Research On Fiber Optic Strain Sensor Based On Mach-Zehnder Interference Structures

As a kind of reinforced concrete structure,the safety monitoring of the bridge building during construction and service is very important.It is the main link to avoid production accidents in advance to find hidden damage hazards in the bridge building in time.The traditional monitoring methods are mostly the regular inspection and maintenance of manpower,relying on the judgment of human experience,it is difficult to achieve timely,rapid and efficient monitoring of various damages to the bridge.It is easy to use traditional electromagnetic sensors for the detection of bridge construction due to electromagnetic interference,it is susceptible to the impact of the harsh environment and leads to shortcomings such as short service life,which is limited in practical use.The optical fiber sensing technology overcomes these disadvantages of the traditional electromagnetic sensors,and its superior performance is being increasingly applied to bridge building safety monitoring.Therefore,how to apply optical fiber sensing technology effectively to the safety inspection of bridge buildings is a subject worthy of in-depth study.This paper introduces the structure and basic principles of optical fiber strain and strain sensors based on the safety monitoring of bridge buildings,designs and fabricates a new type of optical fiber strain sensors,tests the performance of the sensors,and obtains some experimental results with reference value.The main research contents are as follows:(1)Based on the principle of Mach-Zehnder interference,an all-fiber strain sensor based on hollow fiber was designed and fabricated,and the strain experiment was performed on it.The experimental results show that the sensor achieved a strain sensitivity of-1.8 pm/??in the measurement range of 0 ?? to 2000 ?? and a temperature sensitivity in the temperature measurement range 0f 20 ? to 80 ? is 1.6 pm/?.The sensor has relatively high sensitivity,simple structure,low cost and reliable performance,and has certain practical value.(2)Proposed and adopted a new method of taper operation to fabricate an all-fiber strain sensor.The experimental test of the sensor showed that the strain sensitivity of this sensor in the strain measurement range of 0 ?? ~ 2100 ?? reaches-2.7 pm/??,which is 1.5 times that of the all fiber MZI strain sensors without the tapered area and the temperature sensitivity in the temperature measurement range of 20? to 80? is 1.6 pm/?.The sensor has simple structure,high sensitivity,good stability and repeatability,realized the simultaneous measurement of temperature and strain,has certain application value in the safety monitoring of bridge buildings.