GB2285192A

GB2285192A - Network surveillance

Info

Publication number: GB2285192A
Application number: GB9325005A
Authority: GB
Inventors: Christopher Michael Purse
Original assignee: Northern Telecom Ltd
Current assignee: Nortel Networks Ltd
Priority date: 1993-12-07
Filing date: 1993-12-07
Publication date: 1995-06-28
Also published as: GB9325005D0

Abstract

An arrangement for transmitting alarm signals generated at one end of an optical fibre telecommunications link to the other end of the link, which optical link includes an independent end-to-end supervisory channel 10b, the arrangement including means 14b at a line terminating equipment 12b for detecting failure or degradation of optical signals received at the terminating equipment, means for generating an alarm signal in response to detection of said failure or degradation of the optical signals and means for transmitting said alarm signal to the remote end of the link via the independent supervisory channel. <IMAGE>

Description

NETWORK SURVEILLANCE This invention relates to an arrangement for network surveillance across a transmission interconnection between two ends having respectively different network surveillance systems.

There are instances in telecommunications where the two ends of a transmission link, e.g. an optical fibre line transmission system, are administered by different telecom operators. In most cases where there are different network surveillance systems at each end a compatible telemetry system for gathering alarms from the remote end will not be available.

It is known for transmission systems to incorporate, in addition to the normal traffic and signalling channels, a channel reserved for endto-end supervisory communication. In wired systems such a channel is often referred to as an 'order wire'.

According to the present invention there is provided an arrangement for transmitting alarm signals generated at one end of a telecommunications link to the other end of the link via an independent supervisory channel incorporated in the link.

An embodiment of the invention will now be described with reference to the accompanying drawing which is a block schematic for an optical fibre transmission link.

In the drawing optical fibre transmission paths 10a, 10b are set up between two line terminating equipments (LTE) 12a, 12b. Each LTE has connected to it a respective network surveillance system 14a, 14b. It is assumed for the purpose of the present explanation that the LTEs and the network surveillance systems are different, though so far as the LTEs are concerned they will have an interworking compatibility. A network surveillance system may comprise a personal computer (PC) accessing, via a polling controller, various parts of the respective LTE and, via an auxiliary data channel, the link to the remote LTE (and any intervening repeaters etc). Fault conditions in the LTE and the link will generate alarm signals which are detected by the PC and acted upon by the operator as required.However, the criteria used by the network surveillance system and the manner in which the alarm signals are generated may not be compatible with those of the different network surveillance system used by the operator of the remote LTE. Depending on the nature and location of the fault condition X detected by one network surveillance system the other network surveillance system may not detect the same fault.

In the present invention each LTE is provided with means for sending a 'reverse transmit alarm' to the remote end via the network surveillance system if the link fails at the remote end.

This will allow both ends of a transmission system, particularly an optical system, to be monitored by each end even if there are different and incompatible network surveillance systems used at each end. It will also enhance SCADA systems which are only monitored at one end.

Because SCADA uses a polling protocol, if the polling does not reach the remote station then the remote station will not report its alarms. If an optical signal to the remote end fails then the remote end will not receive any polls so it will not be able to report the failure. This invention solves this problem by providing an alarm to the SCADA interface.

When the received optical signal fails or degrades to an error rate worse than 1 in 103 then the optical line terminating equipment (LTE) sends a 'reverse transmit' alarm back to the remote end via overhead bits in the optical signals.

The 'reverse transmit' alarm is mapped into the alarm message sent to the network surveillance system so that if there is a failure of the optical signal at one end, e.g. at 'X' in the example illustrated then å 'receive line signal fail' alarm is reported to the network surveillance system 14b, and a 'reverse transmit' alarm is reported to the network surveillance system 14a.

In the case where there are intermediate stations, e.g.

repeaters, the stations up to the failure will report 'reverse transmit' alarms and from this the network operator will be able to deduce where the failure occurred.

Claims

CLAIMS:

1. An arrangement for transmitting alarm signals generated at one end of a telecommunications link to the other end of the link via an independent supervisory channel incorporated in the link.

2. An arrangement for transmitting alarm signals generated at one end of an optical fibre telecommunications link to the other end of the link, which optical link includes an independent end-to-end supervisory channel, the arrangement including means at a line terminating equipment for detecting failure or degradation of optical signals received at the terminating equipment, means for generating an alarm signal in response to detection of said failure or degradation of the optical signals and means for transmitting said alarm signal to the remote end of the link via the independent supervisory channel.

3. An arrangement for transmitting alarm signals generated at one end of an optical fibre telecommunications link to the other end of the link substantially as described with reference to the accompanying drawing.