A pressure sensor is formed on a substrate, the surface of the substrate having a p-n junction and a shell with a beam inside the shell over the p-n junction. The beam and the shell and the p-n junction surface form optical Fabry-Pérot cavities. An optical fiber is positioned in a hole formed in the underside of the substrate below the p-n junction. Light from the fiber charges the p-n junction and drives it into vibration mode. Pressure changes change the tension in the diaphram to vary the frequency with changes in pressure, so that pressure can be detected.