In [1]:

```
import math
from __future__ import division
#initialisation of variables
Sigma_s=0.1; #source dispersion inns
Sigma_D=0.1; #detector dispersion in ns
Sigma_F=0.05; #fiber dispersion in ns
bitrate=622; #bitrate in Mbps
STM_rate=250; #4 channel VSB PCM
Power_margin=30; #power margin in dB
system_margin=6; #system margin in dB
Average_loss=0.6; #average loss in dB/Km
#CALCULATIONS
Sigma_max=STM_rate/bitrate; #max dispersion allowed
L2=math.sqrt((Sigma_max-Sigma_s**2-Sigma_D**2)/(Sigma_F**2)); #dispersion limited maximum length in Km
L1=(Power_margin-system_margin)/Average_loss; #Attenuation limited length in km
#RESULTS
print"Since dispersion limited maximum length is less than Attenuation limited length \nso present system length limit is =",round(L2,5),"Km";
```