Mixing 62.5/125 µm with 50/125 µm multimode fiber - OptiFiber

With users moving to laser optimized 50/125 µm multimode fiber, we are seeing an increasing issue with links failing due to fiber mismatches. This is where 62.5/125 µm multimode fiber is being mixed with 50/125 µm multimode fiber. When this happens, the light in the 62.5/125 µm multimode fiber is allowed to escape into the cladding of the 50/125 µm multimode fiber. This can cause a coupling loss of up to 4 dB. 

If you were to make a measurement with an OptiFiber using a 62.5/125 µm multimode fiber launch and receive lead whilst testing an installed 50/125 µm multimode fiber installation, you would see something like this: 

If you were to test a 62.5/125 µm multimode fiber installation with a 50/125 µm multimode fiber launch and receive fiber, you would see a gainer first followed by a significant loss event - a reverse of what is shown above.