JPH0685748A - Optical communication network - Google Patents

Abstract

PURPOSE:To provide the optical communication network in which wavelength management and wavelength allocation control are simplified and the accuracy of the operating wavelength are enough to be deteriorated by setting a wavelength of a path to a wavelength multiplex optical link and transferring the resulting wavelength according to a connection table for each optical communication node. CONSTITUTION:Wavelengths for paths set to on respective path of optical communication nodes 1a-1f are stored in advance, and a table used by a wavelength conversion section and a spatial switch is provided to a wavelength path routing controller. Then the table is so devised that the wavelengths for each of wavelength multiplex optical links 2a-2g set between two optional communication nodes 1a-1f are allowed to be different. Thus, the wavelength allocation control to wavelength paths 3a-3d having been required when the wavelength paths 3a-3d are formed by using the same wavelength between terminations is not required and the accommodation design to the wavelength multiplex optical links 2a-2g including the wavelength allocation control complicating the problem is simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used for wavelength division multiplexing optical communication. In particular, it relates to a switching setting technique of a mesh transmission line using a plurality of different wavelengths.

[0002]

2. Description of the Related Art An optical communication node using various optical devices and a wavelength division multiplexing optical communication network using a link using an optical fiber cable connecting them are widely used because of their large information transmission capacity.

A conventional example will be described with reference to FIGS. 7 and 8. FIG. 7 is a diagram showing a conventional optical communication network. FIG. 8 is a diagram showing a routing table. The optical communication network has optical communication nodes 1a, 1b, 1c, 1d, 1e, 1f, and WDM optical links 2a, 2b, 2 for connecting them.
There are c, 2d, 2e, 2f, and 2g.

Any of these optical communication nodes 1a, 1b,
In order to communicate between 1c, 1d, 1e, and 1f, a transmission line connecting them is necessary. This transmission line has limited wavelength-multiplexed optical links 2a, 2b, 2c, 2d, 2e,
As a method of using 2f and 2g, there is a method of allocating wavelength paths of a plurality of wavelengths.

In FIG. 7, the wavelength path 3a of wavelength λa (solid line) connects the optical communication nodes 1a-1b-1c-1f, and the wavelength path 3b of wavelength λb (dashed line) is the optical communication nodes 1a-1b-. Connect 1e-1f. Also, the wavelength λ
The wavelength path 3c of c (broken line) is the optical communication node 1e-1b.
-1c is connected, and the wavelength path 3d of wavelength λa (solid line) is
The optical communication nodes 1a-1d-1e-1f are connected.

An electrical signal to be transferred from the optical communication node 1a to the optical communication node 1f via the optical communication nodes 1b and 1c is converted into an optical signal of wavelength λa at the optical communication node 1a, and the wavelength division multiplexing optical link 2a- It is transferred on the wavelength path 3a via 2b-2e. In FIG. 7, the wavelength paths 3a, 3
In order to form b, 3c and 3d, at least three wavelengths λa and λ
b and λc are required.

At this time, the same WDM optical links 2a,
If the wavelengths on 2b, 2c, 2d, 2e, 2f, and 2g overlap, it becomes impossible for the receiving side to distinguish the signals by wavelength, so that the wavelengths used do not overlap in any wavelength-multiplexed optical link in the optical communication network. , Wavelength paths 3a, 3b, 3
It is necessary to assign wavelengths to c and 3d. Further, the wavelength paths 3a, 3b, 3c and 3d are connected to the respective optical communication nodes 1a and 1
Each optical communication node 1a, 1b, 1c, 1d, 1e, 1f has a routing table of the wavelength paths 3a, 3b, 3c, 3d in order to select the route by b, 1c, 1d, 1e, 1f.

The routing table will be described with reference to FIG. FIG. 8 is a diagram showing a routing table of the conventional device. Each optical communication node 1a, 1b, 1c, 1d,
As described above, 1e and 1f have a function of connecting each wavelength path 3a, 3b, 3c, 3d on the input transmission line to an appropriate output transmission line according to the information of this routing table. The wavelengths assigned to the same wavelength path 3a, 3b, 3c, 3d are always the same in the network, and do not change each time the connection is made in the optical communication node.

[0009]

In the configuration of the wavelength routing network of such a system, since one wavelength is assigned to each end of the wavelength path, the wavelength paths accommodated in each wavelength-multiplexed optical link in the network are Wavelength path wavelength allocation control is essential so that wavelengths do not overlap on the same wavelength-multiplexed optical link for each wavelength path.

This wavelength allocation control becomes complicated as the number of optical communication nodes, the number of wavelength-multiplexed optical links, and the number of wavelength paths to be accommodated increases, and wavelength allocation control is performed in a network of the same scale as an actual communication network. Therefore, it requires an extremely large amount of calculation time, and in general, it is difficult to obtain an optimum solution that requires the minimum number of wavelengths used in the network. About this, I. Chlamtac, A. Ganz and G. Karmi "Purely Optical
Networks for Terabit Communication, "Proc.INFOCOM
'89, PP887 -896.

In order to allocate one wavelength to one wavelength path between the terminals, the number of wavelength paths increases, the number of wavelengths required in the network increases, and wavelength management is centrally managed in the network. There is a need for a centralized management device for wavelength allocation, and when connecting wavelength paths at optical communication nodes, especially when the number of wavelengths used in the network increases, strict absolute accuracy is required. There were many problems.

The present invention has been made under such circumstances, and an object of the present invention is to provide an optical communication network which simplifies wavelength management and wavelength allocation control and which may have low accuracy of wavelengths to be used.

[0013]

SUMMARY OF THE INVENTION The present invention comprises several optical communication nodes and wavelength-multiplexed optical links connecting the optical communication nodes, wherein the optical communication node is the input-side wavelength-multiplexed optical link. A wavelength demultiplexer that inputs and demultiplexes wavelength-multiplexed optical signals from the link, a wavelength conversion unit that converts each signal demultiplexed by this wavelength demultiplexer into an assigned wavelength, and a wavelength conversion unit from this wavelength conversion unit. It is an optical communication network including a space switch for outputting a signal to a designated path and a wavelength multiplexer for wavelength-multiplexing the output from the space switch to the wavelength-multiplexed optical link on the output side and outputting the wavelength-multiplexed light.

Here, the feature of the present invention is to provide a table in which the wavelengths preset for each route of each optical communication node are stored and used by the wavelength conversion unit and the space switch, and the contents of the table are In this configuration, the wavelengths set between any two optical communication nodes allow different wavelengths to be used for each wavelength-multiplexed optical link.

Further, it is desirable that a combination of wavelengths to be multiplexed in a signal transmitted to one wavelength multiplexing optical link is set in advance as a small number of wavelength groups. In this case, the wavelength conversion unit and the space switch may be limited in type for each wavelength group.

[0016]

[Operation] When converting an electric signal into an optical signal from the optical communication node at the start point to the optical communication node at the end point and selecting and transferring the route according to the wavelength of light, wavelength conversion is performed at the optical communication node on the way. . That is, according to the connection table for each optical communication node, each wavelength is transferred to the wavelength multiplexing optical link and transferred.

In each optical communication node between the optical communication node at the start point and the optical communication node at the end point, the signal of each optical wavelength on the wavelength-multiplexed optical link on the input side is separated for each wavelength, and the wavelength path is connected to the connection table. In accordance with the contents of the above, the switch function to connect to the corresponding output transmission line described, the means for converting to the corresponding output wavelength described, and the conversion to each appropriate output wavelength from the wavelength-multiplexed optical link on the different input side. It is realized by means for wavelength-multiplexing the obtained optical signal and sending it to each output transmission line.

When a small number of wavelength groups are set, the number of wavelength conversion units and space switches is limited, which is advantageous.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the first embodiment device of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of the first embodiment of the present invention. FIG. 2 is a block diagram of an optical communication node.

The present invention includes six optical communication nodes 1a and 1
b, 1c, 1d, 1e, 1f and this optical communication node 1
WDM optical links 2a, 2b, 2c, 2d, 2e, 2 that connect a, 1b, 1c, 1d, 1e, and 1f, respectively.
f, 2g, and optical communication nodes 1a, 1b, 1c, 1
d, 1e, and 1f are wavelength-multiplexed optical links 2a, 2b, 2c, 2d, 2e, 2f, and 2g on the input side corresponding to each of them.
A wavelength demultiplexer 11 for inputting and demultiplexing a wavelength-multiplexed optical signal from the optical fiber 10, and a wavelength converter 12 for converting each signal demultiplexed by the wavelength demultiplexer 11 into an assigned wavelength. A spatial switch 14 that outputs a signal from the wavelength conversion unit 12 to a designated path, and wavelength-multiplexed optical links 2a, 2b, 2c, 2d, and 2e on the output side corresponding to the output from the spatial switch 14, respectively. 2f, 2g
And a wavelength multiplexer 16 for wavelength-multiplexing and outputting to the optical communication network.

Here, the feature of the present invention is that the optical communication nodes 1a, 1b, 1c, 1d, 1e,
The wavelength path routing control device 13 is provided with a table for storing the wavelengths of the wavelength paths set for each 1f route and used by the wavelength conversion unit 12 and the space switch 14, and the contents of the table are arbitrary two optical communication nodes. 1a, 1b,
1c, 1d, 1e, 1f, wavelength multiplexing optical links 2a, 2b, 2c, 2d, 2e, 2f, 2 of wavelength paths set between
This is a configuration that allows different wavelengths to be used for each g.

Next, the operation of the optical communication network according to the first embodiment of the present invention will be described with reference to FIG. An electrical signal to be transferred from the optical communication node 1a to the optical communication node 1f via the optical communication nodes 1b and 1c is converted into an optical signal having a wavelength λa by the optical communication node 1a, and the wavelength division multiplexing optical links 2a-2b-2e.
Are transmitted on the wavelength path 3a having the same wavelength λa. The electrical signal to be transferred from the optical communication node 1a to the optical communication node 1f via the optical communication nodes 1b and 1c is converted into an optical signal of wavelength λb at the optical communication node 1a and transferred on the wavelength division multiplexing optical link 2a. Optical communication node 1
b, the wavelength is converted from the wavelength λb to λa in the optical communication node 1b, transferred on the optical link 2d, reaches the optical communication node 1e, and is wavelength-converted from the wavelength λa to λb in the optical communication node 1e. It is transferred on the multiplex optical link 2g and reaches the end point optical communication node 1f. That is, the wavelength path 3
The wavelength b is wavelength-converted for each wavelength-multiplexed optical link and is connected as λa → λb → λa.

WDM optical links 2a, 2b, 2c, 2
wavelength paths 3a accommodated in d, 2e, 2f, and 2g,
The wavelengths 3b, 3c, and 3d are assigned to each wavelength multiplexing optical link so that the wavelengths used do not overlap on any one wavelength multiplexing optical link in the network.

Next, referring to FIG. 2, the optical communication node 1a,
The operation of 1b, 1c, 1d, 1e, 1f will be described. Wavelengths of maximum n waves are wavelength-multiplexed in each of the single optical fibers 10 on the input side. In this case, each wavelength-multiplexed optical link 2a, 2b, 2c, 2d, 2e, 2f, 2g can simultaneously have a maximum of n wavelength paths within the same link.
The optical fiber 10 on each input side is connected to the wavelength demultiplexer 11, and the optical signal transmitted through the optical fiber 10 is separated for each wavelength and input to the wavelength conversion unit 12. Wavelength converter 1
The respective wavelengths from the respective optical fibers 10 input to the 2 are converted into appropriate wavelengths based on the information from the wavelength path routing control device 13 including the routing table. The wavelength paths 3a to 3n of the respective wavelengths thus converted are input to the space switch 14, and based on the information from the wavelength path routing controller 13, the wavelength multiplexer corresponding to the designated optical fiber 15 on the output side. It is connected to the input side of 16 and is multiplexed by the wavelength multiplexer 16 and output to the optical fiber 15.

Next, the routing table will be described with reference to FIG. FIG. 3 is a diagram showing a routing table. The wavelength to be converted on the output transmission path is specified in the routing table. The transmission line number on the input side,
The corresponding transmission line number on the output side is shown, and the corresponding wavelength is also shown. This routing table is included in the wavelength path routing control device 13 shown in FIG.

The wavelength demultiplexer 11 uses a multilayer filter, a grating, an optical branching element such as an optical star coupler, a wavelength filter capable of extracting a specific wavelength, or a tunable wavelength demultiplexer. It can also be realized by combining with a wavelength filter. As the wavelength filter, one using a planar waveguide can be used in addition to the bulk type. Further, the wavelength multiplexer 12 uses a multilayer film filter, a configuration using a grating, and n
It is also possible to use an optical coupler of pair 1 or n: m. The optical coupler and the like can be realized by using a flat waveguide as well as a fiber fusion type.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 shows an optical communication node 1a, 1b, 1c, 1d, 1e, 1f used in the optical communication network of the second embodiment of the present invention.
It is a block diagram of. The second embodiment of the present invention is the optical communication nodes 1a, 1b, 1c, 1d, 1e of the first embodiment of the present invention.
Optical communication nodes 1a, 1b, 1c, 1 having different configurations to 1f
The feature is that d, 1e, and 1f are used. In the optical communication nodes 1a, 1b, 1c, 1d, 1e, 1f, the wavelength conversion unit 12 and the space switch 14 are connected in the reverse order. This operation starts with the space switch 14
Are connected to the paths connected to the wavelength paths 3a to 3n on the input side and the wavelength paths 3a to 3n on the output side corresponding to the wavelength paths 3a to 3n, and then converted to the corresponding wavelengths by the wavelength conversion unit 12.

Next, the wavelength converter 12 of the optical communication node will be described with reference to FIG. FIG. 5 is a diagram showing the wavelength conversion unit 12. The wavelength converter 12 shown in FIG. 5 is a system that converts an optical signal from wavelength λi to λj without converting it to an electrical level. As a method of converting the wavelength of an optical signal without converting it into an electric signal, here, a method using an optical-optical wavelength converter 17 utilizing three-wave mixing or four-wave mixing of an organic or inorganic nonlinear material is used. In addition, a method of using a bistable LD that uses the original signal as a trigger light during intensity modulation, and a signal light is injected into a light source such as an LD after FM-IM conversion during frequency modulation to change the carrier density in the light source and oscillate frequency. , A method of extracting and amplifying a side band of modulated signal light, a method of obtaining a large frequency change by cascading effects of small frequency shift (-10 GHz) such as injection locking and Brillouin scattering in multiple stages. is there.

FIG. 6 is a diagram showing another example of the wavelength conversion section. In this example, in the wavelength conversion unit 12, an optical signal of wavelength λi is once converted into an electrical signal by the photoelectric converter 18, and an electrical signal of wavelength λj is obtained by the electro-optical converter 19 using this electrical signal. . As a method to change the wavelength of the optical signal by converting it once into an electrical signal, here we used the method of opto-electrically converting with a separate optical receiver for each wavelength and directly modulating a specific wavelength with the electrical signal. . For the modulation of the optical signal, here, the method of directly modulating the light source was used, but in addition to this, the method of using an external modulator, the method of specifying the wavelength and the method of specifying the light source that oscillates at a specific wavelength, and controlling the wavelength of the light source There is a method of doing so, or a method of combining both.

In the present invention, the wavelength division multiplexing optical link 2a,
The wavelengths multiplexed on 2b, 2c, 2d, 2e, 2f, 2g are used to identify the corresponding wavelength paths 3a, 3b, 3c, 3d, and the absolute accuracy of the wavelength is low in the network. May be. In other words, one WDM optical link 2
When n-wave multiplexing is performed with a, 2b, 2c, 2d, 2e, 2f, and 2g, wavelengths λ1, ..., λn are used as n waves, and other wavelength-multiplexed optical links 2a, 2b, 2c, 2d, 2 are used.
The wavelengths λ′1, ..., λ′n may be used for e, 2f, and 2g. That is, the WDM optical links 2a, 2b, 2c, 2
It suffices if n waves can be identified for each of d, 2e, 2f, and 2g. Therefore, the wavelength standard in the network, which is indispensable in the wavelength path method using the same wavelength between the ends described in the conventional example, is unnecessary, and the wavelength multiplexing optical links 2a, 2b, 2c, 2d, 2
e, 2f, 2g for each of the other wavelength division multiplexing optical links 2a in the network,
The wavelength can be set regardless of 2b, 2c, 2d, 2e, 2f, and 2g.

Further, along with this, it is not necessary to manage the wavelength allocation for each wavelength path in the network, and the wavelength multiplexing optical links 2a, 2
Individual management for each of b, 2c, 2d, 2e, 2f, and 2g is sufficient.

Further, according to the optical communication networks of the first to third embodiments of the present invention, the optical communication nodes 1a, 1b, 1c, 1d, 1e, 1f at the starting points of the wavelength paths 3a, 3b, 3c, 3d are provided.
Optical communication nodes 1a, 1b, 1c, 1d, 1e, 1 at the end point
optical links 2a, 2b, 2c, 2d, 2e, 2f with f,
Since the vacant appropriate wavelengths are connected every 2 g to form the end-to-end wavelength paths 3a, 3b, 3c, and 3d, the same wavelength is used between the ends as in the conventional technique. The wavelength allocation control to the wavelength paths 3a, 3b, 3c, and 3d, which is necessary when forming 3b, 3c, and 3d, becomes unnecessary. For this reason, the wavelength paths 3a, 3b, 3c, which have been extremely complicated in the conventional technology,
WDM optical links 2a, 2 including wavelength allocation control to 3d
The accommodation design in b, 2c, 2d, 2e, 2f, and 2g is extremely simplified, and the calculation time required for wavelength allocation can be greatly reduced. This is because each wavelength path 3a, 3b,
It is not necessary to consider the wavelength allocation unique to each of the networks 3c and 3d, and each wavelength multiplexing optical link 2a, 2b, 2c, 2
The wavelength paths 3a, 3b, 3c, 3d are provided under the constraint that the wavelengths corresponding to the number of wavelength paths 3a, 3b, 3c, 3d can be independently set in d, 2e, 2f, 2g.
WDM optical links 2a, 2b, 2c, 2d, 2e, 2
This is because it is possible to design the housing in f and 2g. In addition,
In the prior art, the wavelength paths 3a, 3b, 3c, 3d
Since one wavelength is assigned to each network, it may be possible to assign the same wavelength to each path if there are completely different routes even between the same ends. WDM optical links 2a, 2b, 2c, 2d,
2e, 2f, and 2g also share the wavelength path 3a,
There is a constraint that the same wavelength cannot be assigned to 3b, 3c, and 3d. Therefore, in the optical communication network of the first or second embodiment of the present invention, the wavelength usage efficiency in the network is high,
That is, it is possible to significantly reduce the required minimum number of wavelengths required to accommodate the same number of wavelength paths 3a, 3b, 3c, 3d as compared with the conventional technique. This requires, for example, three wavelengths in the conventional example to accommodate the same path and the same number of wavelength paths of the optical communication network described as the conventional example and the optical communication networks of the first to second embodiments of the present invention. It can be easily confirmed from the fact that the optical communication network according to the first or second embodiment of the present invention can use two wavelengths.

Further, in the prior art, when a network is added, a wavelength division multiplexing optical link and an optical communication node are newly added, and a new wavelength path is set, wavelength reassignment to a wavelength path in the network is carried out. In general, a re-accommodation design including the above is required, but in the present invention, even when a network is added and a new path is set, it is vacant for each wavelength multiplex link including the newly added wavelength multiplex optical link. Since the existing wavelengths can be connected and a new path can be easily set, the proportion of re-accommodation design required can be significantly reduced as compared with the prior art.

Further, in the optical communication network of the first or second embodiment of the present invention, the wavelength division multiplexing optical links 2a, 2b, 2 are provided.
The wavelengths multiplexed on c, 2d, 2e, 2f, and 2g are used for identification in the wavelength links of the corresponding wavelength paths 3a, 3b, 3c, and 3d, and the absolute wavelengths in the network are No precision required. In other words, when n-wave multiplexing is performed in a certain wavelength-multiplexed optical link, the absolute value of the n-wave may be different in each of the other wavelength-multiplexed optical links. That is, the WDM optical links 2a, 2b, 2c, 2d, 2e, 2f,
It suffices if n waves can be identified every 2 g. This eliminates the need for the wavelength standard in the network, which was necessary in the conventional wavelength path system that uses the same wavelength between the ends, and the wavelength multiplexing optical links 2a, 2
b, 2c, 2d, 2e, 2f, 2g, the other wavelength division multiplexing optical links 2a, 2b, 2c, 2d, 2e, 2f, 2 in the network.
This means that the wavelength can be set irrespective of g, and it is possible to greatly relax the requirements regarding the wavelength of the optical components used in the network, and it is possible to construct an economical communication network.

Further, in accordance with this, centralized wavelength allocation management in the network becomes unnecessary, and the wavelength multiplexing optical links 2a, 2b,
Since individual management for each of 2c, 2d, 2e, 2f, and 2g is sufficient, a large-scale database or the like required for unified management is unnecessary, and the network can be made economical.

Further, instead of performing the operation of the present invention for each wavelength multiplexed on one wavelength multiplex optical link, the optical signal multiplexed on one wavelength multiplex link is divided into a plurality of wavelength groups, The wavelength demultiplexer 11, the wavelength conversion unit 12, and the wavelength multiplexer 16 that configure the optical communication node are configured by considering each wavelength group as one wavelength and performing the process for each wavelength group. It can be simplified.

For example, in FIG.

[0038]

[Equation 1] , For example, λ ₁ is λ ₁₁ , ..., λ
Includes _1m m wave. The node does not recognize each of these m waves. It operates by recognizing λ _{1 as a} whole.

Up to now, the case of optical wavelength multiplexing has been described, but it is also possible to adopt a structure in which a coherent optical communication system is applied instead of the optical wavelength to perform route selection by optical frequency.

[0040]

As described above, according to the present invention, the wavelength management and the wavelength allocation control can be simplified and the number of wavelengths used can be reduced, so that the accuracy of each wavelength can be lowered. As a result, the man-hours and costs for expanding the optical communication network can be significantly reduced.

Further, the accuracy required for the optical parts used is relaxed, and an economical optical communication network can be constructed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of an optical communication node.

FIG. 3 is a diagram showing a routing table.

FIG. 4 is a block diagram of an optical communication node according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a wavelength conversion unit according to first and second embodiments of the present invention.

FIG. 6 is a diagram showing a wavelength conversion unit according to a third embodiment of the present invention.

FIG. 7 is a block diagram of a conventional device.

FIG. 8 is a diagram showing a routing table of a conventional device.

[Explanation of symbols]

1a, 1b, 1c, 1d, 1e, 1f Optical communication node 2a, 2b, 2c, 2d, 2e, 2f, 2g Wavelength multiplexed optical link 3a, 3b, 3c, 3d Wavelength path 10, 15 Optical fiber 11 Wavelength demultiplexer 12 wavelength converter 13 wavelength path routing controller 14 spatial switch 16 wavelength multiplexer 17 optical-optical wavelength converter 18 opto-electric converter 19 electro-optical converter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location H04Q 3/52 C 9076-5K 8529-5K H04L 11/00

Claims (2)

[Claims] 1. A plurality of optical communication nodes and a wavelength-multiplexed optical link connecting the optical communication nodes, respectively, wherein the optical communication node is an optical signal wavelength-multiplexed from the input-side wavelength-multiplexed optical link. , A wavelength demultiplexer that demultiplexes by inputting, a wavelength demultiplexer that converts each signal demultiplexed by this wavelength demultiplexer into an assigned wavelength, and a signal from this wavelength demultiplexer to a specified route. In an optical communication network equipped with a space switch for outputting and a wavelength multiplexer for wavelength-multiplexing and outputting the output from this space switch to the wavelength-multiplexed optical link on the output side, A table that stores the set wavelengths and that is used by the wavelength conversion unit and the space switch is provided, and the contents of the table are the wavelength multiplexing optical links of the wavelength paths set between any two optical communication nodes. Optical network, wherein the wavelength used for each is configured to allow different. 2. The optical communication network according to claim 1, wherein a combination of wavelengths to be multiplexed in a signal transmitted to one wavelength multiplexing optical link is set in advance as a small number of wavelength groups.