Subject :- Applied Physics 2.

Topic :- Laser.

Difficulty :- Medium.

Communication is defined as transfer of information from one place to another, within a communication system the information signal is superimposed on a carrier wave and the carrier wave is modulated by the information signal. The modulated carrier wave is then transmitted through the communication channel to the destination where it is received and demodulated to extract the original information. The carrier waves are electromagnetic waves. Greater is the carrier frequency, larger is the transmission bandwidth and thus the information carrying capacity of the communication system. To transmit an optical carrier signal over a long distance a guiding channel is required. This is done by sending an optical beam or pulse through an optical fiber.