Intel photonics engineers have unveiled a chip, made entirely from silicon, that can transfer data at speeds up to 200Gbps, on a single beam of light. This prototype chip is twice as fast as current optical modules, but these are not made from silicon and suffer from limitations Intel has been able to work around with this new silicon chip. Just the fact the chip is made from silicon makes it much easier to scale up the speed for future uses.
The reason silicon hasn't been used with the other optical circuits is because silicon as a semiconductor doesn't really have the properties that you want. Instead, companies have used compounds such as indium phosphide and gallium arsenide. The properties of these materials, compared to silicon, are superior, but they are limited by the manufacturing and the hardships of making them scale to faster speeds. More