Patent ID: 8611744

Claim:
An apparatus, comprising: a first circuit including an oscillator and a filter, the oscillator supplying light having a frequency which sweeps at a sweep rate from a first one of a plurality of frequencies to a second one of the plurality of frequencies, a first portion of the light being provided to the filter which filters the first portion of the light to provide a filtered output having an intensity peak at a third one of the plurality of frequencies; a second circuit configured to receive a second portion of the light from the first circuit on a first input and an optical signal on a second input, said optical signal having a fourth one of the plurality of frequencies, the second circuit configured to provide an output signal in response to the second portion of the light and the optical signal, the output signal being indicative of said fourth one of the plurality of frequencies; and a third circuit configured to provide a control signal based on, at least, the filtered output of the first circuit, the output signal of the second circuit, and the sweep rate, wherein the control signal is configured to control a corresponding one of a plurality of characteristics associated with said optical signal wherein the third circuit is configured to determine a time period by measuring time from the intensity peak to the detection of the output signal, an offset frequency determined by multiplying the sweep rate by the time period, said fourth one of the plurality of frequencies being determined by adding the offset frequency to the third one of the plurality of frequencies of the intensity peak.