KR100573992B1 - Method and apparatus for detecting/switching failure of optical fiber - Google Patents

Abstract

The present invention automatically detects a line cut using a gain-controlled optical amplifier and a fiber diffraction grating, and based on the detection result, an optical line cut detection for automatically switching from an operating ring to an operating ring or from an alternate ring to an operating ring. And an automatic switching technique. To this end, the present invention provides an optical fiber diffraction grating at a front end of each node to reflect a laser beam inserted into a gain-controlled optical signal, and to detect the laser beam being reflected. To detect the cutting of the optical line, and based on the detection result, the protection in the optical layer that automatically switches the optical signal from the operating ring to the switching ring or from the switching ring to the operating ring (i.e., protection / switching in the optical layer). By realizing the switching, it is possible to effectively prevent the deterioration of the transmission quality of the traffic due to the optical fiber cutting.

Description

METHOD AND APPARATUS FOR DETECTING / SWITCHING FAILURE OF OPTICAL FIBER}

1 is a block diagram of an optical line cutting detection and automatic switching device according to an embodiment of the present invention,

FIG. 2 is a conceptual diagram illustrating a process of protecting / switching an optical signal when cutting an optical line in a self-healing annular network structure; FIG.

3 is a graph showing the output spectrum of a gain controlled optical amplifier,

4 is a block diagram of a typical conventional optical branch coupling device that is a node element in a self-healing annular network structure.

<Description of the code | symbol about the principal part of drawing>

100, 200: optical branch coupling device 102, 116, 202, 216: demultiplexer

104, 118, 204, 218: multiplexer 106, 206: gain controlled optical amplifier

108, 208: optical switch 110, 210: optical coupler

112, 212: controller 112 / a, 212 / a: photodetector

112 / b, 212 / b: optical switch controller 114, 214: optical fiber diffraction grating

140: operation ring 150: protection ring

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting and switching a break in an optical line in a WDM-SHR (Wavelength Division Multiplexing Healing Ring). More specifically, a gain controlled optical amplifier The present invention relates to a method and apparatus for detecting and cutting an optical line, which is suitable for detecting an optical line cut in a ring network structure using a gain-clamping EDFA and automatically switching from an operating ring to a protective ring.

Recently, optical transmission using wavelength division multiplexing (WDM) has been developed into a self-healing ring structure using an optical branch coupling device. In the ring-type network adopting the conventional synchronous transmission device, the traffic protection / switching is performed by unidirectional path switching R (UPSR) or bidirectional line switching for each of two or four optical fibers. There is a method of switching (BLSR).

In the conventional WDM-SHR structure, in order to implement switching in the optical layer, the optical power of the operating ring and the backup ring is monitored to monitor line accidents such as cutting of the optical cable, and when the accident occurs, the service is automatically switched from the operating ring to the backup ring. The method of sustaining was used.

That is, in the WDM self-healing annular network, the structure of each node is, for example, a multiplex that multiplexes the front end of the demultiplexer 404 and the demultiplexed channel which demultiplexes by inputting the multiplexed channel as shown in FIG. 4A. A structure having optical amplifiers 402 and 408 at the rear end of the firearm 406 or the front end of the demultiplexer 404 of the multiplexer as shown in FIG. The optical amplifier 408 is provided only at the rear end. 4A and 4B, reference numeral 404a denotes a channel passing through a node, 404b denotes a channel branching from a node, and 406a denotes a channel coupled to the node.

On the other hand, the branch coupling of the optical signal at each node means a change in the number of channels, the change in the number of channels means a change in the intensity of the optical signal input to the optical amplifier. Thus, in the conventional method, the saturation state variation in the optical amplifier may be induced, which may cause a serious loss in the transmission of the optical signal.

Accordingly, the present invention is to solve the above problems of the prior art, the automatic detection of the line cut by using the gain-controlled optical amplifier and the optical fiber diffraction grating, and switching or switching ring in the operating ring based on the detection result The purpose of the present invention is to provide an optical line cutting detection and automatic transfer method and apparatus that can be automatically transferred to an operation ring in the.

The present invention according to the consistent point to achieve the above object, the optical line cutting detection and automatic switching method for detecting the optical line cutting between each adjacent node, and performing the protection / switching between the adjacent nodes based on the detection result A method comprising: delivering a gain control amplified multiplexed signal at an arbitrary node to an adjacent node through an operating ring; Reflecting a specific wavelength of the multiplexed signal through a reflector provided at the adjacent node and transmitting the reflected wavelength to the arbitrary node; And detecting the reflected optical signal in the specific wavelength band, and when the detected optical signal falls below a preset threshold, it is determined that the optical preference is cut between the arbitrary node and the adjacent node and is output from the arbitrary node. It provides an optical line cutting detection and automatic switching method consisting of bypassing a multiplexed signal through a switching ring and transferring the multiplexed signal to the adjacent node.

The present invention according to another aspect to achieve the above object, the optical line cut detection and automatic switching device for detecting the optical line cut between each adjacent node, and performing the protection / switching between the adjacent nodes based on the detection result Wherein each node comprises: first branching / coupling means for branching / coupling a multiplexed input optical signal; Gain controlled optical amplifying means for gain control amplifying the branched / coupled multiplexed signal; An optical switch for switching the output of the gain control amplified multiplexed signal to a normal contact or bypass contact; Optical coupling means for transmitting the multiplexed signal transmitted from the normal contact point of the optical switch to an adjacent node through an operation ring, and combining a specific wavelength signal reflected from the reflector in the adjacent node; Detects the reflected specific wavelength signal provided from the optical coupling means, and detects the optical line cutting between two adjacent nodes through comparison between the detected specific wavelength signal and a predetermined threshold value for contact switching of the optical switch. Switching control means for generating a switching control signal; A reflector for passing only a data channel of a gain control amplified multiplexed signal transmitted through a bypass contact of the optical switch when an optical line break between any node and an adjacent adjacent node is detected; And a second branching / coupling means for branching / coupling the data channel transmitted from the reflector and transferring the data channel to the input of the adjacent node through the switching ring.

The above and other objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, a key technical aspect of the present invention is to insert an optical fiber diffraction grating in front of each node to reflect the laser wavelength inserted into the gain-controlled optical signal, and based on the detected laser wavelength detection, In the present invention through such technical means by detecting the cutting, the automatic switching of the optical signal from the operating ring to the switching ring or the switching ring to the operating ring (that is, the protection / transfer in the optical layer) based on the detection result. It is easy to achieve the purpose.

1 is a block diagram of an optical line cutting detection and automatic switching device according to a preferred embodiment of the present invention.

Referring to FIG. 1, in the present embodiment, only two optical branch coupling devices (ie, nodes) 100 and 200 connected by the operation ring 140 and the protection ring 150 are provided for the convenience of explanation and the understanding. Although shown, in practice, a gain-controlled optical amplifier (EDFA: erbium-doped fiber amplifier) may be used to decorate a plurality of nodes regardless of the number of channels that are branched.

That is, each optical branch coupling device, such as optical branch coupling device 100, has two demultiplexers 102, 116, two multiplexers 104, 118, a gain controlled optical amplifier 106, optical A switch 108, an optical coupler 110, a controller 112, and an optical fiber diffraction grating 114, the controller 112 including an optical detector 112 / a and an optical switch controller 112 / b. .

Here, the optical signal transmission path (that is, the optical signal transmission path in the optical branch coupling device 100) in the steady state (when no optical line cutting has occurred) is performed by the first demultiplexer 102 → the first multiplexing. The firearm 104 → the gain controlled optical amplifier 106 → the contact ab of the optical switch 108 → the optical coupler 110, where the optical signal output through this path is passed through the operating ring 140 to the next stage. It is delivered to the optical fiber coupling device 200.

That is, the multiplexed optical signal coming into the input A side is branched / combined through the first demultiplexer 102 and the first multiplexer 104, and then input to the gain-controlled optical amplifier 106 to have a predetermined level. Is amplified. At this time, in the spectrum of the amplified multiplexed signal output from the gain-controlled optical amplifier 106, as shown in FIG. 2 as an example, the raised channel LW1 having a specific wavelength in addition to the input data channel DC or LW2) appears to keep the gain of the optical amplifier constant.

Subsequently, the amplified multiplexed signal (i.e., the multiplexed signal having the raised channel and the data channel) is output through the contact ab of the optical switch 108, the optical combiner 110, and passes through the path through the operation ring 140. The optical splitter coupling device 200 is transmitted to an adjacent optical branch coupling device 200, and in the adjacent optical branch coupling device 200, the multiplexed optical signal is contacted to the optical switch 208 ab → optical fiber diffraction grating 214 → second demultiplexer 216. ? Is passed to the next node not shown via the second multiplexer 218.

On the other hand, the optical fiber diffraction gratings 114 and 214 have reflection characteristics with respect to the gain control amplified laser wavelength. Accordingly, the data channel DC of the multiplexed channel information transmitted through the contact ab of the optical switch 208 passes through the optical fiber diffraction grating 214 as it is, but the raised channel LW1 or LW2 is reflected to reflect the optical switch ( The contact ba and the operating ring 140 of 208 return to the adjacent optical branch coupling device 100.

Next, the raised wavelength returned through the operating ring 140 is transmitted to the controller 112 through the optical coupler 110, and the photodetector 112 / a in the controller 112 receives the raised wavelength. Detect. Therefore, since the light intensity above the predetermined threshold value is detected through the photo detector 112 / a, the optical switch 112 / a turns off the contact state according to the control from the optical switch controller 112 / b. cd). Here, the threshold is set higher than the weak signal detected by the photo detector when the optical line is cut (that is, the weak signal reflected from the broken cross section when the optical line is broken).

On the other hand, the optical signal transmission path (the optical signal transmission path in the optical fiber coupling device 100) at the time of defect occurrence (i.e., cutting the optical line) is obtained by the first demultiplexer 102 → the first multiplexer 104 → the gain. Controlled optical amplifier 106 → contact ac of optical switch 108 → optical fiber diffraction grating 114 → second demultiplexer 116 → second multiplexer 118, the light output through this path The signal is transmitted to the input D of the optical fiber coupling device 200 via an optical fiber (eg, switching) or other nodes, not shown in FIG. 1.

That is, when the optical path is cut, even if the gain control amplified multiplexed signal is transmitted from the optical coupler 110 to the adjacent node (optical branch coupling device 200) through the operation ring 140, the optical path is adjacent. The raised wavelength reflected from the optical fiber diffraction grating 214 of the node does not return to the optical fiber diffraction grating 100, and only a weak optical signal is detected at the photodetector 112 / a.

That is, the photo detector 112 / a in the controller 112 is reflected by the optical fiber diffraction grating 214 in the adjacent optical fiber coupling device 200, and then the raised wavelength (or channel) transmitted through the optical coupler 110. ), The light detection signal is used to check whether the optical line is cut. That is, the optical switch controller 112 / b in the controller 112 switches the contacts of the optical switch 108 in the bar state (ab, cd) or cross state in response to the light detection signal provided from the photo detector 112 / a. Switching to (ac, bd), the switching is controlled to maintain the bar state when the detected optical signal (raised wavelength) is above the preset threshold and to maintain the cross state when the detected optical signal is below the preset threshold. .

Thus, when the optical line is cut, the contacts of the optical switch 108 are switched to the cross state, i.e., the ac and cd states, under the control of the optical switch controller 112 / b, resulting in a gain controlled optical amplifier 106. The amplified multiplexed signal is output through the branching / combining process via the contact ac → optical fiber diffraction grating 114 → second demultiplexer 116 → second multiplexer 118 of the optical switch 108. do.

At this time, when the operating ring is cut, since the operating ring and the protection ring are sealed in one cable, the protection ring is also cut at the same time. As a result, the optical switch 208 in the optical branch coupling device 200 through the same process as described above. The contact is switched from the bar state (ab, cd) to the cross state (ac, bd) under the control of the optical switch controller 212 / b.

Next, the amplified multiplexed signal output from the second multiplexer 118 of the optical branch coupling device 100 is transferred to the input D of the optical branch coupling device 200 through a switching ring or another node, not shown. do.

That is, referring to FIG. 3 as an example, assuming that node n1 is the optical branch coupling device 100 of FIG. 1 and node n2 is the optical branch coupling device 200 of FIG. When the optical line is not cut between n1) and node n2, the amplified multiplexed signal output from node n1 is transmitted to node n3 through node n2 along path 306 indicated by a solid arrow. When the optical path is cut between node n1 and node n2, the amplified multiplexed signal output from node n1 is transferred to a switching ring formed along a path 308 indicated by a dotted arrow (or switching including other nodes). Pass along the ring) and pass through node n2 to node n3. In Fig. 3, reference numeral 302 denotes an operation ring, and 304 denotes a protection ring.

Next, the multiplexed optical signal coming through the input D is branched / combined via the first demultiplexer 202 and the first multiplexer 204 and then input to the gain controlled optical amplifier 206. The multiplexed signal, which is amplified to a predetermined level, is not shown via the contact db → optical fiber diffraction grating 214 → second demultiplexer 216 → second multiplexer 218 of the optical switch 208. It is delivered to the next node, for example node n3 of FIG.

Therefore, according to the present invention, even when the optical path between the adjacent nodes is cut, traffic transmission between adjacent nodes is possible through the bypassing path, that is, economical protection switching at the optical layer in the event of a line failure, thereby reducing traffic quality. Can be effectively prevented.

Also, in the present invention, since the protection / switching is implemented in the optical layer, unlike the SONET signal, protection / switching without additional devices is required when accommodating IP traffic or sub-signals such as PDH, which do not have a protection / switching function in the optical splitter coupling device. Is easy to implement.

As described above, according to the present invention, an optical fiber diffraction grating is inserted at the front end of each node to reflect the laser wavelength inserted into the gain-controlled optical signal, and the optical line is cut based on the detected laser wavelength detection. By detecting and by the detection result, by realizing the protection / switching in the optical layer to automatically switch the optical signal (that is, the protection / transfer in the optical layer) from the operating ring to the switching ring or the switching ring to the operating ring, It is possible to effectively prevent the transmission quality degradation of traffic due to the optical fiber cut.

Claims (6)

In the optical line cut detection and automatic transfer method for detecting the optical line cut between adjacent nodes, and performing the protection / switching between adjacent nodes based on the detection result, Transferring the gain control amplified multiplexed signal at an arbitrary node to an adjacent node through an operation ring; Reflecting a specific wavelength of the multiplexed signal through a reflector provided in the adjacent node and transmitting the reflected wavelength to the arbitrary node; And Multiplexing output from the arbitrary node by detecting the optical signal reflected in the specific wavelength band and determining that the optical preference is cut between the arbitrary node and the adjacent node when the detected optical signal falls below a preset threshold The optical line cutting detection and automatic switching method comprising the step of bypassing the signal through the switching ring to the adjacent node. The optical line break detection and automatic switching method of claim 1, wherein the reflected specific wavelength is a laser wavelength on a gain control amplified multiplexed signal. The optical line cutting detection and automatic switching method of claim 2, wherein the reflector is an optical fiber diffraction grating. In the optical line cutting detection and automatic switching device which detects the optical line cutting between adjacent nodes, and performs the protection / switching between the adjacent nodes based on the detection result, Each of these nodes is: First branching / coupling means for branching / coupling the multiplexed input optical signal; Gain controlled optical amplifying means for gain control amplifying the branched / coupled multiplexed signal; An optical switch for switching the output of the gain control amplified multiplexed signal to a normal contact or bypass contact; Optical coupling means for transmitting the multiplexed signal transmitted from the normal contact point of the optical switch to an adjacent node through an operation ring, and combining a specific wavelength signal reflected from the reflector in the adjacent node; Detects the reflected specific wavelength signal provided from the optical coupling means, and detects the optical line cutting between two adjacent nodes through comparison between the detected specific wavelength signal and a predetermined threshold value for contact switching of the optical switch. Switching control means for generating a switching control signal; A reflector for passing only a data channel of a gain control amplified multiplexed signal transmitted through a bypass contact of the optical switch when an optical line break between any node and an adjacent adjacent node is detected; And And a second branch / coupling means for branching / coupling the data channel transmitted from the reflector and transferring the data channel to the input of the adjacent node through the switching ring. 5. The apparatus of claim 4, wherein the reflected specific wavelength signal is a raised wavelength carried in a gain control amplified multiplexed signal. The optical line cutting detection and automatic switching device according to claim 5, wherein the reflector is an optical fiber diffraction grating.

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