USource 1650 optical band reflector built-in FBG(Fiber Bragg Grating), packaged in SC or LC adapter female to male, which reflects more than 99.5% of 1650 OTDR signal back and pass other wavelengths from 1260-1625, widely used on ONU side.
There are others models available. Reflect: 1577/1625/1650 Applications: