A modulated reflectance well telemetry apparatus having an electrically conductive pipe extending from above a surface to a point below the surface inside a casing. The apparatus comprises a container having base member and a peripheral containment wall and defining a total interior volume. Such techniques can be performed in conjunction with a spectral decomposition analysis. The diffraction grating of the first optical member and the diffraction grating of the second optical member are in close contact with each other. Once the gravel packing is completed, the swellable member may be activated to provide and supplement a hydraulic seal between adjacent zones. The inputoutput ports are coupled in alignment with the input port of the input waveguide and the output ports of the output waveguides.