公开(公告)号：US20230336338A1

公开(公告)日：2023-10-19

申请号：US18009399

申请日：2020-06-11

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Yuto SAGAE ,  Kazuhide NAKAJIMA ,  Taiji SAKAMOTO ,  Nobutomo HANZAWA ,  Takashi MATSUI ,  Noriyuki ARAKI ,  Shinichi AOZASA ,  Ryota IMADA ,  Yoko YAMASHITA

IPC: H04L9/08 ,  H04B10/25

CPC classification number: H04L9/088 ,  H04B10/25

Abstract: It is an object of the present disclosure to reduce the risk of information exploitation by a malicious third party while allowing communication data to be demodulated in real time. An optical transmission system according to the present disclosure includes a transmitter which transmits an optical signal representing a cryptographic key and an optical signal representing communication data individually, an optical transmission path including a heterogeneous multi-core optical fiber having multiple cores, at least one of which has a different propagation delay time, the optical transmission path transmitting the optical signal representing the cryptographic key using a first core with a smaller delay among the multiple cores and the optical signal representing the communication data using a second core with a greater delay than the first core, and a receiver which individually receives the optical signals representing the cryptographic key and the communication data output from the individual cores of the optical transmission path and demodulates the received communication data on the basis of the received cryptographic key information.

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：US20220337025A1

公开(公告)日：2022-10-20

申请号：US17762399

申请日：2019-09-26

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

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

IPC: H01S3/23 ,  H01S3/067

Abstract: An objective of the present invention is to provide an optical amplifier having a cladding excitation configuration that improves amplification efficiency. The optical amplifier includes an optical amplification unit 36 in which n (n is a natural number equal to or greater than 2) amplification fibers 34 that optically amplify signal light propagating through cores with excitation light supplied to claddings and n−1 optical input/output units 35 that input/output the signal light to/from the cores and the outside of the amplification fibers 34 are connected in series such that the amplification fibers 34 and the optical input/output units 35 are disposed in an alternating manner, an excitation light generator 31 that outputs the excitation light in multi-mode, and optical multiplexer/demultiplexers 33 that cause the excitation light from the excitation light generator 31 that has been divided into two light beams to be incident on the claddings of the amplification fibers 34 disposed at both ends of the optical amplification unit 36 and cause the signal light to be input to/output from the cores of the amplification fibers 34 disposed at both ends of the optical amplification unit 36.

公开(公告)号：US20220337020A1

公开(公告)日：2022-10-20

申请号：US17760713

申请日：2019-09-26

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

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

IPC: H01S3/094 ,  H01S3/067 ,  H01S3/16

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.

公开(公告)号：US20220337016A1

公开(公告)日：2022-10-20

申请号：US17760697

申请日：2019-09-26

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

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

IPC: H01S3/067

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.

公开(公告)号：US20250105578A1

公开(公告)日：2025-03-27

申请号：US18833531

申请日：2022-02-17

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Taiji SAKAMOTO ,  Ryota IMADA ,  Shinichi AOZASA ,  Kazuhide NAKAJIMA

IPC: H01S3/067 ,  H01S3/094

Abstract: An amplification optical fiber according to the present disclosure is an amplification optical fiber doped with a rare earth element, the amplification optical fiber including: a first cladding enclosing cores of the amplification optical fiber; and a second cladding enclosing the first cladding, in which the two or more cores are disposed inside the first cladding in a cross section of the amplification optical fiber, and a core cladding ratio Rcc, which is a ratio of a sum of areas of the two or more cores to a sum of areas of the two or more cores and the first cladding in the cross section of the amplification optical fiber, is 0.0095

公开(公告)号：US20240007189A1

公开(公告)日：2024-01-04

申请号：US18021991

申请日：2020-08-21

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Yuto SAGAE ,  Kazuhide NAKAJIMA ,  Takashi MATSUI ,  Taiji SAKAMOTO ,  Ryota IMADA

IPC: H04B10/291 ,  H04B10/25

CPC classification number: H04B10/2916 ,  H04B10/25 ,  G02B6/02042

Abstract: An object of the present invention is to provide an optical transmission system capable of satisfying XT required by a modulation system even if there is an inter-core loss difference in an MCF.
An optical transmission system of the present invention includes a multi-core optical fiber having a plurality of core regions and having different losses between at least two cores, a forward excitation light source and a multiplexing unit for allowing Raman amplification excitation light to be incident on each core of the multi-core optical fiber in the same direction as signal light, and a backward excitation light source and a multiplexing unit for allowing Raman amplification excitation light to be incident on each core of the multi-core optical fiber in a direction opposite to the signal light, wherein an intensity ratio of the forward excitation light to the backward excitation light is controlled (a ratio of power of excitation light is set to a predetermined value) such that crosstalk (XT) fluctuation between cores is reduced.

公开(公告)号：US20230280525A1

公开(公告)日：2023-09-07

申请号：US18024074

申请日：2020-09-04

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Takashi MATSUI ,  Kazuhide NAKAJIMA ,  Taiji SAKAMOTO ,  Yuto SAGAE

IPC: G02B6/028 ,  G02B6/02

CPC classification number: G02B6/0288 ,  G02B6/02042

Abstract: The present disclosure relates to a multi-core optical fiber including:
M (where M is a positive integer of 1 or larger) group(s) each consisting of N (where N is a positive integer of 2 or larger) core regions linearly arranged in a cross section; a cladding region that surrounds the plurality of core regions and has a refractive index lower than any of the plurality of core regions; and a coating region that surrounds the cladding region, wherein the plurality of core regions are arranged in line symmetry with respect to both imaginary lines orthogonal to each other at a center of the cladding region, a diameter of the cladding region is 180 μm or less, and a diameter of the coating region is 235 μm or more and 265 μm or less.

公开(公告)号：US20230163554A1

公开(公告)日：2023-05-25

申请号：US17913097

申请日：2020-03-30

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Shinichi AOZASA ,  Yoko YAMASHITA ,  Takashi MATSUI ,  Kazuhide NAKAJIMA ,  Taiji SAKAMOTO ,  Nobutomo HANZAWA ,  Noriyuki ARAKI ,  Ryota IMADA ,  Yuto SAGAE

IPC: H01S3/067 ,  G02B6/32 ,  G02B3/08

CPC classification number: H01S3/06754 ,  G02B3/08 ,  G02B6/32 ,  H01S3/1608

Abstract: An object of the present disclosure is to implement a clad-excitation rare-earth-added optical fiber amplifier with a high light-to-light conversion efficiency. The present disclosure is an optical fiber amplifier having, in a longitudinal direction of a rare-earth-added optical fiber, a light collection structure that collets an excitation light, which propagates through a clad portion, into a core portion.