Module 1
Tutorial – Problems
Equations – Module 1
For SI
For GI
step index profile when α = ∞
V no. cutoff of Single Mode in GI
parabolic profile when α = 2 (BEST)
triangular profile when α = 1 For single mode fibers, V = 2.405
UTY Problem 1
• graded index fiber with a parabolic refractive
index profile core has a refractive index at the
core axis of 1.5 and a relative index difference
of 1%. Estimate the maximum possible core
diameter which allows single mode operation
at a wavelength of 13micro meter.
UTY Problem 2
• A multimode step index fiber with core
diameter 60μm and relative refractive index of
1% is operating at 0.80μm.Determine
normalized frequency parameter of the fiber
UTY Problem 3 , 4
• An optical fiber with attenuation of
0.25dB/Km is used for 20Km transmission. The
light power launched in to the fiber is 2 mW.
What is the output power?
UTY Problem 5, 6
UTY Problem 7, 8
UTY Problem 9, 10
Module III
Problems
Equations
6.626 x 10-34
1.602 x 10-19. C
Bulk Recombination Lifetime Internal Quantum Efficiency Internal Power Generated
Transmission Factor
LED Index
Power Emitted to medium External Power Efficiency Coupling Efficiency
Power Conversion Efficiency Optical Losses in dB
Equations
6.626 x 10-34
1.602 x 10-19. C
Bulk Recombination Lifetime Internal Quantum Efficiency Internal Power Generated
Transmission Factor
LED Index
Power Emitted to medium External Power Efficiency Coupling Efficiency
Power Conversion Efficiency Optical Losses in dB
UTY Problem 1
• Define LED efficiency. What is the power
coupled in to a step index multimode fiber
whose core refractive index is 1.48 and
cladding refractive index is 1.46 if LED radiates
100μw power
UTY Problem 2
• A 2x2 coupler has an input optical power level
of 200μW.The output powers at the other
three ports are P1=90μW, P2=85μW and
P3=6.3nW.Find coupling ratio and return loss
for this coupler.
UTY Problem 3
• InGaAsP LED operating at 1310nm has
radiative and non- radiative recombination
times of 30 and 100ns respectively.The current
injected is 40mA.Calculate, i)bulk
recombination lifetime ii)internal quantum
efficiency iii)internal power level.
Module 3
• 3 important characteristics of a photodiode:
– Quantum Efficiency
– Responsivity
– Multiplication Factor
• The efficiency of a photodiode in converting photos to
electron – hole pairs is known by the term Quantum
Efficiency
• Relation between optical power given to the
photodiode and the photocurrent generated –
Responsivity
• Relation between Multiplied avalanche photo current
to primary photo current – Multiplication Factor
• Depends on material bandgap, operating wavelength,
and doping thickness of P, I, N regions
Module 4
• The transmission bit rate for soliton propagation when the amplifier
spacing is smaller than the dispersion length
• (i.e. LA << LD)
• The transmission bit rate for soliton propagation when the amplifier
spacing is greater than the dispersion length
• (i.e. LA >> LD)
Module 5
Problems
EDFA Gain (dB) = 10 log10 ((Pout – PASE)/ Pin)
Quantum efficiency Population Inversion Factor
For a typical EDFA, the value of is equal to 2 and the resultant noise figure is F=4 (6dB)
Gain Coefficient
Gain
Mode Number Spontaneous Emission Factor
SOA
A semiconductor optical amplifier operating at a signal wavelength of1.3μm
produces a gain of 20dB with an optical bandwidth of 900GHz.The device has a
spontaneous emission factor of 1.5 and the mode number is equal to 2 with a net
signal gain of 300. Determine
a) The length of the SOA
b)The ASE noise signal power at the output of the amplifier
• An EDFA is pumped at 980nm with a 30 mW
pump power. If the gain at 1550nm is
20dB,what are the maximum input and output
powers?
