The light multiplexing/demultiplexing device comprises: a first demultiplexer that demultiplexes an inputted first wavelength-multiplexed signal light into a first signal light of a first wavelength band and a second signal light of a second wavelength band and outputs the first and the second signal light; a first amplifier that amplifies the second signal light from the first demultiplexer; a light processor that, based on the inputted second signal light and an inputted third signal light of the second wavelength band, outputs a fourth signal light; and a first multiplexer that multiplexes the fourth signal light with the first signal light from the first demultiplexer, further, the gain of the first amplifier is set such that the difference between power of the first signal light outputted from the first multiplexer and power of the fourth signal light outputted from the first multiplexer is equal to or less than a predetermined value.

An optical relay device includes a WSS functioning as a wavelength selective switch capable of performing path switching in wavelength units and optical level adjustment for each of wavelengths and a control device that instructs, on the basis of a fluctuation amount of an optical level for each of the wavelengths of an optical signal output from the WSS and setting information indicating, for each of the wavelengths, whether optical level adjustment for the wavelengths of the optical signal is enabled, the WSS to perform a setting change of an optical level adjustment amount of the optical signal.

In some embodiments, a system includes a set of servers, a set of switches within a switch fabric, and an optical device. The optical device is operatively coupled to the set of servers via a first set of optical fibers. Each server from the set of servers is associated with at least one wavelength from a set of wavelengths upon connection to the optical device. The optical device is operatively coupled to each switch from a set of switches via an optical fiber from a second set of optical fibers. The optical device, when operative, wavelength demultiplexes optical signals received from each switch from the set of switches, and sends, for each wavelength from the set of wavelengths, optical signals for that wavelength to the server from the set of servers.

Systems and methods for measuring the in-phase/quadrature (I/Q) skew of optical signals. The method may be used to characterize the I/Q skew of optical signals transmitted by optical coherent transponders in complex modulation formats. The method may include providing an input signal to a transponder to produce a periodic (and generally sinusoidal) output signal, providing the output signal to a test system including an optical spectrum analyzer, measuring the optical power of a first harmonic of the signal, and comparing the measured optical power to calibration data to determine the I/Q skew. The optical power may be analyzed in a portion of the spectrum where sensitivity of the power to changes in skew is highest. The calibration data may map previously-obtained optical power measurements to corresponding known skew amounts. The system may provide more accurate skew measurements using less expensive equipment than existing skew measurement methods.

A data communication system comprises an optical transferring device, optical network units, and user processors. The optical transferring device splits a received optical signal into split optical signals. Each optical network unit transforms a respective split optical signal into M first electronic signals, M>1. Each user processor comprises an input mapping unit to map the respective M first electronic signals into N second electronic signals, N?M; an equalization processor to equalize the N second electronic signals and generate a set of N equalized electronic signals; a wave-front demultiplexer to perform a wave-front demultiplexing transform on the N equalized electronic signals, and output N wave-front demultiplexed signals, each of the N wave-front demultiplexed signals being a unique linear combination of the N equalized electronic signals; and an output mapping unit to map the N wave-front demultiplexed signals into at least M third digital electronic data signals.

An analog radio over fiber (AROF) wavelength division multiplexing (WDM) system and method for reducing adjacent channel leakage ratio (ACLR) in a radio frequency signal provided by an AROF WDM system are provided. The AROF WDM system comprises a plurality of transmitters, a multiplexer, a demultiplexer, a plurality of receivers and a controller. Each transmitter is for receiving a radio frequency input signal and for modulating the radio frequency input signal onto an optical signal to obtain a modulated optical signal. The multiplexer is for receiving each modulated optical signal from the plurality of transmitters and for combining the modulated optical signals into a combined optical signal to be sent a distance over an optical fiber. The multiplexer has a pluralities of passbands with each passband having a center wavelength. The demultiplexer is for receiving the combined optical signal and for separating the combined optical signal back into the individual modulated optical signals. Each receiver is for receiving one of the modulated optical signals from the demultiplexer and for converting the received modulated optical signal into a radio frequency output signal. The controller is configured to detune, for each transmitter, one of that transmitter and the multiplexer relative to the other such that a wavelength of the modulated optical signal transmitted by that transmitter is longer than the center wavelength of a corresponding one of the plurality of passbands of the multiplexer.

Disclosed is a method for monitoring the wavelength of a tunable laser device of user by local OLT. The method is applied to a wavelength division multiplexing passive optical network framework. The framework comprises an ONU, a first athermal array waveguide grating, a transmission optical fiber, a second athermal array waveguide grating and the OLT, which are sequentially connected. ONU comprises tunable wavelength optical transmitters. The method comprises: starting handshaking is carried out between the OLT and the ONU; and the OLT carries out wavelength drifting monitoring during operation of the ONU. Wavelength adjustment can be carried out on the multi-channel tunable laser device in an external auxiliary monitoring environment, thus channel wavelengths of the multi-channel tunable laser device can be accurately controlled, and the requirement for calibration accuracy of channels of the tunable laser device at the ONU is greatly reduced.

An optical switch (10) comprising: inputs (12) to receive input optical signals at respective wavelengths and having planar wavefronts; conversion apparatus (14) to convert each input optical signal into a respective optical signal having a respective helical wavefront, each helical wavefront having a different orbital angular momentum, OAM; optical multiplexing apparatus (16) to receive each helical wavefront optical signal from the conversion apparatus and to multiplex the helical wavefront optical signals into an OAM multiplexed optical signal; and optical demultiplexing apparatus (18) comprising a plurality of outputs (20), the optical demultiplexing apparatus arranged to: receive the OAM multiplexed optical signal; demultiplex the OAM multiplexed optical signal into a plurality of wavelength multiplexed optical signals each having a different OAM; reconvert each wavelength multiplexed optical signal from its helical wavefront into a respective planar wavefront; and deliver each planar wavefront wavelength multiplexed optical signal to a respective one of the outputs according to the respective OAM it had before reconversion.

An apparatus comprising a polarization beam splitter optically coupled to a first light path and a second light path and configured to receive a CW light having a plurality of wavelengths, forward a first light beam of the CW light along the first light path, and forward a second light beam of the CW light along the second light path. A first multiplexer coupled to the first light path and configured to de-multiplex the first light beam into a first plurality of channels each corresponding to one of the plurality of wavelengths. A second multiplexer coupled to the second light path and configured to de-multiplex the second light beam into a second plurality of channels each corresponding to one of the plurality of wavelengths. A modulator coupled to the first multiplexer and the second multiplexer and configured to modulate the first plurality of channels and the second plurality of channels.

An optical transmission device and an optical communication system being capable of coping with various installation forms of a transponder in a unit of optical fiber transmission path are provided. The optical transmission device is installed inside a station building. First and second interface units are connected to first and second fiber transmission paths accommodated in a submarine optical fiber cable. A first fiber transmission path mediates an optical signal to be transmitted between the first interface unit and a first transponder. A second fiber transmission path mediates an optical signal to be transmitted between the second interface unit and a second transponder.