Simultaneous measurement for multi-parameters and avoiding the cross interference of the external environment temperature based on the fiber sensor has been widely investigated in recent years due to its intrinsic advantages, such as compact size, light weight and immune to electro-magnetic interference, etc. Compared with the traditional technology, the fiber sensor always needs to cascade with other optical device or additional interferometer. Thus, the fabrication and size of the fiber structure is relatively complex. Moreover, the cross impact exists in multi-parameters measurement. One of the most common ways is the crossing matrix method, but it also has the cross interference and is difficult to distinguish the multi-parameters, leading to the accuracy of the measurands sharply decline.
Professor Ping Lu of the Wuhan National Laboratory for Optoelectronics (WNLO) proposed a novel fiber curvature sensor without temperature cross interference based on a single hole twin eccentric core has been proposed. A section of single hole twin eccentric core fiberwith the length of 2.6mm is fusion spliced between two single mode fibers (SMFs). Anti-resonant mechanism combined with inline Mach-Zehnder interference (MZI) structure are applied to the measurands detection. The spectrum is composed of a comb spectrum caused by the inline MZI and several dominant resonant wavelengths induced by anti-resonant effect. The curvature sensitivity of -1.54dB/m-1 can be achieved by intensity demodulation of the selected dip of Gaussian fitting. Similarly, the temperature sensitivity of 70.71pm/℃ and 34.17pm/℃ are respectively achieved by tracking coherent decrease point obtained by the FFT band pass filter method and Gaussian fit dip. Consequently, a relatively higher resolution of temperature measurement can be realized by the two methods mentioned above. The proposed sensor has a great potential for engineering applications due to its compact structure, easy fabrication and without cross impacts.
This work has been published in Optics Express Vol.25, No.11, 12372-12380 (2017) in 17, May, titled "Single hole twin eccentric core fiber sensor based on anti-resonant effect combined with inline Mach-Zehnder interferometer ". This work was supported by the National Natural Science Foundation of China under Grant 61275083 and Grant 61290315.