Nippon Telegraph and Telephone Corporation

The Furukawa Electric Co., Ltd.

Fujikura Limited

The University of Tokyo

Kazuhide Nakajima

Takashi Matsui

Taiji Sakamoto

Masaki Wada

Yuto Sagae

Takashi Yamamoto

Kyozo Tsujikawa

Toshio Kurashima

Shinichi Aozasa

Nobutomo Hanzawa

Takayoshi Mori

Yoko Yamashita

Yukihiro Goto

Tomoya Shimizu

Takeshi Yagi

Shoichiro Matsuo

Itaru Ishida

Fumihiko Yamamoto

Azusa Urushibara

Ryuichi Sugizaki

Shoji Tanigawa

Ryo Koyama

Masaaki Takaya

Yoshiteru Abe

Naomi Kumano

Iwao Shimotakahara

Harumi Inaba

Yusuke Yamada

Shinichi Arai

Kunimasa Saitoh

Kazuo Hogari

Kazunori Katayama

Chisato Fukai

Izumi Sankawa

Hiroki Hamaguchi

Shigeto Matsumoto

Katsusuke Tajima

Masatoshi Shimizu

Hideaki Murayama

Ryota Wada

Takeshi Fujisawa

Kyoichi Nakamizo

Jian Zhou

Saki Nozoe

Makito Kobayashi

Ryota Imada

Koutaro Saito

Noriyuki Araki

Kotaro Saitoh

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 according to the present invention includes: a grating portion in which a fiber Bragg grating that reflects light of a desired wavelength is formed in the core of an optical fiber, the light of the desired wavelength being of light propagating in the core; and a tap portion that is disposed at a stage before the grating portion in the propagation direction of the light, and is provided with a tap waveguide that outputs the light reflected by the grating portion from a side surface of the optical fiber.

Optical side input/output circuit and optical connector

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 μm 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 Δ1 relative to the core of the first cladding region and a specific refractive index Δ2 relative to the core of a second cladding region including four cores and the first cladding region.

Multicore optical fiber, method of designing multicore optical fiber, and optical transmission method

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.

Evaluation method and evaluation device for multi-core fiber

A shape measurement system and method for a three-dimensional shape of a linear object over a long distance with high resolution. The shape measurement system comprises: a multicore optical fiber having a center core positioned in the center of the cross section thereof and three or more outer peripheral cores positioned at equal intervals concentrically with respect to and outside of the center core; a measurement device for measuring the backward Brillouin scattered light distribution in the propagation direction of each core of the multicore optical fiber; and an analysis device for calculating position coordinates, in three-dimensional space, of a linear structure having an unknown three-dimensional shape from the backward Brillouin scattered light distributions of a multicore optical fiber positioned along the linear structure having an unknown three-dimensional shape and a multicore optical fiber positioned along a linear structure having a known three-dimensional shape.

Shape measurement system and shape measurement method

The optical fiber according to the present invention includes, in a cross section of the optical fiber, one core region () and a cladding region () that is arranged on an outer periphery of the core region. The cladding region is a medium that has a lower refractive index than that of the core region and also has a smaller refractive index wavelength dispersion than that of the core region. The optical fiber has a solid core and therefore, allows more reduction in the Rayleigh scattering loss compared to an optical fiber having a hollow core. In addition, since the optical fiber adopts, for the cladding region, a medium that has a smaller refractive index wavelength dispersion than that of the core region, it allows a reduction in the wavelength dispersion of n.

Optical fiber

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 A. 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 0.1 dB/turns or smaller, and the inter-core crosstalk at the wavelength of 1.625 μm is −47 dB/km or smaller.

Multi-core optical fiber and design method

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 Λ 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.

Provided are an LPFG and an optical transmission system in which a mode conversion amount does not depend on a polarization state and an electric field distribution. The LPFG according to the present invention includes cavity rows (-and-) of cavitiesperiodically arranged in a core regionof the few-mode fiberat a position away from a central axis z of the core regionin parallel with the central axis z. Each of the cavity rows (-and-) is located at a different position in a longitudinal direction of the few-mode fiber(where the position in a z direction is different), and the cavity rows (-and-) are located at positions shifted by 90° on a cross section of the core regionwith the center of the cross section of the core region(the intersection of an x-axis and a y-axis) as an origin.

Long period fiber grating and optical transmission system

A mode loss difference compensator of the present disclosure includes a main waveguide configured to allow propagation of N or more modes (where N is an integer of 3 or more), a first auxiliary waveguide having, at one end thereof, a first coupling portion configured to mode-convert an LP0n mode (where n is an integer of 2 or more) propagating in the main waveguide into a fundamental mode in the first auxiliary waveguide and transfer the fundamental mode from the main waveguide to the first auxiliary waveguide and having, at the other end thereof, a second coupling portion configured to mode-convert the fundamental mode propagating in the first auxiliary waveguide into the LP0n mode (where n is an integer of 2 or more) in the main waveguide and transfer the LP0n mode from the first auxiliary waveguide to the main waveguide, and a second auxiliary waveguide having, at one end thereof, a third coupling portion configured to convert a higher-order mode, other than any LP0n mode (where n is an integer of 2 or more), propagating in the main waveguide into a fundamental mode in the second auxiliary waveguide and transfer the fundamental mode from the main waveguide to the second auxiliary waveguide and having, at the other end thereof, a terminal end portion configured to eliminate the fundamental mode propagating in the second auxiliary waveguide from the second auxiliary waveguide, wherein the main waveguide includes a loss imparting portion configured to impart a loss to a fundamental mode propagating in the main waveguide between the first and second coupling portions.

Propagation mode loss difference compensator

A multi-core optical fiber includes four cores arranged in a shape along a longitudinal direction, each of the four cores having a step-index type refractive index distribution with a radius, and a cladding region having a lower refractive index than that of each core and a diameter of 125±1 μm and provided on an outer portion of each core. An absolute value of a relative refractive index difference between each core and the cladding region is Δ. The four cores are arranged so that a relationship between a minimum distance from the center of each core to an outer periphery of the cladding region, a minimum value A of spacing between the cores, and the MFD at a set wavelength satisfies a Formula C1, and the radius of each core and the relative refractive index difference Δ between the core and the cladding region are set.

Multicore optical fiber and design method

The purpose of the present invention is to provide an optical fiber evaluation equipment and an optical fiber evaluation method that evaluate the center of a cladding of an MCF and a deviation of the center of each core of the MCF from a design value with ease and high accuracy. The optical fiber evaluation equipment according to the present invention approximates the outside diameter of a cladding by a circle, based on a cross-sectional image of an MCF, and determines the center of the circle as the center of the cladding. In addition, the optical fiber evaluation equipment according to the present invention obtains the center coordinates of cores with an origin at the center of the circle, rotates the cross-sectional image so as to minimize a difference between the center coordinates and design coordinates of each core, and derives the minimum value thereof as the amount of deviation of the center of each core.

Optical fiber evaluation device and optical fiber evaluation method

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.

Optical transmission system

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. The multi-core optical fiber according to the present invention is an optical fiber in which two or more core regions are arranged in a cladding region having a refractive index lower than a refractive index of the core at a minimum core interval, a ring-shaped low refractive index region surrounding the core and having a refractive index lower than the refractive index of the cladding region is provided, a bending loss after the provision of the ring-shaped low refractive index region is reduced as compared with a characteristic in a case where the ring-shaped low refractive index region is not provided, and at the same time, a change in mode field diameter after the provision of the ring-shaped low refractive index region is not changed as compared with a characteristic in a case where the ring-shaped low refractive index region is not provided.

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. The present optical transmission system includes an optical fiberwith the number of spatial modes being L (an integer of 2 or greater), an optical multiplexerconnected to one end of the optical fiberand configured to input M (a natural number of L or less) signal beams of light to the optical fiberand cause the M input signal beams of light to be propagated for each of the spatial modes of the optical fiber, an optical demultiplexerconnected to another end of the optical fiberand configured to demultiplex a propagated beam of light propagated through the optical fiberfor each of the spatial modes of the optical fiber, N (N=L) receiversconfigured to each receive a demultiplexed beam of light obtained by demultiplexing the propagated beam of light, a signal generation apparatusconfigured to generate P (an integer of from M to L) combined signals from the N received signals, and a P×M MIMO equalizerconfigured to receive the P combined signals to output M demodulated signals.

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. By forming a waveguide on a glass substrate serving as a connection destination so as to match the absolute positions of the cores, the rotational and positional displacements of the MCF can be eliminated, thus making it possible to reduce the connection loss.

Core position grasping method, connection method, and connection device

Growing community of inventors

Tsukuba, Japan

Kazuhide Nakajima