84results about "Dual mode fibre" patented technology

Various types of holey fiber provide optical propagation. In various embodiments, for example, 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 the hole spacing to yield a desired operation with a desired leakage loss of the fundamental mode. Resulting holely 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. Other embodiments are also provided.

An optical fiber adapted to carry optical power for powering an electrical device and also optionally adapted to carry optical data for signal processing. The optical fiber capable of carrying both optical data and optical power includes a central data waveguide region that carries data light and an annular power waveguide region concentrically surrounding the data waveguide region and adapted to carry relatively large amounts of optical power. A first annular isolation region between the data and power waveguide regions and that includes microstructures serves to optically isolate the waveguide regions. An outer annular isolation region serves to confine power light to the power waveguide region and contributes to the bend-resistance of the optical fiber. An optical power and optical data distribution system that utilizes the optical fiber is also described.

A few mode optical fiber suitable for use in a mode division multiplexing (MDM) optical transmission system is disclosed. The optical fiber has a graded-index core with a radius R1 in the range from 8 [mu]m to 14 [mu]m, an alpha value greater than or equal to about 2.3 and less than about 2.7 at a wavelength of 1550 nm, and a maximum relative refractive index Delta1MAX from about 0.3% to about 0.6% relative to the cladding. The optical fiber also has an effective area greater than about 90 [mu]m2 and less than about 160 [mu]m2. The core and cladding support only the LP01 and LP11 modes at wavelengths greater than 1500 nm. The cladding has a maximum relative refractive index Delta4MAX such that Delta1MAX>Delta4MAX, and the differential group delay between the LP01 and LP11 modes is less than about 0.5 ns/km at a wavelength of 1550 nm.

A system for filtering light propagating in a waveguide is described. The system utilizes an adjustable periodic grating which induces mode coupling of predetermined frequencies of light propagating in the waveguide.

The invention relates to a few-mode fiber with relatively low different group delay (DGD). The few-mode fiber comprises a core layer and claddings, and is characterized in that the relative refractive index difference delta 1 of the core layer is 0.24% to 0.36%; the radius R1 of the core layer is 9-12 micrometers; the claddings coating the core layer comprise an inner cladding, a sunken cladding and an outer cladding from inside to outside; the relative refractive index difference delta 2 of the inner cladding is -0.02% to 0.02%; the radius R2 of the inner cladding is 13.6-18 micrometers; the sunken cladding is divided into a first sunken cladding and a second sunken cladding; the radius R3 of the first sunken cladding is 16-30 micrometers; the difference between R3 and R2 is larger than or equal to 2 micrometers; the relative refractive index difference of the first sunken cladding is alpha-type refractive index distribution gradually reduced from delta 2 at R2 to delta 3 at R3; delta 3 is -0.8% to -0.4%; the relative refractive index difference of the second sunken cladding is delta 3; the radius R4 is 18.6-30 micrometers; R4 is larger than or equal to R3; the quotient of the difference between R3 and R2 divided by the difference between R4 and R2 is larger than or equal to 0.5 and smaller than or equal to 1; the outer cladding is a pure quartz glass layer. The few-mode fiber has lower DGD and relatively high MFD, and keeps relatively good anti-bending performance.

Shunt fibers having a photonic bandgap cladding region including one or more hollow guiding regions of which one guiding region is configured as the core and one or more other guiding regions are configured as shunts, respectively, provide nearly single mode transmission in the core. The effective mode index of unwanted core modes and modes in one or more shunts are matched closely enough such that higher order modes will selectively couple to the shunt modes by resonant phase matching in the presence of fiber variations. The shunts are designed to have relatively higher losses thereby effectively dissipating power in the higher order modes at a faster rate.

An optical multi-mode HIC (high index contrast) waveguide (102,104, 201, 301) for transporting electromagnetic radiation in the optical waveband, the waveguide comprising a guiding core portion (204) with higher refractive index, and cladding portion (206) with substantially lower refractive index configured to at least partially surround the light guiding core in the transverse direction to facilitate confining the propagating radiation within the core, the wave-guide being configured to support multiple optical modes of the propagating radiation, wherein the waveguide incorporates a bent waveguide section (202) having bend. curvature that is configured to at least gradually, preferably substantially continuously, increase towards a maximum curvature of said section from a section end.

A multiple-layer fiber-optic sensor is described with dual Bragg gratings in layers of different materials, so that the known temperature and strain response properties of each material may be utilized to simultaneously correct the sensor output for temperature and strain effects.

Single-mode optical fiber systems, incorporating fiber of core radius of sufficient size to support the fundamental mode together with from one to three higher order modes, exhibit performance/cost advantages relative to systems based on traditional single-mode fiber.

A double core optical fiber is provided, in which single mode signal light and multimode signal light can be transmitted and a multimode transmission of the signal light guided through the core can be reduced even when the optical fiber is bent. The double core optical fiber of the present invention includes a core (111) arranged on a central axis of the optical fiber and having a refractive index (112), a first cladding (121) arranged on the outer circumference of the core (111) and having a refractive index (122) smaller than the refractive index (112), and a second cladding arranged on the outer circumference of the first cladding (121) and having a refractive index (132) smaller than the refractive index (122). The core (111) functions as a core for single mode transmission, the core (111) and the first cladding (121) function as a core for multimode transmission, the first cladding (121) function as a cladding for the core for single mode transmission, and the second cladding (132) functions as a cladding for the core for multimode transmission.

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 n₁ and a maximal refractive index n₀. The optical fiber 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:

C=NA−0.02×a

• where:
• NA=√{square root over (n₀²−n₁²)}=n₀·√{square root over (2Δ)} with

The minimal and maximal refractive indexes n₁, n₀ and the optical core radius a are chosen such that NA>0.20, a>10 μm and |C|<0.20.

An optical fiber includes a core portion and a cladding portion that is formed on an outer periphery of the core portion and has a refractive index lower than a maximum refractive index of the core portion. Characteristics at a wavelength of 1550 nm are an effective core area of a fundamental propagation mode of equal to or larger than 120 μm², an effective core area of a first higher-order propagation mode of equal to or larger than 170 μm², and an effective refractive index of the first higher-order propagation mode of larger than the refractive index of the cladding portion by equal to or larger than 0.0005.

A technique is described for generating a Bessel beam. An input optical fiber is provided that supports propagation in the fundamental mode. The input fiber is connected to a fiber mode converting device that provides phase matching, at a predetermined excitation wavelength, between the fundamental mode and a selected azimuthally symmetric higher-order mode. As an input to the fiber mode converting device, a coherent light beam is fed through the input optical fiber to provide a fundamental mode input at the excitation wavelength. The fiber mode converting device resonantly excites the selected azimuthally symmetric mode. The azimuthally symmetric mode is provided as a beam output from an endface of the fiber mode converting device to approximate a Bessel beam.

The invention relates to a multimode optical fibre having a refractive index profile, comprising a light-guiding core surrounded by one or more cladding layers. The present invention furthermore relates to an optical communication system comprising a transmitter, a receiver and a multimode optical fibre.

An index grating is imprinted in the core of an optical fiber using a specially designed silica glass phase grating mask. The phase mask is held in close proximity to the optical fiber. Laser irradiation of the phase mask with ultraviolet light at normal incidence imprints (photoinduces) into the optical fiber core the interference pattern created by the phase mask.