A New Method to Design Trifurcated Optical Fiber Displacement Sensors

Trifurcated optical fiber displacement sensors (OFDSs) are increasingly used in industrial and aerospace applications. The critical element of the sensor is the fiber bundle. However, there is no straightforward method to calculate it from the working specifications of the sensor, the number of fibers needed, their size, and arrangement. This work presents a simple yet accurate method to design trifurcated OFDSs. The proposed method allows to derive the geometrical arrangement and size of the fibers from three simple equations, thus reducing significantly the difficulty and complexity of the OFDS design. Those three equations depend on the working point, working range, required sensitivity, and maximum size of the bundle. In this way, the proposed method will save valuable time for researchers and engineers who wish to design, fabricate, and use this type of OFDSs. The procedure is explained in detail with two examples. The results predicted by the model are compared with the experimental results of a bundle with identical fiber arrangement and dimensions. The results show good agreement with a deviation of less than 1% in the working range of the sensor.