A fiber optic adapter is provided which controls the shear point for a fiber optic wiring system in a traffic control box and other fiber optic applications. The fiber optic adapter includes a bottom disc with a shear chamber and cutting blade, a center gasket, and a top disc with a splice chamber and splice block, for field assembly. Once the fiber optic cables have been positioned in the fiber optic adapter, the adapter is securely mounted to an immobile object in the control box. When a triggering event occurs, such as an accident at the traffic control box, the fiber optic cable is caused to engage the cutting blade to shear the fiber optic cable inside the adapter and not elsewhere in the fiber optic wiring system.