The production and new type of preforms are presented which yield, upon drawing, new, class of optical fibers, improved, speckle-free output optical fibers. Useful fibers, providing speckle-free, smooth output with flat top transmission of light from gaussian or few mode sources are produced from preforms introduced herein. The unique production of these improved preforms is also presented. The preforms, and thus the fibers produced in varying core dimensions from about 100 μm to above 1000 μm, are based on a structured silica section of mode mixing area adjacent to the inner core, or in the case of non-circular core, within the core. Plasma Vapor Deposition process is modified to achieve the structured sections in a well-controlled manner. The structured sections are composed of a number of pairs of layers, where a thin down-doped layer is alternated with a much thicker core material layer. The ratio of the thickness of the core layer to the thickness of the down-doped layer is about 3 to 25. The number of paired layers is typically between about 8 to 30-layer pairs. The effective NA of the structured section is dependent on the particulars of the structured silica section and of the individual down-doped layer. Both circular inner core examples and non-circular core examples are possible and are discussed, herein.

The production and new type of preforms are presented which yield, upon drawing, new, class of optical fibers, improved, speckle-free output optical fibers. Useful fibers, providing speckle-free, smooth output with flat top transmission of light from gaussian or few mode sources are produced from preforms introduced herein. The unique production of these improved preforms is also presented. The preforms, and thus the fibers produced in varying core dimensions from about 100 μm to above 1000 μm, are based on a structured silica section of mode mixing area adjacent to the inner core, or in the case of non-circular core, within the core. Plasma Vapor Deposition process is modified to achieve the structured sections in a well-controlled manner. The structured sections are composed of a number of pairs of layers, where a thin down-doped layer is alternated with a much thicker core material layer. The ratio of the thickness of the core layer to the thickness of the down-doped layer is about 3 to 25. The number of paired layers is typically between about 8 to 30-layer pairs. The effective NA of the structured section is dependent on the particulars of the structured silica section and of the individual down-doped layer. Both circular inner core examples and non-circular core examples are possible and are discussed, herein.

Disclosed is an optical fiber-based divergence-limiting device for limiting divergence from a first maximum divergence of input light to a second maximum divergence of output light, in which the second maximum divergence is less than the first maximum divergence.

Some embodiments may include a packaged laser diode assembly, comprising: a length of optical fiber having a core and a polymer buffer in direct contact with the core, the length of optical fiber having a first section and a second section, the first section of the length of optical fiber including a tip of an input end of the optical fiber, wherein the polymer buffer covers only the second section of the first and second sections; one or more laser diodes to generate laser light; means for directing a beam derived from the laser light into the input end of the length of optical fiber; a light stripper attached to the core in the first section of the length of optical fiber. Other embodiments may be disclosed and/or claimed.

Various example embodiments relate to active optical fibers and devices comprising active optical fibers. A section of an active optical fiber may comprise an active core doped with at least one rare-earth element. The active core may have a first refractive index and be configured to support a single mode operation of an optical signal. The section of the active optical fiber may further comprise at least one cladding layer having a second refractive index. The second refractive index may be less than the first refractive index. Birefringence of the active core may be less than 10.sup.-5. Fiber lasers and power amplifiers comprising the section of the active optical fiber are also disclosed.

A bending detecting system includes a light guide, a first grating and a light detector. The light guide has elongated shape and is configured to guide an incident light in a propagating direction. The light guide includes a core and a cladding disposed around the core. The first grating is disposed in a boundary area, the boundary area including an outer surface of the core, and an adjacent area that is adjacent to the outer surface. The first grating includes a first periodic structure along the propagating direction with a first pitch, and is configured to generate a first diffracted light from the incident light. The light detector is configured to detect the first diffracted light from the first grating, and detect a bending of the light guide based upon an optical feature amount of the first diffracted light.

A cladding light stripper may include a double-clad optical fiber having a core for guiding signal light, an inner cladding surrounding the core, and an outer cladding surrounding the inner cladding. The optical fiber may include a stripped portion forming an exposed section. The exposed section may include a plurality of spirally-arranged transversal notches disposed along the optical fiber to enable light to escape the inner cladding upon impinging on the plurality of notches. A circumferential segment of the optical fiber may include a single notch of the plurality of notches. Each of the plurality of notches may have a depth of only a partial distance to the core.

A cladding light stripper may include a double-clad optical fiber having a core for guiding signal light, an inner cladding surrounding the core, and an outer cladding surrounding the inner cladding. The optical fiber may include a stripped portion forming an exposed section. The exposed section may include a plurality of spirally-arranged transversal notches disposed along the optical fiber to enable light to escape the inner cladding upon impinging on the plurality of notches. A circumferential segment of the optical fiber may include a single notch of the plurality of notches. Each of the plurality of notches may have a depth of only a partial distance to the core.

Provided is a micro optical circuit including a first micro optical waveguide and a second micro optical waveguide with a boundary face therebetween, in which the height of the first and second micro optical waveguides is different from each other, and the side faces of the first micro optical waveguide are connected to the side faces of the second micro optical waveguide at first and second connection points in a plan view. An intersection between the boundary face and the center line equidistant from the two side faces of the second micro optical waveguide is present in a region between a first straight line and a second straight line in a plan view, the first straight line passing through the first and second connection points, the second straight line crossing the second micro optical waveguide so as not to cross the first micro optical waveguide.

Provided is a micro optical circuit including a first micro optical waveguide and a second micro optical waveguide with a boundary face therebetween, in which the height of the first and second micro optical waveguides is different from each other, and the side faces of the first micro optical waveguide are connected to the side faces of the second micro optical waveguide at first and second connection points in a plan view. An intersection between the boundary face and the center line equidistant from the two side faces of the second micro optical waveguide is present in a region between a first straight line and a second straight line in a plan view, the first straight line passing through the first and second connection points, the second straight line crossing the second micro optical waveguide so as not to cross the first micro optical waveguide.