02-11-2012, 05:25 PM
Fundamental of Fiber Optics
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Optical Transmitter
Definition: a device that converts electrical signal into optical signal
Lasers
Fabry-Perot Lasers (FP)
Distributed Feedback Lasers (DFB)
Vertical Cavity Surface Emitting Lasers (VCSEL)
ASE fiber laser
Light Emitting Diodes (LED)
Surface-Emitting LED (SLED)
Edge-emitting LED (EELED)
Transmitter
Fabry-Perot Laser (FB Laser)
Radiation pattern: 60o angle cone-shape
Output power: several mW
Modulation: at high rates
Spectral width: relatively big
Optical Receiver
Definition: convert optical signal into electrical signal
Types:
p-i-n photodetector: photon-electron converter
Avalance photodetector (APD): more sensitive for high speed systems
Photodetector parameters:
Responsivity: the amount of current produced per unit of input optical power
Wavelength bandwidth: the bandwidth the PD is sensitive to.
Damage threshold: the maximum optical power the PD can take before damage
Optical Fiber Sensor
Optical fiber sensor: A sensor that measures a physical quantity based on its modulation on the intensity, spectrum, phase, or polarization of light traveling through an optical fiber.
Advantages of optical fiber sensors
Compact size
Multi-functional
Remote accessible
Multiplexing
Resistant to harsh environment
Immunity to electro-magnetic interference
Optical Fiber Sensor Types
Intrinsic: the effect of the measurand on the light being transmitted take place in the fiber
Extrinsic: the fiber carries the light from the source and to the detector, but the modulation occurs outside the fiber
Index matching fluid
Definition: A liquid with refractive index similar to glass that is used to match the materials at the ends of two fibers to reduce loss and back reflection.
Applications:
Reduce back reflection
increase coupling between two fibers
[attachment=37971]
Optical Transmitter
Definition: a device that converts electrical signal into optical signal
Lasers
Fabry-Perot Lasers (FP)
Distributed Feedback Lasers (DFB)
Vertical Cavity Surface Emitting Lasers (VCSEL)
ASE fiber laser
Light Emitting Diodes (LED)
Surface-Emitting LED (SLED)
Edge-emitting LED (EELED)
Transmitter
Fabry-Perot Laser (FB Laser)
Radiation pattern: 60o angle cone-shape
Output power: several mW
Modulation: at high rates
Spectral width: relatively big
Optical Receiver
Definition: convert optical signal into electrical signal
Types:
p-i-n photodetector: photon-electron converter
Avalance photodetector (APD): more sensitive for high speed systems
Photodetector parameters:
Responsivity: the amount of current produced per unit of input optical power
Wavelength bandwidth: the bandwidth the PD is sensitive to.
Damage threshold: the maximum optical power the PD can take before damage
Optical Fiber Sensor
Optical fiber sensor: A sensor that measures a physical quantity based on its modulation on the intensity, spectrum, phase, or polarization of light traveling through an optical fiber.
Advantages of optical fiber sensors
Compact size
Multi-functional
Remote accessible
Multiplexing
Resistant to harsh environment
Immunity to electro-magnetic interference
Optical Fiber Sensor Types
Intrinsic: the effect of the measurand on the light being transmitted take place in the fiber
Extrinsic: the fiber carries the light from the source and to the detector, but the modulation occurs outside the fiber
Index matching fluid
Definition: A liquid with refractive index similar to glass that is used to match the materials at the ends of two fibers to reduce loss and back reflection.
Applications:
Reduce back reflection
increase coupling between two fibers