Optoelectronic feedback in audio signal transmission

A new type of optoelectronic feedback system was built to simultaneously transmit the PFM (pulse frequency modulation) audio-signal from a sender to one or more receivers. In the sender, the PFM audio-signal generated by using a VCO (voltage-controlled oscillator) is converted into the optical signal by an optical transmitter and the optical transmitter output is also fed back to the VCO input through an optical receiver installed in the sender. The optoelectronic feedback is thus established to compensate for the nonlinearity of the VCO, to reduce the distortion of the received signal, and to improve the dynamic range of the PFM modulator. This new PFM system has a distortion factor of as low as 0.5% with a dynamic range of as wide as 2.0 V_p-p