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Abstract

A grating-in-etalon wavelength division multiplexing device is disclosed. In one aspect the device includes an etalon structure with a single volume (or Bragg) diffraction grating, multiple superimposed volume diffraction gratings or a binary volume supergrating is interposed between the reflective opposed faces of the etalon. The etalon includes a tilt mechanism for tilting one or both of the reflective faces at a preselected angle with respect to each other from the parallel. A multiple wavelength light beam is directed through the volume grating in different preselected directions so that light of wavelengths satisfying the Bragg condition on each traversal of the grating is diffracted in a direction different from the direction of the incident beam. The diffracted beam exits the etalon and is wavelength interrogated in a detector while the undiffracted wavelengths propagate through the grating to be reflected from the opposed mirror face back through the volume grating. On this traversal the diffracted light exits through the other side of the etalon and is wavelength interrogated in another wavelength sensitive light detector. In another aspect of the invention the WDM device is fabricated from an etalon waveguide with reflective opposed faces and having a Bragg grating (or multiple gratings) written into the waveguide between the reflective faces. Polarization insensitivity is achieved by writing in two sets of gratings, one set to diffract ordinary polarized light and the other to diffract extraordinary polarized light so that when polarization state of light changes, the diffraction efficiencies are relatively the same.

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First Claim