prezentatCEF Networks Workshop

1. 1
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

2. 2
Outline
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•Since 2001, in CESNET network
•Single fibre lines 1 360 km of 6100 km - 22%

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Spectrum sharing - Single fibre lines
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
+ 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

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Spectrum sharing - Single fibre lines
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
+ 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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•L band - 60 nm vs C band - 35 nm
•294 km in operation, 235 km under upgrade

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S band
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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.
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Fibre spectrum sharing for R&D Networks
•UFE Prague – BEV Vienna, pair of unidirectional lambdas
•CESNET Prague – VUGKT Pecny, bidirectional dark channel
•Roughly 3 x smaller white phase noise
UFE Prague – BEV Vienna
CESNET Prague – VUGKT Pecny
Praha, September 16, 2014

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Extension to UFE Prague – VUGKT Pecny
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•Single path EDFA on 2 x 100km (62 mi) 19 + 19 dB line

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Discrete bidirectional single path amplification
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•C band SOA on 2 x 100km (62 mi) 19 + 19 dB line

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Discrete bidirectional single path amplification
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•S band SOA on 2 x 100km (62 mi) 19 + 19 dB line

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Distributed bidirectional single path amplification
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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.
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•Can we use it over dark channel?
•Yes, when dark fibre last miles available

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Ongoing work
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•Brno – České Budějovice
•Praha – Brno bidi amplified channel

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Conclusions
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
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)

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8th CEF networks workshop
Praha, September 16, 2014
All optical two-way time transfer in strongly heterogeneous networks
Thank you for kind attention! Questions? josef.vojtech(salamander)cesnet.cz

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2um (2000nm) band
8th CEF networks workshop
Praha, September 16, 2014
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.
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
Source: Richardson D.” Fiber Amplifiers for SDM Systems”, OTu3.G1, OFC2013

30. Praha, September 16, 2014
8th CEF networks workshop
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Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks

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OSNR
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
200 km Raman left, 100 km + 100 km EDFA right

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Motivation
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
Source: Schnatz H., Comparison of clocks using optical fiber links: recent results and future projects

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Motivation
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
•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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UFE Prague – BEV Vienna
8th CEF networks workshop
Praha, September 16, 2014
Fibre spectrum sharing for R&D Networks
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