AU650584B2

AU650584B2 - Fault location arrangement for digital transmission system

Info

Publication number: AU650584B2
Application number: AU29807/92A
Authority: AU
Inventors: David Anthony Frisch
Original assignee: Alcatel Australia Ltd
Current assignee: Telstra Corp Ltd; Tasman Cable Co
Priority date: 1989-08-09
Filing date: 1992-12-01
Publication date: 1994-06-23
Anticipated expiration: 2010-07-30
Also published as: AU2980792A

Description

65584 P100oiiO 2815 91 Regulation 3.2

AUSTRALIA

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ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "FAULT LOCATION ARRANGEMENT FOR DIGITAL TIRANSMISSION SYSTEM" a

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The following statement is a full description of this invention, including the best method of performing it known to us:- 2 This invention relates to digital transmission systems, in particular, though not exclusively, submarine digital transmission systems, comprising a first terminal and a second terminal each having a signal transmit means and a signal receive means, a first transmission bearer and a second transmission bearer, the first transmission bearer cu..veying signals from the signal transmit means of one terminal to the signal receive means of the other terminal, and the second transmission bearer conveying signals from the signal transmitter of the other terminal to the receive terminal of the said one terminal, each bearer having a plurality of spaced regenerators to restore the original shape of a pulse signal transmitted from a signal transmit means of a terminal.

Such transmission systems require a fault location arrangement to locate faults in remote regenerators and in sections of bearer adjacent thereto.

Techniques for locating faults are known and may comprise an arrangement in which a command signal is sent from a terminal of the system which addresses a particular regenerator. The regenerator responds with a status message or an action such as switching a laser or activating a loop-back circuit.

:These known arrangements are relatively complicated and require o S complex circuitry.

It is an object of the present invention is to provide a supervisory arrangement for initiating a loop-back at a regenerator without the need for complex circuitry. By "loop-back" is meant the regenerated signals in a regenerator that are transmitted from a terminal on one bearer, are diverted at 2,6 the regenerator onto the other bearer and are received in the receive equipment S of the same terminal. The Bit-error-ratio may then be measured and used to check the performance of the regenerator under test.

According to the invention, in a non-re-timed digital transmission system comprising a first terminal and a second terminal each of which includes a signal transmit means and a signal receive means, a first transmission bearer and a second transmission bearer, the first transmission bearer conveying signals from the signal transtit means of one terminal to the signal receive means of the other terminal, and the second transmission bearer conveying signals from the signal transmit means of the other terminal to the signal receive means of the said one terminal, each bearer having a plurality of spaced regenerators to restore the original shape of a pulse signal transmitted from a signal transmit means, a method of locating faults by diverting regenerated signals that are transmitted from a terminal on one bearer onto the other bearer to return said regenerated signals to the signal receive means of that terminal, said method including the steps of: transmitting a repetitive pattern of n bits at a predetermined line rate from the transmit means of a terminal to selectively generate a detectable signal of a predetermined frequency; detecting said detectable signal of a predetermined frequency with filter means in a regenerator, said filter means being tuned to pass said detectable signal to a diverting circuit in the regenerator; and activating said diverting circuit in the regenerator to divert regenerated Po1 signals from one bearer to the other.

s** According to a further aspect of the invention, there is provided in a nonre-timed digital transmission system comprising a first terminal and a second terminal each of which includes a signal transmit means and a signal receive means, a first transmission bearer and a second transmission bearer, the first transmission bearer conveying signals from the signal transmit means of one terminal to the signal receive means of the other terminal, and the second o transmission bearer conveying signals from the signal transmit means of the too: other terminal to the signal receive means of the said one terminal, each bearer having a plurality of spaced regenerators to restore the original shape of a pulse signal transmitted from a signal transmit means, and means for locating faults by diverting regenerated signals that are transmitted from a terminal on one bearer onto the other bearer to return said regenerated signals to the signal receive means of that terminal; wherein said means for locating faults comprises: means for transmitting a repetitive pattern of n bits at a predetermined line rate from the transmit means of a terminal to selectively generated 4etectable signal of a predetermined frequency; 4 means for detecting said detectable signal of a predetermined frequency with filter means in a regenerator, said filter means being tuned to pass said detectable signals to a diverting circuit in the regenerator; and means for activating said diverting circuit in the regenerator to divert regenerated signals from one bearer to the other.

In order that the invention may be readily carried into effect, embodiments thereof will now be described in relation to the drawings.

Figure 1 shows a block diagram of a non-returned digital transmission system.

Figure 2 shows a block diagram of an arrangement embodying the present invention to di.,'rt regenerated signals at a regeneration onto the other bearer for loop-back tests.

Figure 3 shows a further embodiment of the present invention.

Referring to Figure 1 of the drawings, the transmission system comprises two terminals A and B each of which include a signal transmit means 1 and a .signal receive means 2. The terminals are linked by a Send optical bearer 3 and a Receive optical bearer 4, over which a main data signal, having typically a 0- 600 MHz bandwidth is transmitted from the terminals. At intervals along each optical bearer are interposed four regenerators R1 to R4 and R5 to R8.

Referring to figure 2 of the drawing, the regenerator comprises an amplifier 9, a narrow band filter 10 and a loop-back switch 11 arranged to switch the regenerated signals onto the other bearer.

.In operation, in order to transmit a command signal to a selected regenerator (R1 R8) and cause it to switch into a loop-back mode, a repetitive pattern of a preselected number of bits is transmitted. This pattern may be used for testing the performance of the resulting chain of regenerators.

A pattern of n bits at a line rate of B produces a series of tones, the lowest of which is at B/n and has a relative power of 1/n. For a line rate of 591 Mbauds: 96 bits produces 6158 kHz 104 bits produces 5685 kHz A pattern length is chosen to produce a selective tone which can be passed by filter 10 at the regenerator under test to trigger loop-back switch 11.

Filter 10 may be a filter such as, for example, a crystal filter or a phase lock load detector. The bandwidth of the filter should be such that the code noise of normal data does not trigger the loop-back switch.

It will be understood that the regenerator shown in Figure 6 can be part of an electrical or an optical transmission system, and therefore amplifier 9 can be either an electric amplifier or an optical amplifier. In the case of an optical transmission system, a small part of the amplified optical signal is split off, converted in a conventional optical/electrical converter means as shown in Figure 3, and coupled into filter While the present invention has been described with regard to many particulars, it is understood that equivalents may be readily substituted without departing from the scope of the invention.

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Claims

1. In a non-re-timed digital transmission system comprising a first terminal and a second terminal each of which includes a signal transmit means and a signal receive means, a first transmission bearer and a second transmission bearer, the first transmission bearer conveying signals from the signal transmit means of one terminal to the signal receive means of the other terminal, and the second transmission bearer conveying signals from the signal transmit means of the other terminal to the signal receive means of the said one terminal, each bearer having a plurality of spaced regenerators to restore the original shape of a pulse signal transmitted from a signal transmit means, a method of locating faults by diverting regenerated signals that are transmitted from a terminal on one bearer onto the other bearer to return said regenerated signals to the signal receive means of that terminal, said method including the steps of: transmitting a repetitive pattern of n bits at a predetermined line rate from o the transmit means of a terminal to selectively generate a detectable signal of a se* S predetermined frequency; 4 oo detecting said detectable signal of a predetermined frequency with filter 0 a means in a regenerator, said filter means being tuned to pass said detectable S signal to a diverting circuit in the regenerator; and activating said diverting circuit in the regenerator to divert regenerated Ssignals from one bearer to the other. 9'ee S

2. A method as claimed in claim 1, wherein said transmission bearers are optical bearers. S

3. A method as claimed in claim 1, wherein said regenerator is part of an optical transmission system, and further comprises optical amplifier means S" wherein a small part of the amplified optical signal is split off, converted in a conventional optical/electrical converter means and coupled into a filter.

4. A non-re-timed digital transmission system comprising a first terminal and a second terminal each of which includes a signal transmit means and a signal receive means, a first transmission bearer and a second transmission bearer, the first transmission bearer conveying signals from the signal transmit means of one terminal to the signal receive means of the other terminal, and the second 4 1 1 7 transmission bearer conveying signals from the signal transmit means of the other terminal to the signal receive means of the said one terminal, each bearer having a plurality of spaced regenerators to restore the original shape of a pulse signal transmitted from a signal transmit means, and means for locating faults by diverting regenerated signals that are transmitted from a terminal on one bearer onto the other bearer to return said regenerated signals to the signal receive means of that terminal; wherein said means for locating faults comprises: means for transmitting a repetitive pattern of n bits at a predetermined line rate from the transmit means of a terminal to selectively generate a detectable signal of a predetermined frequency; means for detecting said detectable signal of a predetermined frequency with filter means in a regenerator, said filter means being tuned to pass said detectable signals to a diverting circuit in the regenerator; and means for activating said diverting circuit in the regenerator to divert oo ~regenerated signals from one bearer to the other. fee*

5. The system according to claim 4, wherein said transmission bearers are S• optical bearers,

6. The system according to claim 4, wherein said regenerator is part of an 20 optical transmission system, and further comprises optical amplifier means too wherein a small part of the amplified optical signal is split off, converted in a *0 conventional optical/electrical converter means and coupled into a filter. 0e a o.

7. A method and system substantially as herein described with reference to Figures 1 3 of the accompanying drawing. DATED THIS TWENTY-SECOND DAY OF APRIL 1994 TASMAN CABLE COMPANY PTY LTD and AUSTRALIAN OVERSEAS TELECOMMUNICATIONS CORPORATION LIMITED ABSTRACT This invention relates to submarine digital transmission systems and in par- ticular the provision of a simple supervisory system to check the performance of remote regenerators of the transmission system. According to the invention there is provided a method by which a repetitive pattern of a preselected number of bits is transmitted from a terminal on one bearer A filter (10) at the regenerator under test is arranged to pass the pre- selected bits, and triggers a loop-back switch 11' to divert regenerated signals onto the return bearer f f