Nortel Networks Corporation

Darrell Smith

Edward J Whittaker

Paul Wilson

An optical receiver arrangement comprises a phase locked loop incorporating a voltage controlled oscillator whereby the loop can be matched in frequency to a received signal frequency. A frequency detector associated with the loop produces an output comprising first or second pulses indicative of whether the loop frequency is above or below the received signal frequency. A control circuit determines a time averaged measure of difference between the loop frequency and the received signal frequency, and issues a loss of lock alarm if this averaged difference exceeds a predetermined value.

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Bishops Stortford, United Kingdom

Darrell Smith