20-3-2007

Fotonica in SURFnet6Wouter HuismanNetwerkdiensten, SURFnet

2

Agenda

- Fibers & Infra- Module Blocks

- Transmitter, Receivers, Amplifiers, Filters- Systems

- Single channel lasers/receivers- Amplified single channel- C/DWDM

- DCM, PMD, FEC- Latest technology- SURFnet’s network

3

Optical fiber - Historical perspective

- Internal reflection known from

19th century (John Tyndall, 1870)

- Early fibers with cladding

extremely lossy ~1000dB/km

(1960)

- Today fiber loss ~0.2dB/km

Refractive indexN1(water) > N2 (air)

4

Fiber basics

- Multi Mode (MM)- Intra office- SX- max 500m

- Single Mode (SM)- LX, ZX, C/DWDM

5-10µm

50 - 62µm

CoreCladding

5

Fiber Loss (SM)

- Fiber loss is wavelength dependent, minimum is around 1550nm

1310nm 1470nm-1620nm

6

Fiber plant layout

Equipment

POP

Splice

HandholePatching at ODF

MMR

~4km ~4km

7

Fiber Plant test

Basic paramaters:- Length- Loss- Reflection

OTDR (optical time domain reflectometer)

8

10Gb/s optical transmitter technologies

DFB

External Modulation - DM-DFB (Directly Modulated Distributed Feed Back laser)

• Cheap, small, low power consumption

• Chirped, i.e. different wavelength during “ones” and “zeros” which leads to a wide optical spectrum and associated transmission impairments

• Used for short reach transmission

{0,1,1,0,1,1,…,0,1,0}

DFB

{0,1,1,0,1,1,…,0,1,0}

Mach-ZehnderLiNbO3 modulator

External Modulation - CW-DFB (Continuous Wave DFB laser) and MZ (Mach-Zehnder) combination

• Expensive, relatively large, high-power drivers (high power consumption)

• Excellent performance

• Typically used for DWDM (Dense Wavelength Division Multiplexing)

9

Typical optical receiver setup

preamp AGC

CLK

decisioncircuit

(A)PD

Prec (dBm)

BER

10-12

10-9

10-6

Psens

data

10

Traditional optical fiber transmission systems

- Combination of transmitter and receiver connected directly to dark fiber

- Typical distance is max 100km- 150Mb/s -2.5Gb/s

Tx Rx

PT (dBm) PR (dBm)

Transmission fiber

α (dB/km)

Transmission distance = (PT-PR) / α (km)

11

3R regeneration - OEO

Transmitter – Receiver = 3R

- Re-amplification

- Re-timing

- Re-shaping

Tx Rx Tx Rx Tx Rx

12

EDFAs (Erbium Doped Fiber Amplifiers)

• Fiber doped with Er3+ ions be excited by 980nm or 1480nm photons• Spontaneous emission generates noise• Excited state Erbium ions can be stimulated to decay to ground state via stimulated emission by a 1550nm signal

Pump laser

Incoming

Outgoing

13

Single Channel System with amplifiers

Tx RxOAOA

Pre and Post Amplifiers allow for longer single span Systems upto 240km

-150Mb/s -2.5Gb/s

Tx OLAOA RxOAOLA

14

Wavelength Division Multiplexing (C/DWDM)

- WDM filters, passive device

- Muxing coloured wavelength

- Spacing between ’s determines the number of channel per fiber

- SURFnet’s DWDM supports 72 ’s @ 10Gb/s

15

DWDM System

OADM Node

Mu

x

Terminal Node AMP NodeOEO

OEO

…

Mu

xOEO

OEO

…

DCF

DCF

DCF

DCF

DCF

DCF

DCF

DCF

OEO

OEO

…

OEO

OEO

…

DCF

DCF

Dem

ux

Dem

ux

Terminal Node

OEO

• Typically 80 channels spaced at 100GHz using C and L band• Each channel operating at 10Gb/s, thus 800Gb/s per fiber• Limited Optical Add and Drop for point-to-point optical lightpaths

16

Chromatic Dispersion

- Typical value dispersion (D) 17ps/nm*km

Transmission

Rate

Spectral

Width (F)

Bitperiod(T

b)

Max distance

(km)

2.5Gb/s 0.025 4x10-10 800

10Gb/s 0.1 1x10-10 50

40Gb/s 0.4 2.5x10-11 3

T ~ bitperiod

L = Tb/ F*D

10Gb/s

F

17

Chromatic Dispersion

After 120km transmission

Speed of Light is Wavelength dependent: Chromatic dispersion affects pulse shape

1 2

1 2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

4100 4300 4500 4700 4900 5100 5300 5500

Time (ps)

Opt

ical

Pow

er (A

.U.)

Optical pulse shape at transmitter output

Tx

120km standard SMFD=17.8 ps/nm km

RxOA ƒ

120km-10Gb/s system configuration

rb = 10Gb/s

c = 1557nm

OA

011101101001001 011101101001001

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PMD

20

FEC

- Forward Error Correction

- Technique to improve bit error rate resulting better Preceiver

- Adding FEC increases bitrate worse Preceiver

Transmit Receive

1 0 0 1 0 1 0 0 1 00 1 1 1 1 0 1 0 1 10 0 1 0 1 0 0 1 0 11 0 1 1 1 1 0 1 1 10 1 1 1 1 0 1 1 1 1

Prec (dBm)

BER

10-12

10-9

10-6

Psens

FEC on

Parity check indicates the single error bit

21

New developments

- 40Gb/s and 100Gb/s- QPSK/QAM 40G over 10Gb/s

From Static to Dynamic:- MEMS – Switchable mirrors

- Dynamic WDM- eDCM- Tunable lasers- Tunable filters- DRAC

22

Layer 0 Evolution

Advanced FEC

Advanced Signal Processing

Higher Spectral Efficiency(QPSK/QAM)

Remove Raman, Increase Performance

Remove DCMs & Amps, Increase PMD Tolerance, Eliminate complex engineering rules (esp. OADM)

4x Capacity per Line and 40G Service Support

OADM NodeM

ux

Terminal Node AMP NodeOEO

OEO

…

Mu

xOEO

OEO

…

DCF

DCF

DCF

DCF

DCF

DCF

DCF

DCF

OEO

OEO

…

OEO

OEO

…

DCF

DCF

Dem

ux

Dem

ux

Terminal Node

Ram

an

Ram

an

Ram

an

OEO

Mu

x

OEO

OEO

… OEO

OEO

…Dem

ux

OEO

ROADM NodeTerminal Node AMP Node Terminal Node

23

Dynamic Networking

ROADM

SMF-28

SMF-28

SMF-28

E-LEAF

E-LEAF

E-LEAF

TWcTWc

ROADM

ROADM

ROADM

ROADM

ROADM

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SURFnet6

• third generation DWDM• 10Gb/s per channel• 50GHz channel spacing• wavelength locking• optical add/drop• forward error correction• dispersion compensation• C-band, can be upgraded to add L-band

Dordrecht1

Breda1

Tilburg1

NLR

BT

BT

NLR

BT

Zutphen1

Lelystad1

Sub network 4: Blue Azur

Subnetwork 3: Red

Sub network 1: Green

Subnetwork 2: Dark blue

Subnetwork 5: Grey

Emmeloord

Zwolle1

Venlo1

Enschede1

Groningen1

LeeuwardenHarlingenDen Helder

Alkmaar1

Haarlem1

Assen1

Beilen1

Meppel1

Emmen1

Arnhem

Apeldoorn1

Bergen-op-Zoom

ZierikzeeMiddelburg

Vlissingen Krabbendijke

Breukelen1

Ede

Heerlen2

DLO

Schiphol- Rijk

Wageningen1 Nijmegen1

Hilversum1

Hoogeveen1

Lelystad2

Dwingeloo1

Amsterdam2

Den Bosch1

Utrecht1

Beilen1

Nieuwegein1

Heerlen1

Heerlen1

Maastricht1

Eindhoven1

Maasbracht1

Rotterdam4

3XLSOP

I BG1 & I BG2Middenmeer1

NNII nHolland

SchipholOegstgeest

Lisse

ZoetermeerLSOP Rtd

SWOVNBD

DenHaag

Rotterdam1

Delft1

Leiden1

Amsterdam1

25

Thanks!

wouter.huisman@surfnet.nl