Abstract: Conventional ply composites have shortcomings such as low interlaminar strength, which limit their application in the field of aeronautics and astronautics. Braided composites can overcome those limitations. Having good strength and antifatigue performances, carbon hermetically coated optic fibers have been used in benthal optic cables, military guiding optic fibers and optic fiber sensing systems under harsh circumstances. In this paper, the application of carbon hermetically coated optic fibers in braided carbon/epoxy composites is studied through experiments. The optic fibers are successfully braided into 3-D braided composite testpieces and processed through Resin Transfer Molding. Optic performance parameters of the optic fibers before, after their being braided into the testpieces, and after the molding process are tested, and compared. The results show that those parameters nearly do not change. Polarimetric optic fiber sensors using carbon hermetically coated optic fibers are designed for measuring the internal strain in braided testpieces under bending loads.