Fibre testing

dr_volki · 11 Sep 2012 at 13:08

Hi Guys

i'm currently testing a lot of old 200um fibres.

but something doesn't add up.

We have 2 big bulkhead cubicles from which we spread out to certain ares.

for these i usually use a launch fibre to get the measurement.

so the launch fibre currently reads in at -10.2dBm
the acutal fibre without the bulkhead measures at -8,5dBm
i later on changed the bulkhead because the reading was too low.

now the measurement for the full length (launch fibre - bulkhead - main fibre) is -14,8dBm.

someone told me i could just subtract the launch fibre measurment from the full measurment but this doesn't add up at all. :confused:

could someone be so nice and explain this to me?

thanks

pdw8 · 11 Sep 2012 at 14:57

What equipment are you using to generate and test the optical power?

PistolPete · 11 Sep 2012 at 16:55

Are you including any losses for splices & connectors?

dr_volki · 20 Sep 2012 at 10:17

sorry forgot that i posted here.

these fibres are not fusion spliced they are just old SMA ends connection through a straightthrough bulkhead, guess that's how they used to do it 20 years ago

equipment is just a normal light source and meter i would have thought?

but i found an answer anyway.

it seems that the light source is already "running" at around -7dB as the light source does not directly inject light into the fibre. so i found that measuring the loss of the launch fibre in dBm and the measuring the actual fibre including launch fibre in dBm.

these 2 figure can be subtracted to get the actual fibre loss in dB.

at least that's what it said on a website