JPH0586712B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a communication path of an exchange for exchanging high-speed, high-bandwidth signals such as image information.

(Prior Art and its Problems) In recent years, the demand for audio-visual communications based on video has increased, and in response to this demand, research is underway on switching equipment that can exchange broadband and high-speed signals both domestically and internationally.

Generally, image information has a band of 4 MHz for broadcast television and 30 MHz for high-definition television, and the bit rate of the digital signal obtained by digital encoding ranges from 100 Mb/s to 200 to 500 Mb/s.

Communication path switches that exchange such high-speed, high-bandwidth signals include switch elements or gate circuits made of GaAs FETs, etc., at each intersection of multiple incoming lines and multiple outgoing lines that intersect with each other. A plurality of lines are provided, and a desired incoming line and a desired outgoing line are connected by control signals. For example, the collection of papers from the 1985 National Conference of the Institute of Electronics and Communication Engineers,
A GaAs FET matrix switch described in Volume 2, No. 486 is known.

This GaAs FET matrix switch is thought to be limited to a matrix size of approximately 8x8 due to limitations such as power consumption, chip size, and crosstalk characteristics. Therefore, in order to obtain a high-capacity communication path for practical use, it is necessary to use a small matrix size.
A multi-stage link connection method can be considered in which multiple GaAs FET matrix switches are arranged in multiple stages and each stage is linked.

However, GaAs FETs generally have a lower load driving ability than bipolar transistors, so when the wiring length between each stage of the communication path becomes long, the signal speed is limited by distributed capacitance. In addition, stray capacitance existing between lines causes deterioration of crosstalk characteristics.

As a means to solve such problems,
It is conceivable to integrate opto-electric conversion circuits and electro-optic conversion circuits at the input and output of a GaAs FET matrix switch, and to perform link connections between each stage of the communication path using optical fiber cables.

However, compared to electrical signals, the loss at optical connectors or splice points varies widely.
This creates a new problem in that the loss differs depending on the communication path. Furthermore, even if GaAs/FET matrix switches, optical/electrical conversion circuits, electrical/optical conversion circuits, etc. are integrated, GaAs/FET matrix
It has the disadvantage that it is difficult to miniaturize the package because it requires as many optical connectors as the number of input and output signals of the switch, and it also requires many optical fiber cables for link connections between each stage of the communication path. .

This point will be explained in detail with reference to the drawings.

FIG. 1 is a diagram showing an example of a conventional broadband communication path.

The broadband communication path shown in FIG.
By connecting the secondary switch 170 configured by 0 and 150 with links 181 to 189, the incoming lines 161 to 169 and the outgoing lines 171 to
179.

In FIG. 1, for example, the incoming line 162 and the outgoing line 17
5 is the incoming line 162 - grid switch 1
00-link 182-grid switch 140-outgoing line 175.

FIG. 2 is a diagram showing a specific example of the lattice switch shown in FIG. 1.

According to FIG. 2, the grid switch 1 shown in FIG.
00 is incoming lines 201, 202 and 203 and outgoing line 2
Switch element 2 is configured by switch elements 221 to 229 provided at each intersection with 11, 212, and 213, and is controlled by a control circuit (not shown).
By controlling the opening and closing of lines 21 to 229, a desired connection is made between the incoming line and the outgoing line.

Returning to FIG. 1, links 181-18 connecting between primary switch 160 and secondary switch 170
9 has a distributed capacitance as shown, for example, in a capacitor 191, and this value, together with the output impedance of a signal source (not shown) connected to input lines 167, 168 and 169, determines the signal band that can be exchanged by the wideband communication path. This is a factor that limits speed.

Further, there is a line capacitance between the links 181 to 189, such as a capacitor 192, which causes crosstalk between the links 181 and 184.

Furthermore, in order to configure the wideband communication path shown in FIG.
A total of nine wires are required for the link connection between the primary switch 160 and the secondary switch 170, and this value increases as the number of grid switches that make up the primary switch 160 and the secondary switch 170 increases.
When the number of secondary switches 170 is m and the number of secondary switches 170 is n, m×n links are required.

FIG. 3 is a diagram showing an example of a conventional broadband communication path.

In FIG. 3, the same numbers as in FIG. 1 indicate the same components as in FIG.

In the wideband communication path shown in FIG.
Electrical/optical conversion circuits 304, 305, and 306 are provided on the output lines of the grid switch 10, and electrical/optical conversion circuits 307, 308, and 309 are provided on the output lines of the grid switch 120, respectively. 311, 312 and 313
, optical-to-electrical conversion circuits 314, 315, and 316 are connected to the input line of the grid switch 140, and optical-to-electrical conversion circuits 317, 318 are connected to the input line of the grid switch 150.
and 319, the link connection between the primary switch 160 and the secondary switch 170 is established by providing optical fiber cables 321 to 319, respectively.
It is carried out by 9.

In the wideband communication path shown in FIG.
Since this is carried out by a 3D converter, there is no distributed capacitance 191 or line capacitance 192 shown in FIG. 1, and therefore wideband, high-speed signals can be exchanged with good crosstalk characteristics.

However, in general, optical connectors, splices, etc. have a large variation in loss compared to electrical signals, which causes variation in insertion loss between communication paths from incoming lines 161-169 to outgoing lines 171-179.

Furthermore, in the wideband communication path shown in Figure 3,
Nine optical fiber cables are required for the link connection between the primary switch 160 and the secondary switch 170, and, for example, the grid switch 100 and the electrical/optical conversion circuits 301, 302, and 303 are integrated on the same chip. Even if the optical fiber cables 321, 322, and 323 are connected, it is necessary to provide three optical connectors, and this value increases as the number of grid switches that make up the primary switch 160 and the secondary switch 170 increases. For example, the primary switch 160
If the number of switches is m, and the number of secondary switches 170 is n, then m×n optical fiber links are required, and the grid switch belonging to the primary switch 160 is connected to m optical connectors belonging to the secondary switch 170. Each grid switch must be provided with n optical connectors, which is a factor that limits the miniaturization of broadband communication paths.

(Objective of the Invention) The present invention has good crosstalk characteristics, can reduce variation in loss between each communication path, and has a small number of optical fiber cables.
An object of the present invention is to provide a broadband communication path whose package can be easily miniaturized.

(Structure of the Invention) In order to achieve the above object, the present invention provides the following: a primary switch composed of i lattice switches with m inputs and n outputs; n of each grid switch belonging to the primary switch in a broadband channel having at least a secondary switch configured
n x i electrical/optical conversion circuits that convert the output electrical signals into n optical signals each having a different wavelength;・i optical multiplexers each having n input terminals connected to the output terminal of the optical conversion circuit; and i optical wavelength multiplexed signals output from the i optical multiplexers. , i input optical waveguides each arranged in parallel; n output optical waveguides intersecting the input optical waveguide and each arranged in parallel; Each of the n optical signals of the n-multiplexed wavelength multiplexed optical signals on the input optical waveguide is arranged at each intersection with the output optical waveguide.
After demultiplexing any one optical signal from the n-multiplexed wavelength-multiplexed optical signals on the input optical waveguide, it is distributed to each grating switch configuring the secondary switch. The i×n wavelength selection elements that are combined as multiplexed optical signals and the n i-multiplexed wavelength multiplexed optical signals output from the n output optical waveguides are respectively inputted, and i
n optical demultiplexers that separate the optical signals into n optical demultiplexers; i output optical signals of each of the optical demultiplexers are respectively input, and i
This circuit further includes i×n optical/electrical conversion circuits connected to the input terminals of the grid switch with input j outputs.

(Embodiment) FIG. 4 is a block diagram showing an embodiment of the present invention.

In FIG. 4, the same numbers as in FIG. 3 indicate the same components as in FIG.

In the embodiment of the present invention shown in FIG. 4, wavelengths λ ₁ , λ ₂ and λ ₃ are assigned to the output wavelengths of the electrical-to-optical conversion circuits 301, 302 and 303, respectively, and the wavelengths are combined by an optical multiplexer 401. Later, it is output as a wavelength multiplexed optical signal and added to the input of the wavelength selection circuit 420. Similarly, electrical/optical conversion circuit 30
The wavelengths λ ₂ , λ ₃ and λ ₁ are assigned to the output wavelengths of the optical multiplexers 402 and 306, and the wavelengths λ ₃ , λ ₁ and λ ₂ are assigned to the output wavelengths of the electro-optical conversion circuits 307, 308 and 309, respectively. After being multiplexed by 403, the signals are output as a wavelength multiplexed optical signal and added to the input of the wavelength selection circuit 420.

The wavelength selection circuit 420 has input optical waveguides 431 and 4
32 and 433, and output optical waveguides 441, 44
2 and 443, and the wavelength selection elements 423, 426, and 429 select the wavelength λ from the wavelength-multiplexed optical signals of the input optical waveguides 431, 432, and 433, respectively. After selecting the optical signals of _{λ 1} , λ ₂ and λ ₃ , they are combined and output from the output optical waveguide 443 as a new wavelength multiplexed optical signal.

Similarly, the wavelength selection elements 422, 425 and 428 select optical signals of wavelengths λ ₂ , λ ₃ and λ ₁ from the wavelength multiplexed optical signals of the input optical waveguides 431, 432 and 433, respectively, and the wavelength selection elements 421, 42
4 and 427 are input optical waveguides 431 and 427, respectively.
After selecting optical signals of wavelengths λ ₃ , λ ₁ and λ ₂ from wavelength multiplexed optical signals of 432 and 433, multiplexing them,
They are output to output optical waveguides 442 and 441 as new wavelength multiplexed signals, respectively.

Here, the wavelength selection elements 421 to 429 include, for example,
A comb- _shaped electrode is placed on top of the directional coupler formed by diffusing Ti into LiNbO ₃ .
There is a known method that uses periodic changes in the refractive index due to the electro-optic effect of the electro-optic effect to cause a blurred reflection in an optical signal in a desired wavelength band. It is being

The wavelength-multiplexed optical signal outputted from the output optical waveguide 443 in this manner is demultiplexed by the optical demultiplexer 411 into optical signals having wavelengths λ ₁ , λ ₂ and λ ₃ , and then the respective optical-to-electrical conversion circuits are used. 311, 312 and 313 inputs.

Similarly, the wavelength-multiplexed optical signal outputted from the output optical waveguide 442 is branched by the optical demultiplexer 412 into optical signals having wavelengths λ ₂ , λ ₃ and λ ₁ , and then sent to the optical-to-electrical conversion circuits 314 and 314 , respectively. 315 and 316 inputs.

Furthermore, the wavelength-multiplexed optical signal outputted from the output optical waveguide 441 is branched by an optical demultiplexer 413 into optical signals having wavelengths λ ₃ , λ ₁ and λ ₂ , and then sent to optical-to-electrical conversion circuits 317 , 318 and λ 2 , respectively. 319 input.

In the embodiment of the present invention shown in FIG. 4, focusing on the output optical signal of the electrical/optical conversion circuit 301, this optical signal is optically transmitted along the path of optical multiplexer 401 - wavelength selection element 423 - optical demultiplexer 411. - Added to the input of the electrical conversion circuit 311.

In addition, the output optical signals of the electrical/optical conversion circuits 302 and 303 are transmitted through the optical multiplexer 401 - wavelength selection element 422 - optical demultiplexer 412 and optical multiplexer 401, respectively.
It is added to the inputs of the optical-to-electrical conversion circuits 314 and 317 through the path of - wavelength selection element 421 - optical demultiplexer 413 . In the same way, the electrical/optical conversion circuit 30
The output optical signals of 4, 305 and 306 are input to optical-to-electrical conversion circuits 312, 315 and 318, respectively, and the output optical signals of electric-to-optical conversion circuits 307, 308 and 309 are input to optical-to-electrical conversion circuits 313, 316 and 309, respectively. 319 input.

In this way, the primary switch 1 shown in FIG.
60 and the secondary switch 170, a link connection is made which is completely equivalent to the conventional broadband communication path shown in FIG.

In the embodiment of the present invention shown in FIG.
3 into an array, it is possible to suppress variations in coupling loss with the optical demultiplexer 411, and therefore the insertion loss can be kept almost constant no matter which communication path is passed. .

Also, the primary switch 160 and the secondary switch 170
The connection between the lattice switch 100 and the electrical/optical conversion circuits 301, 3 can be made using only six fiber optic cables.
By configuring optical multiplexer 401 and optical multiplexer 401 on the same module, the number of optical connectors can be reduced from three to one, thereby reducing the size of the wideband communication path. I can do it.

The effect of reducing this value becomes more pronounced as the number of lattice switches composing the primary switch 160 and the secondary switch 170 increases. For example, if the number of lattice switches belonging to the primary switch 160 is m, If the number of switches is n, link connections can be made using m+n fiber optic cables, and the number of connectors required for the lattice switches belonging to the primary switch 160, for example, is reduced from n to 1. be able to.

In the embodiment of the present invention shown in FIG. 4, a case of two-stage link connection is shown, but even when the wideband communication path is composed of multiple stages of switches, the link connection between each stage can be performed. It is clear that the invention can be applied.

Furthermore, the same effect can be obtained even in the case of a multiple link connection in which a plurality of links are used to connect grid switches belonging to different stages.

(Effects of the Invention) According to the present invention, it is possible to have good crosstalk characteristics and reduce variation in loss between each communication path, and also to realize broadband communication which is easy to downsize due to the small number of optical fiber cables. path is obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a conventional wideband communication path, and Fig. 2 is a block diagram showing an example of a conventional wideband communication path.
FIG. 3 is a block diagram showing an example of a conventional broadband communication path, and FIG. 4 is a block diagram showing an embodiment of the present invention. In the figure, 100, 110, 120, 13
0, 140 and 150 are grid switches, 301
-309 are electrical/optical conversion circuits, 311-319 are optical/electrical conversion circuits, 401, 402, and 403
is an optical multiplexer, 411, 412 and 413 are optical demultiplexers, and 421 to 429 are wavelength selection elements, respectively.

Claims (1)

[Scope of Claims] 1. At least has a primary switch constituted by i lattice switches with m inputs and n outputs, and a secondary switch constituted by n lattice switches with i inputs and j outputs. In the broadband channel, n of each grid switch belonging to the primary switch
n x i electrical/optical conversion circuits that convert the output electrical signals into n optical signals each having a different wavelength;・i optical multiplexers each having n input terminals connected to the output terminal of the optical conversion circuit; and i optical wavelength multiplexed signals output from the i optical multiplexers. , i input optical waveguides each arranged in parallel; n output optical waveguides intersecting the input optical waveguide and each arranged in parallel; Each of the n optical signals of the n-multiplexed wavelength multiplexed optical signals on the input optical waveguide is arranged at each intersection with the output optical waveguide.
After demultiplexing any one optical signal from the n-multiplexed wavelength-multiplexed optical signals on the input optical waveguide, it is distributed to each grating switch configuring the secondary switch. The i×n wavelength selection elements that are combined as multiplexed optical signals and the n i-multiplexed wavelength multiplexed optical signals output from the n output optical waveguides are respectively inputted, and i
n optical demultiplexers that separate the optical signals into n optical demultiplexers; i output optical signals of each of the optical demultiplexers are respectively input, and i
What is claimed is: 1. A wideband communication path characterized by further adding i×n optical-to-electrical conversion circuits connected to the input terminals of a grid switch with input j outputs.