tical detectors? Give some idea of gain that can be achieved by each. 40. Where do we place fiber amplifiers (in most situations)? REFERENCES 1. Transport Systems Generic Requirements (TSGR): Common Requirements, Bellcore GR-499- CORE, Issue 1, Bellcore, Piscataway, NJ, Dec. 1995. 2. Allowable Bit Error Ratios at the Output of a Hypothetical Reference Digital Path for Radio- Relay Systems Which May Form Part of an Integrated Services Digital Network, CCIR Rec. 594-3, 1994 F Series Volume, Part 1, ITU Geneva, 1994. 3. R. L. Freeman, Radio System Design for Telecommunications, 2nd ed., Wiley, New York, 1997. 4. Performance Characteristics for Frequency Division Multiplex/Frequency Modulation (FDM/FM) Telephony Carriers, INTELSAT IESS 301 (Rev. 3), INTELSAT, Washington, DC, May 1994. 5. Performance Characteristics for Intermediate Data Rate (IDR) Digital Carriers, INTELSAT IESS 308 with Rev. 7 and 7A, INTELSAT, Washington, DC, Aug. 1994. 6. IEEE Standard Dictionary of Electrical and Electronic Terms, 6th ed., IEEE Std. 100-1996, IEEE, New York, 1996. 7. R. L. Freeman, Telecommunication Transmission Handbook, 4th ed., Wiley, New York, 1998. REFERENCES 8. Telecommunication Transmission Engineering, 3rd ed., Vol. 2, Bellcore, Piscataway, NJ, 1991. 9. 1993 Lightwave Symposium, Hewlett-Packard, Burlington, MA, Mar. 23, 1993. 10. S. Shimada and H. Ishio, Optical Amplifiers and Their Applications, Wiley, Chichester, UK, 1992. 11. G. P. Agrawal, Fiber-Optic Communication Systems, Wiley, New York, 1992. 12. J. Everett, VSATs: Very Small Aperture Terminals, IEE/Peter Peregrinus, Stevenage, Herts, UK, 1992. 13. Optical Interfaces for Multichannel Systems with Optical Amplifiers, ITU-T Rec. 692, ITU Geneva, 1998. DATA COMMUNICATIONS 10.1 CHAPTER OBJECTIVE Data communications is the fastest growing technology in the telecommunications arena. In the PSTN, data and voice have traded places where data connectivities run about 95% or more of the total traffic load and conventional voice is less than 5%. The widespread availability o