Abstract: A method includes evaluating an optical signal spectrum for estimated filtering parameters of an optical spectral filtering device for shaping optical signal spectrum, determining a feedback for fine tuning the optical spectral filtering device for nonlinearity tolerance enhancement in the optical transmission system, responsive to received optical signal quality in the optical signal spectrum; and using the feedback to adjust said optical spectral filtering device for predetermined shaping and predetermined fiber nonlinearity tolerance in the optical transmission system.

Abstract: A wavelength division multiplexing system and method featuring a wavelength monitor that is configured to receive a portion of a combined signal of wavelength division multiplexing channels and determine the wavelengths of each channel or the guardband between each channel in the combined signal. The wavelength monitor determines if there is excess laser drift for each channel in the combined signal. If excess laser drift is determined, feedback is sent to the transmitter for the signal with excess laser drift and the signal is adjusted to produce a target wavelength. The wavelength monitor may utilize optical intradyning in order to monitor the wavelengths of each channel in the combined signal.

Abstract: A system for carrier phase recovery, including a receiver for receiving one or more frames of L symbols. A phase estimator performs carrier phase estimation for the received frames of L symbols, and the resulting carrier phase estimates are stored in a non-transitory computer-readable storage medium. One or more rotators de-rotates the received frames of L symbols by one or more of the carrier phase estimates, and a data processor calculates a sum of the outputs of the L de-rotated signals raised to an nth power, and determines a real part of the sum. A minimum determination device determines a minimum of the real part of the sum with respect to the carrier phase estimates, and phase unwrapping and multiplier removal is performed if a minimum has been determined.

Abstract: A wavelength division multiplexing optical transmission apparatus includes a plurality of polarization multiplexing optical modulation means, polarization-maintaining optical multiplexing means, and delay adjustment means. The polarization multiplexing optical modulation means generate a plurality of polarization multiplexed optical modulation signals having different wavelengths. The polarization-maintaining optical multiplexing means multiplexes the wavelengths of the polarization multiplexed optical modulation signals to generate a wavelength multiplexed optical signal (WDM). The delay adjustment means adjusts a delay such that light intensities of polarization multiplexed optical modulation signals having adjacent wavelengths in the wavelength multiplexed optical signal (WDM) vary inversely with respect to each other.

Abstract: The invention is directed to a novel computer implemented method for finding a modulation format that has better receiver sensitivity than modulation formats that are currently being used, with a correlated symbol modulation in which neighboring symbols are coded and decoded together to increase receiver sensitivity.

Abstract: Methods and systems for transmission and reception of ternary phase-shift keyed data that include mapping triplets of binary bits to pairs of ternary symbols, such that three bits of data are encoded across two symbols having three-point constellations; modulating the pairs of ternary symbols onto a carrier; and transmitting the modulated carrier across a transmission medium.

Abstract: A polarization multiplexing optical transmitter of the present invention includes frequency dividing means (21) that performs frequency dividing on a clock signal having a Baud rate frequency, phase modulation means (8) that performs phase modulation on a light signal in accordance with the clock signal having undergone the frequency dividing, branching means (2) that branches the phase-modulated light into two light signals, delay means (10) that delays one branched light signal relative to the other branched light signal to generate light signals having phases inverted relative to each other, and polarization multiplexing means (5) that synthesizes the generated signals lights with orthogonal polarizations to generate a polarization multiplexed signal. Hence, the polarization multiplexing optical transmitter that can further improve the signal quality can be accomplished.

Abstract: Methods, structures and systems for generating different polarization multiplexed signals wherein the drivers of the modulators are generic while a software-controlled manager allows the carrying of any standard 10 G/40 G/100 G data while—at the same time—being adaptively adjustable according to specific link requirements and users' requests in both dispersion-managed and uncompensated links.

Abstract: At a receiver side, to enhance the performance of concatenated LDPC and TCM coding, an iterative decoding between TCM decoder and LDPC decoder enables improvement in the reliability of received LLRs of each symbol after each iteration. A SOVA output of the TCM is used for LDPC decoding, and then the updated LLRs from LDPC decoder are further looped back to the TCM decoder for the next iteration. In such a manner, the decoding performance could be significantly improved after just several iterations.

Abstract: A method implemented in a transmission apparatus used in an optical fiber communications system for a polarization switched differential quaternary phase-shift keying (DQPSK) signal is disclosed. The method comprises splitting data into two or more data streams, inputting said two or more data streams to 1-bit DQPSK precoders to perform 1-bit DQPSK precoding, and multiplexing inphase outputs of the 1-bit DQPSK precoders to generate a first output; and multiplexing quadrature outputs of the 1-bit DQPSK precoders to generate a second output. Other methods, apparatuses, and systems also are disclosed.

Abstract: An inventive method for multi-symbol polarization switching for differential detection optical systems includes modulating a laser source by a DQPSK modulator, driving the DQPSK modulator with a data block configured for generating multi-symbol polarization-switched DQPSK differential-encoded signals, and polarizing the multi-symbol polarization-switched DQPSK signals with a polarizing modulator whose modulation speed is based on how often polarization states vary, wherein the data block provides a bits manipulation to provide the multi-symbol polarization switching thereby enabling differential detection for recovering correct original data by a receiver.

Abstract: A method for optical chirp-free optical polarization modulation includes dividing a data modulated optical signal into a first optical path and a second optical path, using a Mach-Zehnder intensity modulator in the first optical path for imparting a ? phase difference between adjacent symbols of the data modulated optical signal in the first optical path, adjusting a delay and amplitude of symbols of the data modulated optical signal in the second path so that the symbols in the first path and the symbols in the second path are synchronized and have substantially equal power levels, and combining the first and second optical paths so that symbols from the first and second optical paths are in orthogonal polarizations.

Abstract: Methods, structures and systems for generating different polarization multiplexed signals wherein the drivers of the modulators are generic while a software-controlled manager allows the carrying of any standard 10 G/40 G/100 G data while—at the same time—being adaptively adjustable according to specific link requirements and users' requests in both dispersion-managed and uncompensated links.

Abstract: The invention is directed to a novel computer implemented method for finding a modulation format that has better receiver sensitivity than modulation formats that are currently being used, with a correlated symbol modulation in which neighboring symbols are coded and decoded together to increase receiver sensitivity.

Abstract: An inventive method for multi-symbol polarization switching for differential detection optical systems includes modulating a laser source by a DQPSK modulator, driving the DQPSK modulator with a data block configured for generating multi-symbol polarization-switched DQPSK differential-encoded signals, and polarizing the multi-symbol polarization-switched DQPSK signals with a polarizing modulator whose modulation speed is based on how often polarization states vary, wherein the data block provides a bits manipulation to provide the multi-symbol polarization switching thereby enabling differential detection for recovering correct original data by a receiver.

Abstract: An inventive method for coherent interleaved polarization-multiplexing PolMux optical communications with a single IQ modulator includes modulating a light source to generate a 50% return-to-zero RZ signal pulse at a frequency Rs, driving a single IQ modulator with inphase I and quadrature phase Q data at a bit rate of sais Rs to introduce phase modulation on said 50% RZ signal pulse to produce a QPSK pulse signal with all symbols being in a same polarization state without any time overlapping; and polarization modulating said QPSK signal to alternatively convert said QPSK signal into two orthogonal polarizations states enabling an interleaving PolMux signal with a symbol rate of Rs/2.

Abstract: A method for optical chirp-free optical polarization modulation includes dividing a data modulated optical signal into a first optical path and a second optical path, using a Mach-Zehnder intensity modulator in the first optical path for imparting a ? phase difference between adjacent symbols of the data modulated optical signal in the first optical path, adjusting a delay and amplitude of symbols of the data modulated optical signal in the second path so that the symbols in the first path and the symbols in the second path are synchronized and have substantially equal power levels, and combining the first and second optical paths so that symbols from the first and second optical paths are in orthogonal polarizations.

Abstract: A DPSK optical receiver includes a DPSK demodulation circuit, an optical bandpass filter, a first photodetector, and a first control circuit. The DPSK demodulation circuit demodulates a DPSK optical signal and outputs the DPSK demodulated optical signal. The optical bandpass filter extracts a demodulated optical signal near the center wavelength from the DPSK demodulated optical signal output from the DPSK demodulation circuit. The first photodetector detects the optical power level of the DPSK demodulated optical signal extracted by the optical bandpass filter. The first control circuit performs phase control on the DPSK demodulation circuit so as to optimize the DPSK demodulation circuit with respect to the center wavelength of the DPSK optical signal on the basis of the optical power level detected by the first photodetector.

Abstract: A wavelength division multiplexing optical fiber transmission line that reduces signal deterioration caused by dispersion even in a transmission system having a high-speed transmission rate, and is suited to a long-distance transmission. A dispersion management transmission line is connected between optical repeaters. The dispersion management transmission line has 3 to 6 pairs of fiber sections, of which each has a positive dispersion fiber and a negative dispersion fiber, connected in series. Dispersion compensation is made step by step over four (4) times for dispersion and a dispersive slope, which were accumulated by the front-stage positive dispersion fiber, by the next-stage negative dispersion fiber.

Abstract: A DPSK optical receiver includes a DPSK demodulation circuit, an optical bandpass filter, a first photodetector, and a first control circuit. The DPSK demodulation circuit demodulates a DPSK optical signal and outputs the DPSK demodulated optical signal. The optical bandpass filter extracts a demodulated optical signal near the center wavelength from the DPSK demodulated optical signal output from the DPSK demodulation circuit. The first photodetector detects the optical power level of the DPSK demodulated optical signal extracted by the optical bandpass filter. The first control circuit performs phase control on the DPSK demodulation circuit so as to optimize the DPSK demodulation circuit with respect to the center wavelength of the DPSK optical signal on the basis of the optical power level detected by the first photodetector.