[AusNOG] Basic question about fibre visual fault locators

Fri Sep 25 19:14:22 EST 2020

You basically need three fibre specs (OM1 62.5u is one, OM2 and OM3 are both
50u, that's two, and OS1 (SMF), that's three) , one patch lead of each type
to the relevant endpoint.

When I worked on a large campus with a mix of fibre (OM1, OM3 and OS1) I
used to have a series of the most common ones in my toolbox along with
line-joiners for LC and SC. I had ST as well, but mostly used a patch lead
to adapt that to my required endpoint (usually brought everything back to SC
- this was a few years ago now. I imagine LC is more common today).

For a view of the one scenario where MMF and SMF are used together, look up
'mode conditioning', which would push the SMF signal up the outer edge of
the MMF core.  It allowed you to use SMF modules to drive higher speeds over
structural MMF where (for example) OM1 had a Gig-E distance limit of around
220m at spec? But mode conditioning would let you push that out to 500-600m,
which was great when OM1 runs spec'd originally for up to 2KM at 100Mbit
needed to be upgraded to Gig.

I got out of the campus network realm 10 years ago however....

Good luck,

Mark.

From: AusNOG <ausnog-bounces at lists.ausnog.net> On Behalf Of Rhys Hanrahan
Sent: Friday, 25 September 2020 9:04 pm
To: ausnog at lists.ausnog.net
Subject: Re: [AusNOG] Basic question about fibre visual fault locators

Hi Guys,

Thanks for the info! The problem is that the site has a wide range of MMF. A
mix of SC, FC and ST on all the patch panels. As well as a mix of OM1, OM2
and OM3/4. So given I have to buy local I was hoping to avoid having to buy
a bunch of different $15-$20 patch leads that I will only need to use once
for tracing.

On the other hand the "switch" end of the existing patch leads are all LC so
that would simplify things - but of course need a female LC to X end for
that.

The cables we are trying to trace are somewhere around 200-300m (they are
between different buildings). I was hoping that despite some light loss
between MMF and SMF, there should be enough left over for basic tracing (we
are not fault finding yet - not sure if we will need to, and in that event
we'd just hire someone). Just trying to re-use old MMF to get an NBN service
where we need it, so trying to avoid expense as much as possible.

Sounds like it might be worth it to just keep hunting for a MMF adaptor in
this case!

Rhys.

From: Mark Foster [mailto:blakjak at blakjak.net] 
Sent: Friday, 25 September 2020 6:39 PM
To: Rhys Hanrahan <rhys at nexusone.com.au <mailto:rhys at nexusone.com.au> >;
ausnog at lists.ausnog.net <mailto:ausnog at lists.ausnog.net> 
Subject: RE: [AusNOG] Basic question about fibre visual fault locators

Single Mode has a very, very narrow light-path (6u) as opposed to Multi-Mode
(50u).

They're not compatible with eachother - I've never used a VFL but I used to
work on campus fibre (MMF OM1, OM2, and OM3, and SMF SM1) routinely.

When I didn't have the connectors I needed, a short patch lead usually did
the trick.

Can you use a short patch lead that'll get you over to your required
interface?

MMF Patchleads are usually fairly readily available in various endpoint
combinations, as are SC-SC female-to-female (line joiners) and usually,
LC-LC versions of the same (which are just for plug alignment, and aren't
type-specific.)

(Colours are specified by the standards but that's all).

Mark.

From: AusNOG <ausnog-bounces at lists.ausnog.net
<mailto:ausnog-bounces at lists.ausnog.net> > On Behalf Of Rhys Hanrahan
Sent: Friday, 25 September 2020 8:26 pm
To: ausnog at lists.ausnog.net <mailto:ausnog at lists.ausnog.net> 
Subject: [AusNOG] Basic question about fibre visual fault locators

Hi Everyone!

I have a pretty basic question about VFLs. I haven't used one before but we
need to trace some existing old MMF at a site and am about to buy a cheap
VFL that has a universal connector for SC, ST, FC. We need LC as all the
patch leads convert to this.  But all the LC female to SC male connectors I
can see around are either SMF, significantly more expensive or
internationally shipped. Need to get my hands on this for next week. 

I understand that in normal circumstances that mixing MMF and SMF spec
equipment would be a no go, but would it be sufficient to use a SMF adaptor
just for the purposes of fault-finding/tracing in this case?

I was looking at an adaptor like this one, coupled with a separate cheap
VFL:
https://www.ebay.com.au/itm/SC-Male-to-LC-Female-Single-Mode-Fiber-Optic-Hyb
rid-Optical-Adaptor-Converter/353200623750

This "looks" like it is the same adaptor all the VFLs are bundling in with
the tool anyway (but they are all being shipped internationally). Is there
any reason not to settle for this? Thanks!

Rhys Hanrahan
Chief Information Officer
Nexus One Pty Ltd

E: support at nexusone.com.au <mailto:support at nexusone.com.au> 
P: +61 2 9191 0606
W: http://www.nexusone.com.au/
M: PO Box A356 Sydney South, NSW 1235
A: Level 12 227 Elizabeth St, Sydney NSW 2000

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