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WELCOME

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TUNABLE LESER

Presented by,

TONY JAIMY

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Contents…

• Introduction

• Need for tunable devices

• Types of tunable lasers

• Advantages and disadvantages

• Requirments

• Conclussion

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INTRODUCTION

Theodor W Hansch introduced the tunable laser in 1972

First tunable laser was the dye laser

Capable of laser operation from 670 nm to 1100 nm wavelength

High output power

Tunable devices enable dynamic DWDM networks

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LASER Emits light through a process of optical amplification.

Each photon emitted has an energy equal to the difference between the higher and lower energy levels

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Need for tunable laser

Wavelength-Division Multiplexing(WDM)

A single tunable laser module can serve as a backup for multiple channels

Tunable lasers will ease a switch to alternative channels without swapping hardware or reconfiguring network resources.

Provide flexibility at multiplexing locations

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Types of tunable lasers

Distributed Feedback (DFB)

Distributed Bragg Reflector Laser (DBR)

External Cavity Laser diode (ECDL)

Vertical-Cavity Surface-Emitting Lasers (VCSEL)

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THE DISTRIBUTED FEEDBACK LASER

Unique in that they incorporate a diffraction grating directly into the laser chip itself

The grating reflects a single wavelength back into the cavity

Forcing a single resonant mode within the laser

Producing a stable, very narrow-bandwidth output

Controlling the temperature of the laser diode cavity

The tuning range of a single DFB laser cavity is limited to a small range of wavelengths

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THE DISTRIBUTED BRAGG REFLECTOR (DBR)

Tunable DBR lasers are made up of a gain section, a mirror (grating) section, and a phase section

Tuning is accomplished by injecting current into the phase and mirror sections

Output power is typically less than 10 mW

Grating assisted co directional Coupler with rear Sampled reflector (GCSR) laser

The GCSR laser is a monolithic widely tunable laser

Another variation of the DBR laser is a grating-assisted co-directional coupler with rear sampled reflector

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THE EXTERNAL CAVITY DIODE LASER

It uses a conventional laser chip and one or two mirrors

Its external diffraction grating and movable reflector together constitute a variable-wavelength filter

The movable reflector gives the laser both its great advantage and its main weakness--a wide tuning range and a low tuning rate

The tuning speed is fairly low--it can take tens of milliseconds to change wavelengths

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THE VERTICAL CAVITY DIODE LASER

VCSEL are located on the top and bottom of the semiconductor material

VCSELs emit much more nearly circular beams than edge-emitting lasers

The dominant cost of a telecommunications laser is not the chip

VCSELs need less power and can be directly modulated at relatively high speeds--up to 10 Gb/s

VCSELs operating at 850 nm have proven ideal in short-reach applications--in buildings

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TUNING WITH MICROMECHANICAL ELEMENTS

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Advantages and Disadvantages

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TUNABLE LASERS IMPROVE NETWORK EFFICIENCY

Reducing Risk of Human Error

Better Use of Expensive Network Bandwidth

Flexible Provisioning

Simplified Capacity Planning and Expansion

Faster, More Responsive Provisioning

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TUNABLE LASERS ENABLE NEXTG CAPABILITIES

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TUNABLE LASER PERFORMANCE REQUIREMENTS

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FUTURE OF TUNABLE LASERS

In Optical NetworkHigh capacityhigh speed

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CONCLUSION

• Tunable networks into clear focus

• Eliminate logistical and inventory problems

• network architectures with dynamic functionality

• Revolutionize optical networks

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REFERENCE

“Tunable lasers” by Elizabeth Bruce; IEEE Spectrum, February 2002.

www.lightreading.com

www.blueskyresearch.com

www.iolon.com

www.opticsjournal.com

www.telcordia.com

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Thank you…