JP5952764B2 - Fiber fuse stopper, optical connector, and optical transmission system - Google Patents

Description

  The present invention provides a fiber fuse stopper that stops or suppresses a fiber fuse phenomenon that may occur when high-power light of several W (watts) order is input to and transmitted to an optical fiber, and protects a transmission device and an optical fiber transmission line, The present invention relates to an optical connector and an optical transmission system.

  Currently, due to the progress of the Internet and the like, the demand for expanding the transmission capacity in optical fiber communication is increasing day by day, and the optical power input to the optical fiber of the backbone network is already approaching 1W. Further increases are expected in the future. On the other hand, in the situation where light of several watts is input to a conventional optical fiber, a local high temperature part is generated in the fiber core part due to bending, cutting, heating, etc., and this becomes a high temperature plasma state toward the light source part. It is known that a phenomenon of propagation (fiber fuse) occurs.

  If the generated fiber fuse is not stopped, the optical fiber transmission path from the generation point to the light source is not only destroyed, but the light source (transmission device) is also destroyed. Therefore, there is a strong demand for a method that does not cause the fiber fuse phenomenon or stops the propagation of the generated fiber fuse.

  When the input power is made smaller than a certain value, propagation of the fiber fuse is stopped. This value is called a propagation threshold. It has been reported that propagation thresholds in conventional optical fibers such as SMF (1.3 um band zero dispersion fiber) and DSF (dispersion shifted fiber) are about 1.5 W and 1.2 W, respectively.

  Thus, various fuse stoppers have been proposed as countermeasures for fiber fuses in the transmission line. When using the fuse stopper, if the input optical power is set below the propagation threshold value in the stopper part, even if a fuse is generated in a part other than the stopper, the fuse stops at the stopper part and the remaining transmission line and The light source part can be protected. As a fuse stopper, one in which a fiber having a particularly high propagation threshold is inserted as a small optical component (fuse stopper) in a part of an optical transmission line has been proposed.

  Specifically, fuse stoppers (for example, patents) made of non-patent document 1 to non-patent document 3 or fibers having a higher propagation threshold (HAF or photonic crystal fiber (PCF)). Reference 1)) has been reported.

JP2012-163802A

Fujita et al., “Fibre Fuse Breaking with GI Fiber”, 2004 IEICE Communication Society Conference, B-10-5, 2004 Yanagi et al., “Development of Fiber / Fuse Breaking Parts”, IEICE Technical Report, OPE 2004-178, 2004 E. M.M. Dianov. et. al. "Destination of silica fiber cladding by the fuse effect", OPTICS LETTERS, 29, 16, p. p. 1852-1854, 2004

  When stopping the propagation of the fiber fuse using the HAF, it is possible to increase the effectiveness of stopping the propagation of the fiber fuse with a structure in which the holes are arranged relatively close to the core. However, with such a structure, there is a problem that multimode HAF easily occurs in the used wavelength band.

  Accordingly, in order to solve the above-mentioned problems, the present invention provides a fiber fuse stopper, an optical connector, and an optical transmission system that can prevent the effects of multi-modes of HAF while keeping the effect of stopping propagation of the fiber fuse high. The purpose is to do.

  It is desirable to shorten the length of the HAF in order to suppress as much as possible the influence of the multimode HAF that may be generated when the propagation stopping force of the fiber fuse is improved. In Patent Document 1, the length of the HAF is set to 0.5 mm or more and 5 mm or less in order to solve the above problem. As a result of intensive studies to further shorten the length of the HAF, the present inventors have found that the fiber fuse can be stopped using a HAF having a length of less than 0.5 mm. That is, in order to achieve the above object, the fiber fuse stopper according to the present invention uses HAF of 0.1 mm or more and less than 0.5 mm.

  Specifically, in the fiber fuse stopper according to the present invention, a part of the optical transmission path is a hole assisted optical fiber (HAF: Hole Assisted Fiber) whose length in the light propagation direction is 0.1 mm to 0.5 mm. ). By arranging the HAF having the length in the middle of the optical transmission line, it is possible to prevent the influence of the HAF from becoming multimode while keeping the effect of stopping the propagation of the fiber fuse high.

  The optical transmission path of the fiber fuse stopper according to the present invention includes the HAF and single mode optical fibers connected to both ends of the HAF.

  The fiber fuse stopper according to the present invention is characterized in that the mode field diameter of the HAF and the mode field diameter of the single mode optical fiber are substantially equal in a wavelength region of propagating light. Insertion loss can be reduced when the HAF is disposed in the optical fiber transmission line.

  The optical connector which concerns on this invention is equipped with the said fiber fuse stopper. Since the length of the HAF is short, it can be accommodated in the optical connector.

  The optical transmission system according to the present invention includes an optical fiber transmission line that connects two optical transmission devices, and the optical fiber transmission line includes the fiber fuse stopper.

An optical transmission system according to the present invention includes an optical fiber transmission line that connects two optical transmission apparatuses, and the optical fiber transmission line includes the optical connector.

  The fiber fuse stopper, the optical connector, and the optical transmission system according to the present invention can suppress the other mode due to the HAF, the insertion loss is sufficiently small, and the fiber fuse generated at the time of high input power can be stopped.

  The present invention can provide a fiber fuse stopper, an optical connector, and an optical transmission system that can prevent the influence of multi-modes of HAF while keeping the effect of stopping propagation of the fiber fuse high.

It is a figure which shows an example of sectional drawing of HAF used by this invention. It is a figure which shows an example of the use in the optical transmission line of the fiber fuse stopper used by this invention. It is a figure which shows an example of the operation | use within the communication station of the fiber fuse stopper used by this invention. It is a figure which shows the example which applies the fiber fuse stopper used by this invention to an optical fiber connector.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
This embodiment relates to an example of the structure in the cross section of the HAF used for the fiber fuse stopper according to the present invention and an example of use in the optical transmission line.

  FIG. 1 is an example of a sectional view of a HAF used for the fiber fuse stopper 10 of the present embodiment. The HAF includes a core part 11, a cladding part 12, and holes 13. The relative refractive index difference Δ between the core portion 11 and the clad portion 12 is typically about 0.3 to 0.4%, and the core radius a is typically about 3.5 to 5 μm. Good. The relative refractive index difference Δ and the core radius a are not limited to these.

  The diameter d of the holes 13 may be a value of about 2 to 10 μm, and the number of the holes 13 may typically be a value of about 1 to 20. The diameter d and the number of the holes 13 are not limited to these.

  The shortest distance R from the cross-sectional center to the hole 13 is defined as the minimum value of the radius of these inscribed circles when inscribed circles from the cross-sectional center to the respective holes 13 are drawn. R may typically be a value of about 3.5 to 10 μm.

  The larger the hole diameter d, the stronger the function of stopping the fiber fuse propagation. Therefore, when R is large, it is preferable to increase d. Further, the position of the hole 13 in the cross section is not limited to the region of the cladding part 12, and the whole or part of the hole 13 may be included in the region of the core part 11.

  FIG. 2 is an example of an optical fiber transmission line provided with a fiber fuse stopper. The optical fiber transmission line connects the two optical transmission devices. In FIG. 2, a light source 22 and a light receiver 23 are shown as an optical transmission device. The fiber fuse stopper 10 is a HAF. The transmission optical fiber 21 has a fuse propagation threshold value lower than that of the fiber fuse stopper 10.

  The fiber fuse stopper 10 is inserted between the optical fibers 21 for transmission, and the output light power of the light source 22 is set in advance below the fuse propagation threshold of the fiber fuse stopper 10. With this setting, if a fiber fuse is generated near the light receiver 23 in the transmission optical fiber 21, the generated fiber fuse can be stopped by the fiber fuse stopper 10.

  It is desirable to install the fiber fuse stopper 10 at a position close to the light source 22. The light source 22 can be reliably protected. Further, a plurality of fiber fuse stoppers 10 may be used at a plurality of locations as required.

  In other words, when inputting light having a large power in the vicinity of 4 W or much exceeding that to an optical transmission line such as a conventional commercial optical fiber, the fiber fuse stopper 10 of this embodiment is inserted at an appropriate position in the middle of the transmission line. By doing so, even if a fiber fuse is generated, the fiber fuse stopper 10 can be stopped and the transmission line and the transmission device can be protected.

  From the viewpoint of use in an optical fiber transmission line, it is desirable that the fiber fuse stopper 10 has a small insertion (connection) loss. In order to reduce the insertion loss of the fiber fuse stopper, the mode field diameter of a commercial single mode fiber (SMF, DSF, etc.) used as an optical fiber transmission line and the mode field diameter of the HAF that is the fiber fuse stopper 10 are roughly outlined. Matching is effective.

  The effect of the fiber fuse stopper of this embodiment will be described. Using SMF as the transmission optical fiber 21 and HAF less than 0.5 mm (0.45 mm) in length as the fiber fuse stopper 10, an experiment was conducted to stop the fiber fuse when the input power is 5 W at a wavelength of 1480 nm. Confirmed with. The core diameter, hole diameter, and R value of the HAF used at this time were 9, 9.1, and 9.3 μm, respectively. The number of holes was 6. The fiber fuse propagating through the SMF entered the HAF by about 60 μm from the connection point between the SMF and the HAF and stopped. Since the penetration length into the HAF is about 60 μm, it is understood that the HAF length as the fiber fuse stopper 10 should be 0.1 mm or more.

(Embodiment 2)
This embodiment relates to application of the fiber fuse stopper of the present invention in a communication station.

  FIG. 3 is a diagram illustrating an example in which the fiber fuse stopper of the present embodiment is applied in a communication station. The optical communication system of FIG. 3 includes a transmission device 31 including a light source, optical fiber cords (32, 33, 34), an optical fiber cable 35, a station inner housing 36 for an optical fiber core in a communication station, and an optical fiber in the communication station. It is the transmission line side accommodation rack 37 of the core wire. There is also a transmission device at the user's home (not shown). The optical fiber transmission is configured by the optical fiber cord (32, 33, 34) and the optical fiber cable 35.

  From the viewpoint of reliably protecting the transmission device 31, it is desirable to use the fiber fuse stopper in a user building, home, or communication station close to the transmission device 31. In the configuration of FIG. 3, the fiber fuse stopper can be used for some or all of the optical fiber cords (32, 33, 34).

(Embodiment 4)
This embodiment relates to application of the fiber fuse stopper of the present invention to optical connectors such as SC, FC, and MU.

  If a HAF having a length of less than 0.5 mm is installed inside the optical connector, the fiber fuse can be stopped by the optical connector.

  FIG. 4 is a view for explaining an optical connector 40 incorporating the fiber fuse stopper of the present embodiment. The existing optical fiber 41 is a conventional SMF or DSF. In the optical connector 40, the fiber fuse stopper 10 (HAF) is installed between the optical fibers 41.

  The fiber fuse can also be stopped by using the optical connector incorporating the fiber fuse stopper for connection at the connection point in FIG.

(Other embodiments)
The first to fourth embodiments have been described by stopping the fiber fuse near the wavelength of 1500 nm that is currently used in optical communication. Furthermore, fiber fuse stoppers for short wavelengths, for example, the wavelength region such as the 1000 nm band and the visible region, have a mode field diameter (MFD) that decreases as the wavelength becomes shorter, so the R value is set smaller than in the 1500 nm band. Good. On the contrary, in the long-wavelength fiber fuse stopper, since the MFD increases as the wavelength increases, the value of R may be set slightly larger than that in the 1500 nm band.

  In the above embodiment, the HAF itself is described as a fiber fuse stopper. However, an optical transmission line having a structure in which both ends of the HAF are sandwiched between optical fibers is also the fiber fuse stopper of the present invention.

The following describes the fiber fuse stopper, the optical connector, and the optical transmission system of the present embodiment.
<Issues>
It is an object of the present invention to provide a fiber fuse stopper, an optical connector, and an optical transmission system that can solve the conflicting events of being highly effective in stopping propagation of fiber fuses and preventing the effects of multimode HAF. .

<Means>
(1):
A single mode optical fiber having a mode field diameter substantially equal to the mode field diameter of the HAF is connected to both ends of the HAF, and the length of the HAF is 0.1 mm or more and less than 0.5 mm. Fiber fuse stopper.
(2):
An optical connector comprising the fiber fuse stopper of (1) above.
(3):
An optical fiber transmission line for connecting two optical transmission devices is provided, and the optical fiber transmission line is connected to the fiber fuse stopper (1) or the optical connector (2) and a transmission optical fiber. An optical transmission system characterized by that.

<Effect>
The present invention can provide a fiber fuse stopper, an optical connector, and an optical transmission system that stop a fiber fuse generated at a high input power with sufficiently small insertion loss.

10: Fiber fuse stopper (HAF)
11: Core portion 12: Cladding portion 13: Hole 21: Transmission optical fiber 22: Light source 23: Light receiver 31: Transmission device 32, 33, 34: Optical fiber cord 35: Optical fiber transmission line or optical fiber cable 36 37: Housing 40: Optical connector 41: Optical fiber

Claims (6)

A fiber fuse stopper for stopping a fiber fuse generated when light having a power of 4 W or more and 5 W or less is input to an optical transmission line,
Some of the optical transmission path, the length of the propagation direction of light is 0.1mm or more 0.5mm following hole-assisted optical fiber (HAF: Hole Assisted Fiber) der is,
A fiber fuse stopper, wherein the shortest distance from the cross-sectional center of the HAF to a hole is 3.5 μm or more and 10 μm or less .
  The fiber fuse stopper according to claim 1, wherein the optical transmission path includes the HAF and single mode optical fibers connected to both ends of the HAF.   3. The fiber fuse stopper according to claim 2, wherein a mode field diameter of the HAF and a mode field diameter of the single mode optical fiber are substantially equal in a wavelength region of propagating light.   An optical connector comprising the fiber fuse stopper according to claim 1. An optical fiber transmission line connecting the two optical transmission devices;
The optical fiber transmission line is
An optical transmission system comprising the fiber fuse stopper according to claim 1. An optical fiber transmission line connecting the two optical transmission devices;
The optical fiber transmission line is
An optical transmission system comprising the optical connector according to claim 4.

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