The present invention relates to a multi-channel IM-DD optical transceiver comprising at least one transmitter and a receiver, and a method for equalizing input samples at an adjusted sampling phase using a quality parameter linearly proportional to a BER. The data transmission and reception use a single master channel and slave channels, which have a baud rate equal to or lower than the baud rate of the master channel. A reliable and identical clocking of all the channels is obtained through either the receiver clock of the master channel when they are received from a single transmitter or a reference clock whose frequency is higher than the highest clock frequency amongst all the channels when they are received from a combination of transmitters. An enhanced timing recovery circuit is also provided to select optimized finite impulse response filters, calculate filter coefficients and generate the receiver clock of the master channel.

An optical receiver includes an optical filter that transmits signal light to be received from wavelength-multiplexed signal light, a light source that outputs local oscillation light, a 90-degree hybrid circuit that causes the local oscillation light output from the light source to interfere with the signal light transmitted through the optical filter to output interference signal light, a converter that converts the interference signal light into an electrical data signal, a spectrum detector that detects a frequency spectrum of the electrical data signal based on the electrical data signal, and a controller that controls a center frequency of a passband of the optical filter based on a shape of the frequency spectrum.

A method of controlling a wavelength of a wavelength tunable laser module includes: referring to data of measured frequencies and wavelength filter control values at two or more points for each basic frequency channel, the data being stored in a memory of a controller; selecting the basic frequency channel closest to a frequency of laser light that a laser light source is instructed to emit; calculating a first wavelength filter control value for providing the instructed frequency of laser light from the data of the measured frequencies allocated to the basic frequency channel closest to the instructed frequency and the wavelength filter control values; and controlling the transmission characteristic of a wavelength filter using the first wavelength filter control value.

A set of media channel (MCh) widths are determined to be used in an optical network. Based on the topology of the network, a first set of MCh widths are computed for tentative use in said optical network, said first set of MCh width defining a target spectral efficiency. A reduced set of MCh widths are generated from said first set of MCh widths by mapping each of the original MCh widths of said first set to a corresponding new MCh width, which is identical with or larger than the original MCh width. An optimization algorithm is used that penalizes MCh widths that are more likely to cause fragmentation problems in the spectrum, and penalizes a decrease in spectral width due to the mapping of an original MCh width of said first set to a new, larger width.

Methods and systems for reach extension of multi-carrier channels using unequal subcarrier spacing may decrease FWM by grouping the subcarriers into groups of 2 subcarriers, and apply a secondary, unequal spacing between the groups. In this manner, nonlinear interactions may be reduced and the transmission reach of a multi-carrier channel may be extended.

A method includes, for each optical fiber path in an optical network, allocating an optical wavelength channel in an optical spectrum such that the allocated optical wavelength channel is assigned to support optical communications over the optical fiber path. The method also includes updating an allocation table in response to performing the allocating for one or more of the optical fiber paths; the allocating including determining the optical wavelength channel to be allocated based on a state of the allocation table. The allocation table indicates optical wavelength channels allocated over optical fiber spans of the optical network. The method also includes defining a set of optical sub-bands to cover a part of the optical spectrum in response to a state of the allocation table satisfying a fullness property. The optical sub-bands are such that each of the allocated wavelength channels is in one of the optical sub-bands.

A wavelength division multiplexing, WDM, network comprising an apparatus adapted to manage a frequency spectrum in the wavelength division multiplexing, WDM, network, the apparatus comprising an adjustment unit adapted to adjust a frequency offset between carriers for each individual carrier depending on performance characteristics of the individual carriers.

In order to identify occupied bands in an optical transmitter with high accuracy, a band identifying circuit includes an optical intensity controller configured to change, by a prescribed level, an optical intensity of an optical signal outputted from a target-of-identification optical transmitter among a plurality of optical signals respectively outputted from a plurality of optical transmitters, constituting a wavelength-multiplexed optical signal, and having mutually different wavelengths, a spectrum acquisition circuit configured to measure an optical intensity of each wavelength of the wavelength-multiplexed optical signal and output a result of the measurement as a spectrum, and a band identifier configured to identify a band occupied by the target-of-identification optical transmitter, based on a change amount of the outputted spectrum.

A processor of an optical transport apparatus is configured to transport an optical multiplexed signal between the optical transport apparatus and a counterpart apparatus by using a plurality of communication units; transmit an arbitrary optical wavelength from the optical multiplexed signal passing through ports by using a wavelength selective switch that has the ports respectively connected to the communication units; control a radio unit in the counterpart apparatus so as to change a frequency of the radio signal in the specified optical wavelength; and change a transmission band of the port through which the optical wavelength passes, according to a change of the frequency of the radio signal. The processor is configured to control an optical transmission unit of the counterpart apparatus so as to change a center wavelength of an optical wavelength passing through the port to a center wavelength of the changed transmission band of the port.

Methods and systems for reach extension of multi-carrier channels using unequal subcarrier spacing may decrease FWM by grouping the subcarriers into groups of 2 subcarriers, and apply a secondary, unequal spacing between the groups. In this manner, nonlinear interactions may be reduced and the transmission reach of a multi-carrier channel may be extended.