In some embodiments, a data center optical communications system includes: a transmitter comprising a light source, wherein the light source is configured to provide light; an optical fiber operably connected to said transmitter and configured to receive light from the light source, wherein the optical fiber has a length L of 50 km or greater; a receiver configured to receive light from the optical fiber, wherein the receiver includes a detector for detecting the light, wherein the system has a power consumption of 15 W or less

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.

An optical fiber sensor includes: a central core disposed at a center of an optical fiber; and an outer peripheral core that spirally surrounds the central core. The effective refractive index n.sub.e2 of the outer peripheral core is lower than the effective refractive index n.sub.e1 of the central core. A ratio between the effective refractive index n.sub.e2 and the effective refractive index n.sub.e1 matches a ratio between an optical path length of the central core and an optical path length of the outer peripheral core.

A fiber ring resonator having a relatively long loop of standard single-mode fiber with a short nanofiber segment. The evanescent mode of the nanofiber segment allows the cavity-enhanced field to interact with atoms in close proximity to the nanofiber surface.

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 made of silica glass includes a core having a maximum refractive index n1, a depressed portion surrounding the core and having an average refractive index n2, and cladding surrounding the depressed portion and having an average refractive index n3. In the optical fiber, n1>n3>n2. The optical fiber has a local maximum value of chromatic dispersion within a wavelength range of 1530 nm to 1610 nm, and the local maximum value is 2 ps/nm/km or greater and below 0 ps/nm/km.

An optical fiber sensor includes: a central core disposed at a center of an optical fiber; and an outer peripheral core that spirally surrounds the central core. The effective refractive index n.sub.e2 of the outer peripheral core is lower than the effective refractive index n.sub.e1 of the central core. A ratio between the effective refractive index n.sub.e2 and the effective refractive index n.sub.e1 matches a ratio between an optical path length of the central core and an optical path length of the outer peripheral core.

An optical fiber according to an embodiment comprises, as a structure suitable for large capacity transmission over a long haul, a core, a cladding having an outer diameter of 80 m or more and 130 m or less, a primary coating, and a secondary coating having elasticity higher than that of the primary coating and an outer diameter of 210 m or less. The optical fiber having the structure as described above has an MFD of 10 m or more at a wavelength of 1550 nm, a cable cutoff wavelength longer than 1260 nm, and a microbending loss of 0.6 dB/km or less at a wavelength of 1550 nm.

An optical fiber for efficient coupling of optical signals to photonic devices. The optical fiber includes a Cl doped tapered core region with a changing outer diameter and changing maximum core refractive index to provide improved coupling at wavelength of interest to photonic devices. The photonic devices may be, for example, silicon photonic devices with an operating wavelength at or near 1310 nm, or at or near 1550 nm.

In some embodiments, a data center optical communications system includes: a transmitter comprising a light source, wherein the light source is configured to provide light; an optical fiber operably connected to said transmitter and configured to receive light from the light source, wherein the optical fiber has a length L of 50 km or greater; a receiver configured to receive light from the optical fiber, wherein the receiver includes a detector for detecting the light, wherein the system has a power consumption of 15 W or less.