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Optical Communications

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About homeworks and projects!2

Upload HWs and do not miss the deadlines!

Never ever never do plagiarism !!! You can all references even internet! But copy and paste is just a plagiarism!!

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Review

What is light ?!4

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Region of approximation6

Region 1 [geometric optics]

Photon energies are small compared with the energy sensitivity of the equipments;

Region 2 [classical theory of electromagnetic]

Region 3 [Quantum optics] very small

Region of approximation7

Geometric Optics How light behave on a large scale

Lens magnification, reflection, refraction, focal length, ….

Classical theory of electromagnetic Radiation, polarization, interference, diffraction, dispersion, light scattering, laser physics.

Quantum Optics Study physical effects

Photoelectric effects, particle aspects, uncertainty principle, quantized energy, …

Theory of Quantum Optics8

The theory of quantum optics provides an explanation for virtually all optical phenomena. It is more general than electromagnetic optics, which was shown earlier to encompass wave optics and ray optics. [See ”Fundamentals of photonics”, Chapter 11, by Saleh].

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Radian ?!

Steradian ?!

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Radiation and Surface

Radiation from a surface11

Radiance of a surface (): Amount of energy radiated per unit time, per solid angle, per unit of projected area of the surface normal to the direction .

Radiance : 12

Radiance: Energy per time per area per solid angle [W m–2 sr–1]

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Differential power radiated

where is the surface radiance (brightness function).

Total power radiated from surface in the solid angle in direction is

Note: Radiance (brightness ) is a function of wavelength.

Lambertian surface14

Lambertian (diffusive) surface: When a radiating (or reflecting) surface has a radiance that is independent of the viewing angle, the surface is said to be perfectly diffuse, or, a Lambertiansurface.

If is the same in all directions.Lambert’s law:. the angle between the normal to the surface and the direction of the radiation.

Point Source15

A point source is a limit of radiating surface when the area of a surface decreases but it’s brightness increases such that;

exist and is finite, for .Radiance of a point source is isotropic.

Surface irradiance16

The radiant power incident on a unit area of a surface is defined as the irradiance at the surface.

Irradiance: Energy per time per area [J s–1 m–

2] = [W m–2]

differential irradiance at surface 17

By use of steradian definition, we have

So, is given by

Replace with ,

Total irradiance18

When