A health monitoring device for detecting blood pressure having a blood pressure sensor including a first fiber Bragg grating (FBG) with a refractive index is configured to be placed in contact with a person's skin approximate to an artery or vein. A baseline sensor that includes a second fiber Bragg grating (FBG) also having a refractive index is configured to be placed in contact with a person's skin away from an artery or vein to provide a baseline refractive index. The device pulses light waves through the FBGs to provide a processor with reading of the refractive index from the FBGs. Based on the effective shifts of the Bragg wavelength due to axial strain on the FBGs, a blood pressure estimator estimates systolic and diastolic blood pressure based on a calibration curve comparing pressure against strain.