Why are fibers birefringent because of the chemical makeup of the fiber because the fiber is a natural fiber because the fiber has long range order because the fiber has a refractive index greater than 1.52 because the refractive index is less than 1.52

Because of the chemical makeup of the fiber.

Explanation:

The birefringence is the difference between the refractive index of a fiber in a direction at parallel to the fiber axis and in a direction at right angles. It is caused by asymmetric core shape for the two axes, and majorly one of the manufacturing imperfections. It helps in controlling polarization property inside the fiber.