Enhancement of modal birefringence in solid core Bragg fibers with high-index-contrast claddings

•We present two highly birefringent Bragg fibers with high-index-contrast claddings.•Our presented fibers have higher birefringence than the low-index-contrast ones.•The characterized modal birefringence can serve for sensing refractive index.•Both birefringence and confinement loss are influenced by photonic bandgap effect.