Optical Networks
Josef Vojtěch
josef.vojtech/zavinac/cesnet.cz
www.ces.net
czechlight.cesnet.cz
19th Nov 2013
Optical Networks
Optical Networks
Outline
History
Transmission Fibers
Attenuation Limited Reach - Amplifiers

Doped fiber – EDFA, TDFA

Raman

SOA
OSNR Limited Reach
Impairments (CD, PMD, non-linearities)
WDM Transmission (WDM, DWDM, CWDM)
Present and Future Transmission Systems
Capacity Limits, SDM
Photonic Services, Precise Time Transfer
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A Little Bit of History (1)
Back to Antiquity (mirrors, fire beacons, smoke signals) [1]
Till the end 18th century with lamps, flags
1792 – Claude Chappe with mechanical „optical“ telegraph
1830 – the advent of telegraphy (e.g. Morse)
Submarine cables started before the first transatlantic in 1858
but was not working long, short message (one sentence)
from Queen Victoria to President Buchanan took 30 hours!
Initial assumptions: 3 words per minute but in reality less
than 1 word per minute, only 20 days than cable failed, 723
messages! 1866 its sucessor
Terestrial long haul in Russia, USA – telegraph along railways,
submarine preferable
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A Little Bit of History (2)
1876 – the invention of telephone (A.G.Bell, U.S. Patent No.
174 465)
1895 – radio by Marconi, big competition started
1940 – massive increase of pairs installed - 3 MHz coax-cable
system (repeater spacing 1 km), high freq. dependent loss
especially above 10MHz
1948 – 4 GHz microwave system
1975 – last most advanced coaxial system with 274Mbit/s
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A Little Bit of History (2)
Evolution of optical communication systems
1960 – the invention of laser (suitable transmission medium?)
1960s – optical fibre 1000 dB/km, 1970 20dB/km close to 1um
1st generation GaAs lasers 850nm, 10km regeneration

1980 – 45 Mb/s (1st generation) multi-mode fibres
2nd generation 1310 nm


1980s – 1310 nm, 1 dB/km, 100 Mb/s, multi-mode fibres
Late 1980s – 2 Gb/s, single mode fibres, repeater spacing 50 km
(2nd generation)
3rd generation 1550 nm

1990s – 1550 nm (problem with lasers, dispersion of fibres,
typical repeater spacing 60 -70km), 2.5 Gb/s or 10 Gb/s (3rd
generation)
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A Little Bit of History (3)
4th generation 1550 nm – WDM - DWDM, CWDM
Optical amplification, EDFAs developed late 1980s
1990s - DWDM, optical amplification (4th generation)
Today comercially available 100G waves each consumes
50GHz~0.4nm, 160 channels in C+L bands ie 1,6 Tb/s,
thousands of kilometers, coherent technology
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Optical Fibres - MM
1970: 20 dB/km (Kapron, Keck, Maurer), silica fibres
Multimode (MM), singlemode (SM) and fewmode (FM) fibres
Multimode: step-index (SI) or graded index (GI)
MM SI: modal dispersion: different rays disperse in time
because of the shortest (L) and longest (L/sinΦC) paths
MM SI: 10 Mb/s
MM GI: parabolic index, lower modal dispersion, higher bit
rates, 100 Mb/s
Plastic MM GI, for 1 GE (or even 10 Gb/s)
Attenuation: 1 – 4 dB/km, <10 dB/km for plastic
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Optical Fibres
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Optical Fibres - SM
Single mode (SM, Standard SMF, G.652) fibres
Supports only one so called „the fundamental mode of the
fibre“, all higher modes are cut off @ the operating
wavelength
An optical mode refers to a specific solution of the wave
equation (satisfies boundary conditions, spatial distribution is
constant as light travels along a fibre)
The cutoff wavelength is specified in ITU G.650, SSMF cutoff
approx. 1200 nm
0.2 dB/km@1550 nm, 0.4 dB/km@1310 nm
Best conventional fiber ever 0.1484dB/km
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Optical Fibres – SM types
ITU G.651 – MMF, new types suitable for 10G
G.652 SSMF, non-dispersion-shifted fiber, optimized for 1310nm (but
well usable in 1550nm and 100G coherent - big core diameter)
G.653, dispersion-shifted optical fiber, zero dispersion at 1550nm,
strong nonlinear effects (FWM)
G.654, low loss, no longer supported
G.655, nonzero dispersion-shifted, small dispersion at 1550nm
G.656, for S, C and L bands
G.657, G.652-like
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Optical Fibres - Special
Multicore fibres (3-20)
Photonic crystal fibres PCF
Refractive index experienced (“seen”) by propagating light
depends on size and shape of air holes in every point of structure
But speed of light similar to 300 000km/s (air), perhaps
promising for financial transactions
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Optical Reach -Transmitter
Conversion of electrical signals into optical streams
Light source LED or laser: Fabry-Perot (FP), Distributed Feedback
(DFB)
Modulation: direct or external (10 Gb/s, DWDM incl. tunable)
Output powers typicall: 0 dBm – 4 dBm
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Optical Reach
Tx power 1mW ~ 0dBm (P [dBm] = 10 log P[mW])
Receiver PIN diode or APD
Minimal needed Rx power– sensitivity, examples:
-45 dBm (32nW) @ 155Mbps – 180km
-36 dBm @ 1GBps – 144km
-24 dBm @ 10Gbps – ?
Reach extension – regeneration / optical amplification
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Optical Amplifiers
Rare earth doped fibre, Semiconductor (SOA), Raman
Erbium Doped Fibre Amplifiers (EDFA)
Really began a revolution in the telecommunications
industry
Late 1980s, Payne and Kaming (University of
Southampton)
OAs can directly amplify many optical signals
Analogous principle: Protocol, bit-rate transparent
EDFAs working in the 1550 nm window (C band and
later L band)
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Optical Amplifiers EDFA
High energy level, 1 μs
Metastable energy level, 10ms
980 nm
1480 nm
Amplified signal
Low energy level
Light Amplification by Stimulated Emission
Er atoms
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Optical Amplifiers EDFA
Er doped fibre, 10 m – 100 m
SIGNAL
SIGNAL
WDM
PUMP
WDM
PUMP
Forward, backward pumping
Forward: lowest noise
Backward: highest output power
980 nm: low noise
1480 nm: stronger pump sources (req. longer Er fibres)
1480 nm & backward; 980 nm & forward
Single or dual stage (for DCF)
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Optical Amplifiers EDFA
Output powers (5 Watts or more)
Gain (30 dB), not uniform across C (L) band
Input power (-36 dBm)
Noise Figure (NF): 3.6, typ 5-7dB, teoretical minimum 3 dB
ASE
For L band: long Er fibres (> 100 m)
Booster, in-line, preamplifiers
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Optical networks and equipment
OAs and Practical Deployment
Praha - Pardubice
Since May 17, 2002
Now gone
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Masarykova Univerzita, Brno
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Optical networks
Real deployments
OSA (One Side Amplification) – all components are located at
one place, for star topologies
Praha – Plzeň (OSA), 123 km, 34 dB, 1 GE
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Optical networks and equipment
OAs and Practical Deployment
Brno – České Budějovice, 308 km, 70 dB, 2,5 Gb/s, PoS,
without optical filters
JIHLAVA
RX
TX
TX
RX
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Optical networks and equipment
OAs and Practical Deployment
Brno – Ostrava, 235 km, 51 dB, 1 GE (tested for 2,5 G PoS),
without optical filters
TX
RX
TX
RX
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Optical Networks
Other Optical Dopped Fibre Amplifiers –
O band
Praseodymium Doped Fluoride Fibre Amplifier (PDFA)


1310 nm, not as energy efficient compared to EDFA, higher NF
Problems with fluoride fibres, not very widespread
Neodymium DFA

1310 nm, fluoride fibre
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S band
Optical Networks
Other Optical Dopped Fibre Amplifiers –
S band
• Thulium DFA (TDFA), 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
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Er
Tm
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S band cont.
Optical Networks
Other Optical Dopped Fibre Amplifiers –
S band
• Modified EDFA
– Can handle region about 1510-1530nm, 20dB gain, commercially
available, NF higher that TDFA
• Commercially unavailability of DWDM transceivers for this
region
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2um (2000nm)Optical
band Networks
Other Optical Dopped Fibre Amplifiers
•
•
•
•
•
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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Networks
2um (2000nm)Optical
band cont.
Other Optical Dopped Fibre Amplifiers
• 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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Semiconductor Optical Amplifiers
Based on conventional laser principles
Active medium (waveguide) between N and P regions
+ InGaAsP – small and compact components
+ Cost effective solutions, especially for O and S bands
+ High gain (up to 25 dB)
- Low output powers (15 dBm)
+Wide bandwidth
- High noise figure (7-8 dB)
-- Very short life time - cross gain effects
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Semiconductor Optical Amplifiers
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Raman Amplification
Both discrete but mainly distributed amplifier
Stimulated Raman scattering effect
Distributed amplification, a communication fibre itself is a gain
medium
Can add 40 km to increase a maximum transmitter-receiver
distance
Upgrading of existing links to add more channels
A quite weak effect in silica fibre – very high powers have to be
used
Safety problems (automatic laser shutdown - ALS)
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Raman Amplification
Counter-directionally pumping schemes
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Noise Limited Reach
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Noise Limited Reach
Receiver needs some minimal OSNR to achieve intended BER
(e.g. 1E-12)
Scenario 1: Span 80 km, Gain 18 dB, NF 6 dB, Pin 0 dBm.
Scenario 2: Span 100 km, Gain 22 dB, NF 6.5 dB, Pin 0 dBm.
Bit rate
1 Gbit/s
2.5 Gbit/s
10 Gbit/s
Bit rate
10 Gbit/s
40 Gbit/s
40 Gbit/s
100 Gbit/s
400 Gbit/s
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Type of
modulation
NRZ
NRZ
NRZ
Type of
modulation
NRZ
DPSK
PM-QPSK
PM-QPSK
PM-16QAM
Minimal OSNR
accepted
7 dB
11 dB
17 dB
Optical
Reach 1
40 000 km
15 920 km
4 000 km
Minimal OSNR
accepted
8.5 dB
11.5 dB
10.2 dB
14.2 dB
22.4 dB
Optical Networks
Optical
Reach 1
28 320 km
14 160 km
19 120 km
7 600 km
1 120 km
Optical Reach
2
17 000 km
7000 km
1700 km
Optical
Reach 2
12 500 km
6 300 km
8 500 km
3 300 km
500 km
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Optical Networks
Optical Fibres – dispersion
MM: Intermodal dispersion (pulse broadening, the most
important limiting factor)
SM: Intermodal dispersion is absent, pulse broadening is
present still because of Intramodal dispersion (or Groupvelocity dispersion CD), even laser pulses have finite spectral
width and pulses are modulated
CD: different spectral components of the pulse travel at
different speeds
Increases as the square of the bit rate
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Optical Fibres – CD
D = DM + DW
Material dispersion
Waveguide dispersion
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Optical Fibres – CD
G.652 (SSMF): Zero dispersion at 1310 nm
G.653 (DSF): Zero dispersion at 1550 nm
G.655 (NZDSF): Small dispersion at 1550 nm, positive/negative
Dispersion Compensating fibres (DCF)
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Chromatic Dispersion Compensation
Typical values (receivers can have different tolerance to CD!)
Bit rate (Gbit/s)
Maximum length of G.652 link (km)
2,5
1280
10
80
40
5
100 (25Gbaud)
3000 (coherent+DSP)
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Chromatic Dispersion Compensation
Dispersion compensating fibres (DCF)



A special kind of fibre, compensates all wavelengths (the only
solution for „grey“ transmitters)
Adds link loss (and money), especially for long-haul applications
Stronger non-linear effects (due to a smaller core diameter)
Fibre Bragg gratings (FBG)




Typically narrow-band elements – a stabilized DWDM laser is a
must
„Wide-band“ FBGs available today (for C or L band)
Signal filtering, spectrum shaping, tuneable compensators
Cost effective solution
Electronic post and pre compensation, GTE, VIPA, MZI
Tunable
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Optical nNtworks
Chromatic Dispersion Compensation
FBG
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Chromatic Dispersion Compensation
(FBG)
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Optical Fibres – PMD
Polarization Mode Dispersion (PMD)
The stochastic phenomenon
Fibre stress, temperature, imperfections
The fundamental mode has two orthogonally polarized
modes
The two components with different propagating speeds
disperse along the fiber
The difference between the two propagation times is
known as the Differential Group Delay (DGD)
PMD is a wavelength averaged value of DGD
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Optical Fibres – PMD
ITU proposed PMD values
Bit rate
(Gb/s)
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Maximum
PMD (ps)
PMD coefficient
for 400 km fibre
(ps/(km)1/2)
2,5
40
2,0
10
10
0,5
40
2,5
0,125
100(25Gbd)
30 (DSP)
1,5
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Optical Fibres – PMD
PMD is measured and quoted in ps for a particular span
and discrete components but its coefficient is in
ps/(km)1/2
PMD accumulates as the square root of distance of a link
A single span with high PMD dominates the total PMD
for the whole network
A big issue for older fibres (late 1980s, 80 000 000 km)
and higher bit rates (10 Gb/s and more)
Modern fibres have PMD of less than 0,5 ps/(km)1/2
Difficult to compensate in optical domain
In coherent systems compensated in DSP
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Nonlinear Optical Effects
When an intesity of electromagnetic fields becomes too
high, the response of materials becomes nonlinear
For optical systems, nonlinear effects can be both
advantageous (Raman and Brillouin amplification) and
degrading (Four Wave Mixing, Self Phase Modulation and
Cross Phase modulation)
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Nonlinear Optical Effects - SRS
Stimulated Raman Scattering (SRS)
A signal is scattered by molecular vibrations of fibre –
optical phonons
Can occur both in forward and backward directions
Shifted to longer wavelengths (lower energy) by 10 to
15 THz in the 1550 nm window
Wide bandwidth of about 7 THz (55 nm)
Maybe used for amplification (Raman fibre amplifiers),
so called counter directionally pumping schemes
In DWDM systems: transfer of power from shorter
wavelengths to longer ones
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Nonlinear Optical Effects - SBS
Stimulated Brillouin Scattering (SBS)
A signal is scattered by sound waves – acoustic phonons
Shifted to longer wavelengths (lower energy) by 11 GHz
in the 1550 nm window
Narrow bandwidth of about 30 MHz
A problem for monochromatic unmodulated signals
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Nonlinear Optical Effects
Self-Phase Modulation (SPM)
When the intensity of the signal becomes too high, the
signal can modulate its own phase
The refractive index is no longer a constant
Significant for fibres with small effective areas (G.655,
DCF)
Higher bit rates (10 Gb/s and higher)
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Nonlinear Optical Effects (SPM1)
Pin = 16,5 dBm
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Nonlinear Optical Effects (SPM2)
Pin = 22,7 dBm
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Nonlinear Optical Effects (SPM3)
Pin = 25,8 dBm
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Nonlinear Optical Effects (SPM4)
Pin = 30,1 dBm
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Nonlinear Optical Effects 100G (DP-QPSK)
Pin = 30,1 dBm
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Nonlinear Optical Effects
Cross-Phase Modulation (CPM)
A signal modulates the phases of adjacent channels
Difficult for amplitude and phase modulations ie
coherent technologies
Slow 1/10G OOK signals harm 100G DP-QPSK signals
Vendors recommend to use coherent-only solutions
without compensation DCFs or even CD compensation –
so called DCM-free designs
Problem with 10G wavelengths
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Nonlinear Optical Effects
Four Wave Mixing (FWM)
New „ghost“ signals appear in the transmission spectral
range
Depends on several factors like launched powers, the
CD, the refractive index, the fibre length
Severe limitations for G.653 fibres and DWDM
transmissions in the 1550 nm window (C band)
Solution to this problem is to deploy L band DWDM
systems (1565 nm – 1625 nm), where CD is high
enough
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Nonlinear Optical Effects (FWM1)
Pin = 20 dBm
83 km, G.652
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Nonlinear Optical Effects (FWM2)
Pin = 25 dBm
83 km, G.652
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Nonlinear Optical Effects (FWM3)
Pin = 27 dBm
83 km, G.652
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Nonlinear Optical Effects (FWM4)
Pin = 30 dBm
83 km, G.652
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Wavelength Division Multiplex System
[11]
Basic passive WDM principle for 2 channels over MM fibre
Still used, typically 1310+1550 nm over SMF
CWDM
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Optical Networks
Dense WDM - DWDM
[11]
Typically amplified, long distances
Thermally stabilized lasers and filters
Grids:
200 GHz
100 GHz
50 GHz standard ~ 0,4 nm (C band ~ 80 channels)
33 GHz submarine
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Transmission Systems
C(coarse)WDM
+ passive, non thermally stabilized lower power
consumption, less space, cheaper lasers and filters
- Limited number of channels, limited reach
Typically in MAN
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DWDM vs. CWDM
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Parameter
CWDM
DWDM
Wavelength
spacing
20 nm
1.6 nm (200 GHz)
0.8 nm (100 GHz)
0.4 nm (50 GHz)
The number of
wavelengths
18 (G.694.2)
32 (metro) in C band
80+80 (long distance)
in C+L bands
Laser technology
Uncooled DFB Cooled DFB
Bands
O+E+S+C+L
C or C+L
Filter technology
Thin film
Thin film, Grating,
AWG
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Present Transmission Systems
Common 50/100 GHz systems, C band, approx. 80/40 channels, C+L band
approx. 160 channels
Commercially available 25 GHz systems and e.g. undersea 33 GHz systems
Bandwidth demand satisfied by serial speed of single channel growth 2,5->10>40->100G
10->40G transition
40G NRZ tolerance very weak CD 50ps/nm (equals to 3km of G.652 fibre),
PMD 2,5 ps

ODB, DPSK proposed, but more strict design rules compared to 10G
DQPSK (20Gbaud)


NRZ
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ODB
DPSK
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DQPSK
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Present Transmission Systems
100G coherent DP-DQPSK (25GBaud) solves some issues

+ Works over 50 GHz grid

+ Design rules almost 10G; CD, PMD electronic compensation

- Sensitive to non-linearities, FWM->DCFs removal->coexistence with
present 10G channels?

- Cost of complicated modulation format (TX+RX) + necessity of
powerful DSPs and ADCs
TE
TM
Proposed alternative modulation formats: 16 QAM, OFDM, 3ASK-PSK,…
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Present Transmission Systems
TE
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TM
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Present Transmission Systems
Profits from integration
Source: www.oiforum.com
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Present Transmission Systems
„Digital“ DWDM system


Profits from photonic integration – photonic integrated circuits
(PIC)
Do not use optical processing (ROADM) but massive OEO
regeneration in nodes
DWDM system on chip, source: Infinera
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Future Transmission
Works on 400 Gb/s and 1Tb/s per one serial lambda
DP-DQPSK

High channel bandwidth
 ROADM + WSS have to support „flexi grid“
OFDM, 16 or 32 or 64-QAM with or without DP

High OSNR, low nonlinearities
 Raman or hybrid amplification
 Decrease spacing of inline amplifier huts
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Future Transmission - Hero
Experiments
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Channel Capacity Limit
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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Further Capacity Increase
Fibre attenuation decrease, decrease of nonlinearities
Amplifier NF decrease, bandwidth increase
Spatial Division Multiplexing
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Future Transmission
New Fibers
Multicore fibers
[Jun Sakaguchi, Proc. OFCNFOEC2011, OWJ2]
Issues:

Amplification – experimental EDFA, Raman

Cross-talk - MIMO

Splices ?

Connectors ?

New fibers instalation
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ECOC12, NTT: Over 1Pbit/s transmission
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Future Transmission
New Fibers
Few mode fibers - FMF
[OFCNFOEC2011,PDPB9]
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Further Bandwidth
Practical experiences with L band, in lab at first
Single span 150 and 200km G.652 fibre on spools
High launched power about +8.5 and +14.5 dBm/ch
Power transfer (Raman effect) from lower to higher
wavelengths

0.58/0.38 dB
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Further Bandwidth
Field deployment – C + L
• EF line Praha-Brno 300km, mixture of G.655 fibre
with G.652 local loops
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Bandwidth Virtualization
Photonic Service
End-to-end connection between two or more places in
network
Described by Photonic-path and allocated bandwidth


Photonic-path is a physical route that light travels from
the one end point to the other or to multiple other end
points respectively
Allocated bandwidth is a part of system spectrum that is
reserved for user of Photonic Service all along the
Photonic-path.

Minimal impact of network (no processing) on transmitted
data

Path is all-optical , no OEO except special cases.
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Photonic Services
Advantages





Transparency to modulation formats
Low transmission latency as the shortest photonic path
is formed
Constant latency (i.e. negligible jitter), because non or
only specially tailored electrical processing is present
Stable service availability (due allocated bandwidth) with
some exception for protection switching
Future-proof design thanks to grid-less bandwidth
allocation
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Photonic Services – Real Time
Real time has nothing to do with speed, but with timeliness
constraints
For the interaction with external processes (processes running
outside network) real time network services are needed if timing of
interaction limits quality or even the acceptability of network
application.
Real-time network service should respond to an event within a
predetermined time (i.e. there are "real time constraints" operational deadlines from event to system response). The timeliness
constraints or deadlines are generally a reflection of the physical
process being monitored or controlled.
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Photonic Services – Precise Time
Transmission
Comparison of atomic clock scales on live
network : CESNET (CZ) + ACONET (AT)
Tests in 2010
Comparison of time scales between Czech and Austrian
national time and frequency laboratories in Praha and
Wien (IPE-BEV) over operational DWDM since Aug 2011
– RUNNING
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Precise Time Transmission
Photonic path – dedicated lambda over operational DWDM
network:




Mixture of fibre types (G.652/655)
Mixture of transmission systems Cisco/Open DWDM Czechlight
Mixture of CD compensation types (DCF, FBG)
One way distance 550km, total attenuation 137 dB
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Precise Time Transmission
Next line in service since summer 2013



CESNET-VUGKT (Praha-Pecný), single fiber bidirectional line 76km
Passive transmission of time, parallel data are amplified
Significantly smaller noise
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Precise Time Transmission
Amplified bidirectional transmission necessary for longer distances
Tested in lab on fiber spools
Must be very careful with amplifiers gains
Reflections creates feedback and line is lasing
Tx
Rx
Rx
Tx
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Acknowledgements
Lada Altmanová, Michal Altmann, Miloslav Hůla,
Miroslav Karásek, Jan Nejman, Václav Novák, Martin
Míchal, Stanislav Šíma, Karel Slavíček, Pavel Škoda, Jan
Radil and Jan Gruntorád
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References 1
[1] Agrawal G.P., „Fiber-Optic Comminications Systems“, 2002.
[2] Kartalopoulos S.V., „DWDM Networks, Devices and Technology“,
2003.
[3] Ramaswami R., Sivarijan K.N., „Optical Networks“, 2nd edition,
2002.
[4] Radil, J. - Karásek, M., „Experiments with 10 GE long-haul
transmissions in academic and research networks.“,
In: I2 member meeting, Arlington, VA, 2004.
[5] Vojtěch J., „CzechLight and CzechLight amplifiers“. In: 17th TFNGN meeting, Zurych, Switzerland, April 2005.
[6] Vojtěch J., Karásek M., Radil J., „Extending the Reach of 10GE
at 1310 nm “. In: ICTON 2005 meeting, Barcelona, Spain, 2005.
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References 2
[7] www.seefire.org, Deliverables
[8] czechligh.cesnet.cz, Publications
[9] ECOC 2004 , 2005 proceedings
[10] OFC 2004 , 2005 proceedings
[11]http://www.cisco.com/univercd/cc/td/doc/product/mels/cm150
0/dwdm/dwdm_ovr.htm
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Thank you for your attention!
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Laboratory experiments
1GE NIL


300 km G.652 (EDFA only)
325 km G.652 (EDFA + Raman)
10GE NIL




2x10G+2x1G WDM 202km G.652 (EDFA + DCF)
2x10G WDM 250km G.652 (EDFA + Raman + DCF)
10G DWDM 302 km G.655+652 (EDFA + Raman)
8x10G DWDM 250km G.652 (EDFA + FBG)
10GE NIL bidirectional (single fibre) transmission
 2x4x10G 210km G.652 (EDFA + FBGs)
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Laboratory experiments
250 km G.652
Tx1
Rx1
.
.
.
.
EDFA 1
Tx8
EDFA 2
MUX
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Rx8
FBG
Optical Networks
DEMUX
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Laboratory experiments
Bidirectional transmission over single fibre
210 km G.652
EDFA 1
EDFA 2
Tx1
Tx5
λ1+λ2+λ3+λ4
λ5+λ6+λ7+λ8
λ5+λ6+λ7+λ8
λ1+λ2+λ3+λ4
Tx4
Tx8
MUX 1
EDFA 3
EDFA 4
FBG 1
FBG 2
λ5+λ6+λ7+λ8
λ1+λ2+λ3+λ4
DEMUX 1
DEMUX 2
Rx5
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Rx8
Rx1
Optical Networks
Rx4
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Real deployments
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PDFAs/SOAs and Ramans for 1310 nm
Configuration
Reach (km)
Guaranteed
10
In lab, no amps
30
Booster
85
Booster and preamp
120
Dual booster and Raman
135
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PDFAs/SOAs 1310 nm
Eye diagram after preamp, l = 100 km
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PDFAs/SOAs for 1310 nm
Eye diagram after preamp, l = 120 km
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PDFAs/SOAs for 1310 nm
Eye diagram after preamp and optical filter, l = 120 km
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Optical networks and equipment
First 100Gb/s tests in Czech Republic
Alcatel-Lucent and CESNET, 2011
Laboratory and field tests over CESNET2 network
100G coherent transceivers can work in compensated networks –
possible to deploy 10G OOK NRZ and 100G
Over 1063km!
ALU system verified to work with Cisco
and CzechLight – multivendor environment
possible in production networks!
100G possible on single fibre lines! 655km!
Alien wavelengths possible – 100G
even together with Photonic Services
(e.g. atomic clocks comparison), 300km!
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100/10/1 Gb/s tests
Oclaro (former Opnext), 2012
More laboratory verification
100G together with 10G and 1G NRZ
Even slower signals, 100Mb/s as Photonic Service
Nothinh In Line with 100G coherent:
240 km with EDFAs only
277.5 km with EDFAs and Ramans
NIL with 10G was about 250 km
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