First data and second data are transmitted by a simple configuration by including a generation unit that generates a wavelength-changed signal on the basis of the second data, and a transmission unit that transmits the wavelength-changed signal together with a first signal that indicates the first data.

Embodiments of the invention provides a deterministic scrambler (1) arranged in a multimode optical fiber (130) for scrambling light, the light comprising a set of optical signals propagated in said multimode optical fiber according to a set of propagation modes, each propagation mode being associated with a power value, wherein the scrambler is configured to determine a permutation of said propagation modes depending on the power values associated with said propagation modes, the scrambler being configured to redistribute the optical signals according to said permutation of the propagation modes.

A coherent optical receiver includes a plurality of components arranged in a receive signal path and a local oscillator signal path, wherein the plurality of components include one or more variable optical attenuators (VOAs) that, when actuated, generate low phase change between the receive signal path and the local oscillator signal path. With this approach, the low phase change between the receive signal path and the local oscillator signal path are substantially canceled out with some minor phase differences remaining.

A method and a system for pilot-aided feedforward data recovery are provided. The method and system include a receiver including a strong local oscillator operating in a free running mode independent of a signal light source. The phase relation between the signal light source and the local oscillator source is determined based on quadrature measurements on pilot pulses from the signal light source. Using the above phase relation, information encoded in an incoming signal can be recovered, optionally for use in communication with classical coherent communication protocols and quantum communication protocols.

In a coherent optical receiver, a received signal and an oscillator-generated signal, having frequency difference such that the receiver operates under intradyne conditions, are made to beat in a 33 optical coupler. A polarizing beam-splitter splits one of the signals into components with orthogonal polarization which are applied to inputs of the coupler, which receives the other of the received or oscillator-generated signal. After photoelectric conversion, the signals are fed to analog processing devices generating an electrical signal representing the received signal that is fed to a low pass filter before being demodulated. The frequency difference between the signals and the passband of the filter are such that a component of the electrical signal, oscillating at a frequency depending on the frequency difference and having amplitude and phase depending on the instant state of polarization of the received signal, is suppressed. A method is also provided.

In a coherent optical receiver receiving a polarization multiplexed optical signal through an optical communications network, a method of compensating noise due to polarization dependent loss (PDL). A Least Mean Squares (LMS) compensation block processes sample streams of the received optical signal to generate symbol estimates of symbols modulated onto each transmitted polarization of the optical signal. A decorrelation block de-correlates noise in the respective symbol estimates of each transmitted polarization and generating a set of decorrelated coordinate signals. A maximum likelihood estimator soft decodes the de-correlated coordinate signals generated by the decorrelation block.

A method and a system for pilot-aided feedforward data recovery are provided. The method and system include a receiver including a strong local oscillator operating in a free running mode independent of a signal light source. The phase relation between the signal light source and the local oscillator source is determined based on quadrature measurements on pilot pulses from the signal light source. Using the above phase relation, information encoded in an incoming signal can be recovered, optionally for use in communication with classical coherent communication protocols and quantum communication protocols.

A dual-polarization, 2-subcarriers code orthogonal, orthogonal frequency division multiplexed signal carrying information bits is transmitted in an optical communication network without transmitting a corresponding pilot tone or training sequence. A receiver receives the transmitted signal and recovers information bits using a blind equalization technique and by equalizing the 2-subcarriers OFDM signal as a 9-QAM signal in time domain with a CMMA (constant multi modulus algorithm) equalization method.

An optical communication device includes a laser, a transmitter (Tx), a receiver (Rx) and a device controller. The laser is configured to generate an optical carrier. The transmitter is configured to generate an optical Tx signal using the optical carrier and to transmit the optical Tx signal to a peer optical communication device. The receiver is configured to receive an optical Rx signal from the peer optical communication device, and to down-convert the optical Rx signal using the optical carrier. The device controller is configured to adjust a frequency of the laser to reduce a Carrier Frequency Offset (CFO) between the received optical Rx signal and the optical carrier generated by the laser, including conditionally applying to a frequency of the laser a series of frequency hops in accordance with a defined dithering sequence.

In a coherent optical receiver, a received signal and an oscillator-generated signal, having frequency difference such that the receiver operates under intradyne conditions, are made to beat in a 33 optical coupler. A polarising beam-splitter splits one of the signals into components with orthogonal polarisation which are applied to inputs of the coupler, which receives the other of the received or oscillator-generated signal. After photoelectric conversion, the signals are fed to analogue processing devices generating an electrical signal representing the received signal that is fed to a low pass filter before being demodulated. The frequency difference between the signals and the passband of the filter are such that a component of the electrical signal, oscillating at a frequency depending on the frequency difference and having amplitude and phase depending on the instant state of polarisation of the received signal, is suppressed. A method is also provided.