Abstract: elopment of a dual wavelength referenced intensity- modulated optical fiber sensor system is described. The system utilizes a single broadband LED source whose emission is spectrally sliced to provide two separate narrow-band wavelength signals, one as the measurand and a second as the reference. The allocated wavelength bands were selected to minimize differential intensity effects between the two optical signals that may arise from the LED thermal variations. Subsequently, the sensor system provides an output fully referenced for all major common-mode variations arising from the optical propagation effects as well as those due to the LED instability. The complete system comprises of a terminal transceiver unit which incorporates the system electronics together with a specially designed LED coupler and wavelength demultiplexer device which is interfaced to an optical sensor using a single optical fiber. A Graded-Index (GRIN) rod microlens together with an interference filter and a moving mirror element are used in the optical sensor to provide a mechanism for intensity modulation of the measurand signal. The performance characteristics of an advanced prototype sensor system are reported which demonstrate substantial amount of linear displacement. Finally, an initial investigation of the immunity of the system to common-mode variations is also described.!22
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