A method of detecting tampering with a conveyance medium may include determining a baseline brightness level detected at opposing ends of an optical fiber segment disposed proximate to the conveyance medium, determining whether a change in brightness above a threshold level occurs, and providing an output indicating that a breach in continuity of a shielding material that shields both the conveyance medium and the optical fiber segment from exposure to ambient light has occurred in response to the change in brightness being above the threshold level.