An optical transmission system includes an optical transmitter, an optical receiver, and a control apparatus. The control apparatus repeatedly performs an adjustment process for adjusting power of an optical signal of a frequency band to be adjusted while switching the frequency band to be adjusted between at least two frequency bands including at least a frequency band where stimulated Raman scattering occurs among frequency bands that are multiplexed in a multiplexed optical signal transmitted by the optical transmission system. In the adjustment process, when power of an optical signal of the frequency band to be adjusted transmitted from the optical transmitter has been changed, the control apparatus determines the power of the optical signal of the frequency band to be adjusted on the basis of a signal quality measured by the optical receiver that has received the optical signal.

The disclosed systems, structures, and methods are directed to an optical communication comprising a first wavelength division multiplexer (WDM) configured to receive WDM signals, the first WDM is further configured to split the received WDM signals into C band WDM signals and L band WDM signals, a C band amplifier configured and an L band amplifier configured to amplify the C band WDM signals and L band WDM signals respectively and compute a fast total instantaneous powers P.sub.tot-CBand(t) and P.sub.tot-LBand(t) on a fast time scale, a slow per channel power detector configured to extract slow per channel powers P(.sub.1), P(.sub.2) . . . P(.sub.n) on a slow time scale, a Stimulated Raman Scattering (SRS) estimator configured to estimate an SRS induced gain change in the WDM signals, and a second WDM configured to combine and transmit the amplified C band WDM signals and L band WDM signals over optical cables.

A system for an aircraft that includes a plurality of zones including: a first fiber optic cable routed through a zone of the plurality of zones. The first fiber optic cable is attached to a landing gear of the aircraft in the zone of the plurality of zones; and a first controller configured to provide a first optical signal to the first fiber optic cable and obtain a first optical response signal from the first fiber optic cable. The first controller is further configured to determine at least one temperature within the zone of the plurality of zones based on the first optical response signal, the first optical signal, and coherent optical frequency domain reflectometry (COFDR).

A system for an aircraft that includes a plurality of zones including: a first fiber optic cable routed through a zone of the plurality of zones. The first fiber optic cable is attached to a landing gear of the aircraft in the zone of the plurality of zones; and a first controller configured to provide a first optical signal to the first fiber optic cable and obtain a first optical response signal from the first fiber optic cable. The first controller is further configured to determine at least one temperature within the zone of the plurality of zones based on the first optical response signal, the first optical signal, and coherent optical frequency domain reflectometry (COFDR).

This application provides a submarine network device and a submarine cable system that may accurately detect a fault of a submarine optical repeater in time. The device comprises: a first fiber and a second fiber; at least one first pump laser, configured to supply pumping light to a first optical amplification unit located in the first fiber; the first optical amplification unit, configured to amplify and then output a first probe signal sent from a first site to a second site; a first fiber coupler located in the first fiber, configured to receive a first reflected optical signal obtained from the first probe signal after Rayleigh backscattering, and send a portion of the first reflected optical signal to a second fiber coupler located in the second fiber; at least one second pump laser, configured to supply pumping light to a second optical amplification unit; a second optical amplification unit, configured to amplify and then output a second data optical signal sent by the second site to the first site; and a second fiber coupler, configured to receive a portion of the first reflected optical signal output by the first fiber coupler.

This application provides a submarine network device and a submarine cable system that may accurately detect a fault of a submarine optical repeater in time. The device comprises: a first fiber and a second fiber; at least one first pump laser, configured to supply pumping light to a first optical amplification unit located in the first fiber; the first optical amplification unit, configured to amplify and then output a first probe signal sent from a first site to a second site; a first fiber coupler located in the first fiber, configured to receive a first reflected optical signal obtained from the first probe signal after Rayleigh backscattering, and send a portion of the first reflected optical signal to a second fiber coupler located in the second fiber; at least one second pump laser, configured to supply pumping light to a second optical amplification unit; a second optical amplification unit, configured to amplify and then output a second data optical signal sent by the second site to the first site; and a second fiber coupler, configured to receive a portion of the first reflected optical signal output by the first fiber coupler.

An RF signal to be carried by an optical link is modulated onto two optical beams. The modulators are tuned differently so that the distortion products carried on one beam are relatively larger compared to the fundamental compared with other beam. One of the beams is optically upconverted by the appropriate Brillouin shift frequency and the two beams counter-propagated through an optical waveguide in order to create a Brillouin grating. The grating acts to separate the distortion products from the fundamental so as to provide at an output of the link a signal in which the distortion products are insignificant is not absent.

An RF signal to be carried by an optical link is modulated onto two optical beams. The modulators are tuned differently so that the distortion products carried on one beam are relatively larger compared to the fundamental compared with other beam. One of the beams is optically upconverted by the appropriate Brillouin shift frequency and the two beams counter-propagated through an optical waveguide in order to create a Brillouin grating. The grating acts to separate the distortion products from the fundamental so as to provide at an output of the link a signal in which the distortion products are insignificant is not absent.

An optical power compensation method and a device relating to the communications field comprises: a first node that obtains a first optical power and a first timepoint, receives at least two second optical powers sent by a second node, obtains second timepoints corresponding with the at least two second optical powers, where the second timepoint is a timepoint at which the first node receives the second optical power, and determines a target timepoint from the second timepoints according to a preset delay and the first timepoint. The first node determines a variation of a span loss according to a target optical power and the first optical power, where the target optical power is a second optical power corresponding to the target timepoint, and adjusts a gain value and/or an attenuation value of the first node according to the variation of the span loss.

A radio frequency (RF) photonic equalizer may include a first electro-optic (E/O) modulator configured to modulate an optical carrier based upon an RF input signal, a stimulated Brillouin scattering (SBS) medium coupled to the first E/O modulator, and a second E/O modulator configured to modulate the optical carrier based upon an equalizing function waveform. An optical circulator may be coupled to the SBS medium and the second E/O modulator, and a photodetector may be coupled to the optical circulator.