I'm trying to understand how the (power) loss in optical fibre works and I'm having some trouble.
This is a classic 50/50 fused fibre Y coupler. The output on port 2 is the same as port 3 (so half the power of port 1 plus the losses).
The losses considered here are the coupling loss (same for each port) and the radiated loss at the point of the split. We want to measure the coupling loss.
So my first idea would be to go from port 2 and measure the loss. However, while the radiated loss might be smaller, it seems unlikely that it would completely bypass it. Going from port 3 would bring the same result.
So is there any way I can measure the coupling loss in this configuration?