Optical Modulators

Сентябрь 5, 2022

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Optical Modulators

Содержание

2. Week 9: Optical Modulators 1. Advantage of external modulation over direct modulation. Direct Modulation
3. Week 9: Optical Modulators External Modulation
4. Week 9: Optical Modulators 1. Advantage of external modulation over direct modulation. Broad Bandwidth Large extinction
5. Week 9: Optical Modulators 2. Explain the principle of electro-optic phase modulator and electro-optic intensity modulator.
6. Week 9: Optical Modulators Electro-optic Intensity Modulator Phase modulation is converted into amplitude modulation with the
7. Week 9: Optical Modulators 3. Explain the concept of electro-absorption effect. A change in the optical
8. Week 9: Optical Modulators Electro-optic modulator Change optical path length with applied electric field. Electro-absorption modulator
9. Week 9: Optical Modulators 4. For EO Intensity modulators, why do we need to bias at
10. Week 9: Optical Modulators
11. Week 9: Optical Modulators
12. Week 9: Optical Modulators
13. Week 9: Optical Modulators 5. How to increase the EOM bandwidth?
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Week 9: Optical Modulators
1. Advantage of external modulation over direct modulation.
Direct

Modulation

Слайд 3

Week 9: Optical Modulators
External Modulation

Слайд 4

Week 9: Optical Modulators
1. Advantage of external modulation over direct modulation.
Broad

Bandwidth

Large extinction ratio

Excellent spectral purity

High Power handling capability

Removes degrading effects of direct modulation such as chirping and laser
line width stability

Слайд 5

Week 9: Optical Modulators
2. Explain the principle of electro-optic phase modulator

and electro-optic intensity
modulator.

Electro-optic Phase Modulator

Pockels effect: A change in the refractive index of an optical medium induced by
a constant or varying electric.

Pockels effect occurs in crystals lattice such as
lithium niobate

Phase modulator: When a beam of light traverses a pockels cell in which an electric field is applied, it undergoes a phase shift

A change in E

change in n

change in t

change in φ

Слайд 6

Week 9: Optical Modulators
Electro-optic Intensity Modulator
Phase modulation is converted into amplitude

modulation with the help a Mach-Zehnder interferometer (MZI)

When Vb= 0

When Vb= Vπ/2

When Vb= Vπ

Constructive interference

Most linear point

Destructive interference

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Week 9: Optical Modulators
3. Explain the concept of electro-absorption effect.
A

change in the optical absorption coefficient caused by an applied electric field

Change the intensity of light

Слайд 8

Week 9: Optical Modulators
Electro-optic modulator
Change optical path length with applied
electric

field.

Electro-absorption modulator

Change amount of light absorbed with
applied electric field.

Слайд 9

Week 9: Optical Modulators
4. For EO Intensity modulators, why do we

need to bias at quadrature point?

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Week 9: Optical Modulators

Слайд 11

Week 9: Optical Modulators

Слайд 12

Week 9: Optical Modulators

Слайд 13

Week 9: Optical Modulators
5. How to increase the EOM bandwidth?