Design of a Mach-Zehnder Interferometric Fiber Sensing System Based on PCA-Assisted OAM Interrogation for Simultaneous Measurement of Refractive Index and Temperature

We propose and numerically design a Mach-Zehnder interferometric sensing system using principal-component-analysis-based orbital angular momentum (OAM) interrogation for simultaneous measurement of refractive index (RI) and temperature. A capillary-assisted Mach-Zehnder interferometer (CAMZI) encapsulated into a microfluidic channel serves as the sensor probe, which is introduced in the Gaussian interference arm of the sensing system. Temperature-sensitive liquid and RI sample are respectively loaded inside and outside the silica capillary to discriminate the cross sensitivity between refractive and temperature. As the output light of the CAMZI carrying intensity and phase information in response to the variations in RI and temperature interferes with the OAM beam, the intensity and rotation angle of the spiral interferogram would change accordingly. And by performing principal component analysis (PCA) on these interference patterns, RI and temperature variations could be retrieved. The proposed sensing system based on PCA-assisted OAM interrogation is anticipated to resolve cross-sensitivity for dual-parameter sensing, and moreover it paves new way toward developing OAM-related photonic devices.