atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring MicroTest CertiFiber Test Unit Questions

Questions -

It didn't come with the 'launch cables.' From what I can tell, this is just the ST 1m patch cords for both main and remote ends. You use these to set the reference mode by coupling them together and letting the CertiFiber figure the loss of the patch cords so it can subtract that from the cable run you are testing. That makes sense.

What doesn't make sense is the official 'launch cable kit' costs more than I paid for this thing used. Won't ANY two ST<>Coupler<>ST patch cords do the trick? I mean, if it measures power and loss, then subtracts it, who cares? Don't have to be specifically 1m if I have spare 3m cords?

OK the next thing - this unit can use 850nm and 1300nm LED power (my old one just did 850nm). Just leave it at 850nm or what is the advantage of 1300nm (sorry, fiber noob).

With aqua 10-gig 50um fiber vs 62.5 I assume all the above apply as long as 50um patch cords are used.

I do love this little unit so far - especially that it uses AA batteries instead of the always failing nicad batteries of my Pentascanner Cat5e unit.

Seeing as this a fiber question.........don't!

Launch cables stablize the readings....if there isn't enough fiber the system cannot calibrate and measure. Too short is bad.

Don't intermix fiber sizes.

The speeds (850-1300) give an overall performance rating, not just one performance rating.

I agree with what Ken said.

As far as I know Launch cables aren't just 1M long, they are long cords coiled inside a case that would give a "known" loss to the channel. This is evident in a graph when using a OTDR.

When using light loss meters I believe all that is required are mandrels which you wrap a standard patch cord around. Please correct me if I am wrong.

Here is a link to a picture of a mandrel:

https://www.tequipment.net/FlukeNetworksNF-MANDREL-50.html

What Ken said.

When you test fiber you need a long distance to get accurate readings. You can see this well on an OTDR - anything too close to you can't be 'seen'. The light just blows by any problems.

To get truly accurate readings we would test from both sides and compare/average the readings.

As I recall (and it's been a while) we used to use 1 Kilometer launch cords (1,000 meters of fiber wrapped up in a box) - hence the cost.

Multimode fiber was tested at 850nm or 1300nm. I believe this was for 62.5 (850)& 50 (1300) micron fiber. Singlemode was tested at 1310 & 1550nm. When I got out of it they were looking at testing fiber at higher speeds (1600? 1700?) Faster speeds = more bandwidth.

Sam

Here is a quick quote I found to get you started

"The minimum length for a launch cable depends on the pulse width of the OTDR being used. A good rule of thumb is that a 10 nanosecond pulsewidth equals a 1 meter dead zone. The launch cable must be slightly longer than the dead zone in order to view the first connector in your cable run. The connection between the fiber under test and the launch cable is commonly referred to as an "event dead zone" or an "attenuation dead zone". These secondary events create a much shorter blind spot (<1m typically) as compared to the initial dead zone of 5-10 meters or more."

Don't bother buying the Launch Cables you mentioned, just make your own.
What I use to carry with that rig you have now was 2 sets of MM launch cables 100m each section, one set ST/ST another ST/SC, that would cover the major tests I was doing.
Not advised to MIX sizes ie 62.5 to 50 as there is a "numerical aperture: value that needs to considered.


More on the subject of launch cables can be found here:
https://www.jimhayes.com/OTDR/otdrs_c.htm

Here is a link on 850 vs 1300nm, BTW the 2 are wavelengths and not speed:
https://www.ecmag.com/?fa=article&articleID=4886

I found the manual. It specifically shows the launch cable length as just one meter to a ST/ST coupler, then from the coupler one more meter to the remote.

I know that sounds very short, but that is what it says - maybe it is different that an OTDR?

Will check out those links. Thanks.

FiberTech -

You're right - the 850/1300/1310/1550 are wavelengths. It was my impression (probably wrong) that successful testing at a higher wavelength proved capacity for higher speeds.

Sam

I've done very little work on MM, but a lot (years ago) on big SM Networks. We did some testing with power meters (short runs mostly) but most of the work was OTDRs. We always used long launch cords.

Sam

Here's the CertiFiber user guide page on the launch cable. I agree that I probably should use something longer for more accurancy.

My experience was a short launch cable for light meters and a long one for OTDR testing, better results when trouble shooting...