Abstract: A repeatable optical waveguide interconnection may include first and second optical waveguides having respective first and second end faces. Each of the first and second optical waveguides may include a core having a core index of refraction, and a cladding surrounding the core and having a cladding index of refraction different than the core index of refraction. The repeatable optical waveguide interconnection may further include a first index matching elastomeric solid layer having a proximal face chemically bound to the first end face and a low-tack distal face opposite the proximal face to be repeatably optically coupled to the second end face. Further, the first index matching elastomeric solid layer may have an index of refraction matching at least the index of refraction of the core.

Abstract: An optical fiber switch which may include first and second angled optical fibers having respective first and second end faces. Each of the first and second angled optical fibers may include a core having a core index of refraction, and a cladding surrounding the core and having a cladding index of refraction less than the core index of refraction. The optical fiber switch may further include a first index matching elastomeric solid layer having a proximal face coupled to the first end face, and a distal face opposite the proximal face to be repeatably optically coupled to the second end face. The first index matching elastomeric solid layer may have an index of refraction matching at least the index of refraction of the core. The optical fiber switch may also include at least one actuator for relatively moving the first and second angled optical fibers between a coupled position and an uncoupled position.

Abstract: A luminescence concentrator (LK) may concentrate both incident direct and diffuse light by way of frequency shift and total internal reflection. It differs fundamentally from geometric concentrators. With sufficient geometric expansion of the collector plate, nearly arbitrarily high concentration can be achieved in the LK. A luminescence disperser is an apparatus which holds both directional and nondirectional incident light captive in a transparent body by way of frequency shift and total internal reflection and emits it diffusely or directionally uniformly distributed across an area by way of luminescence emission. The object of the invention is a method for the technical implementation of the LK and luminescence disperser, using zeolite crystals having a nanotube structure, into which the luminescent dyes are embedded such that they have antenna properties. Using the resulting novel structures, problems can be solved which made the technical use of LK impossible or at least considerably limited it.

Abstract: Coated optical fibers and related apparatuses, links, and methods for optically attenuating light directed to or from optical fibers are disclosed. In one embodiment, an optical fiber includes an optical fiber end. The optical fiber end may be a source end and/or a detector end, and may be angle-cleaved. A coating material is disposed on at least a portion of the optical fiber end and configured to optically attenuate a portion of light directed to the optical fiber end. The material type of the coating material and/or the thickness of the coating material may be selectively controlled to control the amount of optical attenuation. The thickness of the coating material may also be controlled to provide the desired thickness of coating material onto at least a portion of the optical fiber end. The coating material may also be selectively patterned to improve the bandwidth of a multi-mode optical link.

Abstract: Optical fiber apparatus having a wavelength of operation, that comprises an optical fiber including a core comprising an active material for providing light having the operating wavelength responsive to the optical apparatus receiving pump optical energy having a pump wavelength; a cladding disposed about the core; at least one region spaced from the core; and wherein the optical fiber is configured and arranged such that at the wavelength of operation the optical fiber can propagate a plurality of modes and wherein the optical fiber comprises a fundamental mode that is primarily a mode of the core and at least one higher order mode (HOM) that is a mixed mode of a selected mode of the core and of a selected mode of the at least one region.

Abstract: A nanoparticle array photonic waveguide, a photonic transmission system and a method of photonic transmission compensate for optical loss in an optical signal through stimulated emission using an optical gain material in a core of composite nanoparticles. The nanoparticle array photonic waveguide includes a plurality of the composite nanoparticles arranged adjacent to one another in a row. A composite nanoparticle of the plurality includes a shell and a core. The shell includes a negative dielectric constant material that is capable of supporting an optical signal on a surface of the shell. The core is adjacent to a side of the shell opposite to the shell surface. The core includes an optical gain material (OGM) that is capable of providing optical gain to the optical signal through stimulated emission within the OGM.

Abstract: A self-written branched optical waveguide is formed. A laser beam 2 from a laser source (not shown) is focused with a lens 3 onto the face of incidence 10 of an optical fiber 1. The laser beam of an LP11 mode was emitted from the face of emergence 11, and “bimodal” light intensity peaks were arranged in the horizontal direction (1.A). A slide glass 4 coated with a photocurable resin gel 5 was placed horizontally (1.B). A single linear cured material 61 was formed as the LP11-mode laser beam was emitted from the face of emergence 11 of the optical fiber 1 (1.C). A branch portion 62 was then formed at a distance L from the face of emergence 11 of the optical fiber 1, which was followed by the growth of two cylindrical cured materials 63a and 63b. The two cylindrical cured materials 63a and 63b were linear branches, and formed an angle of about four degrees. An optical waveguide 60 thus formed was composed of cured materials 61, 62, 63a, and 63b (1.D).

Abstract: The present invention relates to an optical fiber which has a structure for further increasing an FOM (=|dispersion|/loss) and which can be applied to a dispersion compensation module. The optical fiber is mainly composed of silica glass and has a core region including a center of an optical axis, a depressed region surrounding the core region, a ring region surrounding the depressed region, and a cladding region surrounding the ring region and doped with F. As compared with the refractive index of pure silica glass, a relative refractive index difference of the core region is greater than 2% but less than 3%, a relative refractive index difference of the depressed region is ?1% or more but ?0.5% or less, a relative refractive index difference of the ring region is 0.01% or more but 0.24% or less, and a relative refractive index difference of the cladding region is ?0.3% or more but ?0.1% or less. The FOM at the wavelength of 1550 nm is 250 ps/nm/dB or more.

Abstract: Systems and methods for manipulating light with high index contrast waveguides clad with crystalline substances having that exhibit large nonlinear electro-optic constants ?2 and ?3. Waveguides fabricated on SOI wafers and clad with crystalline materials such as barium titanate are described. Embodiments of waveguides having slots, electrical contacts, and input waveguide couplers are discussed. Waveguides having closed loop structures (such as rings and ovals) as well as linear or serpentine waveguides, are described. Optical signal processing methods, such as optical rectification and optical modulation, are disclosed.

Abstract: The present invention relates to an optical fiber that includes a glass fiber and three or more coatings that encapsulate the glass fiber, where the three or more coatings include a primary coating in contact with said glass fiber, one or more intermediate coatings that surround the primary coating, and a secondary coating that surrounds the intermediate coatings. Both three-coating and four-coating systems are described that afford improve microbend performance.

Abstract: A disclosed waveguide film cable includes a waveguide formed on a film. The waveguide film cable includes a coating film made of a material having a Young's modulus smaller than or equal to the Young's modulus of a material that forms the film and/or the waveguide and coats partially or entirely the film and/or the waveguide.

Abstract: A photonic band gap fiber and method of making thereof is provided. The fiber is made of a germanate glass comprising at least 30 mol % of a germanium oxide and has a longitudinal central opening, a microstructured region having a plurality of longitudinal surrounding openings, and a jacket. The air fill fraction of the microstructured region is at least about 90%. The fiber may be made by drawing a preform into a fiber, while applying gas pressure to the microstructured region. The air fill fraction of the microstructured region is changed during the drawing.

Abstract: The present disclosure relates to a telecommunications cable having a layer constructed to resist post-extrusion shrinkage. The layer includes a plurality of discrete shrinkage-reduction members embedded within a base material. The shrinkage-reduction members can be made of a liquid crystal polymer. The disclosure also relates to a method for manufacturing telecommunications cables having layers adapted to resist post-extrusion shrinkage.

Abstract: The invention consists in an amplifying optical fiber comprising a core containing a dopant and a cladding, wherein said core comprises a monomode core intended to propagate an optical signal, quantum dots of a semiconductor material being disposed in or near said monomode core, and a multimode core surrounding the monomode core, intended to receive a pumping signal.

Abstract: The invention relates to coated optical fibers comprising soft primary coatings and to such primary coatings for protecting glass optical fibers having a sufficient high resistance against cavitation. In particular, the primary coatings have a cavitation strength at which a tenth cavitation appears (?10cav) of at least about 1.0 MPa as measured at a deformation rate of 0.20% min?1 and of at least about 1.4 times their storage modulus at 23° C. The coating preferably shows strain hardening in a relative Mooney plot, preferably has a strain energy release rate Go of about 20 J/m2 or more, and preferably has a low volumetric thermal expansion coefficient. The invention furthermore provides a method and apparatus for measuring the cavitation strength of a primary coating.

Abstract: A resin composition for an optical material, which is excellent in heat resistance and transparency and is soluble in an aqueous alkali solution, a resin film for an optical material made of the resin composition, and an optical waveguide using the same are provided. The resin composition for an optical material includes: (A) an alkali-soluble (meth)acrylate polymer containing a maleimide skeleton in a main chain; (B) a polymerizable compound; and (C) a polymerization initiator. The resin film for an optical material is made of the resin composition for an optical material. The optical waveguide has a core part and/or a clad layer formed using the resin composition for an optical material or the resin film for an optical material.

Abstract: Provided are an optical device and a method of fabricating the same. The optical device includes: a substrate; and a ring resonator on the substrate. The ring resonator includes: a cladding layer including a lower cladding layer and an upper cladding layer on the substrate; a core including a plurality of rings between the lower cladding layer and the upper cladding layer; and an embeded layer interposed between the core and the cladding layer and having a refractive index less than that of the core and more than that of the cladding layer.

Abstract: An optical fiber including a surface including a non-covalent multilayer including a light-absorbing material can be used to develop fluorescence microscopy with a lateral resolution of about 5 nm and possibly lower. The non-covalent multilayer can be a highly absorptive thin film, for example a film based on J-aggregates, which can be used with conventional Near-Field Scanning Optical Microscopy.

Abstract: An active energy ray (e.g. UV rays)-curable organopolysiloxane resin composition comprises (A) 100 parts by weight of an organopolysiloxane resin containing epoxy groups and aromatic hydrocarbon groups, (B) 0.05 to 20 parts by weight of a photo acid generator, (C) 0.01 to 20 parts by weight of a photosensitizer or photo-radical generator, and (D) 0 to 5,000 parts by weight of an organic solvent. An optical transmission component made of the above-mentioned composition cured by irradiation with active energy rays (for example, UV rays). A method for manufacturing an optical transmission component by irradiating the above-mentioned composition with active energy rays (for example, UV rays).

Abstract: An all-fiber optical pulse compression arrangement comprises a concatenated arrangement of a section of input fiber (e.g., a single mode fiber), a graded-index (GRIN) fiber lens and a section of pulse-compressing fiber (e.g., LMA fiber). The GRIN fiber lens is used to provide mode matching between the input fiber (supporting the propagation of chirped optical pulses) and the pulse-compressing fiber, with efficient pulse compression occurring along the length of the LMA fiber. The dispersion and length of the LMA fiber section are selected to provide the desired degree of pulse compression; for example, capable of reconstituting a femtosecond pulse as is used in supercontinuum generation systems.

Abstract: Disclosed is an optical fiber having a silica-based core comprising an alkali metal oxide a silica-based core, said core comprising an alkali metal oxide selected from the group consisting of K2O, Na2O, Li2O, Rb2O, Cs2O and mixtures thereof in an average concentration in said core between about 10 and 10000 ppm by weight, and a silica-based cladding surrounding and directly adjacent the core, the cladding including a region having a lower index of refraction than the remainder of such cladding. By appropriately selecting the concentration of alkali metal oxide dopant in the core and the cladding, a low loss optical fiber may be obtained which exhibits a cable cutoff less than 1400 nm chromatic dispersion at 1550 nm between about 13 and 19 ps/nm/km, and a zero dispersion wavelength less than about 1324 nm.

Abstract: A thermally stable chalcogenide glass, a process for making the same, and an optical fiber drawn therefrom are provided. A chalcogenide glass having the composition Ge(5?y)As(32?x)Se(59+x)Te(4+y) (0?y?1 and 0?x?2) is substantially free from crystallization when it is heated past the glass transition temperature Tg or drawn into optical fibers. A process for making the thermally stable chalcogenide glass includes purifying the components to remove oxides and scattering centers, batching the components in a preprocessed distillation ampoule, gettering oxygen impurities from the mixture, and heating the components to form a glass melt. An optical fiber formed from the chalcogenide glass is substantially free from crystallization and exhibits low signal loss in the near-infrared region, particularly at wavelengths of about 1.55 ?m.

Abstract: Provided are an optical resin and an optical member using the same, both orientation birefringence and photoelasticity birefringence of the optical material being deadened and generally eliminated. The optical material consists of a composite constituent system of three or more constituents including a copolymerization system of monomer-element number not smaller than two, combination and constituent ratio of the composite constituent system being set so that both orientation birefringence and photoelasticity birefringence of the optical material are deadened at the same time and 5.0×10?5 or less is given under a condition that principal chains of the copolymerization system have degree of orientation equal to 0.03, and further a photoelasticity constant not greater than 1.0×10?12 (Pa?1) is obtained. The composite constituent system may contain an additive containing a low molecular weight compound which has an anisotropic polarizability and can be orientated in a polymer.

Abstract: A process for manufacturing an optical fiber includes: drawing an optical waveguide from a glass preform; applying a layer of a first coating material on the optical waveguide; curing the first coating layer material to obtain a first coating layer; applying a layer of a second coating material onto the first coating layer; applying a layer of colored coating material onto the second coating layer; curing the second coating material and the colored coating material in a single step to obtain a second coating layer superposed on the first coating layer and a colored coating layer superposed on the second coating material layer, the obtained second coating layer having an elastic modulus higher than that of the first coating layer and lower than that of the colored coating layer. An optical fiber and an apparatus for producing it are also provided.

Abstract: An optical waveguide fiber having a high threshold for stimulated Brillouin scattering (SBS). The SBS threshold is increased by an acoustically antiguiding configuration of the fiber. An acoustic configuration comprises one or more acoustic regions having acoustic velocities decreasing from the centerline of the fiber. More preferable configurations have acoustic regions with smaller radial thickness and smaller differences in acoustic velocities among regions.

Abstract: A Low-E glass includes a glass substrate and a multilayer Low-E film formed on at least one surface of the glass substrate. The multilayer Low-E film includes a number of high refractive index layers and a number of low refractive index layers stacked on one another. An innermost layer contacting with the glass substrate is the high refractive index layer. A total number of layers of the multilayer Low-E film is in a range from 30 to 40.

Abstract: An optical fiber, which is less likely to increase its transmission loss even when it is exposed to a high-humidity environment or immersed in water, is provided. The optical fiber comprises a glass fiber and at least two coating layers (a soft layer and a hard layer) coated at the circumference of the glass fiber, wherein the limit-adhesion strength between the glass fiber and the coating layer under a hot and humid environment is 0.50N/10 mm or more. Preferably, the glass-transition temperature of the hard layer is less than 90° C.

Abstract: Disclosed is a resin composition for an optical material which contains a base polymer (A), a photopolymerizable compound (B), and a photopolymerization initiator (C). Also disclosed is a resin film for an optical material which is made of such a resin composition for an optical material. Specifically disclosed is a resin composition for an optical material which has high transparency and high heat resistance, while enabling formation of a thick film with high precision. This resin composition is particularly useful for a resin film which is used for forming optical waveguides. Also specifically disclosed are a resin film for an optical material using such a resin composition and an optical waveguide using such a resin film.

Abstract: Provided is a digital camera module. The digital camera module includes an image sensor generating an electrical signal including a video signal and a clock signal and an optical interconnection unit converting the at least one of the video and clock signals into an optical signal to transmit the converted optical signal. The digital camera module further includes an image signal processor receiving the video signal restored from the optical signal to the electrical signal to convert the received video signal into a signal that is visually displayable.

Abstract: Isolated and/or recombinant enzymes that include surface binding domains, surfaces with active enzymes bound to them and methods of coupling enzymes to surfaces are provided. Enzymes can include large and/or multiple surface coupling domains for surface coupling.

Abstract: According to one example of the invention an optical fiber comprises: (i) a core comprising of Al doped silica having a first index of refraction n1; (ii) at least one silica based cladding surrounding the core and having a second index of refraction n2, such that n1>n2; (iii) a hermetic carbon based coating surrounding said cladding, said hermetic coating being 300 nm-1000 nm thick; and (iv) a second coating surrounding said hermetic coating, said second coating being 5 ?m to 80 ?m thick.

Abstract: The invention consists in an amplifying optical fiber comprising a core containing a dopant and a cladding, wherein said core comprises a monomode core intended to propagate an optical signal, quantum dots of a semiconductor material being disposed in or near said monomode core, and a multimode core surrounding the monomode core, intended to receive a pumping signal.

Abstract: An electro-optic waveguide device comprising an electro-optic polymer core and at least one crosslinked polymer clad, wherein the crosslinked polymer clad is comprised of a first constitutional unit derived from a compound having the formula wherein, m=0-6; n=0-1; q=1-3; y=0-3; Ar1 is an aryl or heteroaryl group; and independently at each occurrence p=0-1; R is an alkyl, heteroalkyl, aryl, or heteroaryl group; Ar2 is an aryl or heteroaryl group; and X is a crosslinkable group. The R group may be an alkyl or heteroalkyl group with at least 6 atoms in a straight chain. In some embodiments, the R group is an alkoxy capped oligoalkylene group. Other embodiments include a polymer comprising a first constitutional unit derived from a compound having the formula described above.

Abstract: The present invention provides a rare-earth ions doped, especially erbium and ytterbium doped transparent electro-optic gain ceramic material consisting lead, zirconium, titanium and lanthanum. The electro-optic gain ceramic material either has a linear electro-optic coefficient or a quadratic electro-optic coefficient, which is greater than about 0.3×10?16 m2/V2 for the latter, a propagation loss of less than about 0.3 dB/mm, and an optical gain of great than 1.5 dB/mm at a wavelength of about 1550 nm while optically pumped by a 1.4 watts diode laser at a wavelength of 970 nm at 20° C. The present invention also provides electro-optic devices including a rare-earth ions doped, especially erbium and ytterbium doped, transparent electro-optic gain ceramic material consisting lead, zirconium, titanium and lanthanum.

Abstract: The present invention relates to an assembly of multiple waveguides which includes a substrate and a plurality of waveguides positioned on said substrate at locations effective to suppress cross-talk between different waveguides. The plurality of waveguides each comprise an elongate array of quantum dots extending between sets of first and second locations on the substrate. The waveguides are positioned to receive: (1) pumped light uniformly applied to the array to produce electron-hole pairs and to enable optical gain and (2) signal light at the first location to trigger an emission from the quantum dot at the first location and transmission of photons along the array to the second location. A light transmission system which includes this assembly as well as methods of making and using the assembly are also disclosed.

Abstract: A suspension board with circuit includes a metal supporting board including a board trench portion, an insulating base layer formed on a surface of the metal supporting board, a conductive pattern formed on a surface of the insulating base layer, and an optical waveguide provided to overlap the board trench portion when projected in a thickness direction of the metal supporting board. At least a part of the optical waveguide is positioned closer to the conductive pattern than to a back surface of the metal supporting board.

Abstract: A method for fabricating a distributed Bragg reflector waveguide is disclosed, which includes forming a first distributed Bragg reflector on a substrate; forming a sacrificial pattern on the first distributed Bragg reflector; forming a second distributed Bragg reflector on the sacrificial pattern and the first distributed Bragg reflector; and removing the sacrificial pattern. A distributed Bragg reflector waveguide is also disclosed.

Abstract: An apparatus for transmitting data at high data rates, between two systems that move relative to one another is provided. The apparatus includes an optical fiber and an axial module on one of the two systems for the purpose of axial data coupling, using the optical fiber and a lateral module on another of the two systems for the purpose of lateral data coupling using the optical fiber.

Abstract: A polarizing film is made of multilayer polarizing fibers embedded within a matrix. The fibers are formed with layers of at least a first and a second polymer material. Layers of the first polymer material are disposed between layers of the second polymer material. At least one of the first and second polymer materials is birefringent. In some embodiments the thickness of the layers of at least one of the materials varies across the fiber, and may include layers are selected as quarter-wavelength thickness for light having a wavelength of more than 700 nm.

Abstract: An optical fiber having: a) a glass portion; and b) at least one protective coating layer disposed to surround the glass portion, the protective coating layer having a modulus of elasticity value between ?40° C. and +60° C. between 5 MPa and 600 MPa, preferably not higher than 500 MPa, more preferably not higher than 450 MPa and much more preferably not higher than 300. Preferably the protective coating layer is a single protective coating layer which is disposed in contact with the glass portion.

Abstract: Step-index optical waveguides are made of multicomponent glass containing a core glass and an outer glass which entirely surrounds the core class. A fiber-optic cable for conducting electromagnetic radiation, contains at least one bundle of individual fibers which encompass the step-index optical waveguides that are made of multicomponent glass containing a core glass and an outer glass that entirely surrounds the core glass on the circumferential wall thereof. These step-index optical waveguides provide great transmission capacity for transmitting data while keeping the transfer characteristics sufficiently durable. Furthermore, the fiber-optic cable is resistant against physical and chemical environmental influences and be protected against radical ambient chemicals.

Abstract: A method of forming an antireflective coating on an electronic device comprising (A) applying to an electronic device an ARC composition comprising (i) a silsesquioxane resin having the formula (PhSiO(3-x)/2(OHx)m HSiO(3-x)/2(OH)x)n, where Ph is a phenyl group, x has a value of 0, 1 or 2; m has a value of 0.05 to 0.95, n has a value of 0.05 to 0.95 and m+n?1; and (ii) a solvent; and (B) removing the solvent and curing the silsesquioxane resin to form an antireflective coating on the electronic device.

Abstract: Disclosed is a resin composition for an optical material which contains a base polymer (A), a photopolymerizable compound (B), and a photopolymerization initiator (C). Also disclosed is a resin film for an optical material which is made of such a resin composition for an optical material. Specifically disclosed is a resin composition for an optical material which has high transparency and high heat resistance, while enabling formation of a thick film with high precision. This resin composition is particularly useful for a resin film which is used for forming optical waveguides. Also specifically disclosed are a resin film for an optical material using such a resin composition and an optical waveguide using such a resin film.

Abstract: A microfabricated light collimating screen is provided. A microfabricated screen, in one form, is made from a photopolymer such as SU-8 material. It is able to collimate light in two dimensions and for improved degrees of collimation. It may also be directly patterned onto image sensors or light sources in order to achieve direct collimation. The fabrication method is large-area compatible and inexpensive. The proposed screens may be useful for position detection of objects, such as in the paper mover, in printers and copy machines.

Abstract: A plurality of optical members (lenses) for use in ultraviolet region are mutually stuck. A fluorine-based organic compound (for example, fluorine-based oil) is provided between them. The periphery of the optical members is sealed with a sealant. As the sealant, an adhesive fluorine resin, for example, a soluble fluorine resin is used.

Abstract: Openings are disposed in an insulating layer to expose a conductor layer. A lower cladding layer is formed, and a resist layer is formed on an insulating layer and the lower cladding layer. Electrolytic plating is performed with using the conductor layer which is connected to the external, as an electrode, to fill openings passing through the lower cladding layer and the resist layer with Cu. The resist layer is removed away to form projections configured by the filled Cu. The projections are processed to have an inclined face. Au layers are formed on the inclined faces of the projection. A core layer and an upper cladding layer are stacked.

Abstract: A resin composition for an optical material, which is excellent in heat resistance and transparency and is soluble in an aqueous alkali solution, a resin film for an optical material made of the resin composition, and an optical waveguide using the same are provided. The resin composition for an optical material includes: (A) an alkali-soluble (meth)acrylate polymer containing a maleimide skeleton in a main chain; (B) a polymerizable compound; and (C) a polymerization initiator. The resin film for an optical material is made of the resin composition for an optical material. The optical waveguide has a core part and/or a clad layer formed using the resin composition for an optical material or the resin film for an optical material.

Abstract: A waveguide device includes a substrate and a first electrode, a first cladding layer, a waveguide, a second cladding layer, and a second electrode sequentially provided on the substrate. At least one of the first cladding layer, the waveguide, and second cladding layer includes a ligand compound which is capable of coordinating to a metal or metal ion.

Abstract: The invention relates to coated optical fibers comprising soft primary coatings and to such primary coatings for protecting glass optical fibers having a sufficient high resistance against cavitation. In particular, the primary coatings have a cavitation strength at which a tenth cavitation appears (?10cav) of at least about 1.0 MPa as measured at a deformation rate of 0.20% min?1 and of at least about 1.4 times their storage modulus at 23° C. The coating preferably shows strain hardening in a relative Mooney plot, preferably has a strain energy release rate Go of about 20 J/m2 or more, and preferably has a low volumetric thermal expansion coefficient. The invention furthermore provides a method and apparatus for measuring the cavitation strength of a primary coating.

Abstract: Disclosed is a fiber amplifier system including a gain fiber having a single-mode core containing dopant ions capable of producing stimulated emission of light at wavelength ?s when pumped with light of wavelength ?p. Absorbing ion filtering means is operatively associated with the gain fiber to alter the gain curve. If the absorbing ions are the same as the gain ions of the gain fiber, the system further includes means for preventing pump light from exciting the gain ions of the filtering means. The excitation prevention means may take the form of means for attenuating pump light. If the absorbing ions are different from the dopant ions of the gain fiber, such absorbing ions can be subjected to light at wavelength ?p, but they will remain unexcited. Such absorbing ions can be used to co-dope the gain fiber, or they can be incorporated into the core of a fiber that is in series with the gain fiber.