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2.1 Loss and Bandwidth Windows > 2.1 Loss and Bandwidth Windows - Pg. 48

48 Propagation of Signals in Optical Fiber Finally, the phemomena discussed in this chapter also apply to various compo- nents. Some of these components are designed not to minimize effect on the prop- agating signal but rather to produce some desired interaction. This will provide the underpinnings for understanding the physical limitations of components described in Chapter 3. 2.1 Loss and Bandwidth Windows The loss incurred by propagating down a fiber can be modeled easily as follows: the output power P out at the end of a fiber of length L is related to the input power P in by P out = P in e -L . Here the parameter represents the fiber attenuation. It is customary to express the loss in units of dB/km; thus a loss of dB dB/km means that the ratio P out /P in for L = 1 km satisfies P