Mach Zehnder Modulator

MACH-ZEHNDER MODULATOR

PRESENTED BY:

RUPENDRA MAHARJAN (141AEM009)

SUGAN SHAKYA (141AEM008)

SRINADH THAKKALAPALLY ( 151AEM013)

OUTLINE

INTRODUCTION TYPES WORKING PRINCIPLE BASIC ATTRIBUTES APPLICATION CONCLUSION

INTRODUCTION

Electro-Optic ModulatorAn optical deviceModulates beam of light by the use of electric field

Mach-Zehnder ModulatorAmplitude modulator based on Mach-Zehnder InterferometerBeam Splitter divides Laser light into two pathsOne or both of the beams passed through phase modulatorBeams are recombined at outputConstructive or Destructive Interference controls intensity or Amplitude of

Exiting Light

SCHEMATIC DIAGRAM

SCHEMATIC DIAGRAM

DETAIL CONSTRUCTION

MZ MODULATOR

A Voltage applied to arm cause a change in refractive index according to the electro optic effect (E Δn): Pockel’s Effect

The changing refractive index phase modulates the propagating beam through arms (Δ n Δ φ): Self Phase Modulation

The phase modulation gets converted to intensity modulation by combining the two paths (Δ φ ΔI)

Medium

Mach Zehnder Modulator based on Lithium Niobate (LiNbO3)Stable over wide temperature rangeVery low bias voltage drift rate

Mach Zehnder Modulator based on Indium Phosphide (InP)Higher electrical bandwidth up to 60 GHzLower driving voltage 2.2 V

Configuration

Push Pull ConfigurationObtained by applying a data (vm) and bias voltage

(VB)on one arm

Inverted data (-vm) and bias voltage (-VB) in the other arm

Phase change in two arm are equal and oppositeChirp free intensity modulation

Configuration

Asymmetric ConfigurationModulating Signal and Bias Voltage are applied in

only one armMay be same or opposite arm

WORKING PRINCIPLE

Consider an electric field of light propagating in z-direction

In phasor form

Let the light be passed through 50:50 beam splitter of Mach-Zehnder ModulatorArm 1: Arm 2:

WORKING PRINCIPLE

Output of Mach-Zehnder Modulator

where, and

Intensity ratio

Phase generated by applied voltage V

WORKING PRINCIPLE

Net phase change

Output Intensity

, k is constant related to geometrical parameters; l is the optical wavelength (in vacuum) and L is the length of waveguide or electrode

MZM Transfer Function