Nonlinearity suppression method for optical frequency scanning based on the Phenomenological model

The frequency-scanning interferometer’s (FSI) precision relies much on its tunable laser source. The external cavity laser diode (ECDL) is an ideal choice for FSI due to its narrow linewidth and high tuning speed. However, ECLD exhibits nonlinearity during optical frequency scanning produced by the inherent hysteresis effect in the piezo-electric transducer (PZT) ceramic. The interference signal hence becomes nonstationary, and the phase extracting of the interference signal causes errors. To address this challenge, this study proposes a novel method based on the asymmetric Prandtl–Ishlinskii (API) model for nonlinearity suppression of optical frequency scanning. By taking the linear driving signal and instantaneous optical frequency of the ECLD as input and output data of the model respectively, then, the hysteresis model can be obtained by using the API modelling method. The model’s inverse then can be employed as a feedforward controller to suppress the nonlinearity of the optical frequency scanning. In this case, a corrected waveform of the PZT driving signal is implemented instead of linear driving signal to suppress the nonlinear frequency scanning of the ECDL. The results of simulation validate the effectiveness of the proposed suppression method with root-square-mean-error (RMS) of 1.6357×10-6 GHz.