Showing papers on "Photonic-crystal fiber published in 1991"

Tunable gain equalization using a Mach-Zehnder optical filter in multistage fiber amplifiers

Abstract: Tunable signal gain equalization is demonstrated in three-stage Er/sup 3+/-doped fiber amplifiers using a waveguide type Mach-Zehnder (MZ) optical fiber. A 29-channel multiplexed system is examined where signal wavelengths are positioned from 1.548 to 1.555 mu m. By adjusting the MZ transmittance with the external control current, tunable gain equalization is achieved at the output of each amplifier. >

A single-mode fiber with chromatic dispersion varying along the length

Abstract: A method for fabrication of a novel type of optical fiber with dispersion varying along the fiber length is described. The method takes into account the calculated dependence of fiber dispersion on fiber core diameter for the measured profile of the preform and the desirable dispersion dependence on the fiber length. The main optical parameters of the drawn fiber are theoretically studied and experimentally measured. The fibers are of great interest for nonlinear fiber optics. Such applications of the fibers, such as high-quality soliton pulse compression, soliton pulsewidth stabilization through compensation of losses, and generation of a high-repetition-rate train of practically uninteracting solitons, are considered. >

Miniature Fabry-Perot interferometers micromachined in silicon for use in optical fiber WDM systems

Abstract: The techniques of silicon micromachining have been used to fabricate a second-generation Fabry-Perot interferometer for use in the near-infrared spectral region. These devices provide a sharp optical transmission peak which can be used as wavelength division demultiplexers in optical fiber communications systems. The wavelength tuning and parallelism control of the mirror elements are achieved electrostatically, by varying the voltage between control electrodes. This second-generation device includes a thin, etch-stopped corrugated diaphragm as the suspension for the movable element. >

All fiber, low threshold, widely tunable single-frequency, erbium-doped fiber ring laser with a tandem fiber Fabry-Perot filter

Abstract: An all fiber, widely tunable, single‐frequency, erbium‐doped fiber ring laser was constructed with a threshold pump power as low as 10 mW. Tuning over more than 30 nm was obtained by applying 0 to 17 dc V to an intracavity fiber Fabry–Perot filter. Threshold pump power versus wavelength data showed low variation over the tuning range. Mode hopping suppression with a tandem fiber Fabry–Perot filter is proposed and demonstrated. Stable single‐frequency operation was demonstrated with side mode suppression higher than 35 dB.

Nonlinear refractive index in erbium doped optical fiber: Theory and experiment

Abstract: An intensity-dependent refractive index in erbium doped optical fiber has been observed for the first time. The effect has been observed by an interferometric technique using a two-core fiber. The effect is analyzed theoretically, and the important nonlinear parameters for thin material have been determined and are presented. >

High-power Q-switched erbium-doped fiber laser

Abstract: Rare-earth single-mode fibers are of specific interest in the field of optical communication as lasers or in-line optical amplifiers. High-power erbium-doped fiber lasers, operating in the eye safe wavelength region of 1.5 μm, are attractive not only in fiber communication but also for such applications as range finding.

Passive laser-fiber alignment by index method

Abstract: A method for packaging a laser-fiber module was explored in which the critical laser-fiber alignment is carried out not with the usual active means, i.e., with the laser activated, but by a passive method based on the registration principles of photolithography. The method relies on an index scheme in which fiducial marks are lithographically placed on the laser chip and on a fiber carrier. At 850 nm, using the index technique with cleaved multimode fibers, it was possible to achieve the same laser-fiber coupling efficiency as attained by active alignment; with cleaved single-mode fibers about 80% of the active-alignment coupling efficiency was achieved. >

Hybrid optical fiber and method of increasing the effective area of optical transmission using same

Abstract: A hybrid fiber which, at the operating wavelength, has a desirable fiber dispersion characteristic and a relatively large effective area is provided. Hybrid fibers are constructed in accordance with the principles of the invention by splicing together a fiber with a large effective area but typically unsatisfactory fiber dispersion characteristics to a fiber having excellent dispersion characteristics but a smaller effective area. The resulting hybrid fiber has an increased effective area and desirable fiber dispersion characteristics at the low-loss operating wavelength.

Photorefractive effect in bulk chalcogenide glass and devices made therefrom

Abstract: The photorefractive effect results in a change in the refractive index of bulk chalcogenide glass when it is exposed to certain wavelengths of light, in particular, sub-band-gap light. The effect results in a variety of device structures including a fiber optic faceplate; an optical waveguide; a fiber tap; a lens and a Bragg grating. Methods for fabricating the various devices are described.

Optical fiber electro-optical module

Abstract: OF THE DISCLOSURE An electro-optical module has at least three ports, with at least one port having an active electro-optical device for connection to electrical circuitry and at least one port having an optical port for connection to an optical fiber link. A passive coupler interfaces the various ports. The passive coupler is formed of optical fibers mounted on glass using an adhesive that exhibits refractive index-matching characteristics. The fiber-on-glass coupler is extremely small, allowing for the module to have minimal size. The coupler may be wavelength selective or wavelength insensitive. If a wavelength-selective coupler is utilized, the end surface of an optical fiber is coated with a dichroic filter to provide wavelength sensitivity. An optical fiber adapted to receive light for connection to a detector is selected to be a multi-mode fiber to increase reception of light. The remaining fibers may be single-mode fibers.

Erbium-doped fiber amplifier pumped at 1.48 mu m with extremely high efficiency

Abstract: An erbium-doped fiber amplifier pumped at 1.48 mu m with extremely high efficiency has been developed. The fiber has a relative refractive index difference of 2.0% and Er/sup 3+/ ions and alumina are doped only in a limited area of the core. A slope efficiency of 86% and a gain coefficient of 6.3 dB/mW have been achieved by 1.48 mu m pumping along with excellent spectral signal output performance. In spite of its small mode-field diameter, it is possible to fusion-splice the fiber to standard dispersion-shifted fibers with low loss due to diffusion of fluorine dopant in the classing. >

Intrinsic fiber-optic sensors

Abstract: The basic theory of optical sensors is explained. State-of-the-art fiber-optic sensors are examined. There are two types of fiber-optic sensors: extrinsic and intrinsic. With extrinsic sensors, light leaves the fiber and is blocked or reflected before going back into the fiber-optic system. Extrinsic sensors are, in general, analogous to photoelectric controls with the potential problems of being affected by dirt, dust, vibration, and alignment. Intrinsic sensors avoid these problems by changing the light while it is still inside the fiber. Five types of intrinsic sensors are described. The advantages and disadvantages of intrinsic fiber-optic sensors are given. Present and future applications of intrinsic fiber-optic sensors are described. >

Optical fiber amplifier and coupler

Abstract: Disclosed is a fiber amplifier system in which a gain fiber is operatively combined with a fiber optic coupler having first and second coupler optical fibers. The coupler fibers are fused together along a portion of their lengths to form a wavelength dependent coupling region whereby most of the light power of a wavelength .lambda.s couples between them, and most of the light power of a wavelength .lambda.p that is introduced into the first fiber remains in it. The mode field diameter of the first coupler fiber is substantially matched to that of the gain fiber and is smaller than that of the second coupler fiber. One end of the first coupler fiber is spliced to the gain fiber. Atransmission fiber is spliced to the second coupler fiber, and a laser diode introduces pumping light of wavelength .lambda.p to the first coupler fiber. The fiber optic coupler preferably includes an elongated body of matrix glass through which the first and second coupler fibers extend. The matrix glass has a refractive index n3 that is lower than that of the fiber claddings. The fibers are fused together along with the midregion of the matrix glass, the fiber cores being more closely spaced at the central portion of the midregion than at the body endfaces, thereby forming the coupling region.

Photorefractive optical fiber

Abstract: Germanosilicate optical fiber having substantially higher GeO/GeO 2 ratio than conventional comparison-fiber is disclosed. The fiber has a loss at wavelength of 330 nm of at least 30 db/m.mole % GeO 2 . Such fiber can be advantageously used for making in line photorefractive Bragg gratings and other photorefractive fiber components. Fiber according to the invention can be produced by an inside deposition process (e.g., MCVD, PCVD), by an outside deposition process (e.g., VAD, OVD), or even a sol/gel process, and embodiments of the general method of making fiber according to the invention are disclosed.

Apparatus including concave reflectors and a line of optical fibers

Abstract: An optical system comprising reflectors of elliptical and circular cross section for efficiently coupling radiation from a large scale radiation source such as a light bulb into an optical fiber bundle.

Fiber Optics: Communication and Other Applications

Abstract: Introduction to fiber optics physics of light principles of fiber optics fiber characteristics optical fibers principles of fiber optic communication modulation and multiplexing fiber optic components optical sources for communication optical detectors the fiber optic communication system applications, appendixes, table of constants and units, energy gap eg. for various substances, laser safety.

Reflective evanescent fiber-optic chemical sensor

Abstract: A fiber-optic sensor is formed from three optical fibers. The distal ends of the fibers are optically linked by bonding their cores and directing their ends to mirrors. A portion of one of the fibers near the bonded point is exposed directly to the fluid to be sensed. The transmission characteristics of this fiber, the signal fiber, is then affected by the chemical constituents of the fluid. Light directed into the proximal end of one of the other fibers, the input fiber, is split between the signal fiber and the remaining fiber, the reference fiber. The ratio of the light in the signal fiber to the light in the reference fiber provides an indication of the chemical constituents that minimizes errors introduced by factors such as bends in the fibers and temperature.

Multimode fiber sensor system with sensor fiber coupled to a detection fiber by spacer means

Abstract: A fiber-optic sensor device utilizing modal interference in a multimode optical sensor fiber, having output light from the sensor fiber coupled to an axially separated detection lead fiber, and having light from the detection lead fiber coupled to a substantially uniform light detector.

Efficient integrated Nd/sup 3+/ fiber laser

Abstract: An efficient, integrated, low-threshold, tunable, laser-diode pumped Nd/sup 3+/ fiber laser has been fabricated. The integrated fiber laser incorporated two highly reflecting intracore Bragg reflectors, which were formed holographically by transversely exposing the core to a UV two-beam interference pattern. When the fiber laser was diode pumped, a maximum output of 2.3 mW was observed at 1.088 mu m, and a slope efficiency of 41% was measured. >

Coupling of optical fiber to optical waveguide device

Abstract: A method of coupling an optical fiber with an optical waveguide device at an elevated temperature, through a symmetrical opening, in the presence of a liquid photohardenable composition, in order to extend the operability of the coupling over a wide range of temperatures.

High-Power Transmission Through Step-Index, Multimode Fibers

Abstract: Motivated by interest in optical firing systems for initiating explosives laser-induced damage thresholds have been investigated in step-index multimode fibers having pure fused silica cores. A compact multimode Nd/YAG laser operated at a pulsewidth of 16 ns was used for the experiments. The focusing geometry for introducing the beam into the fiber was chosen to avoid damage along the core/cladding interface as observed in previous studies. Five lots of twenty fibers each were tested with polishing steps varied between successive lots to produce improved fmishes on the fiber end surfaces. Each fiber was subjected to a sequence of progressively increasing energy densities up to a value more than 80 J/cm2. Initial damage was monitored by observing scattered HeNe laser light from the fiber faces using magnified video cameras. The majority of the fibers damaged initially at the rear fiber face once a " laser conditioning" process at the front fiber face was completed. In this process a visible plasma was generated at the front face for one or more laser shots. Rather than produce progressive damage at the front surface this process apparently improved the surface finish in nearly all cases resulting in improved resistance to damage. Other modes of damage along the fiber length were observed either at locations of handling stresses or at the location of highest static tensile stress corresponding to the fiber's minimum bend radius.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

0.98- mu m strained quantum well lasers for coupling high optical power into single-mode fiber

Abstract: An investigation of epitaxial-layer structures has yielded narrow ridge waveguide structure lasers capable of coupling high optical power into single-mode fiber (SMF). An optical power of well over 60 mW in SMF was obtained for a 2- mu m-wide ridge waveguide laser with a guided separate-confinement-heterostructure (SCH) epitaxial structure. Calculated results indicate that the stringent limit imposed on 0.98- mu m wavelength detuning is relaxed for such high optical power coupled into a SMF. The 0.98- mu m strained-quantum-well lasers thus show considerable promise as a practical low-noise pumping source for Er-doped optical-fiber amplifiers. >

Flexible optical graded-index profile fiber for transmission of laser radiation with high output with substantial preservation of the mode structure

Abstract: A flexible optical multimode fiber for the transmission of laser radiation with high radiation output is described in which the mode structure of the radiation is substantially preserved. The fiber is especially suited for transmitting radiation in Gaussian modes. The dimensioning of the fiber is indicated, and a composition for fibers for the spectral region of about 250 nm to 2 microns is proposed.

Connection loss reduction by thermally-diffused expanded core fiber

Abstract: Connection loss reduction in ten fiber connectors prepared by the thermally diffused expanded core (TEC) method has been confirmed. The mode field diameters (MFDs) of conventional single mode (SM) fibers were expanded from 9.8 to 13 mu m by thermal treatment considering the influence of loss increase due to fiber axis misalignment. An average connection loss of 0.15 dB for 4-SM-fiber connectors was realized, which was improved by 0.22 dB compared with previous value of 0.37 dB without thermal treatment. The TEC method promises to reduce the coupling loss, which is caused by lateral offset of multifiber connectors, fiber/LD modules, and fiber/waveguide device modules. >

Properties of silver halide core-clad fibers and the use of fiber bundle for thermal imaging

Abstract: Optical infrared (IR) fibers with core-clad structure are of great importance because they have better qualities than unclad fibers for most IR fiber applications, especially in CO2 laser power delivery and radiometry. We have fabricated core-clad polycrystalline silver halide optical fibers with different compositions and core diameters, and although their loss is still higher than that of unclad fibers, they already have many advantages and new capabilities. The behavior of the scattering loss along these fibers and other optical properties was measured and compared with that of unclad silver halide fibers. We show that the higher loss of clad fibers results mainly from excessive scattering. The improvement in the process of fabricating clad fibers enabled the production of new elements such as single-mode fibers (SMFs) and fiber bundles for thermal imaging.

Variable-ratio tap for plastic optical fiber

Abstract: A variable-ratio tap is developed by changing the bending radius of a plastic optical fiber. When a plastic fiber is bent over a small radius, the core modes of the fiber are converted into the cladding modes, which can be extracted through material having a suitable refractive index. The transmission characteristics of the variable-ratio tap are investigated using the ray tracing technique governing the quasiskew rays propagating through a multimode fiber.

Manufacturing method of an optical fiber coupler

Abstract: The present invention provides a manufacturing method for an optical fiber coupler, the optical characteristic of which is less dependent on wavelength. In the manufacturing method, a coupling region is formed by fusion-bonding and extending parts of a plurality of optical fibers arranged to be closely touching each other. At least one of the optical fibers is extended at a speed different from that of the other optical fibers when a low-temperature heat source is applied to soften the optical fibers. When the temperature of the low-temperature heat source is raised to form a high-temperature heat source, the extended parts of the closely touching optical fibers are fusion-bonded. When the temperature of the high-temperature heat source is then lowered to form a low-temperature heat source again, the fusion-bonded part can be extended further. In one embodiment, the fibers are twisted before fusion bonding the fibers.

Twin-core optical fiber with large core ellipticity.

Abstract: The first (we believe) twin-core optical fiber with large core elipticity has been fabricated, and its significant polarization dependent coupling properties have been demonstrated.

Method of preparing an optical fiber for use in an interferometer system

Abstract: A method of preparing an optical fiber for user in an interferometric system includes introducing a portion of a single-mode, polarization preserving fiber having an asymmetric cladding into a medium capable of etching away the cladding and withdrawing the portion from the medium after sensing an optical intraction between light introduced into the optical fiber and the medium.

Optical fiber multiplexing/demultiplexing device for multiple-fiber ribbon of optical fibers and their fabrication method

Abstract: An optical fiber multiplexing/demultiplexing devices for the multiple-fiber ribbon of optical fibers, and the fabrication method. It comprises a set of optical fibers arranged in the form of a multiple-fiber ribbon wherein an intermediate point on the multiple-fiber ribbon is first cut, the covers of the optical fibers in the multiple-fiber ribbon thus cut are removed on both sides of the cut edges by a certain length required to expose the optical fiber elements, and both edges of the optical fiber elements paired on both sides of the cut point are welded each other by arc discharge; a pair of substrates in each of which a plurality of V-grooves by the number of the optical fiber elements are provided in parallel each other at equal intervals to form an array on one side thereof, and the pair of substrates assembled so that the scrubbed sides of the surfaces in the pair of substrates are contacted each other so as to couple the cores of the optical fiber elements together according to the Evanescent wave coupling.