Abstract: The disclosure is directed to a method and system for generating a pilot tone for an optical signal with an optical telecommunications system. The pilot tone is generated in the digital domain by modulating the data to be transmitted to a destination node within the optical telecommunications network. The modulation of the data introduces occurrence modulation to the optical signal.

Abstract: A method and apparatus is described for estimating a local oscillator frequency offset (LOFO) of a received optical signal in a coherent optical receiver.

Abstract: The disclosure is directed to a method and system for generating a pilot tone for an optical signal with an optical telecommunications system. The pilot tone is generated in the digital domain by modulating the data to be transmitted to a destination node within the optical telecommunications network. The modulation of the data introduces occurrence modulation to the optical signal.

Abstract: A digital signal processing apparatus and method is described for a transmitter of a communication link. The digital signal processing apparatus comprises a pre-compensation filter for boosting power of a signal to be transmitted within two predetermined frequency bands. One of the predetermined frequency bands is centered around a clock tone frequency of fbaud/2, and the other one of the predetermined frequency bands is centered around a clock tone frequency of ?fbaud/2, fbaud being a baud rate of the transmitted signal.

Abstract: An apparatus comprises a front end configured to receive an optical signal, and convert the optical signal into a plurality of digital signals, and a processing unit coupled to the front end and configured to determine a best-match chromatic dispersion (CD) estimate in the optical signal by optimizing a cost function based on signal peaks of the plurality of digital signals.

Abstract: As network traffic grows and more data needs to be transmitted through a network, it is desired to use optical switching systems that allow for switching between a large number of nodes. An optical switching system according to one embodiment disclosed herein allows different nodes to transmit optical signals having the same optical wavelength, in order to accommodate a larger number of nodes. For example, one cluster of nodes may transmit data using optical wavelengths that are the same as optical wavelengths that may also be used by other clusters of nodes. A controller performs scheduling and reconfiguration in the optical switching system, as needed, e.g. in order to mitigate collisions.

Abstract: A method and apparatus is described for estimating a local oscillator frequency offset (LOFO) of a received optical signal in a coherent optical receiver.

Abstract: A digital signal processing method and apparatus is described. The digital processing apparatus comprises a coarse carrier recovery module for performing a coarse carrier compensation of a received modulated signal; and a trellis-based equalization module selectable between a first mode for performing a trellis-based equalization to compensate a residual inter-symbol interference of the received modulated signal and a second mode for performing a trellis-based equalization to compensate a residual phase noise of the received modulated signal.

Abstract: Quasi-reduced state trellis equalization techniques achieve low-latency inter-symbol interference (ISI) equalization by selecting a subset of accumulated path metrics (APMs) for a leading symbol to propagate over a trellis to candidate states of a trailing symbol. This simplifies the computation of APMs for candidate states of the trailing symbol. Thereafter, APMs for candidate states of the trailing symbol are computed based on the subset of APMs for the leading symbol that were propagated over the trellis. Propagating fewer than all APMs for the leading symbol to the trailing symbol reduces the complexity of APM computation at the trailing symbol.

Abstract: An apparatus for performing fractionally spaced adaptive equalization with non-integer sub-symbol sampling has an adaptive equalizer that receives a continuous stream of input data having a non-integer, fractional delay between consecutive samples at a non-integer, sub-symbol rate and outputs a stream of equalized data based on tap weights of taps of the adaptive equalizer that are spaced at an interval corresponding to the non-integer, sub-symbol rate. The tap weights are updated independently of the fractional delay between consecutive samples of the input data using an error signal. An equalizer output alignment component downstream of the adaptive equalizer aligns the stream of equalized data with a corresponding transmitted symbol.

Abstract: An apparatus comprising a receiver configured to receive an optical signal that carries a multi-rate data signal associated with a first transmission data rate and a second transmission data rate. The apparatus further comprises a processor configured to convert the optical signal into a plurality of digital electrical signals, decode a first portion of the digital electrical signals according to a first modulation format associated with the first transmission data rate, detect a rate change signaling block in the digital electrical signals that indicates a rate change from the first transmission data rate to the second transmission data rate associated with a second modulation format, and decode a second portion of the digital electrical signals received after the rate change signaling block according to the second modulation format.

Abstract: An apparatus for performing fractionally spaced adaptive equalization with non-integer sub-symbol sampling has an adaptive equalizer that receives a continuous stream of input data having a non-integer, fractional delay between consecutive samples at a non-integer, sub-symbol rate and outputs a stream of equalized data based on tap weights of taps of the adaptive equalizer that are spaced at an interval corresponding to the non-integer, sub-symbol rate. The tap weights are updated independently of the fractional delay between consecutive samples of the input data using an error signal. An equalizer output alignment component downstream of the adaptive equalizer aligns the stream of equalized data with a corresponding transmitted symbol.

Abstract: Optical network devices and method for optical network communications in discrete multi-tone (DMT) are provided. A serial information signal is converted to groups of bits and loaded to parallel processing branches based on bit rates of the parallel processing branches. Each branch is configured to encode the associated group of data bits on the associated tone. A first bit rate and modulation and power allocation to a first branch of the branches may be different from a second bit rate and modulation and power allocation to a second branch of the branches. To recover the incoming data, the encoded signal may be parallel-processed using branches with different demodulation formats and provide the serial data stream.

Abstract: An optical circuit switching matrix includes a plurality of optical ports, each optical port being optically coupled to a respective one of a plurality of user nodes and an optical coupler having at least one input port optically coupled to the plurality of optical ports, and an output port. The optical circuit switching matrix also includes a wavelength demultiplexer having an input optically coupled to the output port of the optical coupler, and a plurality of output ports, each output port being optically coupled to a respective one of the plurality of optical ports.

Abstract: An optical transceiver using a modulator biased to a non-linear region of the modulator's power transfer function can extend the possible transmission distance of intensity modulated direct detection (IMDD) n-level pulse amplitude modulated (PAM-n) signals. A non-linear look-up-table may compensate for non-linear characteristics of the modulator. An adaptive decision threshold look-up-table may be used to provide adaptive decision levels at the receiver.

Abstract: The present applies to digital wavelength converters that convert, independently of the format in which optical data may be encoded, an input waveform at a first wavelength to an output waveform at a second wavelength. When operating in an environment where an input waveform has a pilot tone associated thereto, the method and system of the present disclosure allows for the removal of the pilot tone from the input waveform, and also allows for the addition of another pilot to the output waveform.

Abstract: Embodiment reduced-state trellis equalization techniques compute accumulated path metrics (APMs) for a subset of candidate states for at least some stages in the trellis based on a neighborhood map of an ML state. This reduces the number of APMs that are computed and stored during trellis equalization. Other embodiments select a subset of candidate states for which APMs are transported to the next stage of the trellis based on the neighborhood map. This eliminates the need to sort the remaining APMs during reduced state trellis equalization. The neighborhood map identifies a subset of the highest probability neighbors for an ML state. The subset of candidate states identified as highest probability neighbors may be saved in a look-up table. The look-up table may be generated offline and/or generated/updated dynamically during run-time operation.

Abstract: A digital signal processing apparatus and method is described for a transmitter of a communication link. The digital signal processing apparatus comprises a pre-compensation filter for boosting power of a signal to be transmitted within two predetermined frequency bands. One of the predetermined frequency bands is centered around a clock tone frequency of fbaud/2, and the other one of the predetermined frequency bands is centered around a clock tone frequency of ?fbaud/2, fbaud being a baud rate of the transmitted signal.

Abstract: Chromatic dispersion is pre-compensated in a direct-detected orthogonal frequency-division multiplexed optical transmitter through digital signal processing methods, to generate signals that can be transmitted over an optical fiber. The dispersion pre-compensation digital signal processing may include multiplying subcarriers by a respective factor. The dispersion pre-compensation digital signal processing may instead include application of a finite impulse response filter to signals. The dispersion pre-compensation digital signal processing may instead include fast Fourier transformations of signals, application of a frequency domain filter to signals generated by the fast Fourier transformations, and inverse fast Fourier transformations of the signals produced by application of the frequency domain filter.

Abstract: An optical transceiver using a modulator biased to a non-linear region of the modulator's power transfer function can extend the possible transmission distance of intensity modulated direct detection (IMDD) n-level pulse amplitude modulated (PAM-n) signals. A non-linear look-up-table may compensate for non-linear characteristics of the modulator. An adaptive decision threshold look-up-table may be used to provide adaptive decision levels at the receiver.