about 2 octaves the complication this gives rise to is that there are two possible optical wavelengths corresponding to each diffracted angle and some coding scheme would have to be used to distinguish between the two the simplest would be a time multiplex between the two frequencies but this would entail a reduced probability of intercept other coding schemes can be envisioned and these will have to be explored as the concept is developed a schematic of a representative spectrum analyzer system using the aodlf is shown in fig5 this includes input and output polarizers focusing lens and photo detector array to provide the readout by incorporating a two dimensional detector array spectral imaging may be done in which one dimension contains the spatial information and the other dimension contains the spectral information of a line scanned image an additional capability of the aodlf that will be useful for satellite based information processing system applications will be its operation in a derivative mode for enhanced snr of coherence detection in the presence of high incoherent background this is simply done by imposing a very small frequency modulation on the rf applied to the aodlf then by phase locking each of the detector element signals at the fundamental and first harmonic of the fm we observe the first and second spectrum derivatives of each resolution element the great advantage over the aotf is that the entire spectral range is under continuous monitoring operating the aodlf in the derivative mode brings to light another feature of this device which may be functionally useful by imposing an fm onto the cw wave which excites the cell there will instantaneously be a band of acoustic frequencies u03b4f present in the aperture at all times therefore the wavelength.