import math
from __future__ import division
#initialisation of variables
PL=1; #length of preform in m
PD=25e-3; #daimeter of preform in m
OD=125e-6; #outer daimeter of optical fiber in m
#CALCULATIONS
V=3.14*((PD/2)**2)*PL; #volume of Preform cylinder in m^3
L=V/(3.14*((OD)**2)); #Length of optical fiber in m
#RESULTS
print"Length of optical fiber=",L/1e3,"KM"; #division by 1e3 to convert unit from m to Km
import math
from __future__ import division
#initialisation of variables
NA1=0.2; #numerical apperture of fiber 1
NA2=0.1; #numerical apperture of fiber 2
D1=12; #core daimeter of fiber 1 in um
D2=6; #core daimeter of fiber 2 in um
#CALCULATIONS
Losses=20*math.log10(NA1/NA2)+20*math.log10(D1/D2); #total fiber to fiber coupling losses due to NA mismatch and size mismatch
#RESULTS
print"total losses=",round(Losses,5),"db";