In this paper, a novel method for multiplexing a large number of fiber-optic Fizeau sensors using coarse wavelength division multiplexing (CWDM) and spatial-frequency division multiplexing (SFDM) is proposed and demonstrated. A CWDM device is used to multiplex signals from different sensor channels occupying different wavelength regions divided by the CWDM. More than 10 Fizeau sensors arranged in a single channel can be multiplexed by using SFDM due to the long cavity length of the Fizeau sensor. The experimental results show that a strain accuracy of ±5με is achieved. As up to 100 sensors can be multiplexed simultaneously, this approach can improve the multiplexing capacity of Fizeau strain sensors significantly.
A novel method for multiplexing fiber-optic Fizeau strain sensors with optical amplification is proposed and demonstrated. This method overcomes the two intrinsic disadvantages of fiber-optic Fabry-Perot (F-P) strain sensors, i.e. weak signal and difficult multiplexing. The amplified spontaneous emission (ASE) and optical amplification of an Erbium-doped fiber (EDF) pumped by a 980nm laser diode are used simultaneously to enhance the interferometric signal considerably. A Fizeau interferometer formed by two fiber ends with a quite different reflectivity is used to replace the F-P cavity in sensor head design. Such a Fizeau cavity can enlarge the cavity length by at least an order of magnitude and allows more than ten sensors to be multiplexed simultaneously by using spatial-frequency multiplexing. The operating principle of the sensor system is discussed and an experiment is carried out to verify the concept of the method proposed. It is anticipated that such a sensor system could find important applications for health monitoring of large structures.
In this paper, a novel method for multiplexing extrinsic fiber Fabry-Perot interferometric sensors (EFPIs) using the coarse wavelength-division-multiplexing technology (CWDM) is proposed and demonstrated, for the first time to our knowledge. The system and principle for sensing and multiplexing are described. A 1×4 CWDM is used to multiplex signals from four EFPIs with identical cavity length. The experimental results show that a strain accuracy of 2.5me is achieved. There is little cross-talk between adjacent sensor channels. This system improves the multiplexing capability of EFPIs by a factor of four. It is anticipated that such a sensor system could find important applications in smart materials and health monitoring for large structures.