An optical communications system includes a modulator/demodulator (modem) to transmit outgoing communications data and to receive incoming communications data in a transceiver. A main detector is coupled to the modem to convert an optical signal representing the incoming communications data to an electrical signal for the modem. An adaptive data rate processor monitors the electrical signal from the main detector to determine a current power level for the optical signal. The adaptive data rate processor dynamically adjusts a data rate of the modem based on the determined current power level of the optical signal.

An optical communications system includes a modulator/demodulator (modem) to transmit outgoing communications data and to receive incoming communications data in a transceiver. A main detector is coupled to the modem to convert an optical signal representing the incoming communications data to an electrical signal for the modem. An adaptive data rate processor monitors the electrical signal from the main detector to determine a current power level for the optical signal. The adaptive data rate processor dynamically adjusts a data rate of the modem based on the determined current power level of the optical signal.

Methods for configuring an optical link in which a distribution of transmission data rates and line rates are configured for a predetermined amount of optical bandwidth to maximize transmission capacity. In these methods, a controller of an optical network obtains input parameters that include a signal-to-noise ratio (SNR) for optical signals and an allocated bandwidth of the optical link, further obtains, for each line rate, a mapping of transmission data rates along a frequency spectrum of the allocated bandwidth compatible with the SNR, and generates a channel plan in which a number of traffic modes and a distribution of a plurality of channels in the allocated bandwidth are set to maximize transmission capacity. The plurality of channels is used for transmitting the signals on the optical link. The controller configures at least one optical network element in the optical network to establish the optical link based on the channel plan.

An optical receiver includes a transimpedance amplifier that converts a current signal corresponding to an optical signal into a voltage signal. The transimpedance amplifier includes an input terminal receiving the current signal, an output terminal outputting the voltage signal, an inverting circuit including a pull-up device that pull-up drives the voltage signal of the output terminal according to the current signal, and a pull-down device that pull-down drives the voltage signal of the output terminal according to the current signal, a feedback resistor electrically connected between the input and output terminals, a first resistor electrically connected between the input terminal and the pull-up device, and a second resistor electrically connected between the input terminal and the pull-down device.

A photonic random signal generator includes an incoherent optical source configured to generate an optical noise signal, a filter configured to generate a filtered optical noise signal using the optical noise signal, a coupler, a photodetector, a filter, and a limiter. The coupler couples the filtered optical noise signal and a delayed version of the filtered optical noise signal to generate a first coupled signal and a second coupled signal. The photodetector generates an output signal representative of a phase difference between the filtered optical noise signal and the delayed version of the filtered optical noise signal using the first coupled signal and the second coupled signal. The filter filters the output signal representative of the phase difference to generate an analog random signal. The limiter thresholds the analog random signal based on a clock signal, to generate a digital random signal.

A free-space optical (FSO) communication system includes a transmitter including a modulated light source and transmit optics for emitting a modulated optical signal into a FS channel toward a receiver. A receiver is coupled to receive the modulated optical signal including receive optics coupled to a few-mode (FM) pre-amplifier that is coupled to a demodulator.

An optical communication apparatus includes an interface circuit that acquires bit rate information of an optical network, and a processor that selects a modulation scheme in accordance with the bit rate information and operates in the modulation scheme, wherein the processor is configured to select a first modulation scheme when the bit rate is equal to or greater than a first value, and select a second modulation scheme when the bit rate is smaller than the first value, the second modulation scheme having a data transfer performance higher than the first modulation scheme.

An optical receiver includes a transimpedance amplifier that converts a current signal corresponding to an optical signal into a voltage signal. The transimpedance amplifier includes an input terminal receiving the current signal, an output terminal outputting the voltage signal, an inverting circuit including a pull-up device that pull-up drives the voltage signal of the output terminal according to the current signal, and a pull-down device that pull-down drives the voltage signal of the output terminal according to the current signal, a feedback resistor electrically connected between the input and output terminals, a first resistor electrically connected between the input terminal and the pull-up device, and a second resistor electrically connected between the input terminal and the pull-down device.

An operation method of a network device and a control chip of the network device are provided. The network device receives an input signal through a fiber medium. The operation method includes the following steps: setting a target speed of the network device to a first speed; transmitting and/or receiving a data at the first speed; and setting the target speed of the network device to a second speed which is different from the first speed when the amplitude or energy of the input signal is not greater than a threshold.

This application provides a data transmission method and apparatus. The method includes: processing, by a network device, a to-be-sent optical data unit ODU to obtain another ODU, where a bit rate of the another ODU is lower than a bit rate of the ODU; and sending, by the network device, the another ODU. In embodiments of this application, the ODU is processed to obtain the another ODU with a lower bit rate, and this helps reduce a rate increase when service data is transmitted in an OTN, so as to reduce an OTN interface rate and OTN costs.