In this study, a low-cost, small-volume, and high-precision system for detecting the object fracture location based on the Time-of-Flight (ToF) was proposed. Furthermore, ToF has been used in fiber ranging compared with traditional ToF applications. The basic principles of ToF and optical fiber end reflection were introduced, after which the experimental results and errors under different working conditions were examined and a weighted average algorithm to improve the accuracy of the system were proposed. The system measured total distance with an accuracy of better than 5 mm and a standard deviation of 2.04 mm using a weighted average reliability estimate. Ultimately, two system improvement schemes were proposed, providing new design ideas for the structural fracture detection system design of space vehicles such as aircraft and missiles.
KEYWORDS: Laser stabilization, Bragg cells, Signal to noise ratio, Control systems, Field programmable gate arrays, Sensors, Optical tweezers, Telecommunications, Semiconductor lasers, Laser systems engineering
Levitated microspheres have enabled a wide variety of precision sensing applications which have caught great attentions in recent years. Optical tweezers technology is one of the most important methods of microspheres levitation. The stability of laser power directly affects the microspheres levitation and the precision of the measurement. This paper discusses the major factors of power stabilization in semiconductor laser. A PID-controlled model is used to control the feedback on the laser. The system mode is established after the analyzing of the characteristic of the model parameters. The experiment is demonstrated with a commercial semiconductor laser. With the external power stabilization module a 16dB laser power stability control is achieved at the relaxation oscillation, and the long-term stability is improved from 3% to 0.4%.
In this paper, the gradient force and scattering force of two kinds of different sinusoidal modulated Gaussian beams (SMGBs(n=2), SMGB (n=4)) and Gaussian beam (Gb) are analyzed, and their ability to capture particles are studied. It is found that sinusoidal modulated Gaussian beams have multiple stable capture positions at the focal plane than Gaussian beam. Under the same circumstance, Monte Carlo stochastic simulation method is used to simulate the tendency characteristics of particles under the effect of gradient force and scattering force, which verifies the theoretical analysis results. Therefore, the research results of this paper have certain guiding significance in the experiment and application of multi-position optical tweezers.
The environmental noise in interferometric fiber optic gyroscopes (IFOGs) has a significant impact on the self-noise and angle random walk (ARW) at 0-100Hz, the bandwidth commonly used in applications. The stability of the structure affects mostly bandwidths larger than 10Hz, while the airflow in the environment mainly affects that lower than 20Hz. The self-noise in a well-fixed structure and a nonwind room is experimentally demonstrated as 1.3441×10-8 rad/s/√Hz and 2.3896 ×10-8 rad/s/√Hz, 9.08dB and 9.23dB lower than that with environmental noise, respectively, at 100Hz in the 9-km IFOG. This proves that it is essential to avoid environmental noise for the use and testing of high-precision IFOGs.
Nonreciprocity is the main contribution of drift error in fiber optic sensors based on Sagnac interferometer, such as the fiber optic gyroscope. When the sensor has to suffer from wide range of temperature, thermal nonreciprocity becomes the most important one required to overcome for it to retain similar performance over all application condition. In this paper, thermal nonreciprocities induced by both pure temperature and thermal stress in the Sagnac interferometer are analyzed respectively. First we deduce the expressions of nonreciprocities in form of phase error of the Sagnac interferometer’s fiber coil, induced by pure temperature and thermal stress respectively. Then a FEA model of such a fiber coil is build up, based on which pure temperature nonreciprocity and thermal stress nonreciprocity are investigated in detail, and their numerical values are also calculated. Finally an experimental system is set up to verify the numerical results and the corresponding errors of the system is measured, which shows good agreement to the simulation value. At the end of this paper, we discuss some methods for reducing the thermal nonreciprocity in the fiber coil, some of which are proposed for the first time.
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