COFDM in fiber optics

In large SMATV collective antenna installations, for example a university campus or a large hospital, fiber optics are emerging as the ideal solution to transport signals free of leaks or interference.

One of the major limitations of TV distribution systems over coaxial cables is that RF losses increase with the frequency and length of cable used. In applications where it is necessary to transport RF signals over long distances, from one point to another, coaxial cable is not the most appropriate solution. Very often the use of long lengths of coaxial cable involves using in-line RF amplifiers so this solution is sometimes somewhat expensive and cable degradation remains inevitable.

In this type of applications that we can describe as “large collective antenna installations” SMATV (for example a university campus where it is necessary to carry the signal from the main building to other buildings), it appears that fiber optic cables are the ideal solution. Fiber optic cables have very small losses compared to coaxial cable. As it is a non-metallic cable, problems with leaks or interference with RF signals are absent, which makes optical fiber the most suitable solution for transporting RF signals through a “noisy” RF medium.

Solutions

For this type of installations, companies such as Promax They have specific solutions.

Thanks to its DT-610 module it is now possible to easily transmit the DVB-T (COFDM) channels generated by the Digital to TV headend, in a fiber optic cable, covering distances of up to 10 km, using a wavelength of 1550 nm (other wavelengths are provided upon request).

On the opposite side of the fiber, another headend containing a DT-620 module can receive this optical signal and recover the original DVB-T RF signal with hardly any distortion. This RF signal can then be distributed back into a coaxial cable network if necessary.