There are provided an optical receptacle having an optical fiber including a first portion on another end surface side, a third portion on one end surface side, and a second portion between the first portion and the third portion; a core diameter at the first portion is smaller than the core diameter at the third portion; the core diameter at the second portion increases from the first portion side toward the third portion side; a first elastic member is provided between the optical fiber and an inner wall of a through-hole; a holder holds the another end surface side of a fiber stub; and the sleeve holds the one end surface side of the fiber stub.

This disclosure relates to an MCF fiber being usable for short-haul O-band transmission, having a standard coating diameter in an MFD almost the same as that of a general-purpose SMF, being capable of splicing fibers without either a marker or a polarity, and including 12 cores usable for counter propagation. The MCF includes 12 cores and a common cladding, and the common cladding has an outer periphery with a circular cross-section, the 12 cores are arranged such that no adjacent relationship is established between cores each having an adjacent relationship with any core, and are arranged such that centers of the 12 cores are line symmetric with respect to an axis as a symmetry axis that intersects with the central axis and that passes through none of the centers of the 12 cores, and an arrangement of the centers of the 12 cores has rotational symmetry once.

Embodiments of the current disclosure include low moat volume single mode ultra-low loss optical fibers. In some embodiments, a single mode optical fiber includes a first core region; a second core region surrounding and directly adjacent to the first core region, wherein a volume V of the second core region is less than or equal to 14% Δμm.sup.2; a cladding region surrounding the core region; and wherein the optical fiber has a cable cutoff of less than 1260 nm, a mode field diameter at 1310 nm of 8.6 microns to 9.7 microns, a mode field diameter at 1550 nm of 9.9 microns to 11 microns, and an attenuation at 1550 nm of less than or equal to 0.17 dB/km.

A fiber optic sensor interrogation system with inbuilt passive power limiting capability based on stimulated Brillouin scattering that provides improved safety performance for use in explosive atmospheres.

The present disclosure provides an optical waveguide design of a fiber modified with a thin layer of epsilon-near-zero (ENZ) material. The design results in an excitation of a highly confined waveguide mode in the fiber near the wavelength where permittivity of thin layer approaches zero. Due to the high field confinement within thin layer, the ENZ mode can be characterized by a peak in modal loss of the hybrid waveguide. Results show that such in-fiber excitation of ENZ mode is due to the coupling of the guided fundamental core mode to the thin-film ENZ mode. The phase matching wavelength, where the coupling takes place, varies depending on the refractive index of the constituents. These ENZ nanostructured optical fibers have many potential applications, for example, in ENZ nonlinear and magneto-optics, as in-fiber wavelength-dependent filters, and as subwavelength fluid channel for optical and bio-photonic sensing.

An optical fiber includes a core, and a clad surrounding an outer circumference of the core, in which a first relative refractive index difference Δ1a is greater than 0, a second relative refractive index difference Δ1b is greater than 0, the first relative refractive index difference Δ1a is greater than the second relative refractive index difference Δ1b, the first relative refractive index difference Δ1a and the second relative refractive index difference Δ1b satisfy a relationship denoted by the following expression: 0.20≦(Δ1a−Δ1b)/Δ1a≦0.88, and a refractive index profile Δ of the core in an entire region of a section of 0≦r≦r1 as a function Δ(r) of a distance r from a center of the core in the radial direction is denoted by the following expression: Δ(r)=Δ1a−(Δ1a−Δ1b)r/r1.

Embodiments of the current disclosure include low moat volume single mode ultra-low loss optical fibers. In some embodiments, a single mode optical fiber includes a first core region; a second core region surrounding and directly adjacent to the first core region, wherein a volume V of the second core region is less than or equal to 14% Δμm.sup.2; a cladding region surrounding the core region; and wherein the optical fiber has a cable cutoff of less than 1260 nm, a mode field diameter at 1310 nm of 8.6 microns to 9.7 microns, a mode field diameter at 1550 nm of 9.9 microns to 11 microns, and an attenuation at 1550 nm of less than or equal to 0.17 dB/km.

The present invention is to provide a multi-core optical fiber that can expand its transmission wavelength band, and extend its transmission distance by reducing crosstalk, and also provide a method for designing the multi-core optical fiber. A multi-core optical fiber according to the present invention includes: four cores that are arranged in a square lattice pattern in a longitudinal direction; and a cladding region that is formed around the outer peripheral portions of the cores and has a lower refractive index than the cores, the absolute value of the relative refractive index difference between the cores and the cladding region being represented by Δ. In the multi-core optical fiber, the diameter of the cladding region is 125 ± 1 .Math.m, the cutoff wavelength is 1.45 .Math.m or shorter, the mode field diameter MFD at a wavelength of 1.55 .Math.m is 9.5 to 10.0 .Math.m, the bending loss at a wavelength of 1.625 .Math.m and with a bending radius of 30 mm is 0.1 dB/100 turns or smaller, and the inter-core crosstalk at the wavelength of 1.625 .Math.m is -47 dB/km or smaller.

The present disclosure provides an optical waveguide design of a fiber modified with a thin layer of epsilon-near-zero (ENZ) material. The design results in an excitation of a highly confined waveguide mode in the fiber near the wavelength where permittivity of thin layer approaches zero. Due to the high field confinement within thin layer, the ENZ mode can be characterized by a peak in modal loss of the hybrid waveguide. Results show that such in-fiber excitation of ENZ mode is due to the coupling of the guided fundamental core mode to the thin-film ENZ mode. The phase matching wavelength, where the coupling takes place, varies depending on the refractive index of the constituents. These ENZ nanostructured optical fibers have many potential applications, for example, in ENZ nonlinear and magneto-optics, as in-fiber wavelength-dependent filters, and as subwavelength fluid channel for optical and bio-photonic sensing.

This disclosure relates to an MCF fiber being usable for short-haul O-band transmission, having a standard coating diameter in an MFD almost the same as that of a general-purpose SMF, being capable of splicing fibers without either a marker or a polarity, and including 12 cores usable for counter propagation. The MCF includes 12 cores and a common cladding, and the common cladding has an outer periphery with a circular cross-section, the 12 cores are arranged such that no adjacent relationship is established between cores each having an adjacent relationship with any core, and are arranged such that centers of the 12 cores are line symmetric with respect to an axis as a symmetry axis that intersects with the central axis and that passes through none of the centers of the 12 cores, and an arrangement of the centers of the 12 cores has rotational symmetry once.