Next Generation CDC ROADM Network Solution Brian Smith CTO office, Lumentum
Current CDC ROADM Network Solution Degree 2 Twin within Node Degrees Twin 1x9 Twin 1x20 Twin 1x32 EDFA arrays Multicast Switch (MCS) for CDC 4 to 16 degrees 4 to 16 add/drop ports 1xN power splitters Mx1 selector switches General CDC Characteristics MCS high loss requires EDFA arrays MCS provides no spectral filtering Engineered for one wavelength per port Rx Tx Multicast Switch (MCS)
What is Required for Next Generation CDC ROADM Networks? Degree 2 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+ CDC Add/Drop Module? Channel filtering for improved performance and relaxed transceiver requirements Tx_OSNR and receiver dynamic range Rx Tx Support for superchannel transceivers Transceiver which emits multiplexed superchannels, such as 2l x 200Gb/s
What is Required for Next Generation CDC ROADM Networks? Degree 2 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+ Rx CDC Add/Drop Module? Can we meet these requirements with MCS? Tx 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
Insertion loss (db) MCS: Insertion Loss and EDFA Array Power Scaling 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 21 19 17 cooled pumps not practical 15 13 11 uncooled pumps 9 4 8 12 16 24 32 Number of MCS ports
Approximate Reach Penalty (number of spans) MCS: Transmitter Wideband Noise Accumulation OSNR = Tx_OSNR - 10log(N) Tx_OSNR = 50dB Tx_OSNR = 45dB Tx_OSNR = 40dB No Penalty 0 1 N Tx Tx Tx MCS Tolerable Penalty High Penalty 1 2 3 5 8 Tx_OSNR Tx_OSNR 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
Approximate Reach Penalty (number of spans) MCS: Transmitter Wideband Noise Accumulation OSNR = Tx_OSNR - 10log(N) No Penalty effective Tx_OSNR > 50dB 0 Tunable Filter Array Tx Tx Tx MCS Tolerable Penalty High Penalty 1 2 3 5 8 Tx_OSNR Tx_OSNR Tunable filter array solves noise accumulation degradation (effectively increases Tx_OSNR) But increases cost, size and insertion loss
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) MCS 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 Tx A n:1 Tx B Tx Tx Tx n:1 Tx B Tx D Tx A Tx C Tx D Tx B Tx C Tx A n:1 Tx C Tx D
EDFA Array Power Requirements with Superchannel Transceivers not practical cooled pumps uncooled pumps 4 carriers 2 carriers 1 carrier Supporting 2- and 4-carrier superchannels with >10 port MCS requires complex EDFA array
What is Required for Next Generation CDC ROADM Networks? Degree 2 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+ Rx CDC Add/Drop Module? Can we meet these requirements with MCS? Tx 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
Contentionless M x N Addresses Next Generation CDC Degree 2 Low loss eliminates EDFA arrays Lower cost total solution device cost and loss scales minimally with port count Enables higher port count and lower cost / port Rx Contentionless MxN Tx Contentionless MxN Without EDFA arrays: No power dependency on port count Supports superchannel transceivers without specification of power per port passband filters wideband noise High performance independent of port count Relaxes requirements on Tx and Rx
Contentionless M x N Addresses Next Generation CDC Degree 2 Low loss eliminates EDFA arrays Lower cost total solution device cost and loss scales well M x with port count Enables higher port count and lower cost / port Rx Contentionless MxN Tx Contentionless MxN Without EDFA arrays: No power dependency on port count Supports superchannel transceivers without specification Switches of power per port select 1 of M s passband filters wideband noise High performance independent of port count Relaxes requirements on Tx and Rx
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 directly supports next-generation requirements Advanced LCoS and optical design technology enabling Contentionless MxN
Thank you! Brian Smith brian.smith2@lumentum.com Link to Whitepaper: https://www.lumentum.com/sites/default/files/technical-library-items/ngcdcroadm-wp-oc-ae.pdf