Controlling force in polarization-maintaining fiber fused biconical tapering

Fused biconical tapering (FBT) is an important method of manufacturing polarization-maintaining fiber (PMF) couplers. However, the tension on the ends of the fibers can affect the performance of the coupler. In this paper, a computer-based method of controlling the drawing force was presented. The system includes a drawing mechanism, rotary position encoders, and a control circuit. A three-dimensional model of a permanent magnet and a coil is constructed, and the relationship among the coil current, rotation angle of the clamp, and electromagnetic force is determined using finite element simulations. Electromagnetic force control based on these simulations can be realized. The method is verified experimentally, and it is shown that a drawing force of 0-1.8 gf can be achieved with an error of within 3.04%. This result can be used in the FBT-based manufacture of fiber components such as fiber couplers and gratings.