grating filter for FTTX applications are reflective filters integrated with the LC or SC adaptors, which reflect 1650nm maintenance wavelength and transmit all other telecommunication wavelengths. They can be used to monitor live networks utilizing OTDR operating at 1650nm. The 1650nm fiber optic reflector are currently considered the best way of implementing real-time end-to-end (OLT to ONT) monitoring of the optical layer in live FTTX networks. AtGrating OTDR reflector is based on FBG technology to reflect OTDR test signal. Following with mass production of monodirectional 1650nm reflector, AtGrating has been capable of making bidirectional1650nm reflector in high performance. https://www.atgrating.com/products/otdr-fbg-filter.html