Hello txn,
While for the digital fiber links the nonlinearity can actually help, for the analog ones (non)linearity is a very important issue. There is a huge amount of literature dedicated to this subject. Some linearization solutions are based on the driver/receiver (electronic techniques), and others are based on modified modulators (or more generally – optical techniques).
All major photonics manufacturers like lucent, jds, corning surely have application notes etc. on this issue. Some references can also be found here:
**broken link removed**
I used to know of a few other small companies in this field but they seem to have disappeared …
Again, I think it is very important to specify your frequency of interest. There are some very different issues and difficulties when designing sub GHz circuits and modulators as opposed to a few GHz, not to mention up to 40 or 60 GHz.