International Standard Electric Corporation

Stc, Inc

Northern Telecom Europe Limited

Thomas Oswald

Ian J Hirst

Patrick S Kelly

Stephen E Hill

Robert Murphy

Alan J Jeal

A method of locating an intermittent electrical fault in an optical undersea transmission system, comprises measuring the time difference between two signals emanating from the fault along two different routes of the system. In one embodiment one of the signals is a voltage transient and the other signal is an optical error signal created in a repeater adjacent the fault as a result of surge protection in the repeater responding to the electrical fault, and in another embodiment both signals are optical signals, once again emanating from adjacent repeaters and caused by the effect of the electrical fault on the adjacent repeaters. It is envisaged that such a transmission system could be permanently provided with apparatus to detect such a fault in which synchronized counters are permanently running and frequently re-set and which stop in response to error signals being received from a fault when it occurs.

Fault location

In an optical transmission system, particularly a submerged system, a line finding system is provided which, in the event of a fault somewhere along the system, enables the remaining operative lines or paths to take over the traffic and thus 'steer around' the fault. The laser sources of the submerged repeaters and switched by electrical selection at their input using failed clock or a supervisory signal to achieve the switching.

Optical transmission systems

An optical undersea telecommunications system has a main cable (1) which branches (BU1) near a landfall to two separate stations. Each branch (71,81) supplies half the current of the main cable (1) for powering the regenerators. In the event of a fault in a branch (e.g. 81) caused by an anchor or fishing gear, the operations branch (71) regenerator (e.g 11) can supply the full current (I) via a zener diode power feed and bypass circuit and high voltage diodes (D1,D2) automatically prevent leakage of current back to the fault.

Power feeding submarine telecommunications systems

A method and apparatus for optical transmission of an analog signal whose statistical properties approximate 'white noise' including a repeater having an optical source, such as a laser, and signal processing means including a quadratic device having a quadratic characteristic arranged to receive the analog signal and provide an output signal to intensity modulate the source, the output signal containing terms which are proportional to the analog input signal and second order terms proportional to the square of the analog input signal, the second order terms being eliminated by a bandwidth filter.

Optical transmission system and method

An impulse noise source in a bidirectional submerged communications system is positionally located by detection apparatus at one end of the system which measures the time interval between the same impulse arriving twice at the one end of the system, firstly, via a shorter or faster path in the system (either the incoming path to the one end, or a reference frequency band in the incoming path) and, secondly, via a longer or slower path in the system (either the go path from the noise source, a go/return distant loop and the incoming path, or another frequency band in the incoming path). Group delay distortion of the system affects the location accuracy and is equalized by networks in the detection apparatus.

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Dartford, United Kingdom

Thomas Oswald