In this work, we describe the spectral properties of fiber Bragg gratings (FBGs) in Hi‐Bi PANDA fibers subjected to diametrical compression and fibers with internal electrodes, as two examples of the facilities offered by specialty single‐mode fibers for processing optical signals. Due to the complex structure of the fibers, the induced effects on the fiber effective birefringence are presented and discussed, based on numerical analysis with the finite element method.