Raman Distributed Fiber Optic Temperature Sensors And Their Spatial Resolution Study

In recent years, sensor measurement technique of distributed optical fiber is one of the hot questions in the sensor measurement field which this researching task belongs to. Due to the limitation of traditional sensor to supervise a spot, under some particular environment situation to supervise the large quantity position at the same time, it can not supervise and measure the buildings effectively. Otherwise, sensor measurement technique of distributed optical fiber can achieve it with ease.The thesis researches Raman Distributed Optical Fiber Temperature Sensor systems through analyzing its measuring principle. In base of the analysis of main technology index of the system and the power's size of signal, we complete the system construction design and develop an experimental system. Through a number of temperature experiments, we complete the mission of present stage.In this system we improve the ratio between signal's power and noise's power together with the sensitivity of the system by a new temperature signal demodulating method. Spatial resolution of the system is one of the most import technology indexes of the systems. It defines the distributing degree of measuring system. Because of the contradiction between the spatial resolution and the signal's power, to achieve a high spatial resolution is very difficult. In all reports about this kind of system up to now, the highest spatial resolution is 2m. However, in some environment this index still can not achieve the requirement. Therefore, the emphasis of this thesis is to approve the spatial resolution. The deep analysis's results express that the spatial resolution is distinguished by three time constants, however the real decision of the spatial resolution is the size of the signal's power. As a result, improving the spatial resolution must sacrifice the signal's power, at the same time the responding time of the optical detector and the velocity of the A/D card also must satisfy the certain term.Increasing the ratio between the signal's power and noise's power is the basic method to improving the spatial resolution. This system decreasing the noise's power using high insulation optical filter and low noise amplifier. On the other hand, through software and hardware method we consumedly increased the system's work stability.We achieve the temperature measuring which spatial resolution is 10m on 5km optical fiber through the system that adopts an 180mW pulse laser and PIN optical detector. Although there is still a distance between this experimental result and the target, we believe that we will get a better result by adopting EDFA optical amplifier and APD optical detector. Now, a new experimental system is being constructed and the research work of the next stage will soon open.