A HADAMARD-MULTIPLEXED SPECTROMETER BASED ON AN ACOUSTOOPTIC TUNABLE FILTER

This paper presents a Hadamard-multiplexed spectrometer based on an ac ousto-optic tunable filter (AOTF). The multifrequency capability of th e AOTF enables it to be operated in a multiplexed mode. The AOTF can t hen be operated at lower power to obtain improved passband characteris tics without a reduction in the signal-to-noise ratio as compared to a higher-power, nonmultiplexing instrument. An expandable, PC-based spe ctrometer has been developed to illustrate this technique, The current implementation provides seven-frequency Hadamard multiplexing and col lects the spectra in multiplexed blocks. The AOTF is controlled via IE EE-485 bussed VHF synthesizer modules based on a hybrid DDS/PLL techni que, The modular design allows convenient system expansion, The design of and specifications for this instrument are discussed.