A novel liquid-level sensor based on a fiber Bragg grating and carbon fiber composite diaphragm is proposed and demonstrated. The sensing principle and finite element analysis result are described. Because the carbon fiber composite diaphragm's thickness is 0.2 mm and thinner than that of other materials, the sensitivity of the liquid-level sensor is improved. The experimental results show that sensitivity can reach 0.185 nm/m of water height. Based on the high sensitivity and the simple structure of the sensor, this sensor can find applications in the area of liquid level sensing.
A novel liquid-level sensor based on fiber Bragg grating and carbon fiber composite diaphragm is proposed and
demonstrated. The sensing principle and finite element analysis result are described. From the experimental result, this
sensor shows high sensitivity and good repeatability. This sensor can find applications in the area of the liquid level
sensing.
Recently, many accidents were reported that some passengers were unfortunately restrained and killed at the gaps
between the Platform Screen Doors (PSDs) and the doors of the subway trains. In this paper, one proposal of real time
monitoring system based on optical time domain reflectrometer (OTDR) to detect the intrusions at these gaps is
presented. In this method the locations and weight of intrusions can be obtained by detecting the abrupt power loss of
backscattering light caused by the weight of intrusions upon the microbending sensor heads. This method can be easily
multiplexed and extended into a multi-function sensing system, such as monitoring the temperature, smoking and the
strains in the tracks, or applied in other fields, such as escalators, board gates for ferries or planes.
A high speed, portable, multi-function WIM sensing system based on Fiber Bragg Grating (FBG) technology is reported
in this paper. This system is developed to measure the total weight, the distribution of weight of vehicle in motion, the
distance of wheel axles and the distance between left and right wheels. In this system, a temperature control system and a
real-time compensation system are employed to eliminate the drifts of optical fiber Fabry-Pérot tunable filter. Carbon
Fiber Laminated Composites are used in the sensor heads to obtain high reliability and sensitivity. The speed of tested
vehicles is up to 20 mph, the full scope of measurement is 4000 lbs, and the static resolution of sensor head is 20 lbs. The
demodulator has high speed (500 Hz) data collection, and high stability. The demodulator and the light source are packed
into a 17'' rack style enclosure. The prototype has been tested respectively at Stevens' campus and Army base. Some
experiences of avoiding the pitfalls in developing this system are also presented in this paper.
A high speed, high performance, portable, dual-channel, optical Fiber Bragg Grating demodulator based on fiber Fabry-
Pérot tunable filter (FFP-FT) is reported in this paper. The high speed demodulation can be achieved to detect the
dynamical loads of vehicles with speed of 15 mph. However, the drifts of piezoelectric transducer (PZT) in the cavity of
FFP-FT dramatically degrade the stability of system. Two schemes are implemented to improve the stability of system.
Firstly, a temperature control system is installed to effectively remove the thermal drifts of PZT. Secondly, a scheme of
changing the bias voltage of FFP-FT to restrain non-thermal drifts has been realized at lab and will be further developed
to an automatic control system based on microcontroller. Although this demodulator is originally used in Weight-In-
Motion (WIM) sensing system, it can be extended into other aspects and the schemes presented in this paper will be
useful in many applications.
An optical fiber pressure sensor based on fiber Bragg grating (FBG) and metal bellows is presented in this paper. Due to
the lower spring rate of metal bellows, the sensitivity is improved to 48pm/kPa. The relationship between Bragg
wavelength and the applied pressure is derived. Experimental data indicates that there is good linear relation between the
Bragg wavelength shift and the applied pressure. This sensor can be utilized in low pressure measurement.
A novel structure of an optical fiber pressure sensor based on a fiber Bragg grating (FBG) and metal bellows is presented. Due to the novel structure, the sensitivity is improved to 48 pm/kPa. The relationship between Bragg wavelength and the applied pressure is derived. Experimental data indicates that there is a good linear relation between the Bragg wavelength shift and the applied pressure. This sensor can be utilized in low-pressure measurement.
A portable, multi-function WIM sensing system based on Fiber Bragg Grating (FBG) technology is developed to
measure the total weight, the distribution of weight of vehicle in motion (the weights of left front, right front, left rear
and right rear wheels respectively), the distance of wheels axles and distance between left and right wheels. Currently the
speed of vehicle to be tested can be up to 15 mph, the full scope of measurement for this system is 4000 lbs, and the
static sensitivity of sensor head is 20 lbs. This system has been tested respectively at Stevens' campus and Army base.
Compared to other schemes, our method has a number of advantages such as immune to electromagnetic interference,
high repeatability, lightweight, low power consumption, high sensitivity to dynamic strain caused by load of vehicles in
high-speed. The accuracy of whole system can be improved by simulating the mathematical model of sensor heads and
improving the quality of manufacture as well as the calibration condition in the future.
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.
In this weigh-in-motion (WIM) research, we introduce a novel design
of WIM system based-on fiber Bragg grating (FBG) technologies. The
novel design comes from the idea using in-service bridge as the
weigh scale. While vehicles traveling over the bridge, the weights
can be recorded by the strain gauges installed on the bridge
abutments. In this system, the bridge beam is replaced by a piece of
steel plate which supports the weight of the traveling vehicle. Four
steel tubes are attached firmly at the corners of the plate serving
as the bridge abutments. All weights will be finally transferred
into the tubes where four FBGs are attached and can record the
weight-induced strains by shifting their Bragg wavelengths.
Compared with other designs of fiber-optic WIM systems, this design
is easy and reliable. Especially it's suitable for heavy vehicles
because of its large capacity, such as military vehicles, trucks and
trailers. Over 40-ton load has been applied on the system and the
experimental results show a good repeatability and linearity under
such a large load. The system resolution has been achieved as low as
10 kg.
This paper introduces a novel design of "bridge style" fiber-optic
weigh-in-motion (WIM) sensor using fiber Bragg grating (FBG)
technology. Compared with other designs of fiber-optic WIM sensors,
the bridge-style design is reliable, sensitive and can bear more
loads. With these advantages, the bridge-style WIM sensor is
specifically suitable for heavy vehicle dynamic weighing, especially
for military vehicles, cargos and equipments. Experiment is
conducted and the results show good repeatability and sensitivity
under large loads. The minimum achieved resolvable weight is 7.1
kilograms. Finally, WIM sensor on-site installation method is
suggested.
This paper introduces a novel application of fiber microbending
sensor to monitor the highway vehicles, i.e. overtime pull-over
vehicles. Precise locations and durations of the overtime pull-over
vehicles can be detected and alarms can be sent to highway
administrators. Highway administrators can use these data to
maintain the traffic order, secure the passengers and enforce the
law. The sensor is designed based on fiber microbending effect and
optical time-domain reflectometry method is utilized to generate,
collect and process the optical signals. The experiment is designed
to simulate the highway shoulder with vehicle parking on it.
Different vehicle weight-induced fiber microbending losses are
detected and measured. By the optical time domain reflectometry
technique, the precise locations of pull-over vehicles have been
obtained.
An optical-fiber-based gas sensor for CH4 gas real-time monitoring has been developed and tested. A long-distance
silica fiber link with compact single-path or multi-path gas cells has been employed in conjunction with a wavelength-tunable.
InGaAsP DFB laser diode at 1.64μm (at the R(6) absorption peak of methane) to achieve highly sensitive remote interrogation of CH4 with potential application in the mining complexes and residential areas. By wavelength modulation with the DFB laser diode, multi-path gas cell and a self-design processing circuit, sensitivities of less than 1% of lower explosive limit (LEL) had been achieved in the laboratory.
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