The invention discloses a polarization-maintaining
fiber coupler. A
coupling region of the polarization-maintaining
fiber coupler is made of single-mode optical fibers, an input end of the polarization-maintaining
fiber coupler at least contains a polarization-maintaining
optical fiber, an output end which is directly communicated with the input end is one single-mode
optical fiber, the input end of the polarization-maintaining
fiber coupler at least contains one single-mode
optical fiber, an output end which is directly communicated with the input end is the polarization-maintaining optical fiber, and the polarization-maintaining optical fibers of the input end and the output end are fused with the corresponding single-mode optical fibers in the
coupling region respectively. A method for preparing the polarization-maintaining
fiber coupler comprises the following steps that: firstly, a
heat sealer is used to prepare two-node optical fibers; secondly, the optical fibers are arranged and axially positioned according to the design requirement; and finally, a plurality of the single-mode optical fibers in the middle are fused and drawn into the
coupling region. In the polarization-maintaining
fiber coupler, the coupling region is formed by drawing the single-mode optical fibers, so a device has the characteristics of no sensitivity to the polarization and temperature environment, and the stability and the reliability of the device are greatly improved. The invention also discloses an all-fiber optical
current sensor.