A vital signs detecting device and a method for detecting vital signs are provided. The vital signs detecting device comprises a detection unit; a multimode optical fiber configured to be connected to a light source and to the detection unit; a mechanical structure configured for receiving a pressure exerted by a person's body as a result of one or more of a group consisting of a movement of the person's body, a respiratory action of the person's body and a heart beat action of the person's body and to cause microbending of the multimode optical fiber under the exerted pressure and; wherein the multimode optical fiber is disposed between first and second sets of microbending elements of the mechanical structure substantially in a direction of the exerted pressure.