Provided is a signal loopback circuit which, in order to loop back a monitoring signal in a relay device for relaying optical signals of a plurality of wavelength bands, connects between a channel of first direction and a channel of second direction through which an optical signal of first wavelength band and an optical signal of second wavelength band are transmitted, wherein the signal loopback circuit is provided with a first coupler for branching the optical signal on the channel of first direction, a first filter for extracting at least one of a monitoring signal of first wavelength band and a monitoring signal of second wavelength band that are used in the channel of first direction from the optical signal branched by the first coupler, and a second coupler for causing the monitoring signal extracted by the first filter to be joined to the channel of the second direction.

Provided is a signal loopback circuit which, in order to loop back a monitoring signal in a relay device for relaying optical signals of a plurality of wavelength bands, connects between a channel of first direction and a channel of second direction through which an optical signal of first wavelength band and an optical signal of second wavelength band are transmitted, wherein the signal loopback circuit is provided with a first coupler for branching the optical signal on the channel of first direction, a first filter for extracting at least one of a monitoring signal of first wavelength band and a monitoring signal of second wavelength band that are used in the channel of first direction from the optical signal branched by the first coupler, and a second coupler for causing the monitoring signal extracted by the first filter to be joined to the channel of the second direction.

The systems, apparatuses and methods of the present invention set forth improvements to the problems of the current pairing or duplex paradigm, resulting in a dramatic increase in fiber transmission efficiency, accomplished explicitly by restructuring presently-aligned C-Band wavelengths into innovative DWDM transmit and receive formats, and through implementing photonic-wave changes, which directs Ethernet data flow onto new path adaptations. These improvements could reduce line haul expenses significantly, believed to reach a projected 50% less requirement/deployment of fiber strands. This saving would offer owner-operators substantial fiber strand cost reductions, affecting transportation rates of high-bandwidth digital payloads traversing over DWDM networks, and lower usage rates of cross-connections amid multiple equipment inter-exchanging throughout large data centers.

A relay transmission system includes a relay unit configured to relay uplink signals and downlink signals in the first and second communication systems, a time division duplex (TDD) information estimation unit configured to estimate a transmission period of network devices in the first communication system on the basis of the uplink or downlink signal of the first communication system that is relayed by the relay unit, a surplus bandwidth determination unit configured to determine a surplus bandwidth in which an uplink signal of the first communication system is not allocated to a relay target of the relay unit during the transmission period on the basis of the number of network devices and a maximum transmission capacity of the network devices, and a bandwidth allocation unit configured to allocate the uplink signal of the second communication system to the relay target of the relay unit in the surplus bandwidth.

A free-space optical communication link is proposed that utilizes phase-sensitive amplification of the received optical signal at the input to the receiver portion of the link. The transmitter component of the FSO link generates an idler signal that is transmitted through free space with the original data signal and used at the PSA in conjunction with a pump wave to impart gain onto the received information signal. The PSA performs four-wave mixing (FWM) of the data, idler and pump to create the amplified data signal. In one embodiment, the pump wave used to generate the idler at the transmitter is sent through free space with the information and idler signals and used by the PSA to perform amplification. Alternatively, the PSA may use a co-located pump laser, in combination with the received idler signal, to perform the phase-sensitive amplification process.

The systems, apparatuses and methods of the present invention set forth improvements to the problems of the current pairing or duplex paradigm, resulting in a dramatic increase in fiber transmission efficiency, accomplished explicitly by restructuring presently-aligned C-B and wavelengths into innovative DWDM transmit and receive formats, and through implementing photonic-wave changes, which directs Ethernet data flow onto new path adaptations. These improvements could reduce line haul expenses significantly, believed to reach a projected 50% less requirement/deployment of fiber strands. This saving would offer owner-operators substantial fiber strand cost reductions, affecting transportation rates of high-bandwidth digital payloads traversing over DWDM networks, and lower usage rates of cross-connections amid multiple equipment inter-exchanging throughout large data centers.

A free-space optical communication link is proposed that utilizes phase-sensitive amplification of the received optical signal at the input to the receiver portion of the link. The transmitter component of the FSO link generates an idler signal that is transmitted through free space with the original data signal and used at the PSA in conjunction with a pump wave to impart gain onto the received information signal. The PSA performs four-wave mixing (FWM) of the data, idler and pump to create the amplified data signal. In one embodiment, the pump wave used to generate the idler at the transmitter is sent through free space with the information and idler signals and used by the PSA to perform amplification. Alternatively, the PSA may use a co-located pump laser, in combination with the received idler signal, to perform the phase-sensitive amplification process.

The systems, apparatuses and methods of the present invention set forth improvements to the problems of the current pairing or duplex paradigm, resulting in a dramatic increase in fiber transmission efficiency, accomplished explicitly by restructuring presently-aligned C-Band wavelengths into innovative DWDM transmit and receive formats, and through implementing photonic-wave changes, which directs Ethernet data flow onto new path adaptations. These improvements could reduce line haul expenses significantly, believed to reach a projected 50% less requirement/deployment of fiber strands. This saving would offer owner-operators substantial fiber strand cost reductions, affecting transportation rates of high-bandwidth digital payloads traversing over DWDM networks, and lower usage rates of cross-connections amid multiple equipment inter-exchanging throughout large data centers.

Aspects of an optical communications network are described that include two or more optical fibers arranged to allow communication in the same or in opposite directions. The optical network includes a first optical amplifier coupled to the first optical fiber, a second optical amplifier coupled to the second optical fiber, and an optical coupler that allows excess optical power from the first optical fiber to be provided for amplification of signals traversing the second optical fiber. The disclosed systems and devices thus enable excess power from one channel to be utilized to enable amplification of signals traveling on a different channel.

Provided is a signal loopback circuit which, in order to loop back a monitoring signal in a relay device for relaying optical signals of a plurality of wavelength bands, connects between a channel of first direction and a channel of second direction through which an optical signal of first wavelength band and an optical signal of second wavelength band are transmitted, wherein the signal loopback circuit is provided with a first coupler for branching the optical signal on the channel of first direction, a first filter for extracting at least one of a monitoring signal of first wavelength band and a monitoring signal of second wavelength band that are used in the channel of first direction from the optical signal branched by the first coupler, and a second coupler for causing the monitoring signal extracted by the first filter to be joined to the channel of the second direction.