Our prototype fringing spectrometer is being tested on sunlight and laboratory spectral sources. Source light from input fiber optionally passes through an iodine vapor cell to imprint a reference spectrum.
Light passes through a wide angle interferometer which imprints fringes.
Grating spectrometer disperses fringes so that major spectral lines do not overlap each other, which would diminish fringe visibility. Fringing spectum is detected by CCD detector. The shift in phase of the fringes of the source light relative to the iodine fringes yields the Doppler shift of the source. We are now replacing the grating spectrometer shown here with a smaller, more efficient, and 7x greater bandwidth spectrometer using volume phase holographic technology, shown below.