Block1 Part1

Question 1

What is meant by Refractive Index?

Answer 1

The refractive index n is a property of a transparent medium, relating to the speed of light v in the medium to the speed of light c in a vacuum.

v=c/n

Question 2

Why is refractive index relevant to the construction of optical fibres?

Answer 2

If light is directed from one medium to another medium with a lower refractive index, and at a sufficiently shallow angle, the light is reflected back into the first medium.

Can achieve Total Internal Reflection

Question 3

What is the decibel conversion formulae?

Answer 3

G= 10 log_10 * P_1/P_2

where
G is decibels dB
P_1 is power 1
P_2 is power 2

Question 4

Velocity or speed equation

Answer 4

Distance = Velocity * Time

Question 5

tera

Answer 5

10^12
T
Trillion

Question 6

giga

Answer 6

10^9
G
Billion

Question 7

mega

Answer 7

10^6
M
Million

Question 8

kilo

Answer 8

10^3
k
Thousand

Question 9

deci

Answer 9

10^-1
d
Tenth

Question 10

centi

Answer 10

10^-2
c
Hundredth

Question 11

milli

Answer 11

10^-3
m
Thousandth

Question 12

micro

Answer 12

10^-6
μ
Millionth

Question 13

nano

Answer 13

10^-9
n
Billionth

Question 14

pico

Answer 14

10^-12
p
Trillionth

Question 15

Bandwith

Answer 15

The amount of spectrum occupied by a signal called bandwidth.

It is equal to the difference between the highest and lowest frequencies

f_2 - f_1

Question 16

Passband

Answer 16

The range of frequencies that a receiver responds best to

Question 17

The inverse square law

Answer 17

A receiver that is n times as far from the transmitter will receive 1/n^2 of power

Question 18

Wavelength

Answer 18

the distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave

λ = c/f

where λ wavelength
c speed of light 3 x 10^8 m/s
f the frequency

Question 19

What does Shannon’s equation measure?

Answer 19

Channel capacity (bits per second)

Question 20

Shannon’s equation

Answer 20

C = W log_2(1 + S/N)

where,
C is channel capacity (bits per second)
W is the bandwidth in Hz
S/N is the signal to noise ratio

Question 21

Relationship between frequency and wavelength

Answer 21

c=λν

where c = 2.998 x 10^8 m/s the speed of light
λ = lambda the wavelength in metres
ν = nu the frequency in Hz is per second

Question 22

Amplitude Phase Keying (ASK)

Answer 22

A method of digital modulation in which different symbols are represented by segments of a carrier signal with different amplitudes.

The frequency and phase remain the same.

Question 23

Frequency Shift Keying(FSK)

Answer 23

A method of digital modulation in which different symbols are represented by segments of a carrier signal with different frequencies.

The amplitude and phase remain the same

Question 24

Phase Shift Keying (PSK)

Answer 24

A method of digital modulation in which different symbols are represented by segments of a carrier signal with different phases.

The frequency and amplitude remain the same

Question 25

Quadrature Amplitude Modulation (QAM)

Answer 25

QAM, or quadrature amplitude modulation, is where sinusoidal symbols are used that can be viewed as appropriate combinations of in-phase (I) and quadrature (Q) sinusoidal segments.

The resulting symbols thus differ in amplitude and phase, but have a single frequency.

Question 26

Bits per symbol in QAM

Answer 26

n = log_2M

where
n is the bits per symbol
M is the number of symbols

Question 27

Define Baud

Answer 27

The term baud refers to the number of symbols per second, where one baud is one symbol per second

EG if 64-QAM used to transmit data at 48 Mbps
64-QAM is 6 symbols
48/6 is 8 symbols per second
Therefore baud rate is 8 Mbaud

Question 28

Signal-to-noise

Answer 28

Signal power divided by noise power

ie power_s/power_n

Question 29

Power density equation

Answer 29

Power density (W/Hz) = power (W) / bandwidth (Hz)