Managing non-linear signal distortion in photonic time-stretch systems

Other conference contribution, 2007

Photonic time-stretch systems effectively boost the bandwidth of existing real-time oscilloscopes by temporally stretching a piece of a signal using dispersive optics. The stretch is, however, not perfect – the very same dispersion that actually enables the stretch also introduces signal distortions. Although the optical system is linear, the dispersive propagation and the modulator response introduce harmonic signal distortion when considering the signal from electrical input to electrical output. In this talk, two methods developed for the compensation of non-linear as well as linear distortions are presented. The first method recovers the original signal by calculation of the optical phase at the detection point followed by numerical back-propagation to the modulation point whereas the second method iteratively retrieves the signal using the Gerchberg-Saxton algorithm, which frequently is used for phase retrieval in free-space and diffraction optics. To enable fast numerical propagation, which is required for both methods, a very efficient numerical propagation technique specialized for photonic time-stretch systems is also presented.