JPH05102932A - Optical atm switch - Google Patents

Abstract

PURPOSE:To provide an optical ATM switch which uses an optical switch as a switch element and has a variable wavelength function applied to only one of the incoming end outgoing links. CONSTITUTION:An optical switch consists of plural veriable wavelength converter switches 1 provided at the incoming link side, the matrix switch parts 2 which receive the outputs of of the switches 1, and plural optical buffer memories 10 including the optical cell delay parts 11 and the fixed wavelength selecting parts 12 and receive the outputs of the parts 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical ATM switch using an optical switch as a switch element, and more particularly to a structure of a switch for accommodating a plurality of input / output highways.

[0002] In ATM exchange, cells from each incoming highway may go out to the same output highway at the same time. Therefore, it is necessary to provide a buffer, and its construction method is an important issue. In addition, AT aiming at further capacity increase
Optical implementation of the M-switching scheme is about to be carried out. Above all, the wavelength division multiplexing technique of light has been used.

[0003]

2. Description of the Related Art FIG. 7 is a block diagram showing a configuration example of a conventional device. In the figure, reference numeral 1 denotes a variable wavelength conversion switch provided for each of m inputs, which converts an input signal into a wavelength of λ1 to λn according to a route. Reference numeral 2 denotes an m × m matrix switch unit that receives the output of the variable wavelength conversion switch 1 and is a 1 × m switch 2
a is composed of m pieces.

Reference numeral 3 denotes an optical coupler provided for every m paths,
Reference numeral 4 is an optical fiber delay line coupled with the optical coupler 3. The optical fiber delay line 4 takes in signals of all wavelengths from .lamda.1 to .lamda.n and circulates them. During that time, a predetermined wavelength is selected and output. Therefore, the optical coupler 3 and the optical fiber delay line 4 function as a buffer for temporarily holding data.

Here, the matrix switch section 2 is designed not to send signals of the same wavelength to the same route in duplicate. As a characteristic of light, even if signals having different wavelengths are mixed, each wavelength can exist independently without being affected. Reference numeral 5 is a variable wavelength selective switch that sequentially selects and outputs signals of a predetermined wavelength from the signals sent from the optical coupler 3.

The wavelength conversion switch 1 and the wavelength selection switch 5 described above use wavelength conversion elements and wavelength selection elements using semiconductor lasers, and control the wavelength by changing the injection current.

In the thus-configured apparatus, each input optical cell is converted into a desired wavelength by the variable wavelength conversion switch 1, and is distributed to a desired output highway by the 1 × m switch 2a. Then, it is temporarily stored in the optical fiber delay line 4 provided for each outgoing highway. The variable wavelength selective switch 5 selects an optical cell having a desired wavelength from the signals held in the optical fiber delay line 4 and outputs it.

[0008]

In the conventional apparatus, a plurality of cells are stored by wavelength multiplexing in the optical fiber delay line 4 for one cell (for example, n wavelengths are used to store n cells). For this reason, the wavelength conversion switch 1 and the wavelength selection switch 5 need both a variable wavelength function and a high-speed switching function, which causes a problem that the device becomes expensive.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an optical ATM switch in which a variable wavelength function is required to be provided only on either an incoming link or an outgoing link. ..

[0010]

FIG. 1 is a principle block diagram of the first invention, and FIG. 2 is a principle block diagram of the second invention. The same parts as those in FIG. 7 are designated by the same reference numerals. In FIG. 1, 1 is a plurality of wavelength conversion switches provided on the incoming link side, 2 is a matrix switch unit that receives the outputs of these wavelength conversion switches 1, and 10 is an optical cell delay unit that receives the outputs of the matrix switch unit 2. 11 is a plurality of optical buffer memories including a fixed wavelength selection unit 12.

In FIG. 2, reference numeral 20 denotes a plurality of wavelength conversion switches provided on the incoming link side and having fixed output wavelengths, 2 denotes a matrix switch unit for receiving the outputs of these wavelength conversion switches 20, and 30 denotes the matrix switch. It is a plurality of optical buffer memories that receive the output of the unit 2 and that include an optical cell delay unit 31 and a variable wavelength selection unit 32.

[0012]

(First Invention) Each input optical cell is converted to a desired wavelength by the variable wavelength conversion switch 1 (variable by n wavelengths to store n cells) and desired by 1 × m switch 2a. It is distributed to Node Highway. Then, the fixed wavelength selecting unit 12 of the optical buffer memory 10 outputs the signal to a predetermined optical fiber delay line of the optical cell delay unit 11. (Second invention) Each input optical cell is converted by the fixed wavelength conversion switch 20 into a predetermined wavelength pre-assigned for each link, and is distributed to a desired output highway by the 1 × m switch 2a. Then, the optical buffer memory 30
The variable length selection unit 32 (m wavelength division for m highway) outputs the signal to a desired optical fiber delay line of the optical cell delay unit 31.

As described above, according to the present invention, it is possible to provide an optical ATM switch in which the variable wavelength function is provided only on either the incoming link or the outgoing link.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 3 is a configuration block diagram showing a main part of an embodiment of the first invention. The figure shows a configuration example of the optical buffer memory 10. The optical buffer memory 10 is composed of an optical cell delay unit 11 and a fixed wavelength selection unit 12. The optical cell delay unit 11 includes n-1 optical fiber delay lines 11a.
(1 cell). This optical cell delay unit 1
1, the optical fiber 13 is spirally wound as shown in FIG. 4, and one winding forms one optical fiber delay line 11a. The signal from the fixed wavelength selection unit 12 is the optical fiber delay line 11a and the next optical fiber delay line 11
It is connected to a.

The fixed wavelength selecting unit 12 receives an input signal and branches a signal including the respective wavelengths λ1 to λn into n branches, and a signal of a wavelength branched by the brancher 12a. It is composed of n fixed wavelength selective switches 12b for selecting a signal of a specific wavelength. Since the fixed wavelength selective switch 12b on the optical fiber exit side does not enter the optical fiber delay line 11a, the number of optical fiber delay lines 11a is n-1.

The optical buffer memory 1 configured as described above
At 0, the optical signal input from the input unit
a, and is branched into n branches by the branching device 12a. A fixed wavelength switch 12b is attached to each branch, and selects a signal of a specific wavelength from the signals of λ1 to λn and sends it to the optical cell delay unit 11.

The optical cell delay unit 11 has a structure as shown in FIG. 4, and takes in the signal of the wavelength sent from the fixed wavelength selective switch 12b and sends it out to the exit side. For example, a cell entering at the wavelength of λ2 is selected by the fixed wavelength switch 12b provided second from the exit and enters the optical fiber delay line 11a. Then, after being delayed by one cell, it is output to the output highway side.

In the embodiment shown in FIG. 3, the fixed wavelength selective switch 12b comprises λ1, λ2 and λ2 in order from the optical fiber exit side.
.. .lambda.n is selected. With such an arrangement, adjacent wavelengths come close to each other, and so-called crosstalk may occur in which adjacent cells leak. This crosstalk increases as the spacing between adjacent wavelengths decreases. In order to avoid such an influence of crosstalk, adjacent wavelengths may be separated by a certain length or more.

FIG. 5 is a block diagram showing the essential parts of another embodiment of the first invention. The configuration is the same as that of FIG. The difference is that the fixed wavelength selective switches 12b adjacent to each other
That is, the wavelengths of the cells selected in step 1 have a certain distance or more. For example, λ4 fixed wavelength selective switch 1
Both sides of 2b are λ7 and λ1.

Generally speaking, this is as follows. Assuming that the number of links is m and the buffer capacity is n, the selected wavelength interval between adjacent fixed wavelength selective switches 12b is n /
Make it more than m. In this way, by separating the adjacent wavelength selective switches 12b by a certain wavelength interval or more, it is possible to prevent the occurrence of crosstalk.

FIG. 6 is a constitutional block diagram showing a main portion of an embodiment of the second invention, showing a constitutional example of the optical buffer memory 30. The same parts as those in FIG. 2 are designated by the same reference numerals. The optical buffer memory 30 includes an optical cell delay unit 31 and a variable wavelength selection unit 32. Optical cell delay unit 31
Is composed of n-1 optical fiber delay lines 31a (one cell). The configuration of this optical cell delay unit 31 is shown in FIG.
As shown in.

The variable wavelength selection unit 12 receives the input signal and branches the signal including the respective wavelengths λ1 to λn into n branches, and the signal of the wavelength branched by the brancher 32a. It is composed of n variable wavelength selective switches 32b that select a variable wavelength signal. Since the variable wavelength selective switch 32b on the optical fiber exit side does not enter the optical fiber delay line 31a, the number of optical fiber delay lines 31a is n-1.

The optical buffer memory 3 thus configured
At 0, the optical signal input from the input unit
a, and is branched into n branches by the branching device 12a. A variable wavelength switch 32b is attached to each branch, and selects a signal of a specific wavelength from the signals of λ1 to λn and sends it to the optical cell delay unit 31.

The optical cell delay unit 31 has a structure as shown in FIG. 4 and takes in the signal of the wavelength sent from the variable wavelength selective switch 32b and sends it to the exit side. For example, if you want to delay a cell that came in with a wavelength of λ2 by 2 cells before outputting it to the exit highway,
The variable wavelength selective switch 32b may be selected.

[0025]

As described above in detail, according to the present invention, when either the wavelength conversion switch or the wavelength selective switch does not have a high speed and variable function, a plurality of optical fiber delay lines are used to provide an optical buffer memory. By configuring
The characteristics required for the wavelength conversion switch or wavelength selective switch can be relaxed (either of the variable wavelength functions is good),
It greatly contributes to the performance improvement of the comparison and exchange system using the optical ATM switch. As described above, according to the present invention, it is possible to provide an optical ATM switch in which the variable wavelength function is provided only on either the incoming link or the outgoing link.

[Brief description of drawings]

FIG. 1 is a principle block diagram of a first invention.

FIG. 2 is a principle block diagram of a second invention.

FIG. 3 is a configuration block diagram showing a main part of an embodiment of the first invention.

FIG. 4 is a diagram showing a configuration example of an optical cell delay unit.

FIG. 5 is a configuration block diagram showing a main part of another embodiment of the first invention.

FIG. 6 is a configuration block diagram showing a main part of an embodiment of the second invention.

FIG. 7 is a block diagram showing a configuration example of a conventional device.

[Explanation of symbols]

 1 Variable Wavelength Conversion Switch 2 Matrix Switch Section 10 Optical Buffer Memory 11 Optical Cell Delay Section 12 Fixed Wavelength Selection Section 20 Fixed Wavelength Conversion Switch 30 Optical Buffer Memory 31 Optical Cell Delay Section 32 Variable Wavelength Selection Section

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04Q 3/52 Z 9076-5K

Claims (3)

[Claims] 1. A plurality of variable wavelength conversion switches (1) provided on an incoming link side, a matrix switch section (2) for receiving outputs of the variable wavelength conversion switches (1), and the matrix switch section (2). An optical ATM switch including a plurality of optical buffer memories (10) each of which includes an optical cell delay unit (11) and a fixed wavelength selection unit (12). 2. When the number of links is m and the buffer capacity is n, the fixed wavelength selection is performed so that the selection wavelength interval is n / m or more between the fixed wavelength selection switches (12b) of the fixed wavelength selection unit (12). The optical ATM switch according to claim 1, wherein a switch is arranged. 3. A fixed wavelength conversion switch (20) provided on the incoming link side and having a fixed output wavelength.
A matrix switch section (2) for receiving the outputs of these fixed wavelength conversion switches (20), and an optical cell delay section (31) and a variable wavelength selecting section (32) for receiving the outputs of the matrix switch section (2). An optical ATM switch including a plurality of optical buffer memories (30).