Time-Stretched Femtosecond Lidar Using Microwave Photonic Signal Processing

TL;DR

This paper presents a real-time femtosecond lidar system with high resolution and update rate, utilizing all-optical microwave signal processing to encode and measure displacement through frequency variations.

Contribution

It introduces a novel all-optical processing method for femtosecond lidar, enabling real-time ranging with high precision and adjustable dynamic range.

Findings

Achieved 7.64 μm standard deviation over 15 mm range

Demonstrated 19.10 μm mean error over 15 mm range

Attained 37.73 μm standard deviation over 45 mm range

Abstract

A real-time ranging lidar with 0.1 Mega Hertz update rate and few-micrometer resolution incorporating dispersive Fourier transformation and instantaneous microwave frequency measurement is proposed and demonstrated. As time-stretched femtosecond laser pulse passing through an all-fiber Mach-Zehnder Interferometer, where the detection light beam is inserted into the optical path of one arm, the displacement is encoded to the frequency variation of the temporal interferogram. To deal with the challenges in storage and real-time processing of the microwave pulse generated on a photodetector, we turn to all-optical signal processing. A carrier wave is modulated by the time-domain interferogram using an intensity modulator. After that, the frequency variation of the microwave pulse is uploaded to the first order sidebands. Finally, the frequency shift of the sidebands is turned into transmission change through a symmetric-locked frequency discriminator. In experiment, A real-time ranging system with adjustable dynamic range and detection sensitivity is realized by incorporating a programmable optical filter. Standard deviation of 7.64 {\mu}m, overall mean error of 19.10 {\mu}m over 15 mm detection range and standard deviation of 37.73 {\mu}m, overall mean error of 36.63 {\mu}m over 45 mm detection range are obtained respectively.