This paper will introduce and evaluate a novel sensor based on embedding a triangular-lattice photonic crystal into the core of an optical fiber. We will start by mentioning previous results reported recently for a similar sensor which used a rectangularlattice photonic crystal. We will argue that such sensors (i.e., which embedded photonic crystals into the core of standard monomode optical fibers) are highly sensitive, and will show that the novel sensor (which relies on a triangular-lattice photonic crystal) achieves an accuracy of about 10 pico-meters, this being 22% better than that of the sensor which uses a rectangular-lattice photonic crystal. Possible fabrication alternatives will also be mention. While these sensors have been analyzed only with respect to mechanical deformations, they could easily be used for a much wide range of measurements. This aspect, together with the ultra-small size (micro-meters) of such sensors makes them attractive candidates for future (lab-)on-chip applications.