Hi, I'm an optical physicist who started dealing with optical fibers lately.

My question is about a specific type of optical fiber connectorization,
called APC. This type of fiber ending is a flat surface with 8 degree
angle, designed to minimize the return loss (amount of back
reflection) from the fiber tip. I would like to know why they are
using this specific angle (8 degree) and whether this is a value
specific to glass-air interface. In my case, I'm trying to use the
fiber in the water (refractive index 1.33, as opposed to 1 for air),
and wonder if APC ending with 8 degree angle will do any good in this
case as well, in terms of reducing back-reflection.

Thanks much in advance.