Research on the fiber dispersion and compensation in large-scale high-resolution broadband frequency-modulated continuous wave laser measurement system

Abstract

The influence of a fiber dispersion calibration interferometer on the measurement results for a largescale high-resolution broadband frequency-modulated continuous wave (FMCW) measurement system was studied. A model was constructed to simulate the influences of fiber dispersion on the measurements when using a frequency sampling method that corrects the tuning nonlinearity. The results indicated that a broadband external cavity tunable laser, in comparison with a semiconductor laser, causes linear variations in the measurement results because of the effect of the fiber dispersion in the calibration interference path for large-scale high-resolution measurements, and these variations decreased the resolution of the measurements. A method that combines chirp slope calibration and phase compensation to reduce the effects of the fiber dispersion was proposed. A gauge block with a height difference of 200 μm at a distance of 2.43 m was measured during the experiments. Before calibrating the fiber dispersion, the frequency spectrum showed false peaks, and it was difficult to distinguish the peaks of the targets. After compensating for the dispersion, the peaks of the targets could be clearly distinguished, and a height difference of 199.6 μm was measured. Using this model and the method to compensate for the dispersion will provide a reference for large-scale high-resolution broadband FMCW laser measurements.

High-Precision Silicon-Integrated Frequency-Modulated Continuous Wave LiDAR Calibrated Using a Microresonator

“…The final ranging result is positively related to the length of the long optical fiber, and the accuracy and stability of the long optical fiber also directly affect the accuracy of the ranging. However, the ranging range of this solution is limited by the length of the auxiliary MZI fiber when the measurement distance exceeds half of the length of auxiliary MZI fiber; the Nyquist sampling theorem is not satisfied during resampling, and if the fiber of auxiliary MZI is too long, it will introduce greater dispersion and increase the volume of the system . In addition, some research also cooperates with the gas cell to assist the measurement. , The gas cell has the characteristic of absorbing at a specific wavelength position, and the absorption peak position is stable.…”