Hi Jayeshkumar,
I am also working on RoF link. However, I am not considering WDM in my work and my range is upto 70 Km
Acceptable BER for RoF links is upto 10e-3. This value is known as ‘FEC limit BER’. This means that the we can tolerate any BER less than 10e-3 and the Forward Error Correction Codes (FEC) help in bringing down the BER to less than 10e-9.
I suggest that you run your simulation for different fiber lengths and check at what length BER is attaining 10e-3. This is the maximum distance your link can have.
I had attended an IEEE conference recently and one of them presented their work – BER comparison in ROF links.