IPC 2013, Bellevue WA (WG1.2)
Mark Filer and Sorin Tibuleac
ADVA Optical Networking / Atlanta, GA
Performance Tradeoffs of 120 Gb/s DP-QPSK in ROADM Systems Employing Broadcast-and-Select Versus Route-and-Select Architectures
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
Introduction
• Increased capacity demands require optical transmission through spectrally-dense ROADM-enabled networks
• Increasingly challenging due to high bit-rate signals with bandwidths on the order of the channel spacing (e.g., 100G)
• Passband and isolation characteristics of WSS become critical – must be accounted for properly in system architecture and design
• ROADM architecture options:
• Broadcast-and-Select (B&S)
• Route-and-Select (R&S)
• Passband narrowing and crosstalk accumulation effects have been treated separately in prior work
• This study: performance of 120 Gb/s coherent DP-QPSK in a ROADM-enabled network considering both impairments simultaneously
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
• Broadcast-and-Select:
• passive 1xN splitter followed by single Nx1 WSS
• signals broadcast (“copied”) onto all splitter output ports
• signals selectively passed or blocked at each Nx1 WSS input port
• Route-and-Select:
• 1xN followed by Nx1 WSSs
• signals selectively routed or blocked to 1xN WSS output ports
• signals selectively passed or blocked at each Nx1 WSS input port
ROADM architectures
to other degrees
from other degrees
broadcast select WSS
drop add
to other degrees
from other degrees
route WSS select WSS
drop add
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
to other degrees
from other degrees
route WSS select WSS
drop add
• Broadcast-and-Select:
reduced optical/electronic complexity, cost, power consumption
lower passband narrowing
reduced isolation (higher crosstalk leakage)
high IL for large N
• Route-and-Select:
increased optical/electronic complexity, cost, power consumption
increased passband narrowing
superior isolation (lower crosstalk leakage)
acceptable IL for large N
ROADM architectures (2)
to other degrees
from other degrees
broadcast select WSS
drop add
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
Isolation requirements?
• Total Crosstalk:
isoWSS + 10∙log(N-1) + 10∙log(M),
e.g., isoWSS=-27dB, N=9, M=10
Total Crosstalk = (-27dB) + (9dB) + (10dB)
= -8dB
• requirements on isolation profile of stopband?
• “weighted” crosstalk approach*
Nx1 WSS
modulated optical spectrum
port isolation
xM
* Filer and Tibuleac, Optics Express, Vol. 20, pp.17620-17631 (2012)
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
AOM
6x4x
120G co-
herent Rx
de
mu
x
DSP
60-80kmNZ-DSF
120G DP-
QPSK Tx
120G DP-
QPSK xtalk
mu
x
route WSS select WSS
block fcn
2x2
AO
M
Experiment
Recirculating loop emulating system with 24 cascaded ROADM nodes
• 120 Gb/s DP-QPSK coherent XPDR
• 4x ROADM nodes with EDFA, VOA, and 1 or 2 N-degree WSSs (configurable to R&S or B&S architecture)
• 60-80km NZ-DSF*, -6dBm/ch into fiber
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
AOM
6x4x
120G co-
herent Rx
de
mu
x
DSP
60-80kmNZ-DSF
120G DP-
QPSK Tx
120G DP-
QPSK xtalk
mu
x
route WSS select WSS
block fcn
2x2
AO
M
Experiment
Recirculating loop emulating system with 24 cascaded ROADM nodes
• 120 Gb/s DP-QPSK coherent XPDR
• 4x ROADM nodes with EDFA, VOA, and 1 or 2 N-degree WSSs (configurable to R&S or B&S architecture)
• 60-80km NZ-DSF*, -6dBm/ch into fiber
• uncorrelated 120 Gb/s DP-QPSK XPDR as crosstalk source
120G DP-
QPSK Tx
Fast Polar.
Scrambler mu
x
120G DP-QPSK xtalk
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
AOM
6x4x
120G co-
herent Rx
de
mu
x
DSP
60-80kmNZ-DSF
120G DP-
QPSK Tx
120G DP-
QPSK xtalk
mu
x
route WSS select WSS
block fcn
2x2
AO
M
Experiment
Recirculating loop emulating system with 24 cascaded ROADM nodes
• 120 Gb/s DP-QPSK coherent XPDR
• 4x ROADM nodes with EDFA, VOA, and 1 or 2 N-degree WSSs (configurable to R&S or B&S architecture)
• 60-80km NZ-DSF*, -6dBm/ch into fiber
• uncorrelated 120 Gb/s DP-QPSK XPDR as crosstalk source
• optional block fcn WSS to emulate blocking function of another degree’s ‘route’ WSS for R&S case
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
CW DFB
sources
AOM
6x4x
120G co-
herent Rx
de
mu
x
DSP
60-80kmNZ-DSF
120G DP-
QPSK Tx
120G DP-
QPSK xtalk
mu
x
route WSS select WSS
block fcn
2x2
AO
M
Experiment
Recirculating loop emulating system with 24 cascaded ROADM nodes
• 120 Gb/s DP-QPSK coherent XPDR
• 4x ROADM nodes with EDFA, VOA, and 1 or 2 N-degree WSSs (configurable to R&S or B&S architecture)
• 60-80km NZ-DSF*, -6dBm/ch into fiber
• uncorrelated 120 Gb/s DP-QPSK XPDR as crosstalk source
• optional block fcn WSS to emulate blocking function of another degree’s ‘route’ WSS for R&S case
• additional unmodulated CW sources coupled in to maintain constant amplifier gain during loop transitions
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
Cascaded passband evolution
• R&S – experiences twice the number of passbands as B&S
• Reflected in 3dB-BW evolution vs # ROADMs
• BW vs # ROADMs curve shifted by factor 2x for R&S compared to B&S
Broadcast-and-Select Route-and-Select
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
4 ROADMs 8 ROADMs 12 ROADMs 16 ROADMs 20 ROADMs 24 ROADMs
• Plot of crosstalk vs # ROADMs shows great crosstalk advantage of R&S architecture
• OSNR penalties may be computed by knowing crosstalk tolerance of modulation format
Cascaded crosstalk evolution
Broadcast-and-Select Route-and-Select
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
Cascaded crosstalk evolution
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
Results
• Expected worse performance for R&S vs B&S due to additional passband narrowing
• Additional degradations due to crosstalk accumulation as predicted by weighted crosstalk analysis:
• 0.05 to 0.2 dB for B&S
• 0 dB for R&S
• Overall performance better for B&S than R&S
© 2013 ADVA Optical Networking. All rights reserved. Confidential. IPC 2013, Bellevue WA (WG1.2)
Conclusions
• Combined penalties due to passband and isolation characteristics of 9x1 WSSs were studied for 120 Gb/s DP-QPSK transmission
• Broadcast-and-Select and Route-and-Select ROADM architectures considered
• Overall system penalties are lower for B&S than for R&S configurations by up to 0.5dB
• B&S may be preferred architecture for ROADM nodes of N ≤ 9
• For N > 9, R&S architecture is desirable due to the higher insertion loss inherent to B&S
IPC 2013, Bellevue WA (WG1.2)
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