Biological sensors based on long period fiber grating

Abstract

Nowadays, there have been extensive applications of biosensors for industrial production, environment monitoring, disease diagnosis, and food safety. Attributed to periodically refractive index modulation, long period fiber grating (LPFG) can couple the core mode to forward propagating cladding modes at specific wavelengths, so it is sensitive to the variations of environmental refractive index. In addition, LPFG sensors have been ubiquitous in the biological detecting field with advantages of high sensitivity, compact structure, resistance to electromagnetic interference, and long-distance monitoring. In this paper, we focus on the review of sensing mechanisms, signal demodulation, fabrication and origin and recent development of biosensors based on LPFG. Besides, we discuss the methods for improving detection limits such as reducing cladding diameter, working near dispersion turning point (DTP), and within mode transition (MT) region. Applications on the detection of glucose, bacteria, immunoglobulins, biotin, DNA, hemoglobin, virus, drugs and so on are also classified and summarized in detail. Finally, several problems that hinder the practical use of LPFG biosensors are presented and some possible solutions are proposed, and the future development of biosensors is conceived. Over the past few years, biosensors based on LPFG have made remarkable achievements in the diversification of detected objects and improvement of extreme sensitivity. However, there are still some problems in practical applications for LPFG biosensors, such as temperature cross-sensitivity and stable wavelength demodulation, which need to be solved in the future.