Fabrication of a Handheld Optical Fibre Cable Fault Locator for Telecommunications Maintenance Engineers in Lagos State

Optical fibre networks form the backbone of broadband telecommunications infrastructure in Lagos State, South West Nigeria, and cable faults resulting from physical damage or installation defects cause costly service interruptions for millions of users. Professional optical time-domain reflectometry equipment for fault localization is expensive and often unavailable to field maintenance engineers at small and medium-scale internet service providers. This project presents the fabrication of a low-cost handheld optical fibre fault locator based on a visual fault locator principle, using a 650-nanometre red laser diode modulated at 1 Hz and 2 Hz to inject a visible light signal into the fibre core. Fault locations including breaks, bends, and connector losses are identified visually by the maintenance engineer as points where light leaks out of the fibre sheathing. A microcontroller-based pulse generator controls the laser modulation rate, and a battery-powered enclosure provides portable operation for field use. The device was tested on five optical fibre sample cables with intentionally introduced faults at known positions. Fault detection success rate was 100 percent for physical breaks and 80 percent for micro-bend faults within the visible detection range of the laser, typically up to 3 kilometres on single-mode fibre. The total manufacturing cost was approximately 9,500 Naira. The study documents the limitations of the visual method relative to OTDR and recommends the device as a rapid screening tool complementary to full OTDR testing for Lagos field maintenance teams. Keywords: optical fibre, fault locator, visual fault locator, telecommunications, Lagos State