An apparatus for combining optical radiation, wherein the apparatus comprises a bundle of input optical fibers formed of glass, a taper, and an output optical fiber, wherein the taper is fused to the output optical fiber; and the apparatus comprises at least one cladding mode stripper to strip out higher order modes that would otherwise degrade a polymer coating on at least one of the input optical fibers and the output optical fiber.

A fiber coupler is provided, which includes a tubular enveloping structure and several optical fibers arranged in the enveloping structure, each of which has a fiber core and a fiber cladding surrounding same, in order to conduct laser radiation, and each of which extends from the first as far as the second end of the enveloping structure. The enveloping structure includes a tapering section which is tapered in a first direction from the first as far as the second end. In the tapering section, both a first ratio of the diameter of the fiber core to the diameter of the fiber cladding and also a second ratio of the diameter of the mode field of the laser radiation conducted in the optical fiber to the diameter of the fiber core, increases in the first direction for each optical fiber.

There is described an optical fiber coupler in which at least one fiber is a multiple-clad fiber, containing a single-mode core supporting a single guiding mode and an inner multi-mode cladding guiding multiple modes. The multiple-clad fiber is fused with a second fiber of a different etendue to create an optical fiber coupler having an enhanced multi-mode signal transmission.

A bundle structure is obtained by arranging optical fibers having equal diameters in a close-packed arrangement around the outer circumference of a center optical fiber. The optical fibers are signal light optical fibers that transmit signal lights. The optical fiber is a pump light optical fiber that transmits pump light. The number of optical fibers is equal to the number of cores in the multi-core fiber. The bundle structure and the multi-core fiber are connected to one another by adhering or fusing. The cores and the cores are optically connected, and the core and the cladding are optically connected. When connecting, the mode field diameter of the cores and the cores are substantially equivalent. In addition, the outer diameter (diameter of circumscribed circle including optical fibers) of the bundle structure is set so as not to be greater than the outer diameter of the multi-core fiber.

A laser interference lithography device using all-fiber-optic components is disclosed. In the said all-fiber laser interference lithography device, an input coupling fiber receives the coherent laser beam from a laser source and sends it to an optical fiber splitter. The optical fiber splitter splits the input laser beam into at least two sub-beams and outputs the multiple sub-beams through multiple output optical fiber. Adjustable fiber holders, each carrying one output fiber, tune the position and angle of output optical fibers to achieve desired interference patterns on a substrate

The disclosed embodiments show a fused fiber combiner with sensors that are strategically located at various locations, thereby permitting performance monitoring of the fused fiber combiner. Additionally, the disclosed embodiments show various processes for determining causes of any performance degradations.

An optical combiner includes input optical fibers and a bridge fiber. The input optical fibers each includes a core, a first cladding surrounding the core and having a refractive index lower than a refractive index of the core, a second cladding surrounding the first cladding and having a refractive index lower than the refractive index of the first cladding, and a third cladding surrounding the second cladding and having a refractive index lower than the refractive index of the second cladding. The bridge fiber has an incident surface optically coupled to the core of each of the input optical fibers and an emitting surface that emits light obtained by multiplexing the light incident from each of the input optical fibers.

An apparatus includes an optical fiber bundle that includes a plurality of input optical fibers and a tapered segment. One end of each of the input optical fibers physically connects to a wide end of the tapered segment. The optical fiber bundle is an integral unit. The input optical fibers are multimode optical fibers. Fundamental optical propagating modes of at least two of the multimode optical fibers have different velocities.

An optical combiner (25), comprising a bundle of input fibers (24) spliced to an output fiber (26), the output fiber having a cladding and at least one high-index portion within the cladding, such that the high index portion has a diameter substantially equal to or less than the outer diameter of the input fiber bundle at the splice point.

Optical fiber combiner includes a plurality of input optical fibers having a core and a cladding surrounding the core, a bridge fiber having a portion that transmits a light beam entered from each of the input optical fibers, and a glass member fusion-spliced to an end face of the cladding and to a first end face of the bridge fiber. The end portions of the claddings of the plurality of input optical fibers are bundled on at least a first end face side, with the adjacent side surfaces of the claddings being in contact with each other. The glass member has an outer diameter greater than the diameter of the core and smaller than the outer diameter of the cladding. The adjacent glass members are in a non-fusion-spliced state.