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Based On B-otda Technology Of Long Distance Fire Alarm Systems

Posted on:2012-06-06Degree:MasterType:Thesis
Country:ChinaCandidate:L ChangFull Text:PDF
GTID:2208330332986816Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Compared with other temperature sensors, the distributed fiber temperature sensor based on brillouin has the unparalleled advantage in the long-range warning fire detection.However,the conventional Brillouin distributed optical fiber sensor usually use the centralized amplification way,which resulting in a wide range low SNR (signal to noise ratio) region in the end of the fiber, so it seriously affecting sensing performance.In this paper, a novel fire alarm system based on the BOTDA(Brillouin Optical Time Domain Analysis) technology is proposed. The system first use the bi-directional Raman amplification to compensate the low SNR in the sensor's fiber back-end area; The simplex codes was introduced to Brillouin distributed optical fiber sensors to achieve high-precision measurement in the whole optical fiber. In this paper, The detected probe waveshape has been simulated by using the probe-pump coupled equations combined with Raman. The experimental has been demonstrated, the experimental results are in good agreement with the theoretical analysis;This paper also describes the SNR gain theory for S-Transform in BOTDA system, The experimental exploration of the BOTDA with Raman amplification and simplex codes has been demonstrated. The result shows that simplex codes could effectively enhance the sensor's signal to noise ratio. The author has done a great deal of research on three aspects: extending the sensing distance,achieve the high-precision measurement and the practical research,The detailed work of the thesis is listed as follow:(1) This paper summarizes the development process of distributed optical fiber sensing system and research status.(2) This article summarizes various BOTDA products's performance all of the world.(3) The BOTDA system based on Raman amplification has been analysed,the result shows that bi-directional Raman amplification could effectively compensate the signal's transmission loss and improve the precision of the system.(4) The experimental exploration of the BOTDA with Raman amplification and semiconductor optical amplifier(SOA) has been demonstrated. The experimental results are in good agreement with the theoretical analysis. And the results show that, a temperature resolution of 1 oC was achieved over a sensing distance of 49.6 km with a 40 m spatial resolution.(5) The BOTDA system based on S-Transform has been recounted thoretically.The experimental exploration of the BOTDA with simplex codes has been demonstrated. The result shows that Simplex code can effectively enhance the sensor's signal to noise ratio.(6) On the basis of the experiment, the BOTDA sample was excogitated , and we also educe the sample machine test results.
Keywords/Search Tags:Optical Fiber Sensor, BOTDA, Raman Amplification, Simplex coding
PDF Full Text Request
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