Question

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

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

Answer 1

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

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
$=\frac{2.3\times {10}^{14}}{20\times {10}^3}=1.15\times {10}^{10}$