Existing fiber optics (FOs)-based sensors, including mechanical deformation ones rely on structures embedded along the length of the FO. In this paper, we introduce and evaluate photonic crystals (PCs) embedded into FO cores acting as mechanical deformation sensors which are departing from this classical approach as the PCs are perpendicular to the length of the FO. Another noteworthy difference from classical FO-PC based sensors is that while classical ones rely on amplitude variations, the ones presented here use the phase variations of the electromagnetic components for assessing mechanical deformations. We start with a straightforward rectangular-lattice PC while also exploring a triangular-lattice PC. Light transmission simulations through the proposed FO-PC mechanical deformation sensors were performed using EM Explorer, and revealed their behaviors under small mechanical deformations. These simulations (of the rectangular-lattice and triangular-lattice PCs) show that these two FO-PC mechanical deformation sensors have roughly the same sensitivities while the triangular-lattice PC triggers at a lower threshold than the rectangular-lattice PC.