A method of dispersion compensation for an optical link includes establishing communication using a first symbol rate over the optical link, determining a dispersion compensation for the optical link based on the communication at the first symbol rate, and establishing communication using a second symbol rate over the optical link using the determined dispersion compensation, wherein the second symbol rate is higher than the first symbol rate.

A signal processing apparatus includes: a coefficient update unit configured to approximate a characteristic of a transmission line of an optical signal by a first tap coefficient vector of which an L0 norm is a predetermined value or less; a zeroing unit configured to generate a second tap coefficient vector by replacing, with 0, a tap coefficient of which an absolute value is less than a threshold among tap coefficients of the first tap coefficient vector; and an adaptive filter configured to perform, based on the second tap coefficient vector, adaptive equalization processing on a digital signal corresponding to an optical signal received via the transmission line.

Systems and methods include causing transmission of one or more shaped Amplified Spontaneous Emission (ASE) signals, from an ASE source (70), on an optical fiber (58, 60); obtaining received spectrum of the one or more shaped ASE signals from an optical receiver (68) connected to the optical fiber (58, 60); and characterizing the optical fiber (58, 60) based in part on one or more of a nonlinear skirt and a center dip depth in the received spectrum of the one or more shaped ASE signals. The one or more shaped ASE signals can be formed by the ASE source (70) communicatively coupled to a Wavelength Selective Switch (WSS) (62) that is configured to shape ASE from the ASE source to form the one or more shaped ASE signals with one or two or multiple peaks and with associated frequency.

Methods for estimating the Effective Modal Bandwidth (EMB) of laser optimized Multimode Fiber (MMF) at a specified wavelength, λ.sub.S, based on the measured EMB at a first reference measurement wavelength, λ.sub.M. In these methods the Differential Mode Delay (DMD) of a MMF is measured and the Effective Modal Bandwidth (EMB) is computed at a first measurement wavelength. By extracting signal features such as centroids, peak power, pulse widths, and skews, as described in this disclosure, the EMB can be estimated at a second specified wavelength with different degrees of accuracy. The first method estimates the EMB at the second specified wavelength based on measurements at the reference wavelength. The second method predicts if the EMB at the second specified wavelength is equal or greater than a specified bandwidth limit.

A system can include an optical receiver. The optical receiver can have an optical delay component and at least one electrical component (e.g., diode, resistor and/or transistor) operatively coupled to (e.g., integrated within) the optical delay component. The system can further include a processing device, operatively coupled to a memory, that can tune an amount of optical delay implemented by the optical delay component in a low loss and/or low dispersion manner. For example, the processing device can adjust, based on optical delay tuning data (e.g., built-in self-test (BIST) data), the at least one electrical component to modify at least one property of the at least one optical delay component.

A method includes applying, to a modulated digital signal, a forward error correction (FEC) including a low-density parity-check (LDPC) to produce a coded digital signal. Nyquist shaping is applied to the coded digital signal to generate a filtered digital signal. A representation of the filtered digital signal is transmitted in an optical communication channel via a dense wavelength division multiplexing (DWDM) scheme.

A signal processing apparatus includes: a coefficient update unit configured to approximate a characteristic of a transmission line of an optical signal by a first tap coefficient vector of which an LO norm is a predetermined value or less; a zeroing unit configured to generate a second tap coefficient vector by replacing, with 0, a tap coefficient of which an absolute value is less than a threshold among tap coefficients of the first tap coefficient vector; and an adaptive filter configured to perform, based on the second tap coefficient vector, adaptive equalization processing on a digital signal corresponding to an optical signal received via the transmission line.

A wavelength dispersion amount estimation apparatus includes a correlation signal generation unit configured to generate, from a receive signal, a first signal including a main signal of the receive signal and a second signal, which includes an image signal corresponding to the main signal, with a shift by a baud rate of the receive signal relative to the first signal in a frequency domain, a correlation calculation unit configured to calculate a cross correlation of the first signal and the second signal, and a dispersion amount calculation unit configured to calculate a wavelength dispersion amount, based on a position of a peak of the cross correlation.

An optical modulation system comprises a signal source configured to generate an amplitude modulated electrical signal having a bandwidth and divided into frequency components comprising at least a first frequency component covering a first portion of the bandwidth and a second frequency component covering a second portion of the bandwidth; and an electro-optic modulator for receiving an input optical signal, the modulator having a first optical path and a second optical path, the input optical signal being divided between the first optical path and the second optical path and recombined after propagation along the first optical path and the second optical path to produce an output optical signal, and at least one of the first optical path and the second optical path comprising a phase shifter comprising a pair of electrodes in which each electrode is configured to receive a driving signal; wherein the or each phase shifter is coupled to the signal source to receive at least one of said frequency components as a driving signal for an electrode, and the phase shifters are arranged such that the or each phase shifter receives a different pair of driving signals.

Joint estimation of the framer index and the frequency offset in an optical communication system are described among various other features. A transmitter can transmit data frames using pilot and framer symbols. A receiver can estimate the framer index and frequency offset using the pilot and framer symbols, and identify the beginning of a header portion of a data frame. By identifying the beginning of the header portion of a data frame, the receiver can then process data received from the transmitter in a manner synchronous to the manner in which the data was transmitted by the transmitter.