A fault locator with a 2.5mm universal interface and a 30km range is a common, pen-style Visual Fault Locator (VFL) used to detect breaks and faults in fiber optic cables. These devices emit a bright red laser (typically 650nm wavelength) that allows technicians to visually pinpoint problem areas in the fiber. 

Product Details and Features

These VFLs are essential tools in fiber optic engineering for tasks such as fiber tracing, routing, and continuity checks. 

• Function: They work by injecting visible red light into the fiber. At the point of a break, sharp bend, or poor connection, the light refracts and creates a visible glow around the faulty area, allowing for easy and accurate identification of the problem.
• Interface Compatibility: The 2.5mm universal connector is designed to be compatible with common fiber optic interfaces, including SC, ST, and FC connectors. For LC and MU connectors, an additional 1.25mm adapter is typically required.
• Range and Power: With an output power of up to 30mW, these VFLs can effectively detect faults over a distance of 20-30 kilometers. The high-efficiency power circuits ensure stable power output.
• Operating Modes: This models offer both Continuous Wave (CW) and Pulsed mode operation. The pulsed mode can help in locating faults under high ambient light conditions and can also help improve battery life.
• Design: They typically feature a durable, pen-type design with an aluminum alloy body and stainless steel head to prevent crash and dust damage. They are compact and lightweight for portability and field use.
• Additional Features: It come with useful additions like an LED lighting function for working in dark environments, a dust cap to protect the optical port, and options for AA batteries or USB-rechargeable lithium batteries.