Abstract: An objective of the present invention is to provide a mode conversion device capable of designing any coupling efficiency and full width at half maximum, and a design method therefor. According to the present invention, a mode conversion device includes a long period grating at a core of an optical fiber through which light is able to propagate in at least two propagation modes. The long period grating satisfies a relationship of Expression C1, where a full width at half maximum FWHM is a wavelength band in which the coupling efficiency is a half of coupling efficiency of mode conversion at a center wavelength, C is coupling efficiency, Lc is a complete coupling length, Lg is a grating length, ? is a grating pitch, and ?? is a propagation constant difference between the two propagation modes at the center wavelength of a mode conversion target. [ Math .

Abstract: It is an object of the present invention to provide a multicore optical fiber, a design method for the multicore optical fiber and an optical transmission method using the multicore optical fiber including four cores having a standard cladding diameter of 125±1 ?m for an existing single mode optical fiber covering several thousands of kilometers of transmission. The multicore optical fiber according to the present invention disposes two-stage claddings with different refractive indices around each core, and designates as a predetermined range, a core radius a1, a radius a2 of a first cladding region surrounding each core, specific refractive index ?1 relative to the core of the first cladding region and a specific refractive index ?2 relative to the core of a second cladding region including four cores and the first cladding region.

Abstract: An object of the present invention is to provide an optical transmission system capable of controlling a transmission capacity and a signal processing load of a MIMO equalizer, without depending on the number of propagation modes of the optical fiber.

Abstract: An object of the present invention is to provide an evaluation method and an evaluation device for easily determining whether or not a structural parameter of a multi-core fiber satisfies a desired connection loss value (a specification). The evaluation method according to the present invention includes a step of measuring center coordinates of each core with the center coordinates when a clad is approximated by a circle as an origin in an observed cross-sectional structure of the multi-core fiber to be objected, obtaining a length of a line segment connecting the origin and the center of each core and an angle formed by two line segments connecting the origin and two adjacent cores, and judging whether or not a desired connection loss characteristic is satisfied on the basis of whether or not the values satisfy a predetermined determination formula.

Abstract: In a mask pattern forming method, a resist film is formed over a thin film, the resist film is processed into resist patterns having a predetermined pitch by photolithography, slimming of the resist patterns is performed, and an oxide film is formed on the thin film and the resist patterns after an end of the slimming step in a film deposition apparatus by supplying a source gas and an oxygen radical or an oxygen-containing gas. In the mask pattern forming method, the slimming and the oxide film forming are continuously performed in the film deposition apparatus.

Abstract: The purpose of the present invention is to provide an optical fiber amplifier capable of seamlessly and collectively amplifying optical signals in a plurality of bands. In order to achieve the aforementioned purpose, the optical fiber amplifier according to the present invention is the optical fiber amplifier that amplifies multiple wavelength bands, and in cross-section, one signal light primary propagation region, and a doped region where rare-earth ions have been added, wherein the doped region includes the rare-earth-doped optical fiber existing other than the propagation region.

Abstract: An object of the present invention is to achieve a low delay core applicable to a Master channel of a Master-Slave CPE (MS-CPE) transmission method with a general-purpose refractive index distribution structure. An optical fiber according to the present invention is a single-mode optical fiber, and has an SI-type refractive index distribution structure, in which a clad region relative refractive index difference ? (%) with respect to a core region refractive index, a radius a (?m) of the core region, and a group delay time difference ?? between the Master channel and the Slave channel satisfy “Mathematical Expression 19” and “Mathematical Expression 20”, or has a W-type refractive index distribution structure, in which a mode field diameter MFD is 9.5 to 10.

Abstract: An object of the present invention is to provide a core position recognition method, a connection method, and a connection apparatus that can simplify connection operations, and reduce rotational displacement and positional displacement. The connection apparatus according to the present invention includes a function capable of acquiring the rotation amount of an MCF during the bonding/fixing step. Specifically, the connection apparatus of the present invention uses an MCF with lines drawn on a side surface thereof, thereby recognizing the rotation amount of the MCF from the side surface, and calculating the absolute positions of the cores. The connection apparatus according to the present invention can recognize the absolute position s of the cores from a side image of an MCF in a state in which the MCF has been rotated.

Abstract: It is an object of the present invention to provide a multicore optical fiber, a design method for the multicore optical fiber and an optical transmission method using the multicore optical fiber including four cores having a standard cladding diameter of 125±1 ?m for an existing single mode optical fiber covering several thousands of kilometers of transmission. The multicore optical fiber according to the present invention disposes two-stage claddings with different refractive indices around each core, and designates as a predetermined range, a core radius a1, a radius a2 of a first cladding region surrounding each core, specific refractive index ?1 relative to the core of the first cladding region and a specific refractive index ?2 relative to the core of a second cladding region including four cores and the first cladding region.

Abstract: There are provided a multi-core optical fiber including four step-index type cores with a standard cladding diameter and having excellent mass productivity, quality, and yield while meeting desired specifications, and a design method thereof. A multi-core optical fiber according to the present disclosure includes: four cores arranged in a square lattice shape along a longitudinal direction, each of the four cores having a step-index type refractive index distribution with a radius a; and a cladding region having a lower refractive index than that of each core and a diameter of 125±1 ?m and provided on an outer peripheral portion of each core, where an absolute value of a relative refractive index difference between each core and the cladding region is ?.

Abstract: An object of the present disclosure is to enable behavior of a linear structure in water to be estimated. The present disclosure is an apparatus that: expresses at least one parameter in a plurality of discrete values, and forecasts behavior of a linear structure by using each of the discrete values; acquires behavior of the linear structure detected using an optical fiber; calculates a likelihood between the forecasted behavior of the linear structure and the acquired behavior of the linear structure; updates at least one of the plurality of discrete values on the basis of the likelihood; and calculates behavior of the linear structure by using the updated plurality of discrete values.

Abstract: An object of the present invention is to provide an optical transmission system capable of satisfying XT required by a modulation system even if there is an inter-core loss difference in an MCF.

Abstract: An object of the present invention is to provide an HAF having a structure in which the number of air holes is decreased to be smaller than that of a PCF and Rayleigh scattering loss may be more reduced than that in the existing HAF.

Abstract: An object of the present disclosure is to alleviate deterioration of transmission characteristics of a fiber due to transmission of ultraviolet light, and to eliminate complication of operation due to frequent replacement of an optical fiber in which deterioration has occurred. The present disclosure is an ultraviolet light irradiation system including: an optical transmission unit that propagates ultraviolet light using a plurality of optical transmission lines; an ultraviolet light source unit that inputs ultraviolet light to each of the optical transmission lines with arbitrary power; and an irradiation unit that irradiates a target location with the ultraviolet light propagated through the plurality of optical transmission lines.

Abstract: An object is to provide an optical side input/output circuit that has wavelength selectivity and is easily disposed at multiple points in a transmission path, and an optical connector. An optical side input/output circuit 301 according to the present invention includes: a grating portion 20 in which a fiber Bragg grating 21 that reflects light of a desired wavelength is formed in the core 51 of an optical fiber 50, the light of the desired wavelength being of light propagating in the core 51; and a tap portion 10 that is disposed at a stage before the grating portion 20 in the propagation direction of the light, and is provided with a tap waveguide 53 that outputs the light reflected by the grating portion 20 from a side surface of the optical fiber 50.

Abstract: An object of the present invention is to provide an ultraviolet light irradiation system and an ultraviolet light irradiation method which are not limited in an ultraviolet light irradiation region and can be introduced economically. The present ultraviolet light irradiation system is a system configured to connect a single ultraviolet light source part and an irradiation part installed in the vicinity of an object place to be sterilized or the like by the optical cable formed by bundling a plurality of optical fibers (the single-core or the multi-core) or the multi-core optical fiber. Since the optical fiber is very thin and does not require power supply for transmitting the ultraviolet rays, even in a fine place where a person or a robot cannot enter, the ultraviolet light can be irradiated by laying the optical fiber or the optical cable.

Abstract: An objective is to provide an acoustic mode propagation speed measurement method and an acoustic mode propagation speed measurement device capable of measuring a propagation speed of an acoustic mode without cutting or processing an optical fiber wire. According to the present invention, an acoustic mode propagation speed measurement method includes: acquiring a frequency shift spectrum of Brillouin scattered light generated in an optical fiber; fitting the frequency shift spectrum using a Gauss function; acquiring a spectral full-width at half maximum w from a fitted curve using the Gauss function; and calculating a propagation speed VA of an acoustic mode of the optical fiber by substituting the acquired spectral full-width at half maximum w into a linear function of the spectral full-width at half maximum w and the propagation speed VA of the acoustic mode.

Abstract: The present invention aims to provide an optical side input/output circuit that has wavelength selectivity and is easily disposed at multiple points in a transmission path, and an optical connector. The optical side input/output circuit 301 includes: a tap portion 10 in which a tap waveguide 53 that outputs light of a higher-order mode from a side surface of an optical fiber 50 is formed, the light of the higher-order mode being of light propagating in the core 51 of the optical fiber 50; and a grating portion 20 that is located in a stage before the tap portion 10 in the propagation direction of the light, and has a grating 21 that converts light of a desired wavelength from a basic mode to the higher-order mode, the grating 21 being formed in the core 51 of the optical fiber 50.

Abstract: The present invention is to provide a multi-core optical fiber that can expand its transmission wavelength band, and extend its transmission distance by reducing crosstalk, and also provide a method for designing the multi-core optical fiber. A multi-core optical fiber according to the present invention includes: four cores that are arranged in a square lattice pattern in a longitudinal direction; and a cladding region that is formed around the outer peripheral portions of the cores and has a lower refractive index than the cores, the absolute value of the relative refractive index difference between the cores and the cladding region being represented by ?. In the multi-core optical fiber, the diameter of the cladding region is 125 ± 1 µm, the cutoff wavelength is 1.45 µm or shorter, the mode field diameter MFD at a wavelength of 1.55 µm is 9.5 to 10.0 µm, the bending loss at a wavelength of 1.625 µm and with a bending radius of 30 mm is 0.

Abstract: It is an object of the present disclosure to reduce the risk of information exploitation by a malicious third party while allowing communication data to be demodulated in real time.