Research On All-fiber Orientation-dependent Tilt Sensors

Optcial fiber sensors are becoming more and more popular in many fields because of that optical fiber sensors have many advantages such as non-sensitive to electronic disturbance, low cost and compact structure,these fields include health monitoring of large buildings, oil drilling and precision measuring instruments. Optical-fiber tilt sensors mostly based on couple principle and detect changes based on the fiber gratings’ resonance wavelength’s move, as a result, the sensitivity of this kind of sensor is not high enough. Due to this situation, we proposed three kinds of tilt sensor with high sensitivity based on interference, including fiber tilt sensor based on Michelson, MZI tilt sensors based on taper-offset and LPFG-offset. In this paper, first of all, we analysis the sensing principle of the orientation-dependent tilt sensor with high sensitivity; secondly, we simulated the sensors’ structure to get the best parameters by using the BPM software; at the last, we made these three sensors based on parameters we got. The result corresponds to our expectation. The main contents as flows:① We designed a Michelson tilt sensor with compact structure and easy to fabricate. We fused two SMF with an offset manually. We tested the sensor while analysis the sensor. The result shows that this tilt sensor has a very high sensitivity of 2.346nm/o in a range of ±3o and this sensor is orientation-dependent.② We designed a MZI tilt sensor based on taper-offset with compact structure and easy to fabricate. We tapered the SMF by using fusion splicer and fused two SMF manually to make the offset. The experiment result shows that tilt sensor based on Michelson interferometer has a high sensitivity of 1.154nm/o in a good range of ±5o and the sensor is also orientation-dependent.③ We designed a MZI tilt sensor based on taper-offset with compact structure and easy to fabricate based on the second sensor. We made the LPFG by using CO2 laser and fused the SMF manually to make the offset. The experiment result shows that this sensor has a high sensitivity of 0.935nm/o in a range of ±3o and also directional.By tested these three sensors experimentally, the results correspond to our expectation: orientation-dependent, high sensitivity, compact structure, low-cost. These advantages make this kind of sensor is very important at some special fields, such as: oil drilling etc. Although these three sensors have unique advantages, they still have some shortage: the measurement range. The range affects the application of the sensor a lot. At our next plan, we should design orientation-dependent tilt sensor with high sensitivity, at the same time,with good measurement range.