Frequency modulated continuous wave (FMCW) laser interferometry is very sensitive to optical path drift, and a small length drift will lead to a great measurement error in the ranging result. In order to improve the anti-interference ability of the system and realize the large-scale, high-precision absolute distance measurement, the influence of environmental vibration on the frequency-modulated continuous wave laser ranging is analyzed, and a vibration error compensation method based on the superposition of the reverse frequency sweep signal is proposed. Simulation and experimental results show that this method can effectively improve the spectrum offset, distortion and broadening of the measurement signal caused by the optical path drift caused by vibration. Within the measurement range of 43m, the system's ranging resolution and measurement stability have been significantly improved after vibration error compensation. The measurement resolution is very close to the theoretical value, and the measurement standard deviation is stable within 9μm. The method proposed in this paper can realize the compensation of optical path drift without real-time measurement of vibration, and improve the anti-interference ability of large-scale FMCW laser ranging system without increasing the system complexity.
Fiber Bragg Gating (FBG) is widely used in the distributed and in-situ measurements of strain and temperature such as structural health monitoring and vibration detection. However, the low interrogation speed of FBG limits its application of many conditions. In this work, a novel ultrafast FBG interrogation method is proposed using a micro-resonator based broadband Kerr frequency comb (soliton microcomb, SMC) of which 3 or 5 independent optical modes are employed to interrogate a FBG sensor. The proposed method has the efficiency tens of times over conventional methods and even can be implemented using only analog circuit because only a few simple calculations is included in the deriving process. To assess the feasibility and performance of the proposed method, related influencing factors and several parameters were detailed analyzed, and it was also compared with the conventional methods under different signal to noise rates (SNR). We demonstrated continuous heating experiment (with mean square error 0.624 pm) and high-frequency vibration measurement experiment (10 kHz) with an ultrafast FBG interrogator prototype featuring ultrafast rates up to 300 MHz based on a ~50 GHz-repetition-rate SMC. All the analysis, simulation and experiments reveal the splendid advantages of simple construction, compact and ultra-efficient of the proposed ultrafast interrogating method that highlights the prospects of this method with future in various application fields such as uhf vibration measurement.
Dispersive interferometry ranging with optical frequency comb (OFC) has shown great advantages in distance metrology for its simple structure, high accuracy and the ability to resist disturbance. In this paper, the principle of optical frequency comb dispersive interferometry ranging is analyzed theoretically, and various data processing methods or system improvements proposed by researchers are summarized. The resolution, precision, none-ambiguity range and other parameters of dispersion interference ranging systems are analyzed quantitatively and qualitatively. According to the analysis, the shortcomings of current methods are pointed out and the possible solutions are provided. At last, the prospects of instrumentation and application in the future are also given.
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