Highly Sensitive FBG based Tilt Sensor Using PM-IM Conversion and EFD Interrogation Technique

Tilt sensors are essential measurement devices to identify the degree of deviation from the reference plane. They are extensively employed in underground drilling, level determination for instrumentation and mechanical guiding, geophysical observation, biomedical research etc. Fiber Bragg Gratings (FBG) based inclinometers have marked their presence due to their superior performance and ability to work under harsh conditions than their electronic counterparts as well as other fiber optic sensors. FBG based inclinometers require optical spectrum analyzers and interrogators for observing wavelength encoded data. Due to limited resolution of these equipment, it is difficult to develop an inclinometer with very high sensitivity and resolution. Hence, an interrogation technique that utilizes edge filter detection and phase modulation to intensity modulation (PM-IM) conversion phenomena is used to develop an inclinometer with higher sensitivity and accuracy. A detailed theoretical discussion along with its experimental validation is conducted in this manuscript. The proposed system is simple in design and easy to implement, with a very high resolution of 0.00072° and an accuracy of 0.083°. The results have shown a high degree of linearity in a particular sensing range with good repeatability, making the system a reliable candidate for industrial applications.