Long modal interference in multimode fiber and its application in vital signs monitoring

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

“…Since the effective components of the heartbeat signal with an HR of 50-110 bpm were mainly concentrated in the range of 0.8-1.8 Hz, a zero-phase bandpass filter with a frequency of 0.8-1.8 Hz was used for the recovery, as shown in Figure 7c. More importantly, different from the other type of RR and HR optical fiber sensors [7,12,19,21], owing to the combined advantages of the high bending sensitivity of the SHMF-MZI and the optimized designation of the microbending deformer, the amplitude of the extracted HR signal was comparable with that of the extracted RR.…”

“…This included meticulous daily measurements on two volunteers, conducted over a period of five consecutive days. In order to evaluate the accuracy of the wearable SHMF-MZI microbend sensor, a commercial device called Oxygen Saturation (SpO2) sensor was selected for the simultaneous measurement of HR [7], and the RR measurement results were compared with the manual counting method. The respiratory and heartbeat signals of 10 volunteers (5 males and 5 females) were collected in the experiments; all of them did not have any cardiac diseases or take any hormonal drugs prior to the test.…”

“…In the past, many sensors for measuring human RR and HR have been proposed, including piezoelectric-based sensors [5], electromagnetic wave scanning [6], fiber optic sensors [7][8][9][10][11], etc. Among them, fiber optic sensors have attracted the attention of many researchers due to the advantages of high sensitivity, anti-electromagnetic interference, and lightweight.…”

“…The key distinction between the two lies in the fact that the BCG signal exhibits a greater number of characteristic peaks within a single heartbeat cycle, accompanied by a relatively low signal intensity. Most of the usually used schemes was to embed optical fiber sensors into a mattress to monitor the RR and HR of a human lying on the bed [7][8][9][10][11][12][13][14][15][16][17][18]; however, it would require a relatively large sensing area, thus leading to the sensing optical fiber being too long. Another way was to embed the designed optical fiber sensors in a belt to construct a wearable device [19] that was capable of monitoring RR and HR even when the subject was standing or moving.…”

Vital Sign Monitoring in Car Seats Based on Electrocardiography, Ballistocardiography and Seismocardiography: A Review

“…Vital sign monitoring plays a crucial role in both prevention and diagnosis of various health problems [ 135 , 136 ]. As more and more people pay attention to their health condition, various measurement systems are developed, in particular, following the so-called “wearable” concept.…”