At+t Corp.

Lucent Technologies Inc.

Alcatel Lucent

At&t Bell Laboratories

American Telephone and Telegraph, Co.

Lgs Innovations LLC

At&t Intellectual Property I, L.p.

Robert William Tkach

Andrew Roman Chraplyvy

Xiang Liu

Evan Lee Goldstein

Lih-Yuan Lin

John Lester Strand

Chandrasekhar Sethumadhavan

Chuan Pu

Fabrizio Forghieri

Peter Johannes Winzer

Nicholas J Frigo

Angela L Chiu

Robert Duncan Doverspike

Thomas L Koch

Thomas Huntington Wood

John L Zyskind

Lih Yuan Lin

Gokhan Sahin

Kenneth L Walker

Patrick P Iannone

Alan H Gnauck

Jonathan A Nagel

Ivan P Kaminow

Julian Stone

James W Sulhoff

Lawrence Warren Stulz

Atul Kumar Srivastava

Yan Sun

Tingye Li

George W Newsome

Ezhan Karasan

Xiaoping Mao

John C Ellson

An example apparatus comprises an optical transmitter which includes a first processor and at least two optical modulators. The first processor is configured to generate a first electronic representation for each of at least two optical signals for carrying payload data modulated according to a one-dimensional (1-D) modulation format, and to induce on respective ones of the first electronic representations an amount of dispersion that depends on a power-weighted accumulated dispersion (AD) of a transmission link through which the at least two optical signals are to be transmitted thereby generating complex-valued electronic representations of pre-dispersion-compensated optical signals. Each of the at least two optical modulators modulate a respective analog version corresponding to a respective one of the complex-valued electronic representations onto a polarization of an optical carrier.

Communication through multiplexed one-dimensional optical signals

An apparatus comprises an optical transmitter that comprises a processor and at least one optical modulator. The processor is configured to generate electronic representations of at least two pre-dispersion-compensated phase-conjugated optical variants carrying a same modulated payload data for transmission. The at least one optical modulator is configured to modulate the electronic representations, wherein an amount of dispersion induced on the pre-dispersion-compensated phase-conjugated optical variants depends on an accumulated dispersion (AD) of a transmission link through which the pre-dispersion-compensated phase-conjugated optical variants are to be transmitted. The amount of dispersion induced on the phase-conjugated optical variants may be approximately &#x2212;AD/2, where AD is the accumulated dispersion of the transmission link. The pre-dispersion-compensated phase-conjugated optical variants are different from one another in one or more dimensions such as the polarization of light, the time of transmission, the spatial localization, the optical carrier wavelength, or the subcarrier frequency during transmission.

Communication through pre-dispersion-compensated phase-conjugated optical variants

An apparatus receives data encoded in a format where information bits for transmission are mapped into symbols each carrying a plurality of bits, some of which are encoded through a frequency-shift keyed (FSK) format and the rest of which are encoded through an additional modulation format on at least one FSK carrier. The receiver detects the signal through a dual-polarization coherent receiver front-end, and recovers polarization components of the signal by decoding a first non-zero portion of a plurality of bits carried by a symbol based on frequency slot position of at least one FSK carrier in the polarization components and a second non-zero portion of the plurality of bits carried by the symbol based on the additional modulation carried by at least one FSK carrier in the polarization components. Pilot-assisted orthogonal frequency-division de-multiplexing (PA-OFDM) may be used for spectrally-efficient signal reception, even in the presence of severe FSK errors.

System, method and apparatus for high-sensitivity optical detection

An apparatus transmits data using a format where information bits intended for transmission are mapped into symbols each carrying a plurality of bits, some of which are encoded through pulse position modulation (PPM) format and the rest of which are encoded through an additional modulation format on each PPM pulse. The additional modulation format for the PPM pulse may be at least one of a polarization-division-multiplexed (PDM) modulation, phase-shift keying (PSK) modulation, polarization shift keying (PolSK) modulation, amplitude modulation (AM), quadrature-amplitude modulation (QAM) modulation, or a combination thereof. In one embodiment, the additional modulation of the PPM pulses is through polarization-division-multiplexed quadrature-phase-shift keying (PDM-QPSK). The unique combined use of PDM-QPSK and PPM produces much higher receiver sensitivity than either PPM or PDM-QPSK alone.

System, method, and apparatus for high-sensitivity optical detection

An apparatus receives data encoded in a format where information bits for transmission are mapped into symbols each carrying a plurality of bits, some being encoded through a pulse position modulation (PPM) format and some being encoded through an additional modulation format on at least one PPM pulse. A receiver detects the signal through a dual-polarization coherent receiver front-end, recovering polarization components of the signal by decoding a first non-zero portion of a plurality of bits carried by a symbol based on slot position of at least one PPM pulse in the polarization components and a second non-zero portion of the plurality of bits carried by the symbol based on the additional modulation carried by at least one PPM pulse in the polarization components. Pilot-assisted single-carrier frequency-division equalization (PA-SC-FDE) may be used for reliable signal reception in the presence of severe PPM errors.

An optical phase conjugator that can be deployed within a long-haul fiber-optic link of an optical WDM system to improve the system's tolerance to intra- and inter-channel nonlinear effects. In one embodiment, the optical phase conjugator has a digital signal processor configured to perform, in the digital electrical domain, a phase-conjugation transformation for various components of a WDM signal so that certain signal distortions imposed on that signal in the front portion of the fiber-optic link are reduced in the back portion of the link. Advantageously, the optical phase conjugator is flexibly configurable to employ an input-to-output carrier-frequency-mapping configuration that is most beneficial under particular operating conditions. mapping configuration that is most beneficial under particular operating conditions.

Digital phase conjugation for fiber-optic links

Frequency-locked optical comb sources are provided that utilize recirculating frequency shifting based on frequency conversion in a modulator, together with a filter. The filter may be a wavelength notch filter and include a plurality of notches. An example apparatus includes a coupler, an I/Q modulator, and a filter. A first input of the coupler receives a first input optical carrier having a first frequency, and a second input of the coupler re receives a set of frequency-shifted carriers from the filter. The input optical carrier may have a plurality of frequencies. The I/Q modulator shifts the frequency of a first output of the coupler. The filter filters modulated output from the I/Q modulator thereby limiting the frequency-shifted carriers to be within an optical bandwidth. A second output of the coupler provides a plurality of frequency-locked carriers containing the first input optical carrier and the set of frequency-shifted carriers.

Apparatus and method for generating frequency-locked optical comb sources

System, apparatus and method of optical communication are provided for performing digital compensation of the self-phase modulation (SPM) effect experienced by a polarization-division multiplexed (PDM) orthogonal frequency-division multiplexed (OFDM) signal in fiber transmission by compensating a complex digital waveform representing one orthogonal polarization component of the optical PDM-OFDM signal based on both digital waveforms representing two orthogonal polarization components of the PDM-OFDM signal. The compensation of the digital waveform may be further based on an anticipated mean total nonlinear phase shift experienced by the signal during fiber transmission due to SPM. The compensation may be divided into pre-compensation at the PDM-OFDM transmitter and post-compensation at the PDM-OFDM receiver. The fiber transmission link preferably includes a pre-dispersion compensation module, distributed inline dispersion compensation modules, and a post-dispersion compensation module arranged in a judiciously chosen manner.

System, method and apparatus for joint self phase modulation compensation for coherent optical polarization-division-multiplexed orthogonal-frequency division-multiplexing systems

Embodiments for optical communication are provided in which subbands of a multi-carrier optical signal are digital coherent detected and then processed to recover data carried by the modulated carriers corresponding to at least one of the subbands. An exemplary optical communication system includes a multi-carrier coherent optical receiver for receiving a multi-carrier optical signal having M modulated carriers that are frequency locked, wherein M is greater than 2. The multi-carrier coherent optical receiver includes a subband digital coherent detector configured to provide output signals in a digital form for N different subbands of the multi-carrier optical signal, where N is an integer greater than 1 and less than M; and a digital signal processor configured to process the digital form of the detected output signals in order to recover the data carried by the modulated carriers corresponding to at least one of the subbands of the multicarrier optical signal.

Digital coherent detection of multi-carrier optical signal

A method includes receiving a restoration indicator associated with a path that includes an optical cross-connect (OXC). The OXC is reconfigured from a standby configuration to a restoration configuration in response to the restoration indicator. An optical signal received in a first direction at a first wavelength is optically regenerated to produce an optical signal in the first direction at a second wavelength. An optical signal received in a second direction at the second wavelength is optically regenerated to produce an optical signal in the second direction at the first wavelength.

Methods of restoration in an ultra-long haul optical network

An optical carrier drop/add transmission system and method for adding a signal to multiplexed input optical signals conveyed by an optical multiplex input line. The multiplexed input optical signals are demultiplexed to provide isolated input optical signals to an optical switch matrix comprising switches in an array of lines and column, the isolated input optical signals being inputted in a direction parallel to a line of switches in the optical switch matrix. The added optical signal is input in a direction parallel to a column in the optical switch matrix. An output line is selected and the switch that is on the column on which the added optical signal is inputted and on the selected output line is switched.

System and method of wavelength add/drop multiplexing having client configurability

Communication is restored in a fiber optic network by placing error detection circuitry at the add/drop ports of the network nodes of the network. If the error detection circuitry detects an error condition for a communication signal traversing a normal communication path within the network, the communication signal is rerouted along a restoration communication path that is node and span disjoint from the first communication path. By requiring a restoration path to be node and span disjoint from the normal communication path, error detection circuitry need only be placed at the end nodes of the normal communication path. By allowing each node in the restoration path to dynamically choose the particular channels that can accommodate a particular communication signal at the time of the restoration, efficient use of available resources is gained. The result is a cost effective network that restores communication in times competitive to that of SONET rings.

Methods and systems for fast restoration in a mesh network of optical cross connects

The present invention provides methods and systems for restoring communication in a fiber optic network by placing error detection circuitry at the add/drop ports of the network nodes of the network. If the error detection circuitry detects an error condition for a communication signal traversing a normal communication path within the network, the communication signal is rerouted along a restoration communication path that is node and span disjoint from the first communication path. By requiring a restoration path to be node and span disjoint from the normal communication path, error detection circuitry need only be placed at the end nodes of the normal communication path. By allowing each node in the restoration path to dynamically choose the particular channels that can accommodate a particular communication signal at the time of the restoration, efficient use of available resources is gained. The result is a cost effective network that restores communication in times competitive to that of SONET rings.

An optical carrier drop/add transmission system and method for adding a signal to multiplexed input optical signals conveyed by an optical multiplex input line. The multiplexed input optical signals are demultiplexed to provide isolated input optical signals to an optical switch matrix comprising switches in an array of lines and columns, the isolated input optical signals being inputted in a direction parallel to a line of switches in the optical switch matrix. The added optical signal is input in a direction parallel to a column in the optical switch matrix. An output line is selected and the switch that is on the column on which the added optical signal is inputted and on the selected output line is switched.

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Little Silver, NJ, United States of America

Robert William Tkach