Abstract: Feed-forward and feedback strategies are used to control local oscillator power and transimpedance amplifier gain in a high-speed coherent optical receiver.

Abstract: I/Q data skew in a QPSK modulator may be detected by sending identical or complementary data streams to I and Q channel PSK modulators, setting the relative carrier phase between I and Q to zero or ?, and monitoring the average QPSK output power, where the data streams sent to the I and Q channels include streams of alternating ones and zeroes.

Abstract: Digital timing error detection systems and techniques are described. The described techniques are independent of polarization and differential-group-delay and are used to perform timing recovery of polarization-multiplexed coherent optical systems.

Abstract: A method for detecting and measuring time skew in high-speed DP-QPSK coherent optical receivers is described.

Abstract: Patterns detected by a low-speed receiver at the output of a high-speed multiplexer are used to determine when multiplexer input lanes are deskewed.

Abstract: An adaptive-equalizer initialization system performs three functions: frequency offset estimation, taps estimation for chromatic dispersion filters, and taps initialization for an adaptive equalizer. The system contains hardware FFT and peak detector units that sense a pure tone that marks the beginning of a known, short data sequence.

Abstract: Systems and techniques for optical communications based on polarization division multiplexing are described.

Abstract: I/Q data skew in a QPSK modulator may be detected by sending identical or complementary data streams to I and Q channel PSK modulators, setting the relative carrier phase between I and Q to zero or ?, and monitoring the average QPSK output power, where the data streams sent to the I and Q channels include pseudorandom streams of ones and zeroes.

Abstract: Apparatus and methods for receiving and processing optical signals carrying symbols that represent data, including an optical receiver having fractional sampling analog-to-digital conversion and interpolation timing recovery synchronization for processing an optical signal.

Abstract: Optical communication apparatus, methods, systems are provided based on balanced-detection phase-shaped binary transmission (BD-PSBT).

Abstract: Systems and techniques for optical communications based on polarization division multiplexing are described.

Abstract: Techniques, devices and systems based on optical receivers with controllable transfer function bandwidth and gain imbalance.

Abstract: Apparatus and techniques for receiving and processing an optical signal. In one implementation, an optical receiver is provided to include a delay line interferometer, an etalon, and a data estimator for estimating the data carried on a differentially modulated optical input signal. The delay line interferometer receives the input signal and issues differentially decoded constructive and destructive signals. The etalon filters the constructive signal with a transmission stopband imposed over the passband of the constructive signal. The bandwidth of the etalon stopband is selected based on the bandwidth of the modulation of the input signal in order to maximize received signal quality. The data estimator uses a difference between signals derived from the filtered constructive signal and the destructive signal for estimating data.

Abstract: Techniques, apparatus and systems to provide adjustable bit rate optical transmission using programmable signal modulation in optical communication systems.

Abstract: An optical receiver apparatus and methods for mitigating intersymbol interference (ISI) in a differentially-encoded modulation transmission system by controlling constructive and destructive transfer functions. The receiver includes a bandwidth control element for controlling transfer function bandwidth, a transfer phase controller for controlling transfer function phase and/or an imbalancer for imbalancing the transfer functions for compensating for intersymbol interference and optimizing the quality of the received optical signal.

Abstract: An optical receiver apparatus and methods for mitigating intersymbol interference (ISI) in a differentially-encoded modulation transmission system by controlling constructive and destructive transfer functions. The receiver includes a bandwidth control element for controlling transfer function bandwidth, a transfer phase controller for controlling transfer function phase and/or an imbalancer for imbalancing the transfer functions for compensating for intersymbol interference and optimizing the quality of the received optical signal.