Researches On The Novel Polymer Optical Fiber Amplifiers

Compared with the silica optical fiber, the polymer optical fiber (POF) is an ideal transmission medium for LAN because it has some merits such as low cost, large core diameter, easily connected and coupling. Now, the main problem which restrict to the distances of transmission is the high loss of polymer optical fibers except the perfluorinated polymer optical fibers which are high cost. So the research of polymer optical fiber amplifiers (POFAs) is required, the advance of POFA doped by rare earths is very slow, the gain of dye-doped POFA is high, but the thermal bleaching of organic dyes limits the life of POFA. To solve this problem, double-clad dye-doped POFAs were proposed. Firstly, we investigate the material and the technique of preparation of double-clad optical fibers. Centrifugal rotation polymerization equipment was designed and fabricated, using the way of polymerization under the high pressure, optical fiber performs of POFA was prepared. Some double-clad Rhodamine B(RB) doped POFAs with different shape of inner clad such as circle, eccentric circle and D shape were successfully made by drawing the performs. Secondly, some theoretical questions about the double-clad POFA were discussed. The absorption of pumping light propagating in the double-clad fibers by the dyes was analyzed using the fundamental theory of guided-wave optics. The absorption efficiency and coefficient for four double-clad optical fibers with different inner clad shape were got. The result shows that the fiber with rectangle or D-shaped inner clad has higher absorption efficiency and is ideal for the POFA. Taking into account the influences of the triplet state of dye molecule on rate equation, the gain performance of the double-clad dye-doped POFA was given. When the duration of the pumping light pulse is some nanoseconds, the gain of POFA is equal to the steady gain without the absorption of triplet state of dye molecule, the gain decreases exponentially when the duration of the pumping light pulse is longer. The transient performance of POFA shows that the gain decreases evidently as the delay-time between the pumping pulse and the signal pulse increases. Lastly, we set up a series of experiment to measure the characteristic of double-clad POFA. The fluorescence intensity measured at the end of double-clad POFA shows that the thermal bleaching of RB in the core of the fiber decreases obviously and the life of dye prolongs. The gain of the double-clad RB-doped POFA measured by the experiment is less than that indicated by the theory because the short pulse duration of the pump laser and signal laser which is not fit for dye-doped POFAs. Because we are short of money in our study, much equipment is designed and made by ourselves, which is simple and rough. Some aspects of the experiment such as equipment, fabrication technique and lasers for pumping have needed to improve. In addition, it is necessary for the structure of the optical fiber and the species of gain material to investigate farther.