An optical fiber manufacturing method includes setting a first holding member and a rod inside a glass pipe, the first holding member made of glass and having plural holes formed, so that the rod is supported by the first holding member; filling glass particles between the rod and a glass pipe inner wall; holding the rod such that the rod and the filled glass particles are enclosed by the glass pipe inner wall and the first and second holding members, and sealing one end of the glass pipe and manufacturing an intermediate; and manufacturing an optical fiber from the intermediate, wherein a bulk density of the first and second holding members is set with reference to a bulk density of a filling portion made from the glass particles, and the predetermined range is determined according to a core diameter permissible variation range in its longitudinal direction.

A quantum communications system includes a quantum key generation system having a photonic quantum bit generator, a dispersion compensating optical fiber link, and a photon detector unit and a communications network having a signal generator, a signal channel, and a signal receiver. The dispersion compensating optical fiber link extends between and optically couples the photonic quantum bit generator and the photon detector unit. Further, the dispersion compensating optical fiber link is structurally configured to induce dispersion at an absolute dispersion rate of about 9 ps/(nm)km or less and induce attenuation at an attenuation rate of about 0.18 dB/Km or less such that the quantum key bit information of a plurality of photons output by the one or more photonic quantum bit generators is receivable at the photon detector unit at a bit rate of at least about 10 Gbit/sec.

The present disclosure provides an optical fiber (100). The optical fiber (100) includes a core region (102). The core region (102) is defined by a region around central longitudinal axis (112) of the optical fiber (100). In addition, the core region (100) has a first annular region (106). The first annular region (106) is defined from the central longitudinal axis (112) to a first radius from the central longitudinal axis. Moreover, the core region (102) has a second annular region (108). The second annular region (108) is defined from the first radius to a second radius. Further, the core region (102) has a third annular region (110). The third annular region (110) is defined from the second radius to a third radius. Also, the optical fiber (100) includes a cladding (104). The cladding region (104) has a fourth radius.

The present disclosure provides an optical fiber. The optical fiber includes a core region. The core region is defined by a region around central longitudinal axis of the optical fiber. In addition, the core region has a first annular region. The first annular region is defined from the central longitudinal axis to a first radius r.sub.1 from the central longitudinal axis. Moreover, the core region has a second annular region. The second annular region is defined from the first radius r.sub.1 to a second radius r.sub.2. Further, the core region has a third annular region. The third annular region is defined from the second radius r.sub.2 to a third radius r.sub.3. Also, the optical fiber includes a cladding. The cladding region has a fourth radius r.sub.4.

The present disclosure provides an optical fiber. The optical fiber includes a core region. The core region is defined by a region around central longitudinal axis of the optical fiber. In addition, the core region has a first annular region. The first annular region is defined from the central longitudinal axis to a first radius r.sub.1 from the central longitudinal axis. Moreover, the core region has a second annular region. The second annular region is defined from the first radius r.sub.1 to a second radius r.sub.2. Further, the core region has a third annular region. The third annular region is defined from the second radius r.sub.2 to a third radius r.sub.3. Also, the optical fiber includes a cladding. The cladding region has a fourth radius r.sub.4.

A specialized, dispersion-controlled fiber is particularly configured to exhibit a relatively uniform dispersion (D) over a broad spectral range (for example, 1000 nm to 2000 nm). The specialized fiber exhibits an essentially constant attenuation () over this same spectral range so that the fiber is defined as having a high figure of merit (FoM) where FoM is defined as |D|/. The specialized fiber is well-suited for use as a pulse stretcher, providing the ability to separate out wavelength constituents of an extremely short (fs, ps) broadband pulse into the ns range, for example.

The present embodiment relates to an MCF in which the strength of mode coupling or power coupling between adjacent cores included in one coupled-core group is set to an appropriate level to reduce a DGD. The MCF includes at least one coupled-core group. A core interval between adjacent cores included in the coupled-core group is set such that a mode coupling coefficient between the adjacent cores at a wavelength of 1550 nm satisfies 2.610.sup.0 [m.sup.1] to 1.610.sup.2 [m.sup.1] or a power coupling coefficient between the adjacent cores at the wavelength of 1550 nm satisfies 1.310.sup.3 [m.sup.1] to 8.110.sup.0 [m.sup.1].

The present embodiment relates to an MCF in which the strength of mode coupling or power coupling between adjacent cores included in one coupled-core group is set to an appropriate level to reduce a DGD. The MCF includes at least one coupled-core group. A core interval A between adjacent cores included in the coupled-core group is set such that a mode coupling coefficient between the adjacent cores at a wavelength of 1550 nm satisfies 2.610.sup.0 [m.sup.1] to 1.610.sup.2 [m.sup.1] or a power coupling coefficient between the adjacent cores at the wavelength of 1550 nm satisfies 1.310.sup.3 [m.sup.1] to 8.110.sup.0 [m.sup.1].