An optical fiber includes: a core portion made of glass; and a cladding portion made of glass, having a refractive index lower than the refractive index of the core portion, and positioned on an outer periphery of the core portion. Further, the cladding portion has an outer diameter smaller than 100 μm, and the core portion has a relative refractive-index difference of 0.32% to 0.40% with respect to the cladding portion.

An optical fiber array includes a plurality of single-core fibers each having a core and a cladding and each having, in a distal end surface thereof, a beam expanding portion capable of expanding a mode field diameter (MFD) of light propagating in the core, and a ferrule having an optical fiber holding hole into which the plurality of single-core fibers are inserted, and an end surface in which the optical fiber holding hole opens. A cladding diameter of each of single-core fiber in the beam expanding portion decreases toward the distal end surface. The optical fiber holding hole has a tapered portion whose inner diameter decreases toward the end surface and against which the distal end surfaces abut.

The present disclosure relates to an optical fiber or the like that can be adapted to an optical transceiver for a short wavelength band of 850 nm or more and 1060 nm or less while maintaining compatibility with an SMF of the related art. An optical fiber of one embodiment includes a core, a cladding, and a resin coating, and has a mode field diameter of 8.2 .Math.m or more and 9.6 .Math.m or less at a wavelength of 1310 nm, a cable cutoff wavelength of an LP11 mode of 1060 nm or more and 1260 nm or less, and a cable cutoff wavelength of an LP02 mode of 1060 nm or less.

A method of processing by controlling one or more beam characteristics of an optical beam may include: launching the optical beam into a first length of fiber having a first refractive-index profile (RIP); coupling the optical beam from the first length of fiber into a second length of fiber having a second RIP and one or more confinement regions; modifying the one or more beam characteristics of the optical beam in the first length of fiber, in the second length of fiber, or in the first and second lengths of fiber; confining the modified one or more beam characteristics of the optical beam within the one or more confinement regions of the second length of fiber; and/or generating an output beam, having the modified one or more beam characteristics of the optical beam, from the second length of fiber. The first RIP may differ from the second RIP.

An optical fiber array includes a plurality of single-core fibers each having a core and a cladding and each having, in a distal end surface thereof, a beam expanding portion capable of expanding a mode field diameter (MFD) of light propagating in the core, and a ferrule having an optical fiber holding hole into which the plurality of single-core fibers are inserted, and an end surface in which the optical fiber holding hole opens. A cladding diameter of each of single-core fiber in the beam expanding portion decreases toward the distal end surface. The optical fiber holding hole has a tapered portion whose inner diameter decreases toward the end surface and against which the distal end surfaces abut.

An optical fiber includes: a central core portion; an intermediate layer formed around an outer circumference of the central core portion; a trench layer formed around an outer circumference of the intermediate layer; and a cladding portion formed around an outer circumference of the trench layer. Further, when, relative to the cladding portion, a relative refractive-index difference of the central core portion is Δ1, a relative refractive-index difference of the intermediate layer is Δ2, and a relative refractive-index difference of the trench layer is Δ3, relationships Δ1>Δ2>Δ3 and 0>Δ3 are satisfied and Δ1 is equal to or greater than 0.34% and equal to or less than 0.40%, |Δ3| is equal to or less than 0.25%, and Δ1×|Δ3| is less than 0.08%.sup.2.

An electronic device may have a display, a display cover layer, and a sheet-packed coherent fiber bundle. The coherent fiber bundle may have an input surface that receives an image from the display and a corresponding output surface to which the image is transported. The coherent fiber bundle may be placed between the display and the display cover layer and mounted to a housing. The coherent fiber bundle may have fiber cores with bends that help conceal the housing from view and make the display appear borderless. The coherent fiber bundle has filaments formed from elongated strands of binder in which multiple fiber cores are embedded. Sheets of filaments are stacked and fused together to form the coherent fiber bundle. By aligning and fusing the sheets with respect to each other the filaments are packed with a desired density and uniformity.

The present disclosure provides an optical fibre (100). The optical fibre (100) includes a glass core (102), a trench region (106) and a cladding (108). The trench region (106) has a trench curve parameter α.sub.trench in range of 5 to 8. The optical fibre (100) has a mode field diameter in range of 8.7 micrometers to 9.7 micrometers at wavelength of 1310 nanometer.

As described herein, a mode field adapter (MFA) comprises a first fiber including a core associated with a fundamental mode field diameter and a cladding with a diameter that decreases toward a waist. The MFA comprises a second fiber including a core associated with a fundamental mode field diameter that matches the fundamental mode field of the first fiber at the waist and a cladding with a diameter that matches the diameter of the cladding of the first fiber at the waist and increases from the waist of the second fiber. The cladding of the first fiber may be adiabatically etched such that a core-to-cladding ratio of the first fiber changes over a length of the first fiber, and the core and the cladding of the second fiber may be adiabatically tapered such that a core-to-cladding ratio of the second fiber is constant over a length of the second fiber.

An up-taper is applied by a mode adapter to increase a signal mode area prior to tapering and combining.