First transmission device includes a first counter that generates counter value incremented in a specified cycle. Second transmission device includes a second counter that. generates counter value incremented in the specified cycle. Polarization variation monitoring device acquires a first counter value generated by the first counter and a second counter value extracted by the first transmission device from a received frame transmitted from the second transmission device when the first transmission device detects polarization variation, and a third counter value generated by the second counter and a fourth counter value extracted by the second transmission device from a frame transmitted from the first transmission. device when the second detector detects the polarization variation. The polarization variation monitoring device determines an occurrence position of the polarization variation based on the first counter value, the second counter value, the third counter value and the fourth counter value.

A transmission includes an input shaft and an output shaft, the input shaft selectively accepting a torque input from a prime mover, and the output shaft selectively providing torque output to a driveline. A controller determines a shaft displacement angle representing an angle value of rotational displacement difference between at least two shafts of the transmission, and performs a transmission operation responsive to the shaft displacement angle.

A system and method for performing an in-service optical time domain reflectometry test, an in-service insertion loss test, and an in-service optical frequency domain reflectometry test using a same wavelength as the network communications for point-to-point or point-to-multipoint optical fiber networks while maintaining continuity of network communications are disclosed.

A method is provided for assessing the quality of an optical transmitter and/or its interoperability with a receiver. The method includes obtaining an optical signal output by an optical transmitter and performing coherent optical-to-electrical detection of the optical signal to produce an in-phase receive signal and a quadrature receive signal. The method further includes a computing device emulating a worst-case configuration of an optical fiber with which the optical transmitter is to be used, based on the in-phase receive signal and the quadrature receive signal to produce a noise contribution associated with the worst-case characteristics of the optical fiber and determining a figure of merit of the optical transmitter based on the noise contribution.

This application provides a training sequence determining method and a related device. The method in embodiments of this application includes: An ONU receives a first message sent by an OLT. Then, the ONU determines a target training sequence based on the first message, where the target training sequence is used to determine a working parameter of an equalizer in the OLT. Further, the ONU generates a first data frame including the target training sequence. In this application, the OLT may perform training based on the received target training sequence to determine the working parameter of the equalizer in the OLT.

The disclosed systems and methods for monitoring, by a coherent optical monitor (OPM), generalized optical signal-to-noise ratio (gOSNR) of an optical channel, the method comprising: i) receiving, by an input port of the coherent OPM, a first signal and a second signal, wherein: the first signal and the second signal include same data, the first signal is an optical signal received from the optical channel, and the first signal is affected by a noise; ii) processing, by a digital signal processor (DSP) of the coherent OPM, the first signal and the second signal and extract the data from the first signal and the second signal; iii) computing, by the DSP, a first correlation between the data from the first signal and the data from the second digital signal; and iv) computing, by the DSP, a first gOSNR based on the first correlation.

An extinction ratio testing system (10) includes a microcontroller (102), an extinction ratio tester (104), and a thermostat (106). The microcontroller (102) controls the thermostat (106) to maintain an optical transceiver module (20) at a predetermined high temperature, and then the microcontroller (102) controls the extinction ratio tester (104) to test an extinction ratio of the optical transceiver module (20). If the extinction ratio is lower than a standard extinction ratio, the microcontroller (102) controls the optical transceiver module (20) to increase a laser operating current (212) of the optical transceiver module (20) to increase the extinction ratio.

An optical multiplexer/demultiplexer according to an example embodiment includes: an OCM configured to measure a strength of each of optical signals in a plurality of wavelength bands input to a WSS and to determine an optical signal wavelength band and a noise wavelength band based on the measured strengths; the OCM configured to pass the optical signal in the optical signal wavelength band determined by the OCM as a primary signal; a dummy light generation unit configured to generate dummy light in which the optical signal wavelength band has been extinguished; and an optical coupler configured to multiplex the primary signal output from the WSS with the dummy signal into a wavelength division multiplexing optical signal and to output the wavelength division multiplexing optical signal to an optical transmission path.

A communication apparatus includes a plurality of devices, each of the devices includes a monitoring unit that monitors at least one other device and detects an error that has occurred in the other device, and if an error is detected by the monitoring unit, the device performs a device reset indicating a reset of the operating state of the other device by the monitoring unit or a power source reset indicating a reset of the supply of electric power to the communication apparatus by a chain-of-command unit included in the device.

Embodiments relate to a bidirectional free space optical (FSO) communications system. Specifically, data-encoded FSO beams are transmitted and received between two terminals. A transmit (Tx) direction of a beam transmitted from the first terminal is dithered by a beam steering unit (BSU). As the dithered beam is received by the second terminal, the power levels of the beam are measured. The power levels are then encoded in a data-encoded FSO beam transmitted to the first terminal. This allows the first terminal to decode the received FSO beam and determine the power levels. The power levels allow the first terminal to determine Tx direction misalignments and adjust the Tx direction for the Tx beam sent to the second terminal. This process may be repeated to reduce Tx misalignments and may be performed by both terminals such that each terminal sends power level information to the opposite terminal.