Next Generation CDC ROADM Network Solution - … Focus 2017...Next Generation CDC ROADM Network Solution Brian Smith CTO office, Lumentum

Next Generation CDC ROADM Network

Solution

Brian Smith

CTO office, Lumentum

© 2017 Lumentum Operations LLC | LUMENTUM CONFIDENTIAL AND PROPRIETARY INFORMATION

Current CDC ROADM Network Solution

Twin WSS within Node Degrees– Twin 1x9 WSS

– Twin 1x20 WSS

– Twin 1x32 WSS

Multicast Switch (MCS) for CDC– 4 to 16 degrees

– 4 to 16 add/drop ports

General CDC Characteristics– MCS high loss requires EDFA arrays

– MCS provides no spectral filtering

– Engineered for one wavelength per port

WSSWSS

Degree 2

1xN power

splitters

Mx1

selector

switches

…

EDFA arrays

…

Multicast Switch

(MCS)

TxRx


What is Required for Next Generation CDC ROADM Networks?

Improved cost per add/drop port– Leverage higher port count modules

More add/drop ports per module– 16 24 32

– Better total node capacity scalability

Support for more degrees – 8 16 16+

Channel filtering for improved

performance and relaxed transceiver

requirements– Tx_OSNR and receiver dynamic range

Support for superchannel transceivers– Transceiver which emits multiplexed

superchannels, such as 2l x 200Gb/s

WSSWSS

Degree 2

……

TxRx

CDC

Add/Drop

Module ?


WSSWSS

Degree 2

……

Rx Tx










CDC

Add/Drop

Module ?

Can we meet these requirements with MCS?



MCS: Insertion Loss and EDFA Array Power Scaling

not practical

cooled pumps

uncooled pumps

9

11

13

15

17

19

21

4 8 12 16 24 32

Inse

rtio

n lo

ss (

dB

)

Number of MCS ports

An EDFA array is required for MCS above 4-6 add/drop ports– MCS loss increases directly with the number of add/drop ports

Up to about 16 add/drop ports, EDFA arrays can leverage uncooled pumps– Beyond 16, higher complexity pumps required


MCS: Transmitter Wideband Noise Accumulation

OSNR = Tx_OSNR - 10log(N)

Tx_OSNR

WS

S

MCS

Tx Tx Tx

Tx_OSNR

0

1

2

8

5

3

Tx_OSNR = 50dB

Tx_OSNR = 45dB

Tx_OSNR = 40dB

Transceivers emit wideband optical noise (Tx_OSNR specification)

Wideband noise accumulates in filterless MCS degrading OSNR before any transmission

More MCS add/drop ports means proportionally more accumulated noise and degraded OSNR

Appro

xim

ate

Reach P

enalty

(num

ber

of spans)No Penalty

Tolerable Penalty

High Penalty1 N


MCS: Transmitter Wideband Noise Accumulation

Tx_OSNR

WS

S

Tx Tx Tx

Tx_OSNR

0

1

2

8

5

3

effective Tx_OSNR > 50dB

Tunable filter array solves noise accumulation degradation (effectively increases Tx_OSNR)

But increases cost, size and insertion loss

Tunable Filter

Array

MCS

Appro

xim

ate

Reach P

enalty

(num

ber

of spans)

OSNR = Tx_OSNR - 10log(N)

No Penalty

Tolerable Penalty

High Penalty


MCS: Impact of Unwanted Channels on Rx

Large number of wavelengths at a single coherent receiver

As port count (N) increases, dynamic range of receiver

can become inadequate resulting in signal quality

degradation

Issue significantly worse for superchannel Tx/Rx

MCS

Rx N (add/drop)

Niwa M. et al, OFC 2017, Tu3F.4


Supporting Next Generation Superchannel Transceivers

Industry evolving to superchannel transceivers with

multiplexed wavelength subcarriers – Example: 2l x 200Gb/s for 400Gb/s

– Example: 4l x 250Gb/s for 1Tb/s

Superchannel has n times more power per CDC add/drop

port– n is the number of superchannel carriers (i.e. n=2 or 4)

Currently, EDFA array power is engineered for single

channel per port – Multiple channels per add/drop port requires n-times more

output power in EDFA array

WS

S

Tx Tx Tx

n:1

Tx D

Tx C

Tx B

Tx A

n:1

Tx D

Tx C

Tx B

Tx A

n:1

Tx D

Tx C

Tx B

Tx A

WS

S

MCS


EDFA Array Power Requirements with Superchannel Transceivers

not practical

cooled pumps

uncooled pumps4 carriers

2 carriers

1 carrier

• Supporting 2- and 4-carrier superchannels with >10 port MCS requires complex EDFA array


WSSWSS

Degree 2

……

Rx Tx










CDC

Add/Drop

Module ?

Can we meet these requirements with MCS?



Contentionless M x N WSS Addresses Next Generation CDC

WSSWSS

Degree 2

Rx Tx

Contentionless

MxN WSS

Contentionless

MxN WSS

Low loss eliminates EDFA arrays– Lower cost total solution

WSS device cost and loss scales

minimally with port count– Enables higher port count and lower

cost / port

Without EDFA arrays:– No power dependency on port count

– Supports superchannel transceivers

without specification of power per port

WSS passband filters wideband noise– High performance independent of port

count

– Relaxes requirements on Tx and Rx


Low loss eliminates EDFA arrays– Lower cost total solution

WSS device cost and loss scales well

with port count– Enables higher port count and lower

cost / port

Without EDFA arrays:– No power dependency on port count

– Supports superchannel transceivers

without specification of power per port

WSS passband filters wideband noise– High performance independent of port

count

– Relaxes requirements on Tx and Rx

Contentionless M x N WSS Addresses Next Generation CDC

WSSWSS

Degree 2

Rx

Contentionless

MxN WSS

Contentionless

MxN WSS

Tx

M x WSS

Switches

select 1 of M

WSSs


Summary

• MCS is addressing today’s CDC solutions

• Next Generation CDC improvements are needed (cost, port count, performance)

• However, the MCS does not scale to support these requirements

• Contentionless MxN WSS directly supports next-generation requirements

• Advanced LCoS and optical design technology enabling Contentionless MxN WSS

Thank you!

Brian Smith

[email protected]

Link to Whitepaper:

https://www.lumentum.com/sites/default/files/technical-library-items/ngcdcroadm-wp-oc-ae.pdf

Documents

Next Generation CDC ROADM Network Solution - … Focus 2017...Next Generation CDC ROADM Network Solution Brian Smith CTO office, Lumentum