A Review of Fiber-Optic Modal Modulated Sensors: Specklegram and Modal Power Distribution Sensing

In this paper, a review of fiber-optic modal modulated specklegram and modal power distribution sensors is presented first time in the literature. Few researches have been conducted about these modal-modulated approaches in comparison with the other fiber-optic sensing techniques. This paper reports on the past, present, and future scope of modal modulated fiber-optic specklegram and modal power distribution sensors. A detailed overview of the theory and definition of specklegram and modal power distribution sensors have been provided in this paper. Different signal processing techniques, models, and sensor hardware specifications have been introduced and discussed in detail. This is followed by a review of the various applications reported about these sensors. The content of this paper would be important and benefical for the fiber-optic sensor research community especially focused on modal modulated approaches.