400GBASE-SR8 MDI Choices
Paul Kolesar, CommScope
IEEE P802.3cm
May 2018
Purpose and Approach
• Purpose
– To present choices for SR8 MDI lane assignments
to allow informed selection
• Approach
–
–
–
–
Review structured cabling connectivity
Present three types of MDI assignments
Examine pros and cons
Foster discussion
2
Structured Cabling Connectivity
• ANSI/TIA-568.3-D (2016)
– Defines structured cabling polarity methods and
components for duplex and parallel channels
– Illustrates
• duplex, multi-duplex array, 1-row array, 2-row array
– Allows
• other than 12-wide array cabling, e.g. 16-wide
3
How Array Polarity Works
• TIA-568 describes three methods: A, B, C. ISO & CENELEC one.
– All produce the same signal routing with different sets of components
– Key application examples:
cabling
TxTx TxTx
For 1-row applications, methods deliver
lateral signal transposition (Tx to Rx)
RxRxRxRx
Supports 40G/100G/200G-SR4
200G/400G-DR4, 100G-SR2
cabling
RxRxRxRxRxRxRxRxRxRx
TxTx TxTxTx TxTxTx TxTx
For 2-row applications, methods deliver
lateral and row transposition (Tx to Rx)
Supports 100G-SR10,
400G-SR16
These signal routing conventions support all standard parallel applications
including INCITS T11 10GFC 1200-Mx-SN4P-I and HIPPI-6400
4
Some MDI Lane Assignment Choices
without lane numbers
1) Tx row + Rx row, 24f MPO
RxRxRxRxRxRxRxRx
Tx TxTxTx TxTxTx Tx
Tx TxTxTx TxTxTx Tx
RxRxRxRxRxRxRxRx
Rx over Tx
like SR10 opt. A
Tx over Rx
like SR16
2) Single row MPO-16
TxTxTxTxTxTxTxTxRxRxRxRxRxRxRxRx
Tx then Rx
like QSFP-DD
3) “Dual DR4” 24f MPO
TxTxTxTx
RxRxRxRx
TxTxTxTx
RxRxRxRx
Tx, blank, Rx
like QSFP-DD
5
Pros n Cons of 1), 2), 3)
1) Tx row + Rx row
• Pros
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–
–
–
•
2) Single-row MPO16
• Pros
–
Familiar from SR10, 16
CXP and CDFP MSAs
Compatible w standard
cabling if without lane
numbers of MSAs
Monolithic source and
detector w low
interference
–
–
–
–
Cons
–
–
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SR10, SR16 not
popular
Cabling polarity more
complex w two rows
More difficult connector
termination
•
Compatible w standard
cabling polarity
Easier connector
termination
Monolithic source and
detector
In QSFP-DD MSA
Proposed by Google at
outset
Cons
–
–
–
New MDI construct
MPO16 small base
More difficult
interference mitigation
between Tx and Rx
3) “Dual DR4” 24f MPO
• Pros
–
–
–
•
In QSFP-DD MSA
Compatible w standard
cabling polarity if
without lane numbers of
MSA
Dual engine construct
good for DR4 SiP
Cons
–
–
–
–
–
New MDI construct
24f MPO small base
Cabling polarity more
complex w two rows
More difficult connector
termination
Dual Tx and Rx
suboptimal for MM
which has traditionally
used choice 1)
6
Thank You.
Questions?
7
Backup Slides
8
If used, what example lane numbers work
with structured cabling?
1) Tx row + Rx row, 24f MPO
Rx
1 2 3 4 5 6 7 8
Tx
8 7 6 5 4 3 2 1
Tx
8 7 6 5 4 3 2 1
Rx
1 2 3 4 5 6 7 8
Rx over Tx
like SR10 opt. A
2) Single row MPO-16
Tx1 2 3 4 5 6 7 8 8 7 6 5 4 3 2 1Rx
Tx then Rx
like QSFP-DD
Tx over Rx
like SR16
3) “Dual DR4” 24f MPO
Tx 1 2 3 4
8 3 6 5 Rx
Tx 5 6 7 8
4 3 2 1 Rx
Tx, blank, Rx
like QSFP-DD
9
What’s the lane number issue with 3) ?
Key-up to Key-up
Mated Connections
Transceiver
B
PUS H
PULL
Position 1
PULL
PULL
Position 1
Position 12
Position 12
Position 1
P US H
B
Position 1
P ULL
PULL
Top Row : Position 12
Bottom Row : Position 24
PUS H
Tx
Tx
:
:
Tx
Tx
PUS H
Rx
Rx
:
:
Rx
Rx
Position 12
Top Row : Position 1
Bottom Row : Position 13
P US H
Top Bot
Row Row
Position 12
One of the equipment cords must be plugged into
12f trunks with legs swappedType-B:2-1
from that illustrated to
Array Patch Cords
remove row transposition in order to support
applications with the QSFP-DD lane numbers.
Type-B:1-1
Array Cables
Transceiver
Top Bot
Row Row
Position 1
Position 12
P USH
P ULL
P US H
P ULL
PULL
B
Position 1
Position 12
P US H
Position 1
Position 1
B
P ULL
P ULL
Top Row : Position 12
Bottom Row : Position 24
P US H
Tx
Tx
:
:
Tx
Tx
PUSH
Rx
Rx
:
:
Rx
Rx
Position 12
Top Row : Position 1
Bottom Row : Position 13
Position 12
Key-up to Key-up
Mated Connections
Example Optical Path
Connectivity Method B Supporting Parallel Signals
for 1-plug x 2-row Applications over 12f MPO trunks
10