An optical interferometric MMG sensor is presented. It uses the feedback effect in a laser diode to measure the vibration generated by the MMG at the skin surface. Its key features are noncontact measurement, high sensitivity, and extended bandwidth toward low frequencies (1 Hz). Furthermore, as it is able to recover with a good accuracy the shape of vibrations ranging from 1 µm peak-to-peak, the MMG is expressed in the physiological unit (micrometer) rather than the sensor dependent unit. The MMG measurement conditions are reviewed through a clinical protocol, including the perturbation causes. This probe is compared with a classical microphone based sensor, and thereby the influence of the coupling between the muscle and a contact sensor is demonstrated.