Some embodiments of the disclosure relate to an optical transmission system that operates at a wavelength in the range from 950 nm to 1600 nm and that employs a single-mode optical transmitter and an optical receiver optically coupled to respective ends of a multimode fiber designed for 850 nm multimode operation. The optical transmission system also employs at least one single mode fiber situated within the optical pathway between the optical transmitter and the receiver and coupled to the multimode fiber.

It is proposed a home optical data network formed of an optical fiber comprising an optical core and an optical cladding surrounding the optical core, the optical core having a refractive graded-index profile with a minimal refractive index n.sub.1 and a maximal refractive index n.sub.0, said optical fiber being such that it has a numerical aperture NA and an optical core radius a satisfying a criterion C of quality of optical communications defined by the following equation:

[00001]$C=\mathrm{NA}-0.02a$$\mathrm{where}.Math.\text{:}$$\mathrm{NA}=\sqrt{n_0^2-n_1^2}=n_0.Math.\sqrt{2.Math.}.Math..Math.\mathrm{with}.Math..Math.=\frac{n_0^2-n_1^2}{2.Math.n_0^2},$

is the normalized refractive index difference,
and in that said minimal and maximal refractive indexes n.sub.1, n.sub.0 and said optical core radius a are chosen such that NA>0.20, a>10 m and |C|<0.20.

Holey fibers provide optical propagation. In various embodiments, a large core holey fiber comprises a cladding region formed by large holes arranged in few layers. The number of layers or rows of holes about the large core can be used to coarse tune the leakage losses of the fundamental and higher modes of a signal, thereby allowing the non-fundamental modes to be substantially eliminated by leakage over a given length of fiber. Fine tuning of leakage losses can be performed by adjusting the hole dimension and/or spacing to yield a desired operation with a desired leakage loss of the fundamental mode. Resulting holey fibers have a large hole dimension and spacing, and thus a large core, when compared to traditional fibers and conventional fibers that propagate a single mode. Other loss mechanisms, such as bend loss and modal spacing can be utilized for selected modes of operation of holey fibers.

The present invention generally relates to the field of fiber optics, and more specifically to optical fibers, methods of manufacturing optical fibers, and methods of classifying optical fibers. In an embodiment, the present invention is a multimode optical fiber which comprises a core and clad material system where the refractive indices of the core and cladding are selected to minimize chromatic dispersion in the 850 nm wavelength window and the refractive index profile is optimized for minimum modal-chromatic dispersion in channels utilizing VCSEL transceivers. Multimode optical fibers according to this embodiment may have increased channel bandwidth.

It is proposed an optical fiber including an optical core and an optical cladding surrounding the optical core. The optical core has a refractive graded-index profile with a minimal refractive index n.sub.1 and a maximal refractive index n.sub.0. The optical fiber has a numerical aperture NA and an optical core radius satisfying a criterion C of quality of optical communications defined by the following equation:
C=NA0.02a where: NA={square root over (n.sub.0.sup.2n.sub.1.sup.2)}=n.sub.0.Math.{square root over (2)} with $=\frac{n_0^2-n_1^2}{2n_0^2},$ is the normalized refractive index difference. The minimal and maximal refractive indexes n.sub.1, n.sub.0 and the optical core radius a are chosen such that NA>0.20, a>10 m and |C|<0.20.

It is made possible to satisfactorily determine whether or not the light diameter of collimated light is within a defined range in a double mode.

A light intensity distribution of collimated light including components of a fundamental mode and a first-order mode is acquired by a light intensity distribution acquisition section. A light intensity line corresponding to a predetermined light intensity lower than a maximum intensity of light intensity is acquired by a light intensity line acquisition section in reference to the light intensity distribution. The ratio of inclusion of the light intensity line in an annular region between a first circle and a second circle larger than the first circle with an optical axis of the collimated light in a center in an entire circular region centered on the optical axis of the collimated light is calculated by a ratio calculation section. Further, it is determined by a determination section whether or not the light diameter of the collimated light is within a defined range, in reference to the ratio.

An optical fiber which allows propagation of two or more modes, and in a case where a mode coupling coefficient between at least two modes among the two or more modes is h [1/km], the length of the optical fiber is z [km], and the amount XT of coupling between the two modes is represented by XT=10.Math.log.sub.10(zh) [dB], the amount XT of coupling satisfies Expression (A) described below.

XT+14 [dB](A)

An example apparatus may include an optical splitter apparatus that includes a dual mode fiber having a single mode fiber core embedded in a multi-mode fiber core, a plurality of single mode fibers, and a funnel waveguide coupling the dual mode fiber to the single mode fibers. The optical splitter apparatus may be for use in a passive optical network. The single mode fiber core may be for transmitting downstream optical signals, where the funnel waveguide distributes the downstream optical signals to the single mode fibers. In addition, the single mode fibers may transmit upstream optical signals, and the funnel waveguide may direct the upstream optical signals into the multi-mode fiber core. The optical splitter apparatus may have an asymmetric insertion loss ratio between the downstream optical signals received via the single mode fiber core and the upstream optical signals received via the single mode fibers.

An example apparatus may include an optical splitter apparatus that includes a dual mode fiber having a single mode fiber core embedded in a multi-mode fiber core, a plurality of single mode fibers, and a funnel waveguide coupling the dual mode fiber to the single mode fibers. The optical splitter apparatus may be for use in a passive optical network. The single mode fiber core may be for transmitting downstream optical signals, where the funnel waveguide distributes the downstream optical signals to the single mode fibers. In addition, the single mode fibers may transmit upstream optical signals, and the funnel waveguide may direct the upstream optical signals into the multi-mode fiber core. The optical splitter apparatus may have an asymmetric insertion loss ratio between the downstream optical signals received via the single mode fiber core and the upstream optical signals received via the single mode fibers.

An object of the present disclosure is to enable LPG applied over the entire length of an optical fiber without inhibiting an operation of taking out the optical fiber.

The present disclosure relates to an optical fiber cable in which at least one or more optical fibers for transmission in at least two or more modes are gathered, the optical fiber cable including: a linear material abutting on at least one of the optical fibers, in which a thickness of the linear material periodically varies in a longitudinal direction of the linear material.