“…This is likely due to the fact that typical ST forces are in the 10 −3 N range, i.e., much too small to be detectable by optical fiber force sensors with a Young's modulus above 70 GPa (for silica fibers) [11][12][13]. A possible method to overcome this drawback would be to reduce the fiber diameter to increase the force sensitivity, such as in microfiber Bragg gratings [14][15][16] and microfiber-based asymmetrical Fabry-Perot interferometers [17]. However, one problem is that reducing the fiber diameter makes the sensors easy to break; another problem is that such force sensors [14][15][16][17] are not designed to measure lateral forces, but rather axial ones.…”