The general concepts associated with intensity modulation include transmission, reflection, and microbending. Schemes for referencing of intensitymodulated optical. The sensor principle itself is very simple when based on coupling between fibres, and coupling based intensity modulated sensors have found applications over a long time, mainly. In this work, we fully characterize sensors designed with a 2 khz characteristic resonance, experimentally. However radiant signals embrace a wider field than that of optics so there are a few examples of certain forms of radiant energy being capable of modulating optical systems eg the cherenkov effect. An intensitymodulated optical fibre displacement sensor with. The sensor is constructed using single mode fiber smf and multimode fiber mmf. Intensity modulated sensors were defined in chapter 2 as sensors that detect the variation of the intensity of light associated with the perturbing environment. Osa intensitymodulated directional torsion sensor based on. The change in colour is proportional to the changes in the absorption, transmission, reflection, or luminescence of the optical signal, whereas the polarization is related to the strain birefringence.
Pdf intensitymodulated optical fiber sensors based on. Intensity modulated fiber optic sensor for health monitoring applications. The development of a dual wavelength referenced intensity modulated optical fiber sensor system is described. This document pdf may be used for research, teaching and private study. Zehnder interferometer mzi is proposed and demonstrated. Intensitymodulated optical fiber sensors based on chirpedfiber bragg gratings 253 measured, etc, but excluding transmission loss of the grating. Evanescent field modulated magnetic immune sensor based on magnetic fluid and polymer optical fiber abstract. Biomechanics, fiber optic sensors, intensitymodulated sensors.
Schemes for referencing of intensitymodulated optical sensor systems. Research on fbgbased sensor networks and their coexistence. Intensity modulated fiber optic sensors have the many distinct advantages associated with fiber optics that makes them suitable for several industrial and military applications. The intensity of light coupled into the receiving fiber is shown in fig.
Time emitted beam intensity unmodulated noncontact detection. Paulo roriz et al fiber optic intensitymodulated sensors. Intensitymodulated sensors were defined in chapter 2 as sensors that detect the variation of the intensity of light associated with the perturbing environment. Major strategies are investigated using a simple analytical approach to assist in the evaluation of. Phase modulation sensors and interferometric sensors. Market forecasts and trends for the usage of fiber optical sensors confirm that demand for them will continue to increase in the near future. Intensity modulation is one of the simplest to measure because it only requires a photodetector to measure the light intensity. In order to examine modulating techniques in a logical way it is usual to classify them as five separate effects resulting in change of intensity. Intensitymodulated fiberoptic voltage sensors for power.
Here, one of the physical properties of light signal may be in the form of frequency, phase, polarization. Referencing strategies for intensity modulated optical fibre. Common referencing techniques used to provide immunity against the undesirable variable optical losses in analogue intensity modulated optical fibre sensors are described. Jan 15, 2020 we design, test, and analyze fiberoptic voltage sensors based on optical reflection from a piezoelectric transducer. The development of a dual wavelength referenced intensitymodulated optical fiber sensor system is described. This article focuses on the research of fiber bragg grating fbg sensor network, their applications in iot and structural health monitoring shm, and especially their coexistence with existing fiber optical communication system infrastructure.
The type of these fiber sensors intensity modulated sensors were introduced in the early 60s 510. Apparatus and method for selfreferencing and multiplexing light intensity modulating fiber optic sensors provides a pulsed or chirped source light beam. Muller, smartphone technology applied in an approach for multiplexing of fibre optic intensitymodulated macrobend based sensors, in 26th international conference on optical fiber sensors, osa technical digest optical society of america, 2018, paper tue82. Us4777661a apparatus and method for selfreferencing and. This phase modulation is then detected interferometerically, by comparing the phase of the light in the signal fiber to that in a reference fiber. Fiber optic sensors fundamentals and applications, fourth edition, 2014 available at. Intensitymodulated fiber optic sensor for health monitoring. Paper open access pressure mapping system development based. Interferometeric fiber optic sensors the optical phase of the light passing through the fiber is modulated by the field to be detected. Frequency domain techniques are useful tools to characterize processes occurring on different time scales in solar cells and solar fuel devices. Intensitymodulated optical fiber sensors based on chirpedfiber bragg gratings article pdf available in photonic sensors.
Theory and applications of coupling based intensity modulated. A highly sensitive intensitymodulated optical fiber magnetic. A noncircular symmetric perturbation is created to excite noncircular symmetric cladding mode and then interference with the core mode at the second perturbation. Photoelectric sensors pressure sensors flow sensors inductive proximity sensors displacement sensors. Research article intensitymodulated fiber optic sensor for health monitoring applications. Evanescent fieldmodulated magnetic immune sensor based on. Kitching1 1time and frequency division, national institute of standards and technology, 325 broadway, boulder, colorado 80305, usa 2university of colorado, boulder, colorado 80309, usa we demonstrate an optically pumped 87rb magnetometer in a. A common form of the intensitymodulated optical fibre sensor performs its measurement by making use of a pair of straight optical fibres with a plane reflector. A highly sensitive and simple design of intensity based magnetic field sensor is proposed and experimentally demonstrated with a safe data transformation by employing optical fiber as a magnetic resonancecompatible sensor. A reflective intensitymodulated fiberoptic sensor based on microelectromechanical systems. Evanescent fieldmodulated magnetic immune sensor based on magnetic fluid and polymer optical fiber abstract. Intensity modulation an overview sciencedirect topics. Intensitymodulated photocurrent spectroscopy and its. Mbs transmission 1985 1st industrial applications and military systems advent of single mode systems.
Phase modulated sensors are much more accurate than intensity modulated sensors. For over a decade, intensity modulation has remained one of the most extensively investigated forms of optical signal modulation for sensing applications 110. Wavelength modulated fibre optic sensors among these modulation techniques, the first three modulation schemes are most commonly employed in a wide range ofapplications. Phase modulated sensors are much more accurate than intensitymodulated sensors. Muller, smartphone technology applied in an approach for multiplexing of fibre optic intensity modulated macrobend based sensors, in 26th international conference on optical fiber sensors, osa technical digest optical society of america, 2018, paper tue82. Referenced intensitymodulated optical fiber sensor system. Intensitymodulated photocurrent spectroscopy imps is one such technique that links the electrical and optical responses of the device. This sensing scheme is very cost effective, as the temperature can be directly quantified from photodetector voltage measured at the filter output. An optically modulated zerofield atomic magnetometer with. Sensors free fulltext memsbased reflective intensity. Pdf mathematical modeling of intensitymodulated bent. Depending on the application, fiber may be used because of its small size, or because no electrical power is needed at the.
Victor giurgiutiu, in structural health monitoring of aerospace composites, 2016. Appendix 1 gives examples of the types of modulating signals used for measurement purposes and most of these have been applied to modulate light in fibre. An initial rotation angle is designed between two perturbations for the. Mathematical modeling of intensitymodulated benttip optical fiber displacement sensors. Intensitymodulated sensors vary the output light intensity with respect to the measur and. Theory and applications of coupling based intensity. In this paper, a novel differential reflective intensity optical fiber angular displacement sensor was proposed. This approach provides the highest sensitivity for a transmissive sensor. Among them are those manipulating the change in light intensity coming out of the fiber as portion of the fiber is subjected to physical or chemical change.
A major benefit of extrinsic sensors is their ability to reach places which are otherwise inaccessible. Intensity modulated fibreoptic sensors normally require only lowcost monitoring systems principally based on light emitting diodes and photo diodes. The intensity modulation by the measurand can be made by creating leakages during the transmission, that is to say by bringing light out of the optical fiber. The intensity of the light wave traveling through an optical fiber can be modified by microbending of the optical fiber, by a change in coupling of the fiber with the.
A highly sensitive intensitymodulated optical fiber. By controlling the physical dimensions of the device, we can tune the frequency of its natural resonance to achieve a desired sensitivity and bandwidth combination. For this class of sensors a normalized modulation index m can be defined as where, i change in optical power as a result of modulation by the measurand. A fiberoptic sensor is a sensor that uses optical fiber either as the sensing element intrinsic sensors, or as a means of relaying signals from a remote sensor to the electronics that process the signals extrinsic sensors. The shown figure gives an idea about how the light intensity work as a sensing parameter as well as how this arrangement makes the fiber to work as a vibration sensor. Optical fiber sensors intensity modulation sensors.
Major strategies are investigated using a simple analytical approach to assist in the evaluation of each scheme for its referencing effectiveness. Schemes for referencing of intensitymodulated optical sensor. Fibre optic intensity modulated sensors springerlink. We theoretically and experimentally demonstrated an optical fiber magnetic field sensor based on a singlemodemultimodesinglemode sms structure immersed into the magnetic fluid mf. Fiberoptic magnetic field sensing is an important method of magnetic field monitoring, which is essential for the safety of civil infrastructures, especially for power plant. In optical communications, intensity modulation im is a form of modulation in which the optical power output of a source is varied in accordance with some characteristic of the modulating signal.
Although, the accuracy of the sensor is far less that for interferometric sensors, the accuracy is more than sufficient for most process control situations. Although intensity modulated optical fiber sensors have been fabricated in many different designs and with varying degrees of complexity, the essential building blocks of a simple optical fiber sensor system are depicted in fig. The sensors depend on the properties of the optical fiber itself to convert an environmental action into a modulation of the light beam passing through it. Mathematical modeling of intensity modulated benttip optical fiber displacement sensors. Although intensitymodulated optical fiber sensors have been fabricated in many different designs and with varying degrees of complexity, the essential building blocks of a simple optical fiber sensor system are depicted in fig. Intensitymodulated temperature sensor based on fiber. Intensity based fiber optic sensors require more light and these sensors use a multimodelarge core fibers.
In an optical interferometer the reference and phase modulated light are combined and detected using a photodetector. Pdf intensitymodulated fiber optic sensor for health. The sensor is constructed using single mode fiber smf and. Intensity amplitude sensors in this case, the signal to be measured the measurand, intensity amplitude modulates the light carried by an optical fiber. Microbend optical fiber sensors have been explored for physical and chemical detection of parameters such as pressure, strain, displacement, vibration, temperature, intensitymodulated microbend fiber optic sensor for respiratory monitoring and gating during mri doreen lau, zhihao chen. Osa smartphone technology applied in an approach for.
The envelope of the modulated optical signal is an analog of the modulating signal in the sense that the instantaneous power of the envelope is an. The system utilizes a single broadband led source whose emission is spectrally sliced to provide two separate narrowband wavelength signals, one as the measurand and a second as the reference. A common form of the intensity modulated optical fibre sensor performs its measurement by making use of a pair of straight optical fibres with a plane reflector. An intensitymodulated optical fibre displacement sensor. Modeling of light intensity modulated fiberoptic displacement sensors. The sensor consists of two multimode optical fibers with a spherical end, a quartz tube with dual holes, a silicon sensitive diaphragm, and a high borosilicate glass substrate hbgs. There are three basic techniques to create these leakages. Modeling of light intensitymodulated fiberoptic displacement sensors. Handbook of optical sensors optical waveguide sensors. A reflective intensity modulated fiberoptic sensor based on microelectromechanical systems mems for pressure measurements is proposed and experimentally demonstrated. A novel intensitymodulated optical fibre displacement sensor with convex reflector technology is described.
Osa intensitymodulated directional torsion sensor based. Intensitymodulated optical fiber sensors based on chirped. Intensitymodulated microbend fiber optic sensor for. Microbend optical fiber sensors have been explored for physical and chemical detection of parameters such as pressure, strain, displacement, vibration, temperature, intensity modulated microbend fiber optic sensor for respiratory monitoring and gating during mri. We design, test, and analyze fiberoptic voltage sensors based on optical reflection from a piezoelectric transducer. A technique is described which provides a linear pulse. Out of these, the intensity modulated sensors offer the virtues of simplicity of construction, reliability, low cost and their compatibility to the multimode fibre technology. Memsbased reflective intensitymodulated fiberoptic. For this class of sensors a normalized modulation index m can be defined as where, i change in. In this case, the signal to be measured the measurand, intensity. A reflective intensitymodulated fiberoptic sensor based on microelectromechanical systems mems for pressure measurements is proposed and experimentally demonstrated.
The intensity of the light wave traveling through an optical fiber can be modified by microbending of the optical fiber, by a change in. The simulation model included optical sensor network, which is combined with 8channel intensity modulated wavelength division multiplexed wdm fiber optical data transmission system, where one shared 20 km long itutg. Intensitymodulated fiberoptic sensors are the most widely studied fiberoptic. A fixed phase bias of 2 is introduced in the reference arm with the help of a piezoelectric modulator so that the output variation is linear. In this letter, we demonstrated an intensitymodulated directional torsion sensor based on an inline machzehnder interferometer in singlemode fiber. This sensor can directly measure the angular and axial linear displacement of a flat surface. A novel intensity modulated optical fibre displacement sensor with convex reflector technology is described. Pdf mathematical modeling of intensitymodulated benttip. Pdf modeling of light intensitymodulated fiberoptic. Fundamentals and applications september, 2015 david krohn, ph. The envelope of the modulated optical signal is an analog of the modulating signal in the sense that the instantaneous power of the envelope is an analog of the characteristic of interest in the. Referencing strategies for intensity modulated optical. One obtains an interference equation which has a sinusoidal dependence. Memsbased reflective intensitymodulated fiberoptic sensor for.
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