Disclosed herein is a routing band-pass filter for routing optical signals between multiple optical channel sets. In particular, disclosed is a wavelength-division multiplexing (WDM) optical assembly including a first WDM filter, a second WDM filter, and a first routing filter. The first and second WDM filter are in communication with first and second sets of channel ports, respectively. The routing filter has a routing passband and forms a primary routing optical path for signals outside the routing passband between the first WDM filter and a common port. The routing filter also forms a secondary routing optical path for signals within the routing passband between the second WDM filter and the common port. The routing band-pass filter increases the number of channel ports in optical communication with a common port while maintaining signal integrity and increasing speed.