Hello gurinder!
BER roughly always range from 10^-9 to 10^-12.As we consider communication to be error free after this.
check these discussions for more details of BER in OFDM:
http://www.dsplog.com/2012/01/01/symbol-error-rate-16qam-64qam-256qam/
http://vixra.org/pdf/1208.0091v1.pdf
https://opus.lib.uts.edu.au/research/bitstream/handle/2100/67/27_FloresCenturion.pdf?sequence=1
https://optiwave.com/resources/latest-news/new-version-optisystem-12-2/