Study Of Fiber-optic Sensor Model Based On The Optical Feedback Self-Mixing Effect In Semiconductor Lasers

Semiconductor laser self-mixing interference technique and optical sensing technology is the modern surveying in the field of advanced technology. They have their own advantages and disadvantages. On the one hand, self-mixing interference technology has some advantages of Louis-ray collimation, simple frame, large measuring range, high accuracy and low-cost. However, the signal is weak, difficult to measure, requiring high experimental conditions and poor anti-interference ability. On the other hand, optical sensing technology has some advantages of strong anti-interference ability, flexible, widely useful, non-invasive and remote monitoring can be realized. However, the technology's accuracy is not high, complex structure, the follow handle of signal is complex. In this article, semiconductor laser self-mixing interference technique applied to optical fiber sensing technology. A new type of sensing method is explored.Optical fiber sensor is divided into optical fiber parts and coupling parts. The method of geometrical optics optical has been used to analysis of optical in optical fiber part. The method of optical transmission scattering matrix has been used to analysis phase information of transmission signal in coupling part. The detected of Sensor signals, the traditional detection method is to transmit the signal phase information through filtering, amplification, A/D conversion, computer analysis to obtain measurement information. Complicated structure and slow-paced, self-mixing interference technique was adopted, after filtering, phase information of transmission signal detect electronic signal method to analysis, or acquisition waveform image into computer software to analysis. Simply and fatly Detection is the significant advantage of this new method.There are two analyses methods of self-mixing interference effect, one is exactly Solved the rate equation established by Lang and Kobayashi, get output frequency and intensity of light expression. Another is introduction F-P cavity model, use of laser resonator stability conditions when calculating the theoretical formula of bright feedback. In this paper using F-P cavity model to do theoretical research. It can be understood intuitively and simple calculation. In this paper, using this model, we has been derived the equation of output phase and the output power of the phase-mixing interference signal.As the optical transmission of phase information is the performance of outside cavity round-trip time of light, but round-trip time of light and the output power of the beat-wave frequency of self-mixing interference signal has determine relationship between the function, so the relationship of optical transmission of phase information and output power of the beat-wave frequency has been established. The changes in the external environment (changes of tested physical) is the direct factors of leading the changes of optical transmission phase information, thus indirectly established the relationship of tested physical and mixed-signal output frequency. By measuring the beat-wave frequency of output power can be measured the information of tested physical, established a complete theoretical model of self-mixing interference effect of the introduction of fiber-optic sensor.Using MATLAB software to simulate the theory can verify the correctness of the theory, simulation mainly to set some special conditions of temperature and pressure change process, using MATLAB software to calculate the beat-wave frequency of output power of self-mixing interference signal changes in these processes, Simulation results show that this method can predict the changing direction and changing speed of temperature or pressure. By simulating the output power of the beat-wave frequency relationship of temperature and pressure, calculate the scope of application of this method and the measurement accuracy. Temperature measurement range is from -50℃to 350℃,measuring accuracy is 0.78℃/Hz, pressure measurement range mainly in 104 N magnitude, measurement accuracy is 47.8N/Hz.Using MATLAB to simulate temperature or pressure changes in the spectrum chart, spectrum composed by a number of frequency lines, the center frequency value is the same as the value before we simulate, can accurately reflect the beat-wave frequency of output power. It can be seen from the simulation results, this new sensing method is correct in theory, if this approach is applied to the actual sensor measurements, it mast has the following advantages:optical fiber sensor's structure is more simple than conventional, the output power waveform that is direct reflected measurement information, measuring accuracy is higher. Now fiber-optic temperature sensor measurement accuracy reach 10-1℃magnitude, in this paper, measuring accuracy reach 10-2℃magnitude, application fields is broader, universal fiber optic temperature sensor measurement range is 0℃-100℃, in this paper, measurement range is-50℃-350℃.Greatly increased the measuring range of temperature;and simplified structure makes the overall cost lower.