Abstract
A scheme of frequency sweep linearization of semiconductor lasers using a feed-back loop based on amplitude-frequency response is demonstrated in this paper. The beat frequency signal is obtained by self-heterodyne detection. The frequency changes are converted to the envelope of beat frequency signal after amplitude-frequency response. The active frequency sweep linearization is realized by feeding envelope deviations back to the drive currents of the lasers by a feedback loop. A simulation model is built to verify this scheme by Simulink. This scheme does not need high-performance, expensive lasers, complex linearization or tedious post-processing processes, which are of great significance for related applications.
Highlights
Light detection and ranging (LiDAR) is a kind of radar working in optical band
The active frequency sweep linearization is realized by feeding envelope deviations back to the drive currents of the lasers by a feedback loop
We propose a new frequency discrimination scheme, the frequency variation of beat frequency signal is converted into amplitude variation, and the envelope signal is used to represent the frequency modulation nonlinearity
Summary
Light detection and ranging (LiDAR) is a kind of radar working in optical band. According to the working waveform, LiDAR can be divided into pulse LiDAR and frequency-modulated-continuous-wave (FMCW) LiDAR. The linearity and bandwidth of frequency sweep for light sources are key parameters for high-precision ranging. Researchers have proposed to characterize the nonlinearity of frequency modulation with self-heterodyne detection and realize the linearization of slow frequency modulation by an optoelectronic feedback loop [3]. Based on this scheme, an optoelectronic phase-locked loop (PLL) was added to optoelectronic feedback loop to realize frequency stabilization [4]. The frequency sweep linearization based on the phase-locked loop technology mentioned above has high precision, but it has high requirement for laser line width and complex circuit. Simulation results show that the frequency modulation linearization is carried out effectively in this scheme
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