“…Dan Su et al [ 9 ] proposed a measurement scheme for dual-parameter measurements using a double-fiber grating written by a single-mode fiber and a thin-core fiber. Furthermore, there are several other approaches such as polarization-maintaining few-mode Bragg gratings [ 10 ], sawtooth stressor-assisted highly birefringent FBG [ 11 ], cascaded long-period fiber grating or Bragg grating [ 12 , 13 ], multimode fiber chirped long-period grating [ 14 ], superstructure FBG [ 15 ], misaligning splicing a thin core fiber between two SMFs [ 16 ], combining few-mode fiber and FBG [ 17 , 18 ], combining FBG and multimode fiber [ 19 ], tilted FBG [ 20 ], specially packaged FBG [ 21 ], π-phase-shifted FBG [ 22 ], and a combination of different types of interferometers and FBG [ 23 , 24 , 25 , 26 ]. However, there are some flaws such as relatively high complexity, difficult fabrication process, or low sensitivity in some of those approaches, which restrict their practical applications.…”