# SARS-CoV-2 Detection Using Optical Fiber Based Sensor Method
## 1 Introduction
There are tests that can be used to see if someone has been infected with SARS-CoV-2: detection of viral nucleic acid and antigen (acute infection) and detection of antiviral antibodies (pre-infection). Even though there is a global debate about the use and misuse of antibody-detection tests, new tests with high sensitivity, specificity and low-cost technology are needed. As a result, postulating the invention of devices based on optical fibers is appropriate, and they may help manage this and upcoming pandemics with fewer negative consequences for society. The general structure of a biosensor is made up of three distinct components: the substrate, biolayer and immobilization interface. The optical biosensor is a transducer in which the specimen under test interacts with the light that is passed or interacts with an optical fiber to produce a modulated optical signal with information related to the parameter being measured, which means fiber interacts with an external parameter and carries the modulated light signal from the source to the detector. From this modulated optical signal, the input measurement data may be retrieved. A wide range of immobilization techniques have been developed and employed for biosensing applications in recent decades. Fiber Bragg Gratings (FBG) [9], Long-Period Fiber Gratings (LPFG) [10], Surface Plasmon Resonance (SPR) [11], Lossy Mode Resonance (LMR) [12] and a broad range of interferometers [13] were shown to be viable for use as biosensors, with tapered fibers [14] and multimode fibers [13]. To the best of the authors' knowledge, a novel plastic optical fiber sensor U-shaped probe-sensing method is presented and envisaged for detection of SARS-CoV-2 virus, and has the capability to detect new variants such as Omicron. The novelties of this article are as follows:  
1. The U-shaped fiber-optic probe is realized from plastic optical fiber (POF) for two different diameters: 200 and 400 microns, respectively. 2. The test specimens are suggested to be taken from both oropharyngeal and nasopharyngeal tracts, as a sensing approach based on intensity modulation appears to be very cost effective with minimal logistics. 3. The envisaged prototype with its component analysis is shown, making it clear that the design of this prototype is simple and does not require any special training. 4. The results are shown in terms of intensity and relative intensity followed by comparison of the COVID-19 positive specimen with the proposed method and conventional PCR test method. 5. A validation of the method proposed is shown that confirms the accuracy of the proposed technique. In order to validate the proposed technique, it is important to verify that the proposed technique detects SARS-CoV-2 and not something random. In this research, the sample consisted of COVID-19 patients who presented to the hospital with respiratory symptoms. 6. A statistical analysis for the gathered data is presented to understand the cycle or map that is followed for COVID-19 detection in the hospital compared to the cycle of actions required in proposed detection. Moreover, Section 2 presents in detail the emergence and features of COVID-19 that make it easier to understand the life cycle of COVID-19. Section 3 summarizes the main work employed for detection of COVID-19. Section 4 presents the U-shaped fiber-optic sensor methodology while Section 5 explains the Experimental testbed utilized for the work, followed by Section 6 highlighting the theoretical understanding behind the wavelength-bending radius and wavelength refractive index relationship. Section 7 presents the results while Section 8 presents the validation technique where comparisons of proposed and other techniques are compared. Section 9 compares the statistical analysis of the samples. Section 10 explains the future research direction and Section 11 concludes the paper.