Fundamentals of Plastic Optical Fibers

7Optical Link Design

The basic elements of an optical link serve the same purpose as in other communication systems: to transport information from one location to another. The essential components consist of a transmitter, a receiver, and an optical fiber. Additional components such as amplifiers, regenerators, multiplexers, demultiplexers, filters, equalizers, connectors, and splices can be used if needed. The transmitter is a light source, usually a laser diode (LD) or a vertical-cavity surface-emitting laser (VCSEL) for high-speed data rates, which converts an electrical signal to an optical signal, acting as a so-called E/O converter. Both analog and digital signals can be applied. The receiver is a photodetector, usually a photodiode whose material depends on the signal wavelength, which converts an optical signal into an electrical signal, acting as a so-called O/E converter. Different optical fibers can be selected from a large variety of fibers depending on the application and environment. For example, a silica-based single-mode fiber (SMF) is suitable for a long-haul undersea network, whereas a plastic optical fiber (POF) is adequate for local area networks (LANs) in homes, offices, hospitals, vehicles, and airplanes.

An eye diagram provides important characteristics such as the bit error rate (BER), signal-to-noise ratio (SNR), and timing jitter for the design, operation, and maintenance of an optical link. These characteristics, of course, are parameters of the communication ...