Temperature and vibration OTDR measurements with a single mode-multimode-single mode fiber structure

We suggest a prototype of a fiber-optic sensor system that is based on a simple singlemode-multimode-singlemode fiber structure and serial OTDR. The sensor has simple structure, made of affordable components, exploits easy measuring principle, immunes to EMI or RFI, and has confident response to measure key environment variables at a very long span. From the experimental results, the relationship between the temperature of water and output signal of the temperature sensor can be determined. After some maths, we can determine the temperature of the water by measuring the optical power loss of the at the SMS structure in a temperature range of 30 to 70 °C. This SMS structure is shown to carry out vibration measurement for 0.1-60 Hz frequencies with high accuracy. The OTDR exploited allows carrying out far-field measurements when SMS structure is spliced in long fiber-optic link.