Controllable mode emission from all-fiber laser based on polarization rotation technology and its application in bending sensing

We demonstrate a simple and compact all-fiber structure that can generate tunable fiber modes, including LP01, LP11 and OAM modes. The offset splicing between a single-mode fiber (SMF) and a multi-mode fiber (MMF) is used to excite LP11 mode in the MMF from LP01 mode in the SMF. The polarization controller (PC) is used to control the incident angle of the LP11 mode from the MMF into the polarization-maintaining fiber (PMF). The LP11 mode and OAM(+1)/OAM(- 1) mode can be generated at a specific incident angle (45 degrees /135 degrees) in the experiment. In addition, the designed laser has been used to detect the fiber bending degrees. It is found experimentally that the changes in the strength of the two lobes of the output LP11 mode have good linearity in the range of bending diameters from 15 to 35 mm.

Automated summary

We present a simple and compact all-fiber structure for generating tunable fiber modes, including LP01, LP11, and OAM modes. By offset splicing a single-mode fiber (SMF) and a multi-mode fiber (MMF), the LP01 mode in the SMF can be excited into the LP11 mode in the MMF. A polarization controller (PC) is utilized to control the incident angle of the LP11 mode from the MMF into a polarization-maintaining fiber (PMF). In the experiment, the LP11 mode and OAM (+1)/OAM (-1) mode can be generated at specific incident angles (45 degrees /135 degrees). Additionally, the designed laser has been utilized for detecting the bending degrees of the fiber, showing good linearity in the changes of the two lobes' strengths of the output LP11 mode within the range of bending diameters from 15 to 35 mm.