Abstract: A multiwavelength sensor for sensing light scattered from a scattering medium includes a light source, a uniform broadband reflection grating at the Littrow position, a fiber, and a detector. Light from the source is incident on the grating, which diffracts the light. The fiber has a first end into which the light diffracted from the grating is received and has a second end from which the light exits, the fiber being positioned so that the light is incident upon and scattered from the scattering medium. At least some of the light scattered from the medium is scattered back into the second end and out of the first end and incident upon the diffraction grating. Light out of the first end and diffracted from the grating is incident on the detector. The system is fully transparent so that light traveling toward the second end and light traveling back toward the first end are optically isolated and cross-talk is substantially nonexistent.