Optical video transmission is still a valid option
In well-planned networks there are plenty of available fibre cables to be utilised for CCTV purposes. These so called dark fibres (a term used for an unused optical fibre) are easily adoptable for video link operation. A fibre optic link connected to this type of fibre can take an advantage of taking over the full bandwidth capacity of the dedicated fibre granted for use. Various optical architectures can be built in such an environment without causing any influence on other networked system on nearby cables.
Although the modern fiber optic video links are based on digital transmission (whereas the input and output interfaces are still conveniently supporting analogue composite video) there is no need to compress the transmitted payload for the above mentioned reason - the bandwidth is not an issue, at least in single mode fibre operation and in this level of usage. Video signal is merely going thru an analogue-to-digital conversion (A/D) at the transmitter. A very high sample rate and resolution maintains the full quality of the signal. Again at the receiving end the payload is returned back to original format by doing the respective D/A conversion. While travelling thru fiber the digital payload shall maintain it´s quality intact.
Multiplexing offers more services
To achieve more services within one fibre optic link it is possible to multiplex multiple video channels and even additional audio, data and other signalling types to a digital stream that can maintain a full quality of each service embedded. The stream has a defined frame structure which makes possibly to enable or disable any of the payload channels without causing any effect to the complete link service.
So whereas the above described technology allows us to create and design multi-purpose devices with versatile functionalities there is yet another optical technology to multiply the efficiency of a single fibre. By adopting optical multiplexing methods it is possible to create an optical architecture in which different links can share the same physical optical fibre as long as they operate on their own "optical window". A very basic example is to have two fibre optic links sharing the same media but transmitting on different optical wavelengths like 1310 nm and 1550 nm as for example. If the combining of these two optical signals has been done with proper passive optical multiplexers (like WDM splitter) the service are not interfering each other.
Optical multiplexing can be taken into much higher optical link densities by adopting more optical spectrum in use. In CCTV system the most typical technology for this purpose has been the Coarse Wavelength Division Multiplexing (CWDM, an ITU standardised technology) which allows to establish several optical layers into a single fibre.
In all above cases the common nominator and undeniable advantage is very clear - a real time system operation.