performance tradeoffs of 120 gb/s dp-qpsk in roadm systems

IPC 2013, Bellevue WA (WG1.2)

Mark Filer and Sorin Tibuleac

ADVA Optical Networking / Atlanta, GA

[email protected]

Performance Tradeoffs of 120 Gb/s DP-QPSK in ROADM Systems Employing Broadcast-and-Select Versus Route-and-Select Architectures

mailto:[email protected]

© 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


• 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


to other degrees

from other degrees


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


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)


AOM

6x4x

120G co-

herent Rx

de

mu

x

DSP

60-80kmNZ-DSF

120G DP-

QPSK Tx

120G DP-

QPSK xtalk

mu

x


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


AOM

6x4x

120G co-

herent Rx

de

mu

x

DSP

60-80kmNZ-DSF

120G DP-

QPSK Tx

120G DP-

QPSK xtalk

mu

x


block fcn

2x2

AO

M

Experiment





• uncorrelated 120 Gb/s DP-QPSK XPDR as crosstalk source

120G DP-

QPSK Tx

Fast Polar.

Scrambler mu

x

120G DP-QPSK xtalk


AOM

6x4x

120G co-

herent Rx

de

mu

x

DSP

60-80kmNZ-DSF

120G DP-

QPSK Tx

120G DP-

QPSK xtalk

mu

x


block fcn

2x2

AO

M

Experiment






• optional block fcn WSS to emulate blocking function of another degree’s ‘route’ WSS for R&S case


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


block fcn

2x2

AO

M

Experiment






• 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


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


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


Cascaded crosstalk evolution


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


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)

Thank you.

[email protected]

contact details:

mailto:[email protected]

performance tradeoffs of 120 gb/s dp-qpsk in roadm systems

Technology

gbs dp qpsk

degrees route wss

g dpqpsk xtalk

g dp qpsk xtalk mux

gbs dpqpsk xpdr

gbs coherent dpqpsk

gbs dpqpsk coherent

g dp qpsk tx fast polar