Abstract: An efficient downlight system for directing light includes a light source and a generally tubular, hollow coupling device with an interior light-reflective surface for receiving light from the source at an inlet and transmitting it as a generally diverging light beam through an outlet. The coupling device is shaped in accordance with non-imaging optics and increases in cross sectional area from inlet to outlet in such manner as to reduce the angle of light reflected from the surface as it passes through the device. A thermal-isolating region has an inlet positioned in proximity to an outlet of the coupling device and has an outlet for passing light to an optical member. An arrangement for splitting the light from the outlet of the thermal-isolating region comprises a plurality of light guides. Each light guide includes an inlet end for receiving light from the thermal-isolating region and an outlet end for directing light to a remote location.

Abstract: A reliable lighting system is proposed for utilizing the advantages of a centralized light system, wherein at least one optical fiber for the transport of at least a portion of the light of the light sources to at least one light emission location is provided, one of the light sources being a high-intensity gas discharge lamp, in particular a xenon lamp, and the other light source being a halogen lamp.

Abstract: Disclosed is a tap coupler which comprises a ferrule comprising first and second optical fibers symmetrically positioned with respect to an optical axis and transmitting optical signals; and a graded index (GRIN) lens converting a part of the optical signals provided by one of the optical fibers of the ferrule into parallel beams and outputting the same, and reflecting the remaining part of the optical signals and outputting the same to another optical fiber of the ferrule, and having an uncoated beam outputting surface of the GRIN lens. The tap coupler can easily extract a part of the transmitted optical signals with low production cost and a smaller size.

Abstract: An apparatus for interfacing optical signals to an optical fiber has a layered interface element with a first electrically conductive layer defining a first surface, a photoactive material layer in intimate contact with the first layer on a second surface opposite the first surface, a second electrically conductive layer in intimate contact with the photoactive material layer, confining the photoactive material layer between the first and second electrically conductive layers, and a third surface angularly disposed to the first surface and intersecting the photoactive material layer; and a pressure element having a contact surface translatable toward the first surface of the interface element, to urge an optical fiber positioned across the interface element into the first surface, and by local deformation of the optical fiber also into the third surface, creating thereby an intimate contact region between an edge of the photoactive layer intersecting the third surface and the optical fiber.

Abstract: An optical device capable of detecting the intensity and wavelength of light from a light source with a high level of precision, and an optical module incorporating the optical device. The optical device has a planar lightwave circuit having a Y-branched core, a silicon substrate, a filter block, an optical fiber, and a first and a second photodiode. The end portion on the input side of the core is connected to the optical fiber. One end portion on the output side of the core is connected to the filter block, and the other on the same side is to the second photodiode. The light is divided at a predetermined ratio at the Y-branching portion. One of the branched light is sent through the filter block to be input to the first photodiode, and the other branched light is directly input to the second photodiode.

Abstract: The position of an oblique mirror structure inside a polymer waveguide in relation to an optical device is accurately defined by using an integrated mask of metal, which is defined using photolithography, on top of the waveguide structure. When irradiating the surface of the waveguide with laser light, it is only let through where no metal is left, so that the recess formed is defined by edges of strips of the metal layer. In the same metal layer also electrical contact pads are produced used for self-aligning flip-chip mounting of devices such as lasers and photodiodes. Another metal layer can be applied inside the waveguide structure at a place under the waveguide core so that it is hit by and stops the laser light. The energy of the laser light will atomize the metal and the dispersed metal will then be deposited on the walls of the recess.

Abstract: A semiconductor light-receiving device comprises a substrate, an optical fiber, a semiconductor light-receiving element, an optical member, and holders. A groove for a buried optical fiber is formed in the main surface of the substrate to extend from one end of the substrate to the other end thereof. The optical fiber is buried in the optical fiber groove and covered with a resin material. The semiconductor light-receiving element has a light-receiving portion at a surface thereof in opposing relation to the main surface of the substrate and is disposed on the main surface of the substrate via bumps such that the light-receiving portion is opposed to the optical fiber. The optical member is disposed in the substrate in an intersecting relationship with the optical fiber to reflect or diffract signal light propagated through the optical fiber and irradiate the light-receiving portion of the semiconductor light-receiving element with the reflected or diffracted signal light.

Abstract: A variable optical amplifier mounts a fiber coupler within a flexure that provides for deflecting one section of the coupler with respect to another about a tapered intermediate section for controlling transmissions through the coupler. The flexure has a free portion suspended by a pair of resilient arms for relatively deflecting the coupler sections while minimizing friction and maintaining a fixed angular orientation with an actuator. A kinematic link between the flexure and the actuator is thermally compensated not only at a given deflection position but throughout the entire intended range of operation.

Abstract: A horizontal deflecting optical waveguide is formed in an integrated circuit-like structure having a substrate and at least one layer of dielectric material above the substrate. A trench is formed in the dielectric material, and the trench has first and second portions angularly joined at a bent portion. A reflective layer of material adjoins, conforms to and extends along the side walls of the trench. A core of optically transmissive material conforms to the reflective layer within the trench. The reflective layer forms a wall at the bent portion which reflects light from the core located in one portion into the core located in the other portion.

Abstract: A power monitor for a light emitter emitting from a single face creates a monitor beam by deflecting a portion of the application beam and further manipulating the monitor beam to allow more efficient use of the monitor beam. For example, the monitor beam may be collimated to allow an increase in spacing between the light emitter and a detector for sensing the monitor beam. Alternatively or additionally, the monitor beam may be focused to allow use of a smaller detector and of a smaller percentage of the application beam. The diffractive element deflecting the beam may be either transmissive or reflective. The additionally manipulation of the monitor beam may be provided by the same diffractive element which deflects the beam, which is particularly useful when the diffractive element is reflective, and/or by additional optical elements.

Abstract: A bidirectional optical semiconductor apparatus of the present invention includes: a substrate embedding an optical waveguide, through which output light and input light are propagated; a semiconductor light-emitting device for emitting the output light toward one end of the optical waveguide; an optical branching filter, provided in the optical waveguide, for transmitting at least part of the output light and guiding at least part of the input light to the outside of the optical waveguide; a semiconductor light-receiving device, provided over the substrate, for receiving the input light guided by the optical branching filter to the outside of the optical waveguide; and a light-blocking member, formed on the surface of the semiconductor light-receiving device, for blocking the light emitted from the semiconductor light-emitting device.

Abstract: The present invention provides a method and apparatus for image sharpening in a confocal microscopy or endoscopy observation, the method comprising: collecting true confocal return light emanating from an observational field of an object; focussing the true confocal return light into a core of a fiber wave-guide; collecting near confocal return light from a volume partially overlapping the observational field and thereby defining an overlap volume; focussing the near confocal return light into the fiber wave-guide so as to be transmitted principally in a cladding of the fiber wave-guide; separately detecting the true confocal return light and the near confocal return light to produce a true confocal output signal and a near confocal output signal; and adjusting the true confocal output signal on the basis of the near confocal output signal to substantially eliminate from the true confocal output signal a component due to the near confocal output signal; whereby the effective volume of the observational field

Abstract: An optical device, has

Abstract: Improved optical devices, systems, and methods for selectively directing optical signals generally based on a Mach-Zehnder interferometer. Through accurate control of the phase relationship, the Mach-Zehnder interferometer allows optical signals to either be cumulatively combined so as to enhance the transmitted signal strength, or destructively combined so as to effectively prevent transmission from an optical signal port. This phase relationship can be controlled using a nonreciprocal device having a pair of retarder plates disposed along one of the two legs of the Mach-Zehnder interferometer so as to provide an optical isolator or circulator.

Abstract: An optical amplifier with redundant excitation light sources for exciting a rare earth doped optical fiber such as an EDF (Erbium Dope Fiber) minimizes the loss of the excitation light so as to introduce the excitation light to the EDF effectively, though an optical coupler, which plural optical fibers for transmitting the excitation lights from plural excitation light sources are welded, is used. And, the optical amplifier keeps the total of the excitation light introduced to the EDF at a predetermined value and changes one excitation light source to the other unless the output total from the respective excitation light sources becomes zero.

Abstract: In a method and a device for extracting signals out of a glass fiber without any detectable interference occurring, in particular without the signals propagating through the glass fiber experiencing any transmission loss, light that emerges laterally from the glass fiber due to scattering (Rayleigh scattering) processes, which are in existence anyway, is directed at a photodetector. In the process, the emerging light can be directed by focussing elements at the photodetector or at the input face of another glass fiber. In addition, the emerging light can be directed both directly as well as via at least one reflector at the photodetector.

Abstract: An apparatus for optically generating chaotic random numbers to obtain chaotic random numbers satisfying a chaotic dynamical system expressed by X(n+1)=F(X(n)) includes an optical signal splitting device for splitting light from a light source into a predetermined number of beams with identical optical power; an optical chaotic signal generating device comprising the same number of interferometers as the beams, each having a pair of optical paths for receiving the beams from the optical signal splitting device, splitting each of the beams, interfering the splitted beams and outputting optical chaotic signals; optical path length difference data memory device for memorizing data on a difference between the lengths of the pair of optical paths at portions thereof between splitting and interfering; optical output signal measuring device for measuring optical power of the optical chaotic signals output from the interferometers as chaotic random numbers; and an optical output signal memory device for m

Abstract: The present invention is an intelligent optical transmitter module that is used to produce optical test signals. The optical transmitter module contains a solid state laser and a microprocessor. The solid state laser produces the test signals which are used to test optical fibers in an optical fiber network. The laser is both monitored by and controlled by the microprocessor. In one embodiment, backface monitoring and optical output coupling power monitoring (using an optical tap) are accomplished within the module in order to more accurately reflect the state of the laser. The microprocessor reads data regarding the performance of the solid state laser which may be output to another control device. The control device utilizes the data from the microprocessor in the analysis of fiber optic loop conditions as well as the laser itself. The microprocessor enables the output levels of the solid state laser to be adjustable by way of a digital to analog converter.

Abstract: A monitoring apparatus for a high power light source comprises a fiber medium containing a high power output for an application with a first monitoring tap optically coupled to the fiber medium for removing a small portion of light from the output to monitor the output power level. A photodetector is optically coupled to receive the light portion to monitor the output power level. The photodetector, however, has a predetermined saturation level below the power level provided from the first monitoring tap. Therefore, at least one light attenuator is provided between the first monitoring tap and the photodetector to provide a level of monitoring power within a range below the saturation level of the photodetector to accurately monitor changes in the output power present on the fiber medium of the light source.

Abstract: An optical power monitoring tap for use in an optical transmission system advantageously uses existing reflected signal(s) within the transmission system as the “tap” source for the monitor. In particular, one or more multimode fibers are disposed so as to capture reflected signals and directed the reflections into a optical power monitor, such as a PIN photodiode. One or more interfaces within the transmission system (such as a face of an included GRIN lens) provides the reflected signal. In one embodiment, a set of three multimode fibers may be used to capture reflected signals from both an included GRIN lens and isolator component.

Abstract: Disclosed is an optical fiber displacement connector and method used with a fiber optic cable as an optical tap. The fiber optic cable includes a light carrying center, a cladding and a buffer. The cladding displacement connector has surfaces which can be used for displacing the buffer and cladding to expose the light carrying center. The cladding displacement connector at least partially surrounds the light carrying center of the fiber optic cable. The cladding displacement connectors are formed of an optically conductive material and is insertable into a printed circuit board or an integrated circuit chip. The connector can carry bi-directional and multi-wavelength light signals. The optical signal carried by the light carrying center of the fiber optic cable can be caused to exit the fiber optic cable by displacing the cladding, abrading the cladding, dissolving the cladding, and carving a groove into the light carrying center.

Abstract: An add/drop filter for optical wave energy incorporates a Bragg grating in a very narrow waist region defined by merged lengths of elongated optical fibers. Light is propagated into the waist region via adiabatically tapered fibers and is transformed from two longitudinally adjacent fibers into two orthogonal modes within the air-glass waveguide of the waist and reflected off the grating from one fiber into the other. The geometry of the waist region is such that the reflected drop wavelength is polarization independent, without lossy peaks in the wavelength band of interest. Additionally, back reflection are shifted out of the wavelength band of interest. High strength gratings are written by photosensitizing the waist region fibers by constantly in-diffusing pressurized hydrogen or deuterium. For narrow spectral bandwidth gratings, dimensional variations must be minimized or compensated, and the grating is apodized by both a.c. and d.c. variations in writing beams at a net constant power.

Abstract: An optical splitter for distributing a beam of light along a plurality of output paths. The amount of light output from each output path is user adjustable according to one embodiment of the present invention. In another embodiment the amount of light output from each output path is determined by the arrangement of the optical splitter. The present invention allows a single high-power high-intensity light generation source to simultaneously provide light to a plurality of lighting devices, instruments or tools.

Abstract: Existing fiber optic transmission systems do not provide for or permit a raceway arrangement for optically transmitted signals which would allow flexible access to such signals. The present invention provides a system for providing multiple access to a fiber optic transmission at selected locations along a continuum.

Abstract: A multi-mode pump laser having an output, and an optical fiber coupler. The optical fiber coupler has a first section and a second section. The first section of the optical fiber coupler comprises a multi-mode fiber which is optically coupled to the pump laser output. The second section of the fiber coupler comprises a plurality of single mode optical fibers each of which has an input which is optically coupled to the multi-mode fiber. The source further comprises a pump drive which is controllable to dither the optical center frequency of the light produced by the pump laser, so as to scramble modal power distribution at the inputs of the single mode optical fibers.

Abstract: In an optical power splitter for splitting input light into N equal optical waves, and a manufacturing method therefor, a main waveguide and (N−1) branched waveguides are arranged on one side or both sides of the main waveguide. The main waveguide and the (N−1) branched waveguides form a directional coupler. In each of the directional couplers, the branched waveguide has an appropriate phase mismatch, a proper coupling coefficient, and a suitable coupling length to output 1/N of input optical power in the main waveguide. In the optical power splitter, when the main waveguide is semicircular, a circular substrate can be effectively used when the optical power splitter is manufactured.

Abstract: A planar waveguide device is described which can function as either a switching or power dividing element of a soliton transmission communication system operating at a selected central wavelength. The device has one input and two outputs and consists of two optical channel waveguides, in a coupler-like configuration, each of whose cores has a refractive index and dielectric constant with a dependence on the optical signal intensity which can balance a negative dispersion in the waveguide at dimensions compatible with monomode transmission of the selected central wavelength. It is a property of such waveguides that if the input to one channel waveguide is a temporal optical soliton, the output will also be a temporal soliton, and the output waveguide, or waveguides, from which it exits the device as well as the power of the switched or power divided signal at each output will be dependent upon the input soliton peak power.

Abstract: A dense wavelength division multiplexer for separating an optical signal into optical channels is provided. The dense wavelength division multiplexer of the present invention includes a manner for inputting an optical signal where the optical signal comprises a plurality of optical channels; a manner for separating one or more of the plurality of optical channels by introducing a phase difference between at least two of the plurality of optical channels, where the manner of separation includes a polarization beam splitter; and a manner for outputting the separated plurality of optical channels along a plurality of optical paths. The dense wavelength division multiplexer of the present invention provides an ease in alignment and a higher tolerance to drifts due to the increase in the width of the pass band. Its separators may also be placed in a multi-stage parallel cascade configuration to provide for a lower insertion loss.

Abstract: A wavelength-dependent splitter/router is made by chirping a waveguide grating router, such that the path-length difference between pairs of adjacent grating arms is not a constant. With careful design, a device can be fabricated that acts as an optical splitter in one wavelength band and as an optical router in another wavelength band. The invention has applicability in optical networks, because it enables the overlaying of a wavelength-division-multiplexed (WDM) network (which relies on routers) with a broadcast type of network (which relies on splitters).

Abstract: The optical hold unit (100) of the present invention includes an optical modulator (108) that has an electrical input, an optical input, and an optical output. A 1.times.N optical splitter (106) is also provided that has an optical input and N optical outputs. In addition, N optical paths (112) are individually coupled to the N optical outputs and carry one of the N output signals. Each optical path has an associated propagation delay. Optical delay elements may be located in any of the N optical paths that carry the output signals. The optical delay elements serve to lengthen the propagation delay (114a-e) of the optical path (112a-e) in which the optical delay element is located. In an alternative embodiment, the optical hold unit (200) includes an optical modulator (108) that has an electrical input, an optical input, and an optical output. An optical resonator (202) is also provided and connected to the optical output of the modulator (108).

Abstract: A two-way optical communication module includes a main waveguide which is optically coupled to an optical fiber and directs light incident from the optical fiber to a light-receiving element and a sub waveguide which is optically coupled to the side of the main waveguide and directs light emitted from a light-emitting element to the optical fiber so as to carry out an efficient two-way optical communication by using one optical fiber without the necessity for an optical branch device. With this arrangement, it is possible to provide an inexpensive and small-sized two-way optical communication module which readily enables an integration with other elements so as to exhibit suitability for a small-scale network, and to provide a two-way optical communication link which uses the two-way optical communication module.

Abstract: A method of making short length fused fiber optical couplers and couplers made by the method. In a first step, fibers are fused by heating and pulled to form a taper section. Preferably, the fibers are twisted to assure good fusion. After pulling, in a second heating step, heat is applied to a portion of the taper section while the fibers are held stationary. The fibers are not pulled during the second heating step. The coupling ratio is monitored during the second heating step. The coupling ratio changes slowly during the second heating step and the heat is removed shortly before a desired coupling ratio is achieved. The residual heat continues to change the coupling until the desired coupling ratio is achieved. Couplers made according to the present method have a relatively short length. Couplers made according to the present method have a melted zone located in the taper section. The melted zone has a more rounded shape than the taper section due to surface tension.

Abstract: An optical arrangement for full duplexed PON outstation transceivers (single fibber operation) which improves control of optical output power during marshalling by reducing the light level at which closed loop control can be used. The arrangement uses a beam-expanded region incorporating a bulk-optics beam-splitter with a reflective field stop that will tap a higher proportion of the basestation transmitter power when it is operating below lasing threshold and hence has a larger beam size than when operating above threshold.

Abstract: A bidirectional waveguide tap is disclosed. The tap comprises an appropriately blazed grating in the waveguide, with coupling means in optical co-operation with the waveguide causing transfer of light from a guided mode in the waveguide to a radiation mode. Radiation mode light of a given wavelength and propagation direction is brought to a focus on a predetermined region of utilization means, e.g., an array of photosensors.

Abstract: An improved optical fiber device includes a length of optical fiber having a longitudinally tapered region for causing a portion of light signals guided by the fiber to emerge outside of the fiber. The tapered region is surrounded by a coating that operates on the portion of the light signals emerging from the fiber to modify their propagation properties. The tapered optical fiber device can be used in an optical fiber system which includes at least one source of light signals, wherein the optical fiber device is disposed in the path of light signals from the source.

Abstract: The device is formed on a silicon-on-insulator chip (which comprises a layer of silicon (1) separated from a substrate (3) by an insulator layer (2)) and comprises an integrated waveguide (4) formed in the silicon layer (1) and a reflective facet (6) formed in a recess in the silicon layer (1). The facet (6) is positioned to redirect light in a desired direction. The waveguide (4) and facet (6) are both formed in the silicon layer (1) so their positions can be defined by the same lithographic steps so they are automatically aligned with each other.

Abstract: A system and associated method for use in a fiber administration system that establishes optical communication links. The system includes an optical tap that is disposed in each optical fiber pathway contained within the optical communication links. The optical taps are contained within modules that can be selectively added or removed from a shelf casing that is sized to fit within the framework of the fiber administration system. An optical switch is present in each shelf casing that holds the tap modules. The optical switch is connected to each of the optical taps on its shelf and receives the tapped optical signal provided by the optical taps. An optical signal analyzer is provided within the framework of the fiber administration system. The optical signal analyzer is interconnected with the optical switches on each shelf that contains a tap module. The optical switches selectively interconnect the optical signal analyzer to any of the optical taps.

Abstract: An optical branching device includes a main waveguide and a branching waveguide. A portion of the main waveguide is bent and the branching waveguide is placed close to the bent part of the main waveguide. The branching waveguide has a taper structure such that a width of the branching waveguide is gradually decreased in a propagation direction of light. A central axis of the branching waveguide is tilted from a line extended from a straight part of the main waveguide toward the direction X, or the bending direction of the main waveguide. An input end of the branching waveguide has a normal vector tilted from the central axis of the branching waveguide toward the direction Y, an opposite direction of the bending direction of the main waveguide. With above-mentioned structures, light radiated from the bent part of the main waveguide can be launched into the input end of the branching waveguide and transmitted through the branching waveguide efficiently.

Abstract: A device for tapping into and removing a fraction of the light transmitted by a homogeneous sheathed light conducting and transmitting and conveying light pipe. The device is a transparent probe having a conical point for penetrating the sheath of the light pipe and embedding in the core and an external portion which resides outside the sheath for dissipating of transmitting the light abstracted from the core.

Abstract: In accordance with the present invention, an optical fiber communications system is provided with an adaptive data equalizer to correct for linear disortion of signals transmitted over optical fibers. A feedback signal from a receiver is used to custom tailor the spectral profile of a launched pulse to thereby minimize the distortion of a received pulse. The system uses optical taps for feedback control in order to adapt to changing conditions in the fiber path.

Abstract: An optical tap is disclosed that may be utilized with bulk optic devices. The optical tap utilizes any pre-existing reflected optical signal that is present in the conventional bulk optic device. The tap includes a beveled fiber stub that is inserted in the path of the reflected optical signal and thus captures this reflected signal, where the bevel is utilized to allow for the reflected signal to be re-directed through the fiber stub. A convention photodetector is coupled to the fiber stub and used to generate an electrical control signal from the captured reflected optical signal.

Abstract: The subject matter is directed to a parallel array of optical amplifiers and is also directed to equally sharing the optical power supplied by a plurality of optical pumps among the array of optical amplifiers such that if one of the pumps fails the power outputted by the remaining pumps is still equally shared among the array of optical amplifiers.

Abstract: A dispersive optical waveguide tap comprises a blazed refractive index grating in the core of the waveguide, coupling means, focusing means and utilization means. The grating is selected such that guided mode light of predetermined wavelength will, in the absence of the coupling means, be directed into one or more cladding modes of the waveguide. The presence of the coupling means, in optical co-operation with the waveguide, changes the guiding conditions such that the cladding modes are substantially eliminated from a portion of the waveguide that includes the cladding, whereby the grating directs the guided mode light into one or more radiation modes. The blaze angle typically is .ltoreq.15.degree.. The focusing means serve to bring the radiation mode light substantially to a focus in at least one dimension, the focal point (or line) depending on the wavelength of the light.

Abstract: An optical waveguide of an optical deflector comprising a planar optical waveguide or an optical fiber type optical waveguide is cut while perpendicularly pressing a blade having a blade tip with an angle of inclination against the optical waveguide at a desired location thereof to form an oblique end face serviceable as an oblique end face mirror.

Abstract: This invention provides the gain equalizer positioned to an optical amplifying transmission line for equalizing gains of said optical amplifying transmission line, comprising a plurality of first optical filters varying transmittance periodically in at least predetermined wavelength range, and one or more second optical filters that their transmittance peaks at a wavelength substantially coinciding to the predetermined transmittance bottom wavelength of the first optical filters and decreases in a predetermined range at both side of the predetermined transmittance bottom wavelength.

Abstract: An optical coupler having a substrate; an optical waveguide provided on the substrate; a multimode fiber optically coupled with the optical waveguide; and a single mode fiber optically coupled with the optical waveguide, the optical waveguide provided on the substrate having a multimode waveguide and a plurality of single mode waveguides, the multimode waveguide being optically coupled with the multimode fiber, the single mode waveguide being optically coupled with the single mode fiber. The above constitution can suppress the creation of branch loss.

Abstract: A confocal imaging system using optical fibers is provided which has a flexible near confocal optical transmission means having a light collection end adjacent to a light collection of the confocal optical transmission means and adapted to transmit only near confocal light emerging from points in the object located within a range of distances above and below the focal plane, in such a manner that a selected portion of the near confocal light emerging from greater than any selected distance within the range is substantially separable from the remainder. The system also has variable selection means to exclude from detection the selected portion.

Abstract: An optical interface device for extracting, inserting and passing light transmitted bi-directionally on one or more fiber optic line, comprises: a first optical coupler for receiving light to be inserted onto or extracted from the fiber optic line; and a fiber optic-line, optical coupler, coupled to the fiber optic line and to the first optical coupler, for passing light on the fiber optic line, for receiving light from the first optical coupler to be inserted onto the fiber optic line and transmitting said received light in opposite directions on the fiber optic line, and for extracting light from opposite directions on the fiber optic line and transmitting said extracted light to the first optical coupler.

Abstract: In accordance with the invention, light is coupled from a plurality of semiconductor emitters to a cladding-pumped fiber via tapered fiber bundles fusion spliced to the cladding-pumped fiber. Individual semiconductor broad stripe emitters can be coupled to individual multimode fibers. The individual fibers can be bundled together in a close-packed formation, heated to melting temperature, drawn into a taper and then fusion spliced to the cladding-pumped fiber. Advantageously, the taper is then overcoated with cladding material such as low index polymer. In addition, a fiber containing a single-mode core can be included in the fiber bundle. This single-mode core can be used to couple light into or out of the single-mode core of the cladding-pumped fiber.

Abstract: An optical coupler is formed by a GRIN lens having an axis and an optical medium contiguous to the GRIN lens but having an index of refraction that is different from that of the lens. An input optical fiber carries an input optical signal along a path substantially parallel to the axis of the lens but is offset from its axis. The lens collimates the input optical signal into a beam that impinges on the interface between the lens and the optical medium at a small angle. Fresnel reflection of the collimated beam at such interface is focused by lens to an output optical path also substantially parallel to the axis of the lens but at the same offset to the axis from the input optical path. The tapping percentage can be controlled by choosing an optical medium having the desired index of refraction. Additional interfaces can be formed between the optical medium and additional media, such as a thin glass disk for additional Fresnel reflections that are also coupled to the same output fiber.