Modal and Material Dispersion

Daniil Y. Gladkov

Outline

• Hardware• Types of Dispersion• Data• Transfer Function• Future Project Proposals

Why does dispersion matter ?

• Understanding the effects of dispersion in optical fibers is quintessential in optical communications in order to minimize pulse spreading.

• Pulse compression due to negative dispersion can be used to shorten pulse duration in chirped pulse lasers

Hardware and setup

Laser Diode Power Output Profile

Pulsed Fiber Laser System

From Wesley Hughes and Jared Green’s Presentation

Pulse Generator and Amplifier

Modal Dispersion

• Pulse Spreading: where

• Number of modes:where

• Fiber Used: ,

Material Dispersion

• Pulse Spreading:

• Dispersion Coefficient:

Anomalous Dispersion

• Pulse’s higher frequency have faster phase velocity than the lower frequency components

• Responsible for negative dispersion, pulse compression, and soliton formation

• http://www.falstad.com/dispersion/normal.html

150 Picosecond Pulse Generator

1 Nanosecond Pulse with Amplifier

Femtosecond Pulse Laser

1km, 2km, 3km Fiber with Femtosecond Pulse Laser Results

• 1 km - pulse width: 215 ps σ: 572ps

• 2 km - pulse width: 385 ps σ: 2.4ps

• 3 km - pulse width: 382 ps σ: 1.62ps

• Results do not agree with theory

20.56 km Fiber with 1 Nanosecond Pulse Laser Results

Multimode Fiber

Transfer Function

Input Pulse Fitting

Output Pulse Fitting

Computation of Transfer Function

Suggestions for Future Projects

• Use Optical amplifier to boost output signal• Spectral profiling of pulses• Anomalous Dispersion modeling• Better fitting and transfer function modeling • High powered laser to overcome attenuation• More variations of fiber lengths• Soliton formation