Research On Miniaturized Multi-channel Fiber F-P Pressure Sensing Demodulation System Based On ARM Processor

Fiber optic F-P sensor demodulation is the key point of fiber optic F-P sensing technology.The miniaturization of F-P demodulation system and channel multiplexing technology are of great significance to expand the application range of F-P sensing fiber.Space-scanning F-P demodulation method based on low coherence interferometry has the advantages of good stability,high reliability and easy to realize multi-channel multiplexing,but the signal quality of it can be affected by the LED light source.The LED output optical power of light source determines the fiber F-P demodulation system accuracy and long-term stability.This paper presents a miniaturized multi-channel fiber F-P demodulation system based on ARM processor.The system uses LED light source modulation and fiber array to achieve multi-channel multiplexing.Low coherence interferometric signals are detected by CCD.The CCD output analog signal is acquired and uploaded by the ARM processor.A fast self-adaptive method of LED optical output power is proposed,which is based on the evaluation of the SNR level through the difference filtering method.The analog dimming method implemented by the digital potentiometer allows the low coherence interferometric signal to maintain a high signal to noise ratio level.A small multi-channel fiber F-P demodulation system is designed and built.The demodulation system is experimentally validated by the envelope peak method and the monochromatic frequency absolute phase method.The main contents are as follows.1.This paper presents a power adaptive method for LED light source,using ARM processor to collect low coherence interferometric signal.The envelope of the interference signal is extracted by the differential filtering method.And the signal-to-noise ratio of the extracted signal is calculated.The pressure demodulation experiment is validated by the power adaptive method of LED light source.The results show that the adaptive method can effectively improve the demodulation accuracy of the system.Demodulation accuracy within 5-150 k Pa pressure range can reach within 0.05% F.S.Response rate analysis was performed by adding a mutation to reduce the signal-to-noise ratio.The experimental results show that the system can recover the high SNR rapidly in 0.36 s.The stable operation of the system is ensured.2.A multi-channel fiber F-P demodulation system is built.The hardware control circuit of multi-channel system is miniaturization designed.The performance of the circuit system is tested according to the required signal requirements.Ripple factors of channel gating,frame synchronization,point synchronization and other signals are low,which is satisfactory.The drive capacities of each channel in the LED driver circuit are more than 0.95 A.The functions of ADC acquisition,calculation,I2 C communication,data uploading of miniaturization demodulation system are tested.The acquisition speed of ADC is up to 1MHz,and the speed of data uploading can reach 500KB/s.The system runs stably.3.The demodulation experiment of the miniaturized multichannel fiber F-P demodulation system based on ARM processor is carried out.The monochromatic frequency absolute phase method is used for demodulation in the pressure range of 3-283 k Pa.The demodulation accuracy of each channel is better than 0.07% F.S.,and the demodulation results of each channel are almost the same.