
70 Optical Fiber Communication Systems with MATLAB
®
and Simulink
®
Models
where Δτ is the total pulse broadening. Over the length L, the total dispersion D
T
(λ) = M(λ) +
D
w
(λ) and a source linewidth σ
λ
the criterion becomes
B L D
r T
⋅ ⋅ ≤σ
λ
1.
(3.38)
For a total dispersion factor of 1 ps/(nm · km) and a semiconductor laser of line
width of 2–4nm, the bit rate-length product cannot exceed 100 Gb/s · km. That is, if a
100km transmission distance is used then the bit rate cannot be higher than 1.0 Gb/s
(Figures 3.13 and 3.14).
g(t) 1
–T
0
T
0
t
1
2
= 0.606
e
–
g(t) = e
G(f )
f
f
bw
=
1
2πT
0
1
2πT
0
–
1
2πT
0
=G( f )
T
0
e
2π
–
r
2
2T
2
0
(2πf )
2
2
–
T
2
0
FIGURE 3.12
Fiber resp ...