# Optical Communications Questions and Answers – Dispersion Management and Soliton Systems

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This set of Optical Communications Problems focuses on “Dispersion Management and Soliton Systems”.

1. Calculate second order dispersion coefficient for path length L2 20km and L1 160km. Dispersion coefficient for L2 is 17.
a) -2.125ps/nm km
b) -3.25ps/nm km
c) -3.69ps/nm km
d) -1.28ps/nm km

Explanation: The second order dispersion coefficient for path length is given by-
β21 = -β22L2/L1. Here, β22 = Dispersion coefficient forL2, L2 and L1 are path lengths.

2. Calculate the path length L2 if L1is 160, dispersion coefficient of L2 is 17, dispersion coefficient of L1 is -2.25 ps/nmkm.
a) 40 km
b) 20 km
c) 30 km
d) 10 km

Explanation: The path length L2 is given by-
L2 = β21L1/-β22. Here, β22 = Dispersion coefficient forL2, β21 = Dispersion coefficient for L1, L2 and L1 are path lengths.

3. Calculate path length L1 if L2 is 20, dispersion coefficient of L2 is 17, dispersion coefficient of L1 is -2.25 ps/nmkm.
a) 180 km
b) 30 km
c) 160 km
d) 44 km

Explanation: The path length L1is given by-
L1 = β21L2/-β22. Here, β22 = Dispersion coefficient forL2, β21 = Dispersion coefficient for L1, L2 and L1 are path lengths.

4. Calculate second order dispersion coefficient for path length L1 20 km and L1 160 km. Dispersion coefficient for L1 is -2.125*10-12s/nmkm.
a) 20
b) 19
c) 18
d) 17

Explanation: The second order dispersion coefficient for path length is given by-
β22=-β21L2/L1. Here, β21 = Dispersion coefficient forL1, L2 and L1 are path lengths.

5. Calculate dispersion slope for second path fiber if L1 is 150, L2 is 10 and s1 is 0.075.
a) 1.125
b) 2.125
c) 3.125
d) 1.9

Explanation: Dispersion slope for second path fiber is s2 = -s1(L1/L2). Here s1 and s2 are dispersion slopes for L1, L2. L2 and L1 are path lengths.

6. Calculate dispersion slope for first path fiber if L1 is 160, L2 is 20 and s2 is 0.6ps/nm km.
a) 0.1
b) 0.432
c) 0.236
d) 0.075

Explanation: Dispersion slope for first path fiber is s1 = -s2(L1/L2). Here s1 and s2 are dispersion slopes for L1, L2. L2 And L1 are path lengths.

7. Calculate L2 if dispersion slope for first path fiber is 0.075 and L1 is 160 km and s2 is -0.6ps/nm km.
a) 20 km
b) 30 km
c) 40 km
d) 50 km

Explanation: L2 is determined by –
L2 = (-s1/s2)*L1. Here s1 and s2 are dispersion slopes for L1, L2. L2 and L1 are path lengths.

8. Calculate L1 if dispersion slope for first path fiber is 0.075 and L2 is 20 km and s2 is -0.6ps/nm km.
a) 170 km
b) 160 km
c) 180 km
d) 175 km

Explanation: L1 is determined by –
L2 = (-s1/s2)* L2. Here s1 and s2 are dispersion slopes for L1, L2. L2 and L1 are path lengths.

9. Calculate separation of soliton pulses over a bit period length if R2 pulse width is 6 ps for bit period of 70 ps.
a) 5.9
b) 5.7
c) 5.8
d) 5.4

Explanation: The separation of soliton pulses over a bit period length is calculated by –
q0 = T0/2ς. Here ς = pulse width and T0 = bit period.

10. Calculate RZ pulse width if bit period is 60ps and separation of soliton pulses is 5.4.
a) 5.5ps
b) 8.1ps
c) 4.3ps
d) 2.3ps

Explanation: RZ pulse width can be calculated by –
ς = T0/q0. Here ς = pulse width and T0 = bit period.

11. Calculate bit period if RZ pulse width is 50ps and separation of soliton pulses is 5.6.
a) 570ps
b) 540ps
c) 430ps
d) 560ps

Explanation: Bit period can be calculated by –
T0 = 2T2q0. Here T2=pulse width and T0=bit period.

12. Calculate value of dimensionless parameter if bit period is 45ps and RZ pulse width is 4 ps.
a) 5.625
b) 5.0
c) 4
d) 6.543

Explanation: Dimensionless parameter is given by –
q0 = T0/2ς. Here ς=pulse width and T0=bit period.

Sanfoundry Global Education & Learning Series – Optical Communications. 