Detection of optical circulator crosstalk based on signal modulation

A novel method based on piezoelectric transducer (PZT) modulation for detecting the crosstalk of optical circulator has been demonstrated. In the experiment, the lightwave emitted from a low-noise single-frequency laser passed through the circulator, reflected on the surface of the PZT, and returned to the circulator again. The PZT can modulate the frequency of the lightwave reflected on it due to the Doppler effect. Then the crosstalk of the circulator is obtained by measuring the induced optical difference frequency based on a difference-frequency detection technology. The results show that this method is very effective in detecting weak crosstalk of circulator.