raman amplification in optical fiber
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OPTICAL FIBER COMMUNICATIONX 422.21
CHIRAG WARTY
UNIVERSITY OF CALIFORNIA LOS ANGELES,
UCLA EXTENSION , CA 90024
WDM using Raman Amplification for optical Fiber Networks
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Presentation Overview
14 February 2009University of California Los Angeles - Extension
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Introduction to Optical Amplifiers Semiconductor optical Amplifier (SOA)
Doped fiber amplifier (DFA)
Raman Fiber Amplifier (RFA)
Raman Fiber Amplifiers
Sub- Marine optical fiber Communication
Optimum Use of Present Long Haul Infrastructure
Motivation
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OPTICAL AMPLIFIERSTYPES OF AMPLIFIERS
CHARACTERISTICS
University of California Los Angeles - Extension
14 February 2009
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Introduction
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Optical Amplifiers
14 February 2009University of California Los Angeles - Extension
4 Types of Optical Amplifier
Semiconductor Optical Amplifier (SOA)
Doped Fiber Amplifier (DFA) Raman Amplifier
Modes of application In Line Amplifier Preamplifier Power Amplifier
Functions of the Optical Amplifier
Transmitter
Receiver
Power Amplifier
In line amplifier
Preamplifier
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Stimulated EmissionStimulated Emission Pumping MechanismPumping Mechanism
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Optical Amplification
Signal
Pump
Signal
Coupler
Transition State
Ground State
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Semiconductor Optical Amplifier (SOA)
Small Size and Electrically pumped
Semiconductor cavity is used
Loss of power in the cavity is greater than the gain.
Advantages Consume Less Electrical
power Fewer Components,
Compact Cheaper than DFA and RFA
Disadvantages Rapid Gain response High noise, low gain.
Polarization dependence High non linearity
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Doped Fiber Amplifier (DFA)
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Amplifier fiber length – 10
to 30 mts.
Doped by rare earth
elements
Group III or V
Erbium, Ytterbium,
Thulium
Operating region – 1530 to
1560 nm but extensible
Low pump Power
Advantages Pump wide range of
wavelength Immune to crosstalk and
intermodulation distortion Low dependence of Gain on
light polarization Customizable
Disadvantages Special fiber design Precise power loss
estimation
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Doped Fiber Amplifier
EDFA
Silica Fiber glass doped with Erbium (Er 3+)
14 February 2009University of California Los Angeles - Extension
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Stimulated Raman Scattering (SRS)Stimulated Raman Scattering (SRS) SRS MechanismSRS Mechanism
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Dr. C. V. Raman – Nobel Prize (1930)
Silica Glass : Si-O-Si bond
Pump photon – Larger wavelength
Signal photon – lower wavelength
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Stimulated Raman Scaterring
Transition State
Ground State
ωs
ωpump
ωs
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Basics of Raman Amplifier
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Stimulated Raman Scattering (SRS)
Raman Gain Mechanism Lumped Raman Amplifier Distributed Raman Amplifier
Raman Amplification Gain depends on frequency
separation Gain does not depend on
relative direction of propagation
Upper state – Subpicoseconds
Gain Polorization dependent
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Amplifier propertiesAmplifier properties
14 February 2009University of California Los Angeles - Extension
Broadband amplification
using multiple pumps
Amplified spontaneous
emission (ASE)
Signal Spontaneous beat
noise
Noise figure
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Raman Amplification
Advantages Flexibility
Wide frequency range
Low costs
Very high clock frequency (THz)
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UNDERSEA CABLENETWORK TOPOLOGIES
DESIGN
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Sub – Marine Fiber optics Communication
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Sub- Marine Fiber Optics Communication
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Sub-marine Communication What makes it Different ?
Capacity and Flexibility International Water – Free right of way Very high reliability Failures due to external factors
Ship anchors, Natural catastrophe Solution
In Network traffic restoration Ring topology , Trunk and branch topology
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Network Topologies
Long Haul networks
Bidirectional
Line switched rings
Self healing
network
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14 February 2009University of California Los Angeles - Extension
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World Projects
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Africa One First of its kind – WDM technology 40000 Km estimated 8 wavelength channels on 2 fiber pairs each Capacity 2.5 Gb/s
SEA-ME-WE-3 Sub-marine WDM routing Add/drop undersea multiplexing over 2 fiber pairs Span – Germany to Singapore
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WDM undersea routing
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World Projects
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Atlantis 2, Columbus 3, Americas II Shore based mux/Demux Connecting 4 continents Undersea branching Units optically passive Low Initial Costs
China –US and Atlantic crossing 1 Ring Networks – Higher reliability Capacity China-US 12000 Km, AC1 7100 Km Current Capacity 40 Gb/s
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INFRASTRUCTURE AVAILABILITYNETWORK DESIGN TRADE OFF
MOTIVATION
University of California Los Angeles - Extension
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Optimum use of the present infrastructure for long haul
communication
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Present day submarine cable
LAYERS:
1--Polyethylene2--"Mylar" tape
3--Stranded metal "Steel" wires4--Aluminum water barrier5--Polycarbonate6--Copper or aluminum tube7--Petroleum jelly8--Optical fibers
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Motivation
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Increasing demand for higher data rate
Very high capital associated with satellite
deployment
Developments in transmitters and filters
Development in ROV technology
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Questions