An optical receiver module that receives a wavelength-multiplexed optical signal is disclosed. The optical receiver module includes a first lens, an optical de-multiplexer, second lenses, and photodiodes. The first lens forms a beam waist of the wavelength-multiplexed optical signal output therefrom. The optical de-multiplexer de-multiplexes the wavelength-multiplexed optical signal into optical signals depending on wavelengths thereof and is installed so as to make optical paths for respective optical signals different from each other. The second lenses concentrate the optical signals onto the respective photodiodes. In the optical receiver module, the beam waist of the wavelength-multiplexed optical signal is set in a halfway between a longest path and a shortest path from the first lens to the second lenses.

A bidirectional optical device includes a first optical component, wherein a portion of a first interface of the first optical component has a reflector coating, wherein a second interface of the first optical component has an optical coating, and wherein the first optical component includes an internal splitting interface disposed between the first interface and the second interface, and a second optical component including a reflector aligned to the second interface of the first optical component, wherein the first optical component and the second optical component comprise an unbalanced Mach-Zehnder (MZ) interferometer.

A splitter includes an optical input section, N optical branch sections, and at least (N?1) optical filter structures. Each optical filter structure reflects an optical signal of one wavelength. The at least (N?1) optical filter structures include a special optical filter structure and at least (N?3) common optical filter structures, and a wavelength of an optical signal reflected by each of the common optical filter structures is a common wavelength. A wavelength of an optical signal reflected by a first/second special optical filter structure is a first/second special wavelength. At least (N?3) common wavelengths constitute an arithmetic sequence, a difference between the first special wavelength and a largest common wavelength is greater than a tolerance of the arithmetic sequence, and a difference between the second special wavelength and a smallest common wavelength is greater than the tolerance of the arithmetic sequence.

A wavelength conversion apparatus includes: a first demultiplexer wavelength-separating an optical signal having wavelengths of a first band wavelength-multiplexed into n drop signals acquired by wavelength-multiplexing optical signals of predetermined wavelengths and a through signal acquired by wavelength-multiplexing an optical signal of a wavelength being not a target of wavelength conversion; a second demultiplexer demultiplexing optical signals of the predetermined wavelengths included in the n drop signals into optical signals; n wavelength converters wavelength-converting first optical signals of wavelengths included in the optical signals into second optical signals of the second band; n first multiplexers multiplexing the wavelength-converted second optical signals, and outputting n third optical signals; and a multiplexing unit multiplexing and outputting the n third optical signals, an optical signal acquired by wavelength-multiplexing wavelengths of a second band previously wavelength-separated from the wavelength-multiplexed optical signal, and the through signal.

An optical signal transmission method and an apparatus are provided, to reduce processing complexity while maximizing bandwidth utilization. An OPUk multiplexing frame with a bit rate greater than 1.25 Gbps is constructed by using a structure of an OPU0 multiplexing frame, so that the structure of the OPU0 multiplexing frame can be reused by a structure of the OPUk multiplexing frame, and the structure of the OPUk multiplexing frame is aligned with the structure of the OPU0 multiplexing frame. The OPUk multiplexing frame includes an integer multiple of OPUk frames, and a boundary of the OPUk multiplexing frame remains aligned with a boundary of the OPUk frame. According to this application, when mapping an OSU frame, an OTN device may map the OSU frame to the OPUk multiplexing frame based on the reused structure of the OPU0 multiplexing frame.

Provided is an optical amplifier, an optical relay and an optical communication system that can amplify signal light of a plurality of systems and that can realize a reduction in costs. This optical amplifier amplifies and outputs signal light of a plurality of systems, the amplifier including: a plurality of impurity-doped optical fiber amplification units; a plurality of excitation light sources; a plurality of excitation light demultiplexing units; a plurality of excitation light multiplexing/demultiplexing units; and a plurality of multiplexing units. The plurality of excitation light sources include at least a first excitation light source and a second excitation light source that are driven commonly by a first driving current, and a third excitation light source that is driven by a second driving current of a different system than the first driving current.

A communications system comprises a ground hub in a background area, aerial vehicles flying in a formation with slowly varying spacing between the aerial vehicles, and a user terminal in a region within a foreground area. The foreground area is spatially separate from the background area. The ground hub comprises a ground-based beam forming facility (GBBF) for receiving and transforming input signals into beam-formed signals, and a first antenna system coupled to the GBBF for transmitting concurrently the beam-formed signals in a first frequency band to respective aerial vehicles via respective background links. The aerial vehicles receive respectively the beam-formed signals via the background links and transmit respectively the beam-formed signals as respective signal beams covering at least the region within the foreground area in a second frequency band. The user terminal comprises a second antenna system for receiving concurrently the signal beams via foreground links to the aerial vehicles.

An optical relay device includes a WSS functioning as a wavelength selective switch capable of performing path switching in wavelength units and optical level adjustment for each of wavelengths and a control device that instructs, on the basis of a fluctuation amount of an optical level for each of the wavelengths of an optical signal output from the WSS and setting information indicating, for each of the wavelengths, whether optical level adjustment for the wavelengths of the optical signal is enabled, the WSS to perform a setting change of an optical level adjustment amount of the optical signal.

Free-space communication systems and methods are provided. The systems include a transmitter that combines multiple sets of radio-frequency-modulated optical carrier frequencies for transmission across free space using multiple transmission apertures. Different sets of signals are filtered to form single sideband signals. The different sets of single sideband signals are then combined to form dense wavelength division multiplexed signals. In addition, combined sets of signals of different polarizations can be combined. A receiver can include a single receive aperture.

A method is described in which a database is monitored. The database includes information specifying allocations of time periods in which a first optical carrier corresponding to a first optical channel will not be supplying encoded first data into output optical signals being transmitted from a first node to a second node. An idler carrier being amplified stimulated emission light having a frequency corresponding to the first optical channel is supplied into the output optical signals transmitted from the first node to the second node during the time periods in which the first optical carrier will not be supplying encoded first data into the output optical signals.