An optical fiber cable comprising an optical fiber, and a jacketing layer including at least two or more layers of a jacketing inner layer and a jacketing outer layer formed in this order concentrically, wherein the jacketing layer comprises at least two or more layers of a jacketing inner layer and a jacketing outer layer formed in this order concentrically; a material constituting the jacketing inner layer is composed of a resin material having an oxygen permeability of 2.0 cc.Math.20 μm/(m.sup.2.Math.day.Math.atm) or less; a material constituting the jacketing outer layer comprises at least one selected from a polyolefin-based resin, a polybutylene terephthalate-based resin, and a fluorine-based resin containing no chlorine atom in its structure; and the following general formula (i) and (ii) are satisfied when an outer diameter of the optical fiber is denoted by A (μm), an outer diameter of the optical fiber cable is denoted by B (μm), and a thickness of the jacketing outer layer is denoted by c (μm):
900≤A≤1100  (i)
0.40≤2×c/(B−A)≤0.70  (ii).

A single mode optical fiber is provided that includes a core region having an outer radius r.sub.1 and a maximum relative refractive index Δ.sub.1max. The single mode optical fiber further includes a cladding region surrounding the core region, the cladding region includes a depressed-index cladding region, a relative refractive index Δ.sub.3 of the depressed-index cladding region increasing with increased radial position. The single mode optical fiber has a bend loss at 1550 nm for a 15 mm diameter mandrel of less than about 0.75 dB/turn, a bend loss at 1550 nm for a 20 mm diameter mandrel of less than about 0.2 dB/turn, and a bend loss at 1550 nm for a 30 mm diameter mandrel of less than 0.005 dB/turn. Additionally, the single mode optical fiber has a mode field diameter of 9.0 microns or greater at 1310 nm wavelength.

A power over fiber system includes an optical fiber cable. The optical fiber cable includes a core, a first cladding and a second cladding. The core transmits signal light. The first cladding is positioned in contact with periphery of the core and transmits feed light. The second cladding is positioned in contact with periphery of the first cladding. Radial refractive index distribution of the first cladding is distribution in which refractive index gradually decreases from a local maximum at an internal point toward points where the first cladding is in contact with the core and the second cladding, respectively. The internal point is away from the core and the second cladding. The refractive index of the core is higher than the refractive index of the first cladding at the point where the first cladding is in contact with the core.

The optical fiber according to the present invention includes, in a cross section of the optical fiber, one core region (11) and a cladding region (12) that is arranged on an outer periphery of the core region. The cladding region is a medium that has a lower refractive index than that of the core region and also has a smaller refractive index wavelength dispersion than that of the core region. The optical fiber has a solid core and therefore, allows more reduction in the Rayleigh scattering loss compared to an optical fiber having a hollow core. In addition, since the optical fiber adopts, for the cladding region, a medium that has a smaller refractive index wavelength dispersion than that of the core region, it allows a reduction in the wavelength dispersion of n.sub.eff.

An example of an optical fiber includes an attenuating cladding disposed around a first waveguide (e.g., a core) and a waveguide (e.g., a waveguide cladding) disposed around the attenuating cladding. An attenuating cladding may be a doped layer that may be doped with, for example, a dopant comprising metal. A first waveguide and a second waveguide may each transmit light for a distinct sample characterization technique. An example of an optical fiber includes a core, a first intermediate cladding disposed around the core, an attenuating cladding disposed around the first intermediate cladding, an attenuating cladding disposed around the first intermediate cladding, a second intermediate cladding disposed around the attenuating cladding, a waveguide cladding disposed around the second intermediate cladding, and outer cladding disposed around the waveguide cladding, and an outer coating around the outer cladding. An optical fiber may be formed using a rod-in-tube process.

A single mode optical fiber is provided that includes a core region having an outer radius ri and a maximum relative refractive index Δ.sub.1max. The single mode optical fiber further includes a cladding region surrounding the core region, the cladding region includes a depressed-index cladding region, a relative refractive index Δ.sub.3 of the depressed-index cladding region increasing with increased radial position. The single mode optical fiber has a bend loss at 1550 nm for a 15 mm diameter mandrel of less than about 0.75 dB/turn, a bend loss at 1550 nm for a 20 mm diameter mandrel of less than about 0.2 dB/turn, and a bend loss at 1550 nm for a 30 mm diameter mandrel of less than 0.005 dB/turn. Additionally, the single mode optical fiber has a mode field diameter of 9.0 microns or greater at 1310 nm wavelength.

An optical fiber includes: a core; and a cladding layer disposed on an outer circumference of the core. A Cl concentration in the cladding layer is 0.029 wt % to 0.098 wt %. In the optical fiber, Δ2−Δ1≤0 dB/km is satisfied at a wavelength of 430 nm where Δ1 is a value of transmission loss before exposure of the optical fiber to hydrogen and Δ2 is a value of transmission loss after the exposure.

A combined optical coherent tomography (OCT) pressure sensor system includes an optical cable comprising a single-mode core and a multi-mode core. An OCT optical imaging sensor near a distal end of the optical cable can be inserted into a lumen of a living being. First light exiting a distal end of the single-mode core illuminates an interior of the lumen. The OCT optical imaging sensor acquires image information about the interior of the lumen and transmits an optical signal carrying the image information into the distal end of the single-mode core, toward a proximal end of the single-mode core. An optical pressure sensor attached near the OCT optical imaging sensor receives second light from the distal end of the optical cable, senses ambient pressure within the lumen and transmits an optical signal indicative of the ambient pressure into a distal end of the multi-mode core, toward a proximal end of the multi-mode core.

An optical fiber includes a core, an inner cladding surrounding the core, and an outer cladding surrounding the inner cladding. A mean relative refractive index difference Δ1 of the core, a mean relative refractive index difference Δ2 of the inner cladding, and a mean relative refractive index difference Δ3 of the outer cladding satisfy a relationship of Δ1>Δ3≥Δ2. A ratio r2/r1 of an inner cladding radius r2 to a core radius r1 is 4.5 or higher and 5.5 or lower. A minimum value Δmin of a relative refractive index difference is −0.030% or higher and −0.010% or lower. A radius rmin at which the relative refractive index difference is the minimum value Δmin satisfies a relationship of r1<rmin<r2. (Δmin−Δ(r1))/(rmin−r1) is −0.002%/μm or lower, where Δ(r1) denotes the relative refractive index difference with the core radius r1.

An apparatus includes multiple dual cladding waveguides each having a single-mode interior section that transports one of multiple outgoing optical signals and a multimode section at least partially surrounding the interior section that transports one of multiple incoming optical signals. Different outgoing signals have different polarizations, and different incoming signals have different polarizations. The apparatus also includes a polarization beamsplitter that combines the multiple outgoing signals to produce transmit optical signals and separates receive optical signals to produce the multiple incoming signals.