In this paper based on the optical cable,a method was presented that increasing a Fiber Bragg Grat ing together with the optical cables,which could be used for monitoring the cable real-time temperature.Finiteelement method was used to establish the temperature field model of optical cables,and using a tunable laser as a system source,engraving many the same center wavelength of the fiber Bragg grating in a fiber,that was to say using the whole grating as a system temperature sensor.In Optical cable lines when the temperature is abnormal,the reflected grating center wavelength will shift.By detecting the center offset of the reflected light could determine the size of the grating temperature change.Grating at different positions reflected optical signals need different time.By detecting and calculating the interval time of reflected light,the location and the temper ature of the grating whose temperature has changed will obtain.Experimental results showed that grating tempera ture sensitivity rose at 11.4 pm/℃.The deviation between the measured temperature and the actual temperature was within 3% range.

A new kind of strain measurement Hollow-core Photonic Crystal Fiber (HCPCF) Fabry-Perot (F-P) interferometer sensor is presented. One end of the HCPCF is fused with the single-mode fiber to form the reflecting surface 1. The other end of HCPCF completely collapses to form the reflecting surface 2 by the electrode discharge in the welding machine. So the new F-P interferometer sensor with HCPCF cavity is constituted. The experimental results show that the strain sensitivity of the sensor cavity length of 2 mm at room temperature is 3.1 nm/με, the linearity is 0.9992 and limit cavity length change is 3827.3 nm. In the range of 0~150°C, the change of cavity length is about 0.17 μm. Theoretical and experimental results show that the new sensor has a simple fabrication process, high strain sensitivity, low temperature sensitivity and no hysteresis.

Aiming at mine collapse,we design a Fiber Bragg Grating(FBG) sensor network to monitoring the mine.Firstly finite element analysis is made to the mine model to get the instable point in real-time.Then specially designed FBG sensors are installed at the instable points of the mine.When an instable point of the mine is abnormal,the reflected grating center wavelength will change.According to the center shift of the reflected light,the security situation of the mine can be well mastered.Experimental results show that the measurement accuracy of the FBG sensor can reach ±0.01%.

A Fiber Bragg Grating (FBG) is increased in the optical cables, which can be used for monitoring the cable real-time temperature. Finite-element method is used to establish the temperature field model of optical cables. The tunable laser was used as source, and some fiber Bragg gratings with same center wavelength were used as system temperature sensor. In optical cable lines when the temperature is abnormal, the reflected grating center wavelength will shift. By detecting the center wavelength offset of the reflected light, the size of the grating temperature change can be determined. Grating at different positions reflected optical signals needs different time. By detecting and calculating the interval time of reflected light, the location and the temperature of the grating whose temperature has changed will be obtained. Experimental results show that grating temperature sensitivity reaches 11.4 pm/℃. The deviation between the measured temperature and the actual temperature is within 3% range.

The finite element method was used to build the mathematical model of temperature field for upper limb,according to characteristic of the human body.It provides a theoretical basis to the fiber Bragg grating(FBG) used to measure body temperature.Designed and implemented a new FBG body temperature monitoring system.The sin-gle-wavelength laser pulse was modulated,and it can form ultra-narrow pulse laser.The high-speed optical inspection system can detect the reflection grating spectra.The ARM processing system obtained the body temperature by analyses the power spectral characteristics.Experimental results show that the system can detects the temperature of the dynamic around the(28~48)℃,measurement accuracy of 0.1℃,response rate of 10s,the system with high preci-sion,fast response,can be applied to the human body temperature monitoring.

A distributed temperature sensor based on fiber grating of cable is presented in this paper.It can monitor temperature of cable real-time.Based on equation of heat conduction,finite-element method is used to analyze temperature field of cable and provides witness for monitor temperature.The fiber grating is not electrification,has good ability of anti-jamming and radioresistance,it is suit to as the temperature sensor in high-tension electricity environment.In 20～100 ℃,the central wavelength of FBG vary with the temperature has fine linearity.The standard thermojunction temperature sensor and fiber grating temperature sensor are used to do contrast experiment.The experiment result indicates that the curve of time-temperature has good follow character and temperature difference less than 1 ℃.So it can accurately measure temperature of cable.

A novel distributed sensor system based on Fiber Bragg Grating (FBG) sensing technology is proposed. In huge project,there are often one hundred positions to be monitored. If these positions are divided into several groups and every group has four fiber Bragg gratings with the same wavelength,it can implement one hundred fiber Bragg gratings on one fiber. If the temperature of one point is varied,the largest temperature of the group can be obtained. The system will alarm if this temperature is over set value. Based on the theory analysis,temperature experiments of different wavelength have been done. In 10～110°C,the central wavelength of FBG varying with the temperature has fine linearity. It has been seen in experiments that the system has the characteristics of the high measured precisions,good reliability and low cost in distributed multimetering.

This paper presents a new type of distributed Fiber Bragg grating (FBG) sensing system based on a tunable pulse laser. The system has 500 gratings with same centre wavelengths of 1550nm and the spacing of every grating is 3m. All gratings have been packaged and 27m delay lines are inserted between every two adjacent gratings. The scanning periodic time of tunable pulsed laser is 0.25s; the scanning range is 1545~1555nm; the laser pulse line width is 0.18nm. If the grating temperature was constant, only the 1550nm light was reflected back. But with temperature change, the grating central wavelength changed and the corresponding light pulse was reflected back. The light signals are converted to voltage pulses by the photoelectric detector and sampled by high-speed acquisition card at the 500Msps sampling rate. The data processing system send out the voltage signals to control laser and compares these voltage signals with those sampled signals. Program will calculate the offset which linear corresponding to the gratings temperature change. In addition, reflected optical signals of different positions need different time, and the time interval of adjacent grating is 200ns. By detecting and calculating the interval time of reflected light, the location and the temperature of the grating whose temperature has changed will obtain. Experimental results showed that grating temperature sensitivity rose at 11.4 pm/. The deviation between the measured temperature and the actual temperature is within 5% range. This system not only can monitor the temperature, but also can determine the location. It can meet monitoring hundreds or even thousands of different locations simultaneously. Therefore it has broad application prospects.

针对一维偏振光的干涉问题，从更为广泛的二维偏振光干涉模型入手进行分析，推 导出了近轴条件下二维偏振光干涉场强的分布表达式.分析表明：干涉条纹不仅与三光束空 间位置有关，而且与光场的偏振方向有关.对一维偏振光干涉，只要两偏振片的偏振化方向 之间的夹角＜45°就可看到清晰的干涉条纹.