106Propagation of Signals in Optical Fiberlong times) to relieve strain and hence does not suffer the chemical surface changesthat afﬂict strained glass.Plastic optical fiber has been in the home for decades. For example, theSony/Philips Digital Interconnect Format (S/PDIF) interfaces are used to carry audiosignals between devices and stereo components. The physical medium can be opticalfiber using the TOSLINKR(TOShiba-Link) standard. This application uses step-index polymethyl methacrylate (PMMA) fibers whose 1 mm total diameter consistsof a 980 micron diameter plus 10 micron thick cladding ring. The core index is 1.49and the cladding index is 1.42. The bit rate-distance product is 10 MHz-km. Becauseof the short distances of the applications, the bandwidth limitations have typicallynot come from the fiber but from the speed of the transmitters, which are 650 nmLEDs. The material does not transmit in the infrared, thus disallowing the use of850 nm VCSEL transmitters used in gigabit per second data communications.
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Optical Communication Systems, single-mode fibers, bit rate-distance product