Abstract: An optical assembly having a light circulating device is used for routing light and may be used with a receiver. The assembly includes a tunable filter for receiving light traveling from the light circulating device and for selecting which wavelengths of light that reach the receiver. A wavelength routing mechanism optically coupled to the tunable filter and located downstream from the circulator is used to prevent undesired dropping of signal wavelengths. The mechanism has a first operational mode preventing light from reaching the receiver and a second operational mode allowing light to reach the receiver. When the filter is tuning, the mechanism is preferably in the first operational mode. Preferably, the assembly has an arrangement of mirror reflections on the first path and the second path so that an even number of mirror reflection are experienced on one path and an odd number on the other path as light is recombined.