The dispersion due to material, waveguide and profile are -2.8nm -1 km -1 , 20.1nm -1 km -1 and 23.2nm -1 km -1 respectively. Find the total first order dispersion?

Optoelectronics and Optical Communication 

The dispersion due to material, waveguide and profile are -2.8nm -1 km -1 , 20.1nm -1 km -1 and 23.2nm -1 km -1 respectively. Find the total first order dispersion?

a) 36.2psnm -1 km -1 
b) 38.12psnm -1 km -1 
c) 40.5psnm -1 km -1 
d) 20.9psnm -1 km -1

Answer : - 40.5psnm -1 km -1

The total dispersion is given by 
D T = D M + D W + D P (psnm -1 km -1 ) 
Where 
D W = waveguide dispersion 
D M = Material dispersion 
D P = profile dispersion.