Name of the College : Noorul Islam College of Engineering
University : Anna University
Degree : B.E
Department : Electronics and Instrumentation Engineering
Subject Code/Name : EI 1001 – Fiberoptic & Laser Instruments
Document Type : Question Bank
Website : niceindia.com
Download Model/Sample Question Paper :https://www.pdfquestion.in/uploads/niceindia.com/3014-EI_1001_FIBER_OPTICS_AND_LASER_INSTRUMENTS.pdf
NICE Fiberoptic & Laser Instruments Question Paper
UNIT – I
1.What is incident and reflected light? :
Incident Light :Light approaching a surface is known as incident light. This is the incoming light before it has reached the surface. Reflected Light:After light has struck a surface and bounced off, it is known as reflected light. This is the light that is now departing from the surface.
Related : Noorul Islam College of Engineering IC1402 Computer Networks & Distributed Control System B.E Question Bank : www.pdfquestion.in/3013.html
2. What is angle of incidence and angle of reflection? :
Angle of incidence :
The angle between an incident ray and the normal to a reflecting or refracting surface. The angle at which a ray of light approaches a surface, reflective or not, is called the angle of incidence. It is measured from an imaginary line perpendicular to the plane of the surface in question to the incoming ray of light.
3. Angle of Reflection :
Once the light has reflected from a reflective surface, the angle at which the light departs from the surface is called the angle of reflection. This angle is also measured from a perpendicular to the reflecting surface to the departing ray of light. When light reflects from a surface, the angle of reflection is always equal to the angle of incidence.
4. Define critical angle? :
In geometric optics, at a refractive boundary, the smallest angle of incidence at which total internal reflection occurs. The angle of incidence is measured with respect to the normal at the refractive boundary.The critical angle is given by where c is the critical angle, n 1 is the refractive index of the less dense medium, and n 2 is the refractive index of the denser medium.
Note 3 : The incident ray is in the denser medium.
Note 4 : If the incident ray is precisely at the critical angle, the refracted ray is tangent to the boundary at the point of incidence.
5. What is fiber optics? :
Fiber optics is a medium for carrying information from one point to another in the form of light. Unlike the copper form of transmission, fiber optics is not electrical in nature. A basic fiber optic system consists of a transmitting device, which generates the light signal; an optical fiber cable, which carries the light; and a receiver, which accepts the light signal transmitted. The fiber itself is passive and does not contain any active, generative properties.
6. What is bandwidth and wavelength? :
Bandwidth :
Measure of the information-carrying capacity of an optical fiber
Wavelength :
The distance between two successive points of an electromagnetic waveform, usually measured in nanometers (nm).
7. What is total internal reflection? :
The reflection that occurs when light, in a higher refractive-index medium, strikes an interface, with a medium with a lower refractive index, at an angle of incidence (with respect to the normal) greater than the critical angle. When a light ray traveling in one material hits a different material and reflects back into the original material without any loss of light, total internal reflection occurs.
Since the core and cladding are constructed from different compositions of glass, theoretically, light entering the core is confined to the boundaries of the core because it reflects back whenever it hits the cladding. For total internal reflection to occur, the index of refraction of the core must be higher than that of the cladding.
8. Define waveguide? :
A material medium that confines and guides a propagating electromagnetic wave. In the optical regime, a waveguide used as a long transmission line consists of a solid dielectric filament (optical fiber), usually circular in cross section. In integrated optical circuits an optical waveguide may consist of a thin dielectric film.
9. What are the three basic parts of a optical fiber? :
The CORE, CLADDING, and COATING or BUFFER are the three basic parts of an optical fiber.
10. What are the two basic modes of fibers? :
Fibers are classified by the number of modes that propagate along the optical fiber. Single mode fibers propagate only one mode because the core size approaches the operational wavelength. Multimode fibers can propagate over 100 modes depending on the core size and numerical aperture.
11.What is acceptance angle and acceptance cone? :
The maximum angle ‘a’ with which a ray of light can enter through the entrance end of the fiber and still be totally internally reflected is called acceptance angle of the fiber .The light ray incident on the fiber core must be within the acceptance cone defined by the acceptance angle to be propagated along an optical fiber.
12. What is macro bending? :
If a bend is imposed on an optical fiber, strain is placed on the fiber along the region that is bent. The bending strain will affect the refractive index and the critical angle of the light ray in that specific area. As a result, light traveling in the core can refract out, and loss occurs. A macrobend is a large-scale bend that is visible.
13. What is Microbending? :
This is a small-scale distortion, generally indicative of pressure on the fiber. Microbending may be related to temperature, tensile stress, or crushing force. Like macrobending, microbending will cause a reduction of optical power in the glass. Microbending is very localized, and the bend may not be clearly visible upon inspection. With bare fiber, microbending may be reversible; in the cabling process, it may not.
14.What is a decibel? :
Unit for measuring the relative strength of light signals. Normally expressed in dB, it is equal to one-tenth the common logarithm of the ratio of the two levels. Expressed in dBm when a power level is compared to a milliwatt.
15. What is Zero-Dispersion Wavelength? :
Wavelength at which the chromatic dispersion of an optical fiber is zero; occurs when waveguide dispersion cancels out material dispersion.
UNIT II
1.What are the properties that can be sensed using Fiber Optics? The properties that can be sensed using Fiber Optics are,
** Acceleration
** Chemicals/Gases
** Color
** Displacement
** Flow
** Force
** Humidity
** Liquid Level
** Magnetic/Electric Fields
** Moisture
** Motion
** Position (linear, angular)
** Pressure (fluid, gas, etc.)
** Proximity
** Radiation
** Sound
** Speed
** State-of-Cure
** Strain
** Surface Condition
** Tactile Sensing
** Temperature
** Velocity
** Vibration
** Viscosity
** Weight
2.What is fiber optic gyroscope? One of the more important fiber optic sensors is the fiber optic gyroscope, capable of measuring rotation rate. The principle of operation of the fiber optic gyroscope is based on the Sagnac effect.
3.What is a modulator? Optical carrier waves can be modulated in Amplitude, Phase and Frequency in order to carry information. Modulators modulate the carrier wave by changing the material properties of attenuation ‘a’ and refractive index ‘n.’ In suitable materials a and n can be modulated at high frequencies by time dependent electrical fields (EO), magnetic fields (MO) or acoustic fields (AO). The external modulators produce much less chirp (dispersion) than eg. current-modulated SC-diode lasers.