Abstract: Disclosed are methods of providing a hermetically sealed optical connection between an optical fiber and an optical element of a chip and a photonic-integrated chip manufactured using such methods.

Abstract: A co-doped optical fiber is provided having an attenuation of less than about 0.17 dB/km at a wavelength of 1550 nm. The fiber includes a core region in the fiber having a graded refractive index profile with an alpha of greater than 5. The fiber also includes a first cladding region in the fiber that surrounds the core region. Further, the core region has an relative refractive index of about ?0.10% to about +0.05% compared to pure silica. In addition, the core region includes silica that is co-doped with chlorine at about 1.2% or greater by weight and fluorine between about 0.1% and about 1% by weight.

Abstract: A high-refractive-index single-compensation-scattering-cylinder right-angle waveguide of a cylindrical square lattice photonic crystal, being a photonic crystal formed by arranging a first dielectric cylinder having a high refractive index in a background dielectric having a low refractive index in a square lattice; one row and one column of the first dielectric cylinders having a high refractive index are removed from the photonic crystal to form a right-angle waveguide; a second dielectric cylinder having a high refractive index is arranged at a turn of the right-angle waveguide; and the second dielectric cylinder is a compensation scattering cylinder, and the first dielectric cylinders are high-refractive-index cylinders. The structure has an extremely low reflectivity and an extremely high transmission rate, thus facilitating an integration of a large-scale light path.

Abstract: An optical interface device for optically connecting photonic devices to optical device along with methods of making. The method includes providing a glass support member that is either monolithic or laminated. A laser beam is used to write cores in the body of the support member. The support member includes a bend section and the cores generally follow the bend section and serve to define curved optical waveguides. The cores provide strong out-of-plane optical confinement, thereby allowing for strong bends and therefore a compact design for the optical interface device.

Abstract: A single mode optical fiber having a core made from silica and less than or equal to about 11 weight % germania and having a maximum relative refractive index ?1MAX. The optical fiber also has an inner cladding surrounding the core and having a minimum relative refractive index ?2MIN, a first outer cladding surrounding the inner cladding and a second outer cladding surrounding the first outer cladding. The viscosity at 1650° C. of the second outer cladding minus the viscosity at 1650° C. of the first outer cladding is greater than 0.1e7 Poise, and ?1MAX>?2MIN. The single mode optical fiber may also have an outer cladding surrounding the inner cladding made from silica or SiON. The first outer cladding has a maximum relative refractive index ?3MAX, and ?3MAX>?2MIN.

Abstract: A system and method to form beam tunnels in interaction circuits. Forms, such as fibers or sheets can be located and secured above a substrate at a desired size and desired shape to form the final shape of the beam tunnels. Fiber holders can be utilized to position the forms above the substrate. A photoresist can then be applied over the substrate embedding the forms. A single exposure LIGA process can be performed on the photoresist, including the steps of ultraviolet photolithography, molding, and electroforming. After the process, the forms can be removed to leave the beam tunnels in the interaction circuits.

Abstract: A method is provided that includes: forming a low-index trench region with a first density; forming an inner barrier layer comprising silica around the trench region at a second density greater than the first density; depositing silica-based soot around the first barrier layer to form an overclad region at a third density less than the second density; inserting a core cane into a trench-overclad structure; forming an outer barrier layer comprising silica in an outer portion of the overclad region at a fourth density greater than the third density; flowing a down dopant-containing gas through the trench-overclad structure to dope the trench region with the down dopant, and wherein the barrier layers mitigate diffusion of the down-dopant into the overclad region; and consolidating the trench-overclad and the core cane.

Abstract: A single mode optical fiber having a core made from silica and less than or equal to about 11 weight % germania and having a maximum relative refractive index ?1MAX. The optical fiber also has an inner cladding surrounding the core and having a minimum relative refractive index ?2MIN, a first outer cladding surrounding the inner cladding and a second outer cladding surrounding the first outer cladding. The viscosity at 1650° C. of the second outer cladding minus the viscosity at 1650° C. of the first outer cladding is greater than 0.1e7 Poise, and ?1MAX>?2MIN. The single mode optical fiber may also have an outer cladding surrounding the inner cladding made from silica or SiON. The first outer cladding has a maximum relative refractive index ?3MAX, and ?3MAX>?2MIN.

Abstract: A fiber temperature control assembly comprising a spool holding element adapted to hold a fiber spool and a compression element adapted to press fiber windings of a doped optical fiber wound around the fiber spool against said spool holding element being in thermal contact with a heating and/or cooling element of said fiber temperature control assembly.

Abstract: An optical fiber includes a core and a cladding. The optical fiber includes a core material and a cladding material, respectively, wherein the fiber is a non-linear microstructured optical fiber, the microstructured optical fiber being obtainable by a method including loading with hydrogen and/or deuterium and optionally annealing and/or irradiation whereby the lifetime of the fiber may be extended in high power applications.

Abstract: An optical fiber light-guide device for a backlight module includes an optical fiber. The optical fiber includes a core and a cladding layer surrounding the core. The optical fiber defines an inclined groove through an outer surface of the cladding layer, the inclined groove has at least one first end and a second end located along a length of the optical fiber, a depth of the groove gradually increases from each first end to the second end.

Abstract: A few-mode fiber is described, having a graded-index core and a surrounding cladding comprising a ledge between the core and the trench, a down-doped trench abutting the ledge, and an undoped cladding region abutting the trench. The fiber's refractive index profile is configured to support 9 or more LP modes for transmission of a spatially-multiplexed optical signal. Undesired modes have respective effective indices that are close to, or less than, the cladding index so as to result in leakage of the undesired modes into the outer cladding. The index spacing between the desired mode having the lowest effective index and the leaky mode with the highest effective index is sufficiently large so as to substantially prevent coupling therebetween.

Abstract: A treated monomer for optical fiber coatings, a coating composition containing the treated monomer, a coating formed from a coating composition containing a treated monomer, and a fiber coated with the coating formed from a coating composition containing a treated monomer. The monomer is an alkoxylated alkyl acrylate and is formed by acrylating a polyol precursor. The monomer may include residual unreacted polyol precursor. The monomer is treated with a derivatizing agent to convert residual unreacted polyol to a derivative form. The derivative form is less susceptible to degradation to the corresponding non-alkoxylated alcohol or other lower alkoxylated alcohol. The treated monomer includes the alkoxylated alkyl acrylate and the derivative form of the polyol.

Abstract: Described is a technique for the design and manufacture of MMFs. Designs are implemented so as to limit the maximum variation in z(r, ?) with respect to wavelength, where z(r, ?) is the dielectric constant weighted by the square of the wavelength. MMFs for use in CWDM applications are specifically described.

Abstract: An optical element devices and method are described herein. An example optical device may include an optical element. The optical element may have an optical path material to allow a light to pass therethrough. The optical path material may have a first end portion with a first end surface, a second end portion with a second end surface, and a middle portion between the first and second end portions with an interior and an exterior surface. A coating may be disposed along the exterior surface and diffused into the optical path material. The coating may minimize leakage of the light from the interior through the exterior surface.

Abstract: An optical fiber for amplification includes a core having an inner core and an outer core surrounding the outer circumferential surface of the inner core. The relative refractive index difference of the inner core to a cladding is smaller than the relative refractive index difference of the outer core to the cladding. The outer core is entirely doped with erbium. The theoretical cutoff wavelength of an LP11 mode light beam is a wavelength of 1,565 nm or more. The theoretical cutoff wavelength of an LP21 mode light beam is a wavelength of 1,530 nm or less. The theoretical cutoff wavelength of the LP02 mode light beam is a wavelength of 980 nm or less.

Abstract: The present disclosure discloses a fiber laser, including a laser seed source, an amplifying optical path, an output optical isolator and an optical fiber cylinder; wherein, the amplifying optical path is connected to the laser seed source and the output optical isolator, the laser seed source is used to output optical source, the amplifying optical path includes a first stage amplifying optical path and a second stage amplifying optical path, the first stage amplifying optical path is connected to the laser seed source and the second stage amplifying optical path respectively, the output optical source is output via the output optical isolator after two-stage amplifying; the second stage amplifying optical path comprises a multi-mode active optical fiber; the multi-mode active optical fiber is coiled on the optical fiber cylinder. By the disposing way above, the present disclosure may improve output optical beam quality of the fiber laser.

Abstract: A hollow core fiber has a cladding comprising a matrix of cells, wherein each cell comprises a hole and a wall surrounding the hole. The fiber further has a hollow core region comprising a core gap in the matrix of cells, wherein the core gap spans a plurality of cells and has a boundary defined by the interface of the core gap. The matrix of cells comprises a plurality of lattice cells, and a plurality of defect cells characterized by at least one difference in at least one property from that of the lattice cells. The cells at the core region boundary include lattice cells and defect cells that are arranged in a pattern that define two orthogonal axes of reflection symmetry, so as to produce birefringence in a light propagating through the hollow core fiber.

Abstract: Side light LED troffer tube. In an aspect, a side light LED tube is provided that includes a tube having at least one light receiving portion configured to receive light and gradient optics formed on the tube. The gradient optics providing a transparency gradient configured to distribute the light to achieve a selected emitted light intensity variation across a selected surface of the tube.

Abstract: The present disclosure is directed to a method of making an optical fiber with improved bend performance, the optical fiber having a core and at least one cladding layer, and a chlorine content in the in the last layer of the at least one cladding layer that is greater than 500 ppm by weight. The fiber is prepared using a mixture of a carrier gas, a gaseous chlorine source material and a gaseous reducing agent during the sintering of the last or outermost layer of the at least one cladding layer. The inclusion of the reducing gas into a mixture of the carrier gas and gaseous chlorine material reduces oxygen-rich defects that results in at least a 20% reduction in TTP during hydrogen aging testing.

Abstract: Embodiments are generally directed to autostereoscopic display device illumination apparatuses having one or more optical fibers (i.e., flexible light diffusing waveguides) as linear emitters for illuminating columns of pixels of a display panel within the autostereoscopic display device. In some embodiments, the linear emitters are defined by a single optical fiber that is arranged on a substrate in a serpentine manner to form an array of linear emitters. In some embodiments, the linear emitters are defined by several optical fibers. Illumination apparatuses of some embodiments may also include a prism device configured to create multiple images of the optical fiber(s).

Abstract: An optical fiber cable has a sectional area of Ac [mm2] and housing a number N of optical fibers. A transmission loss ?dB [dB/km], a mode field diameter W [?m], an effective area Aeff [?m2], an effective length Leff [km], and a wavelength dispersion D [ps/nm/km] of each of the optical fibers at a wavelength of 1550 nm satisfy a predetermined equation and the transmission loss of the optical fiber at the wavelength of 1550 nm is 0.19 dB/km or less, and the effective area of the optical fiber is in a range from 125 to 155 ?m2.

Abstract: The embodiments described herein relate to multi-core optical fiber interconnects which include at least two multi-core optical fibers. The multi-core optical fibers are connected such that the core elements of the first multi-core optical fiber are optically coupled to the core elements of the second multi-core optical fiber thereby forming an array of interconnect core elements extending through the optical fiber interconnect. The multi-core optical fibers are constructed such that cross-talk between adjacent core elements in each multi-core optical fiber is minimized. The multi-core optical fibers are also constructed such that time-delays between the interconnect core elements in the array of interconnect core elements are also minimized.

Abstract: An illuminated suction apparatus including a hand-held surgical device combining a high-performance illumination waveguide with suction. This device would be useful in a wide array of various surgical procedures including open and minimally invasive orthopedics.

Abstract: Embodiments of optical fiber may include cladding features that include a material (e.g., fluorine-doped silica glass) that may produce a very low relative refractive index difference with respect to cladding material in which the cladding features are disposed. This relative refractive index difference may be characterized by (n1-n2)/n1, where n1 is the index of refraction of the cladding material in which the cladding features are included, and n2 is the index of refraction of the cladding features. In certain embodiments, the relative refractive index difference may be less than about 4.5×10?3. In various embodiments, the configuration of the cladding features including, for example, the size and spacing of the cladding features, can be selected to provide for confinement of the fundamental mode yet leakage for the second mode and higher modes, which may provide mode filtering, single mode propagation, and/or low bend loss.

Abstract: An optical device includes a silicon waveguide core having a tapered portion having a sectional size that decreases toward a terminal end portion thereof, a dielectric waveguide core contiguous to the silicon waveguide core while covering at least the tapered portion, the dielectric waveguide core having a refractive index lower than that of the silicon waveguide core and configuring a single-mode waveguide, and a diffraction grating provided at the single-mode waveguide and configuring a distributed Bragg reflection mirror.

Abstract: A multimode optical fiber may include a core portion formed from SiO2 intentionally doped with a single dopant, wherein the single dopant is phosphorous or a compound of phosphorous. A glass cladding portion may surround and be in direct contact with the core portion. The glass cladding portion may comprise an outer cladding portion and a low-index moat disposed between the core portion and the outer cladding portion. The optical fiber may also have a bandwidth greater than or equal to 2000 MHz-km for each wavelength within a wavelength operating window centered on a wavelength within an operating wavelength range from about 850 nm to about 1310 nm, the wavelength operating window having a width greater than 100 nm. The optical fiber may also have a restricted launch bend loss less than or equal to 0.5 dB/(2 turns around a 15 mm diameter mandrel) at 850 nm.

Abstract: The optical fiber includes a core, the first cladding, and second cladding. The core is made of silica based glass containing Cl. The first cladding and the second cladding are made of silica based glass containing fluorine. The refractive index of the first cladding is lower than that of the core. The refractive index of the second cladding is lower than that of the core and higher than that of the first cladding. The second cladding is divided into an outer region having a uniform refractive index and an inner region having a refractive index higher than that of the outer region. The difference ?P between the maximum refractive index of the inner region and the refractive index of the outer region is 0.02% to 0.10% in terms of relative refractive index with respect to pure silica based glass. The radial thickness R of the inner region is 10 ?m to 25 ?m.

Abstract: An embodiment of the present invention relates to an MMF with a structure for reducing length dependence of optical characteristics while maintaining bend-insensitivity. The MMF has a trench portion provided between a core portion and a cladding portion and having a refractive index lower than that of the cladding portion. In a cross section of the MMF, the trench portion in at least a partial section of the MMF has a non-circularly symmetric shape with respect to an intersection between the optical axis and the cross section.

Abstract: Provided is a polyorganosiloxane having a platinum content of 1 ppm by mass or less.

Abstract: Apparatus and method for amplifying laser signals using segments of fibers of differing core diameters and/or differing cladding diameters to suppress amplified spontaneous emission and non-linear effects such as four-wave mixing (FWM), self-phase modulation, and stimulated Brillouin and/or Raman scattering (SBS/SRS). In some embodiments, different core sizes have different sideband spacings (spacing between the desired signal and wavelength-shifted lobes). Changing core sizes and providing phase mismatches prevent buildup of non-linear effects. Some embodiments further include a bandpass filter to remove signal other than the desired signal wavelength and/or a time gate to remove signal at times other than during the desired signal pulse. Some embodiments include photonic-crystal cores for the signal and/or photonic-crystal inner cladding for the pump and/or use reflector connector segments.

Abstract: A downhole property measurement apparatus includes an optical fiber having a series fiber Bragg gratings with interleaved resonant wavelengths such that adjacent fiber Bragg gratings have different resonant wavelengths and a difference between adjacent resonant wavelengths is greater than a dynamic wavelength range of each of the adjacent fiber Bragg gratings. An optical interrogator is in optical communication with the optical fiber and configured to emit a frequency domain light signal having a swept wavelength for a first time duration and a chirp having a modulation of amplitude with a varying of wavelength for a second time duration that is less than the first time duration. A return light signal is transformed by the optical interrogator into a time domain to determine a resonant wavelength shift and corresponding location of each of the gratings. A processor converts the resonant wavelength shifts into the downhole property.

Abstract: A light-reflective anisotropic conductive adhesive used for anisotropic conductive connection of a light-emitting element to a wiring board includes a thermosetting resin composition, conductive particles, and light-reflective insulating particles. The light-reflective insulating particles are at least one of inorganic particles selected from the group consisting of titanium oxide, boron nitride, zinc oxide, and aluminum oxide, or resin-coated metal particles formed by coating the surface of scale-like or spherical metal particles with an insulating resin.

Abstract: A multicore fiber according to the present invention includes a plurality of cores and a cladding enclosing the plurality of the cores. The plurality of the cores has two cores or greater forming a first plurality of cores linearly arranged to form a first row on one side based on a plane passed through the center axis of the cladding and three cores or greater forming a second plurality of cores arranged in parallel with the first plurality of the cores to form a second row on the other side based on the plane. The cores configuring the first plurality of the cores and the cores configuring the second plurality of the cores are disposed on lines orthogonal to the plane.

Abstract: An optical element device and method of fabrication thereof are described herein. An example optical device may include an optical element (100). The optical element (100) may have an optical path material (105) to allow a light to pass therethrough. The optical path material (105) may have a first end portion (110) with a first end surface (112), a second end portion (110) with a second end surface (112), and a middle portion (115) between the first and second end portions (110) with an interior (116) and an exterior surface (117). A coating (120) may be disposed along the exterior surface (117) and diffused into the optical path material (105). The coating (120) may minimize leakage of the light from the interior (116) through the exterior (117) surface.

Abstract: One embodiment of the disclosure relates to a system comprising: (i) at least light source transmitting at a bit rate of 10 Gb/s or higher at one or more wavelengths between 840 and 860 nm; (ii) at least one few moded optical fiber optically coupled to said light source, said fiber comprises a graded index a graded index glass core having a diameter D1, such that 12.5 microns?D1<40 microns, a maximum relative refractive index between 0.265 and 0.65 percent, the glass core diameter D1 and refractive index are selected such that the core is capable of supporting the propagation and transmission of an optical signal with X number of mode groups at a wavelength of 850 nm, wherein X is an integer greater than 1 and less than 8, and a cladding comprising a depressed index region and an outer cladding region, wherein said fiber has an overfilled bandwidth at an operating wavelength situated in 840 nm to 860 nm wavelength range greater than 4 GHz-km; an alpha being 2.05???2.15; and an attenuation less than 2.

Abstract: A light guide sensor includes a light source, a light guide member comprising a core which guides light radiated from the light source, a cladding formed around the core, and at least one detecting portion is formed, and a light receiving unit which receives the light that has been guided by the member and has passed via the detecting portion. The detecting portion includes a first opening formed by removal in the outer circumference of the member so that at least part of the cladding is left by a thickness such as not to transmit the light from the core, and a second opening formed within the range of the first opening to transmit the light from the core. A method of forming such a light guide sensor is provided.

Abstract: One embodiment of the disclosure relates to a few moded optical fiber comprises: a glass graded index core having alpha profile such that 2.0???2.15, a diameter D1 in the range of 13 microns to 40 microns, a maximum relative refractive index between 0.265 and 0.65 percent, core being structured to propagate more with X number of mode groups at a wavelength of 850 nm, wherein X is an integer greater than 1 and less than 8; and (b) a cladding including a depressed-index annular region surrounding the inner cladding. The fiber has an overfilled bandwidth greater than 2.0 GHz-km at 850 nm and relative microbending sensitivity ? such that ??1.5.

Abstract: An optical fiber containing an alkali metal element and exhibiting low attenuation as well as excellent radiation resistance is provided. The optical fiber of the present invention has a core region and a cladding region enclosing the core region. The core region contains alkali metal elements by an average concentration of 0.2 atomic ppm or more. The attenuation at a wavelength of 1550 nm after irradiating with the radiation of 0.10 Gy or more of cumulative absorbed dose increases by 0.02 dB/km or less as compared with the attenuation exhibited prior to radiation exposure.

Abstract: Embodiments of the present invention generally relate to fiber designs for wavelength tunable ultra-short pulse lasers. More specifically, embodiments of the present invention relate to systems incorporating fiber designs for higher order mode fibers capable of soliton self frequency shifting where a system comprises a first fiber for shifting the wavelength from a pump wavelength to a transfer wavelength and a second fiber for shifting the pulse from the transfer wavelength to an output wavelength. In one embodiment of the present invention, a wavelength tunable short pulse fiber laser system comprises: a pulse generator for providing a pulse having an input wavelength; a mode-converter; a first designed fiber for shifting the pulse from the input wavelength to a transfer wavelength; and a second designed fiber for shifting the pulse from the transfer wavelength to an output wavelength.

Abstract: A device for converting transverse spatial profile of intensity of a light beam, using a microstructured optical fiber. Transverse dimensions of the fiber vary longitudinally and both its ends have opto-geometrical parameters such that at the wavelength of the beam the fiber has a fundamental mode having two different profile shapes at its two ends. Thus by introducing the beam with one of the profiles through one of the two ends, the beam emerges through the other end with the other profile, whose shape is different from that of the profile of the introduced beam.

Abstract: A method for realizing an optical waveguide in a substrate by means of a femtosecond laser system, the waveguide including a birefringence axis tilted by a predetermined angle for at least a segment, is disclosed. The method includes preparing a substrate including a free surface, focusing a femtosecond laser beam into the substrate, in order to induce a refractive index modification of a volume of such substrate around the focal region. The method further includes varying a propagation direction of the femtosecond laser beam to reach a propagation direction describing a predetermined non-vanishing angle with respect to the normal to the free surface of the substrate, and translating the focal region with respect to the substrate, in order to generate the waveguide segment.

Abstract: The present invention relates to an MCF with a structure for enabling an alignment work with higher accuracy. The MCF has a plurality of cores and a cladding. An outer peripheral shape of the cladding in a cross section of the MCF is comprised of a circumferential portion forming a circumference coincident with an outer periphery of the MCF, and a cut portion. The cut portion has a bottom portion and two contact portions provided on both sides of the bottom portion and projecting more than the bottom portion. When a side face of the MCF is viewed, the two contact portions have flattened faces and the flattened faces of the two contact portions extend along a longitudinal direction of the MCF with the bottom portion in between.

Abstract: A multicore fiber includes a plurality of cores and a cladding surrounding the plurality of cores. The plurality of cores is arranged and disposed on a linear line passed through the center of the cladding. A pair of cores is included. The pair of the cores is located adjacent to each other, and has different core diameters in a first direction in which the plurality of cores is arranged on the linear line. A ratio of a core diameter in the first direction to a core diameter in a second direction orthogonal to the first direction is different between the pair of the cores.

Abstract: A lighting system for a vehicle display includes a light source and a pointer located apart from the light source. The lighting system further includes at least one optical fiber connected between the light source and the pointer.

Abstract: The invention relates to an optical fiber as an optical waveguide for the single-mode operation. The present invention proposes a fiber having a microstructure, by which the propagation of modes of a higher order are selectively suppressed in the optical waveguide. At the same time, the propagation of transversal modes of a higher order is dampened more strongly than the propagation of the fundamental modes of the optical waveguide.

Abstract: The present invention generally relates to the field of fiber optics, and more specifically to optical fibers, methods of manufacturing optical fibers, and methods of classifying optical fibers. In an embodiment, the present invention is a multimode optical fiber which comprises a core and clad material system where the refractive indices of the core and cladding are selected to minimize chromatic dispersion in the 850 nm wavelength window and the refractive index profile is optimized for minimum modal-chromatic dispersion in channels utilizing VCSEL transceivers. Multimode optical fibers according to this embodiment may have increased channel bandwidth.

Abstract: An optical fiber preform which can be drawn into a low attenuation optical fiber is provided with a core portion and a cladding portion surrounding the core portion. The core portion includes a first core portion and a second core portion surrounding the first core portion. The cladding portion includes a first cladding portion surrounding the second core portion and a second cladding portion surrounding the first cladding portion. The first core portion contains an alkali metal element, the concentration of oxygen molecules contained in glass is 30 mol ppb or more and 200 mol ppb or less in a part of or entire region having an alkali metal atom concentration of 100 atomic ppm or more, and the concentration of oxygen molecules contained in glass is 10 mol ppb or less in a region having an alkali metal atom concentration of 50 atomic ppm or less.

Abstract: Techniques and architecture are disclosed for providing a laser system. In one specific example embodiment, the system includes a thulium-doped fiber laser coupled by silica glass fiber to a remote optical converter (ROC) including a Ho:YAG laser and, optionally, an optical parametric oscillator (OPO) utilizing in germanium phosphide (ZnGeP2; ZGP) or orientation-patterned gallium arsenide (OPGaAs). The fiber laser may emit a low-peak-power, continuous wave pump signal that pumps the Ho:YAG laser, which in turn emits a higher-peak-power, pulsed signal. When included, the OPO can be used to convert the resultant, pulsed signal to a longer wavelength (e.g., about 2-5 ?m, or greater). In some cases, distributed architecture and reduced weight/bulk may be realized while eliminating the need to actively cool the ROC for operation, for example, over a broad temperature range (e.g., ?55-125° C.). Also, methods of preparing high-peak-power, pulsed signals using such systems are disclosed.

Abstract: An optical fiber cable includes a tubular sheath and a plurality of optical fibers disposed in the space of the sheath as the optical fibers are bent. In the plurality of optical fibers, at least one optical fiber is a multicore fiber. The multicore fiber satisfies an expression RPk<RLo, or RHi<RPk, where a bending radius at which the crosstalk of the multicore fiber becomes the worst is defined as RPk, a bending radius of the multicore fiber at a lowest temperature in operating temperature limits is defined as RLo, and a bending radius of the multicore fiber at a highest temperature in the operating temperature limits is defined as RHi.