Josef Vojtěch, Miroslav Karásek, Jan Radil

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ALL-OPTICAL CHROMATIC DISPERSION COMPENSATION IN LONG-HAUL TRANSMISSION OVER 225km –

WITH NO INLINE AMPLIFICATION

Aug 29, 2007 CSN 2007

Palma de Mallorca, Spain 2

All-optical chromatic dispersion compensation

Outline

Motivations

CD compensation techniques

Laboratory setup

Experimental results

Conclusions

Aug 29, 2007 CSN 2007

Majority of installed fibres – ITU-T G.652, SSMF

Designed for operation in O band

C band – attractive area of operation (low IL, EDFAs, …)

CD coefficient around 1550 nm ≈ 16.8 ps/(nm * km)

CD limits reach significantly 10G NRZ - 90 km of SSMF

40G NRZ - 5 km of SSMF

100G NRZ - 900 m of SSMF !!!

Must be mitigated or compensated

Motivations I

Aug 29, 2007 CSN 2007

CD management studied intensively in regular setups

Motivations II

80 km SSMF

DCF DCF DCF

80 km SSMF

In Research and Educational Networks sometimes not possible or economically reasonable have active components between the transmitter and the receiver

Nothing-in-line (NIL) approach

CD compensation in long-haul NIL setups – relatively unknown

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1G NIL 300 km G.652 (EDFA only) 325 km G.652 (EDFA + Raman)

10G NIL 2x10G+2x1G WDM 202km G.652 (EDFA + DCF) 8x10G DWDM 250km G.652 (EDFA + FBGs) 10G DWDM 302 km G.655+652 (EDFA + Raman)

10G NIL bidirectional (single fibre) transmission 2x4x10G 210km G.652 (EDFA + FBGs)

Motivations II – NIL results

Aug 29, 2007 CSN 2007

Electrical pre or/and post processing

All-optical compensating elements:

CD compensation

Dispersion compensating fibre (DCF)

Fibre Bragg grating (FBG)

Gires-Tournois etalon (GTE)

Virtually-imaged phase-array (VIPA)

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All-optical compensating elements comparisonBroad-band

IL [dB] Tunable Slope match

DCF 16km YES 8.9 Semi NO

FBG NO 2.9 YES YES

FBG YES 3.5 NO YES

GTE NO 2 YES NO

GTE YES 7 NO YES

VIPA NO 7 YES NO* Elements compensating CD of 100 km SSMF are compared

** Table based on product information known to authors

Aug 29, 2007 CSN 2007

TX - 8 x 10 GE DWDM XFPs 1550.12 - 1556.55 nm

225 km of SSMF on reels (granularity 50 km and 25 km) CD +3780 ps/nm

Four DCF modules -1370, -946, -689 and -343 ps/nm

Packet error rate measured by Packet Blazer 10GigE FTB-5810G

Lab setup I – DCF based

DCF DCF225 km of SSMF

Booster EDFA Preamp EDFAs

Aug 29, 2007 CSN 2007

Compensated value -3400 ps/nm, 90% of line CD

Channelized fixed FBGs

Chanelized tuneable FBGs

Broadband fixed FBGs

Channelized tuneable GTEs

Lab setup II – alternative elements

225 km of SSMF

Booster EDFA Preamp EDFA

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Back-to -back eye-diagram of transmitter

Lab setup cont.

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Tolerance to composite launched power – post compensation

Experimental results - DCFs

Launched power tolerance post comp. only

20 21 22 23 24 25 26 27 28 29 30

Composite Pin [dBm]

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Tolerance to composite launched power – pre compensation 9%

Launched power tolerance - precomp. ratio 9%

20 22 24 26 28 30

Composite power in [dBm]

pr 9% po 79%

pr 9% po 61%

pr 9% po 54%

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Tolerance to composite launched power – pre compensation 18 and 25 %

Launched power tolerance - precomp. ratio 18, 25%

20 22 24 26 28 30

Composite Pin [dBm]

pr 18% po 70%

pr 18% po 61%

pr 25% po 64%

pr 25% po 54%

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Experimental results – alternative elements

Launched power tolerance

20 22 24 26 28 30

Composite Pin [dBm]

chann. FBG

chann. TFBG

broadband FBG

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Experimental results – broadband FBGs

21 22 23 24 25 26 27 28 29 30

Composite Pin [dBm]

BFBG 79%

BFBG 90%

BFBG 97%

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Experimental results – channelized FBGs

-9-8-7-6-5-4-3-2-10

21 23 25 27 29

Composite Pin [dBm]

CFBG 79%

CFBG 85%

CFBG 90%

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Experimental results – channelized GTEs

-9-8-7-6-5-4-3-2-10

21 23 25 27 29

Pin [dBm]

CGTE 79%

CGTE 85%

CGTE 90%

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Tolerance to compensation ratio – post compensation

Experimental results – tunable elements

Post compensation

60% 65% 70% 75% 80% 85% 90% 95% 100%

CD compensation [ps/nm]

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Influence of post compensation ratio - TCGTEs

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Tolerance to compensation ratio – pre compensation 9%

Pre compensation 9 %

60% 65% 70% 75% 80% 85% 90% 95% 100%

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TCGTEs - 71% post compensation TCFBGs - 71% post compensation

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Pre compensation 18%

60% 65% 70% 75% 80% 85% 90% 95% 100%

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Conclusions - DCFs

Post compensation - error free transmission in quite small range (about 60 – 70%)

Small pre compensation 9% - error free transmission range grows to (about 54 - 79%)

Further increase of pre compensation – lower power threshold of error free operation but decreases power range significantly

Aug 29, 2007 CSN 2007

Conclusions – alternative elements

GTEs allow lower launched input powers

Broadband FBGs easily handle high launched powers

Both fixed and tuneable channelized FBGs perform nearly identically; tuneable ones a little worse due to higher IL

Small pre compensation 9% - error free transmission range grows significantly again

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Conclusions

DCFs - well known, widely deployed and broadband but bulky, lossy, prone to non-linear effects and expensive

FBGs - commercially available, lower IL, broadband (some), tunable (some), cost effective

GTEs - very low IL, tunable, cost effective but not so widespread and available

VIPAs - not tested yet, commercial availability limited

Next challenge CD compensation at 40G

Aug 29, 2007 CSN 2007

Acknowledgement

Lada Altmanová

Jan Gruntorád

Stanislav Šíma

This research has been supported by the Ministry of Education, Youth and Sport of the Czech Republic under research plan no. MSM6383917201 called “Optical National Research Network and Its New Applications”.

Aug 29, 2007 CSN 2007

All-optical chromatic dispersion compensation Thank you for your kind attention!

Josef Vojtěch, Miroslav Karásek, Jan Radil

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