A novel fiber optic liquid level sensor based on laser radar (ladar) is reported here. Using the perfect technique of ladar in which the phase of amplitude modulated light wave reflected from the liquid surface is com...A novel fiber optic liquid level sensor based on laser radar (ladar) is reported here. Using the perfect technique of ladar in which the phase of amplitude modulated light wave reflected from the liquid surface is compared with that of original modulation signal, the distance can be measured precisely. A special symmetric compensating coaxial optical system is proposed to eliminate many adverse effects. It realized the one-time electronic-free optical measurement on a simulated oil tank and achieves an accuracy of 0.3%, within a temperature range of -10 ℃～+40 ℃ over a measuring of 0～10 m.展开更多
The success of any perimeter intrusion detection system depends on three important performance parameters： the probability of detection （POD）, the nuisance alarm rate （NAR）, and the false alarm rate （FAR）. The ...The success of any perimeter intrusion detection system depends on three important performance parameters： the probability of detection （POD）, the nuisance alarm rate （NAR）, and the false alarm rate （FAR）. The most fundamental parameter, POD, is normally related to a number of factors such as the event of interest, the sensitivity of the sensor, the installation quality of the system, and the reliability of the sensing equipment. The suppression of nuisance alarms without degrading sensitivity in fiber optic intrusion detection systems is key to maintaining acceptable performance. Signal processing algorithms that maintain the POD and eliminate nuisance alarms are crucial for achieving this. In this paper, a robust event classification system using supervised neural networks together with a level crossings （LCs） based feature extraction algorithm is presented for the detection and recognition of intrusion and non-intrusion events in a fence-based fiber-optic intrusion detection system. A level crossings algorithm is also used with a dynamic threshold to suppress torrential rain-induced nuisance alarms in a fence system. Results show that rain-induced nuisance alarms can be suppressed for rainfall rates in excess of 100mm/hr with the simultaneous detection of intrusion events. The use of a level crossing based detection and novel classification algorithm is also presented for a buried pipeline fiber optic intrusion detection system for the suppression of nuisance events and discrimination of intrusion events. The sensor employed for both types of systems is a distributed bidirectional fiber-optic Mach-Zehnder （MZ） interferometer.展开更多
In this paper,we present a novel oil level monitoring sensor based on string tilted fiber Bragg grating(TFBG).The measurement range and sensitivity of oil level monitoring can be modulated via changing the length and ...In this paper,we present a novel oil level monitoring sensor based on string tilted fiber Bragg grating(TFBG).The measurement range and sensitivity of oil level monitoring can be modulated via changing the length and number of string tilted fiber gratings.The transmission spectrum of string TFBGs immersed in oil changes obviously with the oil level variation.Experiments are conducted on three 2 cm-length serial TFBGs with the same tilted angle of 10o.A sensitivity of 3.28 dB/cm in the string TFBG sensor is achieved with good linearity by means of TFBG spectrum characteristic with peak-low value.The cladding mode transmission power and the amplitude of high order cladding mode resonance are nearly linear to the oil level variation.This kind of sensor is insensitive to temperature and attributed to be employed in extremely harsh environment oil monitoring.展开更多
The work describes a surface plasmon resonance(SPR)sensor that measures the liquid level and refractive index(RI)simultaneously.The sensor is fabricated by a polymer optical fiber(POF)with a side-polished spiral struc...The work describes a surface plasmon resonance(SPR)sensor that measures the liquid level and refractive index(RI)simultaneously.The sensor is fabricated by a polymer optical fiber(POF)with a side-polished spiral structure.The POF is wound around a plastic rod with the same pitch and polished into a series of separated side-polished areas to form the sensor probe.Afterwards,the polished surfaces are coated with a gold layer to construct the SPR sensor.The proposed sensor can provide multi-point liquid-level measurement besides RI sensing.The influences of structural parameters such as the bending radius,polishing depth,and pitch on the sensing performance are experimentally studied.The experimental results indicate that the RI could be determined by employing the SPR wavelength shift,and the RI sensitivity of 1862 nm/RIU within the 1.34–1.40 range is obtained.Moreover,the SPR peak’s depth variation can be utilized to monitor the liquid level,and the sensor can provide adjustable resolution and a measurement range for liquid level sensing.With its simple fabrication,low cost,and flexible sensing ability,this sensor probe is suitable for the usage in biochemical applications.展开更多
文摘A novel fiber optic liquid level sensor based on laser radar (ladar) is reported here. Using the perfect technique of ladar in which the phase of amplitude modulated light wave reflected from the liquid surface is compared with that of original modulation signal, the distance can be measured precisely. A special symmetric compensating coaxial optical system is proposed to eliminate many adverse effects. It realized the one-time electronic-free optical measurement on a simulated oil tank and achieves an accuracy of 0.3%, within a temperature range of -10 ℃～+40 ℃ over a measuring of 0～10 m.
文摘The success of any perimeter intrusion detection system depends on three important performance parameters： the probability of detection （POD）, the nuisance alarm rate （NAR）, and the false alarm rate （FAR）. The most fundamental parameter, POD, is normally related to a number of factors such as the event of interest, the sensitivity of the sensor, the installation quality of the system, and the reliability of the sensing equipment. The suppression of nuisance alarms without degrading sensitivity in fiber optic intrusion detection systems is key to maintaining acceptable performance. Signal processing algorithms that maintain the POD and eliminate nuisance alarms are crucial for achieving this. In this paper, a robust event classification system using supervised neural networks together with a level crossings （LCs） based feature extraction algorithm is presented for the detection and recognition of intrusion and non-intrusion events in a fence-based fiber-optic intrusion detection system. A level crossings algorithm is also used with a dynamic threshold to suppress torrential rain-induced nuisance alarms in a fence system. Results show that rain-induced nuisance alarms can be suppressed for rainfall rates in excess of 100mm/hr with the simultaneous detection of intrusion events. The use of a level crossing based detection and novel classification algorithm is also presented for a buried pipeline fiber optic intrusion detection system for the suppression of nuisance events and discrimination of intrusion events. The sensor employed for both types of systems is a distributed bidirectional fiber-optic Mach-Zehnder （MZ） interferometer.
基金supported by the National Natural Science Foundation of China (No.51079080)
文摘In this paper,we present a novel oil level monitoring sensor based on string tilted fiber Bragg grating(TFBG).The measurement range and sensitivity of oil level monitoring can be modulated via changing the length and number of string tilted fiber gratings.The transmission spectrum of string TFBGs immersed in oil changes obviously with the oil level variation.Experiments are conducted on three 2 cm-length serial TFBGs with the same tilted angle of 10o.A sensitivity of 3.28 dB/cm in the string TFBG sensor is achieved with good linearity by means of TFBG spectrum characteristic with peak-low value.The cladding mode transmission power and the amplitude of high order cladding mode resonance are nearly linear to the oil level variation.This kind of sensor is insensitive to temperature and attributed to be employed in extremely harsh environment oil monitoring.
基金supported by the Guangxi Natural Science Foundation,China(Grant Nos.2023GXNSFDA026040 and ZY23055018)National Natural Science Foundation of China(Grant Nos.62365003,62364006,and U23A20282)+2 种基金the Fonds de la Recherche Scientifique under the Postdoctoral Researcher Grant(Chargéde Recherches)Belgium to Xuehao HUthe Innovation Project of Guilin University of Electronic Technology Graduate Education,China(Grant No.2024YCXS202).
文摘The work describes a surface plasmon resonance(SPR)sensor that measures the liquid level and refractive index(RI)simultaneously.The sensor is fabricated by a polymer optical fiber(POF)with a side-polished spiral structure.The POF is wound around a plastic rod with the same pitch and polished into a series of separated side-polished areas to form the sensor probe.Afterwards,the polished surfaces are coated with a gold layer to construct the SPR sensor.The proposed sensor can provide multi-point liquid-level measurement besides RI sensing.The influences of structural parameters such as the bending radius,polishing depth,and pitch on the sensing performance are experimentally studied.The experimental results indicate that the RI could be determined by employing the SPR wavelength shift,and the RI sensitivity of 1862 nm/RIU within the 1.34–1.40 range is obtained.Moreover,the SPR peak’s depth variation can be utilized to monitor the liquid level,and the sensor can provide adjustable resolution and a measurement range for liquid level sensing.With its simple fabrication,low cost,and flexible sensing ability,this sensor probe is suitable for the usage in biochemical applications.
