Study On Optimization Of Long Distance BOTAR Sensing System

With the development of modern measuring technology，optical fiber sensors havereceived more and more attention. Long distance distributed optical fiber sensor,especially the distributed optical temperature/strain sensors based on Brillouinscattering, has attracted more and more researcher because of its incomparableadvantages. Brillouin optical time domain analysis (BOTDA) has extensive applicationprospects in the power transmission cables, oil field, mine, bridges and other facilities.However, researchers used front-end centralized amplification in tradition BOTDA,which limits the sensing length. In order to optimize sensing distance. In order tooptimize sensing distance, this paper study the BOTDA based on optical pulse codingand distributed amplification of random laser. Main content of this paper includes:After that, this paper introduces the basic theory of Brillouin scattering in fiber andBrillouin scattering spectrum. Then I introduce the transport theory of temperature andstrain of BOTDA. After simulation, we get the temperature and strain characteristics ofBrillouin frequency shift, and experiment confirm the theory.Then this paper introduces the current research situation of random laser at homeand abroad. Then we had build the random laser experiment system, measure therelationship between random laser output power and pump laser output power and theability of long distance transmission of random laser. We experimental provedinsensitive to random laser temperature characteristics, realized a novel long distancetemperature sensor based on the random laser.Then we introduce the random laser amplifier system in the traditional Brillouinoptical time domain. We use the unilateral backward pump which can compensate pumpconsumption. After the numerical simulation, we can see sensing distance significantlyprolong because of the introduction of random laser. Meaning time we introduce theSimpson code, measure the relationship between the the S matrix of order L and thesignal-to-noise ratio according calculation, experiment confirmed the system SNRsignificantly increased after we used optical pulse code. Through these two technologies,we extend the sensing distance, improve the system signal-to-noise ratio. The experiment shows100km sensing distance can be achieved with±4mspatialresolution for long distance BOTDA system.We developed the third generation of brillouin optical time-domain analysis systemprototype, reduced the chassis volume to4U. System achieved35km sensing distanceand20km spatial resolution. We also develop a corresponding software, the softwarecan automatic control program and provide friendly man-machine interface.Through research：the BOTDA system based on distributed amplification ofrandom laser and optical pulse coding achieves the sensing distance of100km andspatial resolution of±4m. The system can meet the requirements of long distance ofsensing. It can be used in mine, oil field, etc. And this find provides methods andexperience for future study.