Potential of hybrid gold nanoparticles/graphene oxide (AuNPs/GO) coated single mode fiber (SMF) sensor by exploiting localized surface plasmon resonance (LSPR) effect for Musta’mal water identification was studied. Three structure shapes of fiber optics such as straightshape, loop-shape and u-shape had been prepared. Three layers of AuNPs with 50 nm in diameter were drop-casted onto the partially unclad polished single mode fiber (SMF) to observe the maximum sensitivity of LSPR. To enhance the LSPR effect, one layer of GO was deposited on top of the AuNPs layer. Two optical light sources with least attenuation (1310 nm and 1550 nm) were employed to study the optical power output as the sensor immersed in different type of water samples. The u-shape SMF portrayed the maximum output power about 24.2 dBm at 1550 nm wavelength. According to the analysis, the deployment of 1550 nm laser wavelength resulted in better sensitivity with 23.2% improvement compared to 1310 nm wavelength. Apparently, the LSPR phenomenon created by AuNPs/GO able to enhance the plasmonic signal up to 51.9% than the uncoated SMF. The thinnest diameter of SMF’s cladding, d=0.1195 mm with U-shape structure exhibited the highest power different of 1.10 dBm, in which suggested the best sensing performance. In conclusion, the optimization of AuNPs/GO u-shape polished SMF resulted in the maximum sensitivity with value of S=72.7 dBm/RIU for Musta'mal water identification.

This work is carried out to study the effect of noble metal thicknesses, namely gold and silver on the SPR characteristics for smart food packaging technology applications. A Kretschmann prism coupling was introduced to excite surface plasmon polaritons (SPP). The optical refractive indices values of gold and silver were set as Rgold=0.1759+3.4104i and Rsilver=0.0585+4.2665i respectively. The thicknesses of noble metal thin films were varied between t=25nm and 95nm with the increment of 10nm for each reading. SPR signal analyses were performed by studying the characteristics of SPR peaks such as Q-factor and FWHM. Both analyses demonstrated an outstanding optical properties of silver at t=55nm in comparison with gold due to its low FWHM and high Q-factor values which proves its ability to generate excellent amount of SPP. The employment of silver witnessed the enhancement of Q-factor value up to 7.09% and the decrement of FWHM about 76.58%, relatively with gold. The introduction of silver able to convert 87.20% SPP, whilst the usage of gold only capable to excite 81.4% SPP. In conclusion, application of silver noble metal at t=55nm able to generate maximum SPR. This excellent criterion placed silver as a spectacular candidate in the development of low cost and high sensitive SPR sensor for food quality assessment applications.

Monolayer Au and hybrid Au/GO thin films with thicknesses of 50 nm and 52 nm sequentially, were deposited onto the glass substrate. The effect of laser intensities towards SPP excitation via Kretschmann coupling technique was investigated by varying laser intensities between 30 nW to 80 nW. Maximum SPR represented by the smallest value of Rmin =0.0838 a.u was obtained as 80 nW of laser intensity had incident onto the hybrid films. The deployment of 52 nm Au/GO resulted excellent SPR properties indicated by the greatest Q-factor=0.7668 a.u with percentage difference about 22.24 % in comparison with 50 nm monolayer Au thin film. The utilization of high intensity light demonstrated significant increment of Qfactor value, in which the SPR response was successfully amplified due to the maximum number of photons pumped by the laser.

A hybrid U-shaped-microbend fiber optic evanescent wave sensor was developed by combining two types of bending structures on the optical communication single mode optical fiber (SMF28). To study the effect optical microbending on the output power, corrugated plates consisted of cylindrical structured surface with various distance between the glass rods of 6 cm, 12 cm and 18 cm were constructed. The macrobending effect was introduced by bending the SMF into two shapes, namely U-shaped and Sshaped. The bare SMF with various bending designs were immersed into numerous water sources from Sg. Simin, Sg. Batang Benar and Sg. Klang. The output demonstrated that Sg. Simin was the most polluted river, followed by Sg. Klang and Sg. Batang Benar using U-shaped microbend SMF with distance between glass rod of 6cm and 1310 nm laser source. This result showed an excellent agreement with water quality index (WQI) data released by the Department of Environment (DOE), Malaysia. Maximum optical output power was obtained by using Sg. Simin’s water sample due to better light absorption from the evanescent waves by the pollutant particles, that avoided light leakage in comparison with less polluted water sources. The optimum sensing performance was successfully resulted by using U-shaped SMF due to its durability and uniform evanescent waves radiated from the cladding. In conclusion, the hybrid U-shaped-microbend SMF sensor based on evanescent waves propagation portrays an excellent potential to detect water pollution by monitoring the presence of pollutants around the fiber.

This study investigates the effect gold nanoparticles (Au)/graphene oxide (GO) coated fibre optics with various number of loop ring in identifying recycled cooking oil based on their frying time. Various layers of gold nanoparticles (AuNP) suspension were deposited onto the substrate via drop casting technique. Few material characterizations were performed such as Fourier Transform Infrared (FTIR) spectroscopy, Ultraviolet Visible (UV-Vis) spectroscopy and refractometer analysis. Three macrobending structures of Au/GO coated fiber optic’s loop ring such as single, double and triple loops with diameter of 1.5cm were formed to generate large area of evanescent field around the fibre and to excite surface plasmon polaritons due to the interaction between AuNPs and analytes. Cooking oil samples with different frying time such as 14 minutes, 28 minutes and 42 minutes were prepared as analytes. The FTIR analysis revealed some changes in the transmittance percent of some bands as well as some slight shifts in the exact position of the bands due to the different of fatty acid composition. As the Au/GO coated fibre optics were immersed into the samples, the penetration depths were obtained as 142.75nm and 168.91nm at operating wavelengths of λ=1310nm and λ=1550nm, respectively. By using 1550nm operating wavelength due to its greater penetration depth than 1310nm, triple loop rings fibre optics coated with two layers of AuNP and one layer of GO exhibits a linear consistency with maximum sensitivity up to 69.17% due to the formation of large evanescent field around the loop area and intense SPP excitation

This paper reports the effect of microbending losses in single mode optical fiber for pressure sensing system application. Several types of periodical corrugated plates were fabricated, namely cylindrical-structured surface (Plate A) and rectangular-structured surface (Plate B) with thicknesses of corrugated parts were varied at 0.1 cm, 0.2 cm and 0.3 cm. Laser sources with excitation wavelengths of 1= 1310 nm and 2= 1550 nm were launched at the first end of the fiber. The values of losses were recorded by using an optical power meter. It was clearly seen that the microbending losses were polynomially increased with the increment of applied pressure and the thicknesses of corrugated parts of Plate A and Plate B. The maximum microbending losses of 1.5185 dBm/kPa was resulted as SMF was coupled with corrugated plates B with thicknesses of 0.3cm by using excitation wavelength of 1550nm. These values reduced to 0.7628 dBm/kPa and 0.4014 dBm/kPa as the thicknesses were decreased to 0.2cm and 0.1cm respectively. In comparison with a plain plate which acted as a reference indicator, the maximum percentage of microbending losses was obtained as 74.29 % for Plate A and 95.02 % for Plate B. In conclusions, we successfully proved the ability of SMF as a pressure sensor by manipulating the microbending losses experienced by the fiber. The employment of 1550nm of laser wavelength results better sensitivity sensor where the system able to detect large losses as the pressure applied on the corrugated surfaces.

For years, technologies in monitoring diseases and sickness for early stages detection have been actively developed. Previously, fiber Bragg Grating (FBG) has been widely used for strain, pressure and temperature sensing. Recently, this type of fiber optics has broadened its application in health monitoring field including cancer and various types of viruses’ detection. The combination of surface plasmon resonance (SPR) and propagating cladding modes created by FBG has proved able to enhance the strength of evanescent field in which consequentially increase the sensitivity of FBG sensor. This study reviews the utilization of plasmonic fiber Bragg Grating (FBG) in the health monitoring field in recent years by considering the types of FBG, plasmonic materials, metal deposition techniques and their current applications. In health monitoring application, plasmonic tilted FBG (TFBG) displayed impressive sensing ability resulted from the transmitted light coupling into backward cladding combine with the excitation of surface plasmon polaritons compared to the conventional FBG. These applications include cancer diagnosis, glucose detection, protein detection and respiratory problem. Gold with thicknesses between 30 nm and 50 nm is the most preferable noble metal to generate SPR due to its non-oxidized and chemically stable properties compared to other noble metals. Sputtering has become the most extensively used technique for metal film deposition on FBG because of its ability to create excellent film's adhesion and good thickness uniformity compared to dip coating and spin coating. In conclusion, FBG based SPR sensor technology exhibits bright potential for health monitoring applications due to its simple working procedure, high sensitivity and uncomplicated fabrication process.

A plastic optical fiber (POF) pH sensor is developed based on a sol-gel film. A sol-gel film was prepared by mixing tetramethyl orthosilicate (TMOS), trimethoxymethylsilane (MTMS), ethanol, distilled water and Neutral Red (NR) powder. Then, plastic optical fiber is coated by manually depositing the sol-gel film onto the tip of the POF. The sensing probe is dissolved into analytes with different pH levels, such as Coca-Cola (pH 3), tomato sauce (pH 4), black coffee (pH 5), tea (pH 6), distilled water (pH 7), soap (pH 8), baking soda (pH 9) and Clorox bleach(pH 10). The Refractive index will increase when the analytes are more acidic or more alkaline because they are concentrated with hydrogen and hydroxide ions at pH 3 and pH 10. The output power is varied based on the chemical reaction with the pH sol-gel film in the fiber-optic sensing probe. From the experimental results, it is concluded that the sensitivity of coated POF sensor, which is 0.0566 a.u/RIU, is higher than the sensitivity of the uncoated POF, which is 0.0429 a.u/RIU.

Exposure to harmful gases may cause health problems like bone marrow deficiency, which eventually drops the number of red blood cells, causing anemia and many other dangerous diseases. This work was carried out to study the potential development of a highly sensitive Kretschmann-based surface plasmon resonance (SPR) sensor for gas sensing applications using hybrid thin films of gold/titanium (Au/Ti). To optimize the excitation of surface plasmon polaritons (SPP), the light incident wavelength was varied from visible to infrared spectra. The thickness of Au thin film with a refractive index of n= 0.1758 + 3.4101k was fixed at 50 nm. Meanwhile, the thicknesses of Ti were controlled between 1 nm to 5 nm to optimize the SPR signal. Four different types of gas samples, such as benzene, methane, carbon monoxide, and carbon dioxide, were exposed to the sensor's surface. The proposed Au/Ti-based SPR sensor with thicknesses of Ti within 1 nm to 5 nm using visible and IR wavelengths able to detect various types of gaseous. Apparently, the deployment of infrared wavelength (λ=1550 nm) at Ti thickness of 3 nm resulted in the highest sensitivity up to 2412.06°/RIU and showed excellent selectivity to differentiate different types of gases. In conclusion, Au/Ti thin films are promising hybrid materials for gas sensing applications. Obviously, the sensor's sensitivity with total hybrid thin films of 53 nm was successfully enhanced as additional material, Ti, coated on the Au thin film's surface.

This study was carried out to investigate the effect of hybrid plasmonic material thicknesses, which are Ag/TiN and Ag/ZrN on the sensitivity of SPR sensor in detecting glucose and sucrose. A Krestchmann configuration of surface plasmon resonance (SPR) sensor had been theoretically developed via prism coupling technique. A 633nm of red laser was incident onto the prism’s hypothenuse side to excite the SPR. The effect of Ag/TiN and Ag/ZrN thicknesses ranging from 35nm to 60nm on the sensitivity of SPR sensor was studied. The deployment of Ag/ZrN at 44nm/10nm thicknesses resulted the resonance angle shifting about 0.91º from 44.67º to 45.58º as it was exposed to the glucose and sucrose. In contrary, the Ag/TiN coated sensor indicated large angle shifting only for glucose detection which portrays its non-versatility feature. The proposed Ag/ZrN based SPR sensor able to identify the analytes, with almost similar refractive index values with sensitivity values of 0.6725 °/RIU (glucose detection) and 0.6724°/RIU (sucrose detection). In conclusion, Ag/ZrN (tAg=44nm, tZrN=10nm) offers better sensitivity and selectivity performance than Ag/TiN because of the absorption enhancement inside the Ag due to the high scattering efficiency of ZrN.

This review aims to investigate the potential of various plasmonic materials for Coronavirus Disease 2019 (Covid19) detection in terms of performance, limitations and future prospects. A few parameters have been reviewed, such as sensitivity, the Limit of Detection (LOD), time response, and thickness of materials. This review analyses plasmonic materials used to excite the Surface Plasmon Resonance (SPR) effect, such as gold-based, silver-based, copper-based, and metal nanoparticles. In addition, the additional or hybrid materials are reviewed as well. Gold-based SPR sensors perform excellently in detecting various viruses, including Covid-19. The implementation of gold-based materials includes gold nanomaterial, which has different shapes, for instance, nanospheres, nanorods, and nanoislands. Obviously, the deployment of gold nanomaterials resulted in the best sensitivity. According to the analysis, about 50% of recent research chose gold nanomaterials as plasmonic materials for sensing applications concerning their outstanding properties such as high stability, oxidation resistance and simple fabrication. Besides gold nanomaterials, hybrid-based gold material such as graphene-gold based sensor exhibits a good sensitivity of about 183.3◦/RIU, in which 25% of current studies utilized this plasmonic material for virus detection. In conclusion, gold nanomaterials-based plasmonic sensors have a bright potential to be implemented for Covid-19 detection, and adding another material like graphene can enhance the performance. We believe that the output of this study will contribute to developing biosensors for detecting Covid-19.

With the increasing demand for greater quality of transferred data, the optical cable lines are reaching their limits of transfer capacities. The alternative for more effective usage is by introducing the Dense Wavelength Division Multiplexing (DWDM) integrated with optical amplifier to optimize the output signal. This study was performed theoretically with an assistance of OptiSystem 9.0 simulation software to develop higher transfer speed of 32 channels DWDM network system by employing hybrid optical amplifiers. Three types of optical amplifiers had been introduced such as Erbium Doped Fiber Amplifier (EDFA), Semiconductor Optical Amplifier (SOA) and Dynamic RAMAN amplifier. The optimum performance of DWDM system was obtained by employed hybrid EDFA-Raman amplifier which resulted the best transmission signal received with maximum Qfactor=43.0579 a.u. The hybrid EDFA-Raman produced better stability than EDFA-SOA where the received signals were only fluctuated within ±3.73 a.u. In comparison with other types of configuration, namely EDFA-SOA and RAMAN-SOA; the value of maximum Q-factor experienced about 50% of increment. In conclusion, the development of high performance and excellent stability of 32- channels DWDM optical network system can be achieved by introduced hybrid amplifier of EDFA-RAMAN