Currently, reconfigurable OADM has become the development direction. In addition to using the optical switch dynamically select the upper and lower wavelengths, the use of a tunable filter is a hot spot.

Italy reported a use of SiO2/Si acoustic waveguide made tunable drop filter for 4-way WDM system wavelength interval 3.2nm, drop crosstalk between the brightest less than 18dB;
   
Japan reported OADM using the vertical and in the opposite direction of the semiconductor waveguide coupled constituted, in the tunable range 11nm loss varies by less than 1dB;
   
Canada reported a tunable OADM using FBG made in 1.55Lm window has eight tunable filter, various wavelength interval 0.8nm, thermal tuning make FBG linear grating period changes occur, so that band relaxed;
   
Chinese scholars are also based on acousto-optic tunable filter OADM, the device extinction ratio reaches 32dB, insertion loss of 3dB.