Talk:25 Gigabit Ethernet

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25GBASE-ER does support 40 km operating range[edit]

Please read IEEE Std 802.3cc-2017 on page 30. It is clearly indicated that 25GBASE-ER support 2 m to 30 km and 2 m to 40 km operating range. The standard states: "Links longer than 30 km for the same link power budget are considered engineered links. Attenuation for such links needs to be less than the worst case specified for IEC 60793-2-50 type B1.1, type B1.3, or type B6_a single-mode fiber."

Moreover, in page 15 the definition of 25GBASE-ER is: "IEEE 802.3 Physical Layer specification for 25 Gb/s using 25GBASE-R encoding over single-mode fiber, with reach up to at least 40 km. (See IEEE Std 802.3, Clause 114.)".

Therefore, one shouldn't simply delete or ignore this 40 km information.

--NetsFangfang (talk) 09:09, 24 August 2018 (UTC)[reply]

We know that. The question is whether "30 or 40 km" is good information for the reader. It isn't. Most SMF PHYs have longer reach over engineered links or better cable grade/lower attenuation. The quote "with reach up to at least 40 km" in IEEE jargon means "with reach up to 40 km", the "at least" is general verbiage used with reach and "up to" means the ultimate (=engineered) reach unless you've got some vastly superior channel. The current "30 km or 40 km using engineered link" is OK with me, but maybe we need to explain to the reader what an engineered link is. --Zac67 (talk) 10:42, 24 August 2018 (UTC)[reply]