Fiber Optics (Chapter 11: Past Board Excel)

ECE Board Exam April 2001
Which of the following refers to the relative refractive index difference of single mode fibers?
0.1 - 0.3 %

ECE Board Exam November 2000
A parameter of light beam that do not change the quality when it enters one medium from another.
Frequency

ECE Board Exam April 2000
Which of the following limits the top speed of transmitting information in fiber optic communication?
Detector speed

ECE Board Exam November 1999
Type of multi-channel signal transmission in the optic fiber communication that uses twisted pair coupler to transmit two signals of different wavelengths.
Frequency-division multiplexing

ECE Board Exam April 1999
Best applies to an optical fiber core.
A higher refractive index than the cladding

ECE Board Exam November 1998
How many times bigger does the bandwidth of a fiber optic multimode have over cable?
100 times bigger

ECE Board Exam April 1998
What law does a light travelling in an optical fiber follow?
Snell's

ECE Board Exam November 1997
Band of light waves, that are too short to be seen by human eye.
Ultraviolet

ECE Board Exam April 1997
Insertion loss of connector-type splices for a single-mode fiber cable.
0.38dB

ECE Board Exam November 1996
An object father from a converging lens than its focal point always has an ________ image.
inverted

ECE Board Exam March 1996
The dielectric material of an optical fiber surrounding the core.
Cladding

ECE Board Exam April 2001
An optical time domain reflectometer used in fiber optic communication is not intended to determine one of the following:
Kind of multiplexing

--------------------- An optical time domain reflectometer used in fiber optic communication-------
Refractive index
Loss per kilometer
Length of fiber

ECE Board Exam November 2000
In wire communications system using fiber optic, the packing fraction is related to one of the following statements when referred to fiber optic bundle.
Ratio of the total cross-sectional area to the total cross-sectional area of the fiber bundle

ECE Board Exam April 2000
Why are fiber optic cables considered less expensive compared to coaxial cables in communication system?
Use of less repeaters

ECE Board Exam November 1999
An optic fiber regenerator which is used in communication is consisting of a ________ to clean up and amplify digital data moving in one direction and a similar system for the opposite direction.
transmitter and receiver

ECE Board Exam April 1999
How do you account the effect of light intensity on the refractive index of a fiber optic?
Increases

ECE Board Exam November 1998
One of the following referred to as a major component of an optical time domain reflectometer.
Pulse generator laser

ECE Board Exam April 1998
__________ generates light beam at a specific visible frequency.
Laser

ECE Board Exam November 1997
The most common device used as a light detector in fiber optic communication system.
APDs

ECE Board Exam April 1997
A non-coherent light source for optical communications system.
LED

ECE Board Exam November 1996
The loss in signal power as light travels down a fiber is
attenuation

ECE Board Exam March 1996
It is made from semiconductor material such as aluminum-gallium-arsenide or gallium-arsenide-phosphide.
Light emitting diode

ECE Board Exam April 2001
How much bigger does the bandwidth of a single mode fiber optic have over the multimode fiber?
20 times bigger

ECE Board Exam November 2000
Which of the following refers to the bandwidth of optical fiber?
1 MHz - 500 MHz

ECE Board Exam April 2000
Refers to a characteristic of a multimode fiber optic.
Cladding thickness is greater than the radius of the core and the diameter of the core must be much greater than the wavelength of the light to be carried.

ECE Board Exam November 1999
What do you call the loss in signal power as the light travels the fiber optic?
Attenuation


ECE Board Exam April 1999
One of the characteristics of a fiber optic used in order to carry light in several modes of propagation or to become a multimode fiber.
Diameter of the core must be very muuch greater than the wavelength of the light to be carried.

ECE Board Exam November 1998
What kind of effect is referred to a varying light producing a varying voltage  output of a detector? 
Photovoltaic effect

ECE Board Exam April 1998
Quantity that do not change when a beam of lifgt enters one medium to another
Frequency

ECE Board Exam April 1997
Type of fiber that has the highest modal dispersion.
Step-index multimode

ECE Board Exam November 1997
Calculate the energy of the photon of infrared light intensity at 1.55 um.



ECE Board Exam November 1996
The different angles of entry of light into an optical fiber when the diameter of the core is many times the wavelength of the light transmitted is known as __________.
mode

ECE Board Exam March 1996
An absorption loss caused by valence electrons in the siica material from which fibers are manufactured.
Ultraviolet absorption


ECE Board Exam April 2001
Which of the following is not a major component of an optical time domain reflectometer used in fiber optic communication?
vertical and horizontal plates

-------------------- major component of an optical time domain reflectometer used in fiber optic communication---------------------
Laser
Beam splitter
Pulse generator

ECE Board Exam November 2000
Which of the following is a part of an optical time domain reflectometer?
Beam splitter

ECE Board Exam April 2000
This refers to a certain material which is most sensitive to light.
Photoresist

ECE Board Exam November 1999
Referred to as a light source of fiber optic which supplies level of 5
to 7 milliwats and having a narrow spectrum of emission.
Injection laser diode

ECE Board Exam April 1999
Most likely, how many times would a fiber optic break in a span of thirty years?
2 - 3 times

ECE Board Exam November 1998
An advantage of optic fiber rejecting an induced noise signal from magnetic field or solar storm flux
Immunity to noise

ECE Board Exam April 1998
Which of the following colors of light rays has the shortest wavelength?
Violet

ECE Board Exam April 1997
Fiber optic cable operates near ________ frequencies.
800 THz

ECE Board Exam November 1997
If a fiber optic system has a rise time of 38.55 ns, the source rise time is 12 ns and the detector rise time is 12 ns, what is the cable rise time?


ECE. Board Exam November 1996
Proposed the used of a clad glass fiber as a dielectric waveguide
Bockham and Kao

ECE Board Exam November 2000
ln electronic communications where fiber optic material is used, a reflected
wave is a possibility. what happen to the polarization of this reflected wave
when compared to its original form?
Shifts to 180 degrees

ECE Board Exam April 2000
The effect of multimode propagation caused the rays leaving the fiber to
interfere constructively and destructively as they leave the end of the fiber
this effect is called _________.
modal delay spreading

ECE Board Exam November 1999
What is the wavelength for deep violet light?
500 nmeter

ECE Board Exam April 1999
A device in the fiber optic that is used to attenuate the reflected signal from the polished end of the fiber which has a possibility of developing into a noise.
Isolator

ECE Board Exam November 1998
One of the advantages of the fiber optic which is referred to the volume of capacity of signals it can carry
Bandwidth

ECE Board Exam April 1998
Circuit used to amplify the optical signal in fiber optics communications links.
Optical repeater

ECE Board Exam November 1997
A device that reduces the intensity of light in fiber optics communication systems
Optical attenuator  

ECE Board Exam April 1997
Lifetime of ILDs
50.000 h

ECE Board Exam November 1996
What is the stage of the sand becoming a silicon?
Molten

ECE Board Exam November 2000
One of the major limitations of a plastic fiberoptic used in communication
Due to its high losses

ECE Board Exam April 2000
One of following is considered the largest source of signal power loss in the
use of fiber optic as communications medium such as due to misalignment.
ConnectionECE Board Exam NOvember 1999
One of the following is related to the application of solid material as a medium where light travels.
medium where Ilght travels. apphcatlon of 5DHd mater-ja}; as 3
Fiber optics

ECE Board Exam April 1999
Which of the following is not considered as one of the causes for the loss of signal power as light travels through a fiber optic?
Inter-modulation
----------------causes for the loss of signal power as light travels through a fiber optic-----------------
Scattering
Fiber bending
Absorption

ECE Board Exam November 1997
The core of the optical fiber has _______
a higher index of refraction than the cladding

ECE Board Exam November 1997
Loss due to the diffraction of light when it strikes on the irregularities formed
during the manufacturing process of the fiber optics.
Rayleigh scattering loss


ECE Board Exam November 1996
If a fiber optic system has a rise time of 16 ns, the source rise time is 1.5 ns and the detector rise time is 2 ns, what is the cable rise time?


ECE Board Exam November 2000
A phenomenon which causes the speed of light rays propagation in the fiber
material changes, as it passes through different medium in the fiber
Refraction

ECE Board Exam April 2000
At what intenial does a fiber optic needs a repeater in communications
system?
30 to 300 miles

ECE Board Eanm November 1999
Referfeq to as a limit in reducing further the loss of signal passing through a
fiber optic caused by scattering.
Rayleigh effect


ECE Board Exam April 1999
These are band of light wavelengths, that are too short to be seen by the human eye.
Ultraviolet

ECE Board Exam November 1998
A quarter wavelength device made of crystalline calcite that changes polarization in the optic fiber communication
Retarder

ECE Board Exam April 1999
At what power levels does fiber optic have when used in electronic communications?
Range of micro to milliwatts

ECE Board Exam November 1998
One of the following is among the types of fiber optics used in electronics communication.
Semi-graded multimode


ECE Board Exam November 1998
How do you reduce the loss that is produced when light strikes a flat polished end of a fiber optic?
By application of antireflection coating
 
ECE Board Exam November 1998
What is the device use in used in fiber optic communication which consist of a receiver transmitter use tc clean up and amplify digital data moving in one direction and another in opposite direction? 
Optic regenerator

ECE Board Exam November 2000
An advantage of fiber optic over co-axial cable as a result of coupling signals
from one to the other due to changing magnetic field in one or both.
Crosstalk

ECE Board Exam April 2001
What is the index of refraction of a certain substance if light travels through
the substance at 100 meters at a time is to 140 meters to air'?

OPTICAL FIBER TRANSMISSION MEDIA (C13 Tomasi)

CHAPTER 13

OPTICAL FIBER TRANSMISSION MEDIA

1)Uses light as a carrier of information.

Optical communications system

2)Electronic communications system is directly proportional to bandwidth.

Information-carrying capacity

3)Bandwidth of an analog communications system as a percentage of its carrier frequency.

bandwidth utilization ratio

4)Device constructed from mirrors and selenium detectors that transmitted sound waves over a beam of light.

Photophone

5)Experimented with an apparatus called photophone.

Alexander Graham Bell

6)Used extensively in medical field.

Flexible fiberscope

7)Invented in 1960.

Laser (light amplification by stimulated emission of radiation)

8)Advantages of Optical Fiber cables.

1. wider bandwidth and greater information capacity

2.immunity to crosstalk

3. immunity to statistic interference

4. environmental immunity

5. safety and convenience

6. lower transmission loss

7. security

8. durability and reliability

9. economics

9)Disadvantages of Optical Fiber cables.

1. interfacing cost

2. strength

3. remote electrical power

4. optical fiber cables are

more susceptible to losses introduced by bending the cable

5. specialized tools, equipment, and training

10)Reduces the possibility of the occurrence of a detrimental phenomenon.

Stress corrosion

12)Protective coating.

Buffer jacket

14)Increases the tensile strength of the over all cable assembly.

Strength member

15)Process of decaying from one energy level to another energy level.

Spontaneous decay or spontaneous emission

16)Science of measuring only light waves that are visible to human eye.

Photometry

17)Measures the rate at which electromagnetic waves transfer light energy.

Optical power

18)Spectral separation of white light.

Prismatic refraction

19)Simply the ratio of velocity of propagation of a light ray in free space to the velocity of propagation of a light ray in a given material.

Refractive index

20)Angle at which the propagating ray strikes the interface with respect to the normal.

Angle of incidence

21)Angle formed between the propagating ray and the normal after the ray has entered the second medium.

Angle of refraction

22)Closely related to acceptance angle and is the figure of merit commonly used to measure the magnitude of the acceptance angle.

Numerical aperture

23)Simply means path.

Mode

24)More than one path.

Multimode

26)Probably the most important characteristic of the cable.

Power loss

27)Three factors that contribute to the absorption losses in optical fibers:

1. ultra violet absorption

2. infrared absorption

3. ion resonance absorption

28)Caused mainly by small bends and kinks in the fiber.

Radiation losses

29)Caused by excessive pressure and tension and generally occur when fibers are bent during handling or installation.

Contants-radius bends

30)Caused by the difference in the propagation times of light rays that take different path down a fiber.

Modal dispersion

32)A p-n junction made from two different mixtures of the same types of atom.

Mojunction structure

33)Generally constructed of silicon-doped gallium-arsenide.

Epitaxially grown

34)Homojunction LED’s output approximately 500 μ at a wavelength of 900 nm.

Planar diffused

35) Advantages of heterojunction devices over homojunction devices;

1. increase in current density generates a more brilliant light spot.

2. smaller emitting area makes it easier to couple its emitted light into a fiber.

3. small effective area has a smaller capacitance, which allows the planar heterojunction LED to be used at a higher speed.

36)Depletion-layer photo diode and is probably the most common device used as a light detector in fiber optic communications system.

PIN diode

37)Characteristic of a light detector.

1. responsivity

2. dark currents

3. transit time

4. spectral response

5. light sensitivity

Fiber-Optic Systems (Blake C25)

        Chapter 25: Fiber-Optic Systems

        TRUE/FALSE

  1.   Most new telephone trunk cables are fiber-optic.

ANS:   T

  2.   Cable TV systems use fiber-optic cable.

ANS:   T

  3.   Many data network cables are fiber-optic.

ANS:   T

  4.   Fiber-optic cable is not practical for telephone trunk cables.

ANS:   F

  5.   CATV uses analog modulation on fiber-optic cables.

ANS:   T

  6.   Usually, splicing losses can be disregarded in loss-budget calculations.

ANS:   F

  7.   The rise time of a transmitter limits its bandwidth.

ANS:   T

  8.   RZ encoding allows twice as much pulse spreading as NRZ.

ANS:   F

  9.   The product of bandwidth times distance describes dispersion in a multimode fiber-optic cable.

ANS:   T

10.   Regenerative repeaters for fiber-optic cables typically convert the light signal to an electrical signal, and then back to light.

ANS:   T

11.   Optical amplifiers are not suitable for digital signals.

ANS:   F

12.   Dispersion effects accumulate when optical amplifiers are used.

ANS:   T

13.   Most fiber-optic systems use TDM.

ANS:   T

14.   Fiber-optic cables shorter than 100 km typically do not require repeaters.

ANS:   T

15.   SONET operates at a base speed of 25 Mbps.

ANS:   F

16.   SONET solves many of the timing problems in synchronizing digital signals.

ANS:   T

17.   SONET is typically used on LANs.

ANS:   F

18.   FDDI can be used on a LAN.

ANS:   T

19.   Soliton pulses can travel down a fiber-optic cable with no dispersion.

ANS:   T

20.   TDR cannot be used on fiber-optic cables.

ANS:   F

        MULTIPLE CHOICE

  1.   FDDI stands for:

a.	Fiber Digital Data Interface	c.	Fiber Distribution Delay Interface
b.	Fiber Distributed Data Interface	d.	Frequency-Division Data Interface

ANS:   B

  2.   FITL stands for:

a.	Fiber In The Loop	c.	Frequency Input to The Loop
b.	Fiber Input Timing Loss	d.	Fiber Input Timing Loop

ANS:   A

  3.   FTTC stands for:

a.	Fiber Transmission Timing Constraint
b.	Fiber Transmission Technology Committee
c.	Fiber Telephone Transmission Cable
d.	Fiber To The Curb

ANS:   D

  4.   SONET stands for:

a.	Simple Optical Network	c.	Synchronous Optical Network
b.	Standard Optical Network	d.	none of the above

ANS:   C

  5.   DWDM stands for:

a.	Digital Wavelength-Division Modulation
b.	Dense Wavelength-Division Modulation
c.	Double Wavelength-Division Modulation
d.	Dense Wavelength-Division Multiplexing

ANS:   D

  6.   A Soliton is a:

a.	defect in the glass	c.	type of pulse
b.	type of particle	d.	type of optical network

ANS:   C

  7.   Adding bits to synchronize one digital signal to another is called:

a.	bit stuffing	c.	SDH
b.	bit-synch	d.	WDM

ANS:   A

  8.   Power above the minimum required by an optical receiver is called:

a.	gain margin	c.	excess gain
b.	system margin	d.	overdrive

ANS:   B

  9.   Typically, repeaters are not required for fiber-optic cable lengths up to:

a.	1000 miles	c.	100 km
b.	100 miles	d.	10 km

ANS:   C

10.   In SONET, OC-1 stands for:

a.	Optical Carrier level one	c.	Optical Channel one
b.	Optical Coupler unidirectional	d.	Optical Cable type 1

ANS:   A

11.   In SONET, STS stands for:

a.	Synchronous Transport Signal	c.	Synchronous Transmission Signal
b.	Synchronous Transport System	d.	Synchronous Transmission System

ANS:   A

12.   A commonly used fiber-based system for LANs is:

a.	FDDI	c.	gigabit Ethernet
b.	high-speed Ethernet	d.	all of the above

ANS:   D

13.   The use of solitons on fiber-optic cables is:

a.	common	c.	obsolete
b.	experimental	d.	not possible

ANS:   B

14.   OTDR stands for:

a.	Optical Time-Delay Response	c.	Optical Time-Domain Reflectometer
b.	Optical Timing Delay Requirement	d.	Optical Time-Division Relay

ANS:   C

15.   Using fiber-optic cable in a telephone system except for the connection to the subscriber's phone is called:

a.	FDDI	c.	FITL
b.	FTTC	d.	SONET

ANS:   B

        COMPLETION

  1.   FTTC stands for Fiber To The ____________________.

ANS:   Curb                        

  2.   FITL stands for Fiber In The ____________________.

ANS:   Loop                        

  3.   SDH stands for Synchronous Data ____________________.

ANS:   Hierarchy                 

  4.   WDM stands for ____________________-division multiplexing.

ANS:   Wavelength              

  5.   SONET stands for ____________________ Optical Network.

ANS:   Synchronous            

  6.   FDDI stands for Fiber ____________________ Data Interface.

ANS:   Distributed               

  7.   Optical amplifiers use ____________________-doped glass.

ANS:   erbium                     

  8.   Optical amplifiers use a ____________________ laser.

ANS:   pump                       

  9.   Dense ____________________ allows many different wavelengths of light to share a cable.

ANS:   WDM                       

10.   The OC-1 line rate is ____________________ Mbps.

ANS:   51.84                       

11.   SONET does not use bit ____________________ to synchronize two digital signals.

ANS:   stuffing                    

12.   SONET uses a ____________________ to denote the starting position of an information frame.

ANS:   pointer                     

13.   FDDI systems use two ____________________ rings to carry signals.

ANS:   token                       

14.   The two rings of an FDDI system carry data in ____________________ directions.

ANS:   opposite                   

15.   Each ____________________ in an FDDI system acts as a regenerative repeater.

ANS:   node                        

16.   FDDI uses ____________________ mode cables.

ANS:   multi                        

17.   The data rate of an FDDI system is ____________________ bps.

ANS:   100 M                      

18.   SONET frames have considerably more ____________________ than do DS frames for information about signal routing and setup.

ANS:   overhead                  

19.   The number of bytes in a SONET frame is ____________________.

ANS:   810                          

20.   The number of bytes in the payload of a SONET frame is ____________________.

ANS:   774                          

21.   The number of rows in a SONET frame is ____________________.

ANS:   9                              

22.   The total number of overhead bytes in a SONET frame row is ____________________.

ANS:   4                              

23.   The number of path overhead bytes in a SONET frame row is ____________________.

ANS:   1                              

24.   SONET frame rows contain path overhead and ____________________ overhead.

ANS:   transport                  

25.   In SONET, SPE stands for synchronous payload ____________________.

ANS:   envelope                  

        SHORT ANSWER

  1.   What is the bandwidth of a first-order LPF with a rise time of 350 nanoseconds?

ANS:  

1 MHz

  2.   Calculate the total rise time for a fiber-optic system if the transmitter, receiver, and cable each have a rise time of 50 nanoseconds.

ANS:  

86.6 nanoseconds