Electro-optic Modulator
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The document discusses modulation, the electro-optic effect, electro-optic modulators (EOMs), the acousto-optic effect, and acousto-optic modulators (AOMs). Modulation varies properties of a waveform to transmit information. The electro-optic effect modifies material properties with electric fields. An EOM uses this effect to modulate light. The acousto-optic effect alters material properties with strain, and an AOM controls light using sound waves.
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Electro-optic Modulator
- 1. Supervised by : Prof. Magdy Ibrahim
- 2. Contents • Modulation. • Electro-optic Effect. • Electro-optic Modulator (EOM). • Acousto-optic Effect. • Acousto-optic Modulator (AOM).
- 3. Contents • Modulation. • Electro-optic Effect. • Electro-optic Modulator (EOM). • Acousto-optic Effect. • Acousto-optic Modulator (AOM).
- 4. Modulation
- 5. Modulation Modulation of Binary Signals 1. Amplitude modulation • used for: o up to 1200bps on voice grade lines o very high speeds over optical fiber
- 6. Modulation Modulation of Binary Signals 2. Frequency Modulation • Binary PSK: Two phases represent two binary digits. 3. Phase Modulation • Two binary values represented by two different frequencies.
- 7. Contents • Modulation. • Electro-optic Effect. • Electro-optic Modulator (EOM). • Acousto-optic Effect. • Acousto-optic Modulator (AOM).
- 8. Electro-optic Effect • Definition A change in the optical properties of a material in response to an electric field. • Types 1. Change of the absorption. 2. Change of the Refractive index (n). • Pockels Effect The change in the refractive index linearly with the electric field. • Pockels Cells Voltage-controlled wave plates.
- 9. Electro-optic Effect Pockels Cells • Geometry Longitudinal devices Transverse devices • Material β-barium borate (BBO) : for high average power and high switching frequencies. • Half-Wave Voltage ( V π ) The voltage required for inducing a phase change of π (Relatively high) .
- 10. Contents • Modulation. • Electro-optic Effect. • Electro-optic Modulator (EOM). • Acousto-optic Effect. • Acousto-optic Modulator (AOM).
- 11. Electro-optic Modulator (EOM) • Definition An optical device in which a signal-controlled element displaying electro- optic effect is used to modulate a beam of light. • Types of EOMs 1. Phase Modulation 2. Amplitude Modulation 3. Polarization Modulation 4. Frequency Modulation
- 12. Electro-optic Modulator (EOM) • Definition An optical device in which a signal-controlled element displaying electro- optic effect is used to modulate a beam of light. • Types of EOMs 1. Phase Modulation 2. Amplitude Modulation 3. Polarization Modulation
- 13. Electro-optic Modulator (EOM) 1. Phase Modulation
- 15. Electro-optic Modulator (EOM) 2. Amplitude Modulation • Using Mach–Zehnder Interferometer
- 16. Electro-optic Modulator (EOM) 3. Polarization Modulation Depending on the type and orientation of the nonlinear crystal, and on the direction of the applied electric field, the phase delay can depend on the polarization direction.
- 17. Contents • Modulation. • Electro-optic Effect. • Electro-optic Modulator (EOM). • Acousto-optic Effect. • Acousto-optic Modulator (AOM).
- 18. Acousto-Optic Effect • Definition It is a change of a material's permittivity (ε) due to a mechanical strain • Materials Fused silica, arsenic trisulfide, lead silicate, and other materials. • Acousto optic Devices o Acousto-optic Filter By tuning the frequency of the acoustic wave, the desired wavelength of the optical wave can be diffracted acousto-optically. o Acousto-optic Deflector Controls the optical beam spatially. the power driving the acoustic transducer is kept on, at a constant level, while the acoustic frequency is varied to deflect the beam to different angular positions. o Acousto-optic Modulator
- 19. Contents • Modulation. • Electro-optic Effect. • Electro-optic Modulator (EOM). • Acousto-optic Effect. • Acousto-optic Modulator (AOM).
- 20. Acousto-Optic Modulator (AOM) Definition • A device which can be used for controlling the power, frequency or spatial direction of a laser beam with an acoustic wave.
- 21. Summary • Modulation is the process of varying one or more properties of a high- frequency periodic waveform with a modulating signal which typically contains information to be transmitted. • Electro-optic effect is a change in the optical properties of a material in response to an electric field that varies slowly compared with the frequency of light. • EOM is an optical device in which a signal-controlled element displaying electro-optic effect is used to modulate a beam of light. • The acousto-optic effect is a change of a material's permittivity (and refractive index), due to a mechanical strain. • AOM is a device which can be used for controlling the power, frequency or spatial direction of a laser beam with an acoustic wave.
- 22. References • Modulation: • “Communication Systems 4Th Edition” by Simon Haykin – Chapter 2. • Electro-Optic effect: • http://www.rp-photonics.com/electro_optic_effect.html • Acousto-Optic effect: • http://en.wikipedia.org/wiki/Acousto-optics • http://www.mt-berlin.com/frames_ao/descriptions/ao_effect.htm • Electro-optic modulator: • http://en.wikipedia.org/wiki/Electro-optic_modulator • http://www.rp-photonics.com/electro_optic_modulators.html • “Photonics Optical Electronics for Modern Communications” by AMNON YARIV – Chapter 9. • Acousto-optic Modulator: • http://www.rp-photonics.com/acousto_optic_modulators.html