Experimental Study On Hydrogen Heating Source In FBT System

The method of FBT has been widely used in domestic and foreign large-scale production, because of its lower loss, well stability, suitable for batch production and so on. Facing to the rapid developmental optical communication system, the requirements for stable performance of FBT optical fiber coupler is more and more stringent. In the FBT system, hydrogen combustion heating is the commonly heating method. More and better understanding the characteristics of hydrogen heating source and the interaction mechanism with the hydrogen heating source and optical fiber is very important to produce well performance FBT optical fiber couplers.The first chapter of paper introduces the three kinds of production methods and principles for fiber coupler, and then mainly introduces the principle and advantages or disadvantages of four kinds of heating methods for FBT optical fiber coupler, FBT system, preparation process and the performance parameter of FBT fiber coupler.In paper, the second chapter chiefly introduces the related theory of FBT fiber coupler. It includes the working principle of FBT fiber coupler, three kinds of fiber radius curve theory models, two kinds of optical fiber fusion extent of melting models and equivalent degrees of melting for two fused fibers.The third and fourth chapters are the focus of the paper. The third chapter basically introduces the characterization of hydrogen heating source in FBT system. First, the axial temperature distribution in120-220sccm hydrogen flowing and the transverse temperature distribution in120,150and190sccm hydrogen flowing was measured by K type thermocouple. Second, single optical fiber was tapered in120,150and190sccm hydrogen flowing, which can look for the distance range of qualified excess loss and fiber shape of the hydrogen heating source. The meeting range is the effective working range of hydrogen heating source. This distance range is very small, less than1mm, and it gradually reduce with the increase of hydrogen flowing.The fourth chapter primarily introduces the experimental study on the interactions of hydrogen heating source and optical fiber. This part includes two aspects, one is the single fiber; the other is two optical fibers (splitters or WDM). In actually, the studying of the interactions of hydrogen heating source and single optical fiber is studying the effective heating width W by means of single fiber. In addition, the interaction between hydrogen heating source and two optical fibers is virtually studying the variation regular of melting degree of optical fiber couplers which made on certain conditions. The experimental results show that, the range of effective heating width W is about3.3-7.Omm, and it is increased with the increasing of hydrogen flowing; the melting degree values of splitter is very large, the minimum is about1.85; the melting degrees values of WDM is very small, the minimum nearly close to1. Pulling speed, coupler ratio, hydrogen flow and the distance of fiber and heating source will all have a certain impact on the degree of melting.