Hello everyone.
I am trying to simulate a system which consists of a CW laser at 1550 nm and 10 MHz linewidth, electroabsorption modulator, fiber of length 10 Km and then a photodiode. The RF (electrical signal) input to the modulator to modulate the light from the laser source should be upconverted to different subcarrier frequencies in the electrical domain before being i/p to the modulator. The problem is if the RF signal is at low sub-carrier frequency or baseband there is no dispersion, but if the RF is modulated (upconverted) to higher RF frequency the dispersion increases as the sub-carrier frequency increases, and the system performance deteriorates.
IF I change the laser linewidth to zero, there is no dispersion at any sub-carrier frequency whether low or high.
any idea about that ? or how to count for the dispersion in this case mathematically.
you can find the system setup and a plot of the spectrum with rf data at 8.75 GHz attached
