A ring core fiber sensor based on Mach-Zehnder interferometer for lateral pressure sensing

In this work, we proposed a ring core fiber (RCF) based all-fiber sensor used for lateral pressure sensing. The sensor is composed of 1-mm coreless fiber (CLF) and 2.5-cm RCF. Then the CL-RC fiber structure is connected to two segments of single-mode fibers (SMFs) to form a Mach-Zehnder interferometer (MZI). One of the SMFs serves as the lead-in fiber which is linked with a broadband laser source (BBS) and the other SMF is connected to the optical spectrum analyzer (OSA) for signal recording. The transmission spectrum of the MZI structure has a large extinction ratio (ER) of up to 20 dB with the free spectral range (FSR) of 9.3 nm. After the fabrication, the MZI sensor is packaged for pressure sensing at room temperature (25 ℃). The weights with different values are applied on the fiber sensor so that the intensities of pressure can be calculated and adjusted. The lateral pressure intensity is tuned from around 1.6 MPa to 9.6 MPa. With the increase of pressure intensity, the spectra of output signals show a linear redshift. The pressure sensitivity of the proposed MZI sensor reaches 607 pm/MPa with good linearity of 0.9839. The proposed pressure sensor formed by RCF has many advantages, such as easy fabrication, low cost, small size, electromagnetic resistance and good sensitivity, which can be potentially applied to diverse fields.