Top 29 Microwave And Optical Link Installation Interview Questions You Must Prepare 02.Oct.2022

  • Provide proper light guidance inside the core.
  • Avoid leakage of light from the fiber. 

A leaky mode or tunneling mode in an optical fiber or other waveguide is a mode having electric field that decays monotonicallv for a finite distance in the trverse direction but becomes oscillatory everywhere beyond that finite distance.

During manufacturing of fiber, certain impurities (dopants) are introduced in the core and cladding. so that the refractive index is slightly higher in core than cladding.

LEDs and L4SER diodes are the commonly used sources in optical communication systems, whether the system trmits digital or analog signal. It is therefore, often necessary to use linear Electrical to Optical converter to allow its use in intensity modulation & high quality analog trmission systems.

An anomaly is the smallest discrepancy that can be observed between the actual and desired characteristics of an item.

MFD ( mode field diameter) determines the fundamental mode by the radial extend of its electromagnetic field including losses at launching and joining, microbend losses, waveguide dispersion and width of radiation pattern.

Optical signal is trmitted through optical fiber it is retrieved in its original electrical form with the help of optical to electrical conversion device such as photo detector.

  • To trmit the information which are in the form of coded signals of the telephone communication, computer data.
  • To trmit the optical images(ex: endoscopy).

Rays following the zigzag path when they travel through fiber and for every reflection it will cross the fiber axis.

  • High trmission rate.
  • Reliability.
  • High availability and capacity.

Isotropic pattern from a surface emitter is called a lambertian pattern. In this pattern source is equally bright when viewed from any direction, but power diminishes as cose.

These are the removable joints which allow easy, fast manual coupling and uncoupling of fiber analogous to electrical plugs and sockets.

Macrobend losses occurs when radius of curvature that all large compared with fiber diameter microbend losses are small scale fluctuation in radius of curvature of fiber axis. 

Polarization refers to the electric field orientation of a light signal, which can vary significantly along the length of a fiber polarization state is fundamental property off an optical signal.

The speckle pattern observed in multimode fiber as fluctuation which have characteristics times longer then the resolution time of the detector is know as modal or speckle noise.

  • Amplifying medium 
  • An optical feedback 
  • Pumping source.

Fiber optics are long lenses. A cylinder or rod of trparent material forming a core surrounded by an external cladding with a slightly different material. Light, when entering the fiber, rebounds on the outer cladding towards the core. This way the light advances through the fiber in bounds or steps. until it exits at the other end. 

Rays following the helical path around the fiber axis when they travel through the fiber and they would not cross the fiber axis at any time.

At angles of incident greater than the critical angle the light is reflected back into the originating dielectric medium, which is known as Total internal reflection.

  • Absorption (fiber material). 
  • Scattering (fiber material + structural imperfection). 
  • Radiative effects. 
  • Pulse broadening. 

A connection between two end nodes whose traffic is switched only in the optical domain at intermediate nodes is referred to as a lightpath.

Attenuation occurring as a result of either a bend in an optical fibre that exceeds the minimum bend radius or an abrupt discontinuity in the core/cladding interface is called bending loss.

In weald guiding fibers is small then HE-EH mode pair occurs which have almost identical propagation constants and electromagnetic patterns such mode are called degenerate modes.

It is minimum angle angle of incident beyond which the total internal reflection occurs for light travelling from a medium of higher to one of lower refractive index is called critical angle.

It is possible to find the minimum received optical power required for a specific bit error rate performance in a digital system. This minimum received power level is known as quantum limit.

  • Photo detector noise.
  • Quantum noise.
  • Dark current noise (bulk dark current, surface dark current). 
  • Amplifier noise. 
  • Thermal noise or Johnson noise.

In optical fiber communication system electrical signal is first converted into optical signal with the help of electrical to optical conversion device as LED.

The maximum angle 4max with which a ray of light can enter through the entrance end of the fiber and still be totally internally reflected.

Attenuation loss (or path propagation loss) is the reduction in power density (attenuation) of an electromagnetic wave as it propagates through space.