Differences between LED & LASER
LED vs LASER
Major differences between LED & LASER optical sources for optic-fiber communication:
| Parameter | LED | LASER |
| Wavelength Content : A monochromatic source consists of radiation of a single wavelength or a very small range of wavelength. | Large | Small (desirable; more monochromatic) |
| Spectral Width/Line Width : The wavelength interval over which the magnitude of all the spectral components is greater than or equal to a specified fraction of the total magnitude, Here, the fraction is (0.707)*P | 50 nm | < 5 nm |
| Principle of Emission | Spontaneous; random photon emission (hence, not directional) | Stimulated |
| Coherence : A constant phase difference between two waves | Incoherent; since emission is spontaneous | Coherent; since emission is stimulated; same phase as the stimulating photon |
| Output Power | Low | High |
| Directionality | Low | Highly directional |
| Speed of Operation | Slow | Faster |
| Numerical Aperture : determines the output pattern | Higher | Lower |
| Ease of Use | Easier to use; less complex circuitry | Complex circuitry; needs thermal & optical stabilization circuits due to light amplification |
| Lifetime | Long | Shorter |
| Cost | Cheaper | Expensive |
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