Overview

The television broadcast signal, regardless of the standard used, is one of the most complex signals used in commercial communications. The signal consists of a combination of amplitude, frequency, phase, and pulse modulation techniques all on a 6 MHz channel with a single sideband transmission process called vestigial sideband (VSB).

Cable TV appeared in the industry during the early 1960s. The initial networks installed used a basic tree architecture, in which all signals emanated from the head-end location and were distributed to individual subscribers via a series of main trunks (trees), subtrunks (branches), and feeders (twigs), as shown in Figure 14-1. This topology requires analog amplifiers to periodically boost signals to acceptable levels based on the service area being covered. However, all the benefits of solving the gain/loss problems were offset by the introduction of noise and distortion directly attributed to the amplifiers. Analog amplifiers, as noted in any communications discussion, do nothing to eliminate noise (such as cross talk, white noise, Electromagnetic, and Radio Frequency Interference [EMI/RFI]).

Figure 14-1: The CATV architecture

In early 1988, the Community Antenna Television (CATV) companies discovered that fiberoptic cables could be used as a means of improving the cable infrastructure both in quality and in capacity. The initial deployments used a Fiber-Based Backbone (FBB) overlay placed on top of the existing tree networks to do the following

• Improve performance

• Reduce cascading amplifier problems

• Increase reliability

• Segment systems into smaller, regional areas

• Facilitate targeted programming

• Improve...