Multiplexing optical sensors using a spatial light modulator

The advantages of using spatial light modulators (SLMs) as the multiplexing elements are that low crosstalk levels and high signal to noise ratios (SNR) are attainable. In addition, a substantial number of sensors can be incorporated in the network without serious loss in performance. SLMs are flexible multiplexers which allow a range of multiplexing methods to be used. In this paper time division multiplexing (TDM), frequency division multiplexing (FDM), and code division multiplexing (CDM) are considered. The advantages and limitations of the three multiplexing systems are discussed and their relative performances are compared. The paper concludes with a report on a network incorporating twelve discrete strain sensors using TDM for which the average SNR was 60 dB and the average crosstalk level was better than -70 dB.