Abstract: A wearable transmitter assembly includes a housing containing a radio frequency transmitter and tamper detecting circuit that are attached to an appendage of an individual with a buckle and strap. A light emitter and a light sensor are disposed in the housing and extend to the outside of the housing through one or more apertures. The strap includes an embedded optical fiber. Attachment of the housing to the buckle positions the emitter and sensor adjacent the ends of the optical fiber in the strap to complete an optical path or circuit from the emitter around the appendage to the sensor. The housing is sealed closed, including sealant between the emitter, the sensor and the aperture, providing a water tight enclosure for said transmitter from the time of its manufacture. Attachment of the housing to the buckle completes a seal blocking contaminates, such as water, water vapor, and soap from the ends of the optical fiber, the emitter and the sensor.