Linearity enhancement of linear frequency-modulated DFB semiconductor lasers based on smoothing algorithms.

Area of Science:

• Optics and Photonics
• Metrology and Measurement

Background:

• Frequency-modulated continuous-wave (FMCW) light detection and ranging (LiDAR) is crucial for high-precision ranging and velocity measurements.
• Accuracy in FMCW LiDAR is fundamentally limited by the linearity of laser frequency modulation.
• Conventional predistortion methods struggle with nonlinearity correction at sweep transition points.

Purpose of the Study:

• To introduce a novel smooth predistortion iterative algorithm for FMCW LiDAR.
• To overcome the limitations of traditional predistortion techniques in correcting modulation nonlinearity.
• To enhance the overall accuracy and imaging quality of FMCW LiDAR systems.

Main Methods:

• Development of a frequency-modulation nonlinear correction system utilizing a field-programmable gate array (FPGA).
• Implementation of a smooth predistortion iterative algorithm allowing for increased convergence iterations.
• Experimental validation of the algorithm's performance in reducing laser frequency nonlinearity.

Main Results:

• Laser frequency nonlinearity reduced from 3.3% and 1.3% to 0.022% after 2700 iterations.
• Residual nonlinearity (1-r²) reached as low as 8.458×10⁻⁷.
• Ranging accuracy achieved a maximum error of 9 mm.
• Image entropy improved from 1.9585 bits (conventional) to 1.4063 bits (proposed), indicating superior image quality.

Conclusions:

• The proposed smooth predistortion iterative algorithm effectively minimizes modulation nonlinearity in FMCW LiDAR.
• The enhanced linearity leads to significantly improved ranging accuracy and superior imaging quality.
• This technique offers a robust solution for applications demanding high-precision distance and velocity measurements.