Investigation On Optical Fiber Sensor Fabricated By Femtosecond Laser

Sensors play an important role in modern information technology, while opticalfiber sensor has a unique advantage for its small volume, high sensitivity and lesssusceptible to electromagnetic perturbation. The refractive index, which has closeconnection with material's concentration and PH value, will show some significantphysical and chemical property of the substance. Temperature is also the first factor tobe taken into consideration at many conditions. So it will be of great importance tostudy a high sensitive optical fiber sensor and use it to detect the refractive index andtemperature.Compared with traditional optical fiber evanescent field sensor, D-shaped opticalfiber evanescent field sensor has higher sensitivity and stronger mechanical strength.Single-D-shaped optical fiber and multi-D-shaped optical fiber were constructed withfemtosecond laser pluses, respectively. The relationship between the transmissionefficiency and the refractive index of the solution was simulated by Beamprop software.In the experiment, different solutions with various refractive index was tested by thefiber sensor, and the ratio of the output light power was also recorded with the resultshow better performance than traditional abelrefractometer. For the refractive index ofolive oil and glycerin will have linear decrease as result of its temperature increase,we package the olive oil with single-D-shaped fiber sensor and package glycerin withmulti-D-shaped fiber, respectively, to make two new temperature sensors, and the detectresult of their application depicts high sensitivity.The rectangular grooves on the cladding was carved by femtosecond laser, etchedby hydrofluoric acid. So we can have a guide model-radiation model sensor, theresonant wavelength of this grating will have susceptive shift with the change of theexternal solution's refractive index. This type of sensor also has good sensitivity.The advantage of the use of femtosecond is that it has high precision, highefficiency, less extra damage, easy to control and suitable for monitoring, which is muchbetter than traditional mechanical polish.The result of the experiment has good conform with the theoretical simulation. Sothese three fiber sensors have a bright application prospect.