Abstract: Aspects of the subject disclosure may include, for example, receiving, at a coherent optical receiver system, Frequency Division Multiplexed (FDM) signals within a spectrum, and equalizing the FDM signals, wherein the equalizing involves creating a plurality of sub-spectra that each corresponds to a respective one of the FDM signals, wherein two sub-spectra of the plurality of sub-spectra have overlapping frequencies, and applying a distinct equalization to each of the plurality of sub-spectra, resulting in distinct equalizations, wherein at least two of the distinct equalizations have substantially independent control. Other embodiments are disclosed.

Abstract: Aspects of the subject disclosure may include, for example, arranging a signal into a wavelength division multiplexing (WDM) spectral slot, wherein the signal has a first spectral width, communicating with a receiver using the signal, determining one or more network characteristics based on the communicating, adjusting a center wavelength of the signal in accordance with the one or more network characteristics, modifying the signal such that the signal has a second spectral width, resulting in a modified signal, wherein the second spectral width is larger than the first spectral width, and causing the modified signal to carry traffic to the receiver. Other embodiments are disclosed.

Abstract: Aspects of the subject disclosure may include, for example, a device including a detector configured to identify a narrow-band absorption occurring within a signal spectrum of an optical signal propagating through a gaseous medium, wherein the optical signal is configured to communicate digital information via an optical communication link including a transmitter, a receiver and an optical transport medium therebetween. The device further includes a mitigation controller configured to control a digital circuit to mitigate at least a portion of a vulnerability of the optical communication link, the vulnerability associated with the narrow-band absorption. Other embodiments are disclosed.

Abstract: Aspects of the subject disclosure may include, for example, obtaining two inputs xI and xQ based on a digital input signal, and causing a modulator to create two substantially orthogonal output dimensions I and Q based on the two inputs xI and xQ, by performing controlled introduction of a correlation between the two inputs xI and xQ for the modulator, and detecting a resulting output power of the modulator to facilitate operation of the modulator. Other embodiments are disclosed.

Abstract: A system that incorporates the subject disclosure may include, for example, receiving, via one or more spatially distinct receivers, a plurality of transmitted optical signals associated with a spatially-diverse optical communication link, forming an optical signal based on a combination of the plurality of transmitted optical signals, converting the optical signal to an electrical signal, processing the electrical signal to produce multi-gigabit digital output data, extracting one or more parameters from the electrical signal, and controlling, based on the one or more parameters, the forming of the optical signal, the converting of the optical signal, the processing of the electrical signal, the extracting of the one or more parameters, or any combinations thereof. Additional embodiments are disclosed.

Abstract: A system that incorporates the subject disclosure may include, for example, receiving optical signals, wherein the optical signals are generated by a transmitter, wherein the transmitter generates multiple optical wavelengths, wherein the transmitter modulates the multiple optical wavelengths from digital input data to create correlated optical signals, and wherein the transmitter transmits the correlated optical signals across a transmission medium having characteristics of a turbulent channel, converting of the optical signals to electrical signals, processing of the electrical signals in a modem to produce output data and additional information, supplying the additional information to a processor, and based on the additional information, the processor generating one or more control signals directed to a phase alignment stage for compensating turbulent effects experienced by the optical signals while propagating through the turbulent channel. Additional embodiments are disclosed.

Abstract: Aspects of the subject disclosure may include, for example, obtaining a signal received at a coherent optical receiver, and equalizing the signal using a filter system, wherein the filter system includes a first filter that provides a first filtering characteristic, a second filter that provides a second filtering characteristic, and a third filter that provides a third filtering characteristic, wherein an adjustment rate of the first filter and an adjustment rate of the second filter are each at least ten times an adjustment rate of the third filter, and wherein the adjustment rate of the first filter is at least ten times the adjustment rate of the second filter. Other embodiments are disclosed.

Abstract: Aspects of the subject disclosure may include, for example, creating a first sequence of optical signals based on a first sequence of electrical signals, the first sequence of electrical signals associated with a plurality of matched filters, directing the first sequence of optical signals to a plurality of objects, receiving a second sequence of optical signals based on a reflection of the first sequence of optical signals on the plurality of objects, converting the second sequence optical signals into a second sequence of electrical signals, processing the second sequence of electrical signals according to the plurality of matched filters to extract information associated with the plurality of objects, adjusting the first sequence of electrical signals to a third sequence of electrical signals, adjusting the plurality of matched filters according to the third sequence of electrical signals, generating from the third sequence of the electrical signals an adjusted sequence of optical signals, and directing th

Abstract: Aspects of the subject disclosure may include, for example, generating a first set of optical signals, demultiplexing the first set of optical signals to generate demultiplexed signals, launching the demultiplexed signals into a medium, receiving from the medium a second set of optical signals, multiplexing at least a portion of the second set of optical signals to generate one or more multiplexed signals, obtaining one or more electrical signals according to one or more measurements of one or more optical fields of the one or more multiplexed signals, and generating one or more point spread functions from the one or more electrical signals. Other embodiments are disclosed.

Abstract: Aspects of the subject disclosure may include, for example, generating one or more first optical signals, launching the first optical signal into a medium, receiving from the medium one or more second optical signals, mixing the one or more second optical signals with one or more third optical signals to generate one or more mixed signals, obtaining one or more electrical signals from the mixed signal, and generating one or more point spread functions from the one or more electrical signals. Other embodiments are disclosed.

Abstract: In an optical communication system, a train of optical pulses is transmitted such that each pulse carries a set of multiplexed channels. In a receiver, the error rate for each channel is monitored and a subset of channels having the most favorable rate is selected to carry a first data stream. The remaining channels carry a second data stream. Error rate performance is determined on the basis of error detecting codes carried by the channels in the first and second data streams.

Abstract: Optical timing detection, for phase comparison of optical signals, or clock recovery is achieved by arranging an interferometer to be responsible to data transitions. A pulse train is fed into both arms of the interferometer. An optical amplifier (20) enables the interference condition to be changed when the data is fed into one arm. The output changed if the data transitions lose synchronisation with the pulse train.

Abstract: A sub-harmonic clock signal is provided in a series of soliton optical pulses that are transmitted at a given line rate in a soliton optical transmission system. The line rate defines time slots of equal duration. Each soliton optical pulse in every N time slots is modulated in a manner to make the pulse distinguishable from pulses in other time slots. The frequency of the sub-harmonic clock signal is equal to the line rate divided by N. This technique of providing a clock signal allows simple recovery of the clock signal using a PIN diode photo detector and a bandpass filter of appropriate bandwidth.

Abstract: An optical transmission system comprises a number of optical terminals connected by optical waveguides such as optical fibers. Nonlinear processes occurring within an optical transmission medium of the waveguide or within the optical terminals is detected by a monitor which outputs monitored data representative of the products of nonlinearity. The data is used to control the power of the optical signal such that power is regulated to avoid the onset of the nonlinear process. The data may also be used to indicate an alarm condition to an operator. A monitor for four wave mixing detection utilizes dither signals applied to respective frequency components of a wavelength division multiplexed signal, products of the four wave mixing process being detected in the monitor by correlation between a sample of a received optical signal and reference data representative of dither induced modulation in the four wave mixing product.

Abstract: In an optical communication system, a train of optical pulses is transmitted such that each pulse carries a set of multiplexed channels. In a receiver, the error rate for each channel is monitored and a subset of channels having the most favorable rate is selected to carry a first data stream. The remaining channels carry a second data stream. Error rate performance is determined on the basis of error detecting codes carried by the channels in the first and second data streams.

Abstract: Optical signals in an optical communication system are transmitted as a train of optical pulses which are multiplexed to provide a large number of channels. Error correction coding is applied to data carried by the channels using both interchannel coding and serial coding of individual channels. When multiplexed by wavelength division multiplexing, a waveguide array is used as a dispersive device having a characteristic of frequency selectivity which is locked by a monitoring and control system to a set of spectral lines from the single pulsed laser which generates the pulses. In the receiver, clock signals are generated by extracting clock signals from the earliest and latest received channel signals and performing interpolation to obtain clock signals for the remaining channels. When multiplexed using a spectral modulation technique, individual channels are represented by distinct sinusoidal modulations in frequency space which are then detected in the receiver by Mach-Zehnder filters.

Abstract: Optical timing detection, for phase comparison of optical signals, or clock recovery is achieved by arranging an interferometer to be responsible to data transitions. A pulse train is fed into both arms of the interferometer. An optical amplifier (20) enables the interference condition to be changed when the data is fed into one arm. The output changed if the data transitions lose synchronization with the pulse train.

Abstract: In an optical transmission system, an optical signal is transmitted to an optical element which is sensitive to changes in the optical power of the signal. Changes in optical power are anticipated and damped by controlling the transmitter output power, or an external damping element. For WDM systems, wavelengths can be added or removed without causing rapid changes in total power which would otherwise disturb the output of downstream optical amplifiers, and cause bit errors.

Abstract: An optical transmission system includes means for measuring optical dispersion in the optical path, and a controllable element such as a dispersion compensator, operable in dependence on the measured value of dispersion. A low frequency dither on the optical signal causes timing jitter which varies according to the dispersion in the optical path. The timing jitter is extracted from a clock signal recovered from the optical signal. This jitter is correlated with the original dither to remove jitter effects caused by other mechanisms. Thus a value for dispersion is derived which can be used for monitoring or control purposes.

Abstract: An interferometer, such as a Mach-Zehnder type is fed with a pulse train. One arm is fed with a data stream, so as to modulate the pulse train according to the data stream. This enables the data stream to be regenerated, or sampled without converting from optical form into electrical form. Thus all optical regeneration, multiplexing, demultiplexing or retiming to remove jitter, can be achieved. An optical amplifier (20) in one arm of the interferometer enables the interference condition of the interferometer to be varied, to cause the pulse train to be modulated by the data.