Aspects of the present disclosure describe distributed fiber optic sensing (DFOS) systems, methods, and structures that advantageously overcome problems encountered when operating DFOS systems over operational telecommunications facilities namely, cross-phase modulation, and uneven amplitude profiles through the use of a novel constant amplitude coded DFOS employing out-of-band signaling.

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.

Aspects of the present disclosure describe distributed fiber optic sensing (DFOS) systems, methods, and structures that advantageously overcome problems encountered when operating DFOS systems over operational telecommunications facilities namely, cross-phase modulation, and uneven amplitude profiles through the use of a novel constant amplitude coded DFOS employing out-of-band signaling.

An optical transmission system includes ground stations; optical-terminating devices; a traffic-monitoring unit that detects a traffic amount of the uplink signal transmitted in a time-division multiplexing manner for each of the optical-terminating devices; and a bandwidth allocation calculation unit that estimates one optical-terminating device of the optical-terminating devices connected to one ground station of the ground stations having a cell where the moving object is positioned on the basis of the traffic amount, and calculates a first allocation amount of a bandwidth allocated to the uplink signal of the one optical-terminating device connected to the one ground station having the cell where the moving object is positioned and a second allocation amount of a bandwidth allocated to the uplink signal of another optical-terminating device of the optical-terminating devices connected to another ground station of the ground stations having a cell adjacent to the cell where the moving object is positioned.

A rate negotiation method is provided. A first device switches a fiber transmission rate of a first port of the first device to a first fiber transmission rate based on a preset switching direction within a rotation period of a first fiber transmission rate set. The first device sends a negotiation packet to a second device through the first port of the first device within duration of the first fiber transmission rate. If a response packet is received from the second device through the first port of the first device within the duration of the first fiber transmission rate, the first port of the first device is controlled to communicate with the second device based on the first fiber transmission rate.

An optical receiver capable of substantially measuring the phase and amplitude of a received intensity- or amplitude-modulated optical signal by performing digital-signal processing. In an example embodiment, a DSP of the receiver operates to reduce the detrimental effects of relative phase noise between the optical reference oscillator and optical carrier based on an optical pilot present in the received optical signal. The DSP may employ a sequence of digital filters configured to select a signal component that represents a non-vestigial modulation sideband and then perform signal equalization thereon. The signal equalization may include but is not limited to dispersion compensation. In some embodiments, the optical receiver can be a direct-detection optical receiver. In an example embodiment, the optical reference oscillator and optical carrier are generated using two respective independently running lasers that may or may not be co-located.

Systems and methods for constellation shaping using low rate loss bit-level distribution matchers include receiving blocks of input bits and, for each input block of a predetermined size, assigning a respective codeword of a predetermined output block size. The number of bits of a given bit value in the codeword is dependent on a predetermined target probability distribution. A one-to-one mapping exists between each possible combination of input bits and a codeword for input blocks containing the combination. Some codewords include a number of bits having the given bit value that is different than the predetermined target probability distribution, but an average number of bits having the given bit value in the available codewords meets the predetermined target probability distribution. The disclosed methods result in more available codewords and a lower rate loss than in bit-level distribution matchers with a constant modulus, while achieving similar shaping.

Provided in the invention is a circuit for multiplexing an MON pin of a receiver optical sub-assembly for optical communication. Through a first clamping circuit, the high precision of a whole monitoring dynamic range is kept. Through a second clamping circuit, a voltage of the MON pin is clamped into an input voltage Vcont_in of the second clamping circuit, so that an external control signal Vcont_in is copied and input into the trans-impedance amplifier, and then the Vcont_in is converted into various control variables through a comparator or analog-to-digital converter.

Provided in the invention is a circuit for multiplexing an MON pin of a receiver optical sub-assembly for optical communication. Through a first clamping circuit, the high precision of a whole monitoring dynamic range is kept. Through a second clamping circuit, a voltage of the MON pin is clamped into an input voltage Vcont_in of the second clamping circuit, so that an external control signal Vcont_in is copied and input into the trans-impedance amplifier, and then the Vcont_in is converted into various control variables through a comparator or analog-to-digital converter.

This application provides data transmission methods and apparatuses. One method includes: processing, by a network device, a first optical data unit (ODU) to obtain a second ODU, wherein a bit rate of the second ODU is lower than a bit rate of the first ODU; and sending, by the network device, the second ODU.