Page 519 - Fiber Optic Communications Fund
P. 519
500 Fiber Optic Communications
1.5
1
0.5
Phase (rad) 0
*0.5
*1
*1.5
500 1000 1500 2000
Sample #
Figure 11.2 Evolution of laser phase noise. Each curve corresponds to a different realization of the phase noise. The
laser linewidth = 1 MHz for all curves.
1.5
1
lw = 20 KHz
0.5
Phase (rad) 0
*0.5
*1 lw = 1 MHz
*1.5
200 400 600 800 1000 1200 1400 1600 1800 2000
Sample #
Figure 11.3 Laser phase noise evolution for two different linewidths; lw = linewidth. The fluctuations increase with
linewidth and time.
where is the phase noise due to the transmitter laser and is the constant phase shift due to propagation.
TX,l p
The variance of Δ is
l
2 = < 2 > + < 2 >
Δ TX,l LO,l
= 2{Δ TX +Δ LO }lT samp . (11.22)
Here, we have assumed TX,0 = LO,0 = 0 and ignored dispersion and nonlinear effects in the fiber-optic
channel.
