An optical fiber device may include a unitary core including a primary section and a secondary section, wherein at least a portion of the secondary section is offset from a center of the unitary core, wherein the unitary core twists about an optical axis of the optical fiber device along a length of the optical fiber device, and wherein a refractive index of the primary section is greater than a refractive index of the secondary section; and a cladding surrounding the unitary core.

An optical fiber laser device generates laser light by using an optical amplifying fiber as an amplification medium in a laser oscillator and includes: an optical outputting fiber configured to emit laser light to an outside; a return-light-attenuating portion configured to perform an attenuation process to return light propagating through at least the optical outputting fiber in a reverse direction of the laser light; a thermal conversion unit provided at the return-light-attenuating portion and configured to convert the return light into heat; a temperature-monitoring device configured to measure an increase in a temperature, of the return-light-attenuating portion, caused by the heat converted by the thermal conversion unit; and a control unit configured to decrease or stop an output of the laser light when the temperature measured by the temperature-monitoring device becomes a predetermined threshold temperature or higher.

A free space optical communication system transmits and receives optical signals in a colorless manner using an optical circulator. The system installs the optical circulator with a single mode (SM) fiber at port 1, a double clad (DC) fiber at port 2, and a multimode (MM) fiber at port 3. The system injects a first optical signal into a core of the SM fiber. The system then routes the first optical signal at port 1, using the optical circulator, into a SM core of the DC fiber via Port 2. Further, the system injects a second optical signal into a first cladding of the DC fiber. The system then routes the second optical signal at port 2, using the optical circulator, into the MM fiber via Port 3.

An optical system includes a light guide for guiding an image light ray which is output from a display element and forms an image, to a field of view region of a user as a virtual image. The light guide includes a body having a plate shape, and an in-coupling region and an exit region which are formed in the body. The in-coupling region allows the image light ray incident from the display element to propagate within the body. The exit region allows the image light ray propagating within the body to emerge from the body toward the field of view region. The in-coupling region includes a periodic structure constituted by recessed or protruded parts in relation to a thickness direction of the body which are arranged to have periodicity in three predetermined directions intersecting each other within a predetermined plane perpendicular to the thickness direction of the body.

A waveguide assembly comprising a first waveguide, and a second waveguide designed as a dielectric multimodal waveguide, and a waveguide transition for transmitting an electromagnetic wave between the first waveguide and the second waveguide, the waveguide transition having a dielectric waveguide piece which is between the first waveguide and the second waveguide. The dielectric waveguide piece is capable of guiding a smaller mode number than the second waveguide, at least in a front section, facing the first waveguide.

A patch cord for transmitting between a single mode fiber (SMF) and a multi-mode fiber (MMFs) has a MMF, SMF, and a photonic crystal fiber (PCF) with a hollow core placed between the SMF and MMF. A mode field diameter (MFD) of the PCF hollow core section is in the range of 16 to 19 microns, the length of the PCF is between 1 cm to 10 cm, the MMF has 502 microns core diameter, the SMF has a 6-9 microns core diameter, and the coupling between the PCF mode to the MMF fundamental mode is maximized.

An optical fiber amplifier comprising a first optical fiber, a second optical fiber, a third optical fiber, and an excitation light source, is disclosed. Each optical fiber has cores and a cladding surrounding the cores. The third optical fiber transmits excitation light used for signal amplification in the second optical fiber. A rare-earth element is doped to the second optical fiber that amplifies an optical signal propagating therein by the excitation light. The third optical fiber includes a reduced-diameter portion. A distance between the cores of the third optical fiber in the reduced-diameter portion is shorter than a distance between the cores in other portion of the third optical fiber, and the excitation light entering from the excitation light source to one of the cores of the third optical fiber is mode-coupled with another core of the third optical fiber to distribute the excitation light in the reduced-diameter portion.

Disclosed is an annular-beam coupling system enabling reduction of noise generated from a core of a double-clad fiber. The disclosed annular-beam coupling system comprises: a fiber for transmitting light of a light source; a collimator for receiving the light outputted from the fiber and forming a parallel beam of a circular shape; an annular-beam generation unit for converting the parallel beam into an annular beam; and a double-clad fiber having the annular beam coupled to a cladding region thereof.

An optical connection component includes a holding member that includes a front end surface, a rear end surface opposite to the front end surface, a reference surface, a pair of first guide holes provided on the front end surface, and a pair of second guide holes provided on the rear end surface; and an optical waveguide member that includes a front surface, a rear surface opposite to the front surface, a lower surface, and a plurality of optical waveguides extending from the front surface to the rear surface. Arrangement of first ends of the plurality of optical waveguides on the front surface and arrangement of second ends of the plurality of optical waveguides on the rear surface are different from each other. The optical waveguide member is held by the holding member such that the lower surface and the reference surface come into contact with each other.

A device of collimation of a light beam including a monomode waveguide, a first element of collimation of the light beam parallel to a first plane and a second element of collimation of the light beam parallel to a second plane, the first collimation element coupling the waveguide to the second collimation element.