A vibration-sensing system based on SMS fiber structure

• A vibration sensor based on single-mode multimode single-mode fiber structure was demonstrated.
• Preliminary experimental results verified the proposed idea.
• Vibration frequency measurement error of ±0.5 Hz was obtained.
• Measurement range was from 2 Hz to 80 Hz.

A vibration-sensing system which is based on single-mode multimode single-mode (SMS) fiber structure was demonstrated in this paper. When the light is coupled from the lead-in single-mode fiber (SMF) into the multimode fiber (MMF), high-order Eigen modes of the MMF are excited and the interference between different modes occurs while the light propagates along the MMF. The interference results will be changed because the vibration signals are acted on the sensing MMF. Theoretical analysis was carried out, then preliminary experimental results verified the proposed idea. Vibration frequency measurement error of 2% as obtained within the range from 2 Hz to 80 Hz by using a lock-in amplifier as the signal detection method.