The diaphragm-based sensor tip, which has a critical design in Fabry-Perot fiber optic acoustic sensor production, directly affects device performance. Fabry-Perot fiber optic acoustic sensors tip designs and investigations on different geometric dimensions and different diaphragm materials continue in the literature. In this study, it is predicted that graphene-like two-dimensional In2Se3 single crystal can be used for the diaphragm material which we report for the first time in the literature. Analytical calculations and numerical simulations have been carried out in order to use two-dimensional In2Se3 single crystals as diaphragm material for Fabry-Perot fiber optic acoustic sensors tip production. The calculation results of the Fabry-Perot fiber optic acoustic sensors tip we designed using In2Se3 single crystal are compared with conventional sensor tip made from Si, SiO2 and graphene as a diaphragm in the literature. Since In2Se3 crystal has a high refraction index, sensor visibility allows for long Fabry-Perot cavities, which creates alternative solutions where very short Fabry-Perot cavities are not possible. Another advantage of this feature is that the inner surface of the diaphragm does not need to be coated with reflective materials like gold, silver etc. Using the high density of In2Se3 crystals for diaphragm materials results in reducing the percentage of frequency in transitions from less dense to more dense environments. According to the simulation results, it is seen that it has high sensitivity of 64.12 nm/kPa and this is the result of having a low Young's modulus than other diaphragm materials like Si, SiO2, graphene of the same geometry reported in the literature. The calculation results were also obtained for other materials as 26.54 nm/kPa, 62.58 nm/kPa, and 4.57 nm/kPa for Si, SiO2 and graphene, respectively. The innovative diaphragm design proposed in this work for Fabry-Perot fiber optic acoustic sensors tip production has been advised alternative solutions when sensor sensitivity and visibility must be considered.