JPS60137198A - Synchronous communication system of time-division optical exchange - Google Patents

Abstract

PURPOSE:To attain synchronization with an optical space switch output in a time-division optical exchange which uses an optical space switch by setting a guard time and adding a signal for synchronism in front of a light data signal. CONSTITUTION:The additional signal 20 for synchronism is set before the data signal to be sent to one time slot and the guard time 22 is set before said signal 20 and after the data signal 21. The optical space switch functions as the time-division switch when each light signal has the guard time 22 even if there is variance in the time slot position of each light signal before the signal is inputted to the light space switch. Therefore, the data signal 21 can be restored correctly.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a switching circuit network for communication, and particularly relates to a communication switching network. This invention relates to a synchronous communication system for a time-division optical switch that exchanges optical signals using a two-optical space switch.

[Prior art]

Conventionally, this type of optical exchange using an optical space switch has been configured to handle baseband signals, so it has had the drawback of not being able to handle time-division multiplexed optical signals.

On the other hand, in order to realize the exchange of time-division multiplexed optical signals using an optical space switch, it is essential that the time slot positions of each input signal match at the input position of the optical space switch. Due to variations in the distances from optical signal output circuits located at different locations to each input terminal of the optical space switch via each optical fiber group, it is difficult to exactly match the above time slot positions. Met. Also, when receiving the optical space switch output, due to the variation in the time slot position,
It was difficult to maintain synchronization with the optical space switch output.

〔the purpose〕

According to the present invention, a guard time is set so that no optical signal passes through the optical path at the time when the optical switch is about to switch, and a synchronization signal is added to the beginning of the optical data signal. It is an object of the present invention to provide a time-division optical converter that solves the drawbacks and can handle time-division multiplexed optical signals.

[Structure of the invention]

In order to achieve the above object, the time-division optical switching system according to the present invention has a time-division optical signal sequence in which each time slot consists of a guard time, an additional signal for synchronization, a data signal, and a guard time. The received signal is received by an optical space switch whose time point corresponding to the guard time corresponds to the guard time when switching is performed in the time-division cycle, and the optical output of the optical space switch, and by an additional signal for synchronization of each time slot of the optical output. The present invention is characterized in that it has an optical receiving circuit that receives a data signal following the periodic additional signal while maintaining synchronization.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which optical signal transmission circuits 1 to 4, optical fiber cables 11 to 14 connecting the optical signal transmission circuits 1 to 4 and an optical space switch 9, respectively; Optical space switch 9, optical signal receiving circuit 5
8, optical fiber cables 15 to 18 that connect the optical space switch 9 and each of the optical signal receiving circuits 5 to 8, respectively, and a switch control circuit 10 that controls the optical space switch 9.

FIG. 2 is an example of a timing chart showing the configuration of optical signals passing over the optical fiber cables 11 to 15 in the above block diagram. One frame is a time slot'r
It is time-divided into 1, T2, T, 3...
In one time slot, there is an additional signal 20 for synchronization.
and data signal 21, and additional synchronization signal 2
A guard time 22 is set before 0 and after the data signal 21.

Next, the operation of this embodiment will be sequentially explained with reference to FIGS. 1 and 2. The optical signal transmitting circuit 1 transmits a data signal (dl) including signal content a1 in time slot T1, signal content b1 in time slot T2, signal content C in time slot T3E, respectively. Similarly, from the optical signal transmission circuit 2, the signal content d1 is sent to the time slot T1.
Signal content e1 time slot) T3 in time slot T2
A data signal (d2) containing the M content f is transmitted to
Also, from the optical signal transmission circuit 3, a data signal (d3) containing signal content g in time slot TI, signal content h1 in time slot T2, and signal content 1 in time slot T3
is sent. Each of these optical signals passes through the optical fiber cables 11 to 13 and reaches the optical sky 1' and the J1 switch 9, but at this time, the position of the time slot depends on the clock synchronization difference of each optical signal transmission circuit. , and the delay time difference within the optical fiber cable.

When the optical space switch 9 is switched, the guard time 22 of each optical signal passes through the switch 9.
If so, even if there is the above variation, the optical space switch 9
functions as a time division switch. The signal (d5) of the optical fiber cable 15 in FIG. 2 is the signal after passing through the optical space switch 9, and at time slot T1,
This is an example in which signal a is selected in time slot 7) T2, signal e is selected in time slot 7) T3, and signal i is selected in time slot 7) T3. Since the degree of the above-mentioned variation differs for each time slot, the additional synchronization signal 20 added before the data signal 21 allows the optical signal receiving circuits 5 to 8 to perform tie-ins.
Re-synchronize every b, 2/g. In this way, the optical signal receiving circuit 5i-i:, data signal contents a, e, and i can be correctly restored.

〔effect〕

As explained above, the present invention adds an additional signal for synchronization and a guard time before the data signal sent to the l time slot, and further adds a guard time after the data signal, so that the data signal is input to the optical space switch. This has the effect of enabling time-division optical exchange using an optical space switch, regardless of variations in the time slot positions of each optical signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an example of a timing chart during switching in FIG. 1. 1 to 4: Optical signal transmitting circuits 5 to 8: Optical signal receiving circuit 9: Optical space switch lO2 Control circuits 11 to 18: Optical fiber cable 20: Additional signal for synchronization 21: Data signal 22: Guard time TJ to T3 time Slot numbers a to 1: Data signal content Patent applicant NEC Corporation Figure 1

Claims (1)

[Claims] A time-division optical signal sequence consisting of a guard time, an additional signal for synchronization, a data signal, and a guard time in the order of l time slots is input, and the guard time is the point at which switching is performed in the above-mentioned time division period. A corresponding optical space switch receives an optical output from the optical space switch, synchronizes the received signal with an additional synchronization signal for each time slot of the optical output, and synchronizes the following data signal with the periodic additional signal ζ. 1. A synchronous communication system for a time-division optical converter, characterized in that the time-division optical converter has an optical receiving circuit that receives data while holding the signal, and the time-division optical signal series can be synchronized every time slot.