www.ijete.org SIGNAL DEGRADATION IN OPTICAL FIBERS

Dispersion is the spreading of a light pulse as it propagates down the fiber. Since optical fiber is a waveguide, light can propagate in a number of modes. If a fiber is of large diameter, light entering at different angles will excite different modes while narrow fiber may only excite one mode. Multimode propagation will cause dispersion, which results in the spreading of pulses and limits the usable bandwidth. Single-mode fiber has much less dispersion but is more expensive to produce. Its small size, together with the fact that its numerical aperture is smaller than that of multimode fiber, makes it more difficult to couple to light sources. Dispersion distorts both pulse and analog modulation signals