Patent ID: 7309853

Claim:
A method for controlling a bias voltage to an avalanche photodiode that generates a photo current corresponding to an optical input power incident to the avalanche photodiode, the method comprising steps of: detecting the photo current, estimating the optical input power based on the detected photo current and the bias voltage applied to the avalanche photodiode, comparing the estimated optical input power with a preset power, calculating, when the estimated input optical power exceeds the preset power, a revised bias voltage based on a difference between the estimated optical input power and the optical input power in the last iteration, adjusting the bias voltage based on the calculation of the revised bias voltage, and iterating steps of the detection, the estimation, comparison and the calculation, wherein the revised bias voltage is changed from the bias voltage in the last iteration by the difference between the estimated input optical power and the input optical power in the last iteration multiplied by a constant.