Setting a circular polarization at an FBG

lichen

I have an optical fiber system that consists of a linear polarizer, a manual polarization controller, and a reflector (Bragg grating).

I want to make sure that the polarization at the Bragg grating is circular (either right or left circular will do).

Can someone tell me if the following method is sound:

By monitoring the reflection back from the Bragg grating, I use the polarization controller to ensure I am getting all my light back on the axis that I send it in by. Therefore at the halfway point (the reflector, my point of interest) it must be circularly polarized.

My reasoning is that if the light goes in linearly polarized on one axis, and then is transformed by the waveplate, it can only come back out again on that same axis if it has become, for instance, left circular by the time it is being reflected. The reflection then makes it right circular, and then by the time this has reversed through the waveplate system again it has undergone a further pi/2 shift taking it from right circular to linear on the original axis.

Does this check out?

Many thanks.