Designed to provide either 1310 nm or 1550 nm wavelengths, this optical light source is the perfect tool for providing a stable light source for single mode fiber measurements. This optical light source features the following: Highly stable output power and wavelengths Has four different modulation outputs (CW, 270 Hz, 1 kHz, 2 kHz) at 1310 nm and 1550 nm wavelengths Flush button design makes it easy to use and prevents dust from entering the unit Shatter-resistant sleeve protects the light source from falls or other damage Backlit LCD screen provides a clear display, ideal for dark places