An optical transceiver system includes an optical transceiver chassis including a cable connector, a laser subsystem, and a sensor subsystem. A controller included in the optical transceiver chassis is coupled to the laser subsystem and the sensor subsystem. The controller receives a cable connection signal from the sensor subsystem that indicates that a cable has been connected to the cable connector included on the optical transceiver chassis and, in response, activates the laser subsystem. Subsequent to activating the laser subsystem, the controller receives a cable disconnection signal from the sensor subsystem that indicates that the cable has been disconnected from the cable connector included on the optical transceiver chassis and, in response, deactivates the laser subsystem.

In order to improve reception sensitivity of a response signal at a terminal station, an optical transmission device includes a reception unit that receives a control signal including a predetermined instruction and a main signal, via an optical transmission path connected to the terminal station, a control unit that performs the predetermined instruction of the received control signal, an extraction unit that extracts light in a band of the control signal, a response signal generation unit that modulates the extracted light in the band of the control signal, and outputs a response signal, and a multiplexing unit that multiplexes and outputs the response signal and the main signal. The control unit controls modulation by the response signal generation unit according to the control signal.

An optical transmission apparatus includes the optical transceiver configured to generate a test light for each wavelength assignable to the wavelength multiplex light to transmit the test light to the optical transmission line via the wavelength multiplexer and demultiplexer, detect a reflected light for the test light from the optical transmission line, calculate an arrival distance of the test light for the each wavelength from the reflected light for the each wavelength, and set a wavelength having a longest arrival distance among the arrival distances for the respective wavelengths, as a wavelength to be assigned to the signal light in the optical transceiver.

System and method for fiber-optic time frequency and data joint transmission, comprising local end, relay nodes, and remote end. In each local end, relay node, and remote end, multiplexing and demultiplexing of time frequency signals, optical supervisory signals, and optical communication data services are performed by CWDM modules and OSC-band wavelength multiplexer/demultiplexers, and processing (transmitting, relaying, receiving) is performed by corresponding processing modules for joint transmission. A sub-band of standard OSC band is used for transmitting time frequency signal so that transmission of optical supervisory signal is not influenced while no extra band resource is occupied with improved utilization of wavelength resources and reduced costs. Wavelengths of time and frequency transfer in both directions in sub-band of OSC band are flexibly selected and combined to meet different requirements; wavelengths are close or same so that bidirectional symmetry of the link is guaranteed to the maximum with improved precision.

A transmission device that transmits main signal light to another transmission device via a transmission path, the transmission device includes a transmitter that generates monitoring signal light with intensity modulation based on a signal related to monitoring control of the transmission device and the other transmission device, a multiplexer that multiplexes the monitoring signal light into the main signal light, a receiver that acquires light receiving information from the other transmission device, the light receiving information being related to a light receiving state of the monitoring signal light, and a control circuit that controls a modulation degree of the intensity modulation in accordance with the light receiving information.

An optical line device for use in an optical line system is configured to connect to a second optical line device via a transmit fiber and a receive fiber. The optical line device includes a transmitter connected to the transmit fiber via an output port of the optical line device, wherein the transmitter is configured to transmit a polarization probe signal at a wavelength outside of a band of wavelengths used for traffic-bearing channels in the optical line signal, to a second polarimeter receiver at the second optical line device; and a polarimeter receiver connected to the receive fiber via an input port of the optical line device, wherein the polarimeter receiver is configured to receive a second polarization probe signal from a second transmitter transmitted from the second optical line device and to derive a measurement of SOP on the receive fiber based on the second polarization probe signal.

In order to improve reception sensitivity of a response signal at a terminal station, an optical transmission device includes a reception unit that receives a control signal including a predetermined instruction and a main signal, via an optical transmission path connected to the terminal station, a control unit that performs the predetermined instruction of the received control signal, an extraction unit that extracts light in a band of the control signal, a response signal generation unit that modulates the extracted light in the band of the control signal, and outputs a response signal, and a multiplexing unit that multiplexes and outputs the response signal and the main signal. The control unit controls modulation by the response signal generation unit according to the control signal.

A polarimeter includes a Polarization Maintaining (PM) coupler with an input configured to receive input light and split the input light to a first output and a second output; a first PM fiber coupled to the first output; a second PM fiber coupled to the second output; a first polarization device coupled to the first PM fiber; a second polarization device coupled to the second PM fiber; and a plurality of detectors coupled to the first polarization device and the second polarization device, wherein outputs i.sub.1, i.sub.2, i.sub.3, i.sub.4 are determined based on outputs of the plurality of detectors, the outputs i.sub.1, i.sub.2, i.sub.3, i.sub.4 are linear projections of corresponding Stokes Parameters of the input light.

An optical transmission apparatus includes the optical transceiver configured to generate a test light for each wavelength assignable to the wavelength multiplex light to transmit the test light to the optical transmission line via the wavelength multiplexer and demultiplexer, detect a reflected light for the test light from the optical transmission line, calculate an arrival distance of the test light for the each wavelength from the reflected light for the each wavelength, and set a wavelength having a longest arrival distance among the arrival distances for the respective wavelengths, as a wavelength to be assigned to the signal light in the optical transceiver.

An optical signal is transmitted between first and second transmission devices. When a network control device receives a shutdown report that indicates a loss of light from both of the first and second transmission devices, the network control device transmits a first instruction to resume a transmission of a control signal to both of the first and second transmission devices. When the network control device receives a detection report that indicates a reception of the control signal from both of the first and second transmission devices, the network control device transmits a second instruction to resume a transmission of a WDM signal to both of the first and second transmission devices.