Optical Source:-The main job of optical source is electrical to optical conversion and efficient coupling of lights.
It is of two types:- LED, LASER
#LED (Light Emitting Diode):- LED is based on the principle of spontaneous emission of light.
- Atoms exist in discrete energy state hence due to absorption of external energy atoms make transition from lower energy level to higher energy level. This is known as Stimulated absorption.
- Hence, in the higher energy state atoms is unstable so, tends to comeback to lower or ground state by emitting out the energy in the form of light.
- The entire transition from higher energy level to low energy level is random in nature and there is phase difference in the component of lights. Hence, the spontaneous emission is Incoherent and causes broad spectral width of LED. Hence, LED exhibits chromatic dispersion, low Band width and Bit rate. Hence, used for low data rate and short distance communication.
- LED is not directional source of light. Hence, not preferred for single mode fibers but can be used for multi-mode fibers, Because the coupling efficiency is low.
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