Hi Mandar!

Do you talk about changes in losses? I think that when you speak in displacement, you refer to different positions of the connector, or the core fiber, relative to a reference. Is the displacement longitudinal or transverse? Remember, POFs has a large core diameter, and many modes can propagate in its core. So, some transverse misalignment, or longitudinal displacement of the fiber end with respect to reference can introduce losses. The photodiode need have a large sensing area, to absorb all flow of photons falling on it, if it is the reference.