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From my ancient memories and experience with parallel-fiber eyesafety issues, there should be finite, but very little difference, in the power/ch between 12ch and 16ch. Slide 4 of the referenced presentation shows little variation in the Class 1M power/lane over the 3-12 lane range, suggesting very little difference with 16 lanes. Needs an update of course! Jack From: "Anslow, Peter" <panslow@xxxxxxxxx> Reply-To: "Anslow, Peter" <panslow@xxxxxxxxx> Date: Monday, August 18, 2014 at 9:45 AM To: <STDS-802-3-400G@xxxxxxxxxxxxxxxxx> Subject: Re: [STDS-802-3-400G] [802.3_400G] IEEE P802.3bs 400 Gb/s Ethernet MMF Ad Hoc - August 8th unapproved minutes Steve, This is an issue. See: http://grouper.ieee.org/groups/802/3/ba/public/mar08/petrilla_02_0308.pdf for a discussion of a ten lane version of the problem. Since then, new versions of the relevant standards IEC 60825-1 and IEC 60825-2 have been issued by IEC. Regards, Pete Anslow | Senior Standards Advisor From: Trowbridge, Stephen J (Steve) [mailto:steve.trowbridge@xxxxxxxxxxxxxxxxxx] Hi Mike, This tends to be more of an issue in WDM systems where the power is all in one fiber. Since this is ribbon fiber, I suspect it needs to be investigated what the cross-sectional area is of the ribbon fiber and what the chance is that more than x of 16 lanes would be incident on someone’s eye in the event of cutting the cable or pulling the connector. I think the connector distributes the lanes widely enough it isn’t a problem. I suppose if someone saw this as an application for multicore fiber this might be more of an issue. Regards, Steve From: Mike Dudek [mailto:mike.dudek@xxxxxxxxxx] One key aspect of whether a 16x25G solution can heavily leverage 100GBASE-SR4 is whether the output power per lane would have to be reduced significantly due to eye safety concerns. I would encourage the experts to address this. (I don’t think it has been yet.) Mike Dudek QLogic Corporation Director Signal Integrity 26650 Aliso Viejo Parkway Aliso Viejo CA 92656 949 389 6269 - office. From: Jonathan King [mailto:jonathan.king@xxxxxxxxxxx] Dear all Unapproved minutes for the 400G MMF ad hoc are available on the MMF ad hoc public area. Here’s a link: http://www.ieee802.org/3/bs/public/adhoc/mmf/index.shtml Please let me have any comments or corrections as soon as you are able – thank you! As announced at the last MMF 400G ad hoc call, the next ad hoc will be hosted on August 22nd, 8am to 10am Pacific. Best wishes jonathan |