Northern Telecom Limited

Jds Fitel Inc.

Other

Koichi Abe

Gary S Duck

Mark Farries

Stephen J Mihailov

Paul Colbourne

Yihao Cheng

Joseph W Ip

Jinghui Li

Brian Braham

A system and method are disclosed for demulitplexing closely spaced channels carrying optically encoded data. A composite optical signal having data channels corresponding to center wavelengths .lambda.1, .lambda.2, .lambda.3, .lambda.4, . . . .lambda.n are separated into two composite optical signals of first of which comprises data channels corresponding to center wavelengths .lambda.1, .lambda.3, . . . .lambda.n and a second which comprises data channels corresponding to center wavelengths .lambda.2, .lambda.4, . . . .lambda.n-1, wherein adjacent channels center wavelengths are separated from one another by a distance 'd'. A periodic multi-cavity Fabry-Perot etalon having a free spectral range of '2d' is coupled to a circulator for launching an input beam. The first of the two composite optical signals carrying channels 1, 3, . . . n is reflected from the input port of the etalon and the second of the of the two optical signals carrying channels 2, 4, . . . n-1 is transmitted through the etalon. After the two signals are separated, further separation can be achieved by using conventional dichroic filters.

Method and circuit for demultiplexing an optical signal

A method and optical system are provided which lessen spherical aberration normally associated with coupling small-diameter core optical fiber with a collimating lens. By coupling and optically aligned ends of thermally expanded core (TEC) fiber having a small output angular divergence to a GRIN lens, spherical aberration is significantly reduced.

Method and optical system for passing light between an optical fiber and

A device for distributing an optical signal has an optical waveguide with a plurality of gratings disposed in series therein, the gratings having a predetermined reflectivity response within a specific wavelength range; an optical circulator having at least three ports, one of the ports serving as an input port for receiving the optical signal, and another port for removing at least a part of the optical signal reflected from one of the gratings; and control means for individually controlling at least some of the gratings to effect a change of the wavelength range of the reflectivity response of the gratings. The change may be a shift, an expansion or a compression of the range. The device can function as a signal distributor (router), an equalizer or a demultiplexer. The reflectivity response is preferably a sloped response.

Variable-attenuation tunable optical router

A system for automatically aligning optical components without active alignment techniques is provided. Optical components are placed into an alignment sleeve having an opening with a diameter sized to tightly receive optical components. Optical fibers having thermally expanded core ends are used to coupled light within the alignment sleeve. In instances where the optical fibers are offset from the longitudinal axis of the sleeve, means are provided to prevent rotation of an optical fiber tube holding the optical fibers.

Method and system for aligning of optical elements

An attenuator capable of controllably attenuating at least two wavelengths of light is configured to have an optical waveguide section having at least two Bragg gratings disposed therein in series. The Bragg gratings have a sloped reflectivity response within a predetermined wavelength range. The sloped response is a function of refractive index variations within each of the grating elements. By compressing or expanding at least one of the gratings, the periodicity is modified so as to shift its central wavelength within a predetermined wavelength range.

Bragg grating variable optical attenuator

Optical cable having a central core with grooves along the outside, the grooves housing tubes containing optical fibers. The grooves are inclined to the core axis and preferably are sinusoidal in that they extend around the core in each direction while extending axially and do not complete a revolution around the core before changing direction. In preferred structures, the tubes contact around a concave base surface of the grooves or contact opposing groove walls. In addition, the tubes provide greater strength if they are in a load transmitting relationship with a metal sheath if there is one. The structure also allows for a different water blocking material to be used within the tubes than outside the tubes and within the grooves so as to satisfy different property requirements.

Optical cable with improved strength

Optical waveguide having a fused silica core and a fluorine doped silica cladding is made by heating a cylinder of silica in fluorine, the cylinder initially having an outer annular particulate or porous region which is dried by the fluorine and into which fluorine diffuses to lower the refractive index of the silica when fused. The cylinder is made by depositing particulate silica onto a mandrel, drying the silica in chlorine, and heating the silica to densify it. Further particulate silica is deposited and is then heated in a fluorine-containing gas to dry, fluorine diffuse, and sinter the porous outer part of the silica. The resulting tubular silica preform is heated to collapse the tubular preform into a rod from which optical waveguide is drawn, the waveguide having a fluorine doped silica cladding. In one alternative the silica cylinder is made by depositing onto a mandrel a first layer of relatively dense silica followed by a second layer of less dense particulate silica so that fluorine diffuses preferentially into the lower density material. In another alternative, the silica cylinder is made by depositing particulate silica directly onto a high purity fused silica rod without using a mandrel, the deposited silica then being dried and subjected to fluorine diffusion.

Optical waveguide manufacture

A tubular porous silica preform is made by depositing particulate silica on a mandrel from which the preform is subsequently removed. A solid cylindrical porous silica preform is made by depositing particulate silica on an end surface of a support body. The porous preforms are then dried and the tubular preform is heated in a fluorine containing atmosphere to introduce a fluorine dopant into the silica. The rod preform is then placed inside the tubular preform and the two preforms are further dried in a chlorine atmosphere to remove residual moisture. The dual preforms are then heated in a zone sintering furnace to consolidate and collapse the porous material of the rod and tubular preforms into a transparent fused silica rod. The composite preform obtained is heated and dielectric optical waveguide drawn from it, the waveguide having a pure silica or doped silica core derived from the rod preform and a fluorine doped silica cladding derived from the tubular preform.

Optical fiber

Optical waveguide having a fused silica core and a fluorine doped silica cladding is made by heating a cylinder of silica in fluorine, the cylinder initially having an outer annular particulate or porous region which is dried by the fluorine and into which fluorine diffuses to lower the refractive index of the silica when fused. The cylinder is made by depositing particulate silica onto a mandrel, drying the silica in chlorine, and heating the silica to densify it. Further particulate silica is deposited and is then heated in a fluorine-containing gas to dry, fluorine diffuse, and sinter the porous outer part of the silica. The resulting tubular silica preform is heated to cause fusion of the porous silica and to collapse the tubular preform into a rod from which optical waveguide is drawn, the waveguide having a fluorine doped silica cladding. The fluorine drying and diffusion steps produce HF which is extremely corrosive. To avoid escape of HF, the fluorine drying, diffusion and consolidation steps are all performed within a single protective fused silica tube. After termination of the drying, diffusion and consolidation steps, the protective silica tube is collapsed so as to become an outer layer of the preform and is incorporated within fiber drawn from the preform.

Method for manufacturing optical waveguide

Before splicing optical fibers having cladding and core of differing refractive index, the cores are axially aligned. The fiber ends are held apart with the fibers approximately coaxial. The fiber end surfaces are then illuminated and reflected light is monitored. Since reflectivity is a function of refractive index, the position of the core in the reflectivity profile of each surface can be readily identified. The fiber ends can then be manouvered transverse of the fiber axes to bring the fiber core centers into registration with a datum line. The fiber ends are then brought close together for splicing. Previously, fibers having nominally identical outside diameters were aligned simply by pressing them into a common V groove, the optical transmission efficiency then depending on fiber/core concentricity. Alternatively, light was injected into the far end of one fiber, monitored at the far end of the other fiber, and the fibers at their near end manipulated to maximize monitored optical power. The present invention provides an easier and cheaper method of ensuring core alignment especially for monomode fibers.

Precise positioning of optical fibers

For making a preform for production of optical fiber, the preform including fused silica, particulate material is deposited on the inside wall of a glass tube while the tube is reciprocated through a microwave cavity for production of a plasma in the tube. Oxygen and a reactant gas containing silica are passed through the tube. Dopant material can be added to the gas mixture and the concentration of the dopant varied to vary the refractive index. After the deposit of a sufficient thickness of particulate material, it is fused. The material can be caused to fuse on to the inner wall of the tube or to shrink away from the inner wall and removed from the tube. When the material is fused onto the wall of the tube it can then be collapsed, then either drawn to a fiber or placed in a further tube and drawn to a fiber. When the fused material shrinks from the tube wall, then it is collapsed to a solid rod, placed in a tube and then drawn to a fiber.

Growing community of inventors

Ottawa, Canada

Koichi Abe