The microbend section of the optical fiber is contained in a thermally expansive sheath. It is based on the principle of measuring analog attenuation. Theoretical and experimental aspects of an extrinsic optical fiber ultrasound sensor are described. Handbook of optical sensors optical waveguide sensors. In the case ofgraded index fibre, adjacent guided modes are seperated from each. This type of sensor is able to detect stresses that may have a lasting impact on structures. Abstract a distributed fiber optic moisture sensor based on intrinsic changes in the optical properties of the cladding is reported. Optical fiber can also be used in structural health monitoring. A 10meterlong fiber sensor was fabricated that demonstrated a response to humidity in less than 5 minutes. In this case, the sensor is known as an intrinsic sensor.
Perturbations act on the fiber and the fiber in turn changes some characteristic of. The fiber sensor can be either an intrinsic oneif the modulation takes place directly in the fiber or extrinsic, if the modulation is performed by some external transducer as depicted in fig. This is in contrast to extrinsic sensors, in which the change is outside the fiber and the fiber itself remains unchanged. Intrinsic fiber optic sensor extrinsic sensors are distinguished by the characteristic that the sensing takes place in a region outside the. The distal ends of transmitting and receiving fibers are connected by a small cy lindrical section of an optically clear silicone rubber. Extrinsic and intrinsic types of fiber optic sensors. Textile fiber optic microbend sensor used for heartbeat. This paper traces microbend fiber optic sensors from the early investigative work, into intial applications to mea sure many different parameters, through advanced prototype development and commercial hardware. These types of diaphragms are very reliable and durable in the applications of optical fiber efpi sensor for low acoustic waveshock wave. Us5301001a extrinsic fiber optic displacement sensors. A section of multimode optical fiber sandwiched betw.
We proposed and experimentally investigated a novel microbend sensor structure. A 3db attenuation gives 50%, and 1 db is about 80%. These fibers were selected for their good mechanical behavior. The light beam travels through the core by repeatedly bouncing off the. Pressure sensor based on the fiberoptic extrinsic fabry. It can be a thermooptic, elastooptic, magnetooptic. This causes the wavelengths of the reflected light to change. Intensity modulation induced by microbending in multimode fibers is considered as a transduction mechanism for detecting environmental changes such as pressure, temperature, acceleration, and magnetic and electric fields.
The intrinsic optical fiber sensor has a sensing region within the fiber and light never goes out of the fiber. Pdf fiber optic sensors and their applications researchgate. It is simple, accurate and easily scaled for different sizes and pressure ranges. Sensors which modulate light intensity tend to use mainly multimode fibers, but only monomode cables are used to modulate other light parameters. It can be a thermo optic, elasto optic, magneto optic. Perturbations act on the fiber and the fiber in turn changes some characteristic of the light inside the fiber. In this type of sensors, sensing takes place within the fiber itself. The microbend induced loss in a multimode fibre is given by a k a6 tl3b where bcladding radius, k proportionality constant. About the fiber optic extrinsic sensors extrinsic fiber optic sensors use a fiber optic cable, normally a multimode one, to transmit modulated light from a conventional sensor.
Intrinsic optical fiber sensors are sensors that have a totally di fferent design. A generic microbend sensor has been defined and studied, and its components, such as sensing fiber, light source, optical fiber leads, and detector, have been examined and. Kowalsky, behaviour of intrinsic polymer optical fibre sensor for largestrain applications, meas. A fiber is placed between two plates with rough surfaces. Intrinsic sensors utilize a change that takes place within the fiber itself. About the fiber optic intrinsic sensors intrinsic sensors can modulate the intensity, phase, polarization, wavelength or transit time of light. With extrinsic sensors, light leaves the fiber and is blocked or reflected before going back into the fiberoptic system. Extrinsic opticalfiber ultrasound sensor using a thin polymer film as a lowfinesse fabryperot interferometer. An attenuation of 10 db means that the optical power pl at the end of the fiber is only 10% of the initial power p0. Product segments extrinsic fiber optic sensors, and intrinsic fiber optic sensors. Microbend losses have always been a curse to the fiber optic cable designer, but it is this very same microbend loss effect in optical fibers which was exploited by the microbend sensor designer who adapted the microbend effect to the measurement of many physical parameters and physical variables such as temperature.
This document pdf may be used for research, teaching and private study purposes. Us6671055b1 interferometric sensors utilizing bulk sensing. Depending on the application, fiber may be used because of its small size, or because no electrical power is needed at the. Fidanboylu and others published fiber optic sensors and their applications find, read. Thus by monitoring the decrease in intensity oflight guided through the fibre core, we can construct a pressure or displacement sensor. Jun 01, 1987 a generic microbend sensor has been defined and studied, and its components, such as sensing fiber, light source, optical fiber leads, and detector, have been examined and optimized. Study of multimode extrinsic fabryperot interferometric. An overview of macrobending and microbending of optical.
The extrinsic fizeau fiber optic sensor behaves identically whether it is surface mounted or embedded, which is unique to the extrinsic sensor in contrast to intrinsic fabryperot sensors. The structure is composed of singlemode leads and multimode sensing fiber. This paper reports on a textile fiber optic microbend sensor for heartbeat and respiration monitoring. Apnea detection with microbend fiberoptic sensor 209 the optical. Domaski acultfy of physics, warsaw university of ecthnology, koszykowa 75, 00662 warszawa, poland the paper presents optical ber sensor designed for medical audiometric measurements. However, there are some notable exceptions to this generalization microbend sensor systems, for example. In general, optical fiber sensors may be categorized under two headings according to their operation 24, 23, 24. Extrinsic optical sensor the figure1 depicts extrinsic optical sensor. Intrinsic optical fiber sensor, fiber optic sensors, moh. Additionally, singlemode leads reduce lead noise and allow. Theoretical and experimental aspects of an extrinsic opticalfiber ultrasound sensor are described.
A generic microbend sensor has been defined and studied, and its components, such as sensing fiber, light source, optical fiber leads, and detector, have been examined. This optical fiber sensor was stretched with a micrometer displacement stage while elongation and optical sensor readings were taken. Intrinsic and extrinsic distributed opticalfibre sensors. A corebased intrinsic fiberoptic absorption sensor has been developed and tested for the detection of volatile organic compounds. Intrinsic fiber optic sensor for distributed water detection. Extrinsic opticalfiber ultrasound sensor using a thin. Based on the sensing location, a optical fiber sensor can be classified as extrinsic or intrinsic. Intrinsic polymer optical fibers for large deformation strain sensors. A major feature of extrinsic sensors, which makes them so useful in such a large number of applications, is their ability to reach places which are otherwise inaccessible.
The sensor is based on a thin transparent polymer film acting as a lowfinesse fabryperot cavity that is mounted. A typical attenuation coefficient a against wavelength l is shown in figure 4 for common lowloss fused silica fiber. Sylvain lecler and patrick meyrueis february 22nd 2012. Qingxu yu et al pressure sensor based on the fiberoptic extrinsic fabryperot interferometer 75 light source. Absorption refers to a photon being absorbed by an atom where the photo. The fiber optic sensor has an optical fiber connected to a light source to allow for detection in tight spaces or where a small profile is beneficial. The sensor may be modified to provide a quadrature phase shift extrinsic fizeau fiber optic sensor for the detection of both the amplitude and the relative. A fiber optic 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. Nadir, transformer temperature measurement using optical fiber based microbend. Thus, in addition to all the accepted advantages offered by optical fibres in the sensing function, one has the advantage of a knowledge of the spatial distribution of the measurand.
Extrinsic sensing take place outside of fiber where, fiber. The microbend sensor was one of the earliest fiber optic sensors. 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. Our glass design and coating systems are purposebuilt to satisfy harsh condition installations with longterm reliability. A generic microbend sensor has been defined and studied, and its components, such as sensing fiber, light source, optical fiber leads, and detector, have been examined and optimized. An fbg is an intrinsic sensor that has a regular series of reflective structures in the fibre that are affected by stretching or squashing the fibre. Optical fiber is an intrinsic part of the lighttransmitting concrete building product litracon. This is one of the best optical sensor technologies. Extrinsic optical fiber sensor for medical audiometric applications k. Intrinsic fiber optic sensor extrinsic sensors are distinguished by the characteristic that the sensing takes place in a region outside the fiber as shown in fig. An example is a pressure sensor based on microbending of the fiber. In particular, the present invention includes a gradedindex optical fiber directing steady light through a section of the optical fiber containing a plurality of permanent microbends. Abstractfiber optic sensor technology offers the possibility of sensing.
Finally, the generic microbend sensor has been tested demonstrating good performance. Ppt an introduction to fiber optic sensors powerpoint. Design and modeling of a fiber optical sensor for liquid. Kiesel, intrinsic, singlemode polymer optical fiber sensors for.
Intrinsic polymer optical fibers for large deformation. However, there are some notable exceptions to this generalizationmicrobend sensor systems, for example. Extrinsic optical fiber sensor for medical audiometric. Application of a fiber optic distributed strain sensor. Fiber optic extrinsic fabryperot interferometric sensor for. Fundamentals and applications september, 2015 david krohn, ph. Advantages and disadvantages of microbend sensors are discussed. Optical fiber and optical fiber cable specifies the attenuation at 1550 nm is not to exceed 0. Corebased intrinsic fiberoptic absorption sensor for the. The proposed structure exhibited a level of sensitivity as much as six times higher than that of the classical microbend sensor configuration when the same sensing fiber was used. The present invention is directed toward an interferometric sensor that permits the simultaneous measurement of a change in more than one environmental condition.
Fibre optic sensorst intrinsic sensors extrinsic sensors in intrinsic sensors, the physical parameter or effect to be sensed modulates the. Optical fiber sensors offer attractive characteristics that make. Microbend loss sensor intrinsic in an optical waveguide, a sharp curvatures involving local axial displacements of a few micrometers and spatial wavelengths of a few millimeters. A temperature sensor is made of optical fiber into which quasisinusoidal microbends have been permanently introduced. Introduction to fiber optic sensors and their types. Samples with embedded optical fibers are braided through fourstep method and processed through resin transfer molding rtm process. Volume ii, issue vii, july 20 ijltemas issn 2278 2540. In an optical waveguide, a sharp curvatures involving. On the other hand, in an intrinsic fiber optic sensor. The interferometric sensor comprises an optical fiber and a plurality of sensing regions positioned in an operable relationship to the optical fiber. Pdf on feb 22, 2012, sylvain lecler and others published intrinsic optical fiber sensor. Extrinsic fabryperot interferometer system using wavelength. In an intrinsic optical fiber sensor, the transducer converts the physical value to be measured into an optical information.
Optical pressure sensors the design engineers guide. In particular, it uses an optical fiber as the sensing element, called an intrinsic sensor, or uses it to transport signals from the. Depending on the application, fiber may be used because of its small size. Optical losses extrinsic fiber losses bending losses. A particularly useful feature of intrinsic fiber optic sensors is that they can, if required, provide distributed sensing. The sensor is composed of a sensing diaphragm with a hard center, a microbend modulator a pair of tooth plates, sensing and reference fibres, adjusting bolts, a stainless steel housing, emittingdetecting devices and signal processing circuits. Extrinsic optical sensor vs intrinsic optical sensor. Whether you need a fully distributed intrinsic sensor.
In this cases, the fiber just acts as a means of getting the light to the sensing location. Feb 01, 1996 extrinsic optical fiber ultrasound sensor using a thin polymer film as a lowfinesse fabryperot interferometer. Hundreds of oil and gas wells uses downhole fiber optic sensor systems, platforms begin to use fiber optic shm systems thousands of systems are deployed for many high value oil and gas wells, fiber optic shm mandated on some oil platforms 11 extrinsic fiber optic sensors 12 intrinsic fiber optic sensors fundamental components. Intrinsic optical fiber sensor 55 optical fiber sensor is a system where information is created in the optical path way due to an interaction with a physical phenomenon to be measured and before its transmission to a detector using one or several optical fibers. Extrinsic fiber optic sensors use a fiber optic cable, normally a multimode one, to transmit modulated light from a conventional sensor such as a resistance. Extrinsic or intrinsic sensors are another classification. If the optical fiber is only used to transmit the light, we talk about an extrinsic. A fiber optic sensor is a sensing device that uses fiber optic technology for measuring physical quantities such as temperature, pressure, strain, voltages and acceleration, to name a few.
Finally, the generic microbend sensor has been tested demonstrating. Us5419636a microbend fiberoptic temperature sensor. In general, singlemode fiber is used for intrinsic optical fiber sensors such as interferometric methods, whereas multimode fibers tend to be used in extrinsic sensor systems and transmit the light to and from the sensor head. In an extrinsic fiber optic sensor the fiber is simply used to carry light to and from an external optical device where the sensing takes place. The fresnel reflection from the glassair interface at the front of the air gap reference reflection and the reflection from the airglass interface at the far end of the. When light beam leaves the fiber cable and get changed due to object before it reaches to the optical detector end then it is known as extrinsic optical sensor. In an intrinsic optical fiber sensor, the tran sducer converts the physical va lue to be measured into an optical information. 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. Simultaneous measurement of temperature and pressure with. An overview of macrobending and microbending of optical fibers. The fiber sensor can be either an intrinsic oneif the modulation takes place directly in the fiberor extrinsic, if the modulation is performed by some external transducer as depicted in fig. Help us write another book on this subject and reach those readers. Fiber optic extrinsic fabryperot interferometric sensor 575 fabricated and tested made of metal diaphragm and a single mode optical fiber11 for the measurement of static pressure.
The distance l can be measured with this type of optical sensor as shown. It is important to understand the difference between absorption, attenuation and scattering, all of which refer to the loss of light intensity while propagating along a fiber. Introduction as one kind of intensity modulation sensors, microbend fiber optic sensors utilize intensity loss resulting from optical fiber bending to measure change of environmental parameters, e. Pdf apnea detection with microbend fiberoptic sensor. An extrinsic fizeau fiber optic sensor comprises a singlemode fiber, used as an inputoutput fiber, and a multimode fiber, used purely as a reflector, to form an air gap within a silica tube that acts as a fizeau cavity. Information in each type sensor can be conveyed by polarization, phase, frequency, wavelength, and intensity modulation, or a combination of the above. Whether you need a fully distributed intrinsic sensor fiber for oil and gas operations monitoring, a composite. Phase change of a light wave through an optical fiber of. The optical fiber consists of the core and the cladding, which have different refractive indexes.