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: 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.

Abstract: System and method embodiments are provided for improving reception of direct detection optical signals. In an embodiment, a method for optical transmission includes bit loading and power loading, with a digital signal processor (DSP), transmission bits of an orthogonal frequency-division multiplexing (OFDM) signal; calculating, with the DSP, a signal-signal beat interference (SSBI) component of the bit and power loaded OFDM signal by modulating each subcarrier with a symbol; and subtracting, with the DSP, the calculated SSBI component from the bit and power loaded OFDM signal.

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: System and method embodiments are provided for carrier-signal power ratio (CSPR) control in direct detection optical systems. In an embodiment, a method for CSPR control in a direct detection optical system includes receiving an electrical signal in a receiver (RX) digital signal processor (DSP), wherein the electrical signal is obtained from a corresponding optical signal via a direct detection component; estimating, a CSPR for the electrical signal; generating one of a control signal according to the CSPR; and transmitting the control signal to one of an optical filter and a laser, wherein the wavelength control signal controls causes a center wavelength (CW) of one of the optical filter and the laser to be adjusted such that an offset between the CW of the laser and the CW of the optical filter results in a desired CSPR.

Abstract: Provided is an apparatus and method for transmitting and receiving wireless signals. A transmitting apparatus has a signal processor and a transmitter. The signal processor is configured to generate a signal having a middle channel and at least one side channel. The transmitter is configured to wirelessly transmit the signal subject to a spectral mask that has shoulder regions. According to an embodiment of the invention, the signal processor generates the signal such that each side channel is positioned in one of the shoulder regions of the spectral mask. In this manner, bandwidth from the shoulder regions can be utilized by one or more side channels. Also provided is a receiving apparatus having a receiver configured to wirelessly receive the signal, and a signal processor configured to process the signal.

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: Provided is an apparatus and method for transmitting and receiving wireless signals. A transmitting apparatus has a signal processor and a transmitter. The signal processor is configured to generate a signal having a middle channel and at least one side channel. The transmitter is configured to wirelessly transmit the signal subject to a spectral mask that has shoulder regions. According to an embodiment of the invention, the signal processor generates the signal such that each side channel is positioned in one of the shoulder regions of the spectral mask. In this manner, bandwidth from the shoulder regions can be utilized by one or more side channels. Also provided is a receiving apparatus having a receiver configured to wirelessly receive the signal, and a signal processor configured to process the signal.

Abstract: A method and apparatus for performing residual phase noise compensation is described. A coarse carrier compensation of a received modulated signal is performed to obtain a coarse carrier compensated signal and a trellis-based residual carrier recovery is performed to estimate a residual phase noise of the coarse carrier compensated signal. The coarse carrier compensated signal is compensated based on the estimated residual phase noise.

Abstract: A method for wavelength conversion comprising receiving an input optical signal with a first wavelength, converting the input optical signal to a plurality of input analog signals, generating a plurality of digital signals based on the input analog signals, compensating for waveform distortions by at least filtering one or more of the digital signals to generate one or more compensated digital signals, converting the compensated digital signals to output analog signals via digital-to-analog (DA) conversion, generating an output optical signal with a second wavelength different from the first wavelength based on the output analog signals, and transmitting the output optical signal.

Abstract: An apparatus comprising a processing unit configured to encode a data sequence in a plurality of modulation formats to produce a multi-rate data stream, wherein a first of the modulation formats provides a first transmission data rate, and wherein a second of the modulation formats provides a second transmission data rate different from the first transmission data rate, and insert a rate change signaling block into the multi-rate data stream to indicate a rate change from the first transmission data rate to the second transmission data rate, and a frontend coupled to the processing unit and configured to convert the multi-rate data stream into an optical signal, and transmit the converted optical signal towards a remote optical receiver via an optical network.

Abstract: Described are an optical communications system and a method that allow for compensation of chromatic dispersion and polarization mode dispersion imparted to a communications signal propagating through an optical link. The system is based on a cost-effective optical transport architecture that accommodates baud rates exceeding 15 Gbaud and eliminates the need for costly optical dispersion compensators. Compensation for polarization mode dispersion is performed at the receiver using nonlinear processing. Advantageously, direct detection modulation using inexpensive electro-optic system components can be used in place of more costly and complex coherent and differential modulation formats. Digital filtering can be performed at the transmitter and the input signal can be inverted based on the nonlinearity of the transmitter electro-optic components. Consequently, the bandwidth and linearity requirements for the transmitter electro-optic components are relaxed, and cost reductions are realized.

Abstract: The present disclosure provides a method and system for fine estimation of a local oscillator frequency offset of a received signal at a coherent receiver, by evaluating the probability mass function (PMF) of the signal phase of output symbols at different frequencies. At frequencies other than the actual frequency offset, the signal phase is uniformly distributed in [??,?] such that the summation of a function of PMF values where the function is convex or concave between 0 and 1 can be utilized to determine an a frequency offset to be used by the coherent receiver.

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 apparatus comprising a digital signal processor (DSP) configured to code a plurality of data sub-streams using a plurality of modulation formats to generate a plurality of coded data symbols, wherein each modulation format leads to a unique bit rate for coded data symbols associated with a modulation format, transform the coded data symbols into a frequency domain by applying Fourier transform on each coded data symbol, map the frequency-transformed data symbols onto a plurality of subcarrier signals associated with a plurality of frequency tones, wherein at least two of the subcarrier signals correspond to different modulation formats, and generate an electrical signal in a time domain based on the subcarrier signals.

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: A method of optical communication comprising encoding four modulated symbols to generate four encoded symbols in two orthogonal polarizations and transmitting the four encoded symbols in two successive time slots. An optical communication apparatus comprising a processor configured to receive two sequences of digital symbols in a plurality of time slots, wherein the two sequences correspond to two components of two orthogonal polarizations, wherein one digital symbol per polarization is received in each of the plurality of time slots, divide each of the two sequences into a plurality of groups using a modulo operation of time, wherein each group comprises two digital symbols received in two consecutive time slots, and adaptively equalize the four digital symbols of the two consecutive time slots using a 4×4 matrix to generate four modulated symbols, wherein the 4×4 matrix comprises 16 tap-vectors.

Abstract: An apparatus comprises a digital signal processing module configured to receive a data stream and generate a plurality of digital multiple tones, a plurality of digital-to-analog converters coupled to the digital signal processing module, a plurality of drivers coupled to respective digital-to-analog converters, an electro-optic modulator having inputs coupled to the drivers and outputs coupled to a fiber and a multi-wavelength light source coupled to the electro-optic modulator.