On Wed, Jun 13, 2012 at 1:45 PM, <span dir="ltr"><<a href="mailto:john@netniche.com.au" target="_blank">john@netniche.com.au</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
I'm not aware of any convention other than the "flip it if it doesn't work and curse shutdown-by-default policies".<br>
<br>
Cisco appear to place TX on the "left" of the optics (first port). The LC connector specification chickens out from making a distinction, and the SFP/SFP+ specifications also don't make a commitment (they allow for copper and single-fibre, after all).<br>
</blockquote><div><br>There is a standard here and every transceiver/optics vendor follows it. Its not explicitly spelt out but if you really wanted to know, take a look in SFF-8431 table 3 or figure 1 and you have the electrical contacts used on SFP/SFP+ and where TX and RX are physically.<br>
The practicalities is that no optics vendor is going to 'crossover' the optical side of rx and tx relative to where the electrical connections are and put a more expensive PCB with more layers inside to do so.<br>
<br>SFP/SFP+ transceivers are _meant_ to have an arrows embossed on the metal jacket/sleeve showing the transmit/receive directions. (i say meant to because not all do, but I took a photo of one that does, see <a href="https://arista.box.com/s/720c5c52227da1199658">https://arista.box.com/s/720c5c52227da1199658</a> and you can see the arrows)<br>
</div></div><br><div class="gmail_quote">On Wed, Jun 13, 2012 at 3:06 PM, Tom Sykes <span dir="ltr"><<a href="mailto:TomSykes@nbnco.com.au" target="_blank">TomSykes@nbnco.com.au</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
When you've got access to both pieces of equipment and you check status
lights then I agree - "swapping" the fibres until it works is probably
acceptable. But when the fibre technician doesn't have access to the
equipment (for example: it's 10km away in some other place with a number
of patches in the middle), it helps to agree on a convention.<br></blockquote><div><br>You guys are probably dealing with lowest-common-denominator in 'fibre techs' here - BUT - the chances are that said techs do have appropriate technology for detecting what pair of a fiber has light and someone posted it already. Its fair to say that just about everyone would have a smartphone with a camera on it, and said camera's sensor will happily show you light at 850nm or 1310nm.<br>
<br>may be harder for you to write such a thing into a spec, but this is one nice thing about camera cmos sensors and no filter blocking said parts of the spectrum.<br><br><br>cheers,<br><br>lincoln.<br><br clear="all">
<span><font color="#888888"><br><span><font color="#888888">Lincoln Dale | Principal Engineer, Arista Networks Inc. | <a href="mailto:ltd@aristanetworks.com" target="_blank">ltd@aristanetworks.com</a><br>au did: </font></span></font></span><span><font color="#888888"><span><font color="#888888"><a value="+14085475782">+61 3 9999 7442</a></font></span></font></span><span><font color="#888888"><span><font color="#888888"> | m: </font></span></font></span><span><font color="#888888"><span><font color="#888888"><a value="+61417457965">+61 417 457 <span>965</span></a></font></span></font></span><span><font color="#888888"><span><font color="#888888"> | us did: <a value="+14085475782">+1 408 547 5782</a> <a value="+61417457965"><span></span></a>
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