Sensors developed using fiber optic technology are the frontier of sense. The use of light by these sensors has transformed our understanding and measuring of the world. Fiber optics have no rivals because they can be internal or external sensors communicating over long distances through different fiber amplifier devices. Their small size, in addition to their non-conductivity and immunity from electromagnetic interference, makes them indispensable in high-voltage or volatile environments. Additionally, there are multiplexing features that improve their usability; hence, several parameters can be monitored simultaneously along one fiber.
What are the advantages of fiber optic sensors?
Immunity to Interference:
No disturbance from EMI and RFI, ensuring reliable data collection in noisy environments.
Resilience in Harsh Conditions:
This allows it to be used in extreme vibrations and harsh environments.
High-Temperature Tolerance:
They are safe for temperatures up to 1450 degrees C and corrosive surroundings, making them ideal for critical applications.
Exceptional Sensitivity:
It is sensitive enough to detect the smallest changes, allowing precision measurements in a dynamic environment.
Compact and Lightweight:
Their compactness makes them fit even into any system since they can be easily integrated as per the user’s requirement, thus enhancing versatility.
What are the various applications of fiber optic sensors?
Measurement of Physical Properties:
Strain, displacement, temperature, pressure, velocity, and acceleration in structures of any shape or size.
Real-Time Monitoring of Structural Health:
Monitoring the physical health of structures in real-time.
Buildings and Bridges:
- Concrete monitoring during setting.
- Crack monitoring.
- Prestressing monitoring.
- Spatial displacement measurement.
- Neutral axis evolution.
- Long-term deformation (creep and shrinkage) monitoring.
- Concrete-steel interaction.
- Post-seismic damage evaluation.
Tunnels:
- Multipoint optical extensometers.
- Convergence monitoring.
- Shotcrete / prefabricated vaults evaluation.
- Joints monitoring damage detection.
Dams:
- Foundation monitoring.
- Joint expansion monitoring.
- Spatial displacement measurement.
- Leakage monitoring.
- Distributed temperature monitoring.
Heritage Structures:
- Displacement monitoring.
- Crack opening analysis.
- Post-seismic damage evaluation.
- Restoration monitoring.
- Old-new interaction.
Understanding the Working Principle of Fiber Optic Sensors
Fiber optic sensors are like the contextualization of light, materials, and detection mechanisms that produce accurate measurements and monitoring systems in different applications. So, let us delve into the basic working principles.
Components Overview:
A fiber optic sensor comprises a few vital elements, which include a light source, optical fibre, a sensing element or transducer and a detector. Each component has a unique function that it performs to make the sensor work effectively.
Modulation Mechanism:
The main idea is that the transducer changes some specific parameters within an optical fibre system. By altering intensity, phase, polarization, or wavelength, the encoded information is added to the light being transmitted.
Response Analysis:
This modulation results in well-recognizable changes in an optical signal as it moves along a fiber. Such minute alterations, just similar to trivial disturbances in a controlled environment, can be detected by the receiver of this sensor.
What are the types of fiber optic sensors?
1. Intensity-based fiber optic sensors – These sensors depend on different physical principles, such as evanescent waves or microbending, that cause signal attenuation in the optical fiber cables, leading to signal loss. For these types of sensors, multimode large core fibers are employed, which convert an external force into a decrease in light intensity and can be measured. Microbend sensors cut-off the intensity of light carried through bent fibers occasionally. Evanescent-wave sensors alter the cladding by peeling it off or by applying coating materials that are sensitive to particular chemicals; after the interaction, the sensor remains without any detected reaction product but only changes of some optoelectronic characteristics including absorption spectra, etc., caused primarily by these reactions themselves. Applications range from pressure detection to chemical analysis.
2. Wavelength-modulated fiber optic sensors – The wavelength-modulated fiber optic sensors, however, employ the changes in light wavelengths for detection, including fluorescence, black body, and Bragg grating sensors. Sensing with fluorophores is also used in medicine, biology, chemistry, and industry. A blackbody sensor consists of a cavity heated up by an electrical current that emits radiation; temperature measurement is made by analyzing its spectrum using detectors like photodiodes. The Bragg grating sensor is widely used and has periodic changes in refractive index within the core of the fiber, which acts as an optical filter. From monitoring temperature very precisely to observing the health of structures, these sensors can be used flexibly.
3. Phase-modulated fiber optic sensors In data signals, these sensors are crucial in detecting changes in emitter light. For instance, there are interferometers named Mach Zehnder, Michelson Sagnac, and polarimetric types, just to mention a few. The interferometer configuration involves two paths: one interacts with the sensing environment while the other acts as a reference beam splitter type. The Michelson Interferometer resembles a folded Mach Zehnder set-up but only requires one optical fiber coupler so that twice the optical phase shift per unit length is achieved. Nonetheless, it demands a high-quality reflection mirror to perform optimally.
Summary – Fiber optic sensors represent a significant advancement in sensing technology, offering versatility and precision across industries. Tempsens Instruments (I) Pvt. Ltd. stands out as a leading provider of Thermal and Cable Products, contributing to the evolution of fiber optic sensor technology. With its commitment to innovation, Tempsens Instruments plays a crucial role in shaping the future of sensing applications, ensuring enhanced efficiency and safety across sectors
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