Design Of A New Type Of 3×1 Optical Fiber Coupler

The optical fiber coupler is a kind of passive optical devices, used for joining two or many optical fibers, and enables the coupling of optical signals transmitting in the optical fiber to take place in the special coupling district, and distributes power or wavelength. The making methods of optical fiber couplers have chemical corroding, grinding and fused biconical taper method. The fused biconical taper method is widely used in making fiber couplers, and this method has many advantages, such as small excess loss, perfect direction characteristic, simple control and lower cost, etc. A coupler is manufactured by placing two or more fibers adjacent to one another, then fusing and stretching them, thus creating a coupling region. The heating area is stretched until the desired coupling properties are achieved. The device is called a fused biconical taper(FBT) coupler. Now, the appliances for fabricating 1×2 or 2×2 FBT couplers are popular. In practical application, n×m FBT couplers are more needed, and the methods of making have concatenation of the basic units and making directly. The method of making directly may go as this: keeping n optical fibers in touch closely so as to form a suitable topological structure, then heating them up using high temperature heat source, as the same time, drawing them. On the basis of existing condition, this laboratory develops a new type of 3×1 optical coupler to meet the needs of optical fiber sensing system and optical fiber medical science. The main contents of this text is as follows: (1) The text introduces the elementary knowledge of fibers, stresses the basic knowledge of the taper optical fiber and concludes the formula of the minimal length L in order to diverge optic; (2) The text analyzes the actuality of the fiber many-ended couplers at home and abroad; the experiment uses the five mature processes :the fused biconical taper, rubbing, polishing, liquating, encapsulation, and makes a new type of 3×1 optical fiber coupler. (3) The text makes many experiments at parameter testing of the new type of 3×1 optical coupler. Through the testing, the new type of 3×1 optical coupler can satisfy the needs of optical fiber medical science and optical fiber sensing system. Moreover, using the same methodes, the n×1 (n≧3) optical fiber coupler can be made.