Hello Atul Sharma,
I think your this query has been already answered as suggested by your comments in previous posts where this query was raised. Still for your convenience i would like to say that yes you can do so and it also depends on the application part of your design what results you want. Generally we can use such scenario where we could use two modulation schemes for two wavelengths in the same system. I am working with optical security and i have seen such techniques used in cryptography and stealth channel schemes. Anyway i hope your issue was solved.
Regards