Optical Fiber Articles about LightTransmission for Video, Audio, Data using Analog Digital L-Band HDTV 1080 and more - Fiber-Optics.info
The
CATV industry has responded to the demand of interactive, real-time, two-way television programming with
return pathtechnology. Return path management allows the viewer to send information from a transmitter located within the
set-top-box(STB) located in the viewer's home to the headend with the touch of a few buttons on the television remote. This advancement came from the design of the
hybrid fiber coax (HFC) networks that meet the demands of increased transmission distances required for today's cable television. Return path management is prevalent in
digital broadcast systems (DBS), such as Directv and Dish Network. Typical HFC networks, illustrated in Figure 1, use coaxial cable for shorter transmission lengths between video equipment and the transmitter, or the receiver and the cable customer's television, while the path between the transmitter and the
receiver uses
single-mode (SM) fiber to extend transmission distances. Even in limited distance applications, this combination allows the system designer to use the lower cost solution for each portion of the network. 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.