A predistortion type equi-path linearizer designed for radio-on-fiber system

A predistortion type equi-path linearizer is created for a radio-on-fiber system based on W-CDMA; its main benefit is its simple optical circuit configuration. Experiments show that the phase of the third order intermodulation components of the laser diode is delayed by around 90 degrees from those of RF amplifier. To our knowledge, this is the first report to describe the phase delay. To counter this delay we place an additional phase shifters. The proposed design places a pre-amplifier between the linearizer and a laser diode for lower power consumption and better insertion gain at the linearizer. The experimental and calculated results agree well, and an over 20dB improvement in third order intermodulation components is obtained for the bandwidth of 60MHz. The linearizer works well in the temperature range of 10°C to 40°C with a simple control circuit.