I am mediation developer, I want to know about which languages are used in telecommunication for mediation.
Comptel Eventlink is quite a sophisticated mediation solution and it has multiple components and multiple ways to configure and extend it.
It includes custom environments to extend and build operator specific functionality, for example the Business Logic Tool which provides a graphical UI to build business logic.
There are also many different data aggregation, filtering etc rules which can be configured.
So, a lot of the skills you would need to work with a solution like this will be specific to the solution itself. There does not seem to be many courses offered at this time although you may find some in the more general Nokia courses as Nokia now owns Comptel. There also seems to be a good collection of Comptel manual online if you search in places like kupdf.net.