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PHYSICAL IMPAIRMENTS

Maruthy MentireddiRaghu Kalyan Anna

MOTIVATION

IDEALISTIC: NO TRANSMISSION IMPAIRMENTS BEING CONSIDERED IN ROUTING DECISIONS.

REALISTIC: TRANSMISSION IMPAIRMENTS ARE CONSIDERED IN ROUTING DECISIONS.

IN ANY GIVEN SCENARIO TRANSMISSION IMPAIRMENTS PLAY A MAJOR ROLE IN ROUTING.

AGENDA

• TRANSMISSION IMPAIRMENTS• IMPAIRMENTS BEING CONSIDERED• METRICS AND NETWORK COMPONENTS DESCRIPTION• HYBRID SIMULATION TECHNIQUE• EVALUATION• IMPAIRMENT AWARE RWA • CONSTRAINT MODELS• ILLUSTRATIVE EXAMPLES• ACKNOWLEDGEMENT• BIBLIOGRAPHY

TRANSMISSION IMPAIRMENTS

• LINEAR:– AMPLIFIER NOISE– PMD– CROSSTALK

• NON LINEAR– FOUR WAVE MIXING– SELF PHASE

MODULATION– CROSS PHASE

MODULATION– SCATTERING

IMPAIRMENTS BEING CONSIDERED

• OPTICAL SIGNAL - CROSSTALK AT CROSSCONNECT SWITCHES(XCS) - AMPLIFIED SPONTANEOUS EMISSION (ASE) NOISE AT INTERMEDIATE AMPLIFIERS

Eg., EDFA’S

CONSIDERATIONS FOR CONNECTION PROVISIONING

• OPTICAL SIGNAL-TO-NOISE RATIO (OSNR)• POLARIZATION MODE DISPERSION (PMD)

INTRODUCTORY TERMS

• LIGHTPATH – AN ALL OPTICAL WDM CHANNEL BETWEEN ANY TWO NODES

• CONNECTION PROVISIONING – SETTING UP A LIGHTPATH FOR A CONNECTION REQUEST BY USING A ROUTING AND WAVELENGTH ASSIGNMENT (RWA) TECHNIQUE

• ROUTE – A PATH CONSISTING OF ONE OR MORE FIBER LINKS, FROM THE SOURCE TO THE DESTINATION.

• TRAFFIC/ NETWORK PERFORMANCE: CALL BLOCKING PROBABILITY

• SIGNAL QUALITY: BIT ERROR RATE

METRICS

BLOCKING PROBABILITY

NUMBER OF BLOCKED CALLS Pb = ----------------------------------------------- TOTAL NUMBER OF OFFERED CALLS

BIT ERROR RATE (BER)

ACCUMULATION OF ASE NOISE AND CROSSTALK1

SNR DEGRADATION

INCREASE IN BER2

1 AT EVERY NODE

2 AT DESTINATION

NETWORK COMPONENTS

WRN – WAVELENGTH ROUTING NODE

NETWORK COMPONENTS ALONG A LIGHTPATH IN A WAVELENGTH-ROUTED OPTICAL NETWORK

RECEIVER ARRAY

FIBER LINKCROSS CONNECT

OPTICAL

TAP

TRANSMITTER ARRAY

OPTICAL

AMPLIFIER

NETWORK COMPONENTS (CONTD)

COMPONENTS AND THEIR LOSS/GAIN PARAMETERS IN A WRN

FIBER LOSS

OPTICAL TAP

LOSS

INPUT AMPLIFIER GAIN

OUTPUT AMPLIFIER GAIN

DEMUX LOSSMUX LOSS

SWITCH LOSS

NETWORK COMPONENTS (CONTD)

ARCHITECTURE OF A N x N NONBLOCKING SPACE SWITCH USED IN OUR MODEL

SIMULATION MODEL

HYBRID SIMULATION TECHNIQUE

TRAFFIC VARIATION

CROSSTALK, GAIN, ASE NOISE

AFFECTS BER ESTIMATE

ONLINE BER ESTIMATE

CALL ADMISSION:

- MINIMUM BER

- BER THRESHOLD (SAY 10-12)

CALL ADMISSION

ONLINE BER EVALUATION

BER MODEL

LIGHTWAVE RECEIVED ER(t) = Acos(2ΠVit + Φ(t)) + Ext(t) + Ease(t) PHOTOCURRENT GENERATED ip(t) = Rƛ(ER

2(t)) + ish(t) + ith(t) BER MINIMIZATION σ0Is1

ITH = ------------------ σ0 + σ1

ILLUSTRATIVE EXAMPLES

CALLS AT THE INSTANT OF SIMULATION SNAPSHOT IN A BIDIRECTIONAL RING NETWORK

ILLUSTRATIVE EXAMPLES (CONTD)

PROGRESS OF TAGGED CALL IN A BIRECTIONAL RING NETWORK

ILLUSTRATIVE EXAMPLES (CONTD)

A MESH NETWORK

ILLUSTRATIVE EXAMPLES (CONTD)

MESH NETWORK - BLOCKING PROBABILITY Vs LOAD

FIRST FIT BER

FIRST FIT BER

RANDOM BER

RANDOM BER

INCREASED CROSSTALKINADEQUATE

SATURATION GAIN

IDEAL CASE

FIRST FIT IDEAL

RANDOM IDEAL

IMPLICATIONS• REALISTIC BER: MORE ACCURATE MEASURE OF PERFORMANCE THAN IDEAL CASE

• FIRST FIT BETTER THAN RANDOM FIT (IDEAL)

• RANDOM FIT BETTER THAN FIRST FIT (REALISTIC)

IMPAIRMENT AWARE RWA

WHY IRWA?

AUTOMATICALLY PROVISION A SIGNAL-QUALITY-GUARANTEED LIGHTPATH FOR A CONNECTION REQUEST

IRWA (CONTD)

• LIGHTPATH ASSIGNMENT BASED ON IRWA:

LIGHTPATH COMPUTATION LIGHTPATH VERIFICATION

• NETWORK-RESOURCE BLOCKING : NO AVAILABLE ROUTE OR WAVELENGTH

• PHYSICAL LAYER BLOCKING SIGNAL-QUALITY REQUIREMENTS

IRWA – INTEGRATED MODEL

NETWORK LAYER MODULE

• IMPAIRMENT AWARE BEST PATH ALGORITHM(IABP) • IMPAIRMENT AWARE FIRST FIT ALGORITHM(IAFF)

- WILL RANDOM-ROUTING PERFORM BETTER ?

IABP – INTEGRATED MODEL

• INPUTS - NETWORK STATE

- CONNECTION REQUEST

• OUTPUTSNETWORK LAYER - PATH, WAVELENGTH PHYSICAL LAYER – LIGHTPATH SIGNAL QUALITY

• ALGORITHM- PATH COMPUTATION- PATH OPTIMIZATION / WAVELENGTH ASSIGNMENT- SIGNAL QUALITY ESTIMATION- PATH SETUP- NETWORK STATE UPDATE

PHYSICAL LAYER MODULE• OSNR AND PMD CONSTRAINTS • PMD CONSTRAINT MODEL – TRANSMISSION LENGTH LIMITATION

• OSNR CONSTRAINT MODEL – Q FACTOR AS INTERMEDIATE

LIGHTPATH ARCHITECTURE• AMPLIFICATION SPAN• STANDARD SINGLE MODE FIBER• DISPERSION COMPENSATING FIBER

OSNR ESTIMATION

PROPOSED IRWA’s CHARCTERISTICS

• CONNECTION ADMISSION METRICS: FREE RESOURCES AND SIGNAL QUALITY

• AUTO-PROVISIONING

• IMPAIRMENT AWARENESS - PMD TOLERATION - PRE-ESTIMATED OSNR

• ALGORITHM COMPARISION SCHEMES - NETWORK MODEL: IDEAL AND REALISTIC IDEAL: TRADITIONAL RWA (TBP OR TFF) – A REALISTIC: TRADITIONAL RWA (TBP OR TFF) – B, IRWA (IRWA OR IAFF) – C

BEST-PATH ALGORITHMS

ILLUSTRATIVE EXAMPLES

TBP - REAL

IABP - REAL

TBP - IDEAL

FIRST-FIT ALGORITHMS

ILLUSTRATIVE EXAMPLES (CONTD)

TFF - REAL

IAFF - REAL

TFF - IDEAL

ILLUSTRATIVE EXAMPLES (CONTD)

BEST-PATH ALGORITHMS

EMPLOYING EDFA

TBP - REAL

IABP - REAL

TBP - IDEAL

ILLUSTRATIVE EXAMPLES (CONTD)

FIRST-FIT ALGORITHMS

EMPLOYING EDFATFF - REAL

IAFF - REAL

TFF - IDEAL

ILLUSTRATIVE EXAMPLES (CONTD)

EFFECT ON DATA RATE

AVERAGE NUMBER OF TRIALS FOR SIGNAL-QUALITY ESTIMATION PER CALL

IABP

IAFF

ILLUSTRATIVE EXAMPLES (CONTD)

EFFECT ON DATA RATE

EFFECT OF CHANNEL BIT RATE ON ALGORITHMS IN A REALISTIC NETWORK

IMPLICATIONS• BIT RATE INCREASE MAKES IMPAIRMENTS DOMINANT

• HIGH DATA RATE -> HIGH OSNR IS REQUIRED

• HIGH DATA RATE-> PMD LIMITING FACTOR

ACKNOWLEDGEMENT

FIGURES AND EQUATIONS HAVE BEEN ADOPTED FROM:

1. Impact of transmission impairments on the teletraffic performance of wavelength-routed optical networks, B. Ramamurthy, D. Datta, H. Feng, J. P. Heritage, and B. Mukherjee 2. Connection provisioning with transmission impairment consideration in optical WDM networks with high-speed channels, Yurong Huang   Heritage, J.P.   Mukherjee, B., 

BIBLIOGRAPHY• Issues for routing in the optical layer, J. Strand, A. L. Chiu, and R. Tkach

• Optical components for WDM lightwave networks,Borella, M.S.   Jue, J.P.   Banerjee, D.   Ramamurthy, B.   Mukherjee, B.  

• Impact of transmission impairments on the teletraffic performance of wavelength-routed optical networks, B. Ramamurthy, D. Datta, H. Feng, J. P. Heritage, and B. Mukherjee • Connection provisioning with transmission impairment consideration in optical WDM networks with high-speed channels, Yurong Huang   Heritage, J.P.   Mukherjee, B., 

QUERIES

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