Embodiments of the present disclosure provide an optical signal transmission method, apparatus, and device. The method at a first device side comprises: n first colored optical modules respectively transmit optical signals with the frequency being f and the wavelengths respectively being λ1-λn, wherein λ1-λn are different from each other; and in-band optical layer operation, administration, and maintenance (0AM) information with the modulation frequency being k1-kn is separately superimposed on the optical signals with the wavelengths respectively being λ1-λn.

A polarimeter system integrated into an optical line system includes a transmitter coupled to a transmit filter communicatively coupled to an output port in an optical line device, wherein the transmitter is configured to generate a polarization probe signal, and wherein a wavelength of the polarization probe signal is configured to operate in-service with traffic-bearing channels on the output port; and a polarimeter receiver coupled to a receive filter communicatively coupled to an input port in the optical line device, wherein the polarimeter receiver is configured to vary arrangement of input light from the filter and to measure various outputs of the varied arrangement to derive measurement of State of Polarization (SOP) of the input light.

An apparatus and method for providing a differential latency, DL, between an upstream, US, transmission and a downstream, DS, transmission via an optical transmission link (OTL), said apparatus comprising a measurement unit (2) configured to measure the round trip delays, RTD, of at least two measurement signals having different measurement wavelengths; and a processing unit (3) configured to derive an upstream, US, delay of at least one optical signal at an upstream wavelength from the at least two measured round trip delays, RTD, and to derive a downstream, DS, delay of at least one optical signal at a downstream wavelength from the at least two measured round trip delays, RTD, wherein the differential latency, DL, is calculated on the basis of the derived delays, RTD.

Using pump-probe measurements on multi-span optical links may result in the determination of one or more of the following: 1) wavelength-dependent power profile and gain evolution along the optical link; 2) wavelength-dependent dispersion map; and 3) location of regions of high polarization-dependent loss (PDL) and polarization-mode dispersion (PMD). Such measurements may be a useful diagnostic for maintenance and upgrade activities on deployed cables as well as for commissioning new cables.

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.

A management system for an optical line system includes one or more processors and memory storing instructions that, when executed, cause the one or more processors to receive State of Polarization (SOP) measurements from one or more optical components in the optical line system, wherein the SOP measurements are taken while traffic-bearing channels are operating, and monitor health of one or more fibers based on the SOP measurements. The health can include detection and/or localization of SOP transients.

A management system for an optical line system includes one or more processors and memory storing instructions that, when executed, cause the one or more processors to receive State of Polarization (SOP) measurements from one or more optical components in the optical line system, wherein the SOP measurements are taken while traffic-bearing channels are operating, and monitor health of one or more fibers based on the SOP measurements. The health can include detection and/or localization of SOP transients.

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.

Systems and methods for remotely turning on and turning up a Raman amplifier are provided. In one embodiment, a method includes the step of turning on one or more Raman pumps of a Raman amplifier to a predetermined safe gain or power level. The method also includes determining an estimated loss along a fiber optic span of a link between adjacent nodes of an optical network. Responsive to the estimated loss being greater than a reach of an Optical Supervisory Channel (OSC) signal along the link, the method includes the step of adjusting the gain or power level of the one or more Raman pumps.