Application Study Of The Fiber Laser Self-Mixing Interferometry On The Measuring Small Vibration

The laser beams emitted from a laser diode is reflected or scattered by an external target which needs to be measured, and a part of them are coupled back into the laser cavity. The feedback light will carry the information of the measured target when reflected or scattered. Then it is mixed with original light in the laser cavity to produce interference, with the output power or output frequency being varied. Finally, through the demodulation of the power or frequency, we can obtain the physics parameters of the measured target, such as velocity, displacement, vibration, temperature, morphology, etc. This kind of modern optical sensing surveying technology has many advantages, comparing with the conventional two-beam interference, and obviously, it will be an important development direction of the modern optical surveying technology.Firstly, the theory of the self-mixing interferometry was discussed in detail at the beginning of the paper. Secondly, the structure and principle of the erbium-doped fiber linear laser were introduced. Meanwhile, the paper obtained the advantages of the erbium-doped fiber linear laser, compared with optical two-beam interference and self-mixing interferometry using other types of lasers. Thirdly, the paper numerically simulated the self-mixing interference signals of the erbium-doped fiber linear laser by using software called Matlab. Lastly, a new optic fiber sensing and measuring system was established based on the erbium-doped fiber linear laser. In order to verify the feasibility of the system, we did an experiment to measure the small vibration of a loudspeaker by the system. The experimental result shows that there has a good linear relationship between the slaving voltage and the vibration displacement of loudspeaker.The research in this paper proves that, the new optic fiber sensing and measuring system based on the erbium-doped fiber linear laser is feasible. It is much more convenient to measure small vibration displacement by using this new optical sensor system, which has a simpler structure, comparing with others vibration measuring systems. With the development of the research, it is expected to measure more physical parameter in every kind of environment, so as to establish the optical fiber sensing measurement network of multi-function and miniaturization, which has extensive applications in many fields.