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richard_s
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40G direct attach cable

Thu Mar 02, 2023 1:24 am

I would like to see a 40G direct attach cable to 4 x 10G SFP+ connectors. That I could plug a 40G fiber into and split it between boxes using SFP+. Eliminating a switch or router to do it. Obviously the 40G splitter would nee power but it would be a cheaper way to split 40G to 4 x 10G.
 
savage
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Re: 40G direct attach cable

Thu Mar 02, 2023 1:39 pm

Uhm. Have you tried google?

They exist, and is commonly used.
 
richard_s
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Re: 40G direct attach cable

Thu Mar 02, 2023 2:15 pm

savage I know that cables exist. What I meant is a box that I can plug A fiber into running at 40G and it has a DAC cable from it so I can connect it to 4 x 10G ports
 
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Re: 40G direct attach cable

Thu Mar 02, 2023 3:18 pm

savage I know that cables exist. What I meant is a box that I can plug A fiber into running at 40G and it has a DAC cable from it so I can connect it to 4 x 10G ports
Any 40G QSFP interface on the one side, any 10G Interface on the other side?

The CRS326-24S+2Q+RM for example as 2 x QSFP ports. So each of those QSFP ports, can be configured as 4 x 10G interfaces, and you connect them to 4 x SFP+ ports
 
richard_s
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Re: 40G direct attach cable

Thu Mar 02, 2023 3:29 pm

savage that means another router big expense to breakout a fiber. All I need is a converter like a fiber to copper ethernet unit.
 
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chechito
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Re: 40G direct attach cable

Thu Mar 02, 2023 5:36 pm

what you are requesting is some sort of passive or semmi passive splitter from 40g to 10g

even though internally 40g works like a 4 x 10g connection is not a trivial task to split that

i dont think you can do that without all the logic included on a switch

is not that simple

breakout cable relies on switch to work
 
richard_s
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Re: 40G direct attach cable

Thu Mar 02, 2023 5:50 pm

chechito thanks for that info. What I am looking at is to run 40G fiber then split it between 2 x CRS328-4C-20S-4S+RM switches 20G to each. The site I am looking at is remote with no electric supply (cost of installing it is way to much) so it will be solar powered it is the best location to feed customers in all directions. I thought a converter would be a cheaper option and use less power than a costly switch.
 
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mkx
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Re: 40G direct attach cable

Thu Mar 02, 2023 8:15 pm

So you do have dark fiber between the sites? There's a passive 80Gbps to 8x 10Gbps splitter solution and it's called CWDM. Mikrotik offers some CWDM gear. You have to use CWDM SFP+ modules (instead of normal 1310nm SMF modules), a passive MUX which joins/separates different wavelengths at each end of link. There are 10Gbps SFP modules for CWDM (Mikrtotik offers 1Gbps modules with model names S-CxxDLC40D, other vendors, like FS.com support 10Gbps CWDM modules). So for your particular use case, you would need 4 pairs of CWDM modules (each pair using distinct wavelength) for 4x 10Gbps links and a pair of MUXes (one for each end).

Yes, SFP modules are a bit pricier than normal 1310nm modules, but if use case demands it, it's possible (and feasible).
 
richard_s
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Re: 40G direct attach cable

Thu Mar 02, 2023 9:59 pm

Thanks for that mkx. Been chatting with a friend and come to the conclusion it would be better to put in 12 core fiber which gives me the opportunity to extend the network further with the spare cores in the future. Also if 1 SFP+ fails I still have 1 usable to the switch. I was hoping that there was a piece of kit out there to do it cheaply and not use much power.

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