Research On The Key Techniques Of Fiber Coupled Non-Coherent Lihgt Source

With the fast development of the optical fiber technology, the optical fiber sensor plays a very important role in the sensing area. Usually the fiber-coupled light sources used in the optical sensor are gas lasers, semiconductor lasers and other coherent light source. Because of its beam characteristics, it is very easy for coherent light to interference in the fiber-coupling process; this also has brought a great inconvenience in the signal processing. Therefore, to realize the fiber coupling of incoherent light, to eliminate the noise due to the inter-mode interference, and to improve the SNR of fiber optic sensors become urgent tasks. Starting from the basic principles of coupling between light and fiber, we analyze several factors which affect the coupling. From the aspect of compressing beam divergence angle, concentrating beam energy and fiber end surface processing approach to enhance the efficiency of optical fiber-coupled. The main works of the paper are as follows:First, we study the relationship between the structure of the fiber end surface and the fiber numerical aperture with respect to the improvement of the efficiency of fiber coupling. In particular, we analyze the processing method for the structure of the fiber end face in detail and we compare the results with different fiber structures.Next, we design incoherent optical fiber coupling system, employing the basic optical designing theory to decide the initial parameters of fiber-coupled system, lens type and fundamental differential tolerance. Using the ZEMAX to optimize the initial parameters of the optical system and evaluate the performance of the optical system. We also analyze the tolerance to ensure that we can still realize the anticipated function index with the existing machining precision and assembly accuracy.Finally, we process and assemble the optical system which was designed above. We also debug the fiber-coupled modules and make the contrast of different couple pattern. In our experiment, we reach the exit power up to 132.0μW.Experiments show that using this design of the incoherent light fiber-coupling module for coupling, the effluent light power of the effluent fiber increases from the previous 53.6μW to 132.0μW. The fiber-coupling optical systems proposed in this paper and the fiber numerical aperture improving methods are greatly enhance the optical coupling efficiency, which provide a technical way to further improve the performance of fiber optic sensors.