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: Microstructured optical fiber for transmitting optical signals comprised of light, the optical fiber including a core region and a cladding region surrounding the core region, the cladding region including at least one annular region having an index of refraction lower than that of the remainder of the cladding. The optical fiber provides an absolute SBS threshold in dBm greater than about 9.3+10log[(1?e?(0.19)(50)/4.343)/(1?e?(?)(L)/4.343)], wherein L is the length in km and ? is the attenuation in dB/km at 1550 nm, and a fiber cutoff wavelength of less than 1400 nm.

Abstract: In a LMA optical fiber the index of the core region is graded (i.e., as viewed in a radial cross-section) and has a grading depth of ?ng, as measured from a central maximum at or near the axis to a lower level that is not greater than the central maximum and not less than the index of the cladding region. When the fiber is to be bent at a bend radius, the grading depth, the radius of the core region, and the difference between the central maximum index and the cladding region index are configured to reduce bend distortion. They may also advantageously be configured to maximize the effective mode-field area of the fundamental mode, suppress higher order modes, and reduce bend loss. In a preferred embodiment, the core region includes a centralized gain region, which in turn includes a dark region that is no more than 30% of the area of the gain region. Also described is a method of making such LMA fibers.

Abstract: An optical transmission medium includes a GI optical fiber that is made of silica glass. The GI optical fiber includes a core having a graded-index refractive index profile and a cladding formed around the core. The GI optical fiber is bent by equal to or more than a quarter turn with a curvature radius equal to or larger than 4 mm and equal to or smaller than 10 mm.

Abstract: An optical multimode fiber including a graded index core and an extended gradient core which has a negative refractive index difference with respect to the cladding. The fiber improves the bandwidth, reliability and complexity of the telecommunication systems that are based on multimode fibers. The fiber reduces the differential mode delay among modes. The fiber thereby allows achieving large bandwidth even in the case when the highest order modes are excited. This has positive effects to the conditions that need to be fulfilled by the components such as optical sources, connectors, fiber couplers, other optical components, cables, etc. The fiber eliminates negative impact of the cladding that allows for reduction of fiber core size and the difference between the cladding and the core and thereby allows for achieving the larger bandwidth of optical fiber at lower fiber production cost.

Abstract: An optical fiber has a refractive index profile approximated by n(r)=n1[1?2(?1/100)(r/a)??]1/2 when 0<r?a, and n(r)=n1[1?2(?1/100)]1/2 when a<r, where n1 is refractive index at the center of a core, ?1 is relative refractive index difference between the center of the core and a cladding, a is radius of the core, ? is refractive index profile parameter, and ? represents an exponential. ? is 1.95 to 2.15. The relative refractive index difference is 1.5% or larger. A diameter of the core is 20 ?m to 45 ?m. A diameter of the cladding is 70 ?m to 90 ?m. A bending loss at 850 nm when bending the optical fiber with a curvature radius of 5 mm is 0.1 dB/turn or lower.

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: 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: 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: The present invention includes apparatus and method of a variable step size dithering control algorithm for polarization mode dispersion controllers (PMDCs). The dithering step size of the PCs is adjusted according to the feedback signal including degree of polarization (DOP).

Abstract: A core rod is inserted into a cladding pipe, moisture in a space between the core rod and the cladding pipe is removed, and an optical fiber is drawn while the space is connected to a dry-gas atmosphere and/or being decompressed and while the core rod and the cladding pipe are being unified with each other. Alternatively, the core rod is inserted into the cladding pipe, and an optical fiber is drawn from one end while moisture on the surface of the core rod and the internal surface of the cladding pipe is being removed. Accordingly, a high quality optical fiber is manufactured with good productivity.

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: 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: Optical fibers and optical fiber lasers including gratings and methods of writing gratings into fibers. A method can comprise providing a photosensitive optical fiber having a region having an original refractive index (RI) profile along the elongate direction of the fiber; exposing the optical fiber to actinic radiation to alter the original RI profile to form along a length of the fiber a grating having a RI profile including alternating higher RI and lower RI sections; and wherein the maximum RI difference between a RI of a higher RI section and a RI of an adjacent lower RI section of the grating RI profile is no greater than 85% of the difference between the average index of the grating RI profile and the original RI profile.

Abstract: The present invention relates to a method for manufacturing a preform for optical fibres by means of a vapour deposition process, wherein plasma conditions are created, and wherein the plasma is moved back and forth along the longitudinal axis of the hollow substrate tube between a reversal point near the supply side and a reversal point near the discharge side of the hollow substrate tube, wherein a transition deposition is carried out between the deposition of one phase and the deposition of the other phase.

Abstract: A method of inducing birefringence in an optical waveguide is disclosed wherein the waveguide cladding is irradiated with energy of a sufficient intensity so as to induce a stress in the optical waveguide so as to cause a multitude of spaced stress induced regions within the cladding of the optical waveguide such that there are 10 to 5000 spaced regions per mm and wherein the stress induced regions are proximate the core greater than 2 microns distance from the core-cladding interface. This waveguide has numerous uses, for example a fiber sensor.

Abstract: A waveguide element 21 including a photonic crystal waveguide including a core 4 that is constituted by a photonic crystal having a refractive index periodicity at least in one direction, and that propagates an electromagnetic wave in a direction in which the photonic crystal does not have the refractive index periodicity. At least one of materials forming the core 4 constituted by the photonic crystal, and at least a portion of a cladding in contact with a side face of the core 4 are constituted by a fluid 6. Thus, it is possible to provide a waveguide element that can be used as a light control element, can be produced easily and also can be applied to an optical sensor.

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 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: 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: 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 fiber includes a core and a cladding, said cladding having a refractive index nc a first coating directly contacting the cladding of said fiber, said coating having a thickness of less than 10 microns, said coating having a refractive index delta %=100×(ni2-nc2)/2ni2 less than ?1 percent. In another aspect, an optical fiber includes a core and a cladding, said cladding having a refractive index nc, a first coating directly contacting the cladding of said fiber, said fiber comprising a glass diameter less than 100 microns, said coating having a thickness of at least 8 microns, said coating having a refractive index delta %=100×(ni2-nc2)/2ni2 less than ?1 percent.

Abstract: An optical fiber according to an embodiment of the present invention comprises: a glass core extending from a centerline to a radius R1 wherein R1 is greater than about 5 ?m; a glass cladding surrounding and in contact with the core, the cladding comprising: (i) a first annular region extending from the radius R1 to a radius R2, the first annular region comprising a radial width, W2=R2?R1, (ii) a second annular region extending from the radius R2 to a radius R3, and comprising a radial width, W3=R3?R2, and (iii) a third annular region surrounding the second annular region and extending from the radius R3 to an outermost glass radius R4; wherein the core comprises a maximum relative refractive index, ?1MAX, relative to the third annular region, and wherein ?1MAX is greater than about 0.1% and less than about 0.3%; the first annular region has a refractive index delta ?2(r) is less than about 0.

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 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: 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 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 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 large diameter optical waveguide, grating, and laser includes a waveguide 10 having at least one core 12 surrounded by a cladding 14, the core propagating light in substantially a few transverse spatial modes; and having an outer waveguide dimension d2 of said waveguide being greater than about 0.3 mm. At least one Bragg grating 16 may be impressed in the waveguide 10. The waveguide 10 may be axially compressed which causes the length L of the waveguide 10 to decrease without buckling. The waveguide 10 may be used for any application where a waveguide needs to be compression tuned, e.g., compression-tuned fiber gratings and lasers or other applications. Also, the waveguide 10 exhibits lower mode coupling from the core 12 to the cladding 14 and allows for higher optical power to be used when writing gratings 16 without damaging the waveguide 10. The shape of the waveguide 10 may have other geometries (e.g.

Abstract: Methods and apparatus provide for birefringent waveguides suitable for optical systems exhibiting polarization dependence such as interferometer sensors including Sagnac interferometric fiber optic gyroscopes (IFOG). The waveguides, for some embodiments, may offer single polarization performance over lengths of about a kilometer or more due to polarization dependent attenuation. According to some embodiments, the waveguides incorporate a pure silica core for resistance to radiation-induced attenuation (RIA).

Abstract: An optical fiber having a given refractive index profile comprises a core region and a cladding region. The core region includes at least two co-dopants and the concentration of at least one of said core dopant varies continuously over the entire core region. The optical fiber has, at a wavelength of 1550 nm, a spontaneous Brillouin spectrum width equal or larger to 100 MHz. The optical fiber of the invention achieves a much higher Brillouin threshold compared to standard transmission fibers with limited fiber loss, less than 0.3 dB/km at a wavelength of 1550 nm, and without change in the optical transmission parameters of the fiber.

Abstract: A plastic optical fiber (11) has a core (12) and a clad (13). The clad (13) is composed of an outer clad (14) and an inner clad (15). The refractive index in the core (12) gradually increases as the distance from the center thereof decreases. The refractive index in the inner clad (15) is equal to the minimum value of the refractive index in the core (12), and the refractive index in the outer clad (14) is smaller than that in the inner clad (15). For the purpose of decreasing the transmission loss between the plastic optical fiber (11) and a light emission device or the light receiving device, the diameter d1 of the core (12) and the outer diameter d2 of the inner clad (15) satisfy the following conditions; 100(?m)?d1?700(?m) 200(?m)?d1?1000(?m) d1<d2.

Abstract: An optical waveguide environmental sensor is provided that is capable of detecting a target gas or liquid in the ambient environment in an advantageously short period of time. The waveguide is preferably in the form of an optical fiber having a cladding that contains a photonic band gap structure which in turn envelopes a light conducting, hollow core portion. The cladding further includes at least one elongated side opening that preferably extends the entire length of the fiber and exposes said hollow core portion to the ambient environment, which provides broad and nearly immediate access of the core portion to gases and liquids in the ambient environment, thereby minimizing sensor response time. The ambient gases or liquids filling the hollow core portion and elongated opening function as a ridge and slab, respectively, of an optical ridge waveguide that effectively supports at least one bound optical mode.

Abstract: Using a compound of the following formula (1) makes it possible to provide an optical device having a reduced transmission loss. wherein R1 is an alkyl group having from 1 to 3 carbon atoms and having at least one fluorine atom, and R2 is an alkylene group having 1 or 2 carbon atoms.

Abstract: An air-clad optical fiber is provided having a core that is surrounded by an inner cladding region, an air-clad region, and an outer region. A lead end of the air-clad optical fiber is prepared for splicing by removing the air-clad region and all fiber regions outside of the air-clad region, so as to expose an inner fiber region. The prepared lead end of the air-clad optical fiber is then spliced to a lead end of the optical device. The air-clad region may be removed from a selected portion of an air-clad fiber by causing an etchant gas to stream through the air-clad region in the selected portion of the fiber. Heat is then applied to the selected fiber portion, causing at least some of the microstructure to be etched away.

Abstract: An optical medium has a graded effective refractive index with a high maximum refractive index change. The medium is formed using alternating layers of two or more materials having significantly different refractive indices. The thickness of the layers of at least one of the materials is substantially less than the effective light wavelength of interest. The effective index of refraction in a local region within the medium depends on the ratio of the average volumes of the two materials in the local region. A graded index of refraction is provided by varying the relative thicknesses of the two materials.

Abstract: Optical fiber having a multimode core (10) comprising:—a first zone (11), which is homogeneous, made of a first material, which has a first refractive index;—a second zone (12) made of at least one second material, which has a second refractive index, which is less than the first index, that second zone (12) being peripherally arranged with respect to the first zone (11), said first and second zones being configured so that the interface between those zones defines, in a transverse plane, a contour which has a star shape such that the multimode transmission characteristics of the fiber are equivalent to those of a graded-index fiber. Application in dual-core amplifying fibers or lasers or in transmission fibers for local networks.

Abstract: A silicate optical fiber comprises a graded index silicate core co-doped with aluminum oxide, phosphorus oxide, germanium oxide and fluorine in unique compositions that we have discovered allow multimode, multi-wavelength operation without significant intermodal dispersion. Illustratively, the core comprises a multiplicity of compositions whose refractive indices are graded from a maximum at or near the center of the core to a minimum at the interface with the cladding. Each core composition resides within a sub-volume of a 5 dimensional phase space in which an optimum core profile shape is essentially constant over the wavelength range of operation of the fiber. For operation in the wavelength range of about 0.78 ?m to 1.55 ?m, each composition preferably comprises no more than approximately 6 mole % Al2O3, 9 mole % P2O5, 6 mole % GeO2, 6 mole % F, and 90-100 mole % SiO2.

Abstract: An optical waveguide environmental sensor is provided that is capable of detecting a target gas or liquid in the ambient environment in an advantageously short period of time. The waveguide is preferably in the form of an optical fiber having a cladding that contains a photonic band gap structure which in turn envelopes a light conducting, hollow core portion. The cladding further includes at least one elongated side opening that preferably extends the entire length of the fiber and exposes said hollow core portion to the ambient environment, which provides broad and nearly immediate access of the core portion to gases and liquids in the ambient environment, thereby minimizing sensor response time. The ambient gases or liquids filling the hollow core portion and elongated opening function as a ridge and slab, respectively, of an optical ridge waveguide that effectively supports at least one bound optical mode.

Abstract: A silica based glass waveguide having almost the same optical characteristics as designed value and an optical module using a silica based glass waveguide having excellent optical characteristics and reduced connecting loss are provided. A silica based glass waveguide is comprising a core waveguide and a clad, a core waveguide is formed rectangular in cross section and of SiO2—TiO2 group glass on a synthetic silica glass substrate, and a clad is formed of SiO2—B2O3—P2O5 group glass or etc. on a synthetic silica glass substrate and a core waveguide. A synthetic silica glass substrate is formed of pure SiO2 and having birefringence quantity less than 10 nm/cm.

Abstract: An interface device for performing mode transformation in optical waveguides includes an optical waveguide core for propagating light of a particular wavelength or a plurality of wavelengths. The optical waveguide core terminates in a subwavelength grating configured to change the propagation mode of the light. The subwavelength grating has a pitch sufficiently less than the wavelength of the light to frustrate diffraction. The device can thus serve as an optical coupler between different propagating media, or as an anti-reflective or high reflectivity device.

Abstract: This invention not only provides a graded-index optical member which has heat resistance of 100° C. or more in simple process, but also provides a manufacturing method of a graded-index optical member which can produce a small optical module nearly equal to a diameter of an optical fiber and used for optical communication or an optical network. A graded-index optical member 105 includes a core section 102 which has a maximum portion of a refractive index at a substantial center of a cross-section, and has a refractive index distribution that a refractive index decreases according to distance from the maximum portion. A clad section 103 contacts at least partially with a periphery of the core section 102. Refractive index is substantially uniform, by making a concentration distribution of siloxane structure, where concentration increases according to distance from the maximum portion of the refractive index of the core section 102, formed in a sheet-like polysilane 101.

Abstract: An optical fiber comprising: (i) a silica based passive core having a first index of refraction n1; (ii) a silica based cladding surrounding the core and having a second index of refraction n2, such that n1>n2, said cladding having at least one stress rod and at least one air hole extending longitudinally through the length of said optical fiber; and (iii) wherein said optical fiber supports a single polarization mode or poses polarization maintaining properties within the operating wavelength range.

Abstract: An end face structure of an optical fiber includes a coreless fiber fused to an emitting end face of the fiber optical fiber and a coating material disposed around at least the coreless fiber, a refractive index of the coating material being higher than a refractive index of the coreless fiber.

Abstract: An optical component or optical low-pass filter has two or more regions demarcated by differences in refractive indexes, in which a region having a refractive index different from the refractive index of the continuous region with the largest volume among the two or more regions is formed in the interior of a transparent material. This optical component or optical low-pass filter has regions with different refractive indexes formed in the interior by pulsed laser irradiation or focused irradiation of the transparent material.

Abstract: A graded-index multimode fiber includes a core made of silica glass, the core having a central region and an outer peripheral region, and a cladding which is provided at an outer periphery of the core. The central region contains one of germanium and phosphorus, and the outer peripheral region contains fluorine.

Abstract: A spectrophotometer capable of high spectral resolution (e.g., in the GHz range) is presented. The spectrophotometer includes a container for holding a sample, an arrayed-waveguide grating coupled to the sample holder, and a detector array coupled to the arrayed-waveguide grating. The arrayed-waveguide grating may be a monolithic chip, and the container may be integrated into the chip. An integrated container may be a microfluidic channel formed through the layers in the chip and positioned in such a way that light is transferable from the microfluidic channel to the waveguides of the arrayed-waveguide grating. The invention is also a method of making the spectrophotometer. The method entails providing an arrayed-waveguide grating having an input end and an output end, coupling a container to the input end, wherein the container is capable of holding a sample, and coupling a detector array to the output end of the arrayed-waveguide grating.

Abstract: A method and apparatus is described that use an index-of-refraction profile having a significant central dip in refractive index (or another tailored index profile) within the core of a gain fiber or a gain waveguide on a substrate. The benefits of this central dip (more power with a given mode structure) are apparent when an input beam is akin to that of a Gaussian mode. In some embodiments, the invention provides a fiber or a substrate waveguide having an index profile with a central dip, but wherein the device has no doping. Some embodiments use a central dip surrounded by a higher-index ring in the index of refraction of the core of the fiber, while other embodiments use a trench between an intermediate-index central core portion and the ring, or use a plurality of rings and/or trenches. Some embodiments use an absorber in at least one core ring.

Abstract: Bend resistant multimode optical fibers are disclosed herein. Multimode optical fibers disclosed herein comprise a core region and a cladding region surrounding and directly adjacent to the core region, the cladding region comprising a depressed-index annular portion comprising a depressed relative refractive index.

Abstract: An optical fibre for propagating a signal in different modes, including a longitudinal length “a” of a change in the tension buildup in the optical fibre and a longitudinal distance “L” between two such changes are in accordance with the equation, a<=0.5 L, for at least part of the optical fibre.