Patent ID: 7245828

Claim:
A method for an optical transmitter to automatically determine an extinction ratio of an optical signal by modulating the duty cycle of the optical signal, the method comprising the following: an act of measuring an average normal optical power, the normal optical power being the optical power emitted by the electro-optic transducer under conditions in which the duty cycle of the optical signal is between a bias high and bias low modulation condition; an act of modulating the duty cycle of the optical signal emitted by the electro-optic transducer to the bias high condition in that the length of time that the optical signal is at the optical high power level in the eye diagram is greater than the length of time that the optical signal is at the optical low power level in the eye diagram; an act of measuring an average bias high optical power, the bias high optical power being the optical power emitted by the electro-optic transducer during the act of modulating the duty cycle of the optical signal emitted by the electro-optic transducer to the bias high condition; an act of modulating the duty cycle of the optical signal emitted by the electro-optic transducer to the bias low condition such that the length of time that the optical signal is at the optical low power level is the eye diagram is greater than the length of time that the optical signal is at the optical high power level in the eye diagram; an act of measuring an average bias low optical power, the bias low optical power being the optical power emitted by the electro-optic transducer during the act of modulating the duty cycle of the optical signal emitted by the electro-optic transducer to the bias low condition; and an act of deriving an extinction ratio for the optical signal based on the measured average normal optical power, the measured average bias high optical power, and the measured average bias low optical power.