Pharad’s Dither-Free Bias Controller is a compact circuit for OEM applications that provides accurate and highly stable bias voltage control of optical modulators. As the bias point of the modulator drifts over time, the Bias Controller automatically adjusts the bias voltage to maintain its set point. Non-dither based control of the modulator bias voltage ensures unwanted dither tones do not impact link performance.


The Bias Controller allows for the direct mounting of the optical modulator onto the small footprint circuit board and can be used in conjunction with both periodic and non-periodic modulator transfer functions. Users can select a range of modulator bias voltages via an RS-232 interface in addition to the more conventional quadrature bias point of the modulator’s transfer function characteristic.