thank you so much alistu but something is seriously wrong i have decreased my channels to 10 now and power at output of PIN diode is 33mW at a wavelength of 190.1 Thz so i put center freq to 190.i Thz , i ahve increased sample per bits and sequence length too. cutt off freq is 0.75 * bit rate, sample rate of PIN is 5*sample rate which appx to 1.41 *10^14 Hz.but there is no output at BER analyzer. bit rate is 100 Gbps. even linewidth as i saw from samplefile is decreased tp 0.1Mhz. don’t know what to do?