we have diferent types of optical mux / demux boards in optix osn 9800 system which used for multplexing / demultiplexing signal to / from line and client side .. we have m40 / m48 / m40v / m48v ( ragarding to the mutiplexers ) which differ from the number of wavelngths it can support and capability of providing internal varible optical attenuation control or not which is denoted by "v" . Also we have D40 / D48 ( Regarding to the optical demultiplexers ) Depends on the wavelengths capacity