System engineering of alien wavelengths over the SURFnet network

System engineering of alien wavelengths over the SURFnet network

Roeland Nuijts, SURFnet, [email protected]

Customer Empowered Fiber Networks Workshop, Prague, Czech Republic, September 13th-14th, 2010

2

Outline

Introduction

Alien wavelength concept, advantages and disadvantages

Alien wavelengths in the SURFnet NGE (Next-Generation Ethernet) project

• Alien wavelength for metro-connections using small form factor 10Gb/s DWDM

interfaces on the existing SURFnet network

Alien wavelength for 40Gb/s long-distance SURFnet CBF connections

• mix 40Gb/s PM-QPSK and 10Gb/s NRZ-OOK on standard SMF (G.652) with

dispersion compensation

Conclusions

Alien wavelength concept

3

Rx

Tx

Tx

Rx

Rx

Tx

Tx

Rx

Tx

Rx

Rx

Tx

Rx

Tx

Tx

Rx

(a) conventional closed DWDM system

(b) multi-domain DWDM systems

(c) multi-domain DWDM systems with alien wavelength

Alien wavelength advantages

4

• direct connection of customer equipment cost savings

• avoid OEO regeneration power savings

• faster time to service time savings

• support of different modulation formats extend network lifetime

Alien wavelength challenges

5

• complex end-to-end optical path engineering in terms of linear (i.e.

OSNR, dispersion) and non-linear (FWM, SPM, XPM, Raman)

transmission effects for different modulation formats

• complicated system integration/functional testing

• end-to-end monitoring, fault isolation and resolution

• end-to-end service activation

Application of alien wavelengths in the SURFnet NGE (Next-Generation Ethernet) project

• Huge growth in data-oriented services over the past years

• Push for low-cost, flexible, hence, ethernet connections

• Until now Ethernet was transported over SDH/SONET

infrastructure as a means to re-use existing infrastructure

• With demand for more capacity and longer and high-capacity

connections (WAN instead of LAN) there is now need for Carrier

Ethernet

• SURFnet NGE (Next-Generation Ethernet) project

• SURFnet NGE project re-uses the existing DWDM layer

6

SURFnet DWDM network - after Photonic Evolution project 1Q11

• All implemented ROADMs are of type 1x5 WSSes

• Convert remaining fixed OADM nodes to ROADMs

expensive maybe no time next year

• Zwolle, Enschede, Nijmegen, Wageningen, Delft, Utrecht

ready as of September 10th, 2010

• To be done: Asd1&2, remove fixed OADM in Ehv

• Enables:

• All-optical connection between TUD, TUE and TU

(three Universities of Technology)

• All-optical connection between Aachen (antenna

field in Julich and Astron/JIVE in Dwingeloo)

• All-optical pass-through between Amsterdam

locations to close optical DWDM rings

Alien wavelengths in the metro areaDWDM Architecture SURFnet6/7

9

CIENA OME6500 and CPL

GMD

CMD

DSCM (dispersionCompensation)

10Gb/s WDM transmitter andreceiverOME6500 CPL

10

Form factor improvement – 300pin to XFPTunable 50GHz channel spacing 10Gb/s DWDM transponder

300pin MSA transponderTypical power consumption 10W

Footprint: ±100cm2

XFP transponder Typical power consumption 3W

Footprint: ±14cm2

Example: optical specifications of JDSU XFP

Initial XFP exhibits negative chirp!Initial XFP exhibits negative chirp!

Transient chirp

g

(ps)

D(ps/nm km)

0

λ (nm)

λ (nm)0

A negative frequency excursion on the rising edge corresponds to a positive wavelength excursion which means group delay increases hence velocity decreases The opposite occurs on the falling edge Both result in pulse compression which counteracts pulse broadening by dispersion, hence more reach (or dispersion tolerance) Two methods to get negative chirp, unbalanced drivers or z-cut Mach-Zehnder modulators

Transmission performance versus dispersion with negative chirp

Optimum dispersion around +800ps/nm

In each DWDM ring there are paths from each OADM node to Amsterdam1 and Amsterdam2, tailored to +800ps/nm as close as possible. Consequently, paths between rings can have up to +1600ps/nm dispersion and paths between OADM nodes less dispersion. Sufficient system performance for these dispersion values needs to be verified before deciding to use low-cost 10Gb/s interfaces in the photonic layer for NGE

Optimum dispersion can not always be achieved in systems due to 2 reasons:• in systems due to “quantization error” of DCF spools (i.e. DCF10, 20, ….) • wavelength dependence of dispersion in transmission and compensating fibers

Calculate 10Gb/s wavelengths for NGE*

14

1

2

7

6

5 3

8

9

1011

12

13

14

16

1718

19

21

22

2324

Alr01

Amf01

Asd01

Asd02Bd01

Ddt01

Dgl01Dt01

Ehv01Es01

Gn01Gv01

Ht01

Hvs01

Ledn01Mt01

Nm01

Rt01Tb01

Ut01

Wg01

Zl01

Alr01 14 21 1 7 7Amf01 29 7 7 2 14Asd01 81 45 7 80 8 46 9 44 38 18 16 20 18 14 78 15 37Asd02 19 7 9 9 23 16 14 26 18 25 14 21 35Bd01 14 1 4 14 1Ddt01 7 4Dgl01Dt01 22 14 12 1 14 27 1Ehv01 28 21 7 21 22 14 1Es01 7 23 9Gn01 7 7 7 1 39Gv01 14 21 1 14 3 14 2Ht01 14Hvs01 7Ledn01 21 7Mt01Nm01 1 7 23Rt01 1Tb01 28Ut01 2Wg01 14Zl01

LP+IP traffic

+

Network diagram

* Joint effort with Anteneh Beshir at the TUD (Delft Technical University)

Solved for required 10Gb/s wavelength connections and with minimum number of interfaces

Required 10Gb/s wavelengths for SURFnet NGE - only LightPath traffic

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  Wavelengths  

Nodes 1 2 3 4 5 6 Total

Amsterdam1 4 4 5 5 5 5 28

Amsterdam2 5 5 5 5 5 5 30

Leiden 0 2 0 2 2 2 8

Den Haag 0 2 2 2 0 2 8

Delft 4 4 4 4 4 4 24

Utrecht 0 2 0 2 2 2 8

Hilversum 0 0 0 2 0 2 4

Rotterdam 2 2 0 2 0 2 8

Dordrecht 2 0 0 0 0 2 4

Breda 0 2 2 2 0 2 8

Tilburg 0 0 2 0 0 2 4

Eindhoven 3 3 3 3 3 0 15

Den Bosch 2 2 0 0 0 2 6

Maastricht 0 2 2 0 0 - 4

Nijmegen 3 3 3 3 3 0 15

Wageningen 2 2 2 0 0 2 8

Amersfoort 0 0 0 2 2 2 6

Enschede 0 2 0 0 2 2 6

Zwolle 3 3 4 4 4 4 22

Almere 0 2 0 0 0 2 4

Groningen - - 2 2 0 2 6

Dwingeloo - - 0 0 2 2 4

Total 30 42 36 40  34 48 230

1. 230 10Gb/s interfaces required2. 82 different wavelength paths

required simulated optical transmission performance of all 82 wavelengths in order to verify whether these work and to check whether the first assessment of the FOM was correct

Simulation results of transmission performance- dispersion, received power and OSNR

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OSNRCalculated OSNR was well above ROSNR (Required OSNR) for each of the 82 paths

Measured OSNR of each 10Gb/s wavelength in the SURFnet network was well above the ROSNR

Required performance can be delivered by the new low-cost 10Gb/s interfaces!Required performance can be delivered by the new low-cost 10Gb/s interfaces!

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JOINT SURFnet/NORDUnet 40Gb/s PM-QPSK alien wavelength

DEMONSTRATION

W S S

W S S

10G40G

10G

W S S W S S10G

40G alien wave

10G

40G

416km TWRSAlcatel-Lucent

(with dispersion compensation)

640km TWRSNortel

(without dispersion compensation)

5x10Gb/s @ 50GHz

5x10Gb/s @ 100GHz350GHz

900GHz

End-to-end FoM = 1400 (a couple of dB margin over BOL OSNR limit - set against nonlinearities and

potentially adverse effect from filter concatenation [4])

Am

ste

rdam

Hamburg

Copenhagen

Ham

bu

rg40G

40G

Alien 40Gb/s wavelength transmission on SURFnet CBF connections

Alien 40gb/s wavelength on 10Gb/s-5x100km DWDM system using standard G.652 fiber and DCFs

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1 10 1 10

50GHz 50GHz

0 channels guard band

W S S W S S

10G40G

10G

5x100km SMF

34% pre-compensation

95% mid-span compensation

60% post-compensation

10G40G

10G

•Fairly unfavorable dispersion map due to zero-dispersion crossing at every span and hence high XPM efficiency

40Gb/sPM-QPSK

10x10Gb/s NRZ-OOK

10x10Gb/s NRZ-OOK

1x40Gb/s PM-QPSK

Simulation results 40Gb/s alien wavelength

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1 10 10

50GHz 50GHz

0 channels guard band

40Gb/sPM-QPSK

• The ROSNR of the 40Gb/s alien wavelength increases With increasing power level of the 10Gb/s NRZ-OOK channels, starting at about 4P, probably due to XPM• Increasing the power per channels of the 40Gb/s alien wavelength in the range where we conducted these simulations does not seem to affect (improve) the ROSNR so SPM (Self-Phase Modulation) does not affect the 40Gb/s alien wavelength• Best performance when 40Gb/s channel is stronger than 10Gb/s channels

P

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- We have investigated using low-cost 10Gb/s DWDM interfaces for the SURFnet NGE project by using a heuristic model to determine the required wavelength topology and a transmission propagation model to determine the required performance

- Simulation results show that new low-cost 10Gb/s XFPs deliver sufficient performance to be used for the NGE project and these results suggest they can be connected to the existing SURFnet DWDM layer

- Preliminary simulation results of 40Gb/s PM-QPSK transmission on a DWDM system with standard (i.e. G.652 SMF) and DCFs and equipped with 10Gb/s DWDM signals show that power of the 10Gb/s channels should be well below the power of the 40Gb/s channel in order to avoid XPM

Conclusions

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Acknowledgements

Some of the research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement nº 238875 (GÉANT)

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Thanks for your attention!

Questions?

[email protected]+31-30-2305 305

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What limits system performance?ASE (Amplified Spontaneous Emission)

- Amplifiers are used to overcome fiber losses.- Optical Noise is added by each amplifier.- Engineering rules usually defined for equal spans (e.g. 20 x 20dB) which is not

the case in the real fiber networks

() = 2 h n sp (G() – 1)

Slide courtesy of Kim Roberts, Nortel

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OSNR (Optical Signal-to-Noise Ratio) - Simple formula

N

j jin

jsp

P

NRh

OSNR 1 ,

,21

Tx RxOA OA OA

SMFDCF

repeater

OA OA

DCFSMFSMF

Pin,1 Pin,2 Pin,3 Pin,N-1 Pin,N

NF1

NF2 NF3 NFN-1 NFN

Parameter Description

h Planck's constant (J•s)

c speed of light (m/s)

R OSA resolution BW (Hz)

Pin Input power (W)

Nsp Noise Figure (linear)

ƒ

OSNR

Resolution bandwidth = 0.1nm

25

2729

3133

3537

3941

43

4547

49

0 40 80 120 160 200 240 280 320 360 400

Distance (km)

Cal

cula

ted

OS

NR

(d

B)

Simple formula, accurate to within a few tenths of a dB but sensitive information needs to be provided to fiber suppliers, which equipment vendors don’t like:• NF of amplifiers• launch power per channel• minimum required OSNR => need simplification

2525

In order to quantify optical link grade, we propose a new method of representing system quality: the FOM (Figure of Merit) for concatenated fiber spans

N

j

L j

FOM1

1010Lj, span losses in dBN, number of spans

  FOMA 5504B 5504C 1897

120km 120km 120km 80km 80km 80km

80km 80km 80km 120km 120km 120km

Total 600km

100km 100km 100km100km100km 100km

A

B

C

New method to quantify fiberlink quality, FoM (Figure of Merit)