[AusNOG] Basic question about fibre visual fault locators

Rhys Hanrahan rhys at nexusone.com.au
Fri Sep 25 21:05:26 EST 2020

Hi Jonathan,

Thanks, this kind of feedback is really useful – I was hoping I could get away with it. I grabbed a cheap 10 mW VFL, so I think regardless of any mismatches I might be OK!

For what it’s worth though (and for anyone else), I ended up finding that buying a female LC to LC MMF coupler, along with a standard LC to SC patch cable is much cheaper and easier to find than trying to get an LC to SC adapter. So that’s what I went with, so all my bases are covered.

Thanks all! Have a good weekend.


From: Jonathan Brewer [mailto:jon.brewer at gmail.com]
Sent: Friday, 25 September 2020 7:51 PM
To: Rhys Hanrahan <rhys at nexusone.com.au>
Cc: ausnog at lists.ausnog.net
Subject: Re: [AusNOG] Basic question about fibre visual fault locators

In my experience using visual fault locators to trace MMF, you won't need mode conditioning patch cables at these short distances. You will get enough light through to find your fibre at 300m even using mismatched adaptors and patch leads.

Take care with these lasers, you can get really powerful (read dangerous) ones off Uncle Ali.


On Fri, 25 Sep 2020 at 17:04, Rhys Hanrahan <rhys at nexusone.com.au<mailto:rhys at nexusone.com.au>> wrote:
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!


From: Mark Foster [mailto:blakjak at blakjak.net<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).


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-Hybrid-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
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