ROADM Technologies for Flexible - Tbitsec Optical Networks
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Transcript of ROADM Technologies for Flexible - Tbitsec Optical Networks
© 2014 Finisar Corporation
ROADM Technologies for Flexible, Tbit/sec Optical
Networks
Simon Poole
Director, New Business Ventures
© 2014 Finisar Corporation 2
ROADM Proliferation
ROADMs are used to manage transparent traffic
through the intersections of a WDM network;
3 prime functions: Wavelength Switching
Amplification
Signal Integrity Monitoring
2
Switching Cost Relative to OSI Layer
© 2014 Finisar Corporation 3
Problem: How to reduce cost of transmission
Increase Capacity
Coherent Nyquist Filtering
Superchannels Flexible Grid
Amplifiers Monitoring
Defragmentation etc
Dual WSS
Amplifiers
Reduce Capex
Route & Select
CD/CDC
Size
Power
Reduce Opex
Cost of Transmission
($/Gb/sec/km)
© 2014 Finisar Corporation 4
Increasing Capacity: Nyquist & Superchannels
Third generation coherent
transmitters add a filtering
(digital/analog) at transmitter to
minimise optical bandwidth of
signal (Nyquist output)
A superchannel is a multi-
carrier group of channels that
is operationally managed as a
single channel and which can
be presented to higher
networking layers as a single
higher data rate channel. (May
or may not be Nyquist filtered).
QPSK Re
lati
ve
Po
we
r (d
B)
Normalized Freq (GHz)
16QAM Re
lati
ve
Po
we
r (d
B)
Normalized Freq (GHz)
© 2014 Finisar Corporation 5
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
-25 -20 -15 -10 -5 0 5 10 15 20 25
Rel Freq (GHz)
Rel IL
(d
B)
-3.0
-2.5
-2.0
-22 -21 -20 -19 -18 -17
Rel Freq (GHz)
Rel
IL
(d
B)
Flexible Grid WSS
First generation WSS allocated a
single channel to a single pixel
LCoS-based WSS use a flexible
matrix-based wavelength switching
platform with megapixel matrices
which allows programmable
channel bandwidth
© 2014 Finisar Corporation 6
From Fixed-grid to Flexgrid
LCoS technology allows arbitrary channel bandwidth
Trade-off between flexibility and OSS requirements
12.5GHz slices as per ITU G 694.1 (Feb 2012) supports legacy
fixed-grid as well as Flexgrid
© 2014 Finisar Corporation 7
Flexgrid & Superchannels
Flexgrid™ + superchannels with
Nyquist Filtering for maximum
Spectral Efficiency
Fixed Grid WSS require
interchannel guard-bands
35 GHz Pass Bands 15 GHz “Dead Zones”
Flexgrid™ WSS +
superchannels allow denser
channel packing by eliminating
inter-channel guard-bands
Up to 5 THz Pass Band, 15 GHz “Dead Zone”
© 2014 Finisar Corporation 8
Advanced Flexgrid Functionality
No Limit to Superchannel spectral width
37.5 GHz – 5 THz in 6.25 GHz increments
Intra-channel attenuation control
Attenuation range: 0 to 20 dB
Intra-channel attenuation control of each 6.25 GHz section of a channel
Enables equalization across super channels
Dynamic and scalable channel width
Hitlessly widen, narrow or migrate a channel with 6.25 GHz resolution
Established traffic unaffected
Simplifies defragmentation
© 2014 Finisar Corporation 9
Flexgrid WSS: a proven technology
Finisar has deep experience in LCoS WSS since 2004
More than half of Finisar’s shipped WSS feature flexible grid
functionality
Common LCoS Platform
Single WSS: 1x4 – 1x20 Dual WSS: 2x1x20, 2xMxN
© 2014 Finisar Corporation 10
Example ROADM Configurations
ROADM design depends on many factors
Network Design
Node Degree(s)
Electronic vs Optical switching
Expandability vs Initial Cost
etc
Traditional Broadcast and Select
Colourless, Directionless (CD)
Colourless, Directionless, Contentionless (CDC)
© 2014 Finisar Corporation 11
Broadcast and Select ROADM
Passive split on Drop-side
WSS on Add-side
AWG for wavelength
mux/demux
Fixed Grid
Coloured Add/Drop
100% Add/Drop of 88
channels
2x100 GHz AWGs on
add side for lost cost
Fixed-grid OCM
Classic (B&S) ROADM O
CM
44 ch AWG 88 ch AWG 44 ch AWG
1x9 W
SS
8x8 Span
Crossconnect
8x8 Span
Crossconnect
1x8 s
plitt
er
88 ADD 88 DROP
© 2014 Finisar Corporation 12
Colourless, Directionless (CD) ROADM
Typical Requirements
8 degrees with 100% Add/Drop of 96
channels
Flexgrid
NB Limited drop-side filtering – only
works for coherent systems
Typical Modularity
Per degree
• 2x1x16 (Dual) WSS
• Flexgrid OCM
• Pre-amp and booster
Per directional switch
• 2x6x8 per 96 channels
Per 16 channel Add/Drop
• 2x1x16 splitter/couplers
• EDFA per splitter/coupler
CD ROADM
16x1 coupler
OC
M
1x16 W
SS
8x8 Span
Crossconnect
8x8 Span
Crossconnect
1x16 W
SS
To
Directions 2-8
From
Directions 2-8
Drop Port 1
16 ADD 16 DROP
6x8 WSS 8x6 WSS
Drop Ports 2-8
AMP
x6 x6
Add 1
Add Ports 2 - 8
1x16 splitter
8x6 WSS
AMP
© 2014 Finisar Corporation 13
Colourless, Directionless, Contentionless, (CDC) ROADM
Typical Requirements
Scalable to 8 degrees with ~30%
Add/Drop of 96 channel systems
Flexgrid
NB No drop-side filtering – only
works for coherent systems
Example Modularity
Per degree
• 2x1x23 (Dual) WSS
• Flexgrid OCM
• Pre-amp and booster
Per 16 channel Add/Drop
• 2x8x16 multicast switch
• Quad low-gain EDFA (2 per
multicast switch)
CDC ROADM O
CM
1x23 W
SS
8x8 Optical
Crossconnect
8x8 Optical
Crossconnect
1x23 W
SS
To
Directions 2 - 8 From
Directions 2-8
Drop Port 1
Drop Ports 2-16
16 ADD 16 DROP
AMP AMP
Add Port 1
Add Ports 2-16
8x16 MCS 8x16 MCS
© 2014 Finisar Corporation 14
8 Degree ROADM Comparison
© 2014 Finisar Corporation 15
CDC ROADM , 100% Add Drop
100% capacity on each Add/Drop
requires:
1 x 4 splitter
Higher gain amplifiers
Additional MCS on Add/Drop
CDC ROADM O
CM
1x23 W
SS
8x8 Optical
Crossconnect
8x8 Optical
Crossconnect
1x23 W
SS
Drop Port 1
Drop Ports 2-16
Add Port 1
Add Ports 2-16
1x4 splitter
From
Directions 2-8
16 DROP
8x16 MCS
From
Directions 2-8
16 DROP
8x16 MCS
From
Directions 2-8
16 DROP
8x16 MCS
AMP
© 2014 Finisar Corporation
Optical Amplifiers: Size, Power, SNR
© 2014 Finisar Corporation 17
Honey, I shrunk the EDFA…
XFP: 1.5W power
consumption
APPROXIMATE LIFETIME EXPECTATIONS*
Coil diameter
(mm) 10 12 14 18
125µm – 3%
proof tested fiber <1 year <1 year ~3.17 years >50 years
80µm – 2% proof
tested fiber <1 year 0-3.17 years >40 years >50 years
80µm – 3% proof
tested fiber >40 years >50 years >50 years >50 years
*Cost 218 Model, 4m of fibre
© 2014 Finisar Corporation 18
EDFA Arrays for ROADMs
Shared electronics – reduces cost, power, size
Uncooled pumps - lower power consumption
Dual EDFA (70x90 mm)
PreAmp and Booster in one box
8 EDFA
(183 x 150 x 18.5 mm)
© 2014 Finisar Corporation 19
Hybrid Raman-EDFA
A combination of a counter-propagating Raman pump unit and a
variable gain EDFA
Mesh networks
ULH inline amplification
Hut skipping (for high gain range units)
Overall Gain
Electronics for
AGC Control and Eye Safety
EDFA
980 Pump
Raman
14XX
pump(s)
2 or 3-Pump Hybrid Raman EDFA
© 2014 Finisar Corporation 20
Amplifier Trends
Availability of up to 130 channels (37.5 GHz-spaced Nyquist channels within larger superchannels) in the C-band drives higher amplifier output powers.
Mesh topology will drive lower NF (Hybrid Raman-EDFA) and superior dynamics (fast electronics) to allow flexibility in network re-configuration.
Raman and Hybrid Raman-EDFAs will proliferate in long haul systems.
To simplify ROADM control loops, gain uniformity <0.5 dB.
To reduce types of EDFAs used, either gain switched platforms will proliferate or pluggable EDFAs will take off - provided there is no cost penalty
© 2014 Finisar Corporation
Optical Channel Monitors:
Flexgrid, Superchannels and SDN
© 2014 Finisar Corporation 22
OCM Requirements
Spectral power information with high resolution
Intra-channel attenuation in 6.25 GHz spectral slices
Power monitoring of superchannel carriers
Location of center wavelengths of superchannel carriers
Eliminate power differential between adjacent channels
Fast scanning and response time
Superchannel Add/Drop requires OCM, not just a photodiode, to monitor traffic through
Add/Drop paths
Loss of Signal (LoS) and fault detection to support protection and restoration switching
Staring mode - monitoring a fixed frequency
Applications utilizing in-band modulation signals, i.e. wavelength tracking
• Possibly demodulate within the OCM
Some proprietary OSNR measurement techniques
© 2014 Finisar Corporation 23
Multi-port Flexgrid Optical Channel Monitor
Grating spectrally disperses light from up to four fibers.
2D MEMS mirror is used to scan the optical spectrum onto an
array of photodiodes.
© 2014 Finisar Corporation 24
Example: Multiport Flexgrid OCM
Small size: 100x50x15 mm, Low power: <5 W
Parallel scanning of all ports in 500 ms; no need for dedicated switch
Requires deconvolution of measured signal to provide 6.25 GHz slices
required for attenuation control on Flexgrid WSS
2-4 port OCM
© 2014 Finisar Corporation 25
To Summarise…
Improved ROADM subsystems
(Dual WSS, Hybrid amplifiers, Flexgrid OCM, etc) will
enable future-proof ROADM Architectures
to provide transparent Wavelength Management
Capability for future 400 Gb/sec and 1 Tb/sec