Study of fiber-optic coupler’s strain characteristic based on variational theory

According to the characteristics of fiber coupler, the ratio of single-mode fiber-optic couplerpsilas output power is sensitive to the length of coupling zone. The mode coupling mechanism of fused biconical taper is described in detail. The characteristic of fiber-optic coupler is studied by using spiral micrometer which could avoids the disturbance of cantilever self-weight and self-vibration and enhance the measurement precision effectively. The results indicate that the fused biconical taper coupler is sensitive to strain and the function changed monotone and linear. Meanwhile, it is temperature stability and anti-disturbance transversely. The fused biconical taper coupler is a prospective optical fiber strain sensor.