Plastic Clad Silica Fiber Research Articles

Exploiting the Advantages of Ag/ITO/Enzyme Trapped Gel Layers to Develop a Highly Sensitive and Selective Fiber Optic Plasmonic Urea Sensor

The fabrication and characterization of a surface plasmon resonance (SPR)-based urea biosensor, with thin silver (Ag), ITO (In2O3: SnO2), and enzyme-trapped gel over an unclad portion of plastic-clad silica fiber as a sensing element, is represented. The working principle is to identify changes in the refractive index of the enzyme (urease) entrapped gel layer following the interaction with the incoming analyte. This interaction causes swelling and shrinkage of the gel layer, which alters the effective refractive index of the sensing layer. The wavelength interrogation method is used, and the optimized sensor probe is characterized by urea samples having different pH values. Scanning electron microscopy confirmed the uniformity of the silver layer over the unclad core of the fiber. The sensor operates from 0 to 160 mM of urea concentrations to cover the physiological concentration range of blood urea normally present in the human body. The sensitivity and limit of detection (LOD) offered by the sensor are marked 0.59387 nm/mM near zero concentration of the urea sample and 0.56 mM, respectively, along with the provisions of high stability, remote sensing, and online monitoring of urea. The proposed sensor has proven to be one of a kind due to its fast response time.

Optimization of Multimode Fibers for Surface Plasmon Resonance Based Sensors Under Spectral and Single Wavelength Intensity Interrogation

In an optical fiber based SPR sensor, a segment of metal clad silica fiber is used as the sensing element and resonant coupling occurs to the surface plasmon mode excited at the interface of the metal and ambient which surrounds the sensing element. When polychromatic light is transmitted through the sensing element, the spectrum of light detected at the other end shows minima at a resonance wavelength. In wavelength interrogation, the shift in the resonance wavelength is a measure of change in the refractive index of the ambient. Alternatively, intensity interrogation can be used in which the change in transmitted power at a given wavelength is a measure of change in refractive index of the ambient. The sensitivity and detection accuracy of the sensor depend on the numerical aperture (NA) of the multimode optical fiber used to fabricate the sensor. In the present work, we have carried out a study of the dependence of the sensitivity and detection accuracy on numerical aperture to obtain the optimal value for a multimode optical fiber which is used to fabricate the sensing element under both wavelength and intensity interrogation. For a gold clad sensing element with l/a = 33.33 for the refractive index of the ambient in the range 1.33 to 1.38, the optimized numerical aperture is obtained as \(NA\)= 0.2 for spectral interrogation mode. At this optimal value, the sensitivity is estimated to be 4040 nm/RIU and detection accuracy lies between 20 and 48 μm−1. In single wavelength intensity interrogation, at the He–Ne laser wavelength (633 nm), the optimized numerical aperture is obtained as \(NA\)= 0.42. Experimental results on a sensing element fabricated with gold coating on the core of a plastic clad silica fiber are also reported.

Observation of strong mode coupling in multimode step index silica optical fibers with fluorinated thermoplastic polymer cladding

Using the power flow equation, the state of mode coupling in step index multimode silica optical fiber with fluorinated thermoplastic polymer cladding is investigated in this work. Coupling coefficient is determined by employing our previously reported calculation method. The silica optical fiber with fluorinated thermoplastic polymer cladding shows much stronger mode coupling than the all plastic-clad silica fibers investigated in earlier works. Consequently, it takes much shorter fiber length for the equilibrium mode distribution or steady state distribution to develop (faster launch beam narrowing), which is of great interest in employing silica optical fiber with fluorinated thermoplastic polymer as a part of telecommunication, medical and sensory system.

Mode coupling in bent and twisted step-index plastic-clad silica fibers

The state of mode coupling in bent and twisted step-index plastic-clad silica fibers is investigated in this article by the numerical solving of the time-independent power flow equation. The coupling length Lc at which the equilibrium mode distribution is achieved and the length zs of the fiber required for achieving the steady-state mode distribution are obtained. It was found that the bent and twisted step-index plastic-clad silica fiber investigated in this work shows a much stronger mode coupling than the straight plastic-clad silica fiber. As a result, the coupling lengths where equilibrium mode distribution is achieved, and the lengths of fiber required for achieving a steady-state mode distribution for bent and twisted fibers, are much shorter than corresponding lengths for straight fibers.

Wavelength dependence of equilibrium mode distribution and steady state distribution in W-type plastic-clad silica fibers

Abstract Wavelength dependence of equilibrium mode distribution (EMD) and steady state distribution (SSD) in W-type plastic-clad silica fibers (PCSFs) is investigated in this paper for parametrically varied width of the fiber’s intermediate optical layer and refractive index of the outer cladding. We have shown that the W-type PCSF has better transmission characteristics at longer infrared wavelengths. This is explained by the rise of the leaky mode losses with increasing wavelength. This facilitates tailoring W-fibers to a specific application at hand in the infrared wavelength region.

A Numerical Analysis of Various pH Level for Fiber Optic pH Sensor Based on Bromophenol Blue in Silica

The fabrication and characterization of an optical fiber pH sensor for the detection range 2 – 7 are described. The sensing element was prepared by coating the uncladded middle portion of a multimode plastic clad silica fiber (PCF) with xerogel film of immobilized bromophenol blue (BPB) prepared by a sol-gel process. The exponential decay of the evanescent wave at the core-cladding interface of the multimode fiber was utilized to determine the pH response. The objective of this work is to analyze the measurement of the fiber optic sensing probe towards various pH level. The intensity of the absorbance was analyzed using statistical technique (Statistical Package for the Social Sciences, SPSS) to identify the significant pH range that can be used as a reference in developing the sensor instrumentation in the future. pH2 shows the highest significance among all pH values based on the statistical results using error plots.

Optically active phenolphthalein encapsulated gold nanodendrites for fiber optic pH sensing

Herein, sol-gel based synthesis of poly ethanol glycol assisted gold nanodendrites (AuNDs) is reported at low-temperature. Taking advantage of its facile synthesis, phenolphthalein (phph) is encapsulated/immobilized in AuNDs for the assay of fiber optic pH sensing. Hierarchical structure is observed by FE-SEM analysis before and after phph encapsulation. EDX analysis confirms the uniform distribution of elements with smooth morphology. AFM analysis shows that phph encapsulated AuNDs have low average roughness (2 nm) and less thickness ~20 nm. The chemical bonding between phph species and Au molecules are explored by FTIR analysis. The polycrystalline nature of AuNDs matrix before and after encapsulation is confirmed by XRD. HR-TEM analysis exhibited preferential growth of dendrites structure before and after encapsulation along (111) direction. UV–Vis analysis shows that AuNDs has refractive index 1.24 at 550 nm, which reduces down to 1.18 at 550 nm after phph encapsulation. 30 cm coated middle segment of plastic clad silica fiber (PCS) is used as sensor. Variations in output intensities in terms of transmission are used to characterize the sensor response. A fast response ~0.87 s, repeatability/reproducibility and linear response (R2 = 0.8912) is obtained at 440 nm. Acidity of rainwater (pH 6) is determined by prepared sensor for validity purpose and practical applications.

Mode coupling and its influence on space division multiplexing in step-index plastic-clad silica fibers

Abstract The state of mode coupling in step-index plastic-clad silica fibers is investigated in this article by numerical solving of the time-independent power flow equation. The coupling length Lc at which the equilibrium mode distribution is achieved and the length (zs) of the fiber required for achieving the steady-state mode distribution are obtained. It was found that the plastic clad silica fiber investigated in this work showed a much weaker mode coupling than the plastic-clad silica fibers investigated in earlier works. We have also shown that mode coupling significantly limits the fiber length at which the space division multiplexing (SDM) can be realized with a minimal crosstalk between the neighbor optical channels.

Self-assembled hierarchical phenolphthalein encapsulated silica nanoparticles: Structural, optical and sensing response

Exploration of novel meso-materials with higher surface areas is a major challenge in the rapidly expanding field of opto-chemical sensor devices. Therefore, synthesis and growth mechanism of surfactant CTAB assisted sol-gel based silica and phenolphthalein encapsulated silica nanoparticles (NPs) and their optical and pH sensing activities is reported at low temperature in this present communication. Hierarchical/ordered structures/architectures are observed after encapsulation of phenolphthalein by FE-SEM analysis. AFM analysis exhibits the formation of porous nanostructures with average surface roughness Ra ∼5.15nm which is reduced to Ra ∼4.98nm after encapsulation of phenolphthalein, whereas, particle size increased from 8nm to 13nm. N2 adsorption isotherms explain the meso-porous nature of the matrix with high surface area value of 443m2/g with a pore volume of 0.93cm3/g and pore diameter of 85.59Å. Experimental findings show that the prepared meso-silica-phenolphthalein frameworks have high thermal stability, low refractive index (1.33) with good optical transparency of 83%. Furthermore, the evanescent wave is used to selectively excite the phph molecules encapsulated in silica matrix and deposited on the Plastic Clad Silica fiber as cladding for sampling the aqueous media (pH solutions 2–12) surrounding the fiber. Highest sensing response is optimized for pH 12 within 1s with pink color indication. The improved structural and optical characteristics identify that the prepared optochemical nanosensor device has potential for fast detection of pH at dynamic range.

Mode coupling in multimode step-index plastic-clad silica fibers with corrugated surfaces

The state of mode coupling in step-index plastic-clad silica fibers with corrugated surfaces is investigated in this article using the power flow equation. The coupling coefficient in this equation was obtained using our previously reported method. This enabled us to obtain the length of the corrugated piece of the fiber at which equilibrium mode distribution is achieved as well as the length at which a steady state distribution is established. It was found that the plastic-clad silica fibers with corrugated surfaces showed much stronger mode coupling than plastic-clad silica fibers without corrugated surfaces. Consequently, the equilibrium as well as steady state mode distributions were achieved at shorter fiber lengths in plastic-clad silica fibers with corrugated surfaces than in the same type of optical fibers without corrugated surfaces.

Graphene/Au-Enhanced Plastic Clad Silica Fiber Optic Surface Plasmon Resonance Sensor

Owing to its large surface-to-volume ratio and good biocompatibility, graphene has been identified as a highly promising candidate as the sensing layer for fiber optic sensors. In this paper, a graphene/Au-enhanced plastic clad silica (PCS) fiber optic surface plasmon resonance (SPR) sensor is presented. A sheet of graphene is employed as a sensing layer coated around the Au film on the PCS fiber surface. The PCS fiber is chosen to overcome the shortcomings of the structured microfibers and construct a more stable and reliable device. It is demonstrated that the introduction of graphene can enhance the intensity of the confined electric field surrounding the sensing layer, which results in a stronger light-matter interaction and thereby the improved sensitivity. The sensitivity of graphene-based fiber optic SPR sensor exhibits more than two times larger than that of the conventional gold film SPR fiber optic sensor. Furthermore, the dynamic response analyses reveal that the graphene/Au fiber optic SPR sensor exhibits a fast response (5 s response time) and excellent reusability (3.5% fluctuation) to the protein biomolecules. Such a graphene/Au fiber optic SPR sensor with high sensitivity and fast response shows a great promise for the future biochemical application.

LSPR based fiber optic sensor for fluoride impurity sensing in potable water

We have designed localised surface plasmon resonance (LSPR) based fiber optic sensor. Silver nanoparticles are deposited on a few centimetre length of bare core at the middle part of plastic clad silica fiber by means of a simple and low cost laser induced nanoparticle deposition technique. The nanoparticle deposition was confirmed by TEM analysis. The nanoparticle coated fiber is used to design the sensor and the response of sensor was studied to sense fluoride impurity in water.

Sol–gel based fiber optic pH nanosensor: Structural and sensing properties

Evanescent wave absorption based PCS (plastic clad silica) fiber optic pH sensor is constructed by encapsulation of indicator dyes in the heterogeneous inorganic hybrid silica–titania nanomatrix in the presence of cetyl trimethyl ammonium bromide (CTAB) surfactant by sol–gel method. A nanoporous multilayers (triple layer and six layers) of silica–titania hybrid is deposited on 5cm uncladed middle portion of the fiber by dip-coating sol–gel technique. The CTAB surfactant expressively improved the host matrix structure and enhanced its porosity. Thermally stable, adhesive and smooth thin nanocladding has been examined using microscopic and thermal analysis. Indicators encapsulated nanomatrices are highly sensitive to pH and show optical output signals in terms of intensity. Therefore, it provides confirmation that interactions between the host matrix and pH-indicator molecules are in good assistance. Furthermore, experimental findings reveal that the sensing species are probably better encapsulated in the matrix and show no leaching of sensing molecules. The prepared nanosensors exhibit a much faster response time because of the material to be sensed diffuses faster into the triple-layer sensors <2s. These pH sensors are found to have 60 days (2 months) age stability and high reproducibility. A repeatable response over a wide range of pH values between 3 and 11 is obtained.

Mode Coupling in Plastic-Clad Silica Fibers and Organic Glass-Clad PMMA Fibers

Using the power flow equation, the state of mode coupling in plastic-clad silica fiber and organic glass-clad PMMA fiber is investigated in this article. Coupling coefficients are determined by extending our previously reported calculation method to the narrowing beams that are launched with distributions wider than the corresponding steady state distributions. It was found that the organic glass-clad PMMA fiber showed stronger mode coupling than the plastic-clad silica fiber. Consequently, the fiber length for achieving the steady state distribution was shorter for organic glass-clad PMMA fibers than for plastic-clad silica fibers.

Submarine fiber cable network systems cost planning considerations with achieved high transmission capacity and signal quality enhancement

This paper has presented theoretically the comparison between three types of fibers which are investigated extensively: plastic clad silica (PCS), polystyrene (PS) and perfluorinated graded index polymer optical fibers (PF GI-POF) for high speed undersea cable systems. Based on experimental data, both the deep ocean water temperature and pressure are tailored as functions of the water depth. It is taken into account the estimation of the total cost of the submarine fiber cable system for transmission techniques under study. The system capacity as well as the spectral losses, and the dispersion effects are parametrically investigated over wide range ranges of the set of affecting parameters {wavelength, ocean depth (and consequently the ocean pressure and temperature), and the chemical structure}. The results show that PCS has the optimum performance in compared with other fibers. Therefore PCS fiber is the most appropriate candidate among all types of fibers for high speed local submarine communication systems.

Evanescent field absorption sensor for detection of copper (II) in water using multimode optical fiber

The evanescent field absorption sensor for the detection of trace amount of copper (II) in water is experimentally analyzed with the etched step index multimode plastic clad silica (PCS) fiber. The designed sensor is sensitive to copper (II) content in water with a range up to 250 ppm.

Optical-Fiber Corrosion Sensor Based on Deposit of Au/Ni–P

The realization of an optical-fiber corrosion sensor (OFCS) has been achieved using two different methods. In the first method, a plastic clad silica (PCS) fiber whose uncladded part (2 cm in length) has been metallized through deposition using nickel–phosphorus. In the second method, metallization used gold and nickel–phosphorus. The light power [P(α)] at the exit end of the fiber is recorded as a function of the angle (α, angle of incidence) made by the axis of the fiber and a beam from a laser diode at a 670 nm wavelength applied at the entrance of the fiber. It is observed that the corrosion of the coating material (nickel–phosphorus) modifies the P(α) curves, be it by immersion in phosphoric acid solutions. The full width at half-maximum of these curves increases with increasing corrosion pit density. Kinetic curves of corrosion have been obtained for different concentrations of phosphoric acid. This type of sensor is important because it can be inserted in metallic infrastructures to monitor the corrosion state of the structure in situ.

Particle size effect on porous Sol–Gel doped cladding U-shaped optical fiber critical micelle concentration (CMC) sensor

In this paper, a sol–gel derived coating U-shaped optical fiber sensors for measurement of critical micelle concentration of surfactants has been studied. The doped sol–gel cladding fiber was used to construct an active cladding U-shaped optical fiber CMC measurement sensor. The porous sol–gel film was deposited a 1000 μm core plastic clad silica fiber after removing the cladding of the fiber at the middle portion nearly 6 cm and bending in U-shaped design. CMC detection is based on an adsorption effect in sample solution of sodium dodecylbenzenesulfonate. Three different types of particles size of sol–gel porous cladding were tested in our lab. Test results show that the sensitivity of the small particle size porous sol–gel cladding U-shaped optical fiber in sensing region is higher than that of large particle size sol–gel cladding based U-shaped.

Detection of critical micelle concentration (CMC) using uniform and U-shaped optical fiber in sensing region

In this paper the critical micelle concentration (CMC) in surfactant solutions was detected by using an optical fiber. CMC detection is based on an adsorption effect in sample solution. The incident beam passing through the sensing region of the fiber reflected at the interface between the fiber core and the solution with repeating reflections. The change in adsorption condition leads to an effective change in the refractive index at the surrounding surface of the core. The output signal suddenly increases at the CMC due to the reflectivity change caused by adsorption of surfactant molecules onto the surface of the fiber. Plastic clad silica (PCS) fiber with a uniform sensing region was used to measure the CMC point in surfactant solution. It has been found that sensitivity of the sensor depends on the length of the sensing region, the launching condition of the light source and the optical fiber material. The higher the sensing length, the higher the sensitivity of the sensor. The U-shaped sensing region also tried to find the CMC point, and the experimental results indicate that the U-shaped sensing region is more sensitive than the uniform sensing region. Using this method we are able to detect the CMC of the surfactant solution very accurately and in real time.

An evanescent-wave optical fiber relative humidity sensor with enhanced sensitivity

We report a fiber optic relative humidity (RH) sensor based on the evanescent wave absorption spectroscopy using a single U-bend plastic-clad silica fiber with high dynamic range and high sensitivity. The sensor is fabricated using a CoCl 2 doped thin polymer film coated on the bare fiber core. A comprehensive study of the sensor was made in terms of performance optimization. Sensor response was investigated in terms of the chemically synthesized cladding thickness over the centrally de-cladded U-bent probe. The effect of fiber core diameter on the sensitivity was also studied and the fiber with smaller core diameter was observed to be more sensitive unlike the previously reported results. In addition, we observed that the sensor was having a very fast response to the relative humidity, and was fully reversible, repeatable with a large dynamic range.