Cable television is a system of providing television programs to consumers via radio frequency (RF) signals transmitted to televisions through coaxial cables or digital light pulses through fixed optical fibers located on the subscriber's property. This can be compared to over-the-air method used in traditional broadcast television (via radio waves) in which a television antenna is required. FM radio programming, high-speed Internet, telephony, and similar non-television services may also be provided through cable television.
A communications connection that carries signals from the subscriber back to the operator. The return path allows for interactive television and on-demand services, such as pay-per-view, video on demand, and interactive games.
The DOCSIS 1.1 specification was released in April 1999 and includedtwo additional functional descriptions that began to be implemented in2000. The first specification details procedures for guaranteed bandwidthas well as a specification for Quality of Service (QoS) guarantees.The second specification is called Baseline Privacy Interface Plus (BPI)and it enhances the current security capability of the DOCSIS standardsthrough the addition of digital certificate-based authentication and supportfor multicast services to customers.
Once at the headend, the signals are converted to RF signals by the fiber optic receiver and fed to the demodulator designated for the service requested by the viewer
In return path HFC networks, illustrated in Figure 2, the same system design principle applies, but now there is bidirectional transmission between the viewer location and the headend allowing for the interactive return path management. The signals from the headend are transported over SM fiber using either a 1310 nm or 1550 nm distributed feedback laser (DFB) or Fabry Perot (FP) transmitters. The receiver contains a return path laser that sends the viewer-sent signals back to the headend. Currently, wavelength-division multiplexing technologies, such as DWDM and CWDM, increase the transmission distance and system reliability
