* Question
What are the two major categories of optical fiber in the sensor?
* Answer
1. Intrinsic Optical Fiber Sensors
Definition: The fiber itself acts as the sensing element.
How it works: Changes in temperature, strain, pressure, or other physical conditions directly affect the light propagation inside the fiber—altering intensity, phase, polarization, wavelength, or transit time.
Examples:
Fiber Bragg Grating (FBG) sensors (strain/temperature)
Interferometric sensors (e.g., Mach-Zehnder, Michelson)
Distributed sensors using OTDR (Optical Time Domain Reflectometry)
Applications: Structural health monitoring, oil and gas pipelines, aerospace, and biomedical fields.
2. Extrinsic Optical Fiber Sensors
Definition: The fiber is used to transmit light to and from an external sensing element (outside the fiber).
How it works: The fiber guides light to an external transducer (e.g., pressure-sensitive diaphragm), and back to the detector.
Examples:
Fiber delivering light to a Fabry-Pérot cavity
Sensors for vibration or displacement using external optics
Applications: Harsh environment sensing, medical probes, and high-voltage or electromagnetic environments.
Summary:
Category | Sensing Mechanism | Fiber Role | Typical Use |
Intrinsic | Changes occur within the fiber | Acts as both medium and sensor | Structural, thermal, strain |
Extrinsic | Sensing happens outside fiber | Light carrier only | Pressure, acoustic, biomedical |
These classifications help determine sensor design, sensitivity, and application suitability in optical sensing technologies.
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