Patent ID: 6941072

Claim:
An optical demultiplexer device comprising: a first input/output port through which a wavelength division multiplexed (WDM) signal comprising a plurality of wavelength channels is input along a first path in free space; a first optical filter disposed in the first path for transmitting at least a first predetermined wavelength channel of the WDM signal, and for reflecting a first sub-signal of the WDM signal along a second path in free space at an angle to the first path; a first drop port for outputting at least the first predetermined wavelength channel transmitted by the first optical filter; a first prism for redirecting the first sub-signal of the WDM signal traveling along the second path to a third path; a second optical filter disposed in the third path for transmitting at least a second predetermined channel of the WDM signal, and for reflecting a second sub-signal of the WDM signal along a fourth path in free space at an angle to the third path; and a second drop port adjacent to the first input/output port for outputting at least the second predetermined channel transmitted by the first optical filter; whereby the position, of the second drop port is independent of the angle between the second and third paths, and the required distance between the first drop port and the second drop port is reduced.