JPH11266201A - Method and device for transmitted optical communication by two fiber type bidirectional ring equipped with low priority order traffic automatic protection and management - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect preferential communication, when damage or a failure occurs by constructing an optical communication network with internal and external optical fiber links whose the carrier directions are reverse, termination communication channels of their 1st and 2nd parts, a detection circuit and plural light switches. SOLUTION: When a failure occurs, light switches 131 to 134 on nodes A/B are energized, and optical entrances of receivers RX1 and optical exits of transmitters TX1 are disconnected from use ring paths and are connected to complementary paths. Receivers RX2 and transmitters TX2 are disconnected from a communication network. The node A transmitter TX1 redetermines its direction to the node A communication device TX2 and transmits it up to the node B transmitter RX2 along an external fiber 110 via a generic node Y. The node B transmitter TX1 redetermines its direction to the node B transmitter TX2, so as to transmit it up to the node A receiver RX2 on an internal fiber 120, and the receivers RX2 redetermine their direction to the receivers RX1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to a closed ring transparent optical communication network that provides protection of principal communication channels of each supported wavelength and management of low priority traffic. About.

[0002]

BACKGROUND OF THE INVENTION A major challenge in fiber optic communications between various points is to address potential damage to transmission means and / or parts of communications equipment, for example, It is to ensure adequate protection that does not rely on elements external to the communication network, such as centralized management, and that allows maximum simultaneous use of the transmission bandwidth. Furthermore, it is necessary that a communication failure between two nodes (breakdown) does not cause a communication failure between the other nodes of the network.

The prior art has attempted to address these issues in various ways. For example, EP 0 729 247 describes a synchronous bi-directional ring network with optical fibers, wherein each fiber of the ring handles two signals having different wavelengths. For example, a signal at a wavelength of 1310 nm is used as an operation signal, and a signal at 1550 nm is used as a reserve signal. The network is such that in fault free conditions, a first wavelength can be used for switching between network elements, while at the same time a second wavelength can be used to maximize transmission capacity. Is configured. During the fault condition, the second wavelength is used.

In another example, European Patent No. 06779
No. 35 discloses a communication network including a number of stations S1 to S3. These stations are located two lines above the transmission line LT or the main loop arc.
It is distributed around a closed optical loop 30 having two access nodes N1, N2. Information from these two nodes is carried on different wavelengths. This loop also includes an emergency optical fiber 31 and is protected against any node failure. For data reception, the station may use one of the two wavelengths on the normal loop, or if the other is faulty,
Select an emergency loop.

[0005] EP 0 798 659 describes that
Transparent self-healing ring
ring) optical communication networks are disclosed. This network consists of two optical communication lines coupled to at least two optical signal add / drop nodes. In this network, at least one of the add / drop nodes can selectively drop optical signals from one of the lines, and can also simultaneously input at least one optical signal to each of the lines. .

[0006] In the prior art, inter alia, ITU-T Recommendation G. In 803, various protection schemes, especially path protection, multiplex section protection (MSP), multiplex section dedicated protection ring (MS-DP)
RING), a multiplex section shared protection ring (MS-SPRING).

Path protection applies only to unidirectional rings and consists of duplicating transmissions on the working and protection branches and providing a switch only at the receiver. Thus, there is a single-ended operation where a single node performs protection and does not have an APS (Automatic Protection Switch) protocol. Path protection is also defined as sub-network connection protection.

Multiplex section protection (MS
P) is based on fault detection at the multiplex section level. It features two or more parallel multiplex sections, one used for protection. This has dual-ended operation, since communication between the two nodes is required for communication on the protection line using the APS protocol at the end of the failure.

The multiplex section dedicated protection ring (MS-DPRING) is a unidirectional ring with 1 + 1 protection. Under a failure condition, the entire data stream is looped to the protection channel by the two nodes on each side of the failure. The operation of this type of ring class is always dual-ended. S
At the DH level, the APS protocol is required.

A multiplex section shared protection ring (MS-SPRING) is a bidirectional ring, with half of the capacity of the inner and outer rings reserved for protection. This capacity can be shared by multiple links, thereby increasing network throughput. However, this system uses TD
It can only be used for M multiplexing, not for WDM multiplexing.

[0011] The inventors of the present application provide a principal
When there is a breakdown or degradation in the channel, there is no need to transmit at different wavelengths, without central control and without any electrical-to-optical conversion of the communication channel, temporary or backup. The need for a WDM optical communication network to determine the direction of the fundamental channel to channel has been discovered.

[0012] Under fault-free conditions, the inventors also transmit and receive priority signals via a first communication arc of the network at a particular wavelength, and further communicate at the same wavelength. It has been discovered that an optical communication network can be configured to utilize 100% of its communication capacity by transmitting and receiving ad hoc traffic via a second communication arc of the network.

[0013]

SUMMARY OF THE INVENTION Accordingly, the present invention can generally be used for communication between multiple sites when large communication capacities are required. Further, the present invention provides a mechanism for protecting preferential communication in the event of damage or failure. By managing occasional channels, the transmission capacity can be increased by 100 over the entire operating time when there is no damage to the network.
% Can be used. If the priority channel has a failure or degradation, the priority traffic will
Redirected to a preliminary channel (redirected).

Accordingly, the present invention provides a two-fiber bi-directional ring with temporary automatic traffic protection and management that substantially obviates one or more of the limitations and disadvantages of the prior art arrangements described above. A method and apparatus for providing a transparent optical communication network having The objects and advantages of the invention can be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

To achieve these and other objects and advantages, and in accordance with the objects of the present invention, which are embodied and broadly described in this application, the present invention provides a method for bi-directionally transmitting optical signals of multiple wavelengths. An optical communication network capable of carrying a plurality of wavelengths in a first direction and a plurality of wavelengths in a second direction opposite to the first direction. An external fiber optic link that can be transported to at least a first of the plurality.
A first communication channel for the wavelengths of
A first communication channel terminated by two nodes, and a second communication channel for a first wavelength, comprising second portions of internal and external fiber optic links, wherein Second terminated by node
Communication channel, a detection circuit for determining deterioration in the first communication channel, and a first
And a plurality of optical switches for re-determining the direction of communication at the first wavelength from the first communication channel to the second communication channel upon detection of deterioration in the communication channel of the optical communication network. Is done.

In another aspect, the invention is a method of correcting a failure of a fiber optic link in an optical communication network, the method comprising at least two fiber optic links capable of carrying multiple wavelengths of light. Providing a link; forming at least two optical communication channels for at least a first wavelength of the plurality from the fiber optic link; and degrading transmission quality in any of the optical channels. Detecting; activating the optical switch to switch transmission of the first wavelength from the channel where the degradation is detected to another channel;
It is a method including.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention. Has a role to explain.

Reference will now be made in detail to the presently preferred embodiment of the present invention, an example of which is illustrated in the accompanying drawings.
Wherever possible, the same reference numbers are used throughout FIGS. 1 and 2 to refer to the same or similar parts.

According to the present invention, two different sending and transmitting connecting two nodes by the following disjunct paths realized by the ring architecture of this network:
By using each wavelength of communication between two nodes to allocate channels (basic and temporary)
It is possible to make full use of the transmission capacity of the two optical fibers with the outer and inner rings of the communication network. Under normal operating conditions, the communication between the two nodes can take place on both channels, while on the other hand, under basic channel failure or degradation, on the basic channel. Is normally re-directed (redirected) on a temporary channel path. Due to such redirection, communication on the temporary channel is interrupted for the duration of its failure or degradation.

According to the invention, the reconfiguration of the connections between the nodes takes place at the optical level, ie without the electro-optical conversion of the communication channel, resulting in a concentration between the nodes in question. There is no need for an efficient management or control communication system. Each channel assigned to one wavelength is independent of the other channels at different wavelengths, and the process of reconfiguring the connection between two nodes requires a communication state between the other nodes of the network. Has no effect. Protection of the channel is thus achieved, while still guaranteeing a much higher transmission capacity during normal operation of the network.

FIG. 1 is a block diagram of a ring communication network according to the present invention. The communication network 100
Preferably, it comprises two optical fibers interconnecting the various nodes. As shown, the two optical fibers are an outer fiber 110 and an inner fiber 120. The data flows exchanged between the various nodes traverse the communication network 100 over the two optical fibers 110 and 120 in opposite directions. In the case of an optical network, nodes A and B, which are a generic pair in network 100, have appropriate WDMs as carriers.
Two-way communication is performed using one wavelength of a comb. That wavelength cannot be shared for transmission by other nodes of the network 100. Tapping and detection of that wavelength by other nodes (broadcast transmission mode) is possible, but protection against failure is not guaranteed.

According to the present invention, an arc transmission path is used for data exchange on the external optical fiber 110 from a first node A to a second node B. The same route,
For data exchange from the second node B to the first node A,
Used in the opposite direction on the internal optical fiber 120. In this way, bidirectional communication between nodes A and B is achieved by using only a portion of communication ring 100 or an arc. A path or arc that is complementary to that described above can be used as a second bidirectional communication path between nodes A and B using the same wavelength as the channel above. This makes it possible to use 100% of the transmission capacity of the network 100.

An optical amplifier can be provided between the nodes to compensate for attenuation along fibers 110,120.

More specifically, according to the present invention, node A
And node B communicate in network 100 at wavelength λ1, such that a first two-way communication channel is provided between node A transmitter TX1 and node B receiver RX1 and generically. And vice versa via a simple node X. Similarly, a second bi-directional communication channel is implemented between the transmitter TX2 of node A and the receiver RX2 of node B, and vice versa via the generic node Y, also at wavelength λ1. Is done.

Nodes A and B are optically transparent at inappropriate wavelengths dedicated to communication between other nodes. In the same manner, every other node of the communication network 100 has a wavelength λ1 that is dedicated to nodes A and B.
Is transparent. As shown in FIG. 1, solid arrows at nodes other than A and B indicate a normal path of a communication channel between those nodes. This transmission path is a communication network 100 under normal operating conditions.
To make full use of the transmission capacity of the In the broadcast transmission embodiment, nodes other than A and B are provided with wavelength selective taps, so that a small portion of the optical signal of wavelength λ1 can be extracted from the fibers 110 and / or 120.

According to the invention, the two bidirectional channels on node A (B) are defined separately. In particular, TX1
Channel "1" between and TX1 is preferably defined as the "basic" channel, and channel "2" between TX2 and RX2 is preferably "secondary", ie, extraordinary. Defined as a channel. Such a definition would use channel 1 to manage high priority traffic that requires full protection, while using channel 2 for low priority traffic management that does not require as much protection. It is assumed to be used.

The protection mechanism of the present invention shown in FIG.
If a failure or degradation occurs in the communication on channel 1, it consists of re-determining the traffic on channel 1 on the path normally used by channel 2. To achieve such redirection, traffic on channel 2 is interrupted. According to the invention, the communication network 100 comprises a plurality of optical switches 13 arranged between the communication terminals of nodes A and B.
1-134 and optical addition / dropout of waveguide (Ad
d / Drop) complex. These are used for direction re-determination and will be described in more detail below.

The basic channel 1 protection procedure according to the invention operates in the following manner and in a temporal sequence.
First, a failure in the communication path between node A and node B on channel 1 is received as no optical signal entering receiver RX1, or as a degradation of that optical signal. The failure is caused, for example, by breakage of an optical fiber or a failure in an optical amplifier. Next, node A
(B) The appropriate control logic is the optical switch 131-1
34, the optical entrance of the receiver RX1 and the transmitter T
Disconnect the optical exit of X1 from the ring path used and connect them to the complementary path. By the same operation, the receiver RX2 and the transmitter TX2 are disconnected from the communication network 100. If this failure involves only one of the two directions of propagation of the basic bidirectional channel 1, node A suffering the failure on the receive path
Before the operation of (B) operates, the above-described operation causes the node B to operate.
The absence of the optical signal condition on receiver RX1 in (A) is enforced. This, in turn, triggers the above-described protection mechanism. The basic channel 1 uses the complementary network previously used by the secondary channel in both directions of propagation. Lower priority traffic is lost until the situation returns to normal.

In FIG. 1, the dashed arrow between nodes A and B indicates the direction of basic channel 1 after the reconfiguration of network 100 following a failure in channel 1 or degradation of channel 1 has been detected. Represents a route. As shown in FIG. 1, the transmitter TX1 at node A is re-directed to the transmitter TX2 at node A and along the external fiber 110 via a generic node Y via node B
To the receiver RX2. Similarly, Node B
TX1 is re-directed to the transmitter TX2 of Node B so that it is transmitted over the internal fiber 120 to the receiver RX2 of Node A, and the receiver RX2 is
The direction is re-determined to 1. In this manner, the fundamental channel is typically transmitted on the left arc of network 100, but instead is transmitted on the right arc, which is typically used for extra traffic. You.

FIG. 2 is a more detailed block diagram of the communication network shown in FIG. In particular, FIG. 2 illustrates, by way of example, a more detailed configuration of node A shown in FIG. 1 for a four-wavelength WDM ring network. However, different numbers of wavelengths, for example 8, 16, 32, etc., can be used. If necessary, those skilled in the art can obviously modify the embodiments described herein and use many other wavelengths than four. Node B is preferably configured similarly to node A. As shown in FIG. 2, the outer fiber 110 and the inner fiber 120 each carry four wavelengths λ1, λ2, λ3, λ4. Thus, in this configuration, eight bidirectional links can be provided between the eight nodes. Half of the capacity of the network is used for basic traffic and the other half of the network is used for extra traffic.

As shown in FIG. 2, optical signals enter node A from either internal fiber 120 or external fiber 110 of communication network 100.
The signal on either the outer fiber 110 or the inner fiber 120 is split by a wave division mux (wave division mux).
ltiplexing = WDM) Demultiplex unit 21
1, 212. The demultiplex units 211 and 212 separate the wavelengths and output the selected wavelength λ1 to the optical switch 132. According to the present invention,
Each of the optical switches 131 and 132 is a JDS FITEL
Equipped with devices such as SW22B4-20FP optical switching module.

A demultiplex operation is performed to separate different wavelengths or different wavelength groups along different paths. Thus, as shown in FIG. 2, λ1 on the internal fiber 120 is equal to the demultiplex unit 211
To the receiver RX2, while the external fiber 1
Λ1 on 10 is input from the demultiplex unit 212 via the optical switch 132 to the receiver RX1.

A filtering operation is performed to remove excess noise before the signal is input to the detection circuit described below. If an optical amplifier is provided in the ring network, the level of ASE generated in the optical amplifier can be kept low by filtering. A filter is provided at the output of the demultiplex units 211, 212 along each of the optical paths. However, in the preferred embodiment, the filtering function is provided directly by the demultiplex units 211,212 and / or the multiplex units 213,214. In accordance with the present invention, the demultiplex units 211, 212 each comprise a device such as a Pirelli 4WS demultiplex unit. In another example, the demultiplex units 211, 212 are arrayed waveguide (AWG) devices.

The wavelengths on the internal and external fibers 120 and 110, where nodes A and B are not provided, ie, wavelengths other than λ1, are transmitted directly to the WDM multiplex units 213, 214 of the corresponding path. Multiplex units 213 and 214 are
The signal is reconstructed from the component wavelengths. According to the present invention, the multiplex units 213 and 214 each comprise a device such as a Pirelli 4WM multiplex unit as well as an AWG device.

The transmitters TX1 and TX2 of the node A are:
Each is connected to a transponder 215 and 216 that provides a conversion of the wavelengths emitted by TX1 and TX2 to a wavelength λ1 managed by node A. According to the invention, the transponders 215, 216 each comprise a device such as a Pirelli TXT / EM transponder unit.

The outputs of the transponders 215 and 216 are
The switch 131 is connected to the transmission optical switch 131.
Are connected to the multiplex units 213 and 214, respectively. Multiplex unit 2
The WDM-multiplexed optical signals output from the 13, 214 are prior to being reintroduced into the communication network,
The light is amplified by the optical amplifiers 213 and 214, respectively.
According to the present invention, the optical amplifiers 217 and 218 each include a device such as a Pirelli OLA / E-MW optical line amplifier.

As shown in FIG. 2, the receiving optical switch 132 allows the receiver RX1 of the basic channel to be connected to the WDM demultiplex units 211 and 212 of the external or internal paths 110 and 120, respectively. Be connected as possible. Transmission optical switch 131
Means that the transmitter TX1 of the basic channel is connected to the WDM multiplex unit 21 of the external or internal path 110, 120.
4 and 213, respectively.

The absence or degradation of the signal transmitted along the fundamental channel is for example by a detection circuit comprising a splitter 222 withdrawing a fraction of the received optical power, which is less than 5%. Can be detected. The output of the splitter is input to a photodiode 219 that determines an optical power level. The output of photodiode 219 is an electrical signal coupled to threshold detector 220, which
The output of 20 is coupled to control logic 221.
When necessary, the control logic 221 outputs an electric switch drive signal indicated by a broken line to the optical switches 131 and 132 to perform reconfiguration. The detection circuit including the splitter 222, the photodiode 219, the threshold detector 228, and the control logic includes the optical switch 1
It can be provided on the same card that supports 31 and 132. Although not shown, a similar detection circuit may be used to detect a failure in communication on the internal fiber 120 or its degradation.

Also, or alternatively, according to the combination, the receiver RX1 detects a failure or deterioration of the received signal, for example a bit error rate (BER) of greater than 10 ^-8 , and controls the reception warning signal. It can be output to the logic 221. As described above, the control logic 221 then switches the switch drive signal to the optical switches 131 and 132
To reconfigure the transmission path of the basic channel.

In one example, a bidirectional ring according to the present invention
The network is linked by two spans of single mode optical fiber, each having a length of about 64 km, achieving a ring circumference of about 512 km8.
It has two nodes. In this example, each node provides 6 dB of attenuation to four signals of different wavelengths in the erbium amplification band. A total of 16 erbium-doped optical amplifiers (Pirelli OLA-MW) providing about 22 dB of gain are arranged at the output of each node, both on the inner and outer fiber rings. I have. 2.5Gb between node pairs
/ S (SDH-STM16) four unprotected bidirectional links are thus provided.

In another embodiment of the present invention, the transmission optical switch 131 is located between the transmitters TX1 and TX2 of node A and the transponder units 215, 216, and during reconstruction, the basic channel is reserved. This makes it possible to use the transponder unit 216 of the channel. In this way, the transponder unit 215 of the basic channel can be protected. Thus, a failed transponder on the basic channel can be bypassed.

The system described above applies to WDM networks with any number of wavelengths and nodes, provided that optical power dynamics at the entrance to the receiver and optical amplifier are observed. It should be understood that it is possible. Further, the structure of the present invention does not limit generic nodes to the use of a single wavelength. It is clear from FIG. 2 that the receiver / transmitter RX
A second pair of 1 / TX1 and RX2 / TX2 connects to another extracted wavelength and has demultiplexed and multiplexed WDM with separate protection logic activated by a second pair of optical switches. The unit allows it to be reinserted into the network. Thus, it is possible to connect a single node to various additional nodes, and the bidirectional channels are always individually protected using different wavelengths for each channel.

Furthermore, the use of a secondary channel is not necessary for the correct functioning of the network, and if it does not exist or its communication path fails, the reconfiguration operation is Not done.

[0044] Other embodiments of the invention will be apparent to those skilled in the art from consideration of this application and practicing the invention disclosed herein. For example, the concepts taught herein are all applicable to electrical communication networks. In such a case, the photodiode and the optical signal splitter are replaced by a filter, and the optical switch becomes an electrical switch. The contents and examples of this application are to be considered only as illustrative, and the true scope and spirit of the present invention shall be defined by the appended claims.

[Brief description of the drawings]

FIG. 1 is a block diagram of a ring communication network according to the present invention.

FIG. 2 is a block diagram showing further details of the ring communication network shown in FIG.

 ──────────────────────────────────────────────────の Continuation of front page (71) Applicant 591011856 Pirelli Cavies System e. p. A

Claims (7)

[Claims] An optical communication network capable of bidirectionally carrying optical signals of a plurality of wavelengths, comprising: an internal optical fiber link capable of carrying the plurality of wavelengths in a first direction; An external fiber optic link capable of carrying the plurality of wavelengths in a second direction opposite the first direction; and a first communication channel for at least a first wavelength of the plurality. The internal and external optical fibers
A first communication channel comprising a first portion of a link and terminated by two nodes; and a second communication channel for the first wavelength,
A second communication channel comprising second portions of the internal and external fiber optic links and terminated by the two nodes; a detection circuit for determining degradation in the first communication channel; Activated by a detection circuit, upon detecting degradation in the first communication channel, re-determining a direction of communication at the first wavelength from the first communication channel to the second communication channel. An optical communication network, comprising: an optical switch. 2. The optical communication network according to claim 1, wherein the detection circuit comprises: an optical splitter capable of recovering a power signal from the first communication channel; and the power splitter coupled to the optical splitter; A photodiode capable of determining a level of a signal, a threshold detector coupled to the photodiode, and capable of determining a threshold level of the power signal, and a threshold detector coupled to the threshold detector; Control logic capable of outputting a switch drive signal to a selected one of the plurality of optical switches. 3. The optical communication network according to claim 1, wherein said first communication channel comprises a first transmitter / receiver pair within said first node and a second transmitter / receiver pair within said second node. An optical communication network comprising two transmitter / receiver pairs. 4. The optical communication network of claim 1, wherein the plurality of wavelengths on the internal fiber optic link are input to a first demultiplex unit and the plurality of wavelengths on the external fiber optic link. The plurality of wavelengths may be
An optical communication network characterized in that the optical communication network is input to a demultiplex unit. 5. The optical communication network according to claim 4, wherein said first and second demultiplex units extract said first wavelength and pass the rest of said plurality of wavelengths. Optical communication network. 6. The optical communication network of claim 1, wherein said internal and external optical fiber links comprise optical amplifiers. 7. A method for correcting a failure of a fiber optic link in an optical communication network, the method comprising: providing at least two fiber optic links capable of carrying a plurality of wavelengths of light; Forming, from a link, at least two optical communication channels for at least a first wavelength of the plurality; detecting a degradation in transmission quality on any of the optical channels; Switching the transmission at the first wavelength from a channel in which degradation is detected to another channel.