Provided is an optical fiber coupler capable of suppressing variation of polarization state of light passing through a coupler portion. The optical fiber coupler includes: a substrate having a groove; a coupler portion which is inserted into the groove and to which a middle portion of each of optical fibers is joined; and an adhesive for bonding the coupler portion to the substrate. Shore D hardness of the adhesive is 10 to 35. By setting the Shore D hardness of the adhesive to 10 to 35, it is possible to suppress the variation of the polarization state of the light passing through the coupler portion.

A photonic lantern couples light from several fibers or fiber cores into one or more fibers or fiber cores. Photonic lanterns are often used to combine several lower-power beams into a single higher-power beam. They can also be used to couple light from multi-core fibers into single-mode, multi-mode, or other multi-core fibers. By modulating the phases of the input beams, the light can be switched from output to outputfor example, between output cores of a multi-core output fiber. If desired, the beams can also be amplified using an active fiber in or coupled to the photonic lantern. A first photonic lantern couples signal light and pump light into the core and cladding, respectively, of an active multi-mode or multi-core fiber. And the active multi-mode or multi-core fiber couples amplified signal light into output fiber(s) via a second photonic lantern.

Advantageously, at least one embodiment of the present disclosure comprises a polarization maintaining PROFA (PM-PROFA) coupler in which the polarization axes of the individual vanishing core waveguides thereof are oriented or aligned without the need to adjust the orientation of each individual VC waveguide.

A depolarizer for a broadband optical source to split the source beam by power, not by polarization state, and route the components into respective light paths. A polarization rotator arranged in one of the light paths rotates the polarization state of that beam component to make it orthogonal to that of the other. The components are then recombined by a combiner and output. A variable optical attenuator is arranged in one of the light paths, which during operation is adjusted by a controller to maintain power equalization between the light paths and hence depolarization performance. The controller receives power measurements from the light paths and from after the combiner via respective sensors. With this feedforward design reminiscent of a Mach-Zehnder interferometer the light from a light source which generates highly polarized light can be depolarized in theory with zero insertion loss and in practice with losses of about 1 dB.

Advantageously, at least one embodiment of the present disclosure comprises a polarization maintaining PROFA (PM-PROFA) coupler in which the polarization axes of the individual vanishing core waveguides thereof are oriented or aligned without the need to adjust the orientation of each individual VC waveguide.

An optical transceiver that installs an optical modulator with the Mach-Zehnder type and made of primarily semiconductor materials, and an Erbium Doped Fiber Amplifier (EDFA) is disclosed. The EDFA and the MZ modulator, in addition to a wavelength tunable laser diode, an intelligent coherent receiver, and a polarization maintaining splitter, are installed within a compact case following the standard of CFP2.

A system and method includes a laser to create a control laser signal and a laser to create a probe laser signal. A resonator creates an acoustic signal adjacent the control laser signal and the probe laser signal. A resulting coherent interaction between the control laser signal and the probe laser signal creates a Brillouin scattering induced transparency in one direction and maintains opacity in an opposite direction.