I need to check some fibers. At the moment, I am using a VERY cheap, chinese fiber light-source and power-meter.
The combination is drifting VERY fast.
Now, I want to have a solution, that can do repeatable measurements.
What is your use case for this? If it is cable runs within a datacenter, any reading above ambient is likely to be fine - plug it in and see what the real transceivers report (assuming they support DOM and the rest of the hardware / software does as well). I've found the optical monitoring (Cisco switches, 3rd-party optics) to be pretty consistent:
(Before anyone jumps on me and says "that's a horribly low light level", the other end is 120,000+ feet away and this is going through a set of passive DWDM muxes.)
If you're going between floors in a building, a light source / meter and a pair of walkie-talkies or cell phones is probably a good idea, but you don't need hyper accuracy, just "is it working". I see lots of Fotec test sets on eBay for < $100. Just make sure you can get one that matches your fiber type and wavelength(s) of interest.
If you're talking about dark fiber between 2 buildings (or cities, or states), this is really the provider's problem. You should receive a comprehensive OTDR plot for each strand of fiber (ideally, one plot from each end) as part of turn-up. If it degrades, that's what optical monitoring is for. The provider will likely need to go to at least one end and shoot it again to find the break, unless they already know.
If you're running your own DWDM systems over dark fiber as I am, you need really esoteric test equipment to get readings non-intrusively. The composite port often has a 3% or similar small fraction optical monitoring jack, or if you want to check on a not-in-use wave, you can plug into that port. The test sets to look at the low levels and scattered narrow wavelengths are really expensive, and you might as well just buy a 40-channel (or whatever) analyzer that can look at all of the levels individually. If you want to test individual idle waves, just get a pair of tunable optics and tune them to the channel you're interested in and plug them into a switch at each end and look at the DOM - that is a
lot less expensive than buying a tunable tester. Companies that sell the tunable optics (I use
Solid Optics) usually have other useful goodies - the box that re-codes their optics also comes with an optical power meter (but not a source).
