Free-space multi-port wavelength router with broad wavelength passbands

A free space N×N wavelength router for directing a WDM optical signal having a group of N discrete adjacent-in-wavelength channels received from one of N input optic ports to a group of N output optic ports, said router having an optical axis and comprising:

• an optical diffraction grating having a periodic structure and being oriented in a substantially perpendicular direction relative to a first direction;
• a lens for receiving the WDM optical signal from one of said input optic ports and for collimating the signal on said grating, said grating providing angular displacement, in the first direction relative to the optical axis, to the discrete channels as a function of the wavelength of each discrete channel and directing said angularly-displaced discrete channels to said lens for focusing said angularly displaced discrete channels;
• an array of optical elements arranged along the first direction and positioned for receiving, at each optical element, a select one of said angularly-displaced discrete channels, each optical element producing a corresponding spatial shift along a second direction substantially orthogonal to the first direction for imparting an associated spatial shift to each received discrete channel and for directing each spatially-shifted channel to said grating and to said lens for defining a first pass of said channels through said router;
• and
• a reflective optical element for receiving said spatially shifted channels from said lens and for directing said channels back to said lens, said grating and said array, so as to cause a second pass of said channels through said router and an output of said spatially-shifted channels from said second pass to one of said group of said N input fibers and said group of said N output fibers.

A free space N×N wavelength router for directing a WDM optical signal having a group of N discrete adjacent-in-wavelength channels received from one of N input optic ports to a group of N output optic ports, said router having an optical axis and comprising:

• a first router stage having:
• a first optical diffraction grating having a periodic structure and being oriented in a substantially perpendicular direction relative to a first direction;
• a first lens for receiving the WDM optical signal from one of said input optic ports and for collimating the signal on said grating, said grating providing angular displacement, in the first direction relative to the optical axis, to the discrete channels as a function of the wavelength of each discrete channel and directing said angularly-displaced discrete channels to said first lens for focusing said angularly-displaced discrete channels;
• a first array of optical elements arranged along the first direction and positioned for receiving, at each optical element, a select one of said angularly-displaced discrete channels, each optical element producing a corresponding spatial shift along a second direction substantially orthogonal to the first direction for imparting an associated spatial shift to each received discrete channel and for directing each spatially-shifted channel to said grating and to said lens for defining a first pass of said channels through said router;
• and
• a second router stage positioned at an angle relative to an optical axis of said first router stage and having:
• a second optical diffraction grating having a periodic structure and being oriented in a substantially perpendicular direction relative to a third direction;
• a second lens for receiving the spatially shifted channels from said first router stage and for collimating the spatially shifted channels on said grating, said grating providing second angular displacement, in the third direction which is angularly offset from said first direction, to the spatially shifted channels as a function of the channel wavelengths and directing said second angularly-displaced discrete channels to said second lens for focusing said angularly displaced discrete channels;
• and
• a second array of optical elements arranged along the third direction and positioned for receiving, at each optical element, a select one of said second angularly-displaced discrete channels, each optical element producing a corresponding spatial shift along the third direction substantially orthogonal to the third direction for imparting an associated spatial shift to each received discrete channel and for directing each spatially-shifted channel to said second grating, to said second lens and to the output ports.