Abstract: An apparatus includes an N×1 spatial mode multiplexer, an optical source and an optical receiver. The spatial mode multiplexer has N input ports and an output port end-couplable to a multimode optical fiber. The multiplexer is configured to preferentially couple light between individual ones of the input ports and corresponding spatial optical modes of the multimode optical fiber. The optical source is connected to a first one of the input ports to launch an optical probe pulse into the fiber. The optical receiver is connected to electrically analyze an optical signal backscattered from the multimode optical fiber and output by a second one of the input ports in response to the launch of the optical probe pulse into the fiber.

Abstract: A method for transmitting optical information between an emitter station and a receiving station via a multi-mode optical wave guide uses a wave length multiplex method. Several optical emitters generate a respective signal for each wave length to be transmitted. The signals are fed to the multi-mode optical wave guide in the form of a number of modes via mode multiplexers and wavelength multiplexers, the multi-mode optical wave guide having its own mode that can propagate within the multi-mode optical wave guide for each mode to be transmitted. After transmission and optionally regeneration and/or amplification of the signal via the multi-mode optical wave guide, the transmitted signals are broken down via the wavelength multiplexer into groups of signals having the same wavelength and via the mode demultiplexer into signals having the same mode. Subsequently, the interference signals are extracted from the transmitted demultiplexed signals.

Abstract: A leaky travelling wave array of optical elements provide a solar wavelength rectenna.

Abstract: A system, apparatus and method for providing controlled launch conditions to an optical light source comprises adjustable fiber bending/deforming apparatus to allow adjustment of the device such that multimode launch conditions can be accurately controlled.

Abstract: An active device for dynamic control of lightwave transmission properties has at least one photonic crystal waveguide that has anti-reflection photonic crystal waveguides with gradually changed group refractive indices at both input and output side. An alternating voltage or current signal applied to two electrically conductive regions changes the refractive indices of the photonic crystal materials, introducing a certain degree of blue-shift or red-shift of the transmission spectrum of the photonic crystal waveguide. The output lightwave with frequency close to the band-edge of the photonic crystal waveguide is controlled by the input electric signal. Devices having one or more such active photonic crystal waveguides may be utilized as an electro-optic modulator, an optical switch, or a tunable optical filter.

Abstract: The present invention relates to an apparatus for producing optical pulses of a desired wavelength. The apparatus includes an optical pulse source operable to generate input optical pulses at a first wavelength. The apparatus further includes a higher-order-mode (HOM) fiber module operable to receive the input optical pulses at the first wavelength, and thereafter to produce output optical pulses at the desired wavelength by soliton self-frequency shift (SSFS). The present invention also relates to a method of producing optical pulses having a desired wavelength. This method includes generating input optical pulses using an optical pulse source, where the input optical pulses have a first wavelength and a first spatial mode.

Abstract: A transceiver for use in a bidirectional optical communication link over a multimode channel is provided. The transceiver includes a single transverse mode light source in a transmitter. A waveguide or fiber based bidirectional coupler projects the transmitter mode to the high modes of the multimode channel. A detector coupled to predominantly all the modes of the channel via the waveguide or fiber based bidirectional coupler.

Abstract: A light source and a waveguide are mounted on a recording head slider. Light rays are emitted from the light source into the waveguide. The waveguide may include two core layers for light ray transmission. The first core layer enhances light coupling efficiency from the light source to the second core layer. The second core layer transforms a profile of the light. The waveguide may include a tapered portion with a narrow opening near the light source and a wider opening near the tapered portion exit. The light rays passing through the waveguide may be directed toward a collimating mirror. The collimating mirror makes the light rays parallel or nearly parallel and re-directs the light rays to a focusing mirror. The focusing mirror focuses the collimated light rays to a spot on a magnetic media disc.

Abstract: An apparatus includes a multi-mode optical fiber having a selected plurality of optical propagating modes. The selected plurality may include only a proper subset of or may include all of the optical propagating modes of the multi-mode optical fiber. Each optical propagating mode of the selected plurality has a group velocity that varies over a corresponding range for light in, at least, one of the optical telecommunications C-band, the optical telecommunications L-band, and the optical telecommunications S-band. The ranges corresponding to different ones of the modes of the selected plurality are non-overlapping. The ranges of a group velocity-adjacent pair of the ranges are separated by a nonzero gap of less than about 10,000 meters per second.

Abstract: An optical interconnect includes a set of splitters. Each splitter includes a source waveguide, a reflection waveguide, an output waveguide, and a partially reflective mirror element with a reflective coating. The source waveguide and the reflection waveguide are optically coupled to the partially reflective element. A photonic signal from the source waveguide is partially reflected off the reflective coating as a reflected signal into the reflection waveguide. The output waveguide is optically coupled to the opposite surface and configured such that a non-reflected portion of the photonic signal propagates into the output waveguide. The reflective coating includes a reflected surface area interfacing with the photonic signal form the source waveguide, and power of the non-reflected portion is a function of the reflective surface area interfacing with source waveguide.

Abstract: An optical fiber link suitable for use in a mode division multiplexing (MDM) optical transmission system is disclosed. The link has a first optical fiber having a core which supports the propagation and transmission of an optical signal with X LP modes at a wavelength of 1550 nm, wherein X is an integer greater than 1 and less than or equal to 20, the first fiber having a positive differential mode group delay between the LP01 and LP11 modes at a wavelength between 1530-1570. The link also has a second optical fiber having a core which supports the propagation and transmission of an optical signal with Y LP modes at a wavelength of 1550 nm, wherein Y is an integer greater than 1 and less than or equal to 20, said optical fiber having a negative differential mode group delay between the LP01 and LP11 modes at a wavelength between 1530-1570.

Abstract: A base device has a first waveguide positioned on a first base. The waveguide is at least partially defined by a ridge extending away from the first base. An auxiliary optical device has a second waveguide positioned on a second base. The second optical device is immobilized on the base device such that the second waveguide is between the first base of the first optical device and the second base of the auxiliary device. The first waveguide is optically aligned with the second waveguide such that the first waveguide and second waveguides can exchange optical signals.

Abstract: An embodiment of an apparatus includes an optical fiber for which a complete orthogonal basis of propagating modes at an optical telecommunication frequency includes ones of the propagating modes with different angular momenta. The optical fiber has a tubular optical core and an outer optical cladding in contact with and surrounding the tubular optical core. The tubular optical core has a larger refractive index than the optical cladding. The tubular optical core is configured such that those of the propagating modes whose angular momenta have the lowest magnitude for the propagating modes have substantially the same radial intensity profile.

Abstract: An apparatus includes an optical fiber having a plurality of optical cores therein. Each optical core is located lateral in the optical fiber to the remaining one or more optical cores and is able to support a number of propagating optical modes at telecommunications wavelengths. Each number is less than seventy.

Abstract: A waveguide cores consisting of a subwavelength grating permits transmission of light without diffraction in a discontinuous manner, wherein the energy is provided by field hopping between subwavelength material segments of higher index. The use of alternating segments permits design of waveguides having desired effective index, mode confinement factor, birefringence, polarization mode or mode dispersions, polarization dependent loss, thermal sensitivity, or nonlinear optical coefficient. An optical system comprises a waveguide having such a core, clad on at least one side, extending between two ends, and wavelength-limiting optical components in optical communication with the ends.

Abstract: A high power fiber laser system emitting a substantially diffraction limited beam with a Gaussian intensity profile includes a single mode (“SM”) neodymium fiber pump source outputting a SM pump light; a seed laser operative to emit a SM signal light at a wavelength greater than that of the pump light; a SM DWM receiving and multiplexing the SM pump and signal lights. The disclosed system further includes a booster fiber amplifier which is configured with a frustoconically-shaped ytterbium (“Yb”) doped core receiving the pump and signal lights and configured with a small diameter input end which supports only a SM and a large diameter output end which is capable of supporting the SM and high order modes (:HOM”). The booster further has a cladding surrounding and coextending with the core, the core being configured for having intensity profiles of respective SMs of pump and signal lights overlap one another so that an overlap integral substantially equals to one (1) along an entire length of the core.

Abstract: An integrated optical coupler including in the medium separating a first integrated waveguide from a second substantially parallel integrated waveguide, a succession of strips parallel to one another and orthogonal to the general direction of the waveguides, said strips being made of a material having an absorption preventing the propagation of an electromagnetic wave across its volume, and having: a length H equal to k?/2nmedium, where k is an integer, ? is the central wavelength used, and nmedium is the optical index of the medium between the waveguides; a period P smaller than ?/2nmedium; and ends at a distance shorter than ?/10 from the waveguides.

Abstract: Disclosed is an optical conversion element capable of highly efficient optical coupling between a silicon waveguide and a general single-mode optical fiber only by butt-coupling without requiring anti-reflective coating. One embodiment is an optical conversion element that includes a waveguide structure and converts a mode field of guided light and is characterized in that at least a dual core is included, an innermost core of the dual core is a silicon inverse tapered thin wire core, a first outer core is a forward tapered ridge core having a ridge structure formed of an oxide film with only width of the ridge core changing. The first outer core is positioned on a narrow width side of the innermost core.

Abstract: An optical waveguide and a bi-directional transceiver are provided. A single mode optical fiber has one end coupled to one end of a hollow optical fiber and an opposite end having a slope plane, thereby separating optical signals travelling in opposite directions from each other. Manual alignment for an optical system is easily realized without the need for additional optical elements, so that the light transmission/reception performance of the optical waveguide is improved and the structure of the optical waveguide is smaller.

Abstract: Optical interfaces that may be employed between large-core optical fibers and chip-scale optoelectronic devices. Described herein are couplers that improve the tolerance of misalignment when a single mode (SM) fiber is used as waveguide input. This enables the possibility of passive/automatic alignment and therefore reduces the production cost. The coupler also serves as a spot-size converter that reduces the spot size and is suitable for applications where a waveguide mode with small cross-section area is of particular importance. One such example can be a waveguide-based SiGe or III-V semiconductor photodetector in which the vertical size of its waveguide mode should be as small as few microns.

Abstract: A conically tapered optical fiber with a small half-angle ? (e.g., less than 10?2) has been found able to support whispering gallery mode (WGM) resonances and can therefore be used to form a high-Q cavity. This finding has led to the ability to measure angstrom-level variations in the radius of an optical fiber by viewing the resonance spectrum at various locations where a sensor contacts an optical fiber being measured. An evaluation process is proposed where a microfiber sensor is brought into contact with a target fiber and the created WGM resonance is measured so that location radius variation can be characterized. The sensor is then removed from the target fiber and re-positioned to contact the fiber to another location to repeat the evaluation.

Abstract: An optical mode transformer comprises a first waveguide including a first core, a first cladding and an end facet configured to be coupled to an optical fiber. A second waveguide comprises a second core and a second cladding, and is arranged with respect to the first waveguide so as to realize an evanescent optical coupling with the first waveguide. The second core comprises a tapered region, in at least a portion of which the evanescent coupling takes place. The first core and the second core are separated by a gap. A first refractive index contrast of the first waveguide is less than a second refractive index contrast of the second waveguide.

Abstract: A multimode interference coupler includes at least one supply waveguide and at least one output waveguide, wherein the coupler has along its longitudinal extent in the direction of the supply waveguide at least one longitudinal section in which the refractive index has a locally oscillating profile in a direction running substantially at right angles to the direction of the supply waveguide. A method for the structural configuration of such a multimode interference coupler.

Abstract: Optical fiber comprises core and a cladding configured to support and guide a fundamental transverse mode, the cladding including (i) an outer cladding having an index nout less than the index n1 of the core, (ii) an inner cladding having an index n2<nout, (iii) a pedestal having an index n4˜nout, (iv) an inner trench disposed between the inner cladding and the pedestal, the inner trench having an index n3<<n4, and (iv) an outer trench disposed between the pedestal and the outer cladding, the outer trench having an index n5<n4 and relatively close to nout. To suppress unwanted HOMs the pedestal is configured to resonantly couple at least one unwanted transverse mode of the core (other than the fundamental mode) to at least one transverse mode of the pedestal. Also described is a modular method of making the optical fiber of silica glass.

Abstract: An arrayed waveguide grating optical multiplexer/demultiplexer according to the present invention including an input channel waveguide, an input slab waveguide, an arrayed waveguide, a polarization dependence eliminating means, an output slab waveguide, a temperature compensating means, and an output channel waveguide is characterized in that the temperature compensating means compensates for the temperature dependence of the optical path lengths in the channel waveguides of the arrayed waveguide, and the polarization dependence eliminating means eliminates the temperature dependence and the polarization dependence of the arrayed waveguide grating optical multiplexer/demultiplexer at the same time.

Abstract: A chiral optical fiber polarizer is provided that is capable of being fabricated in-line along a conventional polarization maintaining fiber having external structural element(s), positioned between two optical fiber portions, and includes a modified central portion with altered fiber cladding interface elements on each side thereof. The modified central portion includes at least one diameter reduced sub-section that allows a light signal to propagate simultaneously in the core and in at least one external structure element, and at least one diameter expanded sub-section that allows the light signal to propagate substantially in the core, where the modified central portion is configured to be operable to serve as a polarizer for light signals with linear polarization components.

Abstract: This document provides techniques, apparatus and designs for using electro-optic WGM resonators that support two different families of optical WGM modes with different quality factors in various applications. A radio frequency (RF) resonator is formed on the optical resonator and structured to supply an RF field and spatially overlaps the RF field of the RF resonator with the first and second optical whispering gallery modes to cause RF energy in the RF field at a first RF carrier frequency to couple with the first optical whispering gallery mode and RF energy in the RF field at a second RF carrier frequency to couple with the second optical whispering gallery mode.

Abstract: Optical vector vortex beams may be generated from few-mode or multi-mode optical fiber by introducing linearly or circularly polarized light into the fiber. By adjusting at least one of the polarization of the light, the incident angle of the light coupled into the fiber, and the length of the fiber, one or more vector modes supported by the fiber may be selected. The resulting output from the fiber may be a vortex beam that can be collimated and used for precise manipulation of objects on order of a micrometer or a nanometer in diameter.

Abstract: A system configured to generate an optical beam from a fiber laser is presented. The system includes a fiber gain medium having a core and a cladding, the core being configured to convert radiation from a pump beam into an output beam, the cladding having a mode propagating section and a mode stripping section bounded on a near end and a distal end by the mode propagating section, the mode stripping section of the cladding being configured to scatter excess pump radiation received from the mode propagating section in a substantially outwardly radial direction. The system also includes a rigid support member into which the fiber gain medium is placed, the rigid support member completely encompassing the mode stripping section of the cladding and joined to the fiber at the mode propagating section of the cladding.

Abstract: An optical fiber that is relatively insensitive to bend loss comprises a core region and a cladding region configured to support and guide the propagation of light in a fundamental transverse mode, the cladding region including (i) an outer cladding region having a refractive index less than that of the core region, (ii) an annular cladding pedestal region having a refractive index higher than that of the outer cladding region and comparable to that of the core region, and (iii) an annular cladding inner trench region disposed between the core region and the pedestal region, the inner trench region having a refractive index less than that of the outer cladding region. In one embodiment, the fiber also includes a (iv) an annular cladding outer trench region disposed between the pedestal region and the outer cladding region, the outer trench region having a refractive index less than that of the outer cladding region.

Abstract: The present invention relates to a light modulating device, comprising a SLM and a pixelated optical element, in which a group of at least two adjacent pixels of the SLM in combination with a corresponding group of pixels in the pixelated optical element form a macropixel, the pixelated optical element being of a type such that its pixels comprise a fixed content, each macropixel being used to represent a numerical value which is manifested physically by the states of the pixels of the SLM and the content of the pixels of the pixelated optical element which form the macropixel.

Abstract: An optical adapter includes an optical coupler, a plurality of fiber optic cables and an optical wavelength conversion device. The optical coupler is operable to receive a plurality of multi-mode single-wavelength optical signals having the same frequency. The plurality of fiber optic cables are arranged in parallel and each have a first end connected to the optical coupler and the other end is coupled to the optical wavelength conversion device. The optical wavelength conversion device is operable to optically convert between the plurality of multi-mode single-wavelength optical signals at the same frequency and a plurality of single-mode optical signals at different frequencies and multiplex the plurality of single-mode optical signals at the different frequencies onto a single-mode multi-wavelength optical waveguide. A corresponding optical adapter is provided for the receive side.

Abstract: An optical fiber-type optical filter includes: two fiber regions, namely, the first and second PBGF regions, each of which includes: a core section extending in a waveguide direction of incident light; and a clad section extending in the waveguide direction and surrounding the core section, wherein the clad section includes a plurality of high rods which have a refractive index higher than that of a base material of the clad section, extend in the waveguide direction, and are arranged periodically in a cross section perpendicular to the waveguide direction, and a light loss region between mutually-facing end surfaces of the first and second fiber regions, for coupling a radiation mode with a waveguide mode in which light intensity is observed in the high refractive-index sections in the clad section.

Abstract: Various embodiments include large cores fibers that can propagate few modes or a single mode while introducing loss to higher order modes. Some of these fibers are holey fibers that comprising cladding features such as air-holes. Additional embodiments described herein include holey rods. The rods and fibers may be used in many optical systems including optical amplification systems, lasers, short pulse generators, Q-switched lasers, etc. and may be used for example for micromachining.

Abstract: A nanoscale serpentine ribbon is used to produce electromagnetic radiation by accelerating charge carriers as constrained along a serpentine path defined by the ribbon so that curve portions of the ribbon promote acceleration-induced emission of electromagnetic radiation by the charge carriers.

Abstract: An optical link may include a main optical waveguide; N sub-optical waveguides, where N is a natural number; N mode couplers, each configured to perform a mode coupling operation between the main optical waveguide and a respective one of the N sub-optical waveguide; and an optical wavelength filter connected to an output terminal of the main optical waveguide and an output terminal of each of the N sub-optical waveguides. A memory system may include a memory device, a memory controller, and the optical link. A data processing system may include the memory system and a central processing unit connected to the memory system through a bus.

Abstract: An optical coupler for coupling a multimode waveguide and two or more other waveguides. In one embodiment, the optical coupler has an optical phase mask disposed between the multimode waveguide and two or more other waveguides. The optical phase mask imposes on the light passing therethrough a spatial phase pattern that causes selective mode-to-waveguide coupling between the multimode waveguide and the other waveguides. The optical coupler can be used, e.g., in transmitters and receivers of optical transverse-mode-multiplexed signals.

Abstract: A waveguide coupler includes a first waveguide and a second waveguide. The waveguide coupler also includes a connecting waveguide disposed between the first waveguide and the second waveguide. The connecting waveguide includes a first material having a first index of refraction and a second material having a second index of refraction higher than the first index of refraction.

Abstract: An optical fiber that is relatively insensitive to bend loss comprises a core region and a cladding region configured to support and guide the propagation of light in a fundamental transverse mode, the cladding region including (i) an outer cladding region having a refractive index less than that of the core region, (ii) an annular cladding pedestal region having a refractive index higher than that of the outer cladding region and comparable to that of the core region, and (iii) an annular cladding inner trench region disposed between the core region and the pedestal region, the inner trench region having a refractive index less than that of the outer cladding region. In one embodiment, the fiber also includes a (iv) an annular cladding outer trench region disposed between the pedestal region and the outer cladding region, the outer trench region having a refractive index less than that of the outer cladding region.

Abstract: A monolithic fiber has a double bottleneck-shaped core configured with opposite uniformly configured end regions, frustoconical transformer regions which run inwards from the respective end regions, and a central uniformly-dimensioned region which bridges the transformer regions. The core is configured as a multimode core or single-mode core and capable of guiding a single transverse mode between the end regions without splice losses.

Abstract: This patent disclosure is based on silicon instead of LiNbO3, waveguide chip. The disclosed silicon-based multi-function integrated-optic chip comprises of unique design and fabrication features onto it. First, a unique polarization-diversity coupler is designed and fabricated to couple the external light into the silicon waveguide structure. Then TE mode is guided into a silicon slab waveguide, but TM mode is confined and diverted 90 degree in a silicon carbide structure till the chip edges for TM-mode suppression. Second, a unique two-step (vertical and lateral) taper waveguide region is designed and fabricated to bridge the polarization-diversity coupler output with the input of a multi-mode interferometer (MMI) splitter for power loss reduction. In this configuration, MMI may be a 1×2 or 2×2 structure to divide the input TE mode into a 50/50 splitting ratio output to form a Y-junction.

Abstract: Optical waveguides can extend alongside one another in sufficient proximity such that light couples between or among them as crosstalk. The electromagnetic field associated with light flowing in one optical waveguide can extend to an adjacent optical waveguide and induce unwanted light flow. The optical waveguide receiving the crosstalk can comprise a phase shifting capability, such as a longitudinal variation in refractive index, situated between two waveguide lengths. Crosstalk coupled onto the first waveguide length can flow through the refractive index variation, be phase shifted, and then flow onto the second waveguide length. The phase shifted crosstalk flowing on the second waveguide can meet other crosstalk that has coupled directly onto the second waveguide segment. The phase difference between the two crosstalks can suppress crosstalk via destructive interference.

Abstract: An apparatus is provided comprising a small form factor pluggable module having an optical connector configured to be coupled to a plurality of transmit and receive single mode optical fibers and an optical transmitter comprising a plurality of uncooled laser diodes configured to transmit optical signals to a plurality of transmit single mode optical fibers via the optical connector. The small form factor pluggable module is a quad small form factor pluggable plus (QSFP+) 40GBASE-SR4 module that has been converted for use with single mode fibers by substituting their vertical-cavity surface emitting laser diodes (VCSEL) with longer range uncooled laser diodes. Example replacement lasers may include uncooled Fabry-Perot (FP) laser diodes or Distributed Feedback (DFB) laser diodes. To connect the module to lower grade fibers, a single mode-to-multimode mode conditioning patch cord is provided with a plurality of inline physical offsets, one for each pair of fibers.

Abstract: A method and an apparatus are provided for launching light into an entrance facet of a multimode optical fiber (MMF) of an optical link in a way that excites one or more higher-order Hermite Gaussian (HMG) mode groups in the MMF. Exciting higher-order HMG mode groups in the MMF increases the bandwidth of the link while also providing reduced modal noise. In addition, selectively exciting one or more higher-order HMG mode groups in the MMF ensures that the launch will provide desirable results even in cases where the connector that connects the end of the MMF to the optical transceiver or transmitter is offset with respect to the receptacle of the optical transceiver or transmitter. This feature allows for greater manufacturing tolerances when manufacturing the connectors and receptacles because precise alignment between them is not critical to achieving a successful launch.

Abstract: An optical fiber that is relatively insensitive to bend loss comprises a core region and a cladding region configured to support and guide the propagation of light in a fundamental transverse mode, the cladding region including (i) an outer cladding region having a refractive index less than that of the core region, (ii) an annular cladding pedestal region having a refractive index higher than that of the outer cladding region and comparable to that of the core region, and (iii) an annular cladding inner trench region disposed between the core region and the pedestal region, the inner trench region having a refractive index less than that of the outer cladding region. In one embodiment, the fiber also includes a (iv) an annular cladding outer trench region disposed between the pedestal region and the outer cladding region, the outer trench region having a refractive index less than that of the outer cladding region.

Abstract: An apparatus that comprises an optical-mode-converter. The optical-mode-converter includes a optical waveguide including a segment directly located on a substrate and a cantilevered segment located over said substrate and separated from said substrate by a cavity, and, said cantilevered segment includes a core surrounded by a cladding. The optical-mode-converter also includes a dielectric material filling said cavity and contacting said cantilevered segment over said cavity, wherein said dielectric material has a refractive index that is less than a refractive index of said cladding and that is no more than about 20 percent less than said refractive index of said cladding.

Abstract: An optical fiber coupler array capable of providing multiple low loss, high coupling coefficient interfaces between a predetermined number of low numerical aperture optical fibers and an optical waveguide device with at least a corresponding number of waveguide interfaces. The novel coupler array includes a plurality of coupler inner cores and a plurality of corresponding coupler outer cores, within a medium surrounding each plural outer core, and also includes a first end for interfacing with plural optical fibers and a second end for interfacing with a plurality of waveguide interfaces of an optical waveguide device. The sizes of the inner and outer cores are gradually reduced from the first end to the second end in accordance with at least one predetermined reduction profile.

Abstract: An active device for dynamic control of lightwave transmission properties has at least one photonic crystal waveguide that has anti-reflection photonic crystal waveguides with gradually changed group refractive indices at both input and output side. An alternating voltage or current signal applied to two electrically conductive regions changes the refractive indices of the photonic crystal materials, introducing a certain degree of blue-shift or red-shift of the transmission spectrum of the photonic crystal waveguide. The output lightwave with frequency close to the band-edge of the photonic crystal waveguide is controlled by the input electric signal. Devices having one or more such active photonic crystal waveguides may be utilized as an electro-optic modulator, an optical switch, or a tunable optical filter.

Abstract: An optical coupler is provided. It has a bundle of multimode fibers with a few-mode fiber in its centre. Such bundle is fused at one end which is the output end for the signal that is transmitted by the few-mode fiber. To make the coupler, this output end of the bundle is aligned and spliced with a large area core double clad fiber while preserving the modal content of the feed-through. A method for making such optical coupler is also provided. It includes the steps of bundling a central few-mode fiber with a plurality of multimode fibers and then fusing one end of such bundle and aligning it and splicing with a large core double clad fiber, while preserving fundamental mode transmission from one to the other.

Abstract: An apparatus for transmission of free space optical communication system signals employing a spatially-extended light source and method of using the same. A laser beam source directs an optical signal into a free end of a segment of multimode fiber. As the optical signal passes through the segment of multimode fiber, the optical signal is converted into a mode-scrambled optical signal. This mode-scrambled signal may then be used as a spatially-extended light source that is directed outward as an optical beam through the use of a collimating lens.