Question

Optical signal of wavelength $0.75\mu m$ is transmitted with the help of an optical fiber having a numerical aperture of $0.70$. The signal is coupled to another optical fiber having the refractive index of core and cladding as $1.45$ and $1.40$ respectively. The magnitude of coupling loss in the tranmission of signal is __-- $dB$

• A. $537$
• B. $0.537$
• C. $53.7$
• D. $5.37$

Answer 1

The correct option is D $5.37$

$(NA{)}_{Sender}=0.70$
$(NA{)}_{Receiver}=\sqrt{{1.45}^2-{1.40}^2}=0.377$
Coupling loss $=20log\frac{(NA{)}_{Sender}}{(NA{)}_{Receiver}}$
Coupling loss $=20log\frac{0.70}{0.377}=5.37dB$