FIBER OPTIC SENSORS
Optical sensor is a transducer which converts any form of signal into optical signal in the measurable form. Here optical fibers are used as a guiding media and hence called as wave guides. The block diagram of a sensor system is as follows.
The optical sources used here are LED/Laser. The optical signal produced by the optical source and is transmitted through the transmitting fiber in the modulation zone.
The optical signals are modulated based on any one of these properties, viz., Optical intensity, phase, polarization, Wavelength and spectral distribution. These modulated signals with any one of these properties are received by the receiving / fiber and is sent to the optical detector.
1. TYPES OF SENSORS
There are two types of sensors, viz.
i. Intrinsic sensors or Active sensors
ii. Extrinsic sensors or Passive sensors
INTRINSIC SENSORS OR ACTIVE SENSORS
In intrinsic sensors or active sensors the physical parameter to be sensed directly acts on the fiber itself to produce the changes in the transmission characteristics.
i. Temperature /Pressure Sensor( Phase and polarization sensor) and
ii. Liquid level sensor.
In extrinsic sensors or passive sensors, separate sensing element will be used and the fiber will act as a guiding media to the sensors.
i. Displacement sensor
ii. Laser Doppler velocimeter sensor