JP2002527990A - Unidirectional optical ring network - Google Patents

Abstract

(57) [Summary] In an optical unidirectional ring network having a plurality of network nodes (NA to NN), a transmission channel (Λ _A ) having a transmission band used only once is assigned to each network node. The configuration of this network is performed via a switchable or adjustable receive filter (54).

Description

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a unidirectional optical ring network according to the preamble of claim 1.

For transmission of large data volumes, ring networks are known, in which bidirectional data is transmitted between various network nodes / terminals, either unidirectionally or mostly via two fibers.

“22nd European Conference on Optical Communication” -ECOC 96, Oslo, p
.3.51-3.54 to "colored section ring"
Are known, in which wavelengths used only once each for transmission between two network nodes are used. This makes it possible, in the event of a disturbance, to connect a spare connection with the same wavelength via the undisturbed part of the ring network.

In order to reconfigure the ring network, ie, to create a new logical connection, a change in wavelength is usually required.

In newly envisioned optical ring networks, data dropping and insertion should take place at the optical level and reconfiguration should be easily possible. A ring network including network nodes should also be implemented as cheaply as possible.

[0006] Such a ring network is defined in claim 1.

[0007] Advantageous embodiments of the ring network result from the dependent claims.

[0008] Unidirectional ring networks are especially cost-effective. This is because only one glass fiber is required for transmission, and the network node is simply configured. A fixed assignment of a given transmission channel or wavelength used in the ring network to the network node only once results in a unique assignment of the transmission channel, ie the transmitted data signal, to the network node. Since each network node receives the data signals of all other network nodes, any connection to the other network node can be made by selecting the corresponding receive filter. If a switchable or always tunable receive filter is selected, any connection can be made between all network nodes. Multiple filters also allow simultaneous connections to multiple network modes.

By using a coupler provided with a grating, a network node having a very simple structure can be obtained. This coupler has filter characteristics due to the grating.

If relatively high demands on the reliability of the transmission are presented, a second ring is provided for the backup circuit. In this second ring, data transmission takes place in the opposite direction.

An embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a unidirectional ring network, FIG. 2 shows a first embodiment of a network node, FIG. 3 shows an advantageous embodiment of this network node, and FIG. 4 has a spare transmission ring. It is a unidirectional ring network.

FIG. 1 shows a plurality of network nodes NA, NB, NC,. . . A unidirectional ring network with NN is shown. Transmission between arbitrary network nodes is performed in a wavelength division multiplexing mode via a glass fiber 1 and a plurality of transmission channels _{Ａ A} ~.
Made in lambda _N, the plurality of transmission channels lambda _A to [lambda] _N has a preset wavelength intervals. The transmission direction is indicated by an arrow.

FIG. 2 shows a basic circuit diagram of the network node NA. Network nodes are used for the realization of various connections that are always made via transmission channels. The data signal to be coupled out at this network node is called the "drop" signal, and the data signal to be transmitted is called the "insert" signal (add). Channels, also referred to as branching, conducting connections or insertions, refer to signals transmitted in this channel in a relatively narrow sense. Reference symbols having the same index are used for the transmission channel and the associated data signal. The data signal λ _A is transmitted on the associated transmission channel _{Ａ A.}

The network node reduced to the basic function of an Add-Drop-module includes a series circuit of an amplifier 4, an output coupling device 5 and an input coupling device 6. The input side 2 receives wavelength division multiplexed signals λ _{A to} λ _{N of} all data signals received via the transmission channels _{Ａ A to Ｎ N.} In each transmission channel (transmission band), only one signal is transmitted, or a plurality of individual signals are transmitted in the wavelength division multiplex mode or, of course, in the time division multiplex mode.

The received signal is first amplified and then reaches the output coupling device 5. The division of all data signal / transmission channels into two signal paths is first performed in a 1: 2 coupler (branch). All the transmission signals to be conductively connected except for the transmission channel _ＡA assigned to this network node via one signal path
/ The transmission channel is connected conductively. The transmission channel _{Ｄ D} via the other signal path
The data signal λ _{DROP of} the _ROP or the transmission channel ＤＲ _DROP , for example, the data signal λ _{B, DROP} is output-coupled.

The transmission channel Λ _DROP to be _dropped is selected by an output combiner, here configured as a wavelength separation filter. This wavelength separation filter is schematically illustrated here as a coupler 51 having a constant switchable or tunable bandpass filter 52 and a bandstop filter 53. Channel Λ _{D ROP} is the only channel in the passband of bandpass filter 52. This channel ＤＲ _DROP is transferred via the drop output 7 to, for example, a subscriber terminal.

Instead of the data signal / channel split off at this network node, the input coupling device 6 configured as a coupler in the transmission channel to which the corresponding data signal λ _{A, ADD} applied to the summing input 8 is assigned. Inserted. This presupposes that the signal λ _A (loop return signal) already transmitted from this network node A and received again at the input 2 via the ring must be blocked at the latest before the input coupling device 6. . For this purpose, a band-stop filter 53 is provided which is connected to the first signal path, and which is fixedly adjusted to a corresponding wavelength. The transmission of this signal can also be prevented at the network node MN, which is at the front, but this has the additional configuration cost of adding further network nodes.

The output side 3 outputs a wavelength division multiplexed signal. This wavelength division multiplex signal includes signals λ _{A, ADD} and λ _B to _N of all transmission channels.

By replacing, switching or adjusting the band-pass filter 52, each network node receives a corresponding transmission signal of each other network node. That is, a corresponding connection can be made. Therefore, a simple configuration change is possible.

FIG. 3 shows a special variant embodiment of the network node. An adjustable bandpass filter 54 is provided, and a coupler 61 having a grating 62 is used as the input coupling devices 61 and 62. Wavelength division multiplexing signal coming from the amplifier 4 also includes data signals lambda _A. This data signal λ _A has already been transmitted through the entire ring network (loop return signal). This signal is reflected by the grating 62, which acts as a bandstop filter, and is discarded at an optical sump (appropriate connection of the optical fiber). Initially, the signal λ _{A, ADD} supplied to the coupler in a direction opposite to the transmission direction of the ring network is likewise reflected by the grating and thus transmitted further in this transmission direction. Various structures are known for the coupler 61 having a grating. Either place the grating in the coupling area (FIG. 3) or make two coupling areas and provide a separate grating for each fiber between each of these two coupling areas.

Of course, a connection having a plurality of channels between individual network nodes can also be realized. For this purpose, the add-drop modules shown in FIGS. 2 and 3 are connected in series or adapted accordingly. It is also possible to output or input multiple adjacent channels together by using a wider band filter.

FIG. 4 shows an expanded ring network in which the optical fiber 1 is supplemented by an optical fiber 1 P provided for protection purposes. In the event of breakage of the optical fiber 1 or other disturbances, only the protected data signal λ _AP is shown here, but the data signal is first transmitted over the undisturbed part of the ring network and then The data signal is supplied in the opposite direction to the protection optical fiber 1P, so that all the network nodes receive this data signal. The selection of the transmission path is performed by a changeover switch provided in the network node.

[Brief description of the drawings]

FIG. 1 is a unidirectional ring network.

FIG. 2 is a first embodiment of a network node.

FIG. 3 is an advantageous embodiment of this network node.

FIG. 4 is a unidirectional ring network with a spare transmission ring.

[Explanation of symbols]

NA~NN network node lambda _A to [lambda] _N wavelength division multiplexed signal lambda _A to [lambda] _N transmission channels 1 glass fiber 2 input 3 output 4 amplifier 5 output coupling device 6 infeed device 7 drop output side 8 adder input 51 1 : 2 coupler (branch device) 52 band stop filter 53 band pass filter 61 input coupling device (coupler) 62 grating 63 sump Λ _DROP branch transmission channel λ _DROP branch data signal λ _{A, ADD} insertion data signal λ _AP protection data signal

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] November 24, 2000 (2000.11.24)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Title of the Invention] Unidirectional optical ring network

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a unidirectional optical ring network according to the preamble of claim 1.

For transmission of large data volumes, ring networks are known, in which bidirectional data is transmitted between various network nodes / terminals, either unidirectionally or mostly via two fibers.

“22nd European Conference on Optical Communication” -ECOC 96, Oslo, p
.3.51-3.54 to "colored section ring"
Are known, in which wavelengths used only once each for transmission between two network nodes are used. This makes it possible, in the event of a disturbance, to connect a spare connection with the same wavelength via the undisturbed part of the ring network.

[0004] IEEE Photonics Technology Letters 6 (1994), No. 6, New York, p. 760-763,
Optically- “Amplified WDM Ring Network Incorporating Channel-Dropping Fi
lters ”includes an add-drop module (Add-D
A number of alternative embodiments for the rop-Module have been described. Conventional filters are used for signal output and input coupling.

Electric Letters 16 March 1995, Vol 31, No. 6, pages 476 and 477 describe add-drop modules, which basically consist of two couplers and a reflector. Has a filter. These add / drop modules are only suitable for certain networks. This is because signals having the same wavelength are input and output coupled.

“Optical Fiber Communication Conference” 1992, San Jose 27, Optical So
The Society of America, US, Washington DC 2006, pp. 255-256, describes an add / drop module having a plurality of conventional drop and add filters in FIG. The protection connection is made in the usual manner by backward steering of the data.

[0007] Electronics Letters, GB, IEE Stevenage, bd.32, No.3, 1, February 1996,
p.234-235, “Increased Capacity in an MS Protection Ring Using WDM Techni
A method of protection is known from "que and OADM: The Colored Section Ring". This protection method uses different wavelengths for the individual connection sections of a bidirectional ring network. The protected connection is not disturbed This is performed via a wavelength that is not used in the section.

[0008] In order to reconfigure the ring network, ie to create a new logical connection, a wavelength change is usually required. In newly envisioned optical ring networks, the dropping and insertion of data should take place at the optical level, and reconfiguration should be easily possible. A ring network including add-drop modules (network nodes) should be further implemented as cost-effectively as possible.

[0009] Such an add-drop module is defined in claim 1.

[0010] Advantageous embodiments of this add-drop module are derived from the dependent claims. A ring network realized thereby is described in claim 6.

[0011] Unidirectional ring networks are particularly inexpensive. This is because only one glass fiber is required for transmission, and the network node is simply configured. A fixed assignment of a given transmission channel or wavelength used in the ring network to the network node only once results in a unique assignment of the transmission channel, ie the transmitted data signal, to the network node. Since each network node receives the data signals of all other network nodes, any connection to the other network node can be made by selecting the corresponding receive filter. If a switchable or always tunable receive filter is selected, any connection can be made between all network nodes. Multiple filters also allow simultaneous connections to multiple network modes.

By using a coupler provided with a grating, an add / drop module or network node having a very simple structure can be obtained. This coupler has filter characteristics due to the grating.

If relatively high demands on transmission reliability are presented, a second ring is provided for the backup circuit. In this second ring, data transmission takes place in the opposite direction.

An embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a unidirectional ring network, FIG. 2 shows an easily conceivable embodiment of a network node, FIG. 3 shows an embodiment of the present invention of this network node, and FIG. Is a unidirectional ring network having

FIG. 1 shows a plurality of network nodes NA, NB, NC,. . . A unidirectional ring network with NN is shown. Transmission between arbitrary network nodes is performed in a wavelength division multiplexing mode via a glass fiber 1 and a plurality of transmission channels _{Ａ A} ~.
Made in lambda _N, the plurality of transmission channels lambda _A to [lambda] _N has a preset wavelength intervals. The transmission direction is indicated by an arrow.

FIG. 2 shows the principle circuit diagram of the network node NA in an easily conceivable embodiment. Network nodes are used for the realization of various connections that are always made via transmission channels. The data signal to be coupled out at this network node is called the "drop" signal, and the data signal to be transmitted is called the "insert" signal (add). Channels, also referred to as branching, conducting connections or insertions, refer to signals transmitted in this channel in a relatively narrow sense. Reference symbols having the same index are used for the transmission channel and the associated data signal. The data signal λ _A is transmitted on the associated transmission channel _{Ａ A.}

The network node reduced to the basic function of the add / drop module includes a series circuit of the amplifier 4, the output coupling device 5, and the input coupling device 6. The input side 2 receives wavelength division multiplexed signals λ _{A to} λ _{N of} all data signals received via the transmission channels _{Ａ A to Ｎ N.} In each transmission channel (transmission band), only one signal is transmitted, or a plurality of individual signals are transmitted in the wavelength division multiplex mode or, of course, in the time division multiplex mode.

The received signal is first amplified and then reaches the output coupling device 5. The division of all data signal / transmission channels into two signal paths is first performed in a 1: 2 coupler (branch). All the transmission signals to be conductively connected except for the transmission channel _ＡA assigned to this network node via one signal path
/ The transmission channel is connected conductively. The transmission channel Λ _D via the other signal path
The data signal λ _{DROP of} the _ROP or the transmission channel ＤＲ _DROP , for example, the data signal λ _{B, DROP} is output-coupled.

The transmission channel ＤＲ _DROP to be _dropped is selected by an output coupler, here configured as a wavelength separation filter. This wavelength separation filter is schematically illustrated here as a coupler 51 having a constant switchable or tunable bandpass filter 52 and a bandstop filter 53. Channel Λ _{D ROP} is the only channel in the passband of bandpass filter 52. This channel ＤＲ _DROP is transferred via the drop output 7 to, for example, a subscriber terminal.

Instead of the data signal / channel split off at this network node, the input coupling device 6 configured as a coupler in the transmission channel to which the corresponding data signal λ _{A, ADD} is applied to the summing input 8. Inserted. This presupposes that the signal λ _A (loop return signal) already transmitted from this network node A and received again at the input 2 via the ring must be blocked at the latest before the input coupling device 6. . For this purpose, a band-stop filter 53 is provided which is connected to the first signal path, and which is fixedly adjusted to a corresponding wavelength. The transmission of this signal can also be blocked at the front-end network node MN, but this has the additional configuration cost of adding additional network nodes.

The output side 3 outputs a wavelength division multiplexed signal. This wavelength division multiplex signal includes signals λ _{A, ADD} and λ _B to _N of all transmission channels.

By replacing, switching or adjusting the band-pass filter 52, each network node receives a corresponding transmission signal of each other network node. That is, a corresponding connection can be made. Therefore, a simple configuration change is possible.

FIG. 3 shows an embodiment of the invention for a network node. In this embodiment, an adjustable bandpass filter 54 is provided, and a coupler 61 having a grating 62 is used as the input coupling devices 61 and 62. Wavelength division multiplexing signal coming from the amplifier 4 also includes data signals lambda _A. This data signal λ _A has already been transmitted through the entire ring network (loop return signal). This signal is reflected by the grating 62, which acts as a bandstop filter, and is discarded at an optical sump (appropriate connection of the optical fiber). Initially, the signal λ _{A, ADD} supplied to the coupler in a direction opposite to the transmission direction of the ring network is likewise reflected by the grating and thus transmitted further in this transmission direction. Various structures are known for the coupler 61 having a grating. Place the grating in the coupling area (
FIG. 3) Alternatively, two coupling regions are created, and a separate grating for each fiber is provided between these two coupling regions.

Of course, a connection having a plurality of channels between individual network nodes can also be realized. For this purpose, the add-drop modules shown in FIGS. 2 and 3 are connected in series or adapted accordingly. It is also possible to output or input multiple adjacent channels together by using a wider band filter.

FIG. 4 shows an extended ring network in which the optical fiber 1 is supplemented by an optical fiber 1 P provided for protection purposes. In the event of breakage of the optical fiber 1 or other disturbances, only the protected data signal λ _AP is shown here, but the data signal is first transmitted over the undisturbed part of the ring network and then The data signal is supplied in the opposite direction to the protection optical fiber 1P, so that all the network nodes receive this data signal. The selection of the transmission path is performed by a changeover switch provided in the network node.

[Brief description of the drawings]

FIG. 1 is a unidirectional ring network.

FIG. 2 is an easily conceivable embodiment of a network node.

FIG. 3 is an embodiment of the present invention of this network node.

FIG. 4 is a unidirectional ring network with a spare transmission ring.

[EXPLANATION OF SYMBOLS] NA~NN network node lambda _A to [lambda] _N wavelength division multiplexed signal lambda _A to [lambda] _N transmission channels 1 glass fiber 2 input 3 output 4 amplifier 5 output coupling device 6 infeed device 7 drop output side 8 Addition input side 51 1: 2 coupler (branch device) 52 Band stop filter 53 Band pass filter 61 Input coupling device (coupler) 62 Grating 63 Optical sump Λ _DROP branch transmission channel λ _DROP branch data signal λ _{A, ADD} insertion data signal λ _AP protected data signal

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kuno Zubar-Oklok, Austria Vienna Rampersh Tolfagasse 40/12 (72) Inventor Martin Schleipliner Vienna, Wald. Schwarzachasse 3/69 F-term (reference) 5K002 AA06 BA04 BA31 DA02 DA03 DA06 DA11 EA33 FA01 5K031 AA06 AA08 CA15 CB12 DA12 DA19 DB12 DB14 EB02

Claims (6)

[Claims] 1. Unidirectionality having a plurality of network nodes (NA to NN)
An optical ring network comprising a data signal (λ_A, λ_B, ... λ_N) Is wavelength division
It is transmitted in the multiplex mode, and each network node (NA to NN) transmits
Data signal (λ_A,_ADD) With a transmission band used only once.
The transmission channel (Λ_A), Multiple network nodes
In a unidirectional optical ring network having nodes (NA to NN), each network node (NA to NN) includes an optical output coupling device (5) and an optical input coupling device.
The optical output coupling device (5) has a transmission channel (Λ). _A ~ Λ_N) Received at the optical data signal (λ_A~ Λ_N) Are supplied to the optical output coupling device (5) of the network node (NA).
Other network nodes (NB to NN) by filters (52, 53; 62)
The transmission channel (Λ_DROP; Λ_BAt least)
Are also output-coupled, and their assigned transmission channels (Λ_A) Already sent in
A unique data signal (λ_AOther than)
Transmission channel (Λ_B~ Λ_N) Data signal (λ_B~ Λ_N) Are conductively connected, and in the input coupling device (6), each of the transmission channels is conductively connected.
(Λ_B~ Λ_N) Is the data signal to be inserted (λ_A,_ADD)
The assigned transmission channel (Λ_A), The data to be inserted
Signal (λ_A,_ADD) Is transmitted together with the data signal that has been conductively connected.
Characterized unidirectional optical phosphor having a plurality of network nodes (NA to NN)
Network. 2. The output coupling device (5) comprises different transmission channels (Λ _DROP ;
光_{B, DROP} ) is coupled out. 3. The output coupling device (5) comprises an exchangeable filter (52, 53).
3. The optical ring network according to claim 2, wherein the optical ring network comprises a plurality of filters and is switchable between the replaceable filters (52, 53) or the plurality of filters. 4. The output coupling device comprises a coupler (51) and an adjustable filter (
An optical ring network according to claim 2, characterized in that the optical ring network comprises: 5. A lens which acts as an optical filter as an input coupling device (6).
A coupler (61) having a coating (61) is provided.
Assigned transmission channel (Λ_A) Sent over the ring network
Data signal (λ_A) And further insert the data signal ((Λ _{A, ADD} ) Is connected to the data signal (λ_B~ Λ_N)
The optical ring network according to claim 1, wherein 6. The optical ring network according to claim 1, wherein a further fiber (1P) is provided for protection purposes.