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OPTICAL SIGNAL TRANSMISSION SYSTEM AND OPTICAL FIBER

Foreign code F190009843
File No. (S2017-1128-N0)
Posted date Jul 25, 2019
Country WIPO
International application number 2018JP038134
International publication number WO 2019078117
Date of international filing Oct 12, 2018
Date of international publication Apr 25, 2019
Priority data
  • P2017-203869 (Oct 20, 2017) JP
Title OPTICAL SIGNAL TRANSMISSION SYSTEM AND OPTICAL FIBER
Abstract The purpose of the present invention is to suppress the delay of an optical signal propagating through an optical fiber while simultaneously improving the ease of manufacturing the optical fiber and reducing the propagation loss. The optical signal transmission system includes: an optical fiber (1) capable of propagating an optical signal with a plurality of modes; and a transmitter (2a) and a mode converter (3) for inputting the optical signal to the optical fiber (1). The transmitter (2a) and the mode converter (3) generate an optical signal with a specific high-order mode. The optical fiber (1) has a hollow core and is designed so that the loss of the optical signal with the specific high-order mode is less than the loss of the optical signal with a basic mode.
Outline of related art and contending technology BACKGROUND ART
, LAN(Local Area Network) optical fiber is used for the current communication in the communication of the relatively short distance such as, the diameter of the core, easily connected to the multi-mode optical fiber is used. On the other hand, if the slightly longer communication distance, polarization mode dispersion in the multimode optical fiber transmission distance, transmission of the limited capacity and therefore, region-based, mission critical, such as the sea, the communication distance is several tens of thousands km 1 km from many communication over about a small diameter core single mode optical fiber is widely used. In any case present in the optical fiber 1 is only a single light passage 1. In one of the passage 1 by the wavelength division multiplexing communication can be loaded with a plurality of signals and increase the capacity in communication, and realizes a large communication capacity communication.
1 Toward the further larger capacity in the current optical fiber has a plurality of light passage, a plurality of wavelength-multiplexed signal is propagated through the optical fiber at the same time using the spatial multiplexing optical communication method performed in the study.
Space multiplexing optical communication system having a plurality of cores and a multiplexing method using multi-core optical fiber core, one core is about 10 to 2 designed to have a propagation mode and a mode using the number of multi-mode optical fiber transmission system, but also a combination of these materials also has been studied.
Apart from these, light incident to the multimode optical fiber made to the method, all of the modes in the multimode optical fiber is not used, similar to the propagation characteristics of each mode can be selectively used to the extent of propagation of several tens of km for use in research have also been carried out (Patent Document 1, Patent Document 2).
These optical fibers is referred to as a high-speed optical communication is, the signal of the light propagated in the optical fiber to the speed of light is used as an optical fiber depends on the refractive index of the glass or plastic, which is a normal optical fiber cannot be greatly improved. Physical limit to the speed of light in the vacuum in order to approximate the speed of the optical signal propagated in the air can suffice. In the prior art, the aerial propagation is the wireless communication is used, the spatial parallel with a higher degree in order to increase the capacity is necessary to use signal processing MIMO(Multiple Input Multiple Output). A large-scale MIMO signal processing is the processing time is lengthy, a short propagation time characteristic cannot be attained.
In the first place, light, electrical and radio wave signal is sufficiently fast, it can be neglected with respect to the propagation delay time itself is not the most. Through a plurality of paths up to the relative delay time of the optical signal was a problem, the earlier the signal arriving at the delay signal according to a slow-to-one correspondence. However, in recent years, securities trading, such as a supercomputer interconnect, even a slight propagation delay time is desirable to reduce the emerging field.
The hollow optical fiber, a material of the optical fiber due to various constraints such as glass and plastic as means to solve have been performed research and development. Inside a hollow tube of a method of depositing a high-reflectance mirror for guiding light is the laser machining is used, the loss of light is large is not suitable for communication. A low-loss hollow optical fiber is proposed as a method of realizing, by a periodic structure of the dielectric energy in the electromagnetic wave (wavelength) of the dielectric and into the hollow core photonic band gap cannot be in the bandgap in the surrounding (non-patent document 1).
Is a dielectric multilayer on a concentric circle such as those of the structure of which some embodiments, the same principle. The communication system using the basic mode of the hollow of the bandgap, or, and designed so as to have a plurality of modes, can be used for mode multiplexing transmission is performed.
The cross section of the hollow around the hollow core of the bandgap in a structure in which a large number of regularly spaced holes. In the bandgap, the structure of the first cladding portion, the wavelength of the generated photonic band gap it is necessary to extend to infinity in the case where the same structure as the calculation of the calculation can be effectively (non-patent document 1) can be performed.
Patent Document 1 a method for generating the bandgap of 0.1mm to 1mm with the outer diameter of the narrow glass tube (capillary) and the optical fiber preform stack and draw method for bundling (or capillary method) is widely used a method called.
For this reason the holes in the hexagonal close-packed along the arrangement of the present invention. In this structure the refractive index of the material used for the optical fiber, and the diameter of the pores and the pore interval Λ to determine a characteristic of the photonic band gap, the larger the diameter of the pores is increased and the range of the photonic band gap, the cladding of the bandgap of the current cross-section of a regular hexagon with rounded angle are arranged in honeycomb shape. As extending to infinity in this structure, the wavelength of the desired wavelength generated in the photonic band structure so that the determining is performed.
Is the actual size of the bandgap of the cladding is limited. In order to control the confinement of light in the vicinity of the boundary region becomes weak, the optical fiber transmission loss is increased. In addition, the disturbance of the structure of the region in which a photonic band-gap narrowing, it becomes lowering of the confinement performance. In order to realize low-loss photonic bandgap structure as a cladding with little disturbance of the periodic structure over an area of the number of times the diameter of the core needs to be created.
Around the hollow core in a narrow capillary method for arranging the glass pipe, the hollow portion of the base material is difficult to retain the shape. The fiber base material to the alignment sequence of the pores at the drawing step. Holes to deteriorate the characteristics of the disturbance of the sequence for bandgap, Patent Document 1, Patent Document 2 at the time of creating the base material as the inner diameter of the core corresponding to the center have a thin glass tube by introducing a method of preventing the fluctuation of the sequence have been proposed.
However, a cylindrical hollow through a pipe surrounding the core and the core part of the light having a wavelength that passes through the binding occurs. Binding occurs for an increase in the loss at the wavelength, the thickness of the non-patent document 1 as of the cylindrical pipe is precisely controlled, the resonance state referred to create a surface of the glass surrounding the core and to reduce the intensity of the light inside the glass, low-loss and can be considered.
However, the created base of the optical fiber during the drawing of the surface tension of the glass to the glass wall around the core for the core in the circumferential direction of the thickness of the uniform has been difficult. Then reduce the loss of the bandgap as a method of Non-Patent Document 2 does not have the glass wall around the core as the glass of the inner cylinder portion is convex upward (toward the center) can be shown that there is valid, the bandgap of this structure is currently used.
Scope of claims (In Japanese)[請求項1]
 複数のモードの光信号を伝搬することができる光ファイバと、
 上記光ファイバに光信号を入力する送信装置と、を含み、
 上記送信装置は、特定の高次モードの光信号を生成し、
 上記光ファイバは、コア部が中空であり、基本モードの光信号の損失よりも上記特定の高次モードの光信号の損失が小さくなるように設計されている光信号送信システム。

[請求項2]
 上記送信装置は、上記特定の高次モードの光信号として、その電界分布が、cosθまたはcos2θの角度分布をなす光信号を生成する請求項1に記載の光信号送信システム。

[請求項3]
 上記光ファイバは、フォトニックバンドギャップファイバである請求項1または2に記載の光信号送信システム。

[請求項4]
 上記光ファイバは、上記コア部の外縁にガラス壁を有するとともに、規則的に配列された複数の空孔部をクラッド部に有し、
 上記ガラス壁の平均厚さと、上記空孔部の中心間距離との比は、0.03以上、0.05以下である請求項3に記載の光信号送信システム。

[請求項5]
 上記特定の高次モードの光信号は、LP 11モードの光信号であるか、またはTE 01モードの光信号のみを含むものである請求項1から4までの何れか1項に記載の光信号送信システム。

[請求項6]
 特定の高次モードの光信号を送信する光信号送信システムにおいて使用される光ファイバであって、
 コア部が中空であり、複数のモードの光信号を伝搬することができ、
 基本モードの光信号の損失よりも上記特定の高次モードの光信号の損失が小さくなるように設計されている光ファイバ。

  • Applicant
  • ※All designated countries except for US in the data before July 2012
  • OSAKA PREFECTURE UNIVERSITY
  • Inventor
  • KUBOTA, Hirokazu
  • OHASHI, Masaharu
  • MIYOSHI, Yuji
  • KOSAKE, Nobuaki
IPC(International Patent Classification)
Specified countries National States: AE AG AL AM AO AT AU AZ BA BB BG BH BN BR BW BY BZ CA CH CL CN CO CR CU CZ DE DJ DK DM DO DZ EC EE EG ES FI GB GD GE GH GM GT HN HR HU ID IL IN IR IS JO JP KE KG KH KN KP KR KW KZ LA LC LK LR LS LU LY MA MD ME MG MK MN MW MX MY MZ NA NG NI NO NZ OM PA PE PG PH PL PT QA RO RS RU RW SA SC SD SE SG SK SL SM ST SV SY TH TJ TM TN TR TT TZ UA UG US UZ VC VN ZA ZM ZW
ARIPO: BW GH GM KE LR LS MW MZ NA RW SD SL SZ TZ UG ZM ZW
EAPO: AM AZ BY KG KZ RU TJ TM
EPO: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
OAPI: BF BJ CF CG CI CM GA GN GQ GW KM ML MR NE SN ST TD TG

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