Fiber Optic Sensors are becoming popular in various industries for their distinctive properties as compared to the traditional sensors. Fiber Optic Sensors uses Optical fiber as the sensor which transmits the signals to the Data Acquisition and Processing system, which calculates the value of the physical parameter to be measured. These systems utilize effect of change in the properties of the light travelling through the fiber like wavelength shift and since the fiber is a passive sensor, it does not require any electrical power to operate, it can be installed in intricate places.
The major advantage of adapting fiber optic sensors over conventional sensors is that the signals are purely in the form of light signals rather than electric signals, so the fiber optic sensors can be used in areas with High Electromagnetic Radiations or Radio Waves and being a good insulator, they find applications in High Current areas such as Transformers, Switchgears etc.
Types of Fiber Optic Sensors :
Based on the number of sensing points and applications, there are 3 types of Fiber Optic Temperature Sensors that we offer :
- Fluorescence Based Temperature Monitoring System (FluoroSenz)
- Fiber Bragg Grating (FBG) Monitoring System (BraggSenz)
- Raman Based Distributed Temperature Monitoring System (DTSenz)
Fluorescence Based Temperature Monitoring System (FluoroSenz)
It is a single point contact based temperature sensor, which is based on the principle of Time Decay of Fluorescence of a rare earth fluorescent material. When the sensitive Rare Earth Material is stimulated by a Pulsed Light Source, electrons inside the sensitive rare earth material absorb photons, causing electrons to move from a low to a high state of excitation. Once the light source has dissipated, the rare earth material emits photon and get back to ground state from its excited state. The time taken by the Rare Earth Material to reach to ground state from excited state is known as “Fluorescence Lifetime” which depends upon the temperature.
The major advantage of this principle is that the monitoring is dependent only on the time of the excited fluorescence and it is independent of the intensity, transmission loss or optic coupling efficiency.
Fiber Bragg Grating Monitoring System (BraggSenz)
BraggSenz is a user-defined multipoint contact based sensor, which is based on the principle of Wavelength Shift of light reflected by grating created in the core of single mode optical fiber by appropriate exposure to ultraviolet light, this grating is known as Bragg Grating. When a broadband light is transmitted through the fiber, most of the wavelengths will pass through but a certain wavelength will reflect depending upon the expansion or contraction of Bragg Grating which is known as Bragg Wavelength.
The working wavelength range of each individual fiber Bragg grating sensor and the total wavelength range that the FBG interrogator can interrogate determine the number of sensors that can be attached to a single fiber.
FBG Sensors have a wide application range like Structural Health Monitoring, Commercial Transportation Monitoring, Hydro Power plant Monitoring, Aerospace Industry for measuring temperature, strain, vibration
Raman Based Distributed Temperature Monitoring System (DTSenz)
DTSenz or Distributed Temperature Monitoring System is a linear temperature monitoring system that works on the principle of Raman Scattering that occurs when the light from the source travels along the fiber. Raman Scattering is an intrinsic property of fiber ie. No additional sensor needs to be formed on the fiber.
When light source (laser) strikes an optical fiber, the fiber glass molecules scatter the light as it propagates down the fiber, exchanging molecules with lattice vibration. There occur Raman scattering which has two components; stokes signal and anti-stokes signal. Raman Scattered signals get reflected back to transmitted end where they are analyzed. The intensity ratio of backscattered anti-stokes and stokes signals help in determining temperature at point. Measurement of arriving time at transmitting end is used to get position of temperature reading using OTDR (Optical Time Domain Reflectometry).
DTSenz has a high potential application where temperature over long distances needs to be measured like Pipelines, Conveyor Belts, Tunnels, Reactor Skin Temperature Monitoring.
Advantages of Fiber Optic Sensors
- Optical Fibers are Robust and suitable for day to day use.
- They are flexible in nature allowing them to be installed at intricate locations
- Unlike metal parts, they are insensitive to Electric Current, Electromagnetic Radiations such as Microwaves and RFI.
- They can also be used in High Voltage areas such as Power Grid, Switchgears etc.
- They are immune to corrosion and are inert to most of the chemicals