公开(公告)号：US20220214496A1

公开(公告)日：2022-07-07

申请号：US17605758

申请日：2020-04-06

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Taiji SAKAMOTO ,  Kazuhide NAKAJIMA ,  Masaki WADA ,  Shinichi AOZASA ,  Takashi YAMAMOTO

IPC: G02B6/02 ,  G02B27/00

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 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−1.

公开(公告)号：US20170160466A1

公开(公告)日：2017-06-08

申请号：US15440228

申请日：2017-02-23

Applicant: FURUKAWA ELECTRIC CO., LTD. ,  NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Katsunori IMAMURA ,  Tomohiro GONDA ,  Ryuichi SUGIZAKI ,  Taiji SAKAMOTO ,  Takayoshi MORI ,  Masaki WADA ,  Takashi YAMAMOTO ,  Fumihiko YAMAMOTO

IPC: G02B6/02 ,  C03B37/16 ,  C03B37/012 ,  G02B6/028

CPC classification number: G02B6/02042 ,  C03B37/01205 ,  C03B37/01222 ,  C03B37/027 ,  C03B37/16 ,  C03B2203/10 ,  C03B2203/18 ,  C03B2203/22 ,  C03B2203/23 ,  C03B2203/26 ,  C03B2203/34 ,  C03B2205/30 ,  G02B6/0288 ,  G02B6/0365

Abstract: A multicore fiber includes a plurality of unit multicore fibers each including: a plurality of core portions; and a clad portion which is formed in an outer circumference of the core portions and has a refractive index lower than a maximum refractive index of the core portions. The plurality of the core portions have substantially same refractive index profile and different group delays at same wavelength in same propagation mode. The core portions of the multicore fiber are configured so that the core portions of the plurality of the unit multicore fibers are connected in cascade, a maximum value of differential group delays between the core portions of the multicore fiber is smaller than a reduced value of a maximum value of differential group delays between the core portions of each unit multicore fiber as a value in terms of a length of the multicore fiber.

公开(公告)号：US20220294537A1

公开(公告)日：2022-09-15

申请号：US17633902

申请日：2019-08-23

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Taiji SAKAMOTO ,  Masaki WADA ,  Takashi YAMAMOTO ,  Kazuhide NAKAJIMA

IPC: H04B10/61 ,  H04B10/2581 ,  H04B10/2575

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.

公开(公告)号：US20200225407A1

公开(公告)日：2020-07-16

申请号：US16633424

申请日：2018-07-31

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Azusa URUSHIBARA ,  Taiji SAKAMOTO ,  Masaki WADA ,  Takashi YAMAMOTO ,  Kazuhide NAKAJIMA ,  Takayoshi MORI

IPC: G02B6/02 ,  H01S3/10 ,  H04B10/2581

Abstract: 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 LP02 mode is greater than or equal to 4.8 and less than or equal to 6.4.

公开(公告)号：US20190196106A1

公开(公告)日：2019-06-27

申请号：US16322432

申请日：2017-08-01

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Masaki WADA ,  Taiji SAKAMOTO ,  Takayoshi MORI ,  Shinichi AOZASA ,  Takashi YAMAMOTO ,  Kazuhide NAKAJIMA

IPC: G02B6/26 ,  G02B6/036 ,  G02B6/02

Abstract: 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.

公开(公告)号：US20220360358A1

公开(公告)日：2022-11-10

申请号：US17760541

申请日：2019-09-17

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Taiji SAKAMOTO ,  Masaki WADA ,  Takashi YAMAMOTO ,  Kazuhide NAKAJIMA

IPC: H04J14/04 ,  H04B10/2581 ,  H04B7/0413 ,  H04B10/079

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. The present optical transmission system includes an optical fiber 11 with the number of spatial modes being L (an integer of 2 or greater), an optical multiplexer 13 connected to one end of the optical fiber 11 and configured to input M (a natural number of L or less) signal beams of light to the optical fiber 11 and cause the M input signal beams of light to be propagated for each of the spatial modes of the optical fiber 11, an optical demultiplexer 14 connected to another end of the optical fiber 11 and configured to demultiplex a propagated beam of light propagated through the optical fiber 11 for each of the spatial modes of the optical fiber 11, N (N=L) receivers 15 configured to each receive a demultiplexed beam of light obtained by demultiplexing the propagated beam of light, a signal generation apparatus 17 configured to generate P (an integer of from M to L) combined signals from the N received signals, and a P×M MIMO equalizer 16 configured to receive the P combined signals to output M demodulated signals.

公开(公告)号：US20190386748A1

公开(公告)日：2019-12-19

申请号：US16312051

申请日：2017-07-04

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Takayoshi MORI ,  Taiji SAKAMOTO ,  Takashi YAMAMOTO ,  Kazuhide NAKAJIMA ,  Masaki WADA ,  Azusa URUSHIBARA

IPC: H04B10/2581 ,  G02B6/02 ,  H04B10/50 ,  H04B10/60

Abstract: 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 μm2 or 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.

公开(公告)号：US20190245317A1

公开(公告)日：2019-08-08

申请号：US16343357

申请日：2017-10-25

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Masaki WADA ,  Shinichi AOZASA ,  Taiji SAKAMOTO ,  Takashi YAMAMOTO ,  Kazuhide NAKAJIMA ,  Takayoshi MORI

IPC: H01S3/067 ,  H01S3/106 ,  H04B10/2581

CPC classification number: H01S3/06791 ,  H01S3/067 ,  H01S3/0675 ,  H01S3/06754 ,  H01S3/10 ,  H01S3/106 ,  H04B10/2581

Abstract: 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.

公开(公告)号：US20190187365A1

公开(公告)日：2019-06-20

申请号：US16327946

申请日：2017-08-25

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Azusa URUSHIBARA ,  Takayoshi MORI ,  Taiji SAKAMOTO ,  Masaki WADA ,  Takashi YAMAMOTO ,  Kazuhide NAKAJIMA

IPC: G02B6/02 ,  G02B6/14 ,  G02B6/44 ,  H04B10/2581

Abstract: 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 (83) that includes an optical fiber with two or more propagation modes; and a plurality of mode converters (91) 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 (91) is equal to or less than a threshold value determined by the transmission line length (Lt) of the optical fiber transmission line (83).