An optical repeater is a C+L-band repeater inserted between a first transmission path fiber and a second transmission path fiber. The optical repeater includes: a first optical fiber amplifier inserted in a first line, for amplifying a C-band signal; a second optical fiber amplifier inserted in a second line, for amplifying an L-band signal; a third optical fiber amplifier inserted in a third line, for amplifying a C-band signal; a fourth optical fiber amplifier inserted in a fourth line, for amplifying an L-band signal; and a first loopback means provided between an input to the first optical fiber amplifier or an output from the first optical fiber amplifier and an input to the third optical fiber amplifier or an output from the third optical fiber amplifier.

An excitation light source apparatus capable of assuring an excellent optical transmission characteristic even at occurrence of a gain tilt is provided. The excitation light source apparatus comprises an excitation light outputting means, a control signal detection means, a control signal detection means, an excitation light control means, and a multiplexing means. The excitation light outputting means outputs excitation light for Raman amplification. The control signal detection means detects a control signal of the excitation light outputting means from beams of WDM signal light transmitted through optical fibers in an upstream direction and a downstream direction. The excitation light control means controls the excitation light outputting means, based on the control signal. The multiplexing means multiplexes the excitation light and each of the beams of the WDM signal light, and outputs the respective multiplexed beams of light to the optical fiber.

A method for determining an optical signal power change, wherein the method includes: A first optical signal that includes a plurality of wavelength signals is obtained, where the plurality of wavelength signals are distributed in a plurality of bands. Then, an optical power of each band and a center wavelength signal of each band are detected, and a preset single-wavelength transmit power and a preset coefficient are obtained. Next, an equivalent quantity N of equivalent wavelength signals is determined, and an equivalent wavelength signal corresponding to the first optical signal is determined. Further, a target power that is used to compensate for a first power change value of the first optical signal in transmission over an optical fiber is determined based on the preset coefficient, the equivalent wavelength signal, the equivalent quantity, and the preset single-wavelength transmit power.

A method for determining an optical signal power change, wherein the method includes: A first optical signal that includes a plurality of wavelength signals is obtained, where the plurality of wavelength signals are distributed in a plurality of bands. Then, an optical power of each band and a center wavelength signal of each band are detected, and a preset single-wavelength transmit power and a preset coefficient are obtained. Next, an equivalent quantity N of equivalent wavelength signals is determined, and an equivalent wavelength signal corresponding to the first optical signal is determined. Further, a target power that is used to compensate for a first power change value of the first optical signal in transmission over an optical fiber is determined based on the preset coefficient, the equivalent wavelength signal, the equivalent quantity, and the preset single-wavelength transmit power.

A submarine optical communication system control device (1) according to the present invention includes: a light intensity distribution determination device (2) configured to determine an optimum distribution of signal light intensity of each optical path for each allocated frequency; a light intensity distribution measuring device (3) configured to measure a light intensity distribution of an optical path after transmission through a submarine cable transmission line; an equalization setting calculation unit (4) configured to calculate a gain equalization setting for compensating for the difference between an optimum distribution in the light intensity distribution determination device and a measured distribution in the light intensity distribution measuring device; and a variable gain equalizer (5) configured to compensate for a light intensity distribution of an optical path to the optimum distribution, based on a gain equalization setting in the equalization setting calculation unit.

An optical system including a forward and a backward Raman pump module positioned along a transmission fiber; a noise matrix computing module configured to: determine, for first gains of the optical signal, a first noise associated with the first gain of the forward Raman pump; determine, for second gains of the optical signal, a second noise associated with the second gain of the backward Raman pump module; generate a noise matrix based on i) the first noise for each first gain of the forward Raman pump module and ii) the second noise for each second gain of the backward Raman pump module; identify a span loss of the optical signal as the optical signal is transmitted along the transmission fiber; identify a combination of a particular first gain of the forward Raman pump module and a particular second gain of the backward Raman pump module.

An optical repeater is a C+L-band repeater inserted between a first transmission path fiber and a second transmission path fiber. The optical repeater includes: a first optical fiber amplifier inserted in a first line, for amplifying a C-band signal; a second optical fiber amplifier inserted in a second line, for amplifying an L-band signal; a third optical fiber amplifier inserted in a third line, for amplifying a C-band signal; a fourth optical fiber amplifier inserted in a fourth line, for amplifying an L-band signal; and a first loopback means provided between an input to the first optical fiber amplifier or an output from the first optical fiber amplifier and an input to the third optical fiber amplifier or an output from the third optical fiber amplifier.

A submarine optical communication system control device (1) according to the present invention includes: a light intensity distribution determination device (2) configured to determine an optimum distribution of signal light intensity of each optical path for each allocated frequency; a light intensity distribution measuring device (3) configured to measure a light intensity distribution of an optical path after transmission through a submarine cable transmission line; an equalization setting calculation unit (4) configured to calculate a gain equalization setting for compensating for the difference between an optimum distribution in the light intensity distribution determination device and a measured distribution in the light intensity distribution measuring device; and a variable gain equalizer (5) configured to compensate for a light intensity distribution of an optical path to the optimum distribution, based on a gain equalization setting in the equalization setting calculation unit.

An excitation light source apparatus capable of assuring an excellent optical transmission characteristic even at occurrence of a gain tilt is provided. The excitation light source apparatus comprises an excitation light outputting means, a control signal detection means, a control signal detection means, an excitation light control means, and a multiplexing means. The excitation light outputting means outputs excitation light for Raman amplification. The control signal detection means detects a control signal of the excitation light outputting means from beams of WDM signal light transmitted through optical fibers in an upstream direction and a downstream direction. The excitation light control means controls the excitation light outputting means, based on the control signal. The multiplexing means multiplexes the excitation light and each of the beams of the WDM signal light, and outputs the respective multiplexed beams of light to the optical fiber.

Disclosed herein are methods and systems for optimizing signal quality in an optical network having two or more hub nodes continuously outputting optical signals to a plurality of leaf nodes. Each of the plurality of leaf nodes may receive a combined optical signal from the hub nodes and determine an optical power and a signal quality of one optical subcarrier group and send a correction signal to the hub node that sent the subcarrier group. The hub nodes may send a power optimization request comprising the optical power and signal quality of each subcarrier group to a network controller. The network controller may use the optical power and signal quality to determine a power update for an optical power of the subcarrier group(s) and send the power update to the hub node transmitting the subcarrier group. The hub node may adjust the optical power based on the power update.