A new fiber optic sensing technology for measuring in-cylinder pressure in automotive engines was investigated. The optic sensing element consists of two mirrors in an in-line single mode fiber that are separated by some distance. To withstand the harsh conditions inside an engine, the Fiber Fabry-Perot Interferometer (FFPI) element was coated with gold and copper. The metal-protected fiber sensor was embedded into a small cut in the metal casing of the spark plug. At first, the sensing element was dipped in liquid gold and cured. Then the gold-coated fiber sensor was electroplated with copper. Finally, the metal-coated fiber sensor was embedded in the spark plug.; The spark-plug-embedded FFPI sensor was monitored using a signal conditioning unit. Field tests were carried out in a 3-cylinder automotive engine with a piezoelectric pressure sensor as a reference transducer up to about 3500 rpm. The fiber optic sensor data generally matched those measured by the piezoelectric reference sensor.; The use of a Vertical Cavity Surface Emitting Laser (VCSEL) diode as a light source in an FFPI optic sensor system was investigated. Reflected light from the FFPI sensing element was used to measure the optical path difference.; With a 1550nm VCSEL as the light source in a 12mm cavity length Fiber Fabry-Perot Interferometer, spectral characteristics were examined to determine the proper combination of dc bias current, modulation current amplitude and modulation frequency. Single VCSEL operation and regular fringe patterns were achieved.; The laser tuning was -41.2 GHz/mA and was determined from measurements of the shift in the spectral peak of the VCSEL diode output as a function of dc bias current. By testing the fringe movement as the FFPI sensor was heated, the temperature tuning coefficient for the optical length was determined to be 11 x 10-6°C.; The results of these experiments indicate that the use of VCSEL diode as a light source for the FFPI sensor offers a viable alternative to the use of Distributed Feedback (DFB) laser diodes for monitoring at a lower bias current and modulating current amplitude.
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机译:研究了一种用于测量汽车发动机缸内压力的新型光纤传感技术。光学传感元件由串联单模光纤中的两个反射镜组成,这些反射镜之间相隔一定距离。为了承受发动机内部的苛刻条件,光纤法布里-珀罗干涉仪(FFPI)元件涂有金和铜。金属保护的光纤传感器嵌入火花塞金属外壳的小切口中。首先,将传感元件浸入液态金中并固化。然后,将镀金的光纤传感器镀上铜。最后,将金属涂层的光纤传感器嵌入火花塞中。使用信号调节单元监控嵌入火花塞的FFPI传感器。现场测试是在3缸汽车发动机中进行的,其中压电压力传感器作为参考传感器的转速高达3500 rpm。光纤传感器数据通常与压电参考传感器测量的数据匹配。研究了使用垂直腔表面发射激光(VCSEL)二极管作为FFPI光学传感器系统中的光源。来自FFPI传感元件的反射光用于测量光程差。在腔长为12mm的Fiber Fabry-Perot干涉仪中,使用1550nm VCSEL作为光源,检查了光谱特性,以确定直流偏置电流,调制电流幅度和调制频率的适当组合。单个VCSEL操作和规则的条纹图案得以实现。激光调谐为-41.2 GHz / mA,由VCSEL二极管输出的频谱峰值随直流偏置电流的变化的测量确定。通过测试在加热FFPI传感器时的条纹运动,光学长度的温度调谐系数确定为11 x 10-6°C;这些实验的结果表明,使用VCSEL二极管作为FFPI传感器的光源,可以替代使用分布式反馈(DFB)激光二极管在较低的偏置电流和调制电流振幅下进行监视。
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