Amplitude detection scheme for optical transmitter control

摘要

An amplitude control scheme for a high bit rate digital optical transmitter is disclosed. The data to be transmitted by the laser is pulse-width modulated by a low frequency signal. The pulse-width modulated signal is applied to the laser via a laser driver and to a mark density reference generator. The magnitude of the low frequency components from the mark density reference generator is a signal indicative of the desired amplitude of the laser light pulses. A back-face photodiode converts a portion of the laser light into an electrical signal, the magnitude of the low frequency portion thereof being a signal indicative of the actual amplitude of the laser light pulses. The actual amplitude of the laser light pulses is compared to the desired amplitude and the laser driver output amplitude may then adjusted to compensate for variations in the laser performance.