The document describes a fiber optic temperature measurement technology using gallium arsenide (GaAs) for accurate temperature readings without the need for recalibration due to its stable material properties. It outlines the system's design, which includes components like a light source, optical coupler, and spectrometer, making it suitable for high voltage and hazardous environments, unlike traditional thermocouples. The application of this technology spans various fields, including automotive, medical, and industrial sectors, highlighting its fast response time and immunity to external factors.

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Fiber Optic Temperature Measurement Technology
ï Visible Infrared ð
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OPERATING PRINCIPLE
§ Based on a well known and reproducible phenomenon
o The band-gap variation in the absorption spectrum of the
semiconductor GaAs (Gallium Arsenide) with respect to temperature
§ GaAs can also be looked at as a variable optical filter (low pass)
o Wavelengths towards visible are blocked
o Wavelengths towards infrared are transmitted
§ A Direct Contact temperature sensor
§ GaAs material properties will never change with time, ever !
o No DRIFT…
o No RECALIBRATION…

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Fiber Optic Temperature Measurement Technology
SYSTEM DESIGN
§ The System consists of
§ Light source
§ Optical coupler
§ Rugged Spectrometer
§ Electronics for Data Processing, Storage & Visualization
§ An optical fiber delivers white light to the semiconductor
GaAs sensor glued at the Probe Tip
§ Some of the light is absorbed – Depending on the
temperature of the GaAs Crystal at the Probe Tip
§ The light is reflected by a dielectric mirror and returns
through the same fiber for analysis by the on-board
Spectrometer
§ Highly reliable monitors suited to automotive
environments
GaAs
Sensor
Fiber Optic ProbeOptical
Coupler
Spectrometer
While Light
Source
FIBER OPTIC TEMPERATURE SYSTEM
Dielectric
Mirror
Coating
GaAs Crystal
(Sensor)
Fiber Cladding
Fiber
Core
Injected
Light
Reflected
Light

3. Radio Frequency
(100 kHz up to 10 MHz)
Chemicals:
All pH levels (0 – 14)
High voltage:
Greater than 1200kV
Radiation: Nuclear
Microwave
(300MHz to 300GHz)
Magnetic Field: Greater
than 25 Tesla
Vibration: 10g+ Force
Bio Safe: Sterile Environments
3
§ No Need for Isolation: Highly dielectric strength
§ Avoid complex compensation and Calibration: Immune to Noise
§ Ultra Fast Response: Accurate Thermal Profiling
§ Smaller Size and Intrinsically Safe: Easy to use and handle Sensors
§ Explosion Proof: Suitable for Explosive Environments
Fiber Optic Sensors: Immunity to Environments

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§ Electric vehicles are going to 1000V+, 700A+ for cars and 2400V+, 1000A+ for trucks
§ Traditional thermocouples are too slow and significant limitation above 200V
§ Thermocouple output is in millivolts and gets affected by Electric and Magnetic fields
§ Safety Risk from Thermocouples: Risk of short circuit at higher voltages, Corrosion etc.
§ Thermocouples are Non-Linear: Sensors are non-linear, require complex compensation
§ Thermocouples are large: not suitable to fit into tiny spaces on PCBs, Power Electronics, Charging Points
§ Slower Response: Thermocouples are not fast enough for accurate thermal profiling
§ Variation from Batch to Batch: Impact accuracy and repeatability of testing
§ Susceptible to High Voltage and Magnetic Fields
§ Thermocouples are not suitable for Explosive Environments
§ Thermocouples are not suitable with longer signal cables
Benefits of Fiber Optic Sensors over Traditional Sensors

5. Application for Fiber
Optic Temperature
Sensors
5
Energy/ Utilities
E-Mobility
Medical
RF / Microwave
Industrial
Research Lab
Fiber Optic Temperature Sensors: applications
§ Microwave Heating
§ Microwave Digestion
§ Microwave Ablation
§ RF / Microwave Drying
§ Food Packaging
§ Soil decontamination
§ Glass Manufacturing
§ Process and Control
§ Mining Applications
§ Cryogenic Research
§ Pharmaceutical Research
§ Consumer Product Research
§ Environmental Research
§ MRI Machines / Coils
§ Sensor for Catheters
§ CT scan, PAT scan
§ Clinical Trails
§ Cancer Treatment
§ EV Motors
§ EV Battery Cells
§ EV Battery Module
§ EV Battery Pack
§ Power Electronics
§ Charging Equipment
§ Transformer Winding Hot Spot Monitoring
§ Switchgear Temperature Monitoring
§ Motor Winding Temperature Monitoring
§ Cable Termination Temperature