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Niels Henrik David Bohr
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7 October 1885_18 November 1962
contributions in atomic structure and quantum mechanics
Received Nobel Prize in 1922
PRESENTED BY JITTY MARIAM JOSE S8 AEI ROLL NO:24
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INTRODUCTION Light Amplification by Stimulated Emission
Radiation (LASER) is most widely used
Tunable laser is a multi functional laser
Here laser is tuned to required wave length
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CONTENTS LASER Need for tunable laser Tunable laser Types of tunable laser Advantages Applications Future of tunable laser
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LASER Semiconductor materials that give out intense light
at one specific colour
Electrons in excited spontaneously fall down to ground state
Lasers give out energy in the form of photons
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WORKING OF LASER
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NEED FOR TUNABLE LASERIn a WDM network we have 128 different lasers
giving light according to the way in which they are designed
128 spare lasers should be stored for replacement in case of failure
Tunable laser can serve as a backup for multiple channels
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TUNABLE LASER Tunable lasers – laser whose wavelengths can be
tuned
There are two methods of tuning laser
1. Mechanically adjusting the cavity length
2. Changing refractive index of the gain medium
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TYPES OF TUNABLE LASER Distributed Feedback [DFB] laser
Distributed Bragg reflector [DBR] laser
External Cavity Laser Diode [ECDL]
Vertical Cavity Surface Emitting Laser [VCSEL]
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DISTRIBUTED FEEDBACK LASER
Incorporates a diffraction grating directly into the laser chip itself
DFB lasers are tuned by controlling the temperature of the laser diode cavity
Tuning range is limited to 5nm
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DISTRIBUTED BRAGG REFLECTOR LASER
DBR has 3 sections-gain , mirror , phase
Tuning is accomplished by injecting current which changes refractive index
Tuning range is less than 10nm
Wider tuning range up to 40nm achieved by sampled grating
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THE EXTERNAL CAVITY DIODE LASER
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It uses a wavelength selective component such as grating or prism which is adjusted in a way that produces desired wavelength
Wide tuning range of about 40nm
Low tuning rate
VERTICAL CAVITY DIODE LASERMirrors are located in top and bottom of
semiconductor
Light resonates vertically in laser chip
Mainly used in telecommunication and other short reach application
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Comparison LASER ADVANTAGES DISADVANTAGE
SMARKET APPLICATIONS
DFB Wavelength stabilityEstablished fabrication process
Low output powerLimited tuning range
Narrowly tunable applications
DBR Fast switching speedEstablished fabrication process
Broad line widthWavelength instability
Access Switching
SGDBR Broad tuning range Fast switching speed
Low output powerBroad line widthNon continuous tuning
Access Metro Switching
VCSEL Narrow line width(for output)Low power consumptionMode stabilityCircular beam emittedTest at wafer level
Low output powerConfined to short wavelengths
AccessMetro
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ADVANTAGES Reducing risk of human error
Better use of expensive network bandwidth
Flexible provisioning
Simplified capacity planning and expansion
Faster , more responsive provisioning16
APPLICATIONSLaser Radar and 3D ImagingSpectroscopyPhotochemistryatomic vapour laser isotope separationoptical communications
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FUTURE OF TUNABLE LASER Fiber optics is the most emerging technology which
accounts for the high speed and accuracy in data transfer
Tunable laser provides options of multiple channel from 16 to 160 and at a rate of 40Gb/s
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CONCLUSION Due to the ease of fabrication and flexibility ,
ordinary lasers will pave the way for tunable lasers . And hope this is going to become a revolution in the field of communication and technology , especially in the field of optical network.
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REFERENCE1. “Tunable lasers” by Elizabeth Bruce; IEEESpectrum, February 2002.2. Tunable Laser Resonance Raman Spectroscopy of Bacteriorhodopsin by
A Lewis, J Spoonhower, RA … - Proc. Natl. Acad. …, 1974 - National Acad Sciences
3. Tunable laser diode by MC Amann - US Patent 5,325,379, 1994 - Google Patents
4. Monolithic Tunable laser diode LA Coldren - IEEE journal of selected topics in quantum electronics, 2000 - 130.83.66.6
5. Digital phase-measuring interferometry with a tunable laser diode Y Ishii, J Chen, K Murata - Optics letters, 1987 - opticsinfobase.org
6. www.blueskyresearch.com7. www.iolon.com8. www.opticsjournal.com9. www.telcordia.co.in
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