A passive optical network for transmitting digital signals incorporates sub-octave filters for the removal of distortions introduced into the signals as they are transmitted over the fiber optic cable of the network. Stated differently, second order distortions that result when the light beam carrying the digital signals is passed through a fiber optic cable are removed by the sub-octave filter. Further, the employment of another passive optical network on the same fiber optic cable with the present network is provided for. And, considerations for ensuring the compatibility of upstream and downstream transmission frequencies with the sub-octave filters are disclosed.