A single mode fiber has a zero dispersion wavelength of 1.21μm and a dispersion slope of 0.08 psnm -2 km -1 . What is the total first order dispersion at wavelength 1.26μm.

Optoelectronics and Optical Communication 

A single mode fiber has a zero dispersion wavelength of 1.21μm and a dispersion slope of 0.08 psnm -2 km -1 . What is the total first order dispersion at wavelength 1.26μm.

a) -2.8psnm -1 km -1 
b) -3.76psnm -1 km -1 
c) -1.2psnm -1 km -1 
d) 2.4psnm -1 km -1

Answer : - 3.76psnm -1 km -1

The total first order dispersion for fiber at two wavelength is obtained by 
D T (1260 nm) = λS 0 /4 [1-(λ 0 /λ) 4 ] 
= (1260*0.08*10 -12 )/4 * (1-[1550/1260] 4 ) 
= -3.76psnm -1 km -1 
Where 
λ 0 = zero dispersion wavelength 
λ = wavelength 
S 0 = dispersion slope 
D T = total first order dispersion. 
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