JPS61242139A - Clock return control system - Google Patents

Abstract

PURPOSE:To transfer a low-speed clock obtained by giving the 1/n division to a clock extracted at a transmission/reception part of one side at the side of a nondefect transmission line to a transmission/reception part of the other side through an adjacent intermediate repeater station when a fault occurs on the transmission line and to give n-multiplication to said low-speed clock to apply it to a transmission part as a transmission clock of an original speed. CONSTITUTION:If faults occurs on the transmission lines 17 and 26, a control part 30 controls a switch part 22 to apply a clock to a transmission part 23 via a multiplier 25. Thus the clock extracted through a reception part 11 of a transmission/reception part 10 of one side at the side of a nondefect transmission line 16 is divided into 1/n by a clock divider 14 and transferred to a transmission/reception part 20 of the other side via a transfer line 18 in the form of a low-speed clock. This clock is multiplied by (n) by a multiplier 25 of the part 20 and turned into the clock of the original speed. This clock is applied to the part 23 via the part 22 as a transmission clock and the fault information, etc. are sent to a transmission line 27. Thus the speed similar to a normal transmission clock is secured for transmission of the fault information to a nondefective transmission line.

Description

[Detailed Description of the Invention] [Summary] When a transmission line failure occurs, a clock is extracted at an intermediate relay station on a healthy transmission line side opposite to the failed transmission line side, and the clock is divided into 1/H. The low-speed clock is transferred to the transmitter side, multiplied by n, and used as the transmit clock, making it possible to transfer the clock with an inexpensive configuration.

[Industrial application field]

The present invention relates to a clock return control method that extracts a clock from a healthy transmission line when a transmission line fails, and transfers the clock to a transmitter on the healthy transmission line in order to send failure information and the like.

In long-distance transmission, a plurality of intermediate relay stations are generally provided between terminal stations, and each intermediate relay station is generally equipped with the 3R functions of waveform shaping, identification reproduction, and timing extraction. In addition, it is not only the transmission line for the main signal (but also the monitoring line for transferring the operating status information of each intermediate relay station to the terminal station, the communication between terminal stations, between the terminal station and intermediate relay stations, or between intermediate relay stations). In this case, rather than using a separate line from the main signal transmission line, operating status information and credit information are superimposed on the main signal by time division, etc. It is common to transmit over lines, and it is especially often used in optical transmission systems.In such transmission systems, a clock for main signal transmission is required even when transmitting fault information etc. becomes.

[Conventional technology]

When a transmission path failure occurs, fault information is sent from the intermediate relay station to the terminal station on the healthy transmission path side. In this case, a transmission clock is required, so a clock generator is installed in each intermediate relay station in advance. A method is known in which the system is activated when failure information is sent. However, providing a clock generator at every intermediate relay station has the disadvantage that it is not economical. Therefore, the clock is extracted from the received signal on the healthy transmission line side in the opposite direction to the faulty transmission line side, and the clock is transferred to the transmitter on the healthy transmission line side, and is used as the transmission clock for sending out the fault information. The method is known.

For example, as shown in FIG. 3, a plurality of intermediate relay stations 33-1 to 33-n are arranged between terminal stations 31 and 32, and
When a transmission path 34 for transmitting data from the terminal station 32 to the terminal station 32 and a transmission path 35 in the opposite direction are provided, if a failure occurs in the transmission path at points A and B, the intermediate relay station 33-1 will: The receiving section 36 (the transmitting section is not shown) on the side of the healthy transmission path extracts the clock and transfers it to the transmitting section 37 (the receiving section is not shown) toward the terminal station 31, and the transmitting section 37 uses the clock. Fault information, etc. is sent to the terminal station 31 on the side of the healthy transmission line, and at the intermediate relay station 33-2, it is sent to the receiving unit 38 on the side of the healthy transmission line.
(The illustration of the transmitter is omitted) extracts the clock and transmits the clock to the transmitter 3.
9 (receiving unit not shown), and the transmitting unit 39 uses its clock to transmit fault information, etc. to the terminal station 32 on the side of the healthy transmission path.
It is to be sent to. Therefore, even without providing a clock generator, it is possible to return the clock extracted from the received signal to the transmitting side and send out fault information, etc.

[Problem that the invention seeks to solve]

Even if the receiving section 36 for one transmission path and the transmitting section (not shown) in each intermediate relay station, for example, the intermediate relay station 33-1, are configured in the same unit, the transmission for the other transmission path is Since the parts 37 and 37 are not configured in the same unit, when the clock return method is applied, there is a
This requires a connection configuration for clock transfer. Furthermore, since a high-speed optical transmission system uses a high-speed transmission clock of several GHz or more, the clock extracted by the receiving section 36.38 is transferred to the transmitting section 37.39 at an electrical signal level. This method has disadvantages in that it is complicated and requires the use of expensive connectors.

An object of the present invention is to transfer extracted clocks with an inexpensive configuration.

[Means for solving problems]

The clock return control method of the present invention will be explained with reference to FIG. A frequency dividing means 7 is provided for dividing the frequency of the clock extracted by 1/n and transmitting the frequency, and a multiplying means 8 is provided for multiplying the frequency by one week and adding the transmission clock to the transmitting section 6 of the other transmitting/receiving section 4. , when there is a fault in the transmission line at the position indicated by the x mark, the receiving section 5 of one of the transmitter/receivers 4 on the side of the healthy transmission line in the opposite direction from the fault point in the intermediate relay station 3 adjacent to the fault point. The frequency of the extracted clock is divided by 1/n by the frequency dividing means 7, the divided low-speed clock is transferred to the other transmitting/receiving section 4, and the low-speed clock is multiplied by one week by the multiplying means 8 and sent to the transmitting section. 6
This is the transmission clock.

[Effect]

The clock extracted by the receiving section 5 is divided into 1/
By dividing the frequency by n, it can be transferred as a low-speed clock, and the mounting structure for transferring the clock from one transmitting/receiving section to the other transmitting/receiving section is simple, and inexpensive connectors and the like can be used. In the other transmitter/receiver section,
By multiplying the low-speed clock by n using the multiplier 8, it can be applied to the transmitter 6 as a transmission clock at the original speed.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram of an embodiment of the present invention, showing main parts within an intermediate relay station. In the same figure, 10.2
0 is a transmitting/receiving section, 11.21 is a receiving section, 12.22 is a switching section, 13.23 is a transmitting section, 14.24 is a frequency divider, 15.
25 is a multiplier, 16.17.26.27 is a transmission line, 18
．． 28 is a clock transfer line, and 30 is a control section.

The receiving section 11.21 receives the signal transmitted from the terminal station or the intermediate relay station via the transmission path 16.26, extracts the clock from the received signal, identifies and reproduces the data, and switches the switching section 12.22. The clock and data are transmitted through the unit 1
The transmitter 13.23 sends the transferred data to the transmission path 17.27 using the transferred clock as a transmission clock. In the optical transmission system, the transmission lines 16, 17 and 26, 27 are composed of optical fibers, etc., and the receiving section 11.21 is equipped with a photoelectric conversion section that converts the received optical signal into an electrical signal, and the transmitting section 11. The sections 13 and 23 are provided with an electro-optical conversion section that converts electrical signals into optical signals.

The switching section 12.22 is controlled by the control section 30, and is normally switched to transfer the clock and data from the receiving section 11.21 to the transmitting section 13.23, as described above. The control section 30 also has a fault monitoring function, and controls the switching section 12.22 in the event of a fault in the transmission path, as well as controlling the transmission of fault information.

For example, if a failure occurs on the transmission line 17.26 side, the control unit 30 controls the switching unit 22 to switch so that the clock via the multiplier 25 is applied to the transmitting unit 23. As a result, the clock extracted by the receiving section 11 of one of the transmitting/receiving sections 10 on the healthy transmission line 16 side is divided into 1/n by the frequency divider 14.
The low-speed clock is transferred to the other transmitter/receiver 20 via the transfer line 18 as a low-speed clock, and this low-speed clock is multiplied by n by the multiplier 25 of the other transmitter/receiver 20 to become the clock at the original speed. It is added as a transmission clock to the transmitter 23 via the transmission clock, and fault information etc. are sent to the transmission path 27 in accordance with this transmission clock.

Also, if a failure occurs on the transmission line 16 or 27 side, the control unit 30 controls the switching unit 12 to switch the multiplier 15
The clock is switched to be applied to the transmitter 13 via the transmitter 13. As a result, the clock extracted from the received signal via the transmission line 26 by the receiving unit 21 of the other transmitting/receiving unit 20 is frequency-divided by 1/n by the frequency divider 24, and is transferred to the one transmitting/receiving unit as a low-speed clock by the transfer line 28. This low-speed clock is multiplied by n by the multiplier 15 to become the original speed transmission clock, which is added as a transmission clock to the transmission section 13 via the switching section 12, and fault information etc. is transmitted according to this transmission clock. 17.

When there is a failure in the transmission path, the □clock transferred from one transmitter/receiver to the other transmitter/receiver is
Since it is a low-speed clock whose frequency is divided by /n, the transfer line 18
．． 28 can use a coaxial line, and its connector can be an inexpensive SP connector or the like. For example, in an optical transmission system, the transmission clock is 1.
For 6 GHz, if n=4, the frequency divider 14.2
Since the frequency is divided by 1/4 by 4 to obtain a 400 MHz clock, the implementation becomes simpler and cheaper than when the 1.6 GHz clock is directly transferred.

〔Effect of the invention〕

As explained above, in the present invention, when there is a failure in the transmission path, the intermediate repeater 3 connects the receiving units 11.2 to 11.2 through the healthy transmission path.
1, the clock extracted from the signal received at frequency divider 14
．． The low-speed clock is divided by 1/n by frequency dividing means 7 such as 24, and the low-speed clock is transferred to the transmitter 13.23 side, and the transfer line 18.28 transfers the low-speed clock. This makes it possible to use coaxial lines, etc., which simplifies the mounting structure compared to the case of transferring high-speed clocks, and allows the use of inexpensive connectors. Furthermore, since a low-speed clock is transferred, distortion of the clock waveform is less likely to occur, and there is an advantage that there is no adverse effect on the operation of the transmitting section 13, 23.

In addition, since the transmitting unit 13.23 receives a transmitting clock obtained by multiplying the low-speed clock by n by the multiplier 8 such as the multiplier 15.25, it has the same speed as the normal transmitting clock and transmits fault information etc. to the healthy transmission line side. Can be sent.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a block diagram of a conventional example. 1.2 is a terminal station, 3 is an intermediate relay station, 4 is a transmitting/receiving section, 5 is a receiving section, 6 is a transmitting section, 7 is a frequency dividing means, 8 is a multiplying means, 10
．． 20 is a transmitting/receiving section, 11.21 is a receiving section, 12.22 is a switching section, 13.23 is a transmitting section, 14.24 is a frequency divider, 1
5.25 is a multiplier, 16.1? , 26.27 is the transmission line,
18.28 is a transfer line.

Claims (1)

[Claims] A plurality of intermediate relay stations (3) are provided on the transmission path between the terminal stations (1, 2), and when a failure occurs in the transmission path, the failure occurs at an intermediate relay station adjacent to the failure point. In the clock return control method, a clock is extracted from a received signal from a healthy transmission line side in the opposite direction to the intermediate relay station, and the clock is transferred as a transmission clock for sending information to the healthy transmission line side. Frequency dividing means (7) for frequency dividing the clock extracted by the receiving section (5) of one transmitting/receiving section (4) to 1/n in (3), and a transmitting section (6) of the other transmitting/receiving section (4) and a multiplier (8) for adding a clock multiplied by n to the other clock, and when the clock returns, the low-speed clock obtained by dividing the clock extracted by the receiving section (5) to 1/n by the frequency dividing means (7) is provided. The low-speed clock is multiplied by n by the multiplier means (8) and transmitted to the transmitter/receiver section (8).
6) A clock return control method characterized in that it is added as a transmission clock.