An optical device includes an optical system mount plate, a casing, and a screw-hole forming part. The device comprises a controllable switching element that is designed to take on at least two states, specifically a first state with a first resistance and a second state with a second resistance that is lower than the first resistance. The coupling member may be configured to electrically couple contact pads on a top surface of the flexible circuit to contact pads on a top surface of the rigid circuit. Each of the end connectors comprises a main body defining an arcuate body engagement surface, and at least two arms which are attached to the main body. The tin-doped corecladding interface region 14 comprises a low concentration gradient of tin dioxide, which advantageously results in a de minimis refractive index change, resistance to hydrogen incursion, and thermal stability of any fiber Bragg gratings written into the interface region 14.