[AusNOG] Bidi usage in DC

[John Edwards]

BX Optics are great for a big rollout because it minimises Splicing costs
and improves installation efficiency - there's only one way the fibre can
be patched and plugged in, so the easily-compromised fibre components are
handled by dirty contractor hands that forgot to bring a fibre-cleaning
tool only once. In one case we had sparkies in a cherry picker connecting
fibre to hundreds of nodes, so if they couldn't get it right the first time
it might mean significant delays while they returned to ground and called
someone.

If you're going to go big on BiDi optics, establish a policy early on about
which end uses the low-frequency transmit (TX) wavelength, which has better
propagation characteristics. Intuition might suggest the more reliable band
goes at the datacentre, but operationally you want remote devices to have
the more reliable TX as this allows you to differentiate between a marginal
fibre path and a power failure when something fails - which will inform if
you're sending a guy out to flip a breaker, or if it's an OTDR job for a
fibre specialist.

John


On Tue, 8 Apr 2025 at 18:03, Tony Wicks <tony at wicks.co.nz> wrote:

> In NZ we use bidi extensively as we are very used to being able to buy
> pretty cheap DF around the place. In Datacentres owned by non local
> companies I find they are often confused by it (go figure) so its all too
> hard. Personally, I would always chose bidi if possible, not just for the
> conservation of ties but also for the fact they work or not instead of the
> possibility of a one way disconnect. 100G bidi is still more expensive in
> the optics and less standard, but 10’s are much the same cost as duplex
> LR’s.
>
>
>
>
>
>
>
> *From:* AusNOG <ausnog-bounces at lists.ausnog.net> *On Behalf Of *Mitch
> Kelly
> *Sent:* Tuesday, 8 April 2025 6:57 pm
> *To:* Alex Samad <alex at samad.com.au>
> *Cc:* Ausnog <ausnog at lists.ausnog.net>
> *Subject:* Re: [AusNOG] Bidi usage in DC
>
>
>
> We use about 70% of Duplex SFP's these days.
>
> Ive checked and we have a total of 482 BiDi optics. (Half of those
> terminate in the DC's)
>
>
>
>
>
> On Tue, Apr 8, 2025 at 2:40 PM Alex Samad <alex at samad.com.au> wrote:
>
> Hi
>
>
>
> Wondering whats the percent usage of Bidi (single core SFP / TX RX on same
> fibre).
>
>
>
> Just a curiosity. Try to persuade some people to use Bidi over normal
> SFP's in the DC.
>
>
>
>
>
> Alex
>
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