3 There are three distinct methods typically used for fiberoptic sensors of displacement measurement; Laser interferometry, wavelength modulation, and light intensity modulation. Laser interferometry is based on fringe counting and has high resolution and stability of measurement. It is also known as phase modulated fiberopticsensor. Most interferometricfiberopticsensor use single mode fiber. This type of sensor uses variation of light for detection (Fidanboylu and Efendioglu, 2009). The working principle is that the field system will modify the optical phase of light channel through the fiber for detection purpose. By comparing the phase of light in signal fiber to that in a reference fiber, the phase modulation is considered to be detected interferometrically. The light is divided into two beams; one beam is exposed to the sensing environment and experiences a phase shift and the other is isolated from the sensing environment and is used for as a reference. Once the beams are recombined, they interfere with each other. However, its precision and stability are wavelength dependent (Huimin et al., 2007). Interferometer technique is also quite complicated even though it can provide very good sensitivity (Yasin et al., 2012).
Abstract: In and post a fire event, an accurate and real-time evaluation and monitoring of a structure’s performance can assist firefighters for efficient survivor rescuing, which significantly improve the fire rescuing safety both for fire fighters and the trapped survivors. However, due to the lack of durable sensors, the structural performance of steel structures in fire conditions is challenging to be evaluated in real time, especially when the associated civil structures are in a large scale. In this paper, a fiberopticsensor network is developed and used to monitor the structural performance of the steel structures in high temperature environments. The fiberopticsensor network has the capacity of real-time large strain measurement up to 12% and temperature of up to 700ºC simultaneously. The capability of large strain measurement up to 12% enables the sensor system to monitor the strain distribution of steel structures during fire events in real time. An one-story one-bay steel frame (A36 steel) is used as an example in this paper to perform the structural performance assessment of steel structures in high temperature using the developed sensor network. The simulated fire tests were performed using high temperature furnace through gradual temperature increase from room temperature to 800 °C at a rate of 10 °C/min. The evaluated fiberopticsensor network consists of two long period fiber grating (LPFG) temperature sensors, five movable extrinsic Fabry-Perot interferometric (EFPI) large strain sensors, and two hybrid EFPI/LPFG sensors, which were distributed along the steel frame inside and around the heating zone of the frame. Experimental results demonstrated that the developed sensor network effectively monitored the plastic hinge formation and failure mode of the steel frame, approving the feasibility of the sensor network for steel structure evaluation in high temperature environments.
It is the basis for recognizing between multiple multiplexed sensors and distributed sensors. In sensors distributed there is only one element of the detector, and the objective of signal processing is to obtain measurement as a position element along the sensing component. In contrast, point multiplexing multiplexing comprises measurements of the appropriate dimensions for each discrete detection component. It must be explained that both types of sensors may coincide within the same network, which occur once again in hybrid networks. As far as the type of optical signal is concerned, one can make an initial qualification between the network capable of combining the sensor by using the optic signal level for data transmission (interferometricsensor network), or that relies on classifying the intensity of light (by some multiplexing techniques) which we will call intensity sensor network. It is an equation of this group that is used in most of its established.
There are two types of fiberoptic cables, they are named as the multi-mode fiberoptic cable and single-mode fiberoptic cable. A single-mode fiberoptic cable is a single stand of a glass or plastic fiber where normally have a diameter of 8.3 to 10 microns that allows only one light to propagate. In other words, single-mode fiberoptic relatively have narrow diameter area through which only single mode can propagate typically 1310 or 1550nm. Single-mode fiber carries greater bandwidth than multi-mode fiber, but it require a narrow spectral width of a light source. One of the main advantage of using single-mode fiber is the distance allowance where it allows 50 times longer distance with a higher transmission rate than multi-mode fiberoptic. However, single-mode fiber will costs more due to only single light can propagate in a time. As shown in Figure 2.1b and Figure 2.1c, single-mode fiberoptic has a smaller core diameter than multi-mode fiberoptic. The small core diameter and single light wave will practically eliminate any distortion that might result from overlapping light pulses, hence will provide least signal attenuation and higher transmission speed.
Currently, fiber sensors have expanded in its exploration lines and possibilities with use of nanocoating deposition techniques (El-Sherif et al., 2007; Ascorbe et al., 2016). Nanostructured thin films and nanocoatings have been applied to the optical fibersensor system to fabricate new sensors. In this case, the sensing part, i.e., the sensing section preparation of modified cladding involves two major steps: removal of the cladding of fiber, and coated with of new material which interacts with the surrounding chemicals (Khalil et al., 2004; Nguyen et al., 2016). The thin film of the materials that coated the fibre increases the interaction between the propagating light in the optical fibre with the surrounding chemicals. This coating acts as sensitive material, and therefore its composition and fabrication parameters are thoroughly studied in order to improve sensitivity or other desirable sensing values (Garcia-Ruiz et al., 2016; Rithesh Raj et al., 2016; Zhou et al., 2016).
C) Preparation of fiber for experimental work:Now, 3cm outer plastic jacket has been removed in the middle of 1m fiber, using stripper. The fiber where outer jacket has been removed is immersed in benzene and heated up to 60 ◦ C for about 25minutes. The plastic clad peels off automatically.The bare core where cladding has been removed is washed gently with distilled water and dried for about 30 minutes. The fiber thus prepared is ready to use in the experimental work.
Pulses returned from each FBG contains phase information from preceding adjacent sensors proportional to the fiber strain between two FBG’s on each side of the fiber wound around the mandrel as a result of the acceleration of the mandrel due to the passing seismic wave. Upon returning to the interrogator, each pulse is compared to a reference interferometer, generating an intensity pulse in the interrogator. The resulting intensity pulse is converted to an electrical signal and filtered in the analog front end and then digitized. Once digitized, the electrical signal is demodulated, thus yielding a digital word representative of the instantaneous fiber strain at the sensor. A software demodulation algorithm is then used to ensure a high fidelity output with a low noise floor and large dynamic range. De- multiplexing is accomplished by tracking the pulses in the order received: each from a different sensor. A
ABSTRACT: Fiber optics sensor technology is use to measure different parameters such as strain, pressure, temperature, to detect a large number of toxic substances and other chemical constituents in sea, water and air, detection of various diseases and many more. This report describes the study and design of evanescent wave absorption field sensor and its application of detection of nitrate concentration in water.
following: (1) some of the light exits the core into the cladding and leaks outside the fiber, and/or (2) some of the light gets reflected from the location of deformation back towards the source (see Figure 1). Both phenomena lead to the same overall effect, namely, an attenuation of the light intensity arriving at the opposite end. Conceptually, this resembles pinching the middle of a water hose to reduce the flow. The degree of this light attenuation can be used to indirectly measure the amount/magnitude of the external deformation forces. Komi et. al.  used this technique with multimode bare plastic optical fibers (POF) of 0.3-0.5 mm diameters to investigate tendon forces in rab- bits and humans up to 6000 N. Here the fiber was inserted through the skin, through the entire tendon, then through the skin and outside the body. One end of the fiber was attached to a light source and the other was attached to a detector. Forces were ap- plied to the tendon and transmission losses were measured. Measurements of the inci- dent and transmitted light intensities allowed quantification of the external forces.
7 development gives much better pulverize and effect resistance. It doesn't, be that as it may, shield the fiber too from the worries of temperature varieties. Since the plastic grows and contracts at an alternate rate than the fiber, developments created by varieties in temperature can bring about misfortune delivering microbends. Another preferred standpoint to the tight cradle is that it is more adaptable and permits more tightly turn radii. This favorable position can make tight-tube cradles valuable for indoor applications where temperature varieties are insignificant and the capacity to make tight turns inside dividers is wanted.
For short separation application, for example, a system in an office building, fiber-optic cabling can spare space in link conduits. This is on account of a solitary fiber can convey a great deal more information than electrical links, for example, standard class 5 Ethernet cabling, which ordinarily keeps running at 100 Mbit/s or 1 Gbit/s speeds. Fiber is additionally invulnerable to electrical obstruction; there is no cross-talk between signs in various links, and no pickup of ecological commotion. Non-defensively covered fiber links don't direct power, which makes fiber a decent answer for securing correspondences gear in high voltage situations, for example, power era offices, or metal correspondence structures inclined to lightning strikes. They can likewise be utilized as a part of situations where unstable exhaust are available, without threat of ignition. Wiretapping (for this situation, fiber tapping) is more troublesome contrasted with electrical associations, and there are concentric double central elements that are said to be tap-proof.
Salinity is an important property of industrial and natural waters. It is defined as the measure of the mass of dissolved salts in a given mass of solution. High salinity has an impact on people and industries reliant on water. High levels of salt can reduce crop yields, limit the choice of crops that can be grown and, at higher concentrations over long periods, can kill trees and make the land unsuitable for agricultural purposes. Salinity increases the “hardness” of water, which can mean more soap and detergents have to be used or water softeners installed and maintained. This can also cause scaling in pipes and heaters. The experimental determination of the salt content by drying and weighing presents some difficulties due to the loss of some components. The only reliable way to determine the true or absolute salinity of natural water is to make a complete chemical analysis. However, the method is time consuming and cannot yield the precision necessity for accurate work. Thus to determine salinity, one normally used method involves the measurement of a physical prop- erty such as conductivity, density or refractive index. The paper reports the refractometric fiberopticsensor for detec- tion of salinity of water. The mathematical model is developed for detection of the refractive index of liquid and simu- lated in MATLAB. The fiberopticsensor probe is developed to measure the refractive index of the solution containing different amount of salt dissolved in water i.e. different molar concentrations. Experiments are carried out using the developed probe for these solutions. Experimental results are showing good agreement with the simulated results. Keywords: FiberOptic Chemical Sensor; Hardness of Water; Refractometry; Retro-Reflective Type FiberOptic
concentration. Brake oil is sort of water driven liquid utilized as a part of pressure driven brake and pressure driven grasp applications in vehicles, cruisers, light trucks, and a few bikes. It is utilized to move power into weight, and to enhance braking power. It works since fluids are not apparently compressible in their characteristic express the part particles do not have inside voids and the atoms pack together well, so mass powers are straightforwardly exchanged to pack the liquid's synthetic bonds. Later on, this venture can work in vehicle that utilization Brake Oil and give change in mechanical industry. The innovation and utilizations of optical filaments have advanced quickly as of late. The upsides of fiberoptic sensors are flexibility from Electromagnetic Interference, wide data transfer capacity, conservativeness, geometric adaptability and economy. By and large, FOS is described by high affectability sensor when contrasted with different sorts of sensors. There are the variety types of fiberoptic sensors. These can be named force of tweak and demodulation amplitude process, physical sensor or substance sensor for estimation, extrinsic or intrinsic sensor, and in conclusion arranged because of their estimations focuses.
This work is based on Fresnel reflection at flat interface between two different media which is air and liquid. The sensor system is based on the use of 2x2 single mode fused fiber coupler with different coupling ratio. Two light sources of different wavelength and two optical detectors namely the power meter and the photodiode are used. Reflected light produced from Fresnel reflection at the interface was measured in term of power due to change of liquid refractive index.
Since the invention of laser in 1960’s, a great enthusiasm in optical system has motivated researchers to study the potential of fiber optics for data communications, sensing, and other applications (Fidanboylu and Efendioğlu, 2009). Moreover, the advances toward low-loss optical fiber in the 1970s stimulated further scientific advances, both in telecommunications and in optical fiber sensors. The phenomena had been leading many researches to focus on suitable design of fibers. Therefore, it's become a new thoughts aimed at using optical fibers to design sensing systems, which led to the fiber based sensing devices and components (Gholamzadeh and Nabovati, 2008).
The open loop fiberoptic rotationary sensor is an interferometer where a light source i.e., Super Luminescent Diode (SLD) is divided in to two beams, which propagate along clock wise and counter clock wise paths in optical fibersensor coil and then recombined before being detected by a PIN photodiode based fiber optical receiver. In the presence of rotation, the two beams from the normal source experience distinctive stage moves before recombining on the optical indicator.
A simple fiberoptic humidity sensor is fabricated based on novel polyelectrolyte complex film of the polymers, Chitosan and Carboxy Methyl Cellulose. A small portion of the cladding of the optical fiber is removed and is coated with the hydrogel polymer film. Coating is done using layer by layer technique. This portion is inserted into the region where the humidity has to be monitored. The sensor makes use of the intensity variation of guided light through the plastic optical fiber due to scattering and the phenomenon refractive index variation of the coated hydrogel film. The output power variation is found to be linear, and without hysteresis.
Fiberoptic is now not only focused on telecommunication network as data transmission media. Fibre optic technology alternatives that can replace conventional cable signal function as electrical conductor. Where fibre optic is used as a sensor or with respect to the fibre optic sensors (FOS). Benefit from optical fiber as sensor has many advantages compared with electrical Sensors which have been used for many years. Fibre optic has some advantages, including a small diameter, lightweight, resistant against electromagnetic disturbance, can be used in the period as in included in high temperature or high tensile, high sensitivity and the ability to feel and to send help. In addition, the optical fiber is also not perishable, it has separate the electricity does not easily get fired or explosion as a result of an electron as a stepping stone on the occurrence of an electrical Sensor.
This project proposes to use design of experiment for optimization of fiberoptic distance sensor. The accuracy of normal sensor produces is affected by critical experimental parameters. The effects of these key variables on the fiberoptic distance sensor efficiency were investigated. The low power output on the normal sensor was determined in many industrial area, as responses to that problem, design of experiment (factorial design) is the way that will assist the industrial to get the better output result or more accuracy on their sensor. The accuracy was checked using one standard reference material or variable which are; type of cable used, type of light source used, and distance of the sensor to the target and permittivity for an experiment. Factorial design 2 4 will applied to determine the significant factors that affect the output power.