Abstract: Embodiments describe an optical fiber that includes a core. The core has high compressive stress. The compressive stress of the core is in a range of about 20 to 60 MPa. The optical fiber further includes a cladding. The cladding is divided into a first cladding layer and a second cladding layer. The second cladding layer has a high residual stress. The high residual stress of the second cladding layer is in a range of about 20 to 60 MPa. The optical fiber enables reduction of particle related breaks. Further, the optical fiber has elevated LLT strength. The LLT strength is about 6 Kg. The optical fiber has high proof test yield. Furthermore, the optical fiber is highly sensitive to micro-bending of the optical fiber.

Abstract: An optical fiber tape includes a matrix and at least one optical fiber connected to the matrix in an undulating manner. The undulations of the optical fiber are generally sinusoidal, semicircular, or elliptic, and are of amplitude and wavelength such that the minimum bend radius of each undulation is not less than a minimum bend radius specified by a manufacturer of the optical fiber. A road having an upper surface has a pathway indented into the upper surface to less than full depth of the road and has the optical fiber tape laid in the pathway so that the optical fiber tape does not protrude above the upper surface of the road.

Abstract: Methods of manufacturing multi-mode optical fiber, and multi-mode optical fiber produced thereby, are disclosed. According to embodiments, a method for forming an optical fiber may include heating a multi-mode optical fiber preform and applying a draw tension to a root of the multi-mode optical fiber preform on a long axis of the multi-mode optical fiber preform thereby drawing a multi-mode optical fiber from the root of the multi-mode optical fiber preform. The draw tension may be modulated while the multi-mode optical fiber is drawn from the root of the multi-mode optical fiber preform. Modulating the draw tension introduces stress perturbations in the multi-mode optical fiber and corresponding refractive index perturbations in a core of the multi-mode optical fiber.

Abstract: A method for continuously producing an optical fiber cable includes: producing a cable core through cable core producing equipment; conveying the produced cable core to a first cable storing device; conveying the cable core from the first cable storing device to a sheath extrusion device, wherein an exterior of the cable core is covered with a sheath, and the optical fiber cable is obtained by processing; receiving the optical fiber cable from the sheath extrusion device by a cable rolling device, wherein the optical fiber cable is rolled at a tray, and a finished tray rolled with the optical fiber cable is obtained; checking whether the finished tray rolled with the optical fiber cable is qualified, and carrying an unqualified finished tray rolled with the optical fiber cable to a repairing area for repairing until qualified; and fixing sealing plates at a qualified finished tray through a sealing device.

Abstract: A cladding light stripper may include a double-clad optical fiber having a core for guiding signal light, an inner cladding surrounding the core, and an outer cladding surrounding the inner cladding. The optical fiber may include a stripped portion forming an exposed section. The exposed section may include a plurality of spirally-arranged transversal notches disposed along the optical fiber to enable light to escape the inner cladding upon impinging on the plurality of notches. A circumferential segment of the optical fiber may include a single notch of the plurality of notches. Each of the plurality of notches may have a depth of only a partial distance to the core.

Abstract: Various embodiments include methods and apparatus structured to increase efficiencies of a drilling operation. These efficiencies may be realized with a fiber cable located in a wellbore at a well site, where the fiber cable can include an optical fiber disposed as a single handed helix in the fiber cable, where the optical fiber is disposed in the cable without having helix hand reversal. Construction of such fiber cables may include applying a twist to the optical fiber during insertion of the optical fiber into the fiber cable in a tubing process in which control of an amount of the twist to form a portion of the optical fiber can control excess fiber length in the tube. Additional apparatus, systems, and methods can be implemented in a variety of applications.

Abstract: A method of forming a coupler, the method comprising: (a) heating a portion of an optical fiber having multiple cores and an initial diameter; and (b) applying a tensile force across the portion such that the portion stretches, thereby reducing the initial diameter to a reduced diameter sufficient to cause optical signals propagating in one or more of the multiple cores to leave their respective cores and enter other cores of the fiber.

Abstract: A method for producing an optical fiber is provided. The method includes the steps of drawing an optical fiber from a heated glass source in a furnace and introducing index perturbations to the optical fiber via a plurality of perturbation sources arranged at a plurality of different azimuthal locations. The index perturbations are introduced synchronously at different locations along the axial length of the fiber by the plurality of perturbation sources in a generally helical pattern on the outside surface of the fiber in one embodiment. According to another embodiment, the index perturbations are introduced by the plurality of perturbation sources at different frequencies.

Abstract: An optical transmission medium bend working device that reduces bending loss of an optical transmission medium includes: an arc-discharge electrode that partially and sequentially heats a bend working area of a tape core wire in an up-down direction, the tape core wire extending in the up-down direction with a distal end thereof being located on a lower side, the bend working area being located above the distal end; a core wire holding unit that holds a portion of the tape core wire located above the bend working area; and a bending arm that applies force to the tape core wire in a state where the bend working area is heated to bend the tape core wire at the bend working area.

Abstract: Photonic devices that include in-line optical microfibers for different uses such as sensing are described. At least one enclosed cavity is positioned within the optical microfiber. One or more enclosed cavities are positioned along or adjacent to a central axis of the microfiber. Light travelling within the microfiber passes through both the enclosed cavity and a remaining portion of the microfiber not occupied by the enclosed cavity. For interferometer applications, recombination of the light propagating through the microfiber and cavity has a light intensity correlated to an external physical property to be measured such as temperature and refractive index as well as strain and bending experienced by the fiber. Plural cavities can be constructed sequentially. Further, whispering gallery mode (WGM) resonator properties of the enclosed cavity can be used to measure external properties. A method for fabricating the optical microfiber devices by micromachining is also described.

Abstract: A calibration assembly has a base and mounting elements to mount the base to a laser. The base has a front, middle and rear portions that are used to align the calibration assembly to the laser to cleave optical fibers with the laser. The front portion has a channel to receive the optical fibers, the middle portion has openings to confirm alignment of the laser; and the rear portion has a rear opening used to adjust the pitch and roll of the laser.

Abstract: The invention relates to a method for laser-based splicing of a glass fiber (1) onto an optical component (3), comprising the following steps: arranging both surfaces to be spliced substantially parallel to each other and at a predefined distance from each other; and aiming a laser beam (4) at the optical component (3). In order to specify an improved method in which the properties of the joining partners are maintained to the greatest extent during splicing, which exhibits high reproducibility and in particular is suitable for splicing joining partners of different cross-sections, the invention proposes that the angle of incidence of the laser beam (4) on the surface of the optical component be between 15° and 45°.

Abstract: An optical device including an active core layer of silica glass doped with ions which serve as optical emitters, the active core layer being on a silica glass substrate and having a layer thickness of at least 5 ?m, and wherein the layer is sintered at a temperature range of 1500-1600 C. and subsequently heat treated by a laser.

Abstract: An optical fiber which, at an optical fiber connecting end having a plurality of voids around the periphery of a core, has a light-permeable substance, such as a resin or glass whose refractive index is lower than that of quartz type substances, filled in the voids adjacent to the connecting end. An optical fiber connecting section where an optical fiber having a plurality of voids in a clad around the periphery of a core is connected to another optical fiber, wherein the optical fiber is connected end-to-end to aforesaid another optical fiber through a refractive index matching agent whose refractive index at the minimum temperature in actual use is lower than that of the core.

Abstract: A fiber optic connector includes a ferrule. The ferrule includes an inner piece including silica and an outer piece including ceramic. The outer piece surrounds the inner piece and the inner piece extends beyond an end of the outer piece by a distance of at least 10 micrometers.

Abstract: An optical fiber having excellent strength that can be manufactured at low cost, as well as a method for making such optical fiber, is provided. An optical fiber 1 is a silica-based optical fiber comprising a core 11, an optical cladding 12 surrounding the core & 11, and a jacketing region 13 surrounding the optical cladding 12 and having a uniform composition throughout from the internal circumference to the outer circumference. A compressive strained layer having a residual compressive stress is provided at the outermost circumference of the jacketing region 13.

Abstract: A pre-terminated optical fiber assembly with a ferrule having front and rear opposed faces and at least one fiber bore defined longitudinally therethrough includes a glass optical fiber is disposed within the at least one fiber bore with the fiber fused to the ferrule at a location at least 1 mm deep inside the bore. A method for fusing is also disclosed. The ferrule 14 is desirably composed of an inorganic composite material, the composite comprising a material gradient from at least 75% by volume of a first inorganic material to at least 75% by volume of second inorganic material in the radially inward direction, where the first inorganic material has a fracture toughness of at least 1 MPa•m1/2, and the second inorganic material has a softening point of no greater than 1000° C., desirably no greater than 900° C.

Abstract: A process and apparatus for cleaving an optical fiber are provided. The process includes window stripping the optical fiber using a laser source to create a window strip. The window stripped optical fiber is then scribed at a position within the window strip and tension is applied to the optical fiber. The cleaved optical fiber can be chamfered by applying a heat source to the cleaved end face. The above process and apparatus provide a high precision and inexpensive system for fiber cleaving and chamfering.

Abstract: A method of producing a thermally stable grating allows the grating to be placed in environments where temperatures reach 1000° C. These gratings may be concatenated so as to form a sensor array. The method requires a step of lowering the characteristic intensity threshold of a waveguide by at least 25%, followed by irradiating the waveguide with femtosecond pulses of light having a sufficient intensity and for a sufficient duration to write the grating so that at least 60% of the grating remains after exposures of at least 10 hours at a temperature of at least 1000° C. Pre-writing a Type I grating before writing a minimal damage Type II grating lowers the characteristic threshold of the waveguide so that a stable low damage type II grating can be written; alternatively providing a hydrogen or deuterium loaded waveguide before writing the grating lowers the characteristic threshold of the waveguide.

Abstract: A process for producing a synthetic silica glass optical component which contains at least 1×1017 molecules/cm3 and has an OH concentration of at most 200 ppm and substantially no reduction type defects, by treating a synthetic silica glass having a hydrogen molecule content of less than 1×1017 molecules/cm3 at a temperature of from 300 to 600° C. in a hydrogen gas-containing atmosphere at a pressure of from 2 to 30 atms.

Abstract: A method for producing an optical fiber is provided. The method includes the steps of drawing an optical fiber from a heated glass source in a furnace and introducing index perturbations to the optical fiber via a plurality of perturbation sources arranged at a plurality of different azimuthal locations. The index perturbations are introduced synchronously at different locations along the axial length of the fiber by the plurality of perturbation sources in a generally helical pattern on the outside surface of the fiber in one embodiment. According to another embodiment, the index perturbations are introduced by the plurality of perturbation sources at different frequencies.

Abstract: A multimode optical fiber is drawn form an optical fiber preform, and during said drawing step, a series of perturbations are imparted to the fiber along the length of the optical fiber, said perturbations exhibiting a non-constant amplitude or repeat period.

Abstract: Individually operable laser diodes in an array are associated with optical fibers for treatment of a material. Each laser diode has a generally Gaussian or similar profile. A guide block receives optical fiber terminal distal ends and enables irradiation of a surface for treatment with overlapping profiles. A control system controls individual laser diodes to achieve desired illumination profiles for a given process. The process is performed in a suitable environment which may include a vacuum system, controlled gaseous environment, or in a doping medium such as a surface coating or even a liquid. Optional relay optics interposed between the terminal distal ends and the treatment material allows distant relaying and reimaging. An optical isolator assembly may be interposed between the relay optics and the treatment material. The system and related methods allow direct irradiation from laser diodes to treat materials.

Abstract: A micro identification system supports facile optical assemblies and components. A segment of optical fiber can comprise an identifier formed via actinic radiation. The identifier can generate a laser interference pattern that can be read through a cylindrical surface of the optical fiber to determine a code. Modified optical fibers are those fibers that have been shaped or coated to an extent beyond the demands of normal communications optical fibers. In one example, modified fibers are no longer than about two feet in length. For another example, the modified fibers can have either a non-cylindrical end face, a non flat end face, an end face the plane of which is not perpendicular to the longitudinal axis of the waveguide, an end face coated with high density filter, or an identifier on or near an end face.

Abstract: A process and apparatus for making silicon or silicon/germanium core fiber is described, which uses a plasma process with reducing agent to make a preform. The process also makes the recommendations in selecting the adequate cladding tube for better fiber properties. An improved fiber drawing apparatus is also disclosed in order to draw this new type of preform.

Abstract: A method of producing a thermally stable grating allows the grating to be placed in environments where temperatures reach 1000° C. These gratings may be concatenated so as to form a sensor array. The method requires a step of lowering the characteristic intensity threshold of a waveguide by at least 25%, followed by irradiating the waveguide with femtosecond pulses of light having a sufficient intensity and for a sufficient duration to write the grating so that at least 60% of the grating remains after exposures of at least 10 hours at a temperature of at least 1000° C. Pre-writing a Type I grating before writing a minimal damage Type II grating lowers the characteristic threshold of the waveguide so that a stable low damage type II grating can be written; alternatively providing a hydrogen or deuterium loaded waveguide before writing the grating lowers the characteristic threshold of the waveguide.

Abstract: A method of producing a thermally stable grating allows the grating to be placed in environments where temperatures reach 1000° C. and where the grating is relatively stable and has very low loss from scatter. These gratings have spectral characteristics that allow them to be concatenated so as to form a sensor array. The method requires a step of lowering the characteristic intensity threshold of a waveguide by at least 25%, followed by irradiating the waveguide with femtosecond pulses of light having a sufficient intensity and for a sufficient duration to write the grating so that at least 60% of the grating remains after exposures of at least 10 hours at a temperature of at least 1000° C.

Abstract: The invention relates to devices having periodic refractive index modulation structures and fabrication methods for the devices using a laser means. By focusing a pulsed laser beam into a transparent material substrate, a path of laser modified volumes can be formed with modified refractive index compared with the unprocessed material. By selecting appropriate laser parameters and relative scan speed, the laser modified path defines an optical waveguide. Separation distance of the individual modified volumes define a periodic modification pattern along the waveguide path, so that the waveguide structures also exhibit grating responses, for example, as spectral filters, Bragg reflectors, grating couplers, grating sensors, or other devices.

Abstract: An object of the present invention is to provide an artificial quartz member inhibited from suffering the decrease in transmittance in a laser light wavelength region which is caused by long-term irradiation with a laser light having a wavelength of 200 nm or shorter; and a process for producing the artificial quartz member. The invention provides an artificial quartz member for use as an optical element to be irradiated with a laser light having a wavelength of 200 nm or shorter, having an aluminum content of 200 ppb or lower.

Abstract: To obtain an optical component having excellent secondary optical nonlinear properties by irradiating a surface and/or inside of glass having at least one member selected from Ni, Fe, V, Cu, Cr and Mn as a heat source material for absorbing and converting a laser beam to heat, incorporated to a glass matrix comprising at least one glass-forming oxide-selected from SiO2, GeO2, B2O3, P2O5, TeO2, Ga2O3, V2O5, MoO3 and WO3 and at least one member selected from alkali metals, alkaline earth metals, rare earth elements and transition elements, with a laser beam with a wavelength to be absorbed by the heat source material, to convert the irradiated portion to a single crystal or a group of crystal grains comprising components contained in the glass matrix and not containing the heat source material, thereby to form a pattern.

Abstract: There is described herein a method and system for inscribing gratings in optical waveguides. The waveguides may be hydrogen-free, germanium-free, low germanium, low hydrogen, and a combination thereof. Such gratings written in hydrogen-free fibers are suitable for sensor applications in which the use of hydrogen for photosensitizing fibers is undesirable owing to their increased sensitivity to nuclear radiation. The grating are formed by at least one pulse having a wavelength comprised between about 203 nm and about 240 nm. The laser source may be a Continuous Wave (CW) laser source or a pulsed laser source generating at least one pulse having a width in the order of nanoseconds (109).

Abstract: The present invention relates to a fiber having a core of crystal fiber doped with chromium and a glass cladding. The fiber has a gain bandwidth of more than 300 nm including 1.3 mm to 1.6 mm in optical communication, and can be used as light source, optical amplifier and tunable laser when being applied for optical fiber communication. The present invention also relates to a method of making the fiber. First, a chromium doped crystal fiber is grown by laser-heated pedestal growth (LHPG). Then, the crystal fiber is cladded with a glass cladding by codrawing laser-heated pedestal growth (CDLHPG). Because it is a high temperature manufacture process, the cladding manufactured by this method is denser than that by evaporation technique, and can endure relative high damage threshold power for the pumping light.

Abstract: Techniques and systems suitable for performing low-loss fusion splicing of optical waveguide sections are provided. According to some embodiments, multiple laser beams (from one or more laser) may be utilized to uniformly heat a splice region including portions of the optical waveguide sections to be spliced, which may have different cross-sectional dimensions. According to some embodiments, the relative distance of the optical waveguide sections and/or the power of the multiple laser beams may be varied during splicing operations.

Abstract: A micro identification system supports facile optical assemblies and components. A segment of optical fiber can comprise an identifier formed via actinic radiation. The identifier can generate a laser interference pattern that can be read through a cylindrical surface of the optical fiber to determine a code. Modified optical fibers are those fibers that have been shaped or coated to an extent beyond the demands of normal communications optical fibers. In one example, modified fibers are no longer than about two feet in length. For another example, the modified fibers can have either a non-cylindrical end face, a non flat end face, an end face the plane of which is not perpendicular to the longitudinal axis of the waveguide, an end face coated with high density filter, or an identifier on or near an end face.

Abstract: There is provided a glass member for optical parts that represents a greater absolute value |?n| of refractive index difference ?n of visual light between base glass and heterogeneous phase region. In the glass member for optical parts, the heterogeneous phase region distinguishable by a different refractive index is formed at an intended location inside a glass by focused irradiation of a pulsed laser. When a multicomponent optical glass of SiO2, Rn2+RO, and TiO2 is used, |?n| of no less than 0.005 can be attained under a lower irradiation intensity. It is suitable for optical parts such as optical low-pass filters, diffractive optical parts, optical diffusion parts, optical filters, lenses and microlens arrays.

Abstract: A process and apparatus for making silicon or silicon/germanium core fiber is described, which uses a plasma process with reducing agent to make a preform. The process also makes the recommendations in selecting the adequate cladding tube for better fiber properties. An improved fiber drawing apparatus is also disclosed in order to draw this new type of preform.

Abstract: A double-clad optical fiber fabrication method including the steps of: preparing a crystal fiber, inserting the crystal fiber into a silica capillary, attaching a sapphire tube to the periphery of the silica capillary, and applying a laser beam to the sapphire tube to increase the temperature of the sapphire tube and to further fuse the silica capillary with thermal radiation to have the fused silica capillary be wrapped about the crystal fiber, thereby forming the desired double-clad optical fiber.

Abstract: An optical fiber treatment system is provided for high power laser transmission to an area of medical treatment. A side fire optical fiber tip for use in high power laser applications having outputs of greater than or equal to 50 Watts is a key to the system. Embodiments are particularly appropriate for the medical treatment of benign prostate hyperplasia (BPH) with a side fire optical fiber tip using a Holmium:YAG laser or a high power diode laser. Such procedures can be done with only local anesthesia. A predetermined length of an output tip on the distal end of the optical fiber of the present invention is formed with an optical fiber core and cladding layer of preselected thickness wherein the cladding to core diameter ratio is at least as great as 1.1. A side fire surface is formed on the distal end of the core/clad output end.

Abstract: A quick terminating fiber optic assembly and method of making same is provided. A pre-terminated fiber optic assembly having an optical fiber already terminated therein includes an exposed optical fiber. The exposed fiber is aligned and contacted with a second exposed optical fiber of another optical cable, and the two fibers are spliced. A sleeve is provided to cover and protect the splice and any exposed fibers. The sleeve secures the pre-terminated fiber optic termini to second optical fiber. This process terminates the second optical fiber at the termini in less time and with the same or similar tools as a conventional method of terminating optical fibers at a termini.

Abstract: There is provided a method of manufacturing an optical waveguide, the method including: allowing a beam to be incident in an optical waveguide direction of an optical waveguide material; generating an optical soliton in the optical waveguide material by adjusting intensity of the incident beam according to the optical waveguide material; allowing the incident beam to be re-incident at an intensity higher than an intensity of the incident beam after checking generation of the optical soliton in the optical waveguide material; and increasing a refractive index of an optical soliton-generating area of the optical waveguide material by the re-incident beam to thereby form an optical waveguide.

Abstract: Optical fiber preforms can comprise a glass preform structure with an inner cavity. A powder can be placed within the inner cavity having an average primary particle size of less than about one micron. The powder can be in the form of an unagglomerated particles or a powder coating with a degree of agglomeration or hard fusing ranging from none to significant amounts as long as the primary particles are visible in a micrograph. Powders can be placed within a preform structure by forming a slurry with a dispersion of submicron/nanoscale particles within a cavity within the preform. In other embodiments, a powder coating is formed within a preform structure by depositing the powder coating directly from a reaction product stream. The formation of the powder coating can be formed within the reaction chamber or outside of the reaction chamber by flowing the product particle stream through a conduit leading to the preform structure. In additional embodiments, a powder coating is placed on an insert, e.g.

Abstract: A method of making an illuminator out of a light guide using a laser to cut a pattern of U shaped notches or grooves in at least one side of the light guide. The laser may be moved at a substantially constant or variable speed during continuous or intermittent pulsing of the laser to cut a plurality of notches or grooves of a desired depth, width, spacing, relative position, diameter and/or surface finish in the light guide.

Abstract: An optical fiber 200 with a high thermal resistance fiber Bragg grating (FBG) 130. Compared to existing FBG's, the invention provides greatly enhanced thermal stability, being stable up to 1200° C. The grating reflectivity and resonant wavelength are maintained for extended duration at high temperatures. The FBG is thus suitable in high temperature sensors. The high thermal resistance of the FBG is obtained in a method of pre-annealing the optical fiber 105 at high temperature prior to inscribing the FBG. The high thermal resistance is optionally enhanced in a post-FBG creation step of heat treating the optical fiber 105 and FBG.

Abstract: A glass powder or a glass-ceramic powder is provided that includes multicomponent glasses with at least three elements, where the glass powder or a glass-ceramic powder has a mean particle size of less than 1 ?m. In some embodiments, the mean particle size is less than 0.1 ?m, while in other embodiments the mean particle size is less than 10 nm.

Abstract: A double-clad optical fiber fabrication method including the steps of: preparing a crystal fiber, inserting the crystal fiber into a silica capillary, attaching a sapphire tube to the periphery of the silica capillary, and applying a laser beam to the sapphire tube to increase the temperature of the sapphire tube and to further fuse the silica capillary with thermal radiation to have the fused silica capillary be wrapped about the crystal fiber, thereby forming the desired double-clad optical fiber.

Abstract: Provided is a ferrule holding member with a transparent body attached to an inner hole of a sleeve. The transparent body has a primary end face for bringing into contact with an end face of a plug ferrule at a halfway position in an axial direction of the sleeve. The primary end face of the transparent body has a convex curved surface obtained through heat treatment. The convex curved surface is preferably an unpolished surface, and a region with a radius of 75 ?m or more, centered around a shaft axis of the sleeve at the convex curved surface, has a convex spherical surface. Alternatively, the transparent body is directly fixed to an inner surface of the sleeve through heat treatment.

Abstract: Disclosed are multifiber ferrule assemblies and methods for manufacturing the same. In one embodiment, a finished multifiber ferrule can be provided with a front end having a first front surface that extends beyond a second front surface, thereby inhibiting interaction with a laser beam during processing. A plurality of optical fibers can be fixed within respective optical fiber bores and extend from respective optical fiber bore openings to a position beyond the first front surface. The plurality of optical fibers can be processed by cutting and polishing with a laser beam for providing each optical fiber with a final polished end surface located beyond the first front surface. In further embodiments, an offset structure is positioned with respect to a finished multifiber ferrule after cutting and polishing the optical fibers.

Abstract: The present invention relates to methods of connecting optical fibers. In a first aspect, the method proceeds by using a ferrule device having a passage adapted to apply radial pressure to optically align and hold in position opposed fiber ends, and fusing said fiber ends held by said ferrule device. In another aspect, the method of the present invention uses a ferrule device to optically align without mechanized adjustment and hold in position opposed fiber ends with a gap where said fiber ends meet, where the fibers have a temperature of fusion that is higher than a melting temperature of said ferrule device. The method then transmits radiation directly onto said fiber ends without significant direct transmission onto said ferrule device to generate heat in said fiber ends and fuse said fiber ends held by said ferrule device.

Abstract: The invention discloses an in-line polarization-state converter. In the polarization converter, a laser beam is radiated onto the side of a photosensitive optical fiber. The laser beam causes the refractive index of an optical fiber core to asymmetrically vary. Birefringence is induced in a core mode of the optical fiber by the variation in the asymmetrical refractive index. An optical fiber segment having the birefringence is generally disposed on a waveguide path of the optical fiber to change the polarization state of an optical signal passing through the optical fiber segment. That is, the phase of the optical signal passing through the optical fiber is changed by radiation of laser beams, which results in a variation in polarization state. The polarization converter disposed on the waveguide path is covered with a metal tube in order to prevent the polarization converter from being bent or broken.

Abstract: An example apparatus includes an optical fiber including a core and cladding, the core being situated to propagate an optical beam along a propagation axis associated with the core, and at least one fiber Bragg grating (FBG) situated in the core of the optical fiber, the fiber Bragg grating including a plurality of periodically spaced grating portions situated with respect to the propagation axis so that light associated with Raman scattering is directed out of the core so as to reduce the generation of optical gain associated with stimulated Raman scattering (SRS).