Optical Communications, 2nd Edition

8.1 FIBER NETWORK INTERCONNECTION ELEMENTS

The development of fiber networks has been spurred by the rapid achievements in specific fiber interconnection elements. Figure 8.1 shows two of the basic optical elements for fiber networking. Figure 8.1a shows a fiber splitter, an interconnection device that permits light from one fiber to be split into separate output fibers. A splitter is usually constructed by tapering down the fiber ends and fusing them together into a Y-shaped connection. The tapering causes the input fiber to focus its output field to illuminate the input ends of both output fibers. Assuming a constant light brightness in the tapered output field, each output fiber collects one half of the available fiber output power. (recall Problem 2.15.) Thus if the input fiber has an output power of P_r, each output fiber collects a power of P_r/2. The output power may also be reduced by any losses of light (for example, light lost into the cladding or leakage light) during the splitting. This latter power loss is called the excess loss (L_e). Hence each output fiber in Figure 8.1a collects a power of

Figure 8.1. Fiber interconnections. (a) Splitter and (b) combiner.

A fiber combiner, shown in Figure 8.1b, is the opposite of a splitter, and permits input fibers to combine their ...