Descriptif
This course is devoted to the principle and related techniques to modulate, transport and detect analog or digital information carried by an optical wave. First, the basic principles of operation of optical fiber communication systems are provided, covering modulation formats, optical amplifier and optical receiver performances. The second part of the course focus on the optical modulation techniques based on electrooptic and acoustooptic effects. Electrooptic (EO) effect is studied in detail, followed by an analysis on the performances of polarization, amplitude and phase EO based modulators. A dedicated chapter is devoted to EO effect in liquid crystals that are applied in commonly used spatial light modulators. Lastly, acoustooptic effects that deal with the interaction between an optical wave and a monochromatic acoustic wave will be described, and illustrated through various functionalities like: amplitude light modulators, beam deflectors, frequency shifters, tunable filters, spectrum analyzers…
Objectifs pédagogiques
By the end of the course, students will be able to:
- Describe the principle and related techniques used to modulate in the spatial, temporal, frequency or polarization domains an optical wave through acoustooptic and electrooptic effects.
- Compare the performances and the limits of those techniques
- Model, calculate the performances achieved with modulator devices in various configurations described in the course
- Understand the techniques and principles used for the transmission and detection of optical signals at rates of several hundred Gbit/s
- Evaluate the performance in terms of signal-to-noise ratio of a digital data transmission system operating in linear regime with a direct, self-heterodyne or coherent detection scheme.
- Carry out an initial dimensioning of an optical transmission system operating in the linear regime (in free space or by optical fibre)
Format des notes
Numérique sur 20Pour les étudiants du diplôme Diplôme d'ingénieur de l'Institut d'Optique Théorique et Appliquée
Le rattrapage est autorisé (Note de rattrapage conservée écrêtée à une note seuil de 12)- le rattrapage est obligatoire si :
- Note initiale < 6
Le coefficient de l'UE est : 30
Programme détaillé
Section 1 : Introduction to optical communication
- Modulation formats and techniques
Electro-optic modulator
Amplitude and phase modulation
Optical spectra
- Optical receiver performances
Noise detection
DIRECT and COHERENT detection : principle
Bite Error Rates and Quality Factor
DIRECT and COHERENT detection : Signal to Noise Ratio (SNR)
- Optical amplification
Erbium doped fiber amplifier : principle of operation
Noise Figure
Amplified transmission : noise accumulation
- Pre-amplified optical receiver
Optical Signal to Noise Ratio : SNRoptique
SNR for DIRECT and COHERENT detection with pre-amplification
Section 2 : Electrooptic modulation
1 - LINEAR ELECTROOPTIC EFFECT
Short reminder about properties of birefringent materials
Modification of the index ellipsoid under EO effects
Modification of the impermeability tensor coefficients by linear EO effect
Example : linear EO effect in KDP
2 - ELECTROOPTIC MODULATION
Polarization modulators
Amplitude modulators
Phase modulators
3 - ELECTROOPTIC MODULATOR CONFIGURATIONS
Longitudinal modulators
Transverse modulators
Integrated-optical modulators
Section 3 : Acoustooptic modulation
1 - Introduction to acoustooptic interaction
2 - Photoelastic effect
Mechanical strain tensor
Strain-optic tensor
3 - Bragg diffraction by an acoustooptic grating
Permittivity variation under elasto-optic effect
Acoustooptic Bragg diffraction
4 - Acoustooptic modulators
