公开(公告)号：US20180321439A1

公开(公告)日：2018-11-08

申请号：US15772263

申请日：2016-11-17

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Takashi MATSUI ,  Kazuhide NAKAJIMA ,  Kyozo TSUJIKAWA ,  Fumihiko YAMAMOTO

IPC: G02B6/02 ,  G02B6/032

Abstract: A photonic crystal fiber according to the present invention has a plurality of holes arranged in the optical fiber along a longitudinal direction, in which the holes are arranged such that, in a cross section, a hole ratio which is an area of the holes per unit area is larger in a central side than in an outer side in a portion corresponding to a cladding and that a wide core area can be obtained while the number of modes that can be propagated is limited to several. Moreover, in a high-power optical transmission system according to the present invention, the amount of axis misalignment between the central axis of a laser oscillator and the central axis of the photonic crystal fiber is less than or equal to a certain amount.

公开(公告)号：US20180341104A1

公开(公告)日：2018-11-29

申请号：US15771040

申请日：2016-11-17

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Takashi MATSUI ,  Kazuhide NAKAJIMA ,  Kyozo TSUJIKAWA ,  Fumihiko YAMAMOTO

IPC: G02B27/00 ,  G02B6/02

Abstract: An optical fiber design method according to the present invention is a design method of a photonic crystal fiber having a plurality of holes arranged in the optical fiber along a longitudinal direction, in which a required effective cross-sectional area is calculated from a light wavelength, a transmission distance, and output power such that, in a cross section, a hole ratio which is an area of the holes per unit area is larger in a central side than in an outer side in a portion corresponding to a cladding, and a fiber structure (hole diameter and hole interval) corresponding to the effective cross-sectional area is calculated.

公开(公告)号：US20180172902A1

公开(公告)日：2018-06-21

申请号：US15563988

申请日：2016-03-22

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Takashi MATSUI ,  Kyozo TSUJIKAWA ,  Fumihiko YAMAMOTO ,  Nobutomo HANZAWA

IPC: G02B6/02

CPC classification number: G02B6/02328 ,  G02B6/02009 ,  G02B6/02309 ,  G02B6/02314 ,  G02B6/02347

Abstract: An object of the present invention is to provide a structure of an optical fiber capable of satisfying desired requirements of an output power, a propagation distance, and a beam quality. In the design of the PCF of the present invention, the PCF has air holes having diameters d and intervals Λ in an overlapping region where a region of Aeff of a desired value or more and a cutoff region in a desired higher-order mode overlap each other on a graph where the horizontal axis represents d/Λ and the vertical axis represents Λ, so that it is possible to sufficiently cut off the mode which is the desired higher-order mode or more, and thus, it is possible to select a region where the Aeff is large.

公开(公告)号：US20220170817A1

公开(公告)日：2022-06-02

申请号：US17434949

申请日：2020-02-19

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Yuto SAGAE ,  Takashi MATSUI ,  Kyozo TSUJIKAWA ,  Kazuhide NAKAJIMA

IPC: G01M11/00

Abstract: An objective is to provide an acoustic mode propagation speed measurement method and an acoustic mode propagation speed measurement device capable of measuring a propagation speed of an acoustic mode without cutting or processing an optical fiber wire.
According to the present invention, an acoustic mode propagation speed measurement method includes: acquiring a frequency shift spectrum of Brillouin scattered light generated in an optical fiber; fitting the frequency shift spectrum using a Gauss function; acquiring a spectral full-width at half maximum w from a fitted curve using the Gauss function; and calculating a propagation speed VA of an acoustic mode of the optical fiber by substituting the acquired spectral full-width at half maximum w into a linear function of the spectral full-width at half maximum w and the propagation speed VA of the acoustic mode.

公开(公告)号：US20190339513A1

公开(公告)日：2019-11-07

申请号：US16507570

申请日：2019-07-10

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Takashi MATSUI ,  Kazuhide NAKAJIMA ,  Kyozo TSUJIKAWA ,  Fumihiko YAMAMOTO

IPC: G02B27/00 ,  G02B6/02 ,  G02B6/032 ,  G02B6/42

Abstract: A photonic crystal fiber according to the present invention has a plurality of holes arranged in the optical fiber along a longitudinal direction, in which the holes are arranged such that, in a cross section, a hole ratio which is an area of the holes per unit area is larger in a central side than in an outer side in a portion corresponding to a cladding and that a wide core area can be obtained while the number of modes that can be propagated is limited to several. Moreover, in a high-power optical transmission system according to the present invention, the amount of axis misalignment between the central axis of a laser oscillator and the central axis of the photonic crystal fiber is less than or equal to a certain amount.

公开(公告)号：US20220334307A1

公开(公告)日：2022-10-20

申请号：US17641061

申请日：2019-09-18

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Saki NOZOE ,  Nobutomo HANZAWA ,  Yuto SAGAE ,  Kazuhide NAKAJIMA ,  Kyozo TSUJIKAWA

IPC: G02B6/02 ,  G02B6/032

Abstract: An object of the present invention is to provide an HAF having a structure in which the number of air holes is decreased to be smaller than that of a PCF and Rayleigh scattering loss may be more reduced than that in the existing HAF. The HAF according to the present invention includes a core portion having a uniform optical refractive index; a cladding portion having a uniform optical refractive index and surrounding the core portion; and a plurality of air holes arranged in two layers at positions configuring hexagonal closest packing excluding the core portion within the cladding portion along a longitudinal direction of the hole-assisted fiber, wherein a center-to-center spacing of the air holes is a sum of a radius Rin of an inscribed circle inscribed in the air holes in an inner layer and a radius d/2 of the air hole, and a radius “a” of the core portion and a relative refractive index difference Δ between the core portion and the cladding portion are present within a range where Rn, which is a ratio of a Rayleigh scattering coefficient Rsmf of a single mode optical fiber and an effective Rayleigh scattering coefficient Reff of the hole-assisted fiber, is equal to or less than 0.92.

公开(公告)号：US20220276430A1

公开(公告)日：2022-09-01

申请号：US17627866

申请日：2020-07-21

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Taiji SAKAMOTO ,  Kazuhide NAKAJIMA ,  Takashi MATSUI ,  Kyozo TSUJIKAWA ,  Kunimasa SAITOH ,  Takeshi FUJISAWA

IPC: G02B6/02 ,  G02B27/00

Abstract: 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.

公开(公告)号：US20190004246A1

公开(公告)日：2019-01-03

申请号：US15752809

申请日：2016-03-03

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Takashi MATSUI ,  Kyozo TSUJIKAWA ,  Fumihiko YAMAMOTO ,  Nobutomo HANZAWA

IPC: G02B6/02 ,  G02B6/42

CPC classification number: G02B6/02347 ,  B23K26/702 ,  G02B6/02 ,  G02B6/02314 ,  G02B6/02333 ,  G02B6/0288 ,  G02B6/42 ,  G02B6/4206

Abstract: An optical fiber that is a photonic crystal fiber in which a plurality of holes is arranged along a longitudinal direction of the optical fiber, having a predetermined bending radius R determined according to a transmission distance L of the optical fiber and optical power output from the optical fiber, and having an inter-hole distance Λ and a ratio d/Λ between a hole diameter d and the inter-hole distance Λ such that light of a predetermined number of modes is transmitted and a bending loss of the light of a fundamental mode with the predetermined bending radius R is equal to or smaller than a predetermined value.