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：US20240072507A1

公开(公告)日：2024-02-29

申请号：US18269611

申请日：2021-01-21

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Shinichi AOZASA ,  Taiji SAKAMOTO ,  Kazuhide NAKAJIMA ,  Takashi MATSUI

IPC: H01S3/10 ,  F21V8/00

CPC classification number: H01S3/10023 ,  G02B6/0003

Abstract: The purpose of the present invention is to provide an optical fiber amplifier capable of seamlessly and collectively amplifying optical signals in a plurality of bands.
In order to achieve the aforementioned purpose, the optical fiber amplifier according to the present invention is the optical fiber amplifier that amplifies multiple wavelength bands, and in cross-section, one signal light primary propagation region, and a doped region where rare-earth ions have been added, wherein the doped region includes the rare-earth-doped optical fiber existing other than the propagation region. The optical fiber amplifier uses the fact that the main propagation regions of the signal light are made the same in the fiber cross-section of the rare-earth-doped optical fiber and the propagation regions of the signal light are partially different in the signal wavelength, and adds rare-earth ions to the partially different propagation regions to make amplification factors different for each signal wavelength and flatten the gain of each amplification wavelength band.

公开(公告)号：US20230324604A1

公开(公告)日：2023-10-12

申请号：US18024559

申请日：2020-09-09

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

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

IPC: G02B6/02

CPC classification number: G02B6/02095

Abstract: 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 (25-1 and 25-2) of cavities 15 periodically arranged in a core region 11 of the few-mode fiber 10 at a position away from a central axis z of the core region 11 in parallel with the central axis z. Each of the cavity rows (25-1 and 25-2) is located at a different position in a longitudinal direction of the few-mode fiber 10 (where the position in a z direction is different), and the cavity rows (25-1 and 25-2) are located at positions shifted by 90° on a cross section of the core region 11 with the center of the cross section of the core region 11 (the intersection of an x-axis and a y-axis) as an origin.

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：US20220344888A1

公开(公告)日：2022-10-27

申请号：US17762403

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 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.