An exemplary photo-electronic frequency multiplier (100) includes an intervening optical signal generator (10), a pair of photo-electronic conversion circuits (21, 22), a differential amplifier circuit (30), and a signal processing circuit (40). The intervening optical signal generator includes a light source (11), a first mirror (12), a first reflector (14), a second reflector (15), an optical phase modulator (16), and a second mirror (13). The intervening optical signal generator is for generating two intervening optical signals. Each photo-electronic conversion circuit is for converting one intervening optical signal into an electronic signal. The differential amplifier circuit is for multiplying the difference between the two electronic signals and outputting an amplifying signal. The signal processing circuit is for processing the amplifying signal to generate a signal having a plurality of frequency multiplications.