Fiber-Optic Communications James N. Downing

Chapter 1 Introduction to Fiber-Optic Communications

Chapter 1 Introduction Objectives –Be familiar with major historical developments in telecommunications and in fiber optics –Understand the reasons for regulation, deregulation and standardization –Identify the parts of a basic telecommunication system –Calculate component and system gain or loss by the transfer function and using decibels

Chapter 1 Introduction Objectives –Define analog and digital –Describe the modulation and multiplexing processes –Understand the relationship between frequency, bandwidth, and bit rate –Understand the basic operation of the PSTN, CATV, and data networks

Chapter 1 Introduction Objectives –Identify the various classifications for data networks –Define convergence –Describe the reasons why fiber-optic systems are critical to the future of telecommunications

Chapter 1 Introduction 1.1 Telecommunications –Milestones Telegraph in 1837 by S.B. Morse Telephone in 1876 by A.G. Bell Electromagnetic waves in late 1800’s by Hertz and Marconi Wireless telegraphy and radio in 1906 Practical televisions in 1940

Chapter 1 Introduction 1.1 Milestones in Telecommunications –Digital computer in 1939 –First digitized message in 1941 –Transistors in 1947 by Shockley, Bardeen, and Brittain –Mainframe computers in 1980s –Personal computers in 1990s

Chapter 1 Introduction 1.1 Milestones in Telecommunications –LANs, PSTN, and internet –CATV –Mobile radio and phones

Chapter 1 Introduction 1.1 Regulation and Deregulation –Prior to the early 1900s, there was no regulation of the telecommunications industry. –The ICC was selected to be the watchdog of the fledgling industry. (At this time, AT&T was the dominant industry.) –In 1934, the Communications Act established the FCC and charged it with regulation of the telephone and radio broadcasting networks.

Chapter 1 Introduction 1.1 Regulation and Deregulation –By 1968, private mobile radio systems were allowed to connect to PSTNs. –By 1976, long-distance services were allowed to be delivered by industries other than AT&T. –In 1984, AT&T was ordered to get rid of the so- called Baby Bells.

Chapter 1 Introduction 1.1 Regulation and Deregulation –The Telecommunications Act of 1996 lifted many of the restrictions that had been imposed on the industry and contributed toward the tremendous growth in the telecommunications industry. –The FCC contributes to the implementation of all types of communications, which not only include terminal equipment and connections but also determine the regions over which the industry can provide services.

Chapter 1 Introduction 1.1 Telecommunications Standards –Developed by International: ISO, ITU, IEEE United States: FCC, TIA, ANSI Europe: CEPT, ETSI

Chapter 1 Introduction 1.2 Communications Basics –Basic System Analysis Consists of an information source, a transmitter, a channel, a receiver, and an output. The transfer function of a system is defined as the output divided by the input. See Figure 1.1.

Chapter 1 Introduction 1.2 Communications Basics –Basic System Analysis If the system is composed of several smaller systems, then the overall transfer function is the product of the transfer functions of the smaller systems. See Fig 1.2.

Chapter 1 Introduction Figure 1.1 Figure 1.2

Chapter 1 Introduction 1.2 Communications Basics –Analog and Digital Signals An analog signal is continuous—all values between any two points are all allowed. A digital signal is discrete—only certain values are allowed.

Chapter 1 Introduction 1.2 Communications Basics –Frequency and Bandwidth Frequency is defined as the number of cycles per second. The units are Hertz. Period is defined as the time needed to complete one cycle. Frequency and period are reciprocals.

Chapter 1 Introduction 1.2 Communications Basics –Frequency and Bandwidth Bandwidth (BW) describes the range of frequencies over which the system works. A filter controls the frequencies to be passed by a system. Aggregate bandwidth or data rate is the total transmission capability of a system.

Chapter 1 Introduction 1.2 Communications Basics –Modulation: The means by which information is encoded on a carrier signal Amplitude modulation Frequency modulation or phase modulation Amplitude-shift keying Frequency-shift keying

Chapter 1 Introduction 1.2 Communications Basics –Modulation: The means by which information is encoded on a carrier signal Frequency-shift keying Pulse code modulation –Nyquist’s Theorem –Quantization noise On-off keying