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: 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 objective of the present invention is to provide an amplification fiber having a cladding excitation configuration that improves amplification efficiency and an optical amplifier. An amplification fiber (10) according to the present invention is a multi-core amplification fiber having, from one end (E1) to the other end (EE), a plurality of cores (11b) in a cladding (11a), and a total distance from the one end (E1) to the other end (EE) in which rare earth ions are doped differs depending on the types of cores (11b). The cores (11b) are preferably disposed such that the cores of the same type are not adjacent to each other. By arranging the types of the cores in this manner, requirements for inter-core crosstalk can be mitigated since the bands of signal light in the adjacent cores are different. As a result, a density of cladding excitation light can be increased by shortening the inter-core distance, and thus the amplification efficiency can be improved.

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 is to provide an optical amplifier with a cladding pumped configuration that improves amplification efficiency. The optical amplifier according to the present invention includes a pump light conversion fiber 11 that converts first pump light L1 with a first wavelength propagating in a cladding into second pump light L2 with a second wavelength, an amplification fiber 13 that is connected to the pump light conversion fiber 11 and optically amplifies signal light Ls with the second pump light L2 supplied to the cladding from the pump light conversion fiber 11, and an oscillator 12 that causes the second pump light L2 to be reflected on two reflectors 15 and to reciprocate within the claddings of the pump light conversion fiber 11 and the amplification fiber 13 to cause laser oscillation of the second pump light L2.

Abstract: An objective is to provide an optical amplifier having a core excitation configuration that improves amplification efficiency. An optical amplifier according to the present invention includes an excitation light conversion fiber 11 that absorbs first excitation light L1 propagating in a cladding and having a first wavelength and emits, into a core, spontaneous emission light having a second wavelength, an oscillator 12 for causing the spontaneous emission light to be reflected on two reflectors 15 to reciprocate the light within the core of the excitation light conversion fiber 11 and laser-oscillating second excitation light L2 having the second wavelength, and an amplification fiber 13 that is connected to the excitation light conversion fiber 11 and amplifies signal light with the second excitation light L2 supplied from the excitation light conversion fiber 11 to the core.

Abstract: An objective of the present invention is to provide an optical amplifier having a cladding excitation configuration that improves amplification efficiency.

Abstract: An object is to provide an optical fiber connector ferrule, a sleeve, and a method for manufacturing a ferrule member that can avoid an increase in manufacturing time and an increase in cost of optical connectors for connecting multicore optical fibers. The present invention provides an optical fiber connector ferrule, a sleeve, and a method for manufacturing ferrule member which realizes alignment of multicore optical fibers corresponding to the connection by mounting a ferrule on a multicore fiber and then cutting a ferrule member instead of aligning core positions by rotating an axis of an optical fiber and adjusting positions of cores to the ferrule, leading to simplification of a rotational alignment step.

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: A planar waveguide having M×N number of cores and to which M number of fibers having N number of cores are connected. In the planar waveguide, in a connecting end surface of the planar waveguide to which the fibers are connected, P number of fibers having Q number of cores are connected, M×N is equal to P×Q, the planar waveguide includes a plurality of the cores arranged in a horizontal direction at the same height position in the planar waveguide, and a laminated structure having the cores at different positions in a height direction, so as to be aligned with the cores of the fibers connected to the connecting end surface, and the positions of the M×N number of cores are constant in the height direction, and change only in the horizontal direction.

Abstract: An object of the present invention is to provide an optical transmission system capable of easily controlling a transmission capacity and an optical signal quality even if a MIMO equalizer is provided. The optical transmission system according to the present invention is provided with an N×M MIMO equalizer, includes receivers (N units) equal in number to the spatial multiplexing order L of an optical fiber, and changes the number M of the signal beams of light transmitted through the optical fiber in the range of the spatial multiplex order L or less. The adjustment of the number M of signal beams of light makes it possible to adjust a transmission capacity and a signal quality of the optical transmission system even after construction of the transmission line.

Abstract: An objective of the present invention is to provide an optical communication system and an optical communication method that can reduce even a delay generated in processing of obtaining a transfer function for correcting distortion in digital coherent transmission. In the optical communication system according to the present invention, pilot data for estimating a transfer function for a transmission channel is transmitted through a transmission channel with a short transmission delay time, a transfer function of the transmission channel is estimated before receiving transmission data, and the transfer function is applied to other transmission channels.

Abstract: An object of the present invention is to provide a multi-core optical fiber that can prevent an increase in bending loss even when a distance between a peripheral core and a cladding boundary is decreased, and can improve a bending loss characteristic in a state where an influence on a cutoff wavelength and a mode field diameter is small, and a design method thereof.

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: 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: An object is to provide a multi-core configuration for acquiring a random mode coupling in a case of an arbitrary core refractive index. A multi-core optical fiber according to the present invention is an optical fiber in which two or more core regions are arranged in a clad region having a refractive index at a minimum core interval ? smaller than a refractive index of the cores, a configuration of the cores is that including one propagation mode, and the core configuration and the core interval are adjusted so that an inter-mode coupling coefficient between adjacent cores is within a range from 0.73 to 120 m?1.

Abstract: An optical fiber includes a core, a first clad that is provided on an outer circumferential portion of the core and has a refractive index lower than that of the core, and a second clad that is provided on an outer circumferential portion of the first clad and has a refractive index lower than that of the first clad. In the optical fiber, a mode field diameter at a wavelength of 1.55 ?m is equal to or greater than 11.5 ?m, a cutoff wavelength is equal to or less than 1.53 ?m, a bending loss at a bending radius of 30 mm and a wavelength of 1.625 ?m is equal to or less than 2.0 dB/100 turns, and a delay time of transmission light per unit length at a wavelength of 1.55 ?m is equal to or less than 4.876 ?s/km.

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: 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 optical fiber manufacturing method includes setting a first holding member and a rod inside a glass pipe, the first holding member made of glass and having plural holes formed, so that the rod is supported by the first holding member; filling glass particles between the rod and a glass pipe inner wall; holding the rod such that the rod and the filled glass particles are enclosed by the glass pipe inner wall and the first and second holding members, and sealing one end of the glass pipe and manufacturing an intermediate; and manufacturing an optical fiber from the intermediate, wherein a bulk density of the first and second holding members is set with reference to a bulk density of a filling portion made from the glass particles, and the predetermined range is determined according to a core diameter permissible variation range in its longitudinal direction.