WDM CEx Filter module (Coeximstence Element) used in the optical monitoring of the FTTH network and for the distribution of services on PON architecture, which are described in the ITU-T recommendation G.984.5. These components allow the coexistence, on a single optical fiber, of G-PON, XG-PON, NG-PON2 systems together with the OTDR signal for monitoring the optical connection.