Photonic Fractional Fourier Transformation Based on Discrete-Frequency Processing

Photonic fractional Fourier transformation (FRFT) based on discrete-frequency processing is proposed to overcome the limitations of processing latency, resolution, and tunability. Typical applications of FRFT, such as de-chirp processing, separation of two linear frequency modulated waveforms (LFMWs) in fractional domain and filtering of a LFMW from a noisy background, are experimentally demonstrated. The operation bandwidth and spectral resolution are 4 GHz and 60 MHz, respectively. Both the phase and amplitude can be measured by the proposal without relying on complex algorithms, while the processing latency is close to the minimum delay required in the FRFT. All optical devices employed in our system shows great potential in integration.