A bio-signal monitoring sensor based on the microbending effect of fiber

Abstract

In this paper, the focus of the study is the bio-signal monitoring sensor based on microbending effects and bending loss in fiber, the physical natures of the microbending effects and bending loss of multimode fiber are expounded through the microbending principle of fiber, and the effect of displacement on the microbending loss of fiber is explored and analyzed by deriving the microbending loss formula under the optical fiber theory. After putting the sensor on the back of a chair and letting the subject sit on the chair with the back on the sensor, the degree of microbend or radius of the fiber change as the change in chest volume during breathing results in the change in the external force, i.e., the force applied to the sensing part of the fiber. The physical change in the fiber induce changes in the amount of light energy transmitted in the fiber, causing optical loss. The respiratory rate is obtained by measuring the optical loss. The results show that the waveform displayed on the computer has good traceability performance, on which the frequencies of respiratory signals including normal breath, deep breath, and rapid breath can be distinguished. Experiments show that the sensor has good traceability feature and can automatically recognize the breathing conditions, with a signal-to-noise ratio of over 28dB

A Wearable Sandwich Heterostructure Multimode Fiber Optic Microbend Sensor for Vital Signal Monitoring

“…When Λ satisfies Equation ( 4), the transmission mode of the SHMF-MZI sensor reaches full coupling, and the microbend loss and sensitivity reach the maximum. Moreover, the sensitivity of the fiber optic microbend sensor increases with the number of microbend N [25,26]. Therefore, it is anticipated that the sensing region of the fiber optic sensor, which is the GIMMF, is fully covered by the microbend deformer.…”

“…In order to precisely extract the HR signal from the time domain mixed signal of HR and RR, it is also expected that the wearable sensor has a similar sensitivity to both of them. Since most of the RR and HR optical fiber sensors are based on the principle of sensing the pressure or bending induced by respiration and heartbeat, microbending is usually utilized to increase the pressure or strain sensitivity of the optical fiber [23,24], including the mattress type [14][15][16]25,26] and the wearable belt type [19].…”