Abstract: A multi-rate, burst-mode, photon-counting receiver can communicate at data rates up to 10.416 Mb/s over a 30-foot water channel. With added attenuation, the maximum link loss is 97.1 dB at ?=517 nm. In clear ocean water, this equates to link distances up to 148 meters. For ?=470 nm, the achievable link distance in clear ocean water is 450 meters. The receiver incorporates soft-decision forward error correction (FEC) that supports multiple code rates to achieve error-free performance. A burst-mode receiver architecture provides robust performance with respect to unpredictable channel obstructions. The receiver can detect the data rate on-the-fly and adapts to changing levels of signal and background light. The receiver updates its phase alignment and channel estimates every frame, allowing for rapid changes in water quality as well as motion between transmitter and receiver.

Abstract: A system and method for clock recovery from an input data stream recovers the clock signal in a manner that preserves the signal strength of the input signal. The measure of signal strength, referred to herein as the “signal strength indicator” is in turn used to normalize the output of a phase detector in a phaselocked loop (PLL), and the normalized signal is used as an input to the PLL oscillator to recover the clock signal from the input data signal. In this manner, the phaselocked loop is used to perform narrow band filtering, while baseband amplifiers are used to compensate for reference signal power variations. In one aspect, the present invention is directed to a clock recovery system for recovering a clock signal from an input data signal. The system comprises a primary phase detector for receiving an input data signal, and for combining the input data signal with a feedback signal to generate a phase difference signal.

Abstract: A method for generating a polarization-multiplexed optical clock signal for an optical communication system is described. The method includes splitting a polarized input optical clock signal having a clock rate into a first and a second polarized optical signal. The first polarized optical signal includes a first polarization state and the second polarized optical signal includes a second polarization state. The first polarized optical signal is delayed relative to the second polarized optical signal. The first and the second polarized optical signals are combined to generate the polarization-multiplexed optical clock signal for the optical communication system.

Abstract: A method for modulating a polarization-multiplexed optical clock signal for an optical communication system is described. The method includes splitting a linearly polarized input optical clock signal having a clock rate into a first and a second linearly polarized optical signal. The first linearly polarized optical signal comprises a first polarization state and the second linearly polarized optical signal comprises a second polarization state. The first linearly polarized optical signal is delayed relative to the second linearly polarized optical signal. The first and the second linearly polarized optical signals are combined to generate the polarization-multiplexed optical clock signal for the optical communication system. The polarization-multiplexed optical clock signal is then modulated with a polarization-insensitive optical modulator to encode data on the polarization-multiplexed optical clock signal.

Abstract: A system and method for clock recovery from an input data stream recovers the clock signal in a manner that preserves the signal strength of the input signal. The measure of signal strength, referred to herein as the “signal strength indicator” is in turn used to normalize the output of a phase detector in a phaselocked loop (PLL), and the normalized signal is used as an input to the PLL oscillator to recover the clock signal from the input data signal. In this manner, the phaselocked loop is used to perform narrow band filtering, while baseband amplifiers are used to compensate for reference signal power variations. In one aspect, the present invention is directed to a clock recovery system for recovering a clock signal from an input data signal. The system comprises a primary phase detector for receiving an input data signal, and for combining the input data signal with a feedback signal to generate a phase difference signal.

Abstract: A bit interleaved polarization multiplexer is described that includes a first and a second modulator. The first and the second modulator modulate a first and a second electrical modulation signal, respectively, onto an optical signal and generate a modulated optical pulse train at a first and a second optical output, respectively. An optical beam combiner combines the modulated optical bit stream generated by the first and the second modulators into a polarization multiplexed optical pulse train. A relative position of each pulse in the polarization multiplexed optical pulse train is determined by an optical path length propagated by the pulse and a relative order of each pulse in the polarization multiplexed optical pulse train is determined by a relative phase of the modulation signal that generated the pulse.