Bernie G4HJW is well known for his innovative microwave designs as well as many other good projects in recent years. This year he has produced another winner for the Finningley Round Table in mid July: a baseband optical transceiver kit designed with SMA components. For details see http://www.earf.co.uk/nanotrx.htm . I am not sure if Bernie is planning to make kits available more generally. Bernie has tested this design over a 65km line-of-sight path recently.