Fibre spectrum sharing_for_rd_networks

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Fibre spectrum sharing for R&D Networks

Josef Vojtěch

http://www.ces.net http://czechlight.cesnet.cz/en

8th CEF networks workshop

Praha, Czech Republic September 15-16, 2014

http://www.ces.net/

http://czechlight.cesnet.cz/en

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Outline

8th CEF networks workshop Praha, September 16, 2014


• Why share capacity/spectrum

– Single fibre bidirectional lines

– Photonic Services – T&F Infrastructure

• Capacity of fibres

– Free spectrum (L band, S band)

• Deployed links

• Single path amplified lines

– Discrete amplification

– Lines without inline equipment

• Conclusions, Q&A

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Spectrum sharing - Single fibre lines



• Since 2001, in CESNET network

• Single fibre lines 1 360 km of 6100 km - 22%

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+ Fibre rental savings average 40% from 0.5

EUR/meter/year *, 1360 km ~ 272 kEUR/year

- Half capacity (4.4 Tbps @ 100G)

*Sima S. et al., Deliverable D3.2v3-Economic analysis, dark fibre usage cost model and model

of operations, Porta Optica project, Online: http://www.porta-optica.org/publications/POS-

D3.2_Economical_analysis.pdf

http://www.porta-optica.org/publications/POS-D3.2_Economical_analysis.pdf





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+ Provide the same services (e.g. SDN) as fibre pairs

• ROADMs since 2011

• Transmission of 100G

• Flex-grid ROADMs can be deployed when useful

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Spectrum sharing – Photonic services



• Support real time applications

• Applications requiring low and stable latency

• Other timing sensitive applications (e.g. time,

frequency transmissions)

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T&F Infrastructure under development



• Improve stability of UTC(TP) – add Cs clocks and H masers

• Compare UTC approximation with neighbouring countries

• Distribute precise time and frequency

• Share fibre with data, length approx. 1400 km

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Capacity of Fibers



• Legacy 10G – 88 ch – 0.88 Tbps

• Present 100G – 88 ch – 8.8 Tbps

• Emerging – 58 ch á 400Gbit/s – 23.2 Tbps *

• L band – additional 60nm

– 100G 15 Tbps

– 400G 40 Tbps

• Low loss window in SMF

– 400nm 0.27 Pbps

• * 400Gbit/s, 75GHz, DP-16QAM

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Capacity of Fibers



• For long haul we are mainly missing high gain,

low noise and reliable amplifiers

• L band – EDFA - OK

• S band – ?

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L band



• L band - 60 nm vs C band - 35 nm

• 294 km in operation, 235 km under upgrade

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S band



• Suitable rare earth Thulium, but poor efficiency in silica, due to high non-radiative decays

• TDFAs based on fluoride fibres commercially available

– 1460-1500 nm 19dB gain and 19dBm output

– Can’t be spliced with silica fibres, hydroscopic

• Double pumped TDFA in silica with dopants – not commercially available

Er+ Tm+

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S band cont.



• Raman amplification – pump at 1390 nm suffers from higher attenuation than for C band

• Modified EDFA

– Can handle region about 1510-1530nm, 20dB gain, commercially available, NF higher that TDFA

• SOA – work well, at least for two T&F channels

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UFE Prague – BEV Vienna



• Comparison of UTCs, 550 km (342 mi) 137 dB

• Pair of unidirectional lambdas in DWDM systems

• Dark fiber in urban last miles

• In operation since 2011

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CESNET Prague – VUGKT Pecny



• Passive channel within bidirectional DWDM system

• In operation since 2013

• 78km (48 mi) 22dB

Praha, September 16, 2014

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Time transfer stability



• UFE Prague – BEV Vienna, pair of unidirectional lambdas

• CESNET Prague – VUGKT Pecny, bidirectional dark

channel

• Roughly 3 x smaller white phase noise


CESNET Prague – VUGKT Pecny

Praha, September 16, 2014

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Extension to UFE Prague – VUGKT Pecny



• Extension via dark channel created within rented passive

CWDM lambda

• Total attenuation of 43 dB, ideally divided into 22 + 21 dB

• Bidirectional single path discrete amplifier can provide gain

up to approximately 20 - 22 dB

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Bidirectional single path amplification



• EDFA, SOA, Raman works bidirectional naturally

• Why we don’t operate them bi-directionally?

• Different designs to limit influence of back-reflections

• Multi-path amplification acceptable for time but not for

frequency transfer – decision to avoid it

Figures: Sliwczynski et al, Frequency transfer in electronically stabilized fiber optic link exploiting bidirectional optical amplifiers

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Discrete bidirectional single path amplification



• Single path EDFA on 2 x 100km (62 mi) 19 + 19 dB line

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• C band SOA on 2 x 100km (62 mi) 19 + 19 dB line

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• S band SOA on 2 x 100km (62 mi) 19 + 19 dB line

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Distributed bidirectional single path

amplification



• Perfect when middle of line inaccessible

• Based on stimulated Raman scattering

• Lab results on 200 km 38 dB line

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Distributed bidirectional single path

amplification cont.



• Can we use it over dark channel?

• Yes, when dark fibre last miles available

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Ongoing work



• Brno – České Budějovice

• Praha – Brno bidi amplified channel

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Conclusions



• There is available spectrum in fibres still

• Special services need special treatment

• Discrete single path optical amplification challenging -

(reflection, equal powers), usable for spans < 20 dB

• Distributed Raman amplification can help

• Interesting choice are SOAs, offering all semiconductor

solution able of operation also outside C and L bands.

• Single path amplified passive channel in DWDM on

distances of about 325km (202 mi) and 385 km (240 mi)

needs to be established

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Acknowledgement



Lada Altmannová, Michal Altmann, Jan Gruntorád,

Ondřej Havliš, Miloslav Hůla, Martin Míchal, Jan

Radil, Vladimír Smotlacha, Stanislav Šíma, Pavel

Škoda

Work was supported by Czech Institutional funding

of research by project Large Infrastructure

CESNET LM2010005 (www.ces.net)

http://www.ces.net/

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All optical two-way time transfer in strongly

heterogeneous networks

Thank you for kind attention!

Questions?

josef.vojtech(salamander)cesnet.cz

mailto:[email protected]

mailto:[email protected]

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2um (2000nm) band


Fibre Capacity Increase for New Services

• Experimental TDFA operation

• Bandwidth 1910-2020nm

• Small signal gain 35dB

• NF 5-7dB

• Silica glass

Li Y. et al,”Thulium-doped Fiber Amplifier for Optical Communications at

2μm”, OFC2013

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2um (2000nm) band cont.



• Hollow core photonic bandgap fibers

• Minimal latency, neff close to 1, propagation speed

almost c, not 2/3c

• Nonlinear coefficient 0.07% of SSMF

• Losses still in order of 4.5dB/km in 2um

• Theoretically losses can go down to 0.15 dB/km

• 1966 Charles K. Kao fiber

1000dB/km

Source: NKT Photonic

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HC PBGF losses prediction



Source: Richardson D.” Fiber Amplifiers for SDM Systems”, OTu3.G1, OFC2013

Praha, September 16, 2014 8th CEF networks workshop 30


• Shannon’s law C = B . log2 (1+SNR)

• C/B (capacity per unit bandwidth) is limited by noise

• And non-linearities too

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Time Transfer Adapter



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OSNR



200 km Raman left, 100 km + 100 km EDFA right

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Motivation



Source: Schnatz H., Comparison of clocks using optical fiber links: recent results and future projects

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Motivation



• More interconnected clocks (Cs primary standards and H

masers) improve accuracy and stability of the time scale

• “Interconnection” means time transfer

Chip size atomic clock

Cesium fountain clock at

NPL UK, height of 2.5 m

Acetylene

stabilized

laser

Optical

frequency comb

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Motivation



• Traditional satellite based methods (GPS, TWSTFT) are

reaching their limits

• Increased interest in optical fiber based transfer: theoretical

studies, laboratory and also field implementations

Source: S.Droste et al, “Optical Frequency

Transfer over a single span 1840 km Fiber Link”

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Economical aspects of T&F infrastructure



• Total fibre line length 1 400 km (870 mi)

• Single fibre transfer is advantage for Time and must for

Frequency transfers

• Fibres rental annual cost (based on average price*)

EUR 420 000 ( $560 000 )

• Share infrastructure with data

*Sima S. et al., Deliverable D3.2v3-Economic analysis, dark fibre usage cost model and model

of operations, Porta Optica project, Online: http://www.porta-optica.org/publications/POS-

D3.2_Economical_analysis.pdf






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Heterogeneity



• T&F infrastructure

– Pair of unidirectional channels in DWDM (same λs)

– Passive channel in single fibre DWDM (different λs)

– Dark fibres

– Single path amplified passive channels in DWDM system

(different λs)

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Interaction of time transfer with coherent

100 Gbps transmission



• Field verification 2011 (vendor 1)

• Neighbouring 100 GHz channels, 300 km (186 mi) of

G.655 fibre

• Routine operation since Feb 2013 (vendor 2)

• Same line as above + spectral displacement

No observable influence

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Propagation time changes

Left: Seasonal October 7 2011 - March 14 2012 appr. 350ns,

1.3 ∙ 10−4 of avg. delay 2788 µs

Right: Daily changes 4-7ns

Technology

Fibre spectrum sharing_for_rd_networks