Question

An optical fiber communication system works on a wavelength of 1.3 $\mu$m. The number of subscribers it can feed if a channel requires 20 kHz are

• A. 2.3 $\times {10}^{10}$
• B. 1.15 $\times {10}^{10}$
• C. 1 $\times {10}^5$
• D. None of these

Answer 1

The correct option is B 1.15 $\times {10}^{10}$

Optical source frequency f = $\frac{c}{\lambda }=\frac{3\times {10}^8}{1.3\times {10}^{-6}}=2.3\times {10}^{14}$ Hz
$\therefore$ Number of channels or subscribers = $\frac{2.3\times {10}^{14}}{20\times {10}^3}$
= 1.15 $\times {10}^{10}$