In one embodiment, an electro-absorption modulator receives an optical light from an optical light source and outputs a modulated optical signal. The electro-absorption modulator includes a bias voltage used to set a predetermined modulation performance and an output power of the electro-absorption modulator. A controller measures a photocurrent generated by the electro-absorption modulator and uses the photocurrent as a reference to automatically control the bias voltage of the electro-absorption modulator to maintain the predetermined modulation performance and the output power of the electro-absorption modulator when a detuning change occurs between the electro-absorption modulator and the optical light source throughout the lifetime of transmitters based on an EML device.