Low-cost Plastic Optical Fiber Research Articles

Bandwidth Analysis of High-Speed InGaN Micro-LEDs by an Equivalent Circuit Model

High-speed light-emitting diodes (LEDs) are ideal light sources for low-cost plastic optical fiber communication in data-centers and vehicles. Here, high-speed micro-LEDs based on InGaN quantum dot (QD) active region with different diameters are fabricated and characterized. The -3dB bandwidth around 3.6 GHz and 1.4 GHz are achieved in the blue and green micro-LEDs under current density less than 1 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , respectively, which can work at an environmental temperature of 125 °C. An equivalent circuit model is proposed to analyze the limiting factors of the bandwidth, using which the effects of carrier recombination and RC time constant on modulation bandwidth are separated. It is found that carrier recombination rate is fast enough and the RC constant is still the main limiting factor for the blue micro-LEDs at an injection current density of more than 500 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> even when the diameter scales down to 20 μm, while the recombination rate mainly limits the bandwidth of the green micro-LEDs.

Study on thermal protection and temperature of PMMA plastic optical fiber for concentrated sunlight transmission in daylighting

Daylighting system by concentrating and transmitting sunlight through optical fiber is an emerging technology of direct utilization of solar energy. In this work, a sunlight concentrating and transmitting system via plastic optical fibers was developed and investigated. This study addressed the overheating problem of plastic optical fibers under highly concentrated light irradiation. Polymethylmethacrylate (PMMA) plastic fibers have a strong absorption in the infrared band. The PMMA plastic fiber generates serious heat under highly concentrated light transmission, which leads to its overheating and burning. In this study, an incident light filtering method based on the combination of infrared filter and insulating glass is proposed. By filtering out the infrared band light with significant thermal effect, the PMMA plastic optical fibers are guaranteed to be within a safe working temperature range. Experiments demonstrated that the developed filter system can ensure the safe operation of PMMA plastic optical fibers at the concentration level of about 4300 suns. This shows that it is feasible to use low-cost plastic optical fiber for highly concentrated daylighting system.

Low-cost plastic optical fiber integrated with smartphone for human physiological monitoring

Human physiological signal monitoring is a key factor in diagnosing health conditions, such as monitoring heart rate and respiration. To meet the increasing monitoring requirements, such as safety, economy, and equipment miniaturization, it is necessary to optimize and improve the monitoring device. Polymer optical fiber sensor has great potential in human physiological monitoring because of their inherent safety, compactness, electrical isolation, and flexibility. In this paper, we report the integration of low-cost plastic optical fibers in smartphones for the measurement of respiratory rate and heart rate in human physiological monitoring. The performance of the plastic optical fiber (POF) sensor with different sensitivity zone is analyzed. With three sensitivity zones, the respiratory rate and heart rate can be displayed in the power spectral density simultaneously. For improving the POF sensor performance, the shutter speed of the smartphone is also optimized to 30 s−1. Finally, the POF sensor is tested under different motion states indicate that the sensor can monitor the heart rate and breathing rate under different postures (running, walking, standing, squatting and lying), where the spectral energy is 2.8 ± 0.11 × 108 pt during running and is 1.4 ± 0.55 × 107 pt in the supine state. And it also can be used to assess the dynamic posture, which is important for some potential sensory applications in clinical and home settings.

Instrumented Office Chair With Low-Cost Plastic Optical Fiber Sensors for Posture Control and Work Conditions Optimization

People spend more and more time sitting and this habit has been shown to cause spine pathologies. Thus, the scientific community and the industry have become interested in instrumented chairs development to detect incorrect user postures. In this work we present the development and implementation of invisibles and non-intrusive plastic optical fiber sensor cells to monitor the posture and evaluate the ergonomic behavior of a seated person. The low-cost plastic optical fiber (POF) based sensing devices developed in this work, were implemented in an office chair, to evaluate the workers posture throughout their work day. In addition to the sensors, Android and PC software applications were developed, to provide real time feedback and alerts to the user whenever an inadequate posture is detected, or the seating position is the same for a long time. The proposed approach was evaluated in a study involving six users, and results show that it can detect the user&#x2019;s position with 96.6% accuracy.

Time–space–weight calibrated plastic optical fiber-based pressure sensing carpet

We demonstrate time-, space-, and weight-based calibration techniques for pressure monitoring in the low-cost plastic optical fiber (POF) sensor carpet. It is found that the POF-based pressure sensing platform has several limitations, such as output voltage variations and difference in the sensor response for horizontal and vertical fibers due to convex and concave shapes of bend. To surpass the these limitations, we have developed time-based calibration using time windowing technique to reduce the standard deviation of photodiode output voltage variations by 98%. We have also described space and weight calibration techniques based on the convex and concave shapes of fiber bend. These techniques help in improving the Landweber image reconstruction algorithm to obtain significant clarity and improvement in object pressure images. We also report an artificial intelligence-based algorithm to determine the accuracy of positioning of the load. Experimental results demonstrate that this algorithm gives a mean square error of 0.875 cm in position detection on the carpet. We discuss the potential for a compact and cost-effective pressure sensor carpet, which integrates with the living environment and the outside world.

Low-cost plastic optical fiber sensor embedded in mattress for sleep performance monitoring

In this study, we investigated plastic optical fiber (POF) pressure sensors embedded in mattresses to measure respiration and heart rate for sleep performance monitoring. The signal is amplified in the circuit using a two-stage amplification scheme to collect weak respiration and heart rate signals while an algorithm was designed to obtain respiration and heart rate. We also propose a good reliability cutting-POF technology which can be used to improve pressure sensitivity. The experimental results indicate that the mattress can distinguish four behavioral states related to sleep (on bed, lying, moving and leaving bed) and can detect respiration and heart rate values in different positions and postures. Validation experiments on 10 participants showed that absolute error was less than one breath per minute and two beats per minute, making our approach suitable for household sleeping monitoring.

Plastic fiber optic sensor for continuous liquid level monitoring

The study demonstrates the development of a novel low-cost plastic optical fiber (POF) based sensor for liquid level measurement. The sensor works on the principle of reduction in scattering-based optical losses (in contrast to the increase in optical losses for evanescent wave-based sensing) in a straight decladded fiber with an increase in the liquid level due to refractive index changes in the medium surrounding the fiber. A compact optical setup is developed in-house consisting of two U-bent fiber probes coupled to a single LED on one end and two photodetectors on the other ends to measure the optical intensity changes. One of the U-bent probes is decladded over the length of the fiber to act as a test probe to measure the liquid level, while the other probe acts as a reference to compensate for the light intensity fluctuations due to light source instability and ambient conditions. The difference in voltage responses of the two photodetectors gives a measure for liquid level. We have investigated the fiber optic level sensor response to rising and falling liquid levels over 55 cm in presence of aqueous liquids of different refractive index values (1.33 to 1.38) and 95% ethanol as well as DI water at various temperatures from 16 °C up to 70 °C. A level sensitivity of 1.4 and 3.3 mV/mm for water level changes was obtained for the liquid level below and above 45 cm respectively. In addition, the fiber optic level sensor shows a stable and reproducible response over several cycles of 30 min duration at different liquid levels. The results demonstrate that this fiber optic level sensor is not only easy-to-make, cost-effective and robust but also offers sensitive, stable and reproducible instantaneous level measurements.

Low Cost Plastic Optical Fiber Pressure Sensor Embedded in Mattress for Vital Signal Monitoring.

The aim of this paper is to report the design of a low-cost plastic optical fiber (POF) pressure sensor, embedded in a mattress. We report the design of a multipoint sensor, a cheap alternative to the most common fiber sensors. The sensor is implemented using Arduino board, standard LEDs for optical communication in POF (λ = 645 nm) and a silicon light sensor. The Super ESKA® plastic fibers were used to implement the fiber intensity sensor, arranged in a 4 × 4 matrix. During the breathing cycles, the force transmitted from the lungs to the thorax is in the order of tens of Newtons, and the respiration rate is of one breath every 2–5 s (0.2–0.5 Hz). The sensor has a resolution of force applied on a single point of 2.2–4.5%/N on the normalized voltage output, and a bandwidth of 10 Hz, it is then suitable to monitor the respiration movements. Another issue to be addressed is the presence of hysteresis over load cycles. The sensor was loaded cyclically to estimate the drift of the system, and the hysteresis was found to be negligible.

Groundwater level monitoring using a plastic optical fiber

The present work describes the testing and application of a low cost plastic optical fiber sensor on the monitoring of groundwater levels. Two sensors with different grove depth (½ and ¼ of the core thickness) and a resolution of 20cm along 2m of the optical fiber were produced and tested. The sensors were tested under two experimental setups: water level variation (increasing and decreasing of the water level) and groundwater increase simulation, in a soil column. The analysis of the optical signal’s amplitude and its variations due to the increasing or decreasing of water level showed that both tested sensors presented an appropriate performance and adequate sensibility to groundwater level variation and, therefore, can be used for in situ applications of monitoring.

Single-Chip Receiver for 1.25 Gb/s Over 50-m SI-POF

This letter presents a single chip receiver for short-reach high-speed applications through low-cost plastic optical fiber. It compensates the limited bandwidth caused by the fiber and the external photodiode. The prototype contains a transimpedance amplifier, a continuous-time adaptive equalizer, a limiting amplifier, and a clock and data recovery circuit. Experimentally, we have obtained 1.25 Gb/s transmission for a simple nonreturn to zero modulation in an optical link composed of 50 m of step-index polymer optical fiber and a large area Si p-i-n photodetector. It achieves a power under 110 mW at only 1 V of supply voltage.

Liquid level gauge based in plastic optical fiber

This work reports de development and testing of a low cost plastic optical fiber liquid level sensor for operation within highly flammable or other hazardous environments, such in oil piping or fuel tanks. The sensor consists on a vertical fiber, with engraved grooves, that will be sequentially fulfill when the liquid rises, resulting in an increase of the transmitted optical power. A variation of 2.60% in the transmitted optical power intensity was obtained per measured point. Moreover, the sensor sensitivity and resolution can be tailored accordingly to the application.

Design and deployment of low-cost plastic optical fiber sensors for gas monitoring.

This paper describes an approach to develop and deploy low-cost plastic optical fiber sensors suitable for measuring low concentrations of pollutants in the atmosphere. The sensors are designed by depositing onto the exposed core of a plastic fiber thin films of sensitive compounds via either plasma sputtering or via plasma-enhanced chemical vapor deposition (PECVD). The interaction between the deposited layer and the gas alters the fiber's capability to transmit the light, so that the sensor can simply be realized with a few centimeters of fiber, an LED and a photodiode. Sensors arranged in this way exhibit several advantages in comparison to electrochemical and optical conventional sensors; in particular, they have an extremely low cost and can be easily designed to have an integral, i.e., cumulative, response. The paper describes the sensor design, the preparation procedure and two examples of sensor prototypes that exploit a cumulative response. One sensor is designed for monitoring indoor atmospheres for cultural heritage applications and the other for detecting the presence of particular gas species inside the RPC (resistive plate chamber) muon detector of the Compact Muon Solenoid (CMS) experiment at CERN in Geneva.

A Low-Power CMOS Receiver for 1.25 Gb/s Over 1- mm SI-POF Links

This paper presents an optical receiver for short-reach applications through low-cost plastic optical fiber. The limited bandwidth caused by the fiber and the external photodiode is compensated by a new adaptive equalizer based on the spectrum balancing technique. A clock and data recovery circuit is included that minimizes jitter and metastability using a new multilevel bang-bang architecture. The prototype, implemented in a standard 0.18-μm CMOS process, achieves 1.25 Gb/s with a power of 107 mW at only 1 V.

Review on recent developments of fluorescent oxygen and carbon dioxide optical fiber sensors

Oxygen and carbon dioxide sensors are involved in many chemical and biochemical reactions. Consequently, considerable efforts over years have been devoted to discover and improve suitable techniques for measuring gas concentrations by optical fiber sensors. Optical gas sensors consist of a gas-sensitive dye entrapped in a matrix with a high permeability to gas. With such sensors, gas concentration is evaluated based upon the reduction in luminescence intensity caused by gas quenching of the emitting state. However, the luminescence quenching effect of oxygen is highly sensitive to temperature. Thus, a simple, low-cost plastic optical fiber sensor for dual sensing of temperature and oxygen is presented. Also, a modified Stern-Volmer model is introduced to compensate for the temperature drift while the temperature is obtained by above dual sensor. Recently, we presented highly-sensitive oxygen and dissolved oxygen sensors comprising an optical fiber coated at one end with platinum (II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) and PtTFPP entrapped core-shell silica nanoparticles embedded in an n-octyltriethoxysilane(Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. Also, two-dimensional gas measurement for the distribution of chemical parameters in non-homogeneous samples is developed and is of interest in medical and biological researches.

Acrylic and metal based Y-branch plastic optical fiber splitter with optical NOA63 polymer waveguide taper region

We proposed a simple low-cost acrylic and metal-based Y-branch plastic optical fiber (POF) splitter which utilizes a low cost optical polymer glue NOA63 as the main waveguiding medium at the waveguide taper region. The device is composed of three sections: an input POF waveguide, a middle waveguide taper region and output POF waveguides. A desktop high speed CNC engraver is utilized to produce the mold inserts used for the optical devices. Short POF fibers are inserted into the engraved slots at the input and output ports. UV curable optical polymer glue NOA63 is injected into the waveguide taper region and cured. The assembling is completed when the top plate is positioned to enclose the device structure and connecting screws are secured. Both POF splitters have an average insertion loss of 7.8 dB, coupling ratio of 55: 45 and 57: 43 for the acrylic and metal-based splitters respectively. The devices have excess loss of 4.82 and 4.73 dB for the acrylic and metal-based splitters respectively.

Comparing polymer optical fiber, fiber Bragg grating, and traditional strain gauge for aircraft structural health monitoring

Systems for structural health monitoring in aeronautical structures use methods of measuring the elongation that normally require too heavy setups or difficult assembly jobs, such as those based on traditional strain gauges. Alternative methods based on fiber Bragg gratings tend to be very expensive. We analyze the possibility of improving the existing designs with the aid of low-cost plastic optical fiber sensors. For this purpose we test these sensors in a rudder flap subjected to different types of bending forces. The results show that they offer good stability and repeatability, and the measured values are very similar to those obtained with Bragg sensors.

A Plastic Optical Fiber Sensor for the Dual Sensing of Temperature and Oxygen

This study presents a low-cost plastic optical fiber sensor for the dual sensing of temperature and oxygen. The sensor features commercially available epoxy glue coated on the side-polished fiber surface for temperature sensing and a fluorinated xerogel doped with platinum tetrakis pentrafluoropheny porphine coated on the fiber end for oxygen sensing. The temperature and oxygen indicators are both excited using an ultraviolet light-emitting diode light source with a wavelength of 380 nm. The luminescence emission spectra of the two indicators are well resolved and exhibit no crosstalk effects. Our studies show that the temperature response of the sensor is independent of the oxygen concentration. Overall, the results indicate that the dual sensor presented in this study provides an ideal solution for the noncontact, simultaneous sensing of temperature and oxygen in general biological and medical applications.

Transimpedance Amplifier for Short-Reach SI-POF Links

This paper presents the design of a low-power lowvoltage transimpedance amplifier for short reach applications through low-cost step index plastic optical fiber. The amplifier has been designed in a 180 nm CMOS technology and dissipates 6 mW from a supply voltage of only 1 V. The design achieves 1.25 Gb/s through 50 m POF and a sensitivity of -20 dBm considering a 10-12 BER.

A 1.25 Gb/s Fully Integrated Optical Receiver for SI-POF Applications

This paper presents a 1.25 Gb/s fully integrated BiCMOS optical receiver for short reach applications through low-cost step index plastic optical fiber. The design achieves 1.25 Gb/s through 50 m POF with a power consumption of 148 mW and a sensitivity of -16.4 dBm for a BER of 10-12.