JP2012127903A - Fiber fuse transmission blocking method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently detect an optical fiber fuse which may occur in an optical fiber communication field, stop a light source, and notify it to the outside.SOLUTION: The fiber fuse transmission blocking method includes: monitoring visible light emitted from a core portion when an optical fiber fuse occurs with a light receiver 3 arranged in the side face of an optical fiber; discriminating the occurrence of the optical fiber fuse with a discriminator 5 using an electric signal output from the monitor 3; stopping a high-power light source 1 causing the occurrence of the optical fiber fuse; and notifying it through an interface 6 for external notification.

Description

The present invention relates to a fiber fuse propagation blocking method which has been a problem in optical fiber communication.

In the optical fiber communication field, a multi-branch video distribution system using a high-power optical fiber amplifier having a light output of several watts, and amplifying signal light by injecting high-intensity excitation light together with a transmission signal into a transmission fiber (Raman amplification) ) The introduction of the backbone transmission system began. As a result, when strong light enters the optical fiber, the core of the optical fiber is broken (periodically or non-periodically on the core), starting from the light scattering point of the optical fiber and the end face contamination of the optical connector connecting the optical fibers. An optical fiber fuse (hereinafter abbreviated as FF) is generated and optical propagation becomes impossible (because the core of the optical fiber is broken (the waveguide structure is broken)). There was a problem. FIG. 7 shows an observation photograph of holes formed in the core of the optical fiber by the FF phenomenon as a reference. It can be seen that, due to the occurrence of the FF phenomenon, holes are formed in the optical fiber core and the waveguide structure is destroyed.

For this reason, the FF stop method described below has been invented so that the damage is not expanded even if the FF occurs accidentally.

Prior art 1 is a method of preventing FF propagation by increasing the optical threshold value through which the FF propagates by enlarging the mode field diameter of the optical fiber core. For example, it is described in Non-Patent Document 1.
S. Yanagi, et. al. "Fiber fuse terminator", The 5th Pacific Rim Conference on Lasers and Electro-Optics, vol. 1, p. 386, 2003

FIG. 8 shows Prior Art 1. The FF propagation light threshold value increases in proportion to the mode field diameter (MFD) of the optical fiber (see FIG. 8A). For this reason, the FF propagation light threshold value of the portion where the MFD is expanded in the optical fiber increases. That is, the FF propagation can be stopped at the portion where the MFD is enlarged (see FIG. 8B).

However, although the prior art 1 can prevent core destruction (hole formation) due to the FF phenomenon over the entire length of the optical fiber, it cannot report to the outside whether or not the FF phenomenon has occurred (for example, optical The problem was that the operation manager of the fiber communication system). For this reason, the prior art 2 was developed. The prior art 2 is a method of detecting the occurrence of FF and stopping the light causing the FF. FIG. 9 is a diagram for explaining the related art 2. For example, it is described in Non-Patent Document 2.
K. S. Abedin, et. al. , “Backreflected radiation due to a propagating fiber fuse”, Optics Express, vol. 17, no. 8, pp. 6525-6531, 2009

In this configuration, the reflected light reflected from the hole forming portion is branched by a tap coupler and received by an optical receiver, and then an electric signal output from the optical receiver is passed through an electric filter to pass through an electric power sensor (discriminator). ) To sense the occurrence of FF. When FF generation is detected, an output stop signal is sent from the electric power sensor to a high power light source that supplies high output light resulting in FF generation (for example, a stop signal is sent to the interlock input of the high power light source) The propagation of the FF is stopped by stopping the output of the light source. Also, by monitoring the output stop signal, the occurrence of FF can be monitored from the outside in the optical fiber communication system.

However, the prior art 2 has a tap coupler for receiving the return light reflected by the FF, a light receiver, an electric filter for observing an increase in the electric spectrum of a specific band, and an electric power sensor.
It was complicated and expensive because it consisted of (discriminator) and many parts.

The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above-described problems, reliably detect the FF phenomenon at low cost, and supply high-output light that generates FF. An object of the present invention is to provide a system capable of reporting the occurrence of FF to the outside together with a stopping method for stopping a high power light source.

In the FF stop method and FF notification method of the present invention, visible light emitted from a core portion heated to a high temperature when an FF is generated is monitored by an optical receiver disposed on the side surface of the optical fiber, and the electric power output from the monitor is output. A high-power light source that supplies high-power light that generates FF is stopped using a signal and notified to the outside. That is, it is possible to greatly reduce the number of components necessary for configuring the conventional technique 2 and to realize a low price. In addition, since visible light emitted from the side surface of the optical fiber is generated only when the FF is generated, the generation of the FF can be reliably monitored.

As described above, the FF stop method and the FF notification method of the present invention monitor the visible light emitted from the core portion heated to a high temperature when the FF is generated by the optical receiver disposed on the side surface of the optical fiber. A component necessary for constructing the prior art 2, characterized by stopping the high power light source that supplies high output light that generates FF using the electrical signal output from the monitor and notifying the outside Can be greatly reduced, and a low price can be realized, which contributes to the realization of an inexpensive FF stop method and FF notification method.

It is a figure explaining the notification of FF generation to the FF stop method of the present invention and the outside. It is a figure explaining the method to monitor FF generation in this invention. It is a figure explaining Example 1 of the present invention. It is a figure explaining Example 2 of this invention. It is a figure explaining Example 3 of this invention. It is a figure explaining Example 4 of this invention. It is the observation photograph of the void | hole formed in the core of an optical fiber by the phenomenon. It is a figure explaining prior art 1. FIG. It is a figure explaining the prior art 2. FIG.

Hereinafter, the present invention will be described in more detail with reference to the drawings. However, the embodiments disclosed below are merely examples of the present invention, and do not limit the scope of the present invention.

As the propagation blocking system of the first embodiment, the configuration shown in FIG. 1 is adopted. 1 is an output 5 W, wavelength 1550 nm, a high-power fiber laser with a remote interlock connector, 2 is a transparent UV-coated single mode fiber, 3 is a silicon photodiode (package: TO-5, light receiving area: 3 mmφ, cutoff) (Frequency: 100 MHz), 4 is an electric signal amplifier capable of variably amplifying current-voltage conversion and an amplification factor of 2 to 1000 times, 5 is a discriminator that outputs a TTL high level from an FF detection signal from the electric signal amplifier, 6 Used an interface that can report that the TTL level is in a high state in response to an inquiry via the Internet by the TTL High level. FIG. 3 shows the output of the silicon photodiode 3 when the FF generated by the light intensity 3W is detected, and the TTL high level signal output from the discriminator 5 based on the detection signal. The propagation speed of FF was ˜0.4 m / s.

In addition, this time, by controlling the remote interlock connector of the high-power fiber laser 1 by this TTL level signal, the high-power fiber laser is started in ~ ms or less after the core destruction part starts passing in front of the light receiver due to the FF phenomenon. The output of 1 was stopped and the FF propagation prevention could be carried out promptly.

In addition, it was possible to obtain information that the FF phenomenon occurred by accessing the notification interface 6 via the Internet. In Example 1, the transparent UV-coated single mode fiber 2 was used. However, even in a state where the UV coat is removed, or in a colored (white, blue, pink, yellow) UV-coated single mode fiber, It was also confirmed that this propagation blocking method works. However, in the case of the colored UV coat, the amplification factor of the electric signal amplifier 4 was made larger than that of the transparent UV coat single mode fiber.

In the first embodiment, the remote interlock connector is controlled to stop the output of the high-power fiber laser 1, but at the light output end of the high-power fiber laser 1. An externally controlled attenuator and optical switch are arranged, and the externally controlled attenuator and optical switch are controlled by the signal from the discriminator 5 to reduce the light intensity of the high intensity light that is the cause of the FF, and the FF propagation The prevention was carried out promptly.

In the second embodiment, as shown in FIG. 4, the connector 7 and the optical fiber 9 in the FF detection are integrated with the optical receiver 3 used in the first embodiment to create the FF detection component 8. By making the shape like the FF detection component 8, it is possible to easily prevent propagation by connecting the FF detection component 8 to the output end of the light source that generates high output light. The FF detection optical fiber 9 used was a single mode fiber from which the UV coating was removed, and the connector 7 was an SC type. This FF detection component 8 was replaced with the optical receiver 3 of Example 1, and the FF generated by the light intensity of 3 W was detected, and the FF propagation prevention could be carried out promptly.

In the first and second embodiments, a delay time (˜ms) from when the optical receiver 3 or the FF detection component 8 generates FF until the remote interlock connector of the high-power fiber laser 1 is controlled is generated. As a result, destruction of the optical fiber due to the FF phenomenon proceeds. For this reason, it is necessary to add an optical fiber corresponding to the control delay time between the FF detection component 8 and the portion to be protected from the FF phenomenon to protect the portion to be protected from the FF phenomenon, and the FF propagation speed is about. In the case of 5 ms, by adding an optical fiber of about several meters, it was possible to protect the portion that was desired to be protected from the FF phenomenon.

Further, instead of adding an optical fiber corresponding to the control delay time, the structure of the FF detection component 8 described in the second embodiment, as shown in FIG. 5, is an FF detection having a core expansion part or a hole assist structure part. By using the inner optical fiber 10, after detecting the FF with the light receiver 3, the FF propagation is promptly performed in the core expanding portion or the hole assist structure portion of the FF detection inner optical fiber 10 having the core expanding portion or the hole assist structure portion. You can stop. In this example, by setting the core diameter of the core expansion portion to 25 μm, the FF generated by the light intensity of 3 W could be prevented from propagating in the core expansion portion.

In addition, although FF propagation can be stopped in the core expansion part or the hole assist structure part, if high-intensity light continues to enter the stopped part, the coating of the optical fiber is burned by the scattered light from the part where the FF stopped. For this reason, the coating of the optical fiber in the vicinity of the core expansion part or the hole assist structure part can be removed, taking into consideration the safety of the eyes, and covering with a flame-retardant material together to solve the problem of combustion and safety It was.

The core expansion portion or the hole assist structure portion for stopping the FF propagation in the FF detection component 8 configured using the optical fiber 10 within the FF detection having the core expansion portion or the hole assist structure portion described in the third embodiment. A light receiver 11 for observing scattered light from the light is disposed. By inputting the electric signal from the optical receiver 11 to the discriminator through an electric signal amplifier (which may be unnecessary) as in the optical receiver 3, it is possible to reconfirm that an FF has occurred. Become. Since the wavelength of the fiber laser 1 used to generate the FF this time is 1550 nm, the optical receiver 11 uses an InGaAs optical receiver, and the FF generation monitored by the optical receiver 3 is generated from the optical receiver 11. It was confirmed from the monitor signal, and the detection reliability was further improved.

DESCRIPTION OF SYMBOLS 1 High power light source 2 Optical fiber 3 Optical receiver 4 Electric signal amplifier 5 Discriminator 6 Interface for notification to the outside 7 Connector 8 FF detection component 9 Optical fiber in FF detection 10 FF with core expansion part or hall assist structure part In-detection optical fiber 11 Optical receiver

Claims (9)

A visible light emitted when forming the optical fiber fuse is monitored by an optical receiver disposed on the side surface of the optical fiber, and a light source that generates the optical fiber fuse using the detected optical fiber fuse generation signal from the monitor is provided. Stop fiber fuse propagation stopping method. A fiber fuse detector with an optical receiver on the side of an optical fiber that can be connected to the optical connector at both ends. 3. The fiber fuse propagation blocking method according to claim 1, or the fiber fuse detection component according to claim 2, wherein a silicon-based photodiode is used as the optical receiver. The fiber fuse propagation blocking method according to claim 1 or the fiber fuse according to claim 2, wherein the optical fiber coating observed by the optical receiver uses an optical fiber from which UV coating or UV coating is removed. Detection component. 2. An optical fiber having a length in consideration of a delay time from the position observed by the optical receiver to the stop of the fiber fuse is inserted in order to protect a portion to be protected from the fiber fuse. Fiber fuse propagation prevention method described in 1. 2. The fiber fuse propagation blocking method according to claim 1, wherein the optical fiber observed by the optical receiver includes a fiber structure of a core expansion portion or a hole assist structure portion. An optical receiver is disposed on the side of an optical fiber whose both ends can be connected to an optical connector, and in the fiber fuse detection part, a part of the optical fiber whose both ends can be connected to the optical connector is a fiber of a core expansion portion or a hole assist structure portion. The fiber fuse detection component according to claim 2, further comprising a structure. The fiber fuse propagation prevention according to claim 6, wherein the vicinity of the core expansion portion or the hole assist structure portion of the optical fiber having the fiber structure of the core expansion portion or the hole assist structure portion has a flame-retardant structure. Or a fiber fuse detection component according to claim 7. The optical receiver for monitoring scattered light is disposed in the vicinity of the core expansion portion or the hole assist structure portion of the optical fiber having the fiber structure of the core expansion portion or the hole assist structure portion. The fiber fuse propagation blocking method according to claim 6, or the fiber fuse detection component according to claim 7.