"Chris Cole" <chris.cole@finisar.com> writes:
One of the points made by Ted Sealy from Sprint is that they take advantage of the extra link budget in 10GBASE-LR 10km link budget to account for extra connector loss, etc.
Ted Seely and I are of the same mind on this. 2 dB sounds like plenty for connector loss right up until you have to deal with multiple patch bays in a structured system with amateurishly applied mechanical splices. The difference between noting that the loss is a little high but the link still works so you roll with it, and having to spend time on the phone arguing with someone who thinks 24 dB link loss is A-OK, will make the slight additional up front cost for the better grade optics look very inexpensive indeed...
From this discussion it sounds to me like we should stick with 10km initially, and then later come back with an additional specification optimized for low cost, perhaps covering 2km.
I'm on board with that as far as it goes, but has the scenario of adjustable launch powers so that you don't ever need attenuators plus the economy of scale that would come from having *one* type of interface for 1m-10km runs been considered? It seems to me based on what I've seen of the optics market that once you make something a mass-produced commodity the price falls awfully far - suppose the price difference was $250 vs. $375, that's a big difference on a percentage basis but pocket change on an absolute basis. ---rob
Chris
-----Original Message----- From: Robert E. Seastrom [mailto:rs@seastrom.com] Sent: Wednesday, December 12, 2007 5:06 AM To: Justin M. Streiner Cc: nanog@merit.edu; Chris Cole Subject: Re: IEEE 40GE & 100GE
"Justin M. Streiner" <streiner@cluebyfour.org> writes:
I haven't read the draft spec yet to see what's being proposed for a link budget at 3/4/10km, but that's just as important as the physical distance.
That's a really good point, and one which I didn't originally consider pre-coffee. :-)
Link budget information on page 4, here: http://www.ieee802.org/3/hssg/public/reach/Matsumoto_r1_1207.pdf Relative cost estimates on page 5.
Suppositions for ingredients to link budget are here: http://grouper.ieee.org/groups/802/3/hssg/public/nov07/cole_01_1107.pdf (page 3)
I'm kind of looking longingly at that extra 3dB, given the slight marginal extra cost and my knowledge of the trained chimp quality mechanical splices that are rife in certain <cough> data centers.
---Rob
I'm on board with that as far as it goes, but has the scenario of adjustable launch powers so that you don't ever need attenuators plus the economy of scale that would come from having *one* type of interface for 1m-10km runs been considered? It seems to me based on what I've seen of the optics market that once you make something a mass-produced commodity the price falls awfully far - suppose the price difference was $250 vs. $375, that's a big difference on a percentage basis but pocket change on an absolute basis.
I'm inclined to agree that when we are talking about unit numbers between 10km >> 40km optics, the marginal price change of a few bucks per optic (vs the human time to go and fix/groom/find/reduce optical losses) is pretty minimal. For that 1% of customers that finds their total cost significantly impacted (vs, say the cost of the equipment these are going into, etc).... would force 10% of us to have to engineer bypass cross-connect panels with fewer physical connections (and spliced ones at that) to get the job done. Just my guess... but no one has really complained about 10km reach optics being so expensive after the first 5 minutes they've been on the market. Personally, I wish this much cost could be cut out of the 80/120km optics market... but hey, no one is asking me. Deepak
Deepak Jain <deepak@ai.net> writes:
I'm on board with that as far as it goes, but has the scenario of adjustable launch powers so that you don't ever need attenuators plus the economy of scale that would come from having *one* type of interface for 1m-10km runs been considered? It seems to me based on what I've seen of the optics market that once you make something a mass-produced commodity the price falls awfully far - suppose the price difference was $250 vs. $375, that's a big difference on a percentage basis but pocket change on an absolute basis.
I'm inclined to agree that when we are talking about unit numbers between 10km >> 40km optics, the marginal price change of a few bucks per optic (vs the human time to go and fix/groom/find/reduce optical losses) is pretty minimal.
For that 1% of customers that finds their total cost significantly impacted (vs, say the cost of the equipment these are going into, etc).... would force 10% of us to have to engineer bypass cross-connect panels with fewer physical connections (and spliced ones at that) to get the job done.
Just my guess... but no one has really complained about 10km reach optics being so expensive after the first 5 minutes they've been on the market.
Personally, I wish this much cost could be cut out of the 80/120km optics market... but hey, no one is asking me.
So, the unspoken point of what I was suggesting is "why not two kinds of optics: medium to short and super-long?? Simplifies sparing. ---Rob
On Wed, 12 Dec 2007, Robert E. Seastrom wrote:
Ted Seely and I are of the same mind on this. 2 dB sounds like plenty for connector loss right up until you have to deal with multiple patch bays in a structured system with amateurishly applied mechanical splices. The difference between noting that the loss is a little high but the link still works so you roll with it, and having to spend time on the phone arguing with someone who thinks 24 dB link loss is A-OK, will make the slight additional up front cost for the better grade optics look very inexpensive indeed... This is somewhat interesting subject. The optical margins for "short-haul" optics are getting tighter. The number of crossconnects in a structural wiring system is getting larger. Given the specified SC connector insertion loss of .75dB, it is not uncommon to see loss within a facility for "working" crossconnects of 3-4dB.
Is anyone giving thought to going forward to connectors like MU/E2000 for structured wiring (which have much lower specified loss - I believe .1dB), or the installed base makes it prohibitive? -alex [not mlc anything]
On Wed, 12 Dec 2007, Alex Pilosov wrote:
wiring system is getting larger. Given the specified SC connector insertion loss of .75dB, it is not uncommon to see loss within a facility
Where does this .75 dB figure come from? Googling around seems to yield .15-.5 with a typical around .2. .75 sounds very high. -- Mikael Abrahamsson email: swmike@swm.pp.se
participants (4)
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Alex Pilosov -
Deepak Jain -
Mikael Abrahamsson -
Robert E. Seastrom