Abstract: An inner core has a first refractive index. An outer core having a second refractive index lower than the first refractive index is formed on outer circumference of the inner core. A cladding having a refractive index that is higher than the second refractive index and lower than the first refractive index is formed on outer circumference of the outer core. A diameter of the inner core is enlarged, the second refractive index is decreased, and a center core having a refractive index lower than the first refractive index is formed at a center of the inner core, to increase an effective core area while maintaining wavelength dispersion and bending loss.

Abstract: A microbend-induced fiber grating is formed from a section of optical fiber configured to exhibit “splitting” between the resonant wavelengths supported by the TE and TM components of the LP1m mode and the resonant wavelength supported by the odd/even HE2m components of the LP1m mode. Since only the TE and TM components are polarization dependent, by splitting and shifting the resonant wavelengths for these modes away from a system-desired wavelength(s) supported by the odd/even HE modes, a polarization insensitive microbend-induced fiber grating can be formed. A fiber core configuration including a central core region, trench and ring is formed to exhibit a large radial gradient in core refractive index profile, with a significantly steep transition between the ring index and the trench index, to provide the desired splitting between the (undesired, polarization sensitive) TE/TM modes and the HE mode.

Abstract: The glass fiber for an optical amplifier has a matrix glass core, a first glass cladding, and a second glass cladding. The matrix glass core has a composition, in mol %, of Bi2O3, 30-60; SiO2, 0.5-40; B2O3, 0.5-40; Al2O3, 0-30; Ga2O3, 0-20; Ge2O3, 0-25 ; La2O3, 0-15; Nb2O5, 0-10; SnO2, 0-30; alkali metal oxides, 0-40; and Er2O3, 0.05-8. The glass claddings have the same composition as the core, except that a transition metal compound is included as an absorbent. The refraction index of the matrix glass is > about 1.85, the refraction index of the first glass cladding is less than that of the core, and the refraction index of the second glass cladding is higher than that of the first.

Abstract: An optical fiber, made of silica-based glass, comprising a core and a cladding, each of the optical fiber having a mode field diameter of 5.5 ?m or larger at a wavelength of 1100 nm, transmitting light with a wavelength of 1250 nm in a single mode, and having a bending loss of 1 dB/turn or smaller at a wavelength of 1100 nm when the optical fiber is bent with a curvature radius of 2 mm.

Abstract: The present invention relates to an optical component comprising an acceptance fibre, e.g. a photonic crystal fibre, for propagation of pump and signal light, a number of pump delivery fibres and a reflector element that reflects pump light from the pump delivery fibres into the acceptance fibre. It is an object of the invention to provide a fibre coupler for coupling two or more light sources into a multi-clad (e.g. double clad) optical fibre, which has practical advantages with respect to handling, loss and back reflection.

Abstract: An optical fiber amplifier includes a laser pump source for generating laser pump light; a fiber including an inner cladding layer optically coupled to a laser pump source for receiving laser pump light; a large mode area (LMA) core surrounded by the inner cladding, the LMA core including a confined region having a predetermined doping concentration of rare-earth ions for undergoing excitation to generate laser light when pumped by the laser pump light; and an outer cladding layer surrounding the inner cladding layer for substantially confining the laser pump light to the inner cladding and the LMA core. In a method of forming the optical fiber amplifier, a ratio of an area of the confined region to an area of the LMA core, and the predetermined doping concentration of the rare earth ions are selected so as to achieve a quantum efficiency (QE) gain factor of approximately 2, but such that the heat dissipation per unit length can be controlled by adjusting the area of the confined region.

Abstract: A white light-emitting device using a fluorescent fiber includes a blue semiconductor light-emitting element (2) for emitting an excitation light (a), and an optical fiber (3) having one side end face and the other side end face, the excitation light (a) emitted from the blue semiconductor light-emitting element (2) being made incident to the one side end face to be guided to the other side end face. The optical fiber (3) includes a core containing therein a phosphor for emitting wavelength conversion lights by being excited by the excitation light (a) received from the blue semiconductor light-emitting element (2), and a cladding member (3B) having a light emission surface in its peripheral surface, at least a part of optically multiplexed lights, which are obtained by optically multiplexing the wavelength conversion lights and the excitation light, being emitted through the light emission surface.

Abstract: An optical fiber includes a core region and a cladding region. The cladding region includes a first cladding region on an outer circumference of the core region, the first cladding region including a main-medium region and a sub-medium region having a refractive index lower than a refractive index of the main-medium region. The sub-medium region includes inner sub-medium regions arranged at four folds rotationally symmetric centering on the core region, and outer sub-medium regions arranged at four folds rotationally symmetric centering on the core region on an outer side of the inner sub-medium regions.

Abstract: An optical fiber including: (i) a silica based, Yb doped core having a first index of refraction n1, said core comprising more than 1 wt % of Yb, said core having less than 5 dB/km loss at a wavelength situated between 1150 nm and 1350 nm and less than 20 dB/km loss at the wavelength of 1380 nm and slope efficiency of over 0.8; and (ii) at least one silica based cladding surrounding the core and having a second index of refraction n2, such that n1>n2.

Abstract: An optical fiber, which has a zero-material dispersion wavelength equal to or greater than 2 ?m, and a high nonlinear susceptibility ?3 equal to or greater than 1×10?12 esu, and uses tellurite glass having sufficient thermal stability for processing into a low loss fiber, employs a PCF structure or HF structure having strong confinement into a core region. This enables light to propagate at a low loss. The size and geometry of air holes formed in the core region, and the spacing between adjacent air holes make it possible to control the zero dispersion wavelength within an optical telecommunication window (1.2-1.7 ?m), and to achieve large nonlinearity with a nonlinear coefficient ? equal to or greater than 500 W?1 km?1.

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 core region is doped with an impurity. A first cladding region is formed in a layered structure around the core region, including a microstructure. A second cladding region is formed in a layered structure around the first cladding region, including a homogeneous material. A relative refractive-index difference ?1 between the core region and the second cladding region is equal to or more than 0.4% and equal to or less than 1.0%.

Abstract: An optical fiber in which the macro-bending loss is lowered while an MFD is maintained large, and a waveguide including the optical fiber. The optical fiber includes a core region doped with an impurity; a first cladding region formed as a layer around the core region and including holes as microstructures; and a second cladding region formed as a layer around the first cladding region and made of a homogeneous material. A relative refractive-index difference ?1 between the core region and the second cladding region is equal to or higher than 0.01% and lower than 0.3%. A total cross-sectional area of the holes in the first cladding region with respect to a total cross-sectional area of the core region, the first cladding region, and the second cladding region is equal to or smaller than 20%. A waveguide is formed using the optical fiber.

Abstract: A dispersion compensating optical fiber for NZ-DSFs, includes: an uncovered dispersion compensating optical fiber; a double-layered resin coating disposed around the uncovered dispersion compensating optical fiber; and an outer coating layer having a thickness of 3 to 7 ?m, containing silicone in an amount of 1 to 5% by weight, and disposed around the double-layered resin coating. The outer diameter of the uncovered dispersion compensating optical fiber is in a range from 90 to 125 ?m, an outer diameter of the dispersion compensating optical fiber is in a range from 180 to 250 ?m, and the amount of silicone contained in the outer coating layer is determined such that an adhesive property of the outer coating layer is 1 gf/mm or less.

Abstract: An optical fiber transmits at least a signal light having a wavelength of 1550 nanometers in a fundamental propagation mode. The optical fiber has, a cutoff wavelength equal to or longer than 1550 nanometers, a wavelength dispersion of 4 ps/nm/km to 7 ps/nm/km in the fundamental propagation mode at the wavelength of 1550 nanometers, a dispersion slope of a positive value equal to or smaller than 0.03 ps/nm2/km in the fundamental propagation mode at the wavelength of 1550 nanometers, an effective core area equal to or larger then 60 ?m2 in the fundamental propagation mode at the wavelength of 1550 nanometers, and a bending loss equal to or smaller than 20 dB/m with a winding of 16 turns at a diameter of 20 millimeters in the fundamental propagation mode at the wavelength of 1550 nanometers.

Abstract: A double core optical fiber is provided, in which single mode signal light and multimode signal light can be transmitted and a multimode transmission of the signal light guided through the core can be reduced even when the optical fiber is bent. The double core optical fiber of the present invention includes a core (111) arranged on a central axis of the optical fiber and having a refractive index (112), a first cladding (121) arranged on the outer circumference of the core (111) and having a refractive index (122) smaller than the refractive index (112), and a second cladding arranged on the outer circumference of the first cladding (121) and having a refractive index (132) smaller than the refractive index (122).

Abstract: A single-mode optical fiber segment incorporating liquid-filled holes parallel to the core that are sealed at each end. Heating the liquid produces stress in the fiber and thereby increases the birefringence level. Alternatively the holes may be filled and sealed at a temperature lower than the temperature at which the fiber will be operated, the temperature difference determining the stress level for given hole characteristics.

Abstract: There is disclosed an optical fiber wherein an absolute value of the fourth order dispersion ?4 of fourth derivative ?4 of propagation constant ? with respect to angular frequency ? at a mean zero dispersion wavelength ?0 in an overall length is not more than 5×10?56 s4/m and wherein a fluctuation of a zero dispersion wavelength along a longitudinal direction is not more than ±0.6 nm.

Abstract: The specification describes an optical fiber device wherein a LOM is converted to an HOM prior to entering the gain section. The gain section is a few mode fiber that supports the HOM. The output from the gain section, i.e. the HOM, may be utilized as is, or converted back to the LOM. With suitable design of the few mode fiber in the gain section of the device, the effective area, Aeff, may be greater than 1600 ?m2. The large mode separation in the gain section reduces mode coupling, allowing greater design freedom and reducing the bend sensitivity of the optical fiber.

Abstract: An optical fiber comprising a multimode glass core having a diameter of at least 250 microns and an index of refraction and a polymer cladding having a thickness and contactingly surrounding a glass portion of the fiber so as to define an interface between the glass portion and the polymer cladding. The polymer cladding can have a first index of refraction that is less than the index of refraction. The fiber can comprise a density of less than 0.25 non-conforming regions having a diameter of 25 microns or greater per millimeter of length along the fiber, where each of the non-conforming regions is a region visible to the human eye under an optical microscope and having at least a portion thereof within a selected distance of the interface. The selected distance can be less than or equal to the thickness of the polymer cladding. The optical microscope can have a total magnification of about 200. The polymer cladding can be applied to at least a part of the optical fiber in at least a class 1000 environment.

Abstract: The invention relates to the field of components with optical fibers and of associated optical fibers. The invention relates, on the one hand, to a component with optical fiber including an at least partly bent optical fiber (2) which successively comprises, from the center to the periphery, an optical core (10) based on silica, an optical cladding (11) based on silica, and a coating (12) having a transparency to infrared radiation larger than 85%. On the other hand, the invention relates to an optical fiber, successively comprising, from the center to the periphery, an optical core (10) based on silica, an optical cladding (11) based on silica, and a coating (12) having a transparency infrared radiation larger than 85%.

Abstract: A germanate glass composition suitable for use in a fiber amplifier for broadband amplification of optical signals is provided. The glass preferably includes 35-75% GeO2, 0-45% PbO, 5-20% BaO, 5-20% ZnO, and 2-10% R2O (R=Na, Li, K). It is doped with thulium ions (Tm3+) and codoped with holmium ions (Ho3+). The glass composition of the invention results in a remarkably large bandwidth as compared with previous glasses. It is also highly compatible with existing silica optical fibers.

Abstract: An optical fiber transmits at least a signal light having a wavelength of 1550 nanometers in a fundamental propagation mode. The optical fiber has a cutoff wavelength equal to or longer than a wavelength of 1550 nanometers, a wavelength dispersion in the fundamental propagation mode at the wavelength of 1550 nanometers larger than 0 ps/nm/km, and a dispersion slope in the fundamental propagation mode at the wavelength of the signal light equal to or smaller than ?0.05 ps/nm2/km.

Abstract: An optical fiber is made of silica-based glass, and includes a core and a cladding. The optical fiber has a mode field diameter of 5.4 micrometers or larger at a wavelength of 1300 nanometers, transmits light with a wavelength of 1250 nanometers in a single mode, and has a bending loss of 1 dB/turn or smaller at a wavelength of nanometers when the optical fiber is bent with a curvature radius of 1 millimeter.

Abstract: An optical fiber comprising: a glass core extending from a centerline to a radius R1; a glass cladding surrounding and in contact with the core, the cladding comprising: a first annular region extending from R1 to a radius R2, the first annular region comprising a radial width, W2=R2?R1, a second annular region extending from R2 to a radius R3, the second annular region comprising a radial width, W3=R3?R2, and a third annular region extending from R3 to an outermost glass radius R4; wherein (i) the core comprises a maximum relative refractive index, ?1MAX, relative to the third annular region; (ii) wherein the first annular region comprises a radial width W2; and (iii) the second annular region comprises a minimum relative refractive index, ?3MIN, relative to the third annular region wherein ?1MAX>?2MAX>?3MIN, and ?2MIN>?3MIN; and the core and the cladding provide a fiber with cable cutoff less than 1500 nm, dispersion at 1550 nm less than 12 ps/nm/km, effective area at 1550 nm greater than 60 ?m2, a

Abstract: An optical fiber, comprising: a core with a first refractive index (n1); a silica based outer cladding surrounding the core, the outer cladding having a refractive index (n), such that the core is substantially surrounded by a gap situated between the core and the outer cladding, the gap containing at least one support structure adjacent to the outer cladding and situated between the outer cladding and the core, wherein the support structure is either hollow or gas filed and is not connected to any other support structure situated within the gap.

Abstract: A waveguide configuration comprising an optical core, an optical cladding, an acoustic core and an acoustic cladding. The acoustic core has two regions. The first region radial thickness is smaller than the optical core radial thickness and the sum of the first region radial thickness and the second region radial thickness is greater than the optical core radial thickness. The first region acoustic velocity is greater than the second region acoustic velocity and the acoustic cladding acoustic velocity is greater than the second region acoustic velocity. In one variation, the first region acoustic velocity is less than the second region acoustic velocity and the acoustic cladding acoustic velocity is less than the second region acoustic velocity.

Abstract: An improved device and method for safer and more efficient laser vein treatments are presented. The device includes an optical waveguide optically coupled to a radiation source at its proximal end, having a core, a cladding layer and a tip configured to protect the clad-core, e.g., from contact with collapsing vein walls during laser vein treatment, and to enhance treatment efficiency through improved centering. According to one embodiment, the clad-core is recessed within one or more jacket layers. In some embodiments, the protective jacket on the clad-core may be left on when the jacket layer is added. In embodiments, one or more protective wires are attached to the clad-core or a jacket layer and extend distally past the clad-core. In some such embodiments, three protective wires are substantially equally spaced relative to each other about the circumference of the core, i.e., forming an equilateral triangular pattern.

Abstract: The present invention concerns an optical fiber 10 comprising a substantially pure silica glass core 12, a concentric tin-doped core/cladding interface region 14, and a concentric fluorine-doped depressed cladding layer 16. The tin-doped core/cladding interface region 14 comprises a low concentration gradient of tin dioxide, which advantageously results in a de minimis refractive index change, resistance to hydrogen incursion, and thermal stability of any fiber Bragg gratings written into the interface region 14.

Abstract: Optical fibers to form an optical transmission line suitable for WDM transmission in a wide-spreading wavelength band, having the following characteristics and parameters: a dispersion in absolute value of 0.5 ps/nm/km to 9 ps/nm/km in a wavelength band of 1430 nm to 1625 nm, a dispersion slope in absolute value of 0.04 ps/nm2/km or less at a wavelength of 1550 nm, a mode field diameter of 7 ?m or less at a wavelength of 1550 nm and a cable cutoff wavelength of less than 1430 nm; core 11 surrounded by cladding 7, core 11 being at least two-layered (first layer 1 at the center and second layer 2 surrounding the first layer; relative refractive index of glass layer ?1 with reference to the cladding being adjusted to not less than 0.6 but not more than 1.6%, relative refractive index of second layer ?2 with reference to the cladding being adjusted to a negative value.

Abstract: A fiber optic connector having a double-clad specialty optical stub fiber with a deep index core-to-inner-cladding profile and a raised index outer-cladding profile. The double-clad optical stub fiber abuts against a single-clad field optical fiber of the single-mode type to form an interface across which the primary mode traverses without significantly interfering with higher-order modes. The ratio of the radius of the inner cladding to the radius of the core of the stub fiber is less than 6.5:1. The index profile of the refractive index of the inner cladding is deep relative to the refractive index of the core to confine the primary mode within the core. The raised refractive index of the outer-cladding pulls the higher-order modes deeper into that region, reducing interference with the primary mode. The respective core diameters of the field and stub fibers are matched to avoid mode-field diameter mismatch.

Abstract: A large mode area optical fiber is configured to support multiple transverse modes of signal radiation within its core region. The fiber is a hybrid design that includes at least two axial segments having different characteristics. In a first axial segment the transverse refractive index profile inside the core is not radially uniform being characterized by a radial dip in refractive index. The first segment supports more than one transverse mode. In a second axial segment the transverse refractive index profile inside the core is more uniform than that of the first segment. The two segments are adiabatically coupled to one another. Illustratively, the second segment is a terminal portion of the fiber which facilitates coupling to other components. In one embodiment, in the first segment M12>1.0, and in the second segment M22<<M12. In a preferred embodiment, M12>>1.0 and M22˜1.0. In another embodiment, the optical fiber is coupled to a fiber stub.

Abstract: The invention concerns a method for making an optical fiber (18) including the following steps: producing a preform (10) containing nanoparticles provided with an active element including at least one recess (14) proximate at least part of the nanoparticles; fiber drawing of the preform (10) by introducing a non-oxidizing gas in the recess (14), thereby limiting the risks of oxidizing the nanoparticles of the preform (10). The preform (10) designed to the manufacture of an optical fiber (18) by the inventive method comprises nanoparticles provided with an active element in a doped zone (12) and at least one recess (14) proximate the doped zone (12).

Abstract: A tension-absorbing cladding layer is formed around a cladding layer, with a refractive index equal to that of a center core region or higher. The center core region has a relative refractive index difference of ?0.1% to 0% with respect to a pure silica glass, a chlorine concentration of wt % to 0.10 wt %, and a fluorine concentration of 0.10 wt % to 0.30 wt %. The tension-absorbing cladding layer has a relative refractive index difference of 0% to 0.05% with respect to the pure silica glass and a chlorine concentration of 0.15 wt % or lower. A ratio of an outer diameter of the tension-absorbing cladding layer to an outer diameter of the cladding layer is 1.10 to 1.40.

Abstract: Disclosed is an optical fiber suitable for WDM system, particularly whose zero-dispersion wavelength is positioned in a short wavelength band less than 1,300 mm. In the optical fiber, dispersion has a positive value, not zero, at 1,310 nm, and a dispersion slope is positive at 1,550 nm with dispersion of 25 ps/nm-km or less. In addition, an effective sectional area is 65 ?m2 or less at 1,310 nm, and 80 ?m2 or less at 1,550 nm. Thus, though a transmission signal is Raman-amplified at a wavelength band of 1,300˜1,700 nm, transmission characteristics are not deteriorated due to crosstalk between pump signals. In addition, since the optical fiber has smaller effective sectional area than a general single-mode optical fiber with having substantially the same dispersion feature, it gives better Raman gain efficiency than a general single-mode optical fiber.

Abstract: An optical waveguide includes an optical waveguide main body and mirrors. The optical waveguide main body includes a first cladding layer, a second cladding layer and a core portion provided between the first cladding layer and the second cladding layer. The optical waveguide main body has a first region in which the core portion and the mirrors are arranged and the light signal is transmitted, and a second region arranged on both sides of the first region and not contributing to a transmission of a light signal. Through vias that pass through the optical waveguide main body is provided in the second region. The first region on a side that faces the light emitting element or the light receiving element is protruded larger than the second region on a side that faces the light emitting element or the light receiving element.

Abstract: An optical fiber adapted to carry optical power for powering an electrical device and also optionally adapted to carry optical data for signal processing. The optical fiber capable of carrying both optical data and optical power includes a central data waveguide region that carries data light and an annular power waveguide region concentrically surrounding the data waveguide region and adapted to carry relatively large amounts of optical power. A first annular isolation region between the data and power waveguide regions and that includes microstructures serves to optically isolate the waveguide regions. An outer annular isolation region serves to confine power light to the power waveguide region and contributes to the bend-resistance of the optical fiber. An optical power and optical data distribution system that utilizes the optical fiber is also described.

Abstract: Microstructured optical fiber and method of making. Glass soot is deposited and then consolidated under conditions which are effective to trap a portion of the consolidation gases in the glass to thereby produce a non-periodic array of voids which may then be used to form a void containing cladding region in an optical fiber. Preferred void producing consolidation gases include nitrogen, argon, CO2, oxygen, chlorine, CF4, CO, SO2 and mixtures thereof.

Abstract: A method of making an optical fiber article can include providing an optical fiber including at least a core; providing a preform; and subsequent to the foregoing providing of the optical fiber and the preform, drawing the preform so as to dispose a region about the optical fiber. An optical fiber article can include a core; a pump cladding disposed about the core, the pump cladding for propagating pump light; and a second cladding disposed about the pump cladding, where the second cladding can provide a photonic bandgap for tending to confine pump light to a region about which the second cladding is disposed. The second cladding can comprise a plurality of layers including a first layer having a different optical property than a second layer, and the plurality of layers can be arranged as to provide the photonic bandgap effect.

Abstract: Optical waveguide fiber that is bend resistant and single moded at 1260 nm and at higher wavelengths. The optical fiber includes a core and cladding, the cladding having an annular inner region, an annular ring region, and an annular outer region. The annular ring region has a low relative refractive index.

Abstract: A waveguide configuration comprising a core, a first cladding, a second cladding, and a buffer. The core includes an index of refraction and an acoustic shear velocity. The first cladding extends about the core and has an acoustic shear velocity which is less than that of the core and an index of refraction which is less than the core. The second cladding extends about the first cladding. The second cladding has an acoustic shear velocity which is greater than that of the first cladding and less than the acoustic shear velocity of the core. The second cladding has an index of refraction which is less than that of an optical mode. The buffer extends about the second cladding.

Abstract: A method and apparatus for imaging using a double-clad fiber is described.

Abstract: Described herein is a method for making a depressed index cladding for the inner cladding of an optical fiber. The method involves making the depressed index cladding in two steps. The innermost portion of the inner cladding is produced using a soot method, thereby deriving the advantages of the soot method for the region of the cladding that carries the most optical power, then forming the remaining portion of the inner cladding layer using a rod-in-tube step. This method effectively marries the advantages and disadvantages of both methods.

Abstract: A waveguide includes a cladding region that has a refractive index that is substantially uniform and surrounds a wave-guiding region that has an average index that is close to the index of the cladding. The wave-guiding region also contains a thin ring or series of rings that have an index or indices that differ significantly from the index of the cladding. The ring or rings enable the structure to guide light.

Abstract: The present invention relates to an optical fiber for an optical amplifier and a method for manufacturing the same, which can be applied to an optical transmission system in the S-band area (4130 nm-1530 nm). According to the present invention, silica is used as a base material and the optical fiber for an optical amplifier contains Tm3+ ions and metal ions in a first core layer formed on an inner surface of a second core layer using the MCVD (Modified Chemical Vapor Deposition) method and a solution doping method whereby the practicability and productivity of the optical fiber are remarkably improved.

Abstract: An optical fiber not only can suppress SBS but also can be produced easily. The optical fiber 1 comprises an optical core region 10 including the center axis and an optical cladding region 14 surrounding the optical core region 10. The optical core region 10 is composed of a first region 11, a second region 12, and a third region 13 in this order from the inside. The third region 13, which is a part of the optical core region 10, is a ring-shaped acoustic core region. The propagation mode of an acoustic wave can be localized in the third region 13.

Abstract: A single-mode optical fiber has a cut-off wavelength of 1260 nm or less, a zero-dispersion wavelength in the range of 1300 nm to 1324 nm, a zero-dispersion slope of 0.093 ps/nm2/km or less, a mode field diameter at a wavelength of 1310 nm in the range of 5.5 ?m to 7.9 ?m, and a bending loss of 0.5 dB or less at a wavelength of 1550 nm, the bending loss being produced when the fiber is wound around a 10-mm radius for 10 turns.

Abstract: An optical fiber for Raman amplification amplifies a signal light with a pumping light. A chromatic dispersion at a wavelength of 1,550 nm is in a range between ?70 ps/nm/km and ?30 ps/nm/km. Raman gain efficiency with a pumping light of 1,450 nm is equal to or more than 5 (W×km)?1. Nonlinear coefficient at the wavelength of 1,550 nm is equal to or less than 5.0×10?9 W?1. Zero-dispersion wavelength is neither at a wavelength of the signal light nor at a wavelength of the pumping light. Cut-off wavelength is equal to or less than the wavelength of the pumping light.

Abstract: Provided is an optical fiber. The optical fiber includes a core and a cladding, the core containing a first element for inducing non-linear Raman phenomenon, and the cladding containing a second element which is a rare earth element, wherein when the optical fiber is pumped by two pumping light sources having different wavelengths with each other, the optical signals in the first and third band are Raman-amplified by the first element and the signals in the second band are amplified by a direct transition of the second element.

Abstract: A dispersion optimized optical fiber for wideband optical transmission is disclosed. The fiber comprise centre core, inner cladding, ring core, outer cladding and outer glass region, characterized by inner cladding provided onto outer periphery of the centre core, ring core, ring core provided onto outer periphery of inner cladding, outer cladding provided onto outer periphery of ring core, and outer glass region surrounding outer cladding, wherein refractive indices of various regions of the fiber are related in a manner that centre core has higher refractive index than that of ring core, ring core has higher refractive index than that of outer glass region, outer cladding has equal to or lower refractive index than that of outer glass region, and inner cladding has lower refractive index than that of outer cladding region, that is the refractive index of various regions of the fiber is related by relationship n1>n3>n5?n4>n2 or the relationship Del1>Del3>Del5?Del4>Del2.