Patent ID: 7646990

Claim:
A circuit for detecting optical failures in a passive optical network (PON) wherein digital burst data transmitted by an optical transmitter is monitored by a photodiode, said circuit comprising: a power determination unit coupled to the photodiode for providing measurements of an output optical power of a high logic level and a low logic level of said digital burst data during ON times of the optical transmitter and for providing a measurement of an output optical power during OFF times of the optical transmitter, wherein the power determination unit comprises a first power determination unit and a second power determination unit for providing measurements of the output optical power during ON and OFF times of the optical transmitter, respectively, and further comprising a switch coupled to the photodiode for switchably coupling the photodiode to either the first power determination unit or to the second power determination unit; and a logic unit coupled to the power determination unit and being responsive to said measurements for generating control and calibration signals.