Why AM modulated analogue multimode fibre optic video transmitters are smaller than digitally encoded multimode fibre optic video transmitters?

I think the best way to explain this is with a few block diagrams and some photos. The block diagram below shows the basic design of a simple AM modulated fibre optic transmitter.



Our first fibre optic transmitter released in 2002 ran on this exact design and below I include a photo of this product’s PCB (Printed Circuit Board).

As you can see the design is so simple that the product is a mere 35mm in length.

A digitally encoded fibre optic transmitter is more complicated because all the video and data signals have to be converted into digital signals before they are processed and transmitted. The block diagram below shows the basic system design for this type of product.

As you can appreciate this is a far more complex design. The picture below is of our VTXD-030-SMM. When we designed the VTXD-030-SMM we decided to make the video transmitter and the video/data transmitter a one PCB design and only populate the component required for the particular model. It is for this reason that our video and our video/data units are the same size. This was done to simplify the product range and to decrease the cost of the product.

This product is 133mm in length, which is 98mm longer than the simple analogue design.

http://www.BFRDigital.co.za/fibre.html