The sender is for Gigabit Ethernet and multimode fiber or for single-mode fibers up to 5 km at 1300 nm. The connector output can be adapted to any cable plant with hybrid adapters or hybrid cables. This unit is easy to operate with only a wavelength/power switch, which selects optical wavelengths or disables the unit. The light source is designed for performing insertion loss measurements on fiber optic links when used with an optical power meter. Whether testing outside plant or premise an optical source is the perfect tool when combinated with an optical power meter. The output is stabilized to ensure accurate test results per current TIA/EIA requirements. The wavelengths are individually adjustable with a mechanical screw to have a variable attenuator or to reduce the output power. This make it able to save battery power when high optical output power is not necessary, or to turn up the power to test long runs. The sender is delivered in a protective rubber boot.