Multimode Plastic Optical Fiber Research Articles

Plasmonic sensor combined with a microcuvette device for monitoring molecule binding processes at ultra-low concentrations

A novel sensing strategy is presented to monitor receptor-target pair interactions at ultra-low concentrations without functionalization processes. The biosensing is made by a sensitive chip and a surface plasmon resonance (SPR) probe connected in series, both built up on multimode plastic optical fibers (POFs). The SPR probe is a conventional D-shaped POF platform, while the capture platform consists of three microholes, containing a few hundred nanoliters each, made in the core of a modified POF. The microholes are filled with a specific receptor solution, which selectively captures the target present in the samples dropped over the filled microholes. Any variation occurring in the microholes due to the molecule binding processes changes the mode profile of the propagated light in the POF's core, modifying the plasmonic effects proportionally to the phenomena under scrutiny. As a proof of concept, the interactions of two receptor-target pairs, estradiol and cortisol to the respective receptors, namely Estrogen Receptor alpha protein (ER) and Glucocorticoid Receptor (GR), were monitored over time in the attomolar range. The receptor-target pair interactions are observed at ultra-low concentrations (order of aM) by monitoring the resonance wavelength shift over time. The proposed sensing approach stands for a novel class of laboratory instrumentation with unprecedented capabilities in terms of compactness, ultra-high sensitivity and low-cost.

Long Period Grating Imprinted on a Flat-Shaped Plastic Optical Fiber for Refractive Index Sensing

A corrugated surface long period grating (LPG) was fabricated on a flat-shaped plastic optical fiber (POF) as a refractive index (RI) sensor by a simple pressing with the heat pressure and mechanical die press print method. The light propagation characteristics of an LPG imprinted on a multi-mode POF were analyzed by the method of geometrical optics. Theoretical and experimental results showed that the structural parameters of the sensor affected the RI sensing performance, and the sensor with a thinner flat thickness, a deeper groove depth of the corrugated surface LPG, and a longer LPG exhibited better RI sensing performance. When the POF with a diameter of 1 mm was pressed with the heat pressure to a flat shape with a thickness of 600 µm, an LPG with a period of 300 µm, a groove depth of 200 µm, and a length of 6 cm was fabricated on it, and the RI sensitivity of 1447%/RIU was obtained with a resolution of 5.494×10−6 RIU. In addition, the influences of the POF cladding, tilting of LPG, and bending of the sensing structure were investigated. The results demonstrated that after removing the cladding and tilting or bending the LPG, the RI sensing performance was improved. When the LPG imprinted on the flat-shaped POF was bent with a curvature radius of 6/π cm, the highest sensitivity of 6 563%/RIU was achieved with a resolution of 2.487×10−9 RIU in the RI range of 1.3330–1.4230. The proposed sensor is a low-cost solution for RI measurement with the features of easy fabrication, high sensitivity, and intensity modulation at the visible wavelengths.

Magnetic field sensing characteristics of rGO/BiMnO3 nanocomposites loaded clad-modified optical fiber sensor

In this paper, the clad-modified multimode plastic optical fiber (POF) was developed using pristine BiMnO 3 (BMO) and BMO/rGO as a sensor material. The BMO and BMO/rGO were synthesized using the hydrothermal method. The structural, morphological, optical, and dielectric properties were studied using X-ray diffraction (XRD), Scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FT-IR), UV–vis spectrophotometer, and LCR meter. The magnetic field sensing characterization was performed using clad-modified optical fiber technology. Due to the magneto-optic and LSPR effect, the modified cladding with BMO/rGO sensor is highly sensitive to applied magnetic fields compared with the pristine BMO. The BMO/rGO sensor had achieved a high sensitivity response of 102.2% (693 nm) and 50.5% (772 nm) at 190 mT.

A Temperature Sensor Exploiting Plasmonic Phenomena Changes in Multimode POFs

A novel sensing method for temperature measurements of liquids, exploiting plasmonic resonance in multimode plastic optical fibers (POFs), has been devised. The possibility to measure the temperature is useful in several application fields of plasmonic sensors, such as when a binding test between a receptor and an analyte occurs, considering that the binding parameters are a function of the temperature. The novel temperature sensor consists of two different D-shaped POF connected in a cascade. The first element is a thermosensitive platform with a thin silicone layer on the POF core, whereas the second is a conventional surface plasmon resonance (SPR) D-shaped POF sensor. The operating principle of the novel temperature sensor is based on the variations of light launch conditions in the SPR-POF sensor as a consequence of the temperature changes in the solution covering the thermosensitive platform. In this way, the input light ray angle changes with the temperature, producing a shift in resonance wavelength conditions. The proposed sensor has been tested, as proof of concept, in a temperature range from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20^{\circ }\text{C}$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$38^{\circ }\text{C}$ </tex-math></inline-formula> with a step size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3^{\circ }\text{C}$ </tex-math></inline-formula> , to establish the role of the silicone layer on the thermosensitive platform and the best configuration in terms of sensitivity.

Exploiting Plasmonic Phenomena in Polymer Optical Fibers to Realize a Force Sensor.

In this work, a novel sensing approach to realize a force optical fiber sensor is designed, developed, and experimentally tested. The proposed sensing methodology exploits the effects of deformation due to an applied force on a patch of plastic optical fiber (POF) connected at the input of a surface plasmon resonance (SPR) sensor realized in a D-shaped POF. Therefore, the proposed force sensor system consists of an SPR D-shaped POF sensor, connected to a spectrometer, within input of a POF patch, connected to a light source used for interacting with the applied force. When the applied force on the patch changes, the mode profile of the light in the multimode POF patch and the SPR-POF sensor change too, so the SPR spectra shift. The obtained experimental results demonstrate that the proposed sensor has a resolution of the force sensor equal to about 22 mN and an excellent linear response in the range from 0 N to 0.5 N.

Theoretical Investigation of the Influence of Wavelength on the Bandwidth in Multimode W-Type Plastic Optical Fibers with Graded-Index Core Distribution.

The bandwidth of multimode W-type plastic optical fibers (POFs) with graded-index (GI) core distribution is investigated by solving the time-dependent power flow equation. The multimode W-type GI POF is designed from a multimode single-clad (SC) GI POF fiber upon modification of the cladding layer of the latter. Results show how the bandwidth in W-type GI POFs can be enhanced by increasing the wavelength for different widths of the intermediate layer and refractive indices of the outer cladding. These fibers are characterized according to their apparent efficiency to reduce modal dispersion and increase bandwidth.

A Molecularly Imprinted Polymer Based SPR Sensor for 2-Furaldehyde Determination in Oil Matrices

Optical chemosensors with surface plasmon resonance (SPR) transduction are widely employed, even in complex environments, such as those outside the laboratory. In this context, not only the chemical nature but also the physical form of the receptor layer is particularly relevant. Synthetic receptors as molecularly imprinted polymers (MIPs) are well suited. This is demonstrated here in the case of an SPR sensor platform based on a multimode plastic optical fiber, which is very promising for on site application due to the low dimensions and low cost. A specific MIP was used as the receptor, with high affinity for the substance to be determined, 2-furaldehyde, in water. Here, a medium of high refractive index, i.e., vegetable oil, was considered because of the high interest for its determination in industrial diagnostics. The effects of the MIP layer thickness and the washing extent on the quality of the analytical signal were investigated. Better spectra were generated at the thinner MIP layer, while a lower detection limit is reached with extended washing.

Investigation of performance properties of plastic optical fibres used in a traffic light system

We investigate the performance properties of a multimode plastic optical fibre (POF) used in a traffic light system. An analytical function is proposed for predicting the angular power distribution at the output end of a multimode optical fibre when the beam at the input end of the fibre is centrally launched along the fibre axis. We demonstrate how mode coupling affects the output angular power distribution along the fibre and, therefore, the performance of optical fibre used as part of a traffic light system. It is found that as the length of the POF increases, the angular power distribution broadens until it reaches a length at which a steady-state distribution (SSD) is achieved. This broadening is insignificant at short POF lengths of up to 10 m. As a result, the effective radiation area at the output end of any long POF as part of different light systems, such as traffic, building, and bridge light systems, can be determined.

Surface Plasmon Plastic Optical Fiber Resonance with Multi-Layer as Chemical Sensor

A chemical optical fiber sensor based on surface plasmon resonance (SPR) was developed and implemented using multimode plastic optical fiber. The sensor is used to detect and measure the refractive index and concentration of various chemical materials (Urea, Ammonia, Formaldehyde and Sulfuric acid) as well as to evaluate the performance parameters such as sensitivity, signal to noise ratio, resolution and figure of merit. It was noticed that the value of the sensitivity of the optical fiber-based SPR sensor, with 60nm and 10 mm long, Aluminum(Al) and Gold (Au) metals film exposed sensing region, was 4.4 μm, while the SNR was 0.20, figure of merit was 20 and resolution 0.00045. In this work a multimode plastic optical fiber with a core diameter of 980 μm, fluorinated polymer cladding of 20 μm and a numerical aperture of 0.51 was used.

Millimeter-wave enabled PAM-4 data transmission over hybrid FSO-MMPOF link for access networks

In this paper, we propose a full duplex architecture based on a hybrid link composed of free space optics (FSO) and multimode plastic optical fiber (MMPOF) for short-range wireless access networks. The proposed architecture employs mode group division multiplexing (MGDM) and wavelength reuse techniques to transmit data between central unit (CU) and radio access units (RAUs). An optical frequency comb source to generate multiple optical sidebands is realized using a single laser source to provide 60 GHz millimeter-wave (mm-wave) signals at each RAU by simultaneously transmitting PAM-4 signal on linearly polarized (LP) modes of each optical sideband. Data rate of 2times12 Gbps at mm-wave frequency of 60 GHz is achieved for both downlink (DL) and uplink (UL) transmissions. The transmission of 2times12 Gbps PAM-4 signal over hybrid FSO-MMPOF link is investigated at different values of refractive index structure parameter (C_n^2) by employing log-normal (LN) FSO channel model to support three RAUs in a ring topology. The acceptable receiver sensitivities below −5 and −0.6 dBm for DL and UL transmissions are achieved, respectively. The proposed hybrid architecture can be a potential candidate for future communication networks.

A review on simple and highly sensitive plastic optical fiber probes for bio-chemical sensing

Abstract A review on bio-chemical label-free sensing applications based on receptors combined with multimode plastic optical fibers (POFs) is carried out. In particular, this work focuses on different kinds of POF intrinsic sensors used in transmission mode, exploiting various types of receptors and useful in several application fields. The sensor structures and the sensing mechanisms of different simple, highly sensitive, and low-cost POF probes are reported and compared. Moreover, different kinds of chemical and biological receptors combined with POF probes, highlighting the advantages and disadvantages of each receptor, are presented in detail. More specifically, the chosen POF sensing platforms, including low-cost and simple interrogation setups, are described showing their ability to monitor specific receptors exploiting intensity variation techniques and plasmonic phenomena, as well. Finally, a prospect of future developments of biochemical sensors with multimode POFs is discussed.

A Magnetic Field Sensor Based on SPR-POF Platforms and Ferrofluids

We present a novel methodology for magnetic field sensing by exploiting surface plasmon resonance (SPR) sensors based on D-shaped plastic optical fiber (POF) and magnetic fluids (MFs). The proposed methodology adopts a multimode POF patch covered with ferrofluid placed between the light source and the SPR-POF platform. The working principle exploits the changing of the SPR spectra due to variations of the SPR resonance conditions generated by the changing in the input light in the SPR-POF sensor due to the attractive force exerted by the target magnetic field on the POF covered with ferrofluid. A model showing a good fitting between the simulated and measured values of the magnetic field is also presented. A proof of concept for this novel sensing approach has been obtained exploiting a prototype of a sensor that has been characterized in the range of values between 0.15 and 1.2 mT. Particularly, we have estimated, in the linear range of the sensor response, sensitivity equal to about 6800 pm/mT and resolution equal to about 0.029 mT. Moreover, the comparison between the expected and the experimental behavior has shown a very good match with a mean squared error of about 5%.

Investigation of the characteristics of a fiber-optic gas-liquid two-phase flow sensor.

A laboratory-prepared wedge-shaped fiber probe using step-index multimode plastic optical fiber was described and tested in a lab-scale gas-liquid flow generator. A three-dimensional model was established in order to fully simulate the process of bubble piercing by the optical fiber probe. A theoretical analysis of the luminous intensity distribution of the light transmission in the process of bubble piercing was undertaken under conditions of different relative positions between the fiber probe and the bubble axis. Using this analytical method, it was possible to accurately define the range of the central region of the bubble where the presignal appeared.

Experimental Characterization of Plasmonic Sensors Based on Lab-Built Tapered Plastic Optical Fibers

In this work, we have compared several configurations of surface plasmon resonance (SPR) sensors based on D-shaped tapered plastic optical fibers (TPOFs). Particularly, the TPOFs used to obtain the SPR sensors are made by a lab-built system based on two motorized linear positioning stages and a heating plate. Preliminarily, a comparative analysis has been carried out between two different configurations, one with and one without a thin buffer layer deposited between the core of TPOFs and the gold film. After this preliminary step, we have used the simpler configuration, obtained without the buffer layer, to realize different SPR D-shaped TPOF sensors. This study could be of interest in SPR D-shaped multimode plastic optical fiber (POF) sensors because, without the tapers, the performances decrease when the POF’s diameter decreases, whereas the performances improve in SPR D-shaped tapered POF sensors, where the diameter decreases in the D-shaped sensing area. The performances of the SPR sensors based on different taper ratios have been analyzed and compared. The SPR-TPOF sensors have been tested using water–glycerin mixtures with refractive indices ranging from 1.332 to 1.381 RIU. According to the theory, the experimental results have demonstrated that, as the taper ratio increases, the sensitivity of the SPR sensor increases as well, while on the contrary the signal-to-noise ratio (SNR) decreases.

Shaping Beam Profiles Using Plastic Optical Fiber Tapers with Application to Ice Sensors.

Using either bulk or fiber optics the profile of laser beams can be altered from Gaussian to top-hat or hollow beams allowing enhanced performance in applications like laser cooling, optical trapping, and fiber sensing. Here, we report a method based on multimode Plastic Optical Fibers (POF) long-tapers, to tweak the beam profile from near Gaussian to a hollow beam, by generating surface irregularities on the conical sections of the taper with a heat-and-pull technique. Furthermore, a cutback technique applied on long tapers expanded the output beam profile by more than twice the numerical aperture (NA) of the fiber. The enhanced sensitivity and detection efficiency of the extended profile was tested on a fiber optical ice sensor related to aviation safety.

Detection of salinity in the process of heating seawater by using a directional coupler of the multimode plastic optical fiber with a plane mirror as a reflector

Plastic optical fiber (POF) FD 620 10 has been widely used in various sensors with the basic principle of utilizing the intensity received because of reflection, one of which is used as a displacement sensor. In this study, POF was used as a directional coupler and was applied for the detection of the refractive index of sodium chloride (NaCl) solutions due to changes in concentration and detection of salinity in the process seawater heating. The results of this study indicate that the sensor system has succeeded in detecting the refractive index of the NaCl solution at a concentration of 0–20% and changes in the salinity of seawater due to the heating process. This sensor system is simple and easy to use, and the manufacturing cost is relatively cheap. The results of this study indicate that the sensor system has succeeded in detecting the refractive index of the NaCl solution at a concentration of 0–20% and changes in the salinity of seawater due to the heating process at the temperature range from 13 to 58 °C. This sensor system is simple and easy to use and the manufacturing cost is relatively cheap.

Fiber-optic humidity sensor system for the monitoring and detection of coolant leakage in nuclear power plants

In this study, we developed a fiber-optic humidity sensor (FOHS) system for the monitoring and detection of coolant leakage in nuclear power plants. The FOHS system includes an FOHS, a spectrometer, a halogen white-light source, and a Y-coupler. The FOHS is composed of a humidity-sensing material, a metal tube, a multi-mode plastic optical fiber, and a subminiature version A (SMA) fiber-optic connector. The humidity-sensing material is synthesized from a mixture of polyvinylidene fluoride (PVDF) in dimethyl sulfoxide (DMSO) and hydroxyethyl cellulose (HEC) in distilled water. We measured the optical intensity of the light signals reflected from the FOHS placed inside the humidity chamber with relative humidity (RH) variation from 40 to 95%. We found that the optical intensity of the sensing probe increased linearly with the RH. The reversibility and reproducibility of the FOHS were also evaluated.

Refractive Index Sensing Based on a Long Period Grating Imprinted on a Multimode Plastic Optical Fiber

A corrugated surface long period grating (LPG) is fabricated on a commercial multimode plastic optical fiber (POF) by a simple mechanical die press print method. This so-obtained LPG is proposed as a refractive index (RI) sensor. The LPGs imprinted on the POFs with different diameters are evaluated, and it shows that an LPG on a thin POF (with a diameter of 0.25 mm) exhibits better RI sensing performance than that of the ones on thick POFs (with diameters of 0.5 and 1.0 mm). By altering the structural parameters of the LPG on the POF with a diameter of 0.25 mm, the RI sensing performance is studied. When the grating period is $100~\mu \text{m}$ , the groove depth is $65~\mu \text{m}$ , and the tilted angle is 20°, the optimum sensitivity of 2815%/RIU with a resolution of $1.39\times 10^{\mathbf {-4}}$ RIU is achieved in the RI range of 1.33–1.45. In addition, the characteristic of the temperature dependence of the sensor is presented. The proposed sensor is a low-cost solution for RI measurement and with the features of simple structure, easy fabrication, and intensity modulation at visible wavelengths.

Two-dimensional displacement optical fiber sensor based on macro-bending effect

This paper highlights a novel and simple approach for two-dimensional displacement sensor’s design based on macro-bending loss and optical power coupling effect. Multimode plastic optical fiber offers flexibility in bending which can easily radiate bend loss and easily side coupled with second fiber (receiving fiber RF). In this approach of 2D system, dual-time repeated twisting has been carried out with transmitting fiber (TF). Two RFs were employed in experiment and twisted in such a way that for the measurement of x-axis displacement (First RF is twisted with TF) and for measurement of y-axis displacement (Second RF is twisted with TF. The experimental measurement results of two dimensions sensor have been achieved for forward and backhaul movement with good consistency up to 160 mm and system has linearity from 0 mm to 100 mm having sensitivity of 2.6 nW/mm. The 2D sensor has numerous industrial applications in robotics, precision alignment, bridges and many more. In this context, the aforementioned technique could be considered as more holistic and optimal in comparison to the existing techniques.

In-Fiber Optic Salinity Sensing: A Potential Application for Offshore Concrete Structure Protection.

The protection of concrete structures against corrosion in marine environments has always been a challenge due to the presence of a saline solution—A natural corrosive agent to the concrete paste and steel reinforcements. The concentration of salt is a key parameter influencing the rate of corrosion. In this paper, we propose an optical fiber-based salinity sensor based on bundled multimode plastic optical fiber (POF) as a sensor probe and a concave mirror as a reflector in conjunction with an intensity modulation technique. A refractive index (RI) sensing approach is analytically investigated and the findings are in agreement with the experimental results. A maximum sensitivity of 14,847.486/RIU can be achieved at RI = 1.3525. The proposed technique is suitable for in situ measurement and monitoring of salinity in liquid.