Re: [802.3_25GSMF] [802.3-25GSMF] "PMD" versus "PHY"
David,
I should probably add that my statement was just based on the observation that, at the BER reference used in 802.3by for 25GBASE-SR (the MMF specification in Clause 112.1.1 on 802.3by), the experimental data for 40km showed sufficient margin, suggesting that the same reference BER could be used. Assuming Clause 112.1.1 is valid and by applying it to 40km, then the same FEC (per Clause 108) assumed in Clause 112.1.1 should give acceptable performance. For reference, Clause 112.1.1 is as below.
Regards,
Kohichi
112.1.1 Bit error ratio
The bit error ratio (BER) shall be less than 5 × 10-5 provided that the error statistics are sufficiently random
that this results in a frame loss ratio (see 1.4.223) of less than 6.2 × 10-10 for 64-octet frames with minimum
interpacket gap when processed according to Clause 108.
If the error statistics are not sufficiently random to meet this requirement, then the BER shall be less than
that required to give a frame loss ratio of less than 6.2 × 10-10 for 64-octet frames with minimum interpacket
gap when processed according to Clause 108.
From: David Lewis [mailto:David.Lewis@xxxxxxxxxxxx]
Sent: Saturday, January 16, 2016 10:38 AM
To: 802. 3 25GSMF
Cc: petejone@xxxxxxxxx; 田村公一 Kohichi Tamura; 'Anslow, Peter'; Law, David; 'Piers Dawe'; 'John DAmbrosia'
Subject: [802.3-25GSMF] "PMD" versus "PHY"
Colleagues,
There has been some discussion via email about the pros and cons of stating our objectives as either:
Provide PMD specification which support 25 Gb/s operation over at least 10 km on SMF.
Provide PMD specification which support 25 Gb/s operation over at least 40 km on SMF.
Or alternatively:
Provide Physical Layer specifications which support 25 Gb/s operation over at least 10 km of SMF.
Provide Physical Layer specifications which support 25 Gb/s operation over at least 40 km of SMF.
In order to ensure we have consensus before submitting the PAR, I would like to request a presentation or presentations arguing the case for one versus the other.
I have received a statement from Kohichi Tamura that for 40 km he does not see a need for a different FEC than the one already included in 802.3by. Therefore the argument in favor of saying “Physical Layer” is that we will need to include changes to non-PMD clauses in order to implement any new PMDs.
Please let me know ASAP if someone is willing to make a presentation on this subject and I will add it to the agenda for Monday.
Regards,
David Lewis
Acting SG Chair