Fiber Bragg Grating Technology Research Articles

Design of a Multicast Optical Packet Switch Based on Fiber Bragg Grating Technology for Future Networks

Abstract In this paper, a non-blocking multicast optical packet switch based on fiber Bragg grating technology with optical output buffers is proposed. Only the header of optical packets is converted to electronic signals to control the fiber Bragg grating array of input ports and the packet payloads should be transparently destined to their output ports so that the proposed switch can reduce electronic interfaces as well as the bit rate. The modulation and the format of packet payloads may be non-standard where packet payloads could also include different wavelengths for increasing the volume of traffic. The advantage is obvious: the proposed switch could transport various types of traffic. An easily implemented architecture which can provide multicast services is also presented. An optical output buffer is designed to queue the packets if more than one incoming packet should reach to the same destination output port or including any waiting packets in optical output buffer that will be sent to the output port at a time slot. For preserving service-packet sequencing and fairness of routing sequence, a priority scheme and a round-robin algorithm are adopted at the optical output buffer. The fiber Bragg grating arrays for both input ports and output ports are designed for routing incoming packets using optical code division multiple access technology.

The Study and Applications on Fiber Bragg Grating (FBG) Monitoring System for Deep and Large Deformed Soft Ground

The fiber Bragg grating (FBG) technology is studied based on the current monitoring status of the highway soft ground settlement, for instance, the low degree of automation, the unsatisfied accuracy of the device, the slow data transmission and the greater measurement errors. The limited measuring range and the difficult situations of the soft ground burying and installing of the fiber optic sensor still need to be addressed. This thesis has analyzed the development of the long range optical fiber displacement sensor as well as its burying techniques which are suitable for soft ground settlement monitoring. Both of them have been successfully applied to De Chang Highway D10 subject. The study also shows that the long range optical fiber displacement sensor is able to meet the requirements of the soft ground monitoring. And data can be accurately monitored by means of real-time or on-line continuously. This is of great significance in pushing forward the development of the fiber optical monitoring technology in the field.

Multi-channel monolithic integrated optic fiber Bragg grating sensor interrogator

Fiber Bragg grating (FBG) is a mature sensing technology for the measurement of strain, vibration, acoustics, acceleration, pressure, temperature, moisture, and corrosion. It has gained rapid acceptance in civil, aerospace, chemical and petrochemical, medicine, aviation and automotive industries. The most prominent advantages of FBG are: small size and light weight, distributed array of FBG transducers on a single fiber, and immunity to radio frequency interference. However, a major disadvantage of FBG technology is that conventional state-of-the-art FBG interrogation system is typically bulky, heavy, and costly bench top instruments that are typically assembled from off-the-shelf fiber optic and optical components integrated with a signal electronics board into an instrument console. Based on the industrial need for a compact FBG interrogation system, this paper describes recent progress towards the development of miniature fiber Bragg grating sensor interrogator (FBG-Transceiver™) system based on multi-channel monolithic integrated optic sensor microchip technology. The integrated optic microchip technology enables monolithic integration of all functionalities, both passive and active, of conventional bench top FBG sensor interrogator system, packaged in a miniaturized, low power operation, 2 cm×5 cm small form factor (SFF) package suitable for long-term structural health monitoring in applications where size, weight, and power are critical for operation.

Large-scale geomechanical model testing of an underground cavern group in a true three-dimensional (3-D) stress state

The stability of a large cavern group at great depth is discussed on the basis of large-scale three-dimensional (3-D) geomechanical model tests and numerical simulations. The model tests are described in detail. Improvements in the tests were made in terms of experimental techniques and advanced measurement methods. The model tests utilized active loading on six sides of a rock mass in a true 3-D stress state. During the model construction, precast blocks were fabricated and monitoring holes were defined prior to test initiation. Newly developed combination ball-sliding walls were installed on each of the major loading surfaces to reduce the friction induced by model deformation. A unique grouting and installation technique employing prestressed cables was adopted in the tests. A digital photogrammetric technique, displacement sensing bars using fiber Bragg grating (FBG) technology, and mini multipoint extensometers were developed for measuring deformation. Overloading tests were then conducted for different overburden depths, and 3-D numerical analyses were performed to simulate the testing procedures. Conclusions regarding the stability of the cavern group were developed based on a comparison between the experimental and numerical results.

Polymer coated fiber Bragg grating thermometry for microwave hyperthermia

Measuring tissue temperature distribution during electromagnetically induced hyperthermia (HT) is challenging. High resistance thermistors with nonmetallic leads have been used successfully in commercial HT systems for about three decades. The single 1 mm thick temperature sensing element is mechanically moved to measure tissue temperature distributions. By employing a single thermometry probe containing a fixed linear sensor array temperature, distributions during therapy can be measured with greater ease. While the first attempts to use fiber Bragg grating (FBG) technology to obtain multiple temperature points along a single fiber have been reported, improvement in the detection system's stability were needed for clinical applications. The FBG temperature sensing system described here has a very high temporal stability detection system and an order of magnitude faster readout than commercial systems. It is shown to be suitable for multiple point fiber thermometry during microwave hyperthermia when compared to conventional mechanically scanning probe HT thermometry. A polymer coated fiber Bragg grating (PFBG) technology is described that provides a number of FBG thermometry locations along the length of a single optical fiber. The PFBG probe developed is tested under simulated microwave hyperthermia treatment to a tissue equivalent phantom. Two temperature probes, the multiple PFBG sensor and the Bowman probe, placed symmetrically with respect to a microwave antenna in a tissue phantom are subjected to microwave hyperthermia. Measurements are made at start of HT and 85 min later, when a 6 degrees C increase in temperature is registered by both probes, as is typical in clinical HT therapy. The optical fiber multipoint thermometry probe performs highly stable, real-time thermometry updating each multipoint thermometry scan over a 5 cm length every 2 s. Bowman probe measurements are acquired simultaneously for comparison. In addition, the PFBG sensor's detection system drift over 10 h is measured separately to evaluate system stability for clinical applications. The temperature profiles measured by the two probes simultaneously under microwave HT are in good agreement showing mean differences of 0.25 degrees C. The stability of the detection system is better than 0.3 degrees C with response times of the PFBG sensor system of 2 s for each scan over ten points. The single fixed multipoint fiber thermometry capability compares favorably with the scanning Bowman probe data. This offers an enabling alternative to either scanning or bundled single point temperature probes for distributed thermometry in clinical applications.

Comparative Study on the Elongation Measurement of a Soil Nail Using Optical Lower Coherence Interferometry Method and FBG Method

Optical fiber sensor has gained popularity for structural monitoring in recent decades. Studies on the monitoring for geotechnical structures with fully-distributed fiber sensors, however, are quite limited. In this study, the fully-distributed Lower Coherence Interferometry (LCI) sensors and quasi-distributed Fiber Bragg Grating (FBG) sensors are applied for measuring the strain distribution of a soil nail as a slender structure during pullout test. First, this paper introduces an innovative calibration method for the LCI system. Second, the paper describes the procedures of fiber instrumentation on soil nail. Third, the measured results by LCI technology and FBG technology are compared to study the strain distribution and friction resistance of soil nail during pullout test. Comparative study from test results indicates the characteristics of strain distribution and resistance contribution for different parts of soil nail. Through this study, the advantages and limitations of two sensing technologies are examined.

Improved FBG Polarimeter Design Evaluated Using VCM Extension to Elliptical Polarization

Polarimeters for measuring the Stokes parameters have evolved significantly over the years from a variety of bulk-optic configurations to a number of elegant in-fiber designs. In this paper, we exploit recent advances in tilted fiber Bragg grating (FBG) technology to propose an improved in-line polarimeter that samples more than four detected beams with only two tilted FBGs. Based on theoretical analysis and simulation utilizing an extended formulation of the Volume Current Method (VCM), we demonstrate that this design reduces average Stokes vector errors by 20% for every state of polarization (SOP), facilitating monitoring at lower signal to noise ratios (SNRs).

Bragg system for temperature monitoring in distribution transformers

Heat represents the energy loss occurring in the core and coils of a transformer. The designer must be able to predict the temperature throughout the transformer, in order to correctly determine the amount of copper and silicon steel sheet and the type of cooling ducts and insulation needed to prevent excessive hot spots. This paper presents a pilot design of a distribution transformer monitor using Fiber Bragg Grating (FBG) technology to determine the temperature at 12 points distributed along the LV and HV coils employing three optical fibers. A 100 kV A single-phase distribution transformer was utilized in order to accurately find and measure the hot spot. The thermal equivalent circuit model was built according to the heat transmission process in a transformer. The radiation and convection resistance values of this model are determined iteratively until they border on the FBG measurement results.

Industrialization of advanced optical technologies for environmental monitoring

In this work, an innovative fully integrated monitoring infrastructure based on optical fibre sensors was developed and implemented. In the framework of the research project named PROTEU [Tecnologias Avancadas para a Monitorizacao de Sistemas Estuarinos e Costeiros (PDCTM/P/MAR/15275/1999)], an 11 km optical fibre cable with Bragg sensors each 500 m was installed from the lagoon mouth to Vouga river, along the bed of the Espinheiro channel, allowing the real-time measurement of water temperature at each sensor location. The results of this project are currently feeding several studies concerning Ria de Aveiro and the surrounding area and are crucial for a continuous assessment and management of the environmental conditions. Meanwhile, a fibre optic sensing system for simultaneous measurement of temperature and salinity based on fibre Bragg grating (FBG) technology was also developed. In the following sections, a complete description of the fabrication process, as well as theoretical and experimental results regarding this particular sensing system, are addressed. Earlier in situ local measurements, as well as the latest remote monitoring and data processing scheme, are described. The developed technology is now being exploited by FiberSensing, an INESC Porto spin-off company devoted to the development of optical fibre Bragg grating-based sensor systems for advanced monitoring applications. The main markets of the company are the ones of structural health monitoring in civil and geotechnical engineering, energy production and distribution, and environment.

Digital monitoring for heavy duty mechanical equipment based on fiber Bragg grating sensor

The digital monitoring principle and technologies for heavy duty mechanical equipment based on fiber Bragg grating (FBG) technology are introduced in this paper. The fundamentals of new-style FBG sensing technology, including the photorefractive effect of FBG, the physical formation, and the relation between optical properties and grating parameters, are investigated. The plaster, encapsulation and distribution planning of FBG sensor (FBGS), which is used to monitor heavy duty mechanical equipment under abominable environment and extreme conditions, are also studied. In addition, theoretical and experimental researches on the strain, temperature, displacement, and stress transmission characteristics between FBGS and detection interface are presented. The principle and method for temperature compensation in non-uniformity temperature field are described in detail as well. Comparing with the traditional sensing monitoring techniques, the application of FBGS technology on digital monitoring and diagnosis for heavy duty mechanical equipment has a number of significant technical advantages and will make a new breakthrough in this field.

ＦＢＧを用いた表面貼付型多点圧力センサの開発

An affix-type multipoint pressure sensor was developed by using the Fiber Bragg Grating (FBG) technology. The FBG technology is commonly used in optical communications and is being applied to the stress/strain measurement of a large structure recently. In this paper, the developed pressure sensor by use of FBG and the pressure measurement system are described. The FBG pressure sensor can be stuck on the surface of a body on which pressures will be measured, and is capable of the temperature compensation by using an FBG temperature sensor. The material and diameter of the diaphragm of the sensor and the pre-tension of the fiber were determined according to the pressure measurement test under static pressures. Pressure distributions on a circular cylinder in uniform flow were measured in a circular water channel, where pressures were also measured by a conventional strain-gauge type pressure sensor. Comparing the measured pressures, performances of the FBG pressure sensor are discussed.

ＦＢＧを用いた表面貼付型多点圧力センサの開発

An affix-type multipoint pressure sensor was developed by using the Fiber Bragg Grating (FBG) technology. In the 1st report, the measurement system of FBG pressure sensor was described and the performance was confirmed in a pressure measurement test on a circular cylinder in uniform flow. In the 2nd report, the FBG pressure sensors were stuck on the surface of the fore- and aft-body of a model ship and resistance tests were conducted. The FBG pressure sensor enables to measure the multi-point pressures on curved surfaces of a ship with the temperature compensation. The measured pressures were compared with the result of CFD calculations, and the effects on the ship's resistance were investigated. It was found from the experimental results that the FBG pressure sensor is effective to measure multipoint pressure on the surface of the model ship in resistance tests.

Detection of premature browning in ground beef with an integrated optical-fibre based sensor using reflection spectroscopy and fibre Bragg grating technology

This paper reports on an optical fibre based sensor system to detect the occurrence of premature browning in ground beef. Premature browning (PMB) occurs when, at a temperature below the pasteurisation temperature of 71°C, there are no traces of pink meat left in the patty. PMB is more frequent if poorer quality beef or beef that has been stored under imperfect conditions. The experimental work pertaining to this paper involved cooking fresh meat and meat that has been stored in a freezer for, 1 week, 1 month and 3 months and recording the reflected spectra and temperature at the core of the product, during the cooking process, in order to develop a classifier based on the spectral response and using a Self-Organising Map (SOM) to classify the patties into one of four categories, based on their colour. Further tests were also carried out on developing an all-optical fibre sensor for measuring both the temperature and colour in a single integrated probe. The integrated probe contains two different sensor concepts, one to monitor temperature, based on Fibre Bragg Grating (FBG) technology and a second for meat quality, based on reflection spectroscopy in the visible wavelength range.

Fiber-Bragg-grating-based weigh-in-motion system using fiber-reinforced composites as the load-supporting material

A novel fiber Bragg grating (FBG)-based weigh-in-motion (WIM) system is introduced in order to achieve a better performance compared with the existing WIM systems. This novel WIM system uses the fiber-reinforced composite (FRC) as the load-supporting material in combination with the FBG technology. The sensor is designed as a multiply FRC laminate with the FBG embedded inside it. A theoretical model is developed to analyze the mechanism of this WIM system. Both static and dynamic tests are conducted to verify the system performance. With the extraordinary mechanical properties of the FRC, this novel WIM system has achieved larger dynamic range and higher sensitivity than prior works. The simple design of the system also reduces the engineering difficulties and overall costs.

Focus on sensors

Focus on sensors

Tilt sensor with FBG technology and matched FBG demodulating method

A tilt measurement structure and signal detection method is proposed based on a self-demodulated fiber-Bragg grating (FBG) sensor, which consists of a couple of matched FBGs and a cantilever-based pendulum clinometer. Compared by the typical matched FBGs demodulating method, of which a sensing FBG and a demodulating filter FBG is placed separately, both matched FBGs of this tilt sensor are attached on the upper and lower surface of only one single pendulum-type cantilever element for simultaneous sensing and demodulating. So the received light power will change due to the split of the two reflected spectrum of FBGs, which is corresponding to the tilt angle. In addition, the cross-sensitivity effect of the FBG-based sensor is automatically solved due to a differential signal process method. Experimental results indicate the feasibility of the proposed idea.

101 FBGを利用した圧力センサの開発(2)(OS1-1 光工学による流体計測法の応用と新展開,OS1 光工学による流体計測法の応用と新展開,オーガナイズドセッション)

A film-type pressure sensor was developed based on the Fiber Bragg Grating (FBG) technology. FGB is commonly used in optical communications and is applied to stress/strain measurement recently. One of the merits of this sensor is the easiness to use, and time-varying pressures at multi-points can be measured. Wind tunnel tests were conducted and the pressures of 4 points on the wing model surface were measured. Obtained data were compared with the CFD simulation results and the results of another experiment, and the utility of the sensor was discussed.

Broadband fiber Bragg gratings for dispersion management

This paper provides an overview and technology update of a dispersion management component made from chirped fiber Bragg gratings. The history and technology of fiber Bragg gratings (FBGs) have been extensively covered in several excellent review articles, [1-6] book chapters, [7] and books. [8,9] We give a brief overview of fiber Bragg grating technology in this section and then focus on the details concerned with construction and performance of dispersion management devices in optical communications systems with a single broadband long-length grating used in reflection. Sampled chirped grating are sometimes referred to as broadband devices, but they actually have a narrow bandwidth of operation that is periodically repeated across a given spectral range. Although these periodic devices have shown promise as dispersion management devices in communications systems, they will not be discussed in this paper.

Highly sensitive fiber Bragg grating refractive index sensors

We combine fiber Bragg grating (FBG) technology with a wet chemical etch-erosion procedure and demonstrate two types of refractive index sensors using single-mode optical fibers. The first index sensor device is an etch-eroded single FBG with a radius of 3μm, which is used to measure the indices of four different liquids. The second index sensor device is an etch-eroded fiber Fabry-Pérot interferometer (FFPI) with a radius of ∼1.5μm and is used to measure the refractive indices of isopropyl alcohol solutions of different concentrations. Due to its narrower resonance spectral feature, the FFPI sensor has a higher sensitivity than the FBG sensor and can detect an index variation of 1.4×10−5. Since we can measure the reflection signal, these two types of sensors can be fabricated at the end of a fiber and used as point sensors.

Part 4: Fiber-Optic Sensor and Three-Dimensional Data Applications in Transportation: Using Fiber Bragg Grating Sensors to Monitor Pavement Structures

A new high-resolution temperature and strain sensor with fiber Bragg grating (FBG) technology was developed. The FBG sensor consists of a reference fiber grating and a grating pair scheme that could offer the potential of simultaneous measurement of strain and temperature for monitoring pavement structures. Experimental results showed that measurement errors of ±6 μϵ and ±0.13°C for strain and temperature could be achieved, respectively. Feasible applications of this sensor for monitoring pavement structures were investigated. The reliability and long-term stability tests for this sensor were examined by mounting it on the surface of two kinds of specimens, asphalt and concrete, and several temperature cycles with a designed working temperature range up to 110°C were applied for at least 24 h. An electronic thermocouple and a long-period optical fiber grating (LPG) sensor with similar function were used to compare the performance. Small root-mean-squared temperature variations (better than 1°C) and excell...