40G reforming

Marian Ďurkovič md at bts.sk
Mon Feb 5 19:32:42 UTC 2018

Many switches based on BCM Trident ASIC allow you to configure 4 consecutive
SFP+ ports as 40G link (not LACP, but using real hardware 40G framing).
In such case, you can plug 4 DWDM SFP+ modules directly into the switch, without
the need for any reformer.


On Mon, 5 Feb 2018 20:03:33 +0100, Baldur Norddahl wrote
> I may need to clarify that I do not want to break the port into 4x10G 
> as such. To the switch this will be an ordinary 40G link to another 
> switch far away.
> I want to take advantage of the fact that 40G is transported as four
> individual streams. Each of the four streams are to be converted from 850
> nm to a 1550 DWDM channel (one channel per stream). And the reverse at 
> the other end of the link.
> The point of doing this is that 40G DWDM modules are not generally
> available and neither are 80 km modules.
> I need a true 40G channel so 4x10G LACP is not an option here. For the 
> same reason I am unable to accept a solution that splits the 40G port 
> into 4x10G and then perhaps recombines using LACP. Instead I am 
> looking at an optical solution that is invisible to the switch hardware.
> The only doubt I have about the proposed solution is whether the frame
> format of the 10G substreams is somehow incompatible with what goes on 
> in the reformer. As I understand these reformers they are little more 
> than two SFP(+) modules connected back to back. And therefore it 
> should not matter that the frame format may be different.
> Regards
> Baldur
> Den 5. feb. 2018 7.20 PM skrev "Paul Zugnoni" <pz at wish.com>:
> Whether a 40G port can be broken into 4x10G is dependent on the
> router/switch hardware and the optic you use. Good news is that most 
> 40G ports are capable of being broken out into 4x10G, since a 40G port 
> is usually operating as 4x10G internally anyway to the ASIC. The QSFP you'll
> need would be a 40G-SR4 for MTP/Multimode or 40G-LR4 for 
> MTP/Singlemode (or a lower power, less expensive equivalent). This is 
> a pretty common use of 40G ports. All 4 10G ports would then be at 
> 850nm or 1310nm, which you can then plug into any 10G SR or LR ports.
> What router or switch platform is driving the 40G?
> Paul Z
> On Mon, Feb 5, 2018 at 7:57 AM, Baldur Norddahl <baldur.norddahl at gmail.com>
> wrote:
> > Hello
> >
> > Is it possible to reform a 40G signal as individual 10G links?
> >
> > The idea is to use a 40G QSFP multimode MTP module such as
> > https://www.fs.com/products/44058.html. Then connect it using a MTP
> > breakout cable such as https://www.fs.com/products/68049.html to get four
> > dual fiber connectors. These are then connected to four 10G SFP+ multimode
> > modules such as https://www.fs.com/products/11589.html. The reformer
> > could be https://www.fs.com/products/43721.html. And finally the reformed
> > signal can be transported using anything including DWDM modules such as
> > https://www.fs.com/products/44058.html.
> >
> > Just using fs.com as a reference to the kind of equipment I am talking
> > about. Many other vendors offer simelar products.
> >
> > The motivation for doing this is to get access to the many options that
> > are available for 10G optics but not possible with 40G.
> >
> > Regards,
> >
> > Baldur
> >
> >

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