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Tup01
@sky.com

Tup01

Anon

[Info] OTDR Y-Coupler

I'm trying to understand an application requirement I currently have maybe someone can help shed some light on this. I have 100ft sm fibre fed into a 50/50 y-coupler with two tails leg a and leg b. Both legs are the same and are 100ft sm fibre. I realise both legs with optical events are overlaid in optical trace as lengths are the same. What puzzles me is that if leg b is disconnected and loss measured across coupler to leg a returns 3.5dB now if leg a is disconnected and b connected the loss is 3.8dB and finally when both legs connected the loss comes in aprox 2.4dB. Does anyone know what is happening here?