DFB Fiber Laser Sensors

The performance of optical fiber sensor has been increasingly improved in pace with the rapid development of optical fiber sensor technology recently. Various physical values can be measured, such as, the sound field, electric field, pressure, temperature, velocity, acceleration, etc. Additionally, it is also can meet the challenges which are unavailable with the existing measurement technology. The optical fiber sensor demonstrated a unique predominance in both confined room and strong electromagnetic interference or high-voltage environment. Moreover, with the fiber grating writing technology gradually mature, The sensor, which is based on fiber grating technology, has become a hot research topic in the optical sensing field.This thesis studies the basic theory of DFB (Distributed FeedBack) fiber lasers and its sensing applications. Firstly, DFB fiber lasers had been researched theoretically. The theoretical calculation and analysis based on the coupled mode theory includes the simulation of the optical field distribution in DFB fiber laser, the relationship between the pump power and emitted light intensity of DFB fiber laser, the threshold pump of DFB fiber laser and the gain of the light intensity in DFB fiber laser. Secondly, the DFB fiber laser based hydrophone system are demonstrated. The Phase demodulation scheme based on phase generated carrier (PGC) is built up. However, we found that the signal vibration was large during long time experiments because the intensity, phase and polarization state of the DFB fiber laser were not stable. So another practical and simple intensity based demodulation scheme is demostrated. The tests of acoustic wave in water are given to show its possibility and prove its application prospective. Finally, the feedback effect of DFB fiber laser is researched because it is significant when DFB fiber laser are used as a sensor element. We found that the feedback effect is good for vibration sensing theoretically. The prilimetary experimental results are given to prove the feasibility of the sensing scheme.