Abstract: An object of the present invention is to provide an ultraviolet light irradiation system and an ultraviolet light irradiation method which can perceive a state of a region where ultraviolet light is irradiated to output/block the ultraviolet light. An ultraviolet light irradiation system 301 according to the present invention includes an ultraviolet light source unit 11 that produces ultraviolet light, an N (N is a natural number) irradiation unit 13 that irradiates an irradiation target region Ar with the ultraviolet light, a sensor unit 31 that detects whether or not an object that should avoid exposure is present in the irradiation target region Ar, and a blocking unit 30 that stops, in a case where the object that should avoid exposure is present in the irradiation target region Ar, irradiation of the ultraviolet light from the irradiation unit 13 to the irradiation target region Ar.

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 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: 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: The present invention not only forms an electric field environment that can be controlled to differentiate between preservation of food freshness and promotion of ripening but also promotes fermentation by fermentative microbes, propagates plankton and inhibits bacterial reproduction. An electrode plate 2 is set inside a refrigerator 1 or an adjustable temperature box 6. Food 3 or a yogurt container 9 is place thereon. The electrode plate 2, 10 is connected to a power source 4, 11. Selection between food freshness preservation and promotion of ripening, and promotion of fermentation of fermented foods such as yogurt are performed by rectification, and voltage and frequency control of the power source. Additionally, propagation of phytoplankton and inhibition of bacterial reproduction are performed by controlling the frequency, voltage and ON/OFF timing of the power source.