A multicore optical fiber comprises a common cladding and a plurality of core portions disposed in the common cladding. Each of the core portions includes a central axis, a core region extending from the central axis to a radius r.sub.1, the core region comprising a relative refractive index Δ.sub.1, an inner cladding region extending from the radius r.sub.1 to a radius r.sub.2, the inner cladding region comprising a relative refractive index Δ.sub.2, and a depressed cladding extending from the radius r.sub.2 to a radius r.sub.3, the depressed cladding region comprising a relative refractive index Δ.sub.3 and a minimum relative refractive index Δ.sub.3 min. The relative refractive indexes may satisfy Δ.sub.1>Δ.sub.2>Δ.sub.3 min. The mode field diameter of each core portion may greater than or equal to 8.2 μm and less than or equal to 9.5 μm.

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 includes: a central core portion; an intermediate layer; a trench layer; and a cladding portion. Further, Δ1>Δ2>Δ3 and 0>Δ3 are satisfied, where Δ1 is a relative refractive-index difference of the central core portion, Δ2 is a relative refractive-index difference of the intermediate layer, and Δ3 is a relative refractive-index difference of the trench layer with respect to the cladding portion, respectively, and (c−b) is smaller than 4.5 μm when Δ1 is equal to or larger than 0.36% and equal to or smaller than 0.40%, Δ2 is equal to or larger than −0.05% and equal to or smaller than 0.05%, |Δ3| is equal to or smaller than 0.25%, Δ1×|Δ3| is equal to or smaller than 0.08%.sup.2, an inner diameter of the trench layer is 2b, and an outer diameter of the trench layer is 2c.

An optical fiber includes: a central core portion; an intermediate layer configured to surround an outer periphery of the central core portion; a trench layer configured to surround an outer periphery of the intermediate layer; and a cladding portion configured to surround an outer periphery of the trench layer. The central core portion is made of silica based glass that does not contain germanium (Ge). Δ1>Δ2>Δ3 and ΔClad>Δ3, where Δ1 represents an average maximum relative refractive-index difference of the central core portion relative to pure quartz glass, Δ2 represents an average relative refractive-index difference of the intermediate layer relative to the pure quartz glass, Δ3 represents an average relative refractive-index difference of the trench layer relative to the pure quartz glass, and ΔClad represents an average relative refractive-index difference of the cladding portion relative to the pure quartz glass. Δ1 is equal to or larger than 0.05%.

The present invention relates to an ultra-low loss optical fiber for long haul communications (100) comprising a core region (102) defined by a core relative refractive index and a cladding region surrounding the core region, defined by a cladding relative refractive index. In particular, the core region comprises a relative refractive index in a range of −0.06% to +0.06% and the cladding region is down-doped for entire radial cladding thickness. Moreover, the cladding region further comprises an inner cladding region (104) defined by an inner cladding relative refractive index and an outer cladding region (106) defined by an outer cladding relative refractive index. The inner cladding relative refractive index is less than the outer cladding relative refractive index.

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.

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 Δ1.sub.max. 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, has 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 0.002 dB/turn. Additionally, the single mode optical fiber has a mode field diameter of 9.0 microns or greater at 1310 nm wavelength and a cable cutoff of less than or equal to about 1260 nm.

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.

An optical fiber includes a glass fiber and a coating resin layer surrounding the outer periphery of the glass fiber. The coating resin layer has a primary resin layer that surrounds the outer periphery of the glass fiber, and a secondary resin layer that surrounds the outer periphery of the primary resin layer. The primary resin layer has a thickness of 7.5 μm or more and 17.5 μm or less. The primary resin layer has a Young's modulus of 0.10 MPa or greater and 0.50 MPa or less at 23° C. The secondary resin layer has a thickness of 5.0 μm or more and 17.5 μm or less. The secondary resin layer has an outer diameter of 165 μm or more and 175 μm or less. The secondary resin layer has a Young's modulus of 1200 MPa or greater and 2800 MPa or less at 23° C.

A transmission cable is provided to implement high-speed inter-device interconnection and intercommunication. The transmission cable includes a positive dispersion transmission section, a negative dispersion transmission section, and a dispersion matching section. A cross-sectional diameter of the positive dispersion transmission section is less than a cross-sectional diameter of the negative dispersion transmission section. The dispersion matching section is configured to connect the positive dispersion transmission section and the negative dispersion transmission section. The transmission cable can implement dispersion cancellation to reduce total group delay.