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.

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.

Optical amplifier assembly for spatial division multiplexing (SDM) optical communication systems. Each optical amplifier assembly includes a single pump assembly configured for causing amplification of signals traveling on separate fiber paths in different directions. Each fiber path includes a plurality of spatial dimensions. The single pump assembly includes a plurality of pump sources to provide redundancy and the optical amplifier assembly further includes splitters for splitting outputs of the pump sources to amplifiers coupled to the different spatial dimensions. Different modulation formats may be used on the different spatial dimensions with different pump power being provided to each of the modulation formats. Amplifiers with complementary outputs may be coupled to average out gain deviations.

A bi-directional coupler assembly includes a first port for connecting to one of an input forward path RF signal line and an output forward path RF signal line. A second port connects to the other of the input forward path RF signal line and the output forward path RF signal line. A relay is connected between the ports and to at least one directional coupler. In a first state of the relay, an input forward path RF signal delivered from the input forward path RF signal line and through the first port is directed through the at least one directional coupler in a first direction. In a second state of the relay, an input forward path RF signal delivered from the input forward path RF signal line and through the second port is directed through the at least one directional coupler in said first direction.

A bi-directional coupler assembly includes a first port for connecting to one of an input forward path RF signal line and an output forward path RF signal line. A second port connects to the other of the input forward path RF signal line and the output forward path RF signal line. A relay is connected between the ports and to at least one directional coupler. In a first state of the relay, an input forward path RF signal delivered from the input forward path RF signal line and through the first port is directed through the at least one directional coupler in a first direction. In a second state of the relay, an input forward path RF signal delivered from the input forward path RF signal line and through the second port is directed through the at least one directional coupler in said first direction.

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 colorless mux/demux cable assembly, including a first fiber optic cable, a second fiber optic cable, and a main body that includes an N:1 optical combiner and a 1:N optical splitter. The N:1 optical combiner is configured to combine individual optical signals received by each of N input fibers of the second fiber optic cable and provide a combined output signal to an output fiber of the first fiber optic cable. The 1:N optical splitter is configured to split a combined input optical signal (having N wavelength channels) received via an input fiber of the first fiber optic cable and provide a split output signal comprising each of the N wavelength channels to each of N output fibers of the second fiber optic cable.

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 system includes (i) an optical link including multiple spans of optical fiber and multiple network elements and (ii) at least one switch configured to reverse a direction that at least one of the network elements communicates over the optical link.

An optical relay device includes a substrate, and a first transmission module and a second transmission module that are provided on the substrate. The substrate has a first side and a second side opposite to each other in a direction perpendicular to the substrate. The first transmission module and the second transmission module both include at least one light emitting unit and at least one light receiving unit. The light emitting unit includes at least one light emitter. The light receiving unit includes at least one light receiver. Optical paths of light receiving units and optical paths of light emitting units are provided in one-to-one correspondence in the direction perpendicular to the substrate, and the light receiving unit and the light emitting unit that are corresponding to each other form a signal transmission channel.