A computation unit uses an assumed chromatic dispersion amount to compensate for dispersion of a coherently received optical signal and performs arithmetic of a signal power of the optical signal that is dispersion compensated. The computation unit performs computation of an evaluation function when a signal power and a delayed signal power obtained by applying a predetermined delay to the signal power satisfy a threshold condition. The evaluation function is a function for evaluating whether the assumed chromatic dispersion amount is a chromatic dispersion amount of the optical signal using the difference between the signal power and the delayed signal power. The chromatic dispersion amount calculation unit calculates a chromatic dispersion amount of the optical signal based on the computation result of the evaluation function by the computation unit when each of a plurality of different assumed chromatic dispersion amounts is used.

An optical network device includes a receiver that receives a polarization multiplexed optical signal and a processor. The processor separates an electric field information signal indicating the polarization multiplexed optical signal into first and second polarization components orthogonal to each other, generates third and fourth polarization components by controlling the first and second polarization components, calculates an evaluation value corresponding to a power of the third or fourth polarization component for each of a plurality of positions on a transmission line, calculates a variation in the evaluation value for a control amount for each of the plurality of positions, and decides whether a first position is a position to be detected based on a result of comparing a variation in an evaluation value for the first position with a variation in an evaluation value for a second position adjacent to the first position.

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.

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.

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.

A state of polarization tracking recovery method and apparatus. The apparatus at least includes a processor configured to fit Stokes vectors to which predetermined symbols correspond of two states of polarization in a received dual-polarization multiplexing optical signal on a Poincare sphere to obtain a fitted plane. The processor calculates a compensation matrix for polarization-dependent loss (PDL) in a Jones space by moving a center of the fitted plane to the origin of the Poincare sphere, and calculates a demultiplexing matrix used for polarization demultiplexing in a Jones space by rotating the fitted plane with the center being moved to the origin until a normal vector of the fitted plane is parallel with a first axis of the Stokes space and rotating the fitted plane with the center being moved to the origin to a plane constituted by a second axis and a third axis of the Stokes space.

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.

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.

Optical transmitters and receivers for improving synchronization of data transmitted over an optical network are described. The receiver can perform non-linear filtering as part of framer index estimation operations to improve the synchronization. The receiver can determine estimated positions of framer indices in data frames received from the transmitter. Next, using a non-linear filter, the receiver can remove estimated positions that are likely erroneous or are greater than a threshold away from the median or mode estimated framer index position. By removing the likely erroneous estimated positions, the receiver can then determine the estimated position of a framer index position for multiple frames with greater confidence.

Provided are a method and apparatus for registering a new terminal using chromatic dispersion distance estimation. The method of registering a new terminal, performed by a transport unit (TU), includes performing frame synchronization through a downstream packet received from a transport node (TN), identifying a position of a frequency of a spectral null and a number of frequencies of spectral nulls through analysis on a frequency spectrum of the received downstream packet, estimating a transmission distance of an optical fiber to the TN, based on the identified position of the frequency of the spectral null and the identified number of frequencies of spectral nulls, and determining a timing of transmitting a registration request message, based on the estimated transmission distance, where the discovery information message is received from the TN.