A Raman pumping device (10) for amplifying a data optical signal in a fiber optic transmission system, comprising first and second ports (12a, 12b) through which the data optical signal may respectively enter and exit the Raman pumping device (10), a Raman pump source (14) for generating a Raman pump signal, and at least one combiner (16) for combining the Raman pump signal with the data optical signal. The Raman pumping device (10) allows for selectively combining the Raman pump signal generated by the same Raman pump source (14), or at least parts of the same Raman pump source (14) codirectionally or counterdirectionally with the data optical signal.

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.

Systems and methods for calibrating a Raman amplifier in a photonic line system of an optical network are provided. A method, according to one implementation, includes the step of setting the gain of a plurality of pump lasers of a Raman amplifier to a safe level. For example, the pump lasers are configured to operate at different wavelengths. Also, the Raman amplifier is connected to a fiber span having a specific fiber-type. The safe can be defined as a level that keeps adverse intermodulation effects below a predetermined threshold regardless of the specific fiber-type. In addition, the method includes the step of increasing the gain of the pump lasers without prior knowledge of the specific fiber-type of the fiber span while keeping the adverse intermodulation effects below the predetermined threshold.

The present application 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 application is also directed to methods of signal transmission using the unrepeatered systems.

An optical communication system configured with a station-side apparatus and a plurality of subscriber-side apparatuses in a bus network topology includes an optical amplification unit installed on a station side, and a drop unit configured to branch an optical signal and excitation light, wherein the optical amplification unit includes an amplifier configured to amplify a downlink signal, and an excitation light output unit configured to output the excitation light for amplifying an uplink signal to a communication path, and the drop unit changes a branching ratio in accordance with a wavelength of the optical signal so that a transmission loss of the excitation light with respect to a trunk fiber is reduced.

An optical communication system having an optical transmission line, where a first section of the optical transmission line is connected to a first optical communication device; and a second section of the optical transmission line is connected to a second optical communication device. The optical communication system further includes: a Raman light source; an incident device connected to same end of the second section of the optical transmission line as the second optical communication device; and a separating device interconnecting the first section of the optical transmission line to the second section of the optical transmission line. The incident device causes excitation light output from the Raman light source to be incident to the second section of the optical transmission line and performs distributed Raman amplification on the optical signal; and the separating device separates the excitation light that is caused to be incident by the incident device.

An apparatus includes a remote optically pumped amplifier (ROPA). The ROPA includes a bypass filter configured to receive an optical signal and first pump power and to separate the optical signal and the first pump power. The ROPA also includes an amplifier configured to receive the optical signal from the bypass filter and to amplify the optical signal. The ROPA further includes an optical combiner/multiplexer configured to receive the first pump power from the bypass filter, receive at least second and third pump powers, combine at least two of the first, second and third pump powers, and provide different pump powers or combinations of pump powers to different locations within the ROPA to feed the amplifier.

A method and system for amplifying optical signals includes generating idler signals for input signals using an optical pump at a first non-linear element (NLE). An intermediate stage including a Raman amplifier performs pump amplification using the output from the first NLE along a single optical path. Optical power monitoring of the input signals may be used for power equalization. The intermediate stage may include a wavelength selective switch for a certain degree of phase modulation. The phase-sensitive amplified signal is generated at a second NLE using the optical pump. Optical power monitoring of the input signals may be used for power equalization and other control functions to achieve low-noise operation.

An optical amplification device includes a first Raman amplifier outputs a first excitation light to a transmission line in a same direction as a signal light, and a second Raman amplifier outputs a second excitation light to the transmission line in an opposite direction to the signal light. The first Raman amplifier includes a first detector detects a first power of a first transmitted light transmitted through a first optical filter. The second Raman amplifier includes a second detector detects second power of a second transmitted light transmitted through a second optical filter. The first Raman amplifier stops output of the first excitation light when the first power is higher than a threshold. The second Raman amplifier stops output of the second excitation light when the second power is reduced from power of the first excitation light transmitted through the second optical filter.

An excitation light source device includes: an excitation light source to generate the Raman excitation light; a light source controller to control an intensity of the Raman excitation light; an amplified spontaneous emission noise measurer to measure an intensity of amplified spontaneous emission noise caused by the Raman excitation light; and a transmission line abnormality analyzer to detect abnormality in the transmission line on a basis of a control state of the light source controller and a measurement result of the amplified spontaneous emission noise measurer. In a state where the abnormality is not detected, the light source controller controls the intensity of the Raman excitation light to gradually increase to a set value. In a state where the abnormality is detected, the light source controller controls the excitation light source to stop or reduce generation of the Raman excitation light.