Optical Strain Sensors
Industrial-Grade Strain-Sensing Technology Based on Optical Phase Interrogation (OPI)
A strain sensing solution based on polymer optical fibers (POF) provides designers with a low-cost sensing solution that is lightweight, immune to electromagnetic interference (EMI) and electromagnetic susceptibility (EMS), and does not require electrical current at the sensing point.
Avago Technologies has developed a unique, cost-effective POF based strain sensor solution utilizing a patented optical phase interrogation (OPI) technique. It enables readily available POF to be used as a high-precision strain sensor on par with current fiber Bragg grating (FBG) based strain sensors for a broad range of applications including wind-blade load management in wind turbines and structural health monitoring in a variety of other structures.
Strain Sensor Principle
To perform the strain sensing, light going through the plastic fiber is split into two equal paths; one path coupled to a polymer optical fiber that is subjected to strain and the second coupled to an unstrained reference fiber. The correlation of strain and phase change between the two optical signals provides a phase differential that can be translated into the amount of strain.
There are multiple approaches to measuring strain or vibration of strain. Strain Gauge and Accelerometer solutions require that power be brought to the sensor, which limits where the sensors can be applied. Optical strain measurement systems, such as Fiber Bragg Gratings (FBG), have been commercially available for a number of years, but Bragg based solutions are significantly more expensive and complex to install.