Abstract: An optical waveguide modulator with automatic bias control is disclosed. A dither signal is applied to the modulator bias and its signature detected in light tapped from an output of the modulator using a phase sensitive dither detector such as a lock-in amplifier. The detected signal is processed using pre-recorded information defining the direction of the detected signal change relative to a change in the modulator bias, and the bias is adjusted in the direction determined using the information. An IQ bias of a quadrature modulator is controlled by dithering bias settings of two inner modulators at different dither frequencies, and detecting an oscillation at a sum frequency.

Abstract: An optical IQ modulator with automatic bias control is disclosed. A dither signal is applied to the modulator bias and its signature detected in light tapped from an output of the modulator using a phase sensitive dither detector such as a lock-in amplifier. The detected signal is processed using pre-recorded information defining the direction of the detected signal change relative to a change in the modulator bias, and the bias is adjusted in the direction determined using the information. The IQ phase bias is controlled by dithering I and Q optical signals in quadrature to produce opposite-sign single subband modulation of output light at two different dither frequencies, and detecting an oscillation at a difference frequency using a lock-in detector.

Abstract: An heterodyne apparatus and method for measuring performance parameters of a coherent optical receiver at RF frequencies is disclosed. Two coherent lights are launched into signal and LO ports of the receiver with an optical frequency offset f. One of the lights is modulated in amplitude at a test modulation frequency F. COR performance parameters are determined by comparing two frequency components of the COR output. CMRR is determined based on a strength of a direct detection spectral line at the modulation frequency relative to that of spectrally-shifted lines at (F±f). GDV information is obtained by modulating one of the lights at two phase-locked frequencies, such as F and 2F, and comparing phases of two time-domain traces corresponding to frequency components of the COR output signal at the two frequencies.

Abstract: An heterodyne apparatus and method for measuring performance parameters of a coherent optical receiver at RF frequencies is disclosed. Two coherent lights are launched into signal and LO ports of the receiver with an optical frequency offset f. One of the lights is modulated in amplitude at a test modulation frequency F. COR performance parameters are determined by comparing two frequency components of the COR output. CMRR is determined based on a strength of a direct detection spectral line at the modulation frequency relative to that of spectrally-shifted lines at (F±f). GDV information is obtained by modulating one of the lights at two phase-locked frequencies, such as F and 2F, and comparing phases of two time-domain traces corresponding to frequency components of the COR output signal at the two frequencies.

Abstract: An electrical circuit and method for de-modulation and carrier recovery of PSK modulated carrier signals in analog domain are described. A portion of the received PSK-modulated carrier signal is passed through a signal multiplication circuit to obtain a frequency-multiplied carrier that is absent of the PSK modulation, which is then passed through a frequency dividing circuit to obtain a reference carrier at the received carrier frequency. The reference signal is then mixed with the received PSK-modulated carrier signal to obtain a de-modulated baseband signal. The method may be used in heterodyne receivers of optical BPSK and QPSK signals.

Abstract: An optical waveguide modulator with automatic bias control is disclosed. A dither signal is applied to the modulator bias and its signature detected in light tapped from an output of the modulator using a phase sensitive dither detector such as a lock-in amplifier. The detected signal is processed using pre-recorded information defining the direction of the detected signal change relative to a change in the modulator bias, and the bias is adjusted in the direction determined using the information. An IQ bias of a quadrature modulator is controlled by dithering bias settings of two inner modulators at different dither frequencies, and detecting an oscillation at a sum frequency.

Abstract: An optical IQ modulator with automatic bias control is disclosed. A dither signal is applied to the modulator bias and its signature detected in light tapped from an output of the modulator using a phase sensitive dither detector such as a lock-in amplifier. The detected signal is processed using pre-recorded information defining the direction of the detected signal change relative to a change in the modulator bias, and the bias is adjusted in the direction determined using the information. The IQ phase bias is controlled by dithering I and Q optical signals in quadrature to produce opposite-sign single subband modulation of output light at two different dither frequencies, and detecting an oscillation at a difference frequency using a lock-in detector.

Abstract: An electrical circuit and method for de-modulation and carrier recovery of PSK modulated carrier signals in analog domain are described. A portion of the received PSK-modulated carrier signal is passed through a signal multiplication circuit to obtain a frequency-multiplied carrier that is absent of the PSK modulation, which is then passed through a frequency dividing circuit to obtain a reference carrier at the received carrier frequency. The reference signal is then mixed with the received PSK-modulated carrier signal to obtain a de-modulated baseband signal. The method may be used in heterodyne receivers of optical BPSK and QPSK signals.

Abstract: An optical waveguide modulator with automatic bias control is disclosed. A dither signal is applied to the modulator bias and its signature detected in light tapped from an output of the modulator using a phase sensitive dither detector such as a lock-in amplifier. The detected signal is processed using pre-recorded information defining the direction of the detected signal change relative to a change in the modulator bias, and the bias is adjusted in the direction determined using the information. An IQ bias of a quadrature modulator is controlled by dithering bias settings of two inner modulators at different dither frequencies, and detecting an oscillation at a sum frequency.

Abstract: An optical IQ modulator with automatic bias control is disclosed. A dither signal is applied to the modulator bias and its signature detected in light tapped from an output of the modulator using a phase sensitive dither detector such as a lock-in amplifier. The detected signal is processed using pre-recorded information defining the direction of the detected signal change relative to a change in the modulator bias, and the bias is adjusted in the direction determined using the information. The IQ phase bias is controlled by dithering I and Q optical signals in quadrature to produce opposite-sign single subband modulation of output light at two different dither frequencies, and detecting an oscillation at a difference frequency using a lock-in detector.

Abstract: An heterodyne apparatus and method for measuring performance parameters of a coherent optical receiver at RF frequencies is disclosed. Two coherent lights are launched into signal and LO ports of the receiver with an optical frequency offset f. One of the lights is modulated in amplitude at two phase-locked modulation frequencies F1 and F2. COR performance parameters are determined by comparing two frequency components of the COR output. The group delay variation (GDV) information is obtained by comparing phases of two time-domain traces corresponding to frequency components of the COR output signal at the two modulation frequencies shifted by the optical frequency offset f.

Abstract: An heterodyne apparatus and method for measuring performance parameters of a coherent optical receiver at RF frequencies is disclosed. Two coherent lights are launched into signal and LO ports of the receiver with an optical frequency offset f. One of the lights is modulated in amplitude at two phase-locked modulation frequencies F1 and F2. COR performance parameters are determined by comparing two frequency components of the COR output. The group delay variation (GDV) information is obtained by comparing phases of two time-domain traces corresponding to frequency components of the COR output signal at the two modulation frequencies shifted by the optical frequency offset f.

Abstract: An heterodyne apparatus and method for measuring performance parameters of a coherent optical receiver at RF frequencies is disclosed. Two coherent lights are launched into signal and LO ports of the receiver with an optical frequency offset f. One of the lights is modulated in amplitude at a test modulation frequency F. COR performance parameters are determined by comparing two frequency components of the COR output. CMRR is determined based on a strength of a direct detection spectral line at the modulation frequency relative to that of spectrally-shifted lines at (F±f). GDV information is obtained by modulating one of the lights at two phase-locked frequencies, such as F and 2F, and comparing phases of two time-domain traces corresponding to frequency components of the COR output signal at the two frequencies.

Abstract: An electrical circuit and method for de-modulation and carrier recovery of PSK modulated carrier signals in analog domain are described. A portion of the received PSK-modulated carrier signal is passed through a signal multiplication circuit to obtain a frequency-multiplied carrier that is absent of the PSK modulation, which is then passed through a frequency dividing circuit to obtain a reference carrier at the received carrier frequency. The reference signal is then mixed with the received PSK-modulated carrier signal to obtain a de-modulated baseband signal. The method may be used in heterodyne receivers of optical BPSK and QPSK signals.

Abstract: An heterodyne apparatus and method for measuring performance parameters of a coherent optical receiver at RF frequencies is disclosed. Two coherent lights are launched into signal and LO ports of the receiver with an optical frequency offset f. One of the lights is modulated in amplitude at a test modulation frequency F. COR performance parameters are determined by comparing two frequency components of the COR output. CMRR is determined based on a strength of a direct detection spectral line at the modulation frequency relative to that of spectrally-shifted lines at (F±f). GDV information is obtained by modulating one of the lights at two phase-locked frequencies, such as F and 2F, and comparing phases of two time-domain traces corresponding to frequency components of the COR output signal at the two frequencies.

Abstract: An electrical circuit and method for de-modulation and carrier recovery of PSK modulated carrier signals in analog domain are described. A portion of the received PSK-modulated carrier signal is passed through a signal multiplication circuit to obtain a frequency-multiplied carrier that is absent of the PSK modulation, which is then passed through a frequency dividing circuit to obtain a reference carrier at the received carrier frequency. The reference signal is then mixed with the received PSK-modulated carrier signal to obtain a de-modulated baseband signal. The method may be used in heterodyne receivers of optical BPSK and QPSK signals.

Abstract: An heterodyne apparatus and method for measuring performance parameters of a coherent optical receiver at RF frequencies is disclosed. Two coherent lights are launched into signal and LO ports of the receiver with an optical frequency offset f. One of the lights is modulated in amplitude at two phase-locked modulation frequencies F1 and F2. COR performance parameters are determined by comparing two frequency components of the COR output. The group delay variation (GDV) information is obtained by comparing phases of two time-domain traces corresponding to frequency components of the COR output signal at the two modulation frequencies shifted by the optical frequency offset f.

Abstract: An heterodyne apparatus and method for measuring performance parameters of a coherent optical receiver at RF frequencies is disclosed. Two coherent lights are launched into signal and LO ports of the receiver with an optical frequency offset f. One of the lights is modulated in amplitude at two phase-locked modulation frequencies F1 and F2. COR performance parameters are determined by comparing two frequency components of the COR output. The group delay variation (GDV) information is obtained by comparing phases of two time-domain traces corresponding to frequency components of the COR output signal at the two modulation frequencies shifted by the optical frequency offset f.

Abstract: An optical waveguide modulator with automatic bias control is disclosed. A dither signal is applied to the modulator bias and its signature detected in light tapped from an output of the modulator using a phase sensitive dither detector such as a lock-in amplifier. The detected signal is processed using pre-recorded information defining the direction of the detected signal change relative to a change in the modulator bias, and the bias is adjusted in the direction determined using the information. An IQ bias of a quadrature modulator is controlled by dithering bias settings of two inner modulators at different dither frequencies, and detecting an oscillation at a sum frequency.

Abstract: An optical IQ modulator with automatic bias control is disclosed. A dither signal is applied to the modulator bias and its signature detected in light tapped from an output of the modulator using a phase sensitive dither detector such as a lock-in amplifier. The detected signal is processed using pre-recorded information defining the direction of the detected signal change relative to a change in the modulator bias, and the bias is adjusted in the direction determined using the information. The IQ phase bias is controlled by dithering I and Q optical signals in quadrature to produce opposite-sign single subband modulation of output light at two different dither frequencies, and detecting an oscillation at a difference frequency using a lock-in detector.