Transcript A Disorganised Approach to Histogram Analysis

Control of Optical Fibre
Communications Networks
Peter Farrell
ARC Special Research Centre for Ultra-Broadband
Information Networks
Utopian Vision
ALL OPTICAL NETWORK
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Analogy with Internet
Transmitter sends photons through the network (transparently)
to Receiver
Format independent
Bit-rate independent
Protocol independent
The Network is very clever (BRIGHT?) and can figure
everything out so that your information goes to its destination
perfectly
A bit like
– electricity too cheap to meter from the nuclear industry
OR
– the paper free office
Interesting Problems to Solve to build Utopia
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Finance
All the routing problems in the Network
BIG optical switches
Control of adjustable elements in the Network
HOW BIG?
Worldwide?
Continental
Darwin
Katherine
Derby
Cairns
Tennant Creek
Mt. Isa
Cloncurry
Townsville
Hughenden
Sth. Hedland
Mackay
Charters Towers
Mt. Newman
Rockhampton
Alice Springs
Bundaberg
Mullewa
Meekatharra
Toowoomba
Geraldton
Brisbane
Glendambo
Kalgoorlie
Ceduna
Perth
Esperance
Pt. Augusta
Clare
Adelaide
Newcastle
Parkes
Sydney
Hay
Canberra
Established by 1993
Melbourne
Established by 1997
Hobart
Metro
Campus
Size matters because …
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Different transmission issues for
– 100 m
building / campus
– 1 km
campus
– 10 km
metro
– 100 km metro/continental
– 1000 km continental
– 10000 km world
All optical network requires (?) 10000 km infrastructure for a
100 m connection
Optical Network Control
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Most published work is on making connections, fault location,
contention avoidance and so on
Very little on control of adjustable elements in the network to
optimise or at least improve the performance
Alternative is to grossly over engineer the hardware
Point to Point Link Impairments
Tx
DisCo
Tx
Rx
Rx
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Tx
– Chirp
– Noise
– Finite extinction ratio
Mux/Demux
– Filter drift
– Crosstalk
Transmission fibre
– Loss
– Dispersion
– Nonlinear effects
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Amplifiers
– ASE/ Noise
– Crosstalk
– Wavelength dependent gain
Rx
– Finite sensitivity
– Noise
– Bandwidth
Everywhere
– PMD
Point to Point Link Adjustments
Tx
DisCo
Tx
Rx
Rx
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Tx
– Power, wavelength, chirp, modulation format, extinction ratio
MUX/DEMUX
– Temperature
Amplifier
– Gain, gain flattening filter, tilt
Dispersion compensation
Rx
– Gain (APD or preamp gain)
– Decision Threshold
– Decision Point
Long Haul Link Configuration
10 Gbit/s over >1000 km
Tx Terminal
1
41
Rx
Tx
Tx
40
Rx Terminal
Tx
C Blue
C Blue
DCF
Tx
DCF
81
Tx
L
M
…
LF
L
M
R
Rx
C Red
R
Rx
Rx
Tx
L Blue
120 Tx
DCF
L Blue
LF
LF
DCF
LF
DCF
CC
C
121 Tx
CCC
LF
DCF
DCF
CCC
DCF
CC
C
Rx
Rx
Rx
Tx
Rx
L Red
160 Tx
Rx
Rx
DCF
LF
L
M
R
DCF
Transmission
Fibre
DCF
LF
C Red
Tx
Amp n
Transmission
Fibre
DCF
LF
Tx
80
Amp1
Transmission
Fibre
Rx
L Red
Rx
Point to Point Link with OADM
Tx
DisCo
Tx
Rx
Rx
Tx
DisCo
Tx
Rx
Rx
O
A
D
M
OADM
X
OADM
All Optical Network
Rx
Tx
Rx
Tx
Lots of Feedback Loops …Amplifier
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Issues
– Measurement accuracy
– Signal reduction
– Transient response
Feedback & Control
Lots of Feedback Loops … Dispersion Compensator
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Issues
– Location
– Accuracy
– Signal reduction
Dispersion
Compensator
Dispersion
Measurement
Lots of Feedback Loops … Pre-emphasis
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-201525
-25
Relative Power (dB)
-30
-35
-40
-45
-50
1530
1535
1540
1545
1550
Wavelength (nm)
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1555
1560
1565
1570
Shares OSNR, BER or received power equally among channels by
adjusting transmit power with time varying disturbances
Simple linear iterative algorithm (and variations on this theme)
(Chraplyvy et al 1992)
-20
-30
Relative Power (dB)
i
Pnew
 PTOT
 Pi


OSNRi 


j
P
  OSNR 
j 
 j

-25
-35
-40
-45
-50
1525
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1530
1535
1540
1545
1550
Wavelength (nm)
Non-linear channel!!!!
Like to know
– if non-linearity is significantly affecting performance
– Origin of non-linearity
1555
1560
1565
1570
Feedback Loops
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What do we measure and where?
– BER
– Channel Powers
– OSNR
– Dispersion
– Non-linearity
– Crosstalk
Local?
Central?
Tradeoffs between non linearity, dispersion and gain
How many channels?
Circuit switched or Packet switched?
Interaction with routing algorithms
Control..
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THE WHOLE NETWORK – WORLD DOMINATION
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Link by Link
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Device by Device
All Optical Network
Rx
Tx
Rx
Tx
Point to Point Link Impairments
Tx
DisCo
Tx
Rx
Rx
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•
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Tx
– Chirp
– Noise
– Finite extinction ratio
Mux/Demux
– Filter drift
– Crosstalk
Transmission fibre
– Loss
– Dispersion
– Nonlinear effects
•
•
•
Amplifiers
– ASE/ Noise
– Crosstalk
– Wavelength dependent gain
Rx
– Finite sensitivity
– Noise
– Bandwidth
Everywhere
– PMD
Point to Point Link Adjustments
Tx
DisCo
Tx
Rx
Rx
•
•
•
•
•
Tx
– Power, wavelength, chirp, modulation format, extinction ratio
MUX/DEMUX
– Temperature
Amplifier
– Gain, gain flattening filter, tilt
Dispersion compensation
Rx
– Gain (APD or preamp gain)
– Decision Threshold
– Decision Point
Conclusion
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Model network
Use standard control theory to construct a controller