[AusNOG] TX/RX Conventions

Darren Ward (darrward) darrward at cisco.com
Wed Jun 13 15:03:51 EST 2012


And I was about to look up which fibre rack/panel vendor I saw that made a patch panel that has a built in optical 1:2 and 2:1 switch per port so if you do have TX/RX around the wrong way you can tell the patch panel remotely to swap them :)

Of course then your patch panel needs power and adds extra loss :)

From: ausnog-bounces at lists.ausnog.net [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Andrew Warburton
Sent: Wednesday, 13 June 2012 3:00 PM
To: john at netniche.com.au
Cc: ausnog at ausnog.net
Subject: Re: [AusNOG] TX/RX Conventions

Hey guys,
No need to get too complicated, this is just Layer 1 ie. Physical layer, no rocket science required.

Andrew
On 13 June 2012 13:45, <john at netniche.com.au<mailto:john at netniche.com.au>> wrote:
On 13.06.2012 07:21, Tom Sykes wrote:
I'm interested to understand which conventions/standards (if any) are
being used by operators to identify the TX/RX in fibre patching
panels/trays - in environments like a meet me room or datacentre.

Hi Tom,

I'm not aware of any convention other than the "flip it if it doesn't work and curse shutdown-by-default policies".

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).

>From a purely logical point of view, TX should be on the "first" port of a group. This is because it's difficult to test for the absence of a signal, so if only 1 of two ports has a signal on it that should ideally be the first one you try.

Otherwise, you're condemning engineers everywhere to a sequence of try port 1, nope, try port 2 - that's a 30 second gain in productivity for the industry each time they plug in a patch lead :)

John

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