Abstract: A method and system for ultra-high bit rate fiber-optic communications (e.g., 160 Gb/s) utilize a phase-correlated modulation format where phases of bits in adjacent four-bit groups in transmitted optical pulse trains are altered by ? (or 180°).

Abstract: A method and apparatus for dispersion management in hybrid data rate long haul mesh networks are provided. The apparatus comprises a dispersion compensator for fully compensating the residual dispersion of a fiber link in the mesh network. A de-interleaver is coupled to the dispersion compensator for de-interleaving odd and even channels of wavelength division multiplexed (WDM) signals transmitted across the fiber link. A delay device is coupled to the de-interleaver for introducing a delay to the odd channels or the even channels of the WDM signals to decorrelate the odd and even channels and substantially reduce inter-channel cross-phase modulation.

Abstract: A system and method for multi-channel PMD/PDL/PDG mitigation, the system including polarization scramblers adapted to vary the state of polarization of an optical signal propagated through the system to effectively vary the polarization mode dispersion experienced by the signal during each burst-error-correcting-period of the forward error correction used in the system.

Abstract: Simultaneous tolerance of system nonlinearities and chromatic dispersion in an optical transmission system using return-to-zero (RZ) duobinary signaling is achieved by filtering the received signal in the optical domain with a bandpass filter having a bandwidth B substantially equal to the bit-rate of the RZ-duobinary data signal. The use of an optical bandpass filter in a receiver for RZ-duobinary signals maintains the expected tolerance of system nonlinearities and simultaneously increases significantly the chromatic dispersion tolerance of the signals.

Abstract: Methods and apparatus are provided for transmitting alternate-polarization phase-shift-keyed data. The output of a laser is modulated to optically encode electronic data using phase shift keying (PSK) to generate an optical signal. An alternate polarization PSK (APol-PSK) signal is generated by alternating the polarization of the optical signal using a modulator such that successive optical bits have substantially orthogonal polarizations.

Abstract: An optical receiver adapted to apply multiple-sampling processing to an optical duobinary signal received over a transmission link in an optical communication system. In one embodiment, the receiver has an optical-to-electrical signal converter coupled to a decoder adapted to process an electrical signal generated by the converter to generate a bit sequence corresponding to the optical signal. To generate a bit value, the decoder first obtains two or more bit estimate values by sampling the electrical signal within a corresponding signaling interval two or more times. The decoder then applies a logical function to the bit estimate values, which produces the corresponding bit value for the bit sequence. Advantageously, embodiments of the present invention improve overall back-to-back (i.e., source-to-destination) system performance, e.g., by reducing the number of decoding errors associated with timing jitter and/or spontaneous beat noise in the received optical signal.

Abstract: An optical receiver adapted to process an optical duobinary signal received over a transmission link in an optical communication system. In one embodiment, the receiver has an optical-to-electrical signal converter coupled to a decoder. The decoder processes an electrical signal generated by the converter to generate a bit sequence corresponding to the optical signal. To generate a bit value, the decoder integrates the electrical signal using a sampling window and compares the integration result with a decision threshold value. In one configuration, the width of the sampling window and the decision threshold value are selected based on the eye diagram and noise distribution function, respectively, corresponding to the optical signal. Advantageously, embodiments of the present invention improve overall back-to-back (i.e., source-to-destination) system performance, e.g., by improving dispersion tolerance and/or reducing optical power corresponding to a selected bit error rate value.

Abstract: A system and method for multi-channel PMD/PDL/PDG mitigation, the system including polarization scramblers adapted to vary the state of polarization of an optical signal propagated through the system to effectively vary the polarization mode dispersion experienced by the signal during each burst-error-correcting-period of the forward error correction used in the system.

Abstract: Method and apparatus for transmitting a light signal in an optical transmission system is described. In an example, an optical transmission link includes an input port and an output port. The optical transmission link is configured to propagate optical pulses from the input port to the output port. Information is encoded using phase relationships between adjacent ones of the optical pulses. A phase conjugator is disposed between the input port and the output port. The phase conjugator is positioned to reduce phase variance of the optical pulses at the output port.

Abstract: A method for selecting an optimum delay length in a polarization mode dispersion (PMD) compensator configured with a constant-length delay line and deployed in an optical communication system. The optimum delay length depends on the data modulation format, bit rate, and/or signal bandwidth and is preferably selected such that outage probability in the communication system is at a minimum. System performance of a PMD compensator configured with a constant-length delay line having the optimum length approaches that of a PMD compensator configured with a variable-length delay line. The method extends the application range of constant-length delay line PMD compensators while reducing the cost of implementing high-performance PMD compensation.

Abstract: A multi-channel (e.g. WDM) receiver, in which l PMD compensators are time-shared by n (n>1) communication channels, where 1≦l≦n−1. The receiver implements PMD monitoring to identify channels exhibiting relatively high amounts of PMD. Some or all of the identified channels are then subjected, before decoding, to PMD-reduction processing, while the remaining channels are decoded without such processing. Channel allocation for the processing may be changed dynamically depending on the current amounts of PMD exhibited by various channels. Due to efficient utilization of PMD compensators, multi-channel receivers of the invention are capable of performance comparable to that of the corresponding fully compensated (i.e., having a dedicated PMD compensator for each channel) receivers, but at appreciably lower cost.