Nippon Telegraph and Telephone Corporation

The Furukawa Electric Co., Ltd.

Fujikura Limited

Taiji Sakamoto

Takashi Matsui

Kazuhide Nakajima

Masaki Wada

Takashi Yamamoto

Takayoshi Mori

Shinichi Aozasa

Yuto Sagae

Azusa Urushibara

Shoichiro Matsuo

Katsuhiro Takenaga

Ryuichi Sugizaki

Kunimasa Saitoh

Shoji Tanigawa

Katsunori Imamura

Yoshiteru Abe

Kyozo Tsujikawa

Nobutomo Hanzawa

Fumihiko Yamamoto

Shigeru Tomita

Tomohiro Gonda

Yoko Yamashita

Kyouzou Tsujikawa

Takeshi Fujisawa

Koutaro Saito

Kotaro Saitoh

Ryota Imada

Noriyuki Araki

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.

Multi-core optical fiber and design method

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.

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

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.

Multicore optical fiber and design method

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 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.

Optical communication system and optical communication method

A planar waveguide having M&#xd7;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&#xd7;N is equal to P&#xd7;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&#xd7;N number of cores are constant in the height direction, and change only in the horizontal direction.

Multi-core fiber connector

An optical amplifier of the present disclosure includes an optical resonator that includes an amplification fiber capable of amplifying signal light having one or more propagation modes and resonates at least one propagation mode of the signal light amplified by the amplification fiber; an excitation light source that outputs excitation light for exciting the amplification fiber; and a multiplexer that multiplexes the signal light and the excitation light, in which the optical resonator includes a gain clamp setting unit which sets gain clamp for at least one propagation mode out of a plurality of propagation modes resonating in the optical resonator.

Optical amplifier

The optical fiber of the present invention includes a core, and a cladding that is provided on an outer periphery of the core and has a refractive index lower than a refractive index of the core region. In the optical fiber of the present invention, a V value representing a normalized frequency of an LPmode is greater than or equal to 4.8 and less than or equal to 6.4.

Optical fiber and optical transmission system

The optical fiber according to the present disclosure is an optical fiber having a pure silica core which is a step index core through which an LPm1 mode with an effective area of 250 &#x3bc;mor more is propagated by setting a relative refractive index difference to 0.60% or less, considering an effective cutoff condition, and only 2 or more modes or the LPm1 mode are propagated, with the optical fiber as the transmission line.

A differential mode attenuation compensator includes a first multi-mode optical fiber and a third multi-mode optical fiber in which a plurality of propagation modes propagate in a wavelength of a propagating optical signal; and a second multi-mode optical fiber including a core and a clad and arranged with a central axis aligned between the first multi-mode optical fiber and the third multi-mode optical fiber, in which each loss in the plurality of propagation modes is different in the first multi-mode optical fiber and the third multi-mode optical fiber.

Inter-mode loss difference compensator and optical amplifier

An optical transmission system according to the present disclosure is a mode multiplexed optical transmission system using a multi-mode optical fiber in which a plurality of propagation modes propagate as a transmission line, the optical transmission system including an optical fiber transmission line () that includes an optical fiber with two or more propagation modes; and a plurality of mode converters () that are configured to generate mode coupling between at least one pair of the propagation modes, in which a variation in an installation interval of the plurality of mode converters () is equal to or less than a threshold value determined by the transmission line length (Lt) of the optical fiber transmission line ().

An alignment apparatus that can efficiently align an optical fiber, and an alignment method will be provided. According to the embodiments, the alignment apparatus that aligns an optical fiber comprises an acquisition unit, a calculation unit, and a rotation processing unit. The acquisition unit acquires one or more side images of the optical fiber. The calculation unit calculates correlation coefficients between the luminances of the one or more side images and those of one or more reference side images. The rotation processing unit rotates the optical fiber in the axis direction of the optical fiber so that the correlation coefficients peak.

Alignment apparatus and alignment method

An optical connector is provided which includes at least one multi-core block fixing and holding a plurality of multi-core optical fibers in a state where a position in a direction orthogonal to an optical axis of each multi-core optical fiber and a rotation angle around the optical axis are in a predetermined state, and a ferrule including an accommodating portion accommodating the multi-core block.

Growing community of inventors

Tsukuba, Japan

Taiji Sakamoto