An optical signal processing device for white-light interferometry, based on CPLD

This paper presents an optical signal-processing device for the interrogation of fiber-optical sensors, and a method for extracting the measured parameter from an interrogated optical-sensor. The proposed signal processor is an all-fiber device based on a Sagnac interferometer and piezo-electric cylinder as used for optical path-length modulation. The proposed design combines the low-coherence interferometry for sensor interrogation with a high-coherence source for simultaneously-providing a reference that is necessary for evaluating and processing signals generated by low-coherent interrogation of the sensor. The entire control and signal processing was implemented within a complex programmable logical array. Thus, high frequency signal processing was demonstrated using minimum number of external electronic components. This system has been tested by using a Michelson interferometer as a strain sensor. An optical path scanning range of over 1 mm and at 20 kHz sampling rate was demonstrated, in practice.