A method of compensating for crosstalk in a mode division multiplexing passive optical network using a technique of transmitter-side crosstalk pre-compensation, performed at the Central Office, in which a downlink reference signal such as a training sequence or pilot signal is retrieved at the transmitter without being influenced by crosstalk effects on its uplink transmission. An uplink reference signal is transmitted in a quasi-single mode transmission along the optical fiber, and a plurality of optical signals input to transmission multiplexer are adapted based on the uplink reference signal to pre-compensate for crosstalk.

A method and system of optical communication are provided. An optical modulator device includes a first and a second waveguide segment, and is configured to modulate an incident optical signal. A first feed-forward equalization (FFE) circuit including an inner first tap and an inner second tap, is configured to equalize the first waveguide segment. A second FFE circuit including a first inner tap and a second inner tap, is configured to equalize the second waveguide segment. An FFE recombination of the first inner tap and the second inner tap of the first and second FFE circuits, is in the electrical domain, respectively. An FFE recombination of the first and second modulation signals, operative to equalize a combination of the first second waveguide segments, is in the optical domain.

A system for processing an electromagnetic signal is described, wherein the system comprises a transmission path with limited dynamic range and a pre-selection unit that is positioned upstream the transmission path. The pre-selection unit is configured to pre-select signal portions and to control the level of the output electromagnetic signal. Further, a method for processing an electromagnetic signal is described.

A wireless communication system includes a baseband processing device configured to transmit a data signal via an optical transmission line, and a wireless device configured to receive the data signal via the optical transmission line and carry out wireless transmission of an output signal obtained by amplifying the data signal, wherein the wireless device is configured to amplify the data signal to generate the output signal, generate a feedback signal according to the output signal, and transmit the feedback signal to the baseband processing device via the optical transmission line, and wherein the baseband processing device is configured to acquire the feedback signal from the wireless device, and execute first processing of multiplying the data signal by a distortion compensation coefficient corresponding to an inverse characteristic of distortion in the radio frequency circuit based on the feedback signal.

An optical communications apparatus comprising a host (100) and an optical module (200) comprising a Mach-Zehnder modulator (202), MZM, wherein the optical module is removably connected to the host via a connection path, the optical communications apparatus comprising: a signal generator (101) at the host, configured to generate a plurality of calibration signals at a plurality of frequencies; a host interface (102) configured to transmit the calibration signals to the optical module via the connection path; a module interface (201) configured to receive the transmitted calibration signals; wherein the MZM is configured to use the calibration signals to modulate a laser light source (206) and biased to a point at which average output power is proportional to the output modulated signal; an optical detector configured to measure an average magnitude of an output of the MZM when each of the calibration signals is used to modulate the laser light source; one of a host calibration unit (103) and a module calibration unit (203), configured to determine a magnitude response of the connection path based on the measured average magnitudes and magnitudes of the respective calibration signals, and further configured to determine a pre-emphasis characteristic based on the magnitude response, the pre-emphasis characteristic for application to signals transmitted by the optical transmitter in use.

An optical transceiver is provided with an optical front end for receiving signal light comprising an optical sub-channel, and for providing an electrical signal based on the signal light; a light source optically coupled to the optical front end for providing local oscillator light thereto for mixing with the signal light; an electro-optical modulator coupled to the light source for receiving output light therefrom and for modulating the output light with digital information to obtain modulated light; and a signal processor operably coupled to the optical front end. The signal processor is configured for processing the electrical signal to obtain a frequency offset of the sub-channel; and adjusting an optical frequency of the modulated light based on the frequency offset. When applied to a multiple-access environment, this may allow access nodes to generate optical sub-channels in the uplink direction using the downlink optical signal as an optical frequency reference.

The present disclosure discloses a method for eliminating nonlinear effects, a transmitter and a receiver. The method includes: setting signals to be transmitted and redundant signals, where the redundant signals are symmetrical to the signals, which are to be transmitted, about Y axis; and after the setting is completed, respectively executing dispersion pre-compensation on the signals to be transmitted and the redundant signals, and executing signal modulation after the dispersion pre-compensation is completed.

An optical transmission system includes N directly-modulated lasers configured to convert N-channel first electrical modulated signals into N-channel optical modulated signals and transmit the N-channel optical modulated signals, N photodetectors configured to receive the N-channel optical modulated signals and convert the N-channel optical modulated signals into N-channel second electrical modulated signals, and at least one of a first MIMO equalizer configured to execute equalization processing for the N-channel first electrical modulated signals, thereby compensating for crosstalk between the N-channel first electrical modulated signals, and a second MIMO equalizer configured to execute equalization processing for the N-channel second electrical modulated signals, thereby compensating for crosstalk between the N-channel second electrical modulated signals, wherein a matrix coefficient based on an impulse response is used in the equalization processing. Hence, the present invention can provide an optical transmission system capable of reducing crosstalk and obtaining a satisfactory BER characteristic.

A method for preventing nonlinear interference in an optical communication system. The method may include selecting an optical signal of a first optical channel. The method may include determining an estimate of inter-channel nonlinear interference to the optical signal of the first optical channel. The inter-channel nonlinear interference may be generated by one or more optical signals transmitted over a second optical channel in the optical communication system. The method may include determining one or more linear filters based on the estimate of the inter-channel nonlinear interference. The method may include pre-distorting an optical signal for transmission over the second optical channel using the one or more linear filters. The pre-distorted optical signal may be configured for reducing the inter-channel nonlinear interference to the first optical signal of the first optical channel. The method may include transmitting the pre-distorted optical signal over the second optical channel through an optical transmission medium.

A burst optical signal transmission device which includes a light source for generating and outputting burst signal light, a light source driving circuit for outputting, to the light source, a driving signal for switching between an output time and a stop time of the burst signal light, based on a burst control signal, and a pre-emphasis circuit for outputting a pre-emphasis control signal for superimposing an additional signal for charging a capacitor included in the light source, onto the driving signal, at a timing in the vicinity of the beginning of the burst control signal.