RAMAN AMPLIFIER

MEENAKSHIME (13-713)Dept. of Electronics and Communication

EngineeringUIET, Panjab University, Chandigarh

• INTRODUCTION• OPTICAL AMPLIFIER• RAMAN AMPLIFIER• NEED OF OPTICAL AMPLIFICATION• OPERATING PRINCIPLE• TYPES OF AMPLIFIER• DRA• RAMAN GAIN IN FIBER AND BANDWIDTH• ADVANTAGES & DISADVANTAGES• FUTURE SCOPE & CONCLUSIONS

CONTENTS

An optical amplifier is a device which amplifies the optical signal directly without ever changing it to electricity. The light itself is amplified.

It operate solely in the optical domain with no inter-conversion of photons to electrons

It can be placed at intervals along a fiber link to provide linear amplification.

• It provides larger amplification bandwidth (several thousands GHz) and speed bottlenecks from electronics are removed .

• It amplify multiple optical inputs at different wavelengths simultaneously (WDM).

OPTICAL AMPLIFIER

Raman Amplifier was demonstrated in the 1980.

Unavailability of high-power diode laser pump source makes it need evident.

It amplify signals from 1270 to 1670 nm Any optical fiber can serve as the amplifying

medium Raman process itself provides high-power laser.

Disadvantage: Cross-talk

INTRODUCTION

Typical fiber loss around 1.5 um is 0.2 dB , SNR is low and BER is high.

The Optical to Electrical to Optical conversion require costly electronics but it operates in optical domain.

It can be placed at intervals along a fiber link & provide better performance over regenerative repeaters which require optoelectronic devices and electronic circuits.

larger amplification bandwidth (several thousands GHz)

Speed bottlenecks from electronics are removed & amplify multiple optical inputs at different wavelengths (WDM).

NEED OF OPTICAL AMPLIFICATION

RAMAN AMPLIFIER

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• RA is based on Stimulated Raman Scattering.• Variable wavelength amplification, depends on

pump wavelength. For example pumping at 1500 nm produces gain at about 1560-1570 nm

OPERATING PRINCIPLE

Raman Amplifier uses intrinsic property of silica fiber which itself combats Signal loss, it uses non linearity nature of fiber.Raman Amplifier are of two types:

(1). Distributed Raman Amplifier

(2). Discrete Raman Amplifier (Lumped)

TYPES OF RAMAN AMPLIFIER

In DRA, optical fiber itself is used as amplification medium.

Pumping is done with a high power pump laser injected at fiber end & amplify the signal.

It is useful in compensating losses.

DRA

RAMAN GAIN IN FIBER AND BANDWIDTH

It depends mainly on optical frequency and also on pump frequency.

There is a max. Raman gain for a frequency offset of 13.2 THz & the usable gain BW is 48 nm.

CONTD…………….

Advantages• Variable Wavelength amplification possible.Compatible with Single Mode fiber stokes

wave.Help to realize longer transmission distance.Bandwidth is large.DisadvantagesHigh pump power requirements.Sophisticated Gain control needed.Noise is also an issue.

ADVANTAGES & DISADVANTAGES

Cost effective use of available bandwidth by sophisticated combination OAs of different vendors and manufacturers. Bandwidth and Length .200 to 400 nm bandwidth amplifiers are possible.

High-power laser sources are available by Raman process itself.

Raman, EDFA combination gives a real life applications.

New fiber lasers and gratings make it practicalSystem with Terabits of capacity are possible .

FUTURE SCOPE & CONCLUSIONS

THANK YOU!!