Abstract: Techniques for improving gain equalization in C- and L-band (“C+L”) erbium-doped fiber amplifier (EDFAs) are provided. For example, the C- and L-band amplification sections of a C+L EDFA may be separated and configured in a parallel arrangement or a serial arrangement. For both the parallel and serial arrangements, the C- and L-band amplification sections may share a common gain flattening filter (GFF) or each amplification section may include and employ a separate GFF. Moreover, in some examples, an “interstage” L-band GFF may be located before or upstream of the L-band amplification section such that the L-band optical signal is gain-equalized or flattened prior to the L-band amplification section amplifying the L-band.

Abstract: A line monitoring system may include a laser source to launch a plurality of pulsed probe signals; an optical transmission system, comprising a plurality of loopbacks, to receive the plurality of pulsed probe signals, and direct the plurality of pulsed probe signals through the plurality of loopbacks. The system may include a receiver to receive a plurality of return signals, derived from the plurality of pulsed probe signals from the transmission system, and a perturbance detection system, coupled to the receiver, to measure a phase difference between a polarization of a pair of return signals of the plurality of return signals. The pair of return signals may be received from a pair of loopbacks of the plurality of loopbacks, from a first loopback and a second return signal from a second loopback. The perturbance detection system may determine a location of a perturbation, based upon the phase difference.

Abstract: Provided are optical communication signal recovery techniques and a submarine optical communication recovery device may include a number of inputs, a number of outputs and a number of optical switch modules. Each input may be operable to connect to a respective optical fiber of a submarine fiber optic cable, and a number of the optical fibers carry optical signals and at least one optical fiber of the plurality of optical fibers is an unusable optical path that is unable to carry a usable optical signal. Each output may couple to another respective optical fiber, and a number of the outputs may be designated as impaired outputs. Each optical switch module of the number of optical switch modules may be operable to connect an input of the number of inputs coupled to the unusable optical path to an impaired output of the number of the impaired outputs.

Abstract: A monitoring system. The monitoring system may include an optical receiver configured to receive an optical signal, the receiver comprising a plurality of equalizers to partition the optical signal over a plurality of optical channels corresponding to a plurality of optical wavelengths. The monitoring system may also include an analysis component, coupled to the receiver, comprising logic, where the logic is configured to construct a plurality of sensor matrices, corresponding to the plurality of optical channels, based upon the optical signal, after reception at the receiver; determine, using the plurality of sensor matrices, a correlation between at least one pair of sensor matrices corresponding to at least one pair of optical channels of the plurality of optical channels; and determine a location of a perturbation, external to the transmission system, based upon the correlation.

Abstract: Provided are optical communication signal recovery techniques and a submarine optical communication recovery device may include a number of inputs, a number of outputs and a number of optical switch modules. Each input may be operable to connect to a respective optical fiber of a submarine fiber optic cable, and a number of the optical fibers carry optical signals and at least one optical fiber of the plurality of optical fibers is an unusable optical path that is unable to carry a usable optical signal. Each output may couple to another respective optical fiber, and a number of the outputs may be designated as impaired outputs. Each optical switch module of the number of optical switch modules may be operable to connect an input of the number of inputs coupled to the unusable optical path to an impaired output of the number of the impaired outputs.

Abstract: A monitoring system. The monitoring system may include an optical receiver configured to receive an optical signal, the receiver comprising a plurality of equalizers to partition the optical signal over a plurality of optical channels corresponding to a plurality of optical wavelengths. The monitoring system may also include an analysis component, coupled to the receiver, comprising logic, where the logic is configured to construct a plurality of sensor matrices, corresponding to the plurality of optical channels, based upon the optical signal, after reception at the receiver; determine, using the plurality of sensor matrices, a correlation between at least one pair of sensor matrices corresponding to at least one pair of optical channels of the plurality of optical channels; and determine a location of a perturbation, external to the transmission system, based upon the correlation.

Abstract: A monitoring system. The monitoring system may include an optical receiver configured to receive an optical signal, the receiver comprising a plurality of equalizers to partition the optical signal over a plurality of optical channels corresponding to a plurality of optical wavelengths. The monitoring system may also include an analysis component, coupled to the receiver, comprising logic, where the logic is configured to construct a plurality of sensor matrices, corresponding to the plurality of optical channels, based upon the optical signal, after reception at the receiver; determine, using the plurality of sensor matrices, a correlation between at least one pair of sensor matrices corresponding to at least one pair of optical channels of the plurality of optical channels; and determine a location of a perturbation, external to the transmission system, based upon the correlation.

Abstract: Apparatus, systems, and techniques for extending distributed acoustic sensing (DAS) range in undersea optical cables over multiple spans, as well as providing span-specific DAS information, are provided.

Abstract: A line monitoring system may include a laser source to launch a plurality of pulsed probe signals; an optical transmission system, comprising a plurality of loopbacks, to receive the plurality of pulsed probe signals, and direct the plurality of pulsed probe signals through the plurality of loopbacks. The system may include a receiver to receive a plurality of return signals, derived from the plurality of pulsed probe signals from the transmission system, and a perturbance detection system, coupled to the receiver, to measure a phase difference between a polarization of a pair of return signals of the plurality of return signals. The pair of return signals may be received from a pair of loopbacks of the plurality of loopbacks, from a first loopback and a second return signal from a second loopback. The perturbance detection system may determine a location of a perturbation, based upon the phase difference.

Abstract: A line monitoring system may include a laser source to launch a probe signal over a first bandwidth, a polarization maintaining tap to receive and split the probe signal, into a first portion and a second portion, a polarization rotator to receive the first portion and send the first portion to a transmission system, a return tap to receive the second portion and to receive a return signal from the transmission system, wherein the return signal being derived from the first portion, a photodetector coupled to receive an interference signal from the return tap, wherein the interference signal is generated by a mixing the return signal and the second portion, where the photodetector is arranged to output a power signal based upon the interference signal, and a power measurement system to measure the power signal at a given measurement frequency over a second bandwidth, comparable to the first bandwidth.

Abstract: A line monitoring system may include a laser source to launch a probe signal over a first bandwidth, a polarization maintaining tap to receive and split the probe signal, into a first portion and a second portion, a polarization rotator to receive the first portion and send the first portion to a transmission system, a return tap to receive the second portion and to receive a return signal from the transmission system, wherein the return signal being derived from the first portion, a photodetector coupled to receive an interference signal from the return tap, wherein the interference signal is generated by a mixing the return signal and the second portion, where the photodetector is arranged to output a power signal based upon the interference signal, and a power measurement system to measure the power signal at a given measurement frequency over a second bandwidth, comparable to the first bandwidth.

Abstract: Techniques for improving gain equalization in C- and L-band (“C+L”) erbium-doped fiber amplifier (EDFAs) are provided. For example, the C- and L-band amplification sections of a C+L EDFA may be separated and configured in a parallel arrangement or a serial arrangement. For both the parallel and serial arrangements, the C- and L-band amplification sections may share a common gain flattening filter (GFF) or each amplification section may include and employ a separate GFF. Moreover, in some examples, an “interstage” L-band GFF may be located before or upstream of the L-band amplification section such that the L-band optical signal is gain-equalized or flattened prior to the L-band amplification section amplifying the L-band.

Abstract: A submarine optical communication system using one or more power feed converters for power delivery to repeaters. Power feed equipment located one or more a landmasses is coupled to a power conductor of an optical cable for powering repeaters coupled to cable. One or more power feed converter(s) are coupled to the power conductor for converting current from power feed equipment to a constant output current or voltage for powering other repeaters coupled to the cable. Embodiments are robust to shunts of the power conductor.

Abstract: A submarine optical communication system using one or more power feed converters for power delivery to repeaters. Power feed equipment located one or more a landmasses is coupled to a power conductor of an optical cable for powering repeaters coupled to cable. One or more power feed converter(s) are coupled to the power conductor for converting current from power feed equipment to a constant output current or voltage for powering other repeaters coupled to the cable. Embodiments are robust to shunts of the power conductor.

Abstract: Optical amplifier assembly for spatial division multiplexing (SDM) optical communication systems. Each optical amplifier assembly includes a single pump assembly configured for causing amplification of signals traveling on separate fiber paths in different directions. Each fiber path includes a plurality of spatial dimensions. The single pump assembly includes a plurality of pump sources to provide redundancy and the optical amplifier assembly further includes splitters for splitting outputs of the pump sources to amplifiers coupled to the different spatial dimensions. Different modulation formats may be used on the different spatial dimensions with different pump power being provided to each of the modulation formats. Amplifiers with complementary outputs may be coupled to average out gain deviations.

Abstract: An optical communication amplification system may include a number of amplification stages for an optical signal that includes a first optical wavelength band signal portion and a second optical wavelength band signal portion. Each amplification stage may separate the first optical wavelength band signal portion from the second optical wavelength band signal portion. The separated first optical wavelength band signal portion is amplified using one or more first optical wavelength band amplifiers and the separated second optical wavelength band signal portion are amplified using one or more second optical wavelength band amplifiers. The amplified first optical wavelength band signal portion is filtered and a reflected portion of the first optical wavelength band signal portion may be used to provide energy to the one or more second optical wavelength band amplifiers to increase the power or gain of the separated second optical wavelength band signal portion.

Abstract: A system and method involving using a nonlinear reversible code for probabilistic constellation shaping. A nonlinear reversible code encoder receives information bits and applies a nonlinear reversible code to the information bits to provide encoded bits. A mapper maps the encoded bits to successive amplitude and phase-shift keying (APSK) symbols. Each of the APSK symbols has an APSK modulation format with an associated constellation and the mapper maps each of the symbols to an associated constellation location of the constellation in response to one or more associated ones of the encoded bits.

Abstract: Optical amplifier assembly for spatial division multiplexing (SDM) optical communication systems. Each optical amplifier assembly includes a single pump assembly configured for causing amplification of signals traveling on separate fiber paths in different directions. Each fiber path includes a plurality of spatial dimensions. The single pump assembly includes a plurality of pump sources to provide redundancy and the optical amplifier assembly further includes splitters for splitting outputs of the pump sources to amplifiers coupled to the different spatial dimensions. Different modulation formats may be used on the different spatial dimensions with different pump power being provided to each of the modulation formats. Amplifiers with complementary outputs may be coupled to average out gain deviations.

Abstract: A system and method involving a coded modulation scheme using an M-APSK format with a circular constellation. A maximum achievable spectral efficiency for the transmitters may be selected and a spectral efficiency step-size of the maximum achievable spectral efficiency may be specified. The spectral efficiency for any transmitter in the system may be individually selected by reducing its spectral efficiency from the maximum achievable spectral efficiencies by a selected number of steps corresponding to the step size.

Abstract: An optical communication amplification system may include a number of amplification stages for an optical signal that includes a first optical wavelength band signal portion and a second optical wavelength band signal portion. Each amplification stage may separate the first optical wavelength band signal portion from the second optical wavelength band signal portion. The separated first optical wavelength band signal portion is amplified using one or more first optical wavelength band amplifiers and the separated second optical wavelength band signal portion are amplified using one or more second optical wavelength band amplifiers. The amplified first optical wavelength band signal portion is filtered and a reflected portion of the first optical wavelength band signal portion may be used to provide energy to the one or more second optical wavelength band amplifiers to increase the power or gain of the separated second optical wavelength band signal portion.