Question

Consider an optical communication system operating at $\lambda \sim 800nm$. Suppose, only $1\%$ of the optical source frequency is the available channel bandwidth for optical communication. How many channels can be accommodated for transmitting audio signals requiring a bandwidth of $8kHz$

• A. $4.8\times {10}^8$
• B. $48$
• C. $6.2\times {10}^8$
• D. $4.8\times {10}^5$

Answer 1

The correct option is A $4.8\times {10}^8$

Optical source frequency $f=\frac{c}{\lambda }$ $=3\times {10}^8/(800\times {10}^{-9})=3.8\times {10}^{-14}Hz$
Bandwidth of channels ( $1\%$ of above ) $=3.8\times {10}^{12}Hz$
Number of channels = $\frac{Totalbandwidthofchannel}{Bandwidthofneededperchannel}$
Number of channels for audio signal $=(3.8\times {10}^{12})/(8\times {10}^3)\sim 4.8\times {10}^8$