what are linearly polarized modes with respect to optical fibres?

Answer 1

I know you can feed longitudnally polarized photons into a fiberoptic cable and they will maintain that polarization. Whether you call it 'horizontal' or 'vertical' is up to the reference at the sending end. The fiber can twist and turn and the polarization may be different at the receiving end (relative to the sending end), but the longitudinality will be maintained.

Once you figure out the angle at which the photons are polarized you can use that as a reference, or you can simply twist the fiber to the same orientation as the sending end.

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