Patent
US 10,218,446Method and Apparatus for Characterizing and Compensating for Optical Impairments in an Optical Transmitter
Suhas P. Bhandare
US
Copyright © 2026 Matter42. All rights reserved.
Patent
Atlas literature
Patent
US 10,218,446Patent drawings and their descriptions. Click a drawing to enlarge it.
FIG. 1. These photodetectors are connected to the DSP, and the output of the photodetector is used to control the RF signals generated by the DACs 942, 944, …
FIG. 2 illustrates an embodiment of a modulator drive amplifier 200 of the present teaching. Those familiar with the state-of-the-art will appreciate that any …
FIG. 3 illustrates an embodiment of a method 300 for characterization and compensation of optical impairments in optical transmitters according to the present …
FIG. 4 illustrates a plot 400 of the simulated P₁-dB compression point determination used to compute Vic voltage of a MZ modulator for one embodiment of the …
FIG. 5 illustrates a plot 500 of the measured RF transfer functions for four MZ modulators embedded into a wavelength tunable InP-based optical transmitter …
FIG. 6B illustrates the transmitter modulator power imbalances as a function of wavelength after compensation using the method and apparatus of the present …
FIG. 7A Description [0031] The electrical modulation inputs of the MZ modulators 104, 106, 108, 110 are each connected to the output of a respective modulator …
FIGS. 8A and 8B illustrates the measured constellation of a 31.785-Gb/s DP-QPSK signal with RF compensation. The optical modulation analyzer data show a XY …
FIG. 9 illustrates a block diagram of an embodiment of an optical transmitter 900 of the present teaching that includes a transmit digital signal processor …
FIG. 10 A illustrates a graph 1000 of the peak-to-average power ratio for pulse amplitude modulation with four levels (PAM₄) as a function of the Nyquist pulse …
Claims define the patent's legal scope. Independent claims stand alone; dependent claims (nested) narrow them. Click a claim to expand its dependents.
A method for characterizing and compensating for optical impairments in an optical transmitter, the method comprising: a) operating an optical transmitter comprising a first parent Mach-Zehnder (MZ) modulator and a second parent MZ modulator, wherein each of the first and second parent MZ modulators comprises a plurality of child MZ modulators; b) biasing each of the plurality of child MZ modulators in the first and second parent MZ modulators at respective initial operating points; c) generating an electro-optic RF transfer function for each of the plurality of child MZ modulators by measuring a plurality of optical output powers of the optical transmitter while sweeping characterizing RF input drive power levels applied to each of the plurality of child MZ modulators; d) determining curve fitting parameters for each of the plurality of electro- optic RF transfer functions; e) determining operating points of each of the plurality of child MZ modulators using the curve fitting parameters; f) determining an I Q power imbalance at a particular operating point for each of the first and the second parent MZ modulators using the curve fitting parameters for each of the plurality of electro-optic RF transfer functions; g) determining initial RF input drive power levels applied to each of the plurality of child MZ modulators that compensate for the determined IQ power imbalance for each of the first and the second parent MZ modulators; h) determining XY power imbalance of the optical transmitter at the determined initial RF input drive power levels using the curve fitting parameters; i) determining operating RF input drive power levels that at least partially compensate for the first and second I Q power imbalances and for the XY power imbalance of the optical transmitter; and j) generating an optical signal comprising a Nyquist-pulse-shape at an output of the optical transmitter.
The method of characterizing and compensating of claim 1 wherein the plurality of child MZ modulators comprise I nP MZ modulators.
The method of characterizing and compensating of claim 1 wherein the optical transmitter operates over a range of wavelengths.
The method of characterizing and compensating of claim 1 wherein the first parent MZ modulator generates a modulated optical beam having a first polarization and the second parent MZ modulator generates a modulated optical beam having a second polarization.
The method of characterizing and compensating of claim 1 wherein the biasing the plurality of child MZ modulators at the initial operating point comprises biasing the plurality of child MZ modulators at a minimum transmission level.
The method of characterizing and compensating of claim 1 wherein the biasing the plurality of child MZ modulators at the initial operating point comprises biasing the plurality of child MZ modulators at a bias that results in an optical output power that is less than -45 d Bm.
The method of characterizing and compensating of claim 1 wherein the biasing the plurality of child MZ modulators at the initial operating point comprises biasing the plurality of child MZ modulators at a quadrature point.
The method of characterizing and compensating of claim 1 wherein the characterizing RF input drive power comprises characterizing RF input drive power over a particular RF frequency that is in a range of 500 MHz to 3 GHz. 10. The method of characterizing and compensating of claim 1 wherein the sweeping characterizing RF input drive power applied to of each of the plurality of child MZ modulators comprises sweeping the characterizing RF input drive power of each of the plurality of child MZ modulators sequentially.
The method of characterizing and compensating of claim 1 wherein the sweeping characterizing RF input drive power comprises sweeping characterizing RF input drive power of each of the plurality of child MZ modulators through a respective V of the child MZ modulators.
The method of characterizing and compensating of claim 1 wherein the sweeping characterizing RF input drive power comprises varying an output power of an external RF signal generator coupled to an RF input of each of the plurality of child MZ modulators in a range of -1 5dBm to +6 d Bm.
The method of characterizing and compensating of claim 1 wherein the particular operating point used to determine the I Q power imbalance is V ic.
The method of characterizing and compensating of claim 1 wherein the particular operating point used to determine the I Q power imbalance is between 10 d B m and 13.5 d Bm.
The method of characterizing and compensating of claim 1 wherein the particular operating point used to determine the I Q power imbalance is between 12 d B m and 15 d Bm.
The method of characterizing and compensating of claim 1 wherein the generating the electro-optic RF transfer function for each of the plurality of child MZ modulators by measuring the plurality of optical output powers of the optical transmitter while sweeping characterizing RF input drive power levels applied to each of the plurality of child MZ modulators comprises reading swept characterizing RF input drive power from an RF peak detector.
The method of characterizing and compensating of claim 1 wherein the determining curve fitting parameters for each of the plurality of electro-optic RF transfer functions comprises performing a linear curve fit.
The method of characterizing and compensating of claim 1 wherein the determining curve fitting parameters for each of the plurality of electro-optic RF transfer functions comprises performing a polynomial curve fit.
The method of characterizing and compensating of claim 1 wherein the determining curve fitting parameters for each of the plurality of electro-optic RF transfer functions comprises performing an inverse cosine curve fit.
The method of characterizing and compensating of claim 1 further comprising determining voltage set points of modulator drive amplifiers that drive the plurality of child MZ modulators using the operating RF drive powers. 22. The method of characterizing and compensating of claim 21 further comprising performing automatic gain control using the voltage set points of the modulator drive amplifiers to compensate power imbalances.
A method of characterizing and compensating for optical impairments in an I nP-based optical transmitter, the method comprising: a) operating an optical transmitter comprising an X-Pol. I Q and a Y-Pol. IQ modulator, wherein each of the X-Pol. I Q and the Y-Pol. I Q modulators comprise a first and second child MZ modulator, over a range of wavelengths; b) biasing each of the first and second child MZ modulators in each of the X- Pol. I Q and the Y-Pol. I Q modulators at respective initial operating points; c) generating an electro-optic RF transfer function for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators by measuring a plurality of optical output powers of the optical transmitter while sweeping a characterizing RF input drive power applied to each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. I Q modulators for at least some wavelengths in the range of wavelengths; d) determining curve fitting parameters for each of the electro-optic RF transfer functions; e) determining an I Q power imbalance for each of the X-Pol. I Q and the Y- Pol. I Q modulators using the curve fitting parameters; f) determining initial RF input drive powers that when applied to each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y- Pol. I Q modulators compensate for each of the X-Pol. I Q and the Y-Pol. I Q modulator's determined I Q power imbalance; g) determining XY power imbalance of the optical transmitter at the determined initial RF input drive powers for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators using the curve fitting parameters; and h) determining operating RF input drive powers for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators that at least partially compensate for the first and second IQ power imbalances and for the XY power imbalance of the optical transmitter over the range of wavelengths. 24. The method of characterizing and compensating of claim 23 wherein the range of wavelengths comprises a range comprising ninety-six wavelengths on a 50-GHz frequency grid.
The method of characterizing and compensating of claim 23 wherein the range of wavelengths comprises a range that falls within a C-band of an erbium-doped fiber amplifier.
The method of characterizing and compensating of claim 23 wherein the generating the electro-optic RF transfer function for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators comprises generating the electro-optic RF transfer function for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. I Q modulators for only a predetermined number of wavelengths.
The method of characterizing and compensating of claim 23 wherein the predetermined number of wavelengths is either twelve or twenty-four.
The method of characterizing and compensating of claim 23 wherein the determining operating RF input drive powers for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. I Q modulators that at least partially compensate for the I Q power imbalances and XY power imbalance of the optical transmitter are determined over the range of wavelengths comprises performing a polynomial fit for wavelengths that are not measured.
The method of characterizing and compensating of claim 23 wherein the biasing the first and second child MZ modulators of the X-Pol. I Q and the Y- Pol. I Q modulators at the initial operating point comprises biasing the first and second child MZ modulators of the X-Pol. I Q and the Y-Pol. IQ modulators at a minimum transmission level.
The method of characterizing and compensating of claim 23 wherein the Claims What is claimed is:
The method of characterizing and compensating of claim 23 wherein the biasing the first and second child MZ modulators of the X-Po l, IQ and the Y -P ol. IQ modulators at the initial operating point comprises biasing the first a n d second child N modulators of the X-Pol, IQ and the Y-Po l. IQ modulators at a q uadrature point. Original
33, The method of characterizing and compensating of claim 23 wherein the sweeping the characterizing RF input drive power of each of the child M Z modulators comprises sweeping the power of each child M Z modulator sequentially. Original
The method of characterizing and compensating of claim 23 wherein the sweeping the characterizing R F input drive power comprises sweeping the characterizing RF input drive power of each child MZ modulator through their respective V, Original
The method of characterizing and compensating of claim 23 wherein the me asuring the plurality of optical output powers of the optical transmitter as a f unc tion of the swept characterizing RE input drive power of each of the child MIZ modulators comprises reading input drive power fro m an RF p eak detector, Original
38, The method of characteri z ing and compensating of claim 23 whe rein the determining curve fitting parameters for each of the electro-op tic RF transfer function of the first and second child M Z modulators of the X -Po l. Original
The method of characterizing and compensating of claim 23 further comprising determining voltage set points of modulator drive amplifiers that drive the first and second child IZ modulators of the X -Po l IQ and the Y-Pol. IQ modulators using the o pe rating RE in p ut drive p owers. Original
37, The method of characterizing and compens a ting of cla im 2 3 wherein the determining curve fitting parameters for each of the el e ctro-optic RF transfer function of the first and second child M Z modulators of the X-Pol. Original
(Origin a l) The method of characterizing and compensati n g of clai m 23 w herein the determining c u rve fitting para m eters for each of t h e electro-optic RE transfer f tn ction of the first and second child M Z modulators of the X-Po l IQ and the Y -PoL IQ modulators comprises per fo rming an inverse cosine curve f it. Original
The m ethod of characterizing and compensating of cl ai m 40 fbrt her comprising performing au to matic gain control u sing the voltage s e t points of the modulator drive amplifiers to compensate power imbalances. Original
An optical transmitter that characterizes and compensates for optical impairments, the optical transmitter comprising: a) a first parent Mach -Z ehnder (MZ) modulator comprising a plurality of child MZ modulators, the first parent MZ modulator generating an X- polarized modulated optical beam; b) a second parent M ach-Ze hn der (MIZ) modulator comprising a plurality of child M Z modulators, the second parent M Z modulator generating an Y- polarized modulated optical beam, the first and second parent M Z modulator configured to form a dual-polarization optical transmitter that generates wavelength tunable modulated optical signals; c) a p lu ralit y of modulator drive amplifiers, each of the plurality of modulator drive amplifiers supplying modulation signals to respective child MZ modulators; d) a tunable l aser source having an output that is optically coupled to an optical input of the dual-polarization optical transmitter; e) an o p tical p hotodetector having an in p ut that is op tically cou p led to an output of the dual-polarization optical transmitter, the optical photodetector detecting R F m odulation initiated by a signal generator and im posed by the chil d MZ modulators onto the wavelength tunable optical signals generated by the first and second parent MZ modulat or configured to fo rm the dual-polarization optical transmitter; and f) a digital signal processor comprising a plurality of digital-to-analog converters each having a plurality of R E outputs that ar e electrically connected to respective R E inputs of the plurality of modulator drive amplifiers that drive the child MZ modulators, the digital sig n al processor b ein g configured to cycle RE modu lation signals so that responses of each child MZ modulator to the R F modulation si g nals can be characterized, the digital s ignal processor having an input that is electrically connected to the optical photodetectors and configured to: i) generate an e lectro-optic R- transfer function for each of the plurality of child MZ modulators; ii) determine c u rve f i tting parameters for each of the plurality of electro-opti c RE transfer f un ctions; iii) determine operating points of each of the plurality of child M Z modulators using the curve fitti ng p arameters; iv) determine an IQ power imbalance at a particular operating point f or each of the first and the s ec ond parent MZ m odulators using the curve fitting parameters for each of the plurality of elcctro -optic R F transfer functions; v) determine initial RE input drive power levels applied to each of the plurality of child MZ modulators that compensate for the determin e d IQ power imbalance for each of the first and the second parent NZ modulators: vi) determine X Y pow er imbalance of the optical transmitter at the determined in it ial R F input drive power levels using the curve fitting parameters; and vii) determine operating R F input drive power leve ls that at least partially compensate for the first and second IQ power imbalances and for the X Y power imbalance of the optical transmitter. Original
43, The optical transmitter of claim 42 wherein the dua l- polarization optical transmitter co m prises a dua l- polarization in-phase (I) and quadra ture (Q) optical modulator a nd the tunable laser source comprises a full C- b and- wavelength thermally-tunable laser source. Original
(Original) T he o p tical transmitter of claim 42 wherein the p lurality of modulator drive amplifiers comprise differential inputs. Original
47. The optical transmitter of claim 42 wherein the du al-polarization optical transmitter generates wavelength tunable modulated optical signals that c ompri s e raised-cosine-shaped pulses with nQAM modulation. Original
The optical transmitter of claim 42 wherein the dual-polariza tion optical trans m itt e r generates wavelength t u nable modulated optical sig nals that comprise s qu are-root-raised-cosine-shaped pulses w ith nQAM m odulation. Original
Layer stacks claimed or described, ordered top of device to substrate.
dual-polarization optical transmitter with parent and child MZ modulators
InP-based dual-polarization IQ optical transmitter (X-Pol. IQ and Y-Pol. IQ)
optical transmitter with digital signal processor for impairment characterization and compensation
Materials described outside the worked examples.
InP
Measurements and analyses referenced in the patent, with their drawing references.
FIG. 2 illustrates an embodiment of a modulator drive amplifier 200 of the present teaching. Those familiar with the state-of-the-art will appreciate that any …
Related documents with shared materials, methods, properties, or citations.
Patent
Atlas literature
Patent
US 10,218,446Patent drawings and their descriptions. Click a drawing to enlarge it.
FIG. 1. These photodetectors are connected to the DSP, and the output of the photodetector is used to control the RF signals generated by the DACs 942, 944, …
FIG. 2 illustrates an embodiment of a modulator drive amplifier 200 of the present teaching. Those familiar with the state-of-the-art will appreciate that any …
FIG. 3 illustrates an embodiment of a method 300 for characterization and compensation of optical impairments in optical transmitters according to the present …
FIG. 4 illustrates a plot 400 of the simulated P₁-dB compression point determination used to compute Vic voltage of a MZ modulator for one embodiment of the …
FIG. 5 illustrates a plot 500 of the measured RF transfer functions for four MZ modulators embedded into a wavelength tunable InP-based optical transmitter …
FIG. 6B illustrates the transmitter modulator power imbalances as a function of wavelength after compensation using the method and apparatus of the present …
FIG. 7A Description [0031] The electrical modulation inputs of the MZ modulators 104, 106, 108, 110 are each connected to the output of a respective modulator …
FIGS. 8A and 8B illustrates the measured constellation of a 31.785-Gb/s DP-QPSK signal with RF compensation. The optical modulation analyzer data show a XY …
FIG. 9 illustrates a block diagram of an embodiment of an optical transmitter 900 of the present teaching that includes a transmit digital signal processor …
FIG. 10 A illustrates a graph 1000 of the peak-to-average power ratio for pulse amplitude modulation with four levels (PAM₄) as a function of the Nyquist pulse …
Claims define the patent's legal scope. Independent claims stand alone; dependent claims (nested) narrow them. Click a claim to expand its dependents.
A method for characterizing and compensating for optical impairments in an optical transmitter, the method comprising: a) operating an optical transmitter comprising a first parent Mach-Zehnder (MZ) modulator and a second parent MZ modulator, wherein each of the first and second parent MZ modulators comprises a plurality of child MZ modulators; b) biasing each of the plurality of child MZ modulators in the first and second parent MZ modulators at respective initial operating points; c) generating an electro-optic RF transfer function for each of the plurality of child MZ modulators by measuring a plurality of optical output powers of the optical transmitter while sweeping characterizing RF input drive power levels applied to each of the plurality of child MZ modulators; d) determining curve fitting parameters for each of the plurality of electro- optic RF transfer functions; e) determining operating points of each of the plurality of child MZ modulators using the curve fitting parameters; f) determining an I Q power imbalance at a particular operating point for each of the first and the second parent MZ modulators using the curve fitting parameters for each of the plurality of electro-optic RF transfer functions; g) determining initial RF input drive power levels applied to each of the plurality of child MZ modulators that compensate for the determined IQ power imbalance for each of the first and the second parent MZ modulators; h) determining XY power imbalance of the optical transmitter at the determined initial RF input drive power levels using the curve fitting parameters; i) determining operating RF input drive power levels that at least partially compensate for the first and second I Q power imbalances and for the XY power imbalance of the optical transmitter; and j) generating an optical signal comprising a Nyquist-pulse-shape at an output of the optical transmitter.
The method of characterizing and compensating of claim 1 wherein the plurality of child MZ modulators comprise I nP MZ modulators.
The method of characterizing and compensating of claim 1 wherein the optical transmitter operates over a range of wavelengths.
The method of characterizing and compensating of claim 1 wherein the first parent MZ modulator generates a modulated optical beam having a first polarization and the second parent MZ modulator generates a modulated optical beam having a second polarization.
The method of characterizing and compensating of claim 1 wherein the biasing the plurality of child MZ modulators at the initial operating point comprises biasing the plurality of child MZ modulators at a minimum transmission level.
The method of characterizing and compensating of claim 1 wherein the biasing the plurality of child MZ modulators at the initial operating point comprises biasing the plurality of child MZ modulators at a bias that results in an optical output power that is less than -45 d Bm.
The method of characterizing and compensating of claim 1 wherein the biasing the plurality of child MZ modulators at the initial operating point comprises biasing the plurality of child MZ modulators at a quadrature point.
The method of characterizing and compensating of claim 1 wherein the characterizing RF input drive power comprises characterizing RF input drive power over a particular RF frequency that is in a range of 500 MHz to 3 GHz. 10. The method of characterizing and compensating of claim 1 wherein the sweeping characterizing RF input drive power applied to of each of the plurality of child MZ modulators comprises sweeping the characterizing RF input drive power of each of the plurality of child MZ modulators sequentially.
The method of characterizing and compensating of claim 1 wherein the sweeping characterizing RF input drive power comprises sweeping characterizing RF input drive power of each of the plurality of child MZ modulators through a respective V of the child MZ modulators.
The method of characterizing and compensating of claim 1 wherein the sweeping characterizing RF input drive power comprises varying an output power of an external RF signal generator coupled to an RF input of each of the plurality of child MZ modulators in a range of -1 5dBm to +6 d Bm.
The method of characterizing and compensating of claim 1 wherein the particular operating point used to determine the I Q power imbalance is V ic.
The method of characterizing and compensating of claim 1 wherein the particular operating point used to determine the I Q power imbalance is between 10 d B m and 13.5 d Bm.
The method of characterizing and compensating of claim 1 wherein the particular operating point used to determine the I Q power imbalance is between 12 d B m and 15 d Bm.
The method of characterizing and compensating of claim 1 wherein the generating the electro-optic RF transfer function for each of the plurality of child MZ modulators by measuring the plurality of optical output powers of the optical transmitter while sweeping characterizing RF input drive power levels applied to each of the plurality of child MZ modulators comprises reading swept characterizing RF input drive power from an RF peak detector.
The method of characterizing and compensating of claim 1 wherein the determining curve fitting parameters for each of the plurality of electro-optic RF transfer functions comprises performing a linear curve fit.
The method of characterizing and compensating of claim 1 wherein the determining curve fitting parameters for each of the plurality of electro-optic RF transfer functions comprises performing a polynomial curve fit.
The method of characterizing and compensating of claim 1 wherein the determining curve fitting parameters for each of the plurality of electro-optic RF transfer functions comprises performing an inverse cosine curve fit.
The method of characterizing and compensating of claim 1 further comprising determining voltage set points of modulator drive amplifiers that drive the plurality of child MZ modulators using the operating RF drive powers. 22. The method of characterizing and compensating of claim 21 further comprising performing automatic gain control using the voltage set points of the modulator drive amplifiers to compensate power imbalances.
A method of characterizing and compensating for optical impairments in an I nP-based optical transmitter, the method comprising: a) operating an optical transmitter comprising an X-Pol. I Q and a Y-Pol. IQ modulator, wherein each of the X-Pol. I Q and the Y-Pol. I Q modulators comprise a first and second child MZ modulator, over a range of wavelengths; b) biasing each of the first and second child MZ modulators in each of the X- Pol. I Q and the Y-Pol. I Q modulators at respective initial operating points; c) generating an electro-optic RF transfer function for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators by measuring a plurality of optical output powers of the optical transmitter while sweeping a characterizing RF input drive power applied to each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. I Q modulators for at least some wavelengths in the range of wavelengths; d) determining curve fitting parameters for each of the electro-optic RF transfer functions; e) determining an I Q power imbalance for each of the X-Pol. I Q and the Y- Pol. I Q modulators using the curve fitting parameters; f) determining initial RF input drive powers that when applied to each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y- Pol. I Q modulators compensate for each of the X-Pol. I Q and the Y-Pol. I Q modulator's determined I Q power imbalance; g) determining XY power imbalance of the optical transmitter at the determined initial RF input drive powers for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators using the curve fitting parameters; and h) determining operating RF input drive powers for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators that at least partially compensate for the first and second IQ power imbalances and for the XY power imbalance of the optical transmitter over the range of wavelengths. 24. The method of characterizing and compensating of claim 23 wherein the range of wavelengths comprises a range comprising ninety-six wavelengths on a 50-GHz frequency grid.
The method of characterizing and compensating of claim 23 wherein the range of wavelengths comprises a range that falls within a C-band of an erbium-doped fiber amplifier.
The method of characterizing and compensating of claim 23 wherein the generating the electro-optic RF transfer function for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators comprises generating the electro-optic RF transfer function for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. I Q modulators for only a predetermined number of wavelengths.
The method of characterizing and compensating of claim 23 wherein the predetermined number of wavelengths is either twelve or twenty-four.
The method of characterizing and compensating of claim 23 wherein the determining operating RF input drive powers for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. I Q modulators that at least partially compensate for the I Q power imbalances and XY power imbalance of the optical transmitter are determined over the range of wavelengths comprises performing a polynomial fit for wavelengths that are not measured.
The method of characterizing and compensating of claim 23 wherein the biasing the first and second child MZ modulators of the X-Pol. I Q and the Y- Pol. I Q modulators at the initial operating point comprises biasing the first and second child MZ modulators of the X-Pol. I Q and the Y-Pol. IQ modulators at a minimum transmission level.
The method of characterizing and compensating of claim 23 wherein the Claims What is claimed is:
The method of characterizing and compensating of claim 23 wherein the biasing the first and second child MZ modulators of the X-Po l, IQ and the Y -P ol. IQ modulators at the initial operating point comprises biasing the first a n d second child N modulators of the X-Pol, IQ and the Y-Po l. IQ modulators at a q uadrature point. Original
33, The method of characterizing and compensating of claim 23 wherein the sweeping the characterizing RF input drive power of each of the child M Z modulators comprises sweeping the power of each child M Z modulator sequentially. Original
The method of characterizing and compensating of claim 23 wherein the sweeping the characterizing R F input drive power comprises sweeping the characterizing RF input drive power of each child MZ modulator through their respective V, Original
The method of characterizing and compensating of claim 23 wherein the me asuring the plurality of optical output powers of the optical transmitter as a f unc tion of the swept characterizing RE input drive power of each of the child MIZ modulators comprises reading input drive power fro m an RF p eak detector, Original
38, The method of characteri z ing and compensating of claim 23 whe rein the determining curve fitting parameters for each of the electro-op tic RF transfer function of the first and second child M Z modulators of the X -Po l. Original
The method of characterizing and compensating of claim 23 further comprising determining voltage set points of modulator drive amplifiers that drive the first and second child IZ modulators of the X -Po l IQ and the Y-Pol. IQ modulators using the o pe rating RE in p ut drive p owers. Original
37, The method of characterizing and compens a ting of cla im 2 3 wherein the determining curve fitting parameters for each of the el e ctro-optic RF transfer function of the first and second child M Z modulators of the X-Pol. Original
(Origin a l) The method of characterizing and compensati n g of clai m 23 w herein the determining c u rve fitting para m eters for each of t h e electro-optic RE transfer f tn ction of the first and second child M Z modulators of the X-Po l IQ and the Y -PoL IQ modulators comprises per fo rming an inverse cosine curve f it. Original
The m ethod of characterizing and compensating of cl ai m 40 fbrt her comprising performing au to matic gain control u sing the voltage s e t points of the modulator drive amplifiers to compensate power imbalances. Original
An optical transmitter that characterizes and compensates for optical impairments, the optical transmitter comprising: a) a first parent Mach -Z ehnder (MZ) modulator comprising a plurality of child MZ modulators, the first parent MZ modulator generating an X- polarized modulated optical beam; b) a second parent M ach-Ze hn der (MIZ) modulator comprising a plurality of child M Z modulators, the second parent M Z modulator generating an Y- polarized modulated optical beam, the first and second parent M Z modulator configured to form a dual-polarization optical transmitter that generates wavelength tunable modulated optical signals; c) a p lu ralit y of modulator drive amplifiers, each of the plurality of modulator drive amplifiers supplying modulation signals to respective child MZ modulators; d) a tunable l aser source having an output that is optically coupled to an optical input of the dual-polarization optical transmitter; e) an o p tical p hotodetector having an in p ut that is op tically cou p led to an output of the dual-polarization optical transmitter, the optical photodetector detecting R F m odulation initiated by a signal generator and im posed by the chil d MZ modulators onto the wavelength tunable optical signals generated by the first and second parent MZ modulat or configured to fo rm the dual-polarization optical transmitter; and f) a digital signal processor comprising a plurality of digital-to-analog converters each having a plurality of R E outputs that ar e electrically connected to respective R E inputs of the plurality of modulator drive amplifiers that drive the child MZ modulators, the digital sig n al processor b ein g configured to cycle RE modu lation signals so that responses of each child MZ modulator to the R F modulation si g nals can be characterized, the digital s ignal processor having an input that is electrically connected to the optical photodetectors and configured to: i) generate an e lectro-optic R- transfer function for each of the plurality of child MZ modulators; ii) determine c u rve f i tting parameters for each of the plurality of electro-opti c RE transfer f un ctions; iii) determine operating points of each of the plurality of child M Z modulators using the curve fitti ng p arameters; iv) determine an IQ power imbalance at a particular operating point f or each of the first and the s ec ond parent MZ m odulators using the curve fitting parameters for each of the plurality of elcctro -optic R F transfer functions; v) determine initial RE input drive power levels applied to each of the plurality of child MZ modulators that compensate for the determin e d IQ power imbalance for each of the first and the second parent NZ modulators: vi) determine X Y pow er imbalance of the optical transmitter at the determined in it ial R F input drive power levels using the curve fitting parameters; and vii) determine operating R F input drive power leve ls that at least partially compensate for the first and second IQ power imbalances and for the X Y power imbalance of the optical transmitter. Original
43, The optical transmitter of claim 42 wherein the dua l- polarization optical transmitter co m prises a dua l- polarization in-phase (I) and quadra ture (Q) optical modulator a nd the tunable laser source comprises a full C- b and- wavelength thermally-tunable laser source. Original
(Original) T he o p tical transmitter of claim 42 wherein the p lurality of modulator drive amplifiers comprise differential inputs. Original
47. The optical transmitter of claim 42 wherein the du al-polarization optical transmitter generates wavelength tunable modulated optical signals that c ompri s e raised-cosine-shaped pulses with nQAM modulation. Original
The optical transmitter of claim 42 wherein the dual-polariza tion optical trans m itt e r generates wavelength t u nable modulated optical sig nals that comprise s qu are-root-raised-cosine-shaped pulses w ith nQAM m odulation. Original
Layer stacks claimed or described, ordered top of device to substrate.
dual-polarization optical transmitter with parent and child MZ modulators
InP-based dual-polarization IQ optical transmitter (X-Pol. IQ and Y-Pol. IQ)
optical transmitter with digital signal processor for impairment characterization and compensation
Materials described outside the worked examples.
InP
Measurements and analyses referenced in the patent, with their drawing references.
FIG. 2 illustrates an embodiment of a modulator drive amplifier 200 of the present teaching. Those familiar with the state-of-the-art will appreciate that any …
Related documents with shared materials, methods, properties, or citations.
Patent
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US 10,218,446Patent drawings and their descriptions. Click a drawing to enlarge it.
FIG. 1. These photodetectors are connected to the DSP, and the output of the photodetector is used to control the RF signals generated by the DACs 942, 944, …
FIG. 2 illustrates an embodiment of a modulator drive amplifier 200 of the present teaching. Those familiar with the state-of-the-art will appreciate that any …
FIG. 3 illustrates an embodiment of a method 300 for characterization and compensation of optical impairments in optical transmitters according to the present …
FIG. 4 illustrates a plot 400 of the simulated P₁-dB compression point determination used to compute Vic voltage of a MZ modulator for one embodiment of the …
FIG. 5 illustrates a plot 500 of the measured RF transfer functions for four MZ modulators embedded into a wavelength tunable InP-based optical transmitter …
FIG. 6B illustrates the transmitter modulator power imbalances as a function of wavelength after compensation using the method and apparatus of the present …
FIG. 7A Description [0031] The electrical modulation inputs of the MZ modulators 104, 106, 108, 110 are each connected to the output of a respective modulator …
FIGS. 8A and 8B illustrates the measured constellation of a 31.785-Gb/s DP-QPSK signal with RF compensation. The optical modulation analyzer data show a XY …
FIG. 9 illustrates a block diagram of an embodiment of an optical transmitter 900 of the present teaching that includes a transmit digital signal processor …
FIG. 10 A illustrates a graph 1000 of the peak-to-average power ratio for pulse amplitude modulation with four levels (PAM₄) as a function of the Nyquist pulse …
Claims define the patent's legal scope. Independent claims stand alone; dependent claims (nested) narrow them. Click a claim to expand its dependents.
A method for characterizing and compensating for optical impairments in an optical transmitter, the method comprising: a) operating an optical transmitter comprising a first parent Mach-Zehnder (MZ) modulator and a second parent MZ modulator, wherein each of the first and second parent MZ modulators comprises a plurality of child MZ modulators; b) biasing each of the plurality of child MZ modulators in the first and second parent MZ modulators at respective initial operating points; c) generating an electro-optic RF transfer function for each of the plurality of child MZ modulators by measuring a plurality of optical output powers of the optical transmitter while sweeping characterizing RF input drive power levels applied to each of the plurality of child MZ modulators; d) determining curve fitting parameters for each of the plurality of electro- optic RF transfer functions; e) determining operating points of each of the plurality of child MZ modulators using the curve fitting parameters; f) determining an I Q power imbalance at a particular operating point for each of the first and the second parent MZ modulators using the curve fitting parameters for each of the plurality of electro-optic RF transfer functions; g) determining initial RF input drive power levels applied to each of the plurality of child MZ modulators that compensate for the determined IQ power imbalance for each of the first and the second parent MZ modulators; h) determining XY power imbalance of the optical transmitter at the determined initial RF input drive power levels using the curve fitting parameters; i) determining operating RF input drive power levels that at least partially compensate for the first and second I Q power imbalances and for the XY power imbalance of the optical transmitter; and j) generating an optical signal comprising a Nyquist-pulse-shape at an output of the optical transmitter.
The method of characterizing and compensating of claim 1 wherein the plurality of child MZ modulators comprise I nP MZ modulators.
The method of characterizing and compensating of claim 1 wherein the optical transmitter operates over a range of wavelengths.
The method of characterizing and compensating of claim 1 wherein the first parent MZ modulator generates a modulated optical beam having a first polarization and the second parent MZ modulator generates a modulated optical beam having a second polarization.
The method of characterizing and compensating of claim 1 wherein the biasing the plurality of child MZ modulators at the initial operating point comprises biasing the plurality of child MZ modulators at a minimum transmission level.
The method of characterizing and compensating of claim 1 wherein the biasing the plurality of child MZ modulators at the initial operating point comprises biasing the plurality of child MZ modulators at a bias that results in an optical output power that is less than -45 d Bm.
The method of characterizing and compensating of claim 1 wherein the biasing the plurality of child MZ modulators at the initial operating point comprises biasing the plurality of child MZ modulators at a quadrature point.
The method of characterizing and compensating of claim 1 wherein the characterizing RF input drive power comprises characterizing RF input drive power over a particular RF frequency that is in a range of 500 MHz to 3 GHz. 10. The method of characterizing and compensating of claim 1 wherein the sweeping characterizing RF input drive power applied to of each of the plurality of child MZ modulators comprises sweeping the characterizing RF input drive power of each of the plurality of child MZ modulators sequentially.
The method of characterizing and compensating of claim 1 wherein the sweeping characterizing RF input drive power comprises sweeping characterizing RF input drive power of each of the plurality of child MZ modulators through a respective V of the child MZ modulators.
The method of characterizing and compensating of claim 1 wherein the sweeping characterizing RF input drive power comprises varying an output power of an external RF signal generator coupled to an RF input of each of the plurality of child MZ modulators in a range of -1 5dBm to +6 d Bm.
The method of characterizing and compensating of claim 1 wherein the particular operating point used to determine the I Q power imbalance is V ic.
The method of characterizing and compensating of claim 1 wherein the particular operating point used to determine the I Q power imbalance is between 10 d B m and 13.5 d Bm.
The method of characterizing and compensating of claim 1 wherein the particular operating point used to determine the I Q power imbalance is between 12 d B m and 15 d Bm.
The method of characterizing and compensating of claim 1 wherein the generating the electro-optic RF transfer function for each of the plurality of child MZ modulators by measuring the plurality of optical output powers of the optical transmitter while sweeping characterizing RF input drive power levels applied to each of the plurality of child MZ modulators comprises reading swept characterizing RF input drive power from an RF peak detector.
The method of characterizing and compensating of claim 1 wherein the determining curve fitting parameters for each of the plurality of electro-optic RF transfer functions comprises performing a linear curve fit.
The method of characterizing and compensating of claim 1 wherein the determining curve fitting parameters for each of the plurality of electro-optic RF transfer functions comprises performing a polynomial curve fit.
The method of characterizing and compensating of claim 1 wherein the determining curve fitting parameters for each of the plurality of electro-optic RF transfer functions comprises performing an inverse cosine curve fit.
The method of characterizing and compensating of claim 1 further comprising determining voltage set points of modulator drive amplifiers that drive the plurality of child MZ modulators using the operating RF drive powers. 22. The method of characterizing and compensating of claim 21 further comprising performing automatic gain control using the voltage set points of the modulator drive amplifiers to compensate power imbalances.
A method of characterizing and compensating for optical impairments in an I nP-based optical transmitter, the method comprising: a) operating an optical transmitter comprising an X-Pol. I Q and a Y-Pol. IQ modulator, wherein each of the X-Pol. I Q and the Y-Pol. I Q modulators comprise a first and second child MZ modulator, over a range of wavelengths; b) biasing each of the first and second child MZ modulators in each of the X- Pol. I Q and the Y-Pol. I Q modulators at respective initial operating points; c) generating an electro-optic RF transfer function for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators by measuring a plurality of optical output powers of the optical transmitter while sweeping a characterizing RF input drive power applied to each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. I Q modulators for at least some wavelengths in the range of wavelengths; d) determining curve fitting parameters for each of the electro-optic RF transfer functions; e) determining an I Q power imbalance for each of the X-Pol. I Q and the Y- Pol. I Q modulators using the curve fitting parameters; f) determining initial RF input drive powers that when applied to each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y- Pol. I Q modulators compensate for each of the X-Pol. I Q and the Y-Pol. I Q modulator's determined I Q power imbalance; g) determining XY power imbalance of the optical transmitter at the determined initial RF input drive powers for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators using the curve fitting parameters; and h) determining operating RF input drive powers for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators that at least partially compensate for the first and second IQ power imbalances and for the XY power imbalance of the optical transmitter over the range of wavelengths. 24. The method of characterizing and compensating of claim 23 wherein the range of wavelengths comprises a range comprising ninety-six wavelengths on a 50-GHz frequency grid.
The method of characterizing and compensating of claim 23 wherein the range of wavelengths comprises a range that falls within a C-band of an erbium-doped fiber amplifier.
The method of characterizing and compensating of claim 23 wherein the generating the electro-optic RF transfer function for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators comprises generating the electro-optic RF transfer function for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. I Q modulators for only a predetermined number of wavelengths.
The method of characterizing and compensating of claim 23 wherein the predetermined number of wavelengths is either twelve or twenty-four.
The method of characterizing and compensating of claim 23 wherein the determining operating RF input drive powers for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. I Q modulators that at least partially compensate for the I Q power imbalances and XY power imbalance of the optical transmitter are determined over the range of wavelengths comprises performing a polynomial fit for wavelengths that are not measured.
The method of characterizing and compensating of claim 23 wherein the biasing the first and second child MZ modulators of the X-Pol. I Q and the Y- Pol. I Q modulators at the initial operating point comprises biasing the first and second child MZ modulators of the X-Pol. I Q and the Y-Pol. IQ modulators at a minimum transmission level.
The method of characterizing and compensating of claim 23 wherein the Claims What is claimed is:
The method of characterizing and compensating of claim 23 wherein the biasing the first and second child MZ modulators of the X-Po l, IQ and the Y -P ol. IQ modulators at the initial operating point comprises biasing the first a n d second child N modulators of the X-Pol, IQ and the Y-Po l. IQ modulators at a q uadrature point. Original
33, The method of characterizing and compensating of claim 23 wherein the sweeping the characterizing RF input drive power of each of the child M Z modulators comprises sweeping the power of each child M Z modulator sequentially. Original
The method of characterizing and compensating of claim 23 wherein the sweeping the characterizing R F input drive power comprises sweeping the characterizing RF input drive power of each child MZ modulator through their respective V, Original
The method of characterizing and compensating of claim 23 wherein the me asuring the plurality of optical output powers of the optical transmitter as a f unc tion of the swept characterizing RE input drive power of each of the child MIZ modulators comprises reading input drive power fro m an RF p eak detector, Original
38, The method of characteri z ing and compensating of claim 23 whe rein the determining curve fitting parameters for each of the electro-op tic RF transfer function of the first and second child M Z modulators of the X -Po l. Original
The method of characterizing and compensating of claim 23 further comprising determining voltage set points of modulator drive amplifiers that drive the first and second child IZ modulators of the X -Po l IQ and the Y-Pol. IQ modulators using the o pe rating RE in p ut drive p owers. Original
37, The method of characterizing and compens a ting of cla im 2 3 wherein the determining curve fitting parameters for each of the el e ctro-optic RF transfer function of the first and second child M Z modulators of the X-Pol. Original
(Origin a l) The method of characterizing and compensati n g of clai m 23 w herein the determining c u rve fitting para m eters for each of t h e electro-optic RE transfer f tn ction of the first and second child M Z modulators of the X-Po l IQ and the Y -PoL IQ modulators comprises per fo rming an inverse cosine curve f it. Original
The m ethod of characterizing and compensating of cl ai m 40 fbrt her comprising performing au to matic gain control u sing the voltage s e t points of the modulator drive amplifiers to compensate power imbalances. Original
An optical transmitter that characterizes and compensates for optical impairments, the optical transmitter comprising: a) a first parent Mach -Z ehnder (MZ) modulator comprising a plurality of child MZ modulators, the first parent MZ modulator generating an X- polarized modulated optical beam; b) a second parent M ach-Ze hn der (MIZ) modulator comprising a plurality of child M Z modulators, the second parent M Z modulator generating an Y- polarized modulated optical beam, the first and second parent M Z modulator configured to form a dual-polarization optical transmitter that generates wavelength tunable modulated optical signals; c) a p lu ralit y of modulator drive amplifiers, each of the plurality of modulator drive amplifiers supplying modulation signals to respective child MZ modulators; d) a tunable l aser source having an output that is optically coupled to an optical input of the dual-polarization optical transmitter; e) an o p tical p hotodetector having an in p ut that is op tically cou p led to an output of the dual-polarization optical transmitter, the optical photodetector detecting R F m odulation initiated by a signal generator and im posed by the chil d MZ modulators onto the wavelength tunable optical signals generated by the first and second parent MZ modulat or configured to fo rm the dual-polarization optical transmitter; and f) a digital signal processor comprising a plurality of digital-to-analog converters each having a plurality of R E outputs that ar e electrically connected to respective R E inputs of the plurality of modulator drive amplifiers that drive the child MZ modulators, the digital sig n al processor b ein g configured to cycle RE modu lation signals so that responses of each child MZ modulator to the R F modulation si g nals can be characterized, the digital s ignal processor having an input that is electrically connected to the optical photodetectors and configured to: i) generate an e lectro-optic R- transfer function for each of the plurality of child MZ modulators; ii) determine c u rve f i tting parameters for each of the plurality of electro-opti c RE transfer f un ctions; iii) determine operating points of each of the plurality of child M Z modulators using the curve fitti ng p arameters; iv) determine an IQ power imbalance at a particular operating point f or each of the first and the s ec ond parent MZ m odulators using the curve fitting parameters for each of the plurality of elcctro -optic R F transfer functions; v) determine initial RE input drive power levels applied to each of the plurality of child MZ modulators that compensate for the determin e d IQ power imbalance for each of the first and the second parent NZ modulators: vi) determine X Y pow er imbalance of the optical transmitter at the determined in it ial R F input drive power levels using the curve fitting parameters; and vii) determine operating R F input drive power leve ls that at least partially compensate for the first and second IQ power imbalances and for the X Y power imbalance of the optical transmitter. Original
43, The optical transmitter of claim 42 wherein the dua l- polarization optical transmitter co m prises a dua l- polarization in-phase (I) and quadra ture (Q) optical modulator a nd the tunable laser source comprises a full C- b and- wavelength thermally-tunable laser source. Original
(Original) T he o p tical transmitter of claim 42 wherein the p lurality of modulator drive amplifiers comprise differential inputs. Original
47. The optical transmitter of claim 42 wherein the du al-polarization optical transmitter generates wavelength tunable modulated optical signals that c ompri s e raised-cosine-shaped pulses with nQAM modulation. Original
The optical transmitter of claim 42 wherein the dual-polariza tion optical trans m itt e r generates wavelength t u nable modulated optical sig nals that comprise s qu are-root-raised-cosine-shaped pulses w ith nQAM m odulation. Original
Layer stacks claimed or described, ordered top of device to substrate.
dual-polarization optical transmitter with parent and child MZ modulators
InP-based dual-polarization IQ optical transmitter (X-Pol. IQ and Y-Pol. IQ)
optical transmitter with digital signal processor for impairment characterization and compensation
Materials described outside the worked examples.
InP
Measurements and analyses referenced in the patent, with their drawing references.
FIG. 2 illustrates an embodiment of a modulator drive amplifier 200 of the present teaching. Those familiar with the state-of-the-art will appreciate that any …
Related documents with shared materials, methods, properties, or citations.
Patent
Atlas literature
Patent
US 10,218,446Patent drawings and their descriptions. Click a drawing to enlarge it.
FIG. 1. These photodetectors are connected to the DSP, and the output of the photodetector is used to control the RF signals generated by the DACs 942, 944, …
FIG. 2 illustrates an embodiment of a modulator drive amplifier 200 of the present teaching. Those familiar with the state-of-the-art will appreciate that any …
FIG. 3 illustrates an embodiment of a method 300 for characterization and compensation of optical impairments in optical transmitters according to the present …
FIG. 4 illustrates a plot 400 of the simulated P₁-dB compression point determination used to compute Vic voltage of a MZ modulator for one embodiment of the …
FIG. 5 illustrates a plot 500 of the measured RF transfer functions for four MZ modulators embedded into a wavelength tunable InP-based optical transmitter …
FIG. 6B illustrates the transmitter modulator power imbalances as a function of wavelength after compensation using the method and apparatus of the present …
FIG. 7A Description [0031] The electrical modulation inputs of the MZ modulators 104, 106, 108, 110 are each connected to the output of a respective modulator …
FIGS. 8A and 8B illustrates the measured constellation of a 31.785-Gb/s DP-QPSK signal with RF compensation. The optical modulation analyzer data show a XY …
FIG. 9 illustrates a block diagram of an embodiment of an optical transmitter 900 of the present teaching that includes a transmit digital signal processor …
FIG. 10 A illustrates a graph 1000 of the peak-to-average power ratio for pulse amplitude modulation with four levels (PAM₄) as a function of the Nyquist pulse …
Claims define the patent's legal scope. Independent claims stand alone; dependent claims (nested) narrow them. Click a claim to expand its dependents.
A method for characterizing and compensating for optical impairments in an optical transmitter, the method comprising: a) operating an optical transmitter comprising a first parent Mach-Zehnder (MZ) modulator and a second parent MZ modulator, wherein each of the first and second parent MZ modulators comprises a plurality of child MZ modulators; b) biasing each of the plurality of child MZ modulators in the first and second parent MZ modulators at respective initial operating points; c) generating an electro-optic RF transfer function for each of the plurality of child MZ modulators by measuring a plurality of optical output powers of the optical transmitter while sweeping characterizing RF input drive power levels applied to each of the plurality of child MZ modulators; d) determining curve fitting parameters for each of the plurality of electro- optic RF transfer functions; e) determining operating points of each of the plurality of child MZ modulators using the curve fitting parameters; f) determining an I Q power imbalance at a particular operating point for each of the first and the second parent MZ modulators using the curve fitting parameters for each of the plurality of electro-optic RF transfer functions; g) determining initial RF input drive power levels applied to each of the plurality of child MZ modulators that compensate for the determined IQ power imbalance for each of the first and the second parent MZ modulators; h) determining XY power imbalance of the optical transmitter at the determined initial RF input drive power levels using the curve fitting parameters; i) determining operating RF input drive power levels that at least partially compensate for the first and second I Q power imbalances and for the XY power imbalance of the optical transmitter; and j) generating an optical signal comprising a Nyquist-pulse-shape at an output of the optical transmitter.
The method of characterizing and compensating of claim 1 wherein the plurality of child MZ modulators comprise I nP MZ modulators.
The method of characterizing and compensating of claim 1 wherein the optical transmitter operates over a range of wavelengths.
The method of characterizing and compensating of claim 1 wherein the first parent MZ modulator generates a modulated optical beam having a first polarization and the second parent MZ modulator generates a modulated optical beam having a second polarization.
The method of characterizing and compensating of claim 1 wherein the biasing the plurality of child MZ modulators at the initial operating point comprises biasing the plurality of child MZ modulators at a minimum transmission level.
The method of characterizing and compensating of claim 1 wherein the biasing the plurality of child MZ modulators at the initial operating point comprises biasing the plurality of child MZ modulators at a bias that results in an optical output power that is less than -45 d Bm.
The method of characterizing and compensating of claim 1 wherein the biasing the plurality of child MZ modulators at the initial operating point comprises biasing the plurality of child MZ modulators at a quadrature point.
The method of characterizing and compensating of claim 1 wherein the characterizing RF input drive power comprises characterizing RF input drive power over a particular RF frequency that is in a range of 500 MHz to 3 GHz. 10. The method of characterizing and compensating of claim 1 wherein the sweeping characterizing RF input drive power applied to of each of the plurality of child MZ modulators comprises sweeping the characterizing RF input drive power of each of the plurality of child MZ modulators sequentially.
The method of characterizing and compensating of claim 1 wherein the sweeping characterizing RF input drive power comprises sweeping characterizing RF input drive power of each of the plurality of child MZ modulators through a respective V of the child MZ modulators.
The method of characterizing and compensating of claim 1 wherein the sweeping characterizing RF input drive power comprises varying an output power of an external RF signal generator coupled to an RF input of each of the plurality of child MZ modulators in a range of -1 5dBm to +6 d Bm.
The method of characterizing and compensating of claim 1 wherein the particular operating point used to determine the I Q power imbalance is V ic.
The method of characterizing and compensating of claim 1 wherein the particular operating point used to determine the I Q power imbalance is between 10 d B m and 13.5 d Bm.
The method of characterizing and compensating of claim 1 wherein the particular operating point used to determine the I Q power imbalance is between 12 d B m and 15 d Bm.
The method of characterizing and compensating of claim 1 wherein the generating the electro-optic RF transfer function for each of the plurality of child MZ modulators by measuring the plurality of optical output powers of the optical transmitter while sweeping characterizing RF input drive power levels applied to each of the plurality of child MZ modulators comprises reading swept characterizing RF input drive power from an RF peak detector.
The method of characterizing and compensating of claim 1 wherein the determining curve fitting parameters for each of the plurality of electro-optic RF transfer functions comprises performing a linear curve fit.
The method of characterizing and compensating of claim 1 wherein the determining curve fitting parameters for each of the plurality of electro-optic RF transfer functions comprises performing a polynomial curve fit.
The method of characterizing and compensating of claim 1 wherein the determining curve fitting parameters for each of the plurality of electro-optic RF transfer functions comprises performing an inverse cosine curve fit.
The method of characterizing and compensating of claim 1 further comprising determining voltage set points of modulator drive amplifiers that drive the plurality of child MZ modulators using the operating RF drive powers. 22. The method of characterizing and compensating of claim 21 further comprising performing automatic gain control using the voltage set points of the modulator drive amplifiers to compensate power imbalances.
A method of characterizing and compensating for optical impairments in an I nP-based optical transmitter, the method comprising: a) operating an optical transmitter comprising an X-Pol. I Q and a Y-Pol. IQ modulator, wherein each of the X-Pol. I Q and the Y-Pol. I Q modulators comprise a first and second child MZ modulator, over a range of wavelengths; b) biasing each of the first and second child MZ modulators in each of the X- Pol. I Q and the Y-Pol. I Q modulators at respective initial operating points; c) generating an electro-optic RF transfer function for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators by measuring a plurality of optical output powers of the optical transmitter while sweeping a characterizing RF input drive power applied to each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. I Q modulators for at least some wavelengths in the range of wavelengths; d) determining curve fitting parameters for each of the electro-optic RF transfer functions; e) determining an I Q power imbalance for each of the X-Pol. I Q and the Y- Pol. I Q modulators using the curve fitting parameters; f) determining initial RF input drive powers that when applied to each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y- Pol. I Q modulators compensate for each of the X-Pol. I Q and the Y-Pol. I Q modulator's determined I Q power imbalance; g) determining XY power imbalance of the optical transmitter at the determined initial RF input drive powers for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators using the curve fitting parameters; and h) determining operating RF input drive powers for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators that at least partially compensate for the first and second IQ power imbalances and for the XY power imbalance of the optical transmitter over the range of wavelengths. 24. The method of characterizing and compensating of claim 23 wherein the range of wavelengths comprises a range comprising ninety-six wavelengths on a 50-GHz frequency grid.
The method of characterizing and compensating of claim 23 wherein the range of wavelengths comprises a range that falls within a C-band of an erbium-doped fiber amplifier.
The method of characterizing and compensating of claim 23 wherein the generating the electro-optic RF transfer function for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. IQ modulators comprises generating the electro-optic RF transfer function for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. I Q modulators for only a predetermined number of wavelengths.
The method of characterizing and compensating of claim 23 wherein the predetermined number of wavelengths is either twelve or twenty-four.
The method of characterizing and compensating of claim 23 wherein the determining operating RF input drive powers for each of the first and second child MZ modulators in each of the X-Pol. I Q and the Y-Pol. I Q modulators that at least partially compensate for the I Q power imbalances and XY power imbalance of the optical transmitter are determined over the range of wavelengths comprises performing a polynomial fit for wavelengths that are not measured.
The method of characterizing and compensating of claim 23 wherein the biasing the first and second child MZ modulators of the X-Pol. I Q and the Y- Pol. I Q modulators at the initial operating point comprises biasing the first and second child MZ modulators of the X-Pol. I Q and the Y-Pol. IQ modulators at a minimum transmission level.
The method of characterizing and compensating of claim 23 wherein the Claims What is claimed is:
The method of characterizing and compensating of claim 23 wherein the biasing the first and second child MZ modulators of the X-Po l, IQ and the Y -P ol. IQ modulators at the initial operating point comprises biasing the first a n d second child N modulators of the X-Pol, IQ and the Y-Po l. IQ modulators at a q uadrature point. Original
33, The method of characterizing and compensating of claim 23 wherein the sweeping the characterizing RF input drive power of each of the child M Z modulators comprises sweeping the power of each child M Z modulator sequentially. Original
The method of characterizing and compensating of claim 23 wherein the sweeping the characterizing R F input drive power comprises sweeping the characterizing RF input drive power of each child MZ modulator through their respective V, Original
The method of characterizing and compensating of claim 23 wherein the me asuring the plurality of optical output powers of the optical transmitter as a f unc tion of the swept characterizing RE input drive power of each of the child MIZ modulators comprises reading input drive power fro m an RF p eak detector, Original
38, The method of characteri z ing and compensating of claim 23 whe rein the determining curve fitting parameters for each of the electro-op tic RF transfer function of the first and second child M Z modulators of the X -Po l. Original
The method of characterizing and compensating of claim 23 further comprising determining voltage set points of modulator drive amplifiers that drive the first and second child IZ modulators of the X -Po l IQ and the Y-Pol. IQ modulators using the o pe rating RE in p ut drive p owers. Original
37, The method of characterizing and compens a ting of cla im 2 3 wherein the determining curve fitting parameters for each of the el e ctro-optic RF transfer function of the first and second child M Z modulators of the X-Pol. Original
(Origin a l) The method of characterizing and compensati n g of clai m 23 w herein the determining c u rve fitting para m eters for each of t h e electro-optic RE transfer f tn ction of the first and second child M Z modulators of the X-Po l IQ and the Y -PoL IQ modulators comprises per fo rming an inverse cosine curve f it. Original
The m ethod of characterizing and compensating of cl ai m 40 fbrt her comprising performing au to matic gain control u sing the voltage s e t points of the modulator drive amplifiers to compensate power imbalances. Original
An optical transmitter that characterizes and compensates for optical impairments, the optical transmitter comprising: a) a first parent Mach -Z ehnder (MZ) modulator comprising a plurality of child MZ modulators, the first parent MZ modulator generating an X- polarized modulated optical beam; b) a second parent M ach-Ze hn der (MIZ) modulator comprising a plurality of child M Z modulators, the second parent M Z modulator generating an Y- polarized modulated optical beam, the first and second parent M Z modulator configured to form a dual-polarization optical transmitter that generates wavelength tunable modulated optical signals; c) a p lu ralit y of modulator drive amplifiers, each of the plurality of modulator drive amplifiers supplying modulation signals to respective child MZ modulators; d) a tunable l aser source having an output that is optically coupled to an optical input of the dual-polarization optical transmitter; e) an o p tical p hotodetector having an in p ut that is op tically cou p led to an output of the dual-polarization optical transmitter, the optical photodetector detecting R F m odulation initiated by a signal generator and im posed by the chil d MZ modulators onto the wavelength tunable optical signals generated by the first and second parent MZ modulat or configured to fo rm the dual-polarization optical transmitter; and f) a digital signal processor comprising a plurality of digital-to-analog converters each having a plurality of R E outputs that ar e electrically connected to respective R E inputs of the plurality of modulator drive amplifiers that drive the child MZ modulators, the digital sig n al processor b ein g configured to cycle RE modu lation signals so that responses of each child MZ modulator to the R F modulation si g nals can be characterized, the digital s ignal processor having an input that is electrically connected to the optical photodetectors and configured to: i) generate an e lectro-optic R- transfer function for each of the plurality of child MZ modulators; ii) determine c u rve f i tting parameters for each of the plurality of electro-opti c RE transfer f un ctions; iii) determine operating points of each of the plurality of child M Z modulators using the curve fitti ng p arameters; iv) determine an IQ power imbalance at a particular operating point f or each of the first and the s ec ond parent MZ m odulators using the curve fitting parameters for each of the plurality of elcctro -optic R F transfer functions; v) determine initial RE input drive power levels applied to each of the plurality of child MZ modulators that compensate for the determin e d IQ power imbalance for each of the first and the second parent NZ modulators: vi) determine X Y pow er imbalance of the optical transmitter at the determined in it ial R F input drive power levels using the curve fitting parameters; and vii) determine operating R F input drive power leve ls that at least partially compensate for the first and second IQ power imbalances and for the X Y power imbalance of the optical transmitter. Original
43, The optical transmitter of claim 42 wherein the dua l- polarization optical transmitter co m prises a dua l- polarization in-phase (I) and quadra ture (Q) optical modulator a nd the tunable laser source comprises a full C- b and- wavelength thermally-tunable laser source. Original
(Original) T he o p tical transmitter of claim 42 wherein the p lurality of modulator drive amplifiers comprise differential inputs. Original
47. The optical transmitter of claim 42 wherein the du al-polarization optical transmitter generates wavelength tunable modulated optical signals that c ompri s e raised-cosine-shaped pulses with nQAM modulation. Original
The optical transmitter of claim 42 wherein the dual-polariza tion optical trans m itt e r generates wavelength t u nable modulated optical sig nals that comprise s qu are-root-raised-cosine-shaped pulses w ith nQAM m odulation. Original
Layer stacks claimed or described, ordered top of device to substrate.
dual-polarization optical transmitter with parent and child MZ modulators
InP-based dual-polarization IQ optical transmitter (X-Pol. IQ and Y-Pol. IQ)
optical transmitter with digital signal processor for impairment characterization and compensation
Materials described outside the worked examples.
InP
Measurements and analyses referenced in the patent, with their drawing references.
FIG. 2 illustrates an embodiment of a modulator drive amplifier 200 of the present teaching. Those familiar with the state-of-the-art will appreciate that any …
Related documents with shared materials, methods, properties, or citations.
FIG. 7A Description [0031] The electrical modulation inputs of the MZ modulators 104, 106, 108, 110 are each connected to the output of a respective modulator …
FIGS. 8A and 8B illustrates the measured constellation of a 31.785-Gb/s DP-QPSK signal with RF compensation. The optical modulation analyzer data show a XY …
FIG. 7A Description [0031] The electrical modulation inputs of the MZ modulators 104, 106, 108, 110 are each connected to the output of a respective modulator …
FIGS. 8A and 8B illustrates the measured constellation of a 31.785-Gb/s DP-QPSK signal with RF compensation. The optical modulation analyzer data show a XY …
FIG. 7A Description [0031] The electrical modulation inputs of the MZ modulators 104, 106, 108, 110 are each connected to the output of a respective modulator …
FIGS. 8A and 8B illustrates the measured constellation of a 31.785-Gb/s DP-QPSK signal with RF compensation. The optical modulation analyzer data show a XY …
FIG. 7A Description [0031] The electrical modulation inputs of the MZ modulators 104, 106, 108, 110 are each connected to the output of a respective modulator …
FIGS. 8A and 8B illustrates the measured constellation of a 31.785-Gb/s DP-QPSK signal with RF compensation. The optical modulation analyzer data show a XY …