An object is to provide an optical amplifier capable of performing Raman amplification while suppressing power consumption and a size. A multicore fiber has a double clad structure. The double clad structure includes a plurality of cores thorough which an optical signal is transmitted and a clad includes the cores. A light source outputs a pump light used for amplifying the optical signal by stimulated Raman scattering in the multicore fiber. The pump light is generated by multiplexing multimode laser lights. A optical coupler couples the pump light into the clad of the multicore fiber.

The present invention relates to the technical field of optical communications, and relates to an optical amplification method and an amplifier, and in particular, to a self-adaptive wave band amplification method and an amplifier. The present invention consists of a master amplifying unit and a slave amplifying unit, and can autonomously detect the service signal wave band range of an optical transmission line, and according to the detection result, the two amplifying units do not need to perform scheduling or configuration from the level of network management, and perform direct interaction and action from the bottom layer to implement self-adaptive on, off and adjustment in real time. On one hand, power consumption is reduced, and energy is saved; and on the other hand, the performance is optimized, and an optimal optical amplification index is obtained.

An object of the present invention is to provide an optical transmission system capable of satisfying XT required by a modulation system even if there is an inter-core loss difference in an MCF.

An optical transmission system of the present invention includes a multi-core optical fiber having a plurality of core regions and having different losses between at least two cores, a forward excitation light source and a multiplexing unit for allowing Raman amplification excitation light to be incident on each core of the multi-core optical fiber in the same direction as signal light, and a backward excitation light source and a multiplexing unit for allowing Raman amplification excitation light to be incident on each core of the multi-core optical fiber in a direction opposite to the signal light, wherein an intensity ratio of the forward excitation light to the backward excitation light is controlled (a ratio of power of excitation light is set to a predetermined value) such that crosstalk (XT) fluctuation between cores is reduced.

An optically amplified repeater system includes optical transmission paths, a multi-channel optical amplifier, one or more Raman amplification pumping light sources, and a wavelength multiplexer. The multi-channel optical amplifier includes K simultaneous pumping light sources, N optical amplification media, and one or more optical couplers, and simultaneously amplifies, with the K simultaneous pumping light sources, light intensities of optical signals that pass through the N optical amplification media and propagate through the optical transmission paths. Light intensities of the wavelength band of the optical signals is Raman amplified by the Raman amplification pumping light. A light intensity of the Raman amplification pumping light output from the one or more Raman amplification pumping light sources is determined in accordance with characteristic differences between the optical signals passing through the optical transmission paths.

A method of providing in-line Raman amplification in an optical fiber sensing system, including the procedures of generating a probe light having a probe wavelength, transmitting the probe light into an optical fiber, generating at least one Raman pump light at a respective pump wavelength, the pump wavelength being shorter than the probe wavelength, generating at least one Raman seed light at a respective seed wavelength, the seed wavelength being between the pump and probe wavelengths, transmitting the Raman pump light into the optical fiber, transmitting the Raman seed light into the optical fiber and propagating the Raman pump light, the Raman seed light and the probe light along the optical fiber to achieve distributed Raman amplification of signal light produced by the probe light as it propagates along the optical fiber.

An unrepeatered transmission system includes a receiver coupled to a receive span; a transmitter coupled to the receive span; and a plurality of cascaded amplifiers in the receive span with dedicated fiber cores to supply one or more optical pumps from the receiver to each amplifier, wherein the plurality of cascaded amplifiers increase system reach by increasing the length of a back span in an unrepeatered link.

An optical amplifier assembly and a detection method capable of dynamically performing optical time-domain reflection detection. The detection method comprises obtaining signal light intensity detection signals from a first and second photodetectors and sending a control signal to an L-band Raman pump when it is determined that the signal light intensity in the second photodetector is lower than a first preset threshold, so that the L-band Raman pump enters into an optical time-domain reflection detection mode; sending a control signal to the L-band Raman pump when the signal light intensity in the second photodetector is greater than or equal the first preset threshold, so that the L-band Raman pump enters into an L-Band Raman optical fiber amplifier operation mode.

An apparatus includes multiple ports configured to be coupled to multiple optical fibers and to transmit first optical signals and receive second optical signals over the optical fibers. The apparatus also includes a signal source configured to generate a first additional optical signal for inclusion with the first optical signals. The apparatus further includes a signal detector configured to detect a second additional optical signal included with the second optical signals. In addition, the apparatus includes a switch configured to selectively couple the signal source to one of the ports. The switch is configured to couple the signal source to different ones of the ports in different configurations of the switch.

The present invention is directed to techniques and systems for extension of unrepeatered submarine fiber links to provide an increase in reach of unrepeatered fiber transmission. Both single channel unrepeatered systems and multiple channel unrepeatered systems can be used. The multiple channel unrepeatered systems can further employ nonlinearity compensation. The present invention is also directed to methods of signal transmission using the unrepeatered systems.

A low-noise amplifier includes a gain medium and two or more amplifier stages. Each amplifier stage includes an optical filter to pass all wavelengths of a respective input optical signal in a given propagation direction over the gain medium and reflect wavelengths above a respective threshold wavelength received in the opposite direction, and a respective Raman pump to inject a pump light centered at a wavelength lower than the threshold wavelength onto the gain medium for transmission in the given direction. A first amplifier stage outputs a first combined optical signal including all wavelengths of the respective input optical signal and a pump light injected by the respective Raman pump. The second amplifier stage receives the first combined optical signal as its input and outputs a second combined optical signal including all wavelengths of the first combined optical signal and a pump light injected by the respective Raman pump.