Page 430 - Fiber Optic Communications Fund

Channel Multiplexing Techniques 411

2.5 mW
Fiber 1
5 mW

2.5 mW 25 ps
3-dB Fiber 2
Combiner
Splitter

Figure 9.22 Generation of OTDM bit stream.

Solution:
The 3-dB splitter splits the optical pulse into two pulses, each with half power.
The delay occurring in fiber 1 is L = 0.5 × 10 −8 × 1 × 10 −3 s = 5ps.
1
To have a separation of 25 ps between pulses, the delay in fiber 2 should be 25 ps + 5ps = 30 ps. Therefore,
the length of fiber 2 is given by
delay 30 × 10 −12
= = 6 mm. (9.92)
0.5 × 10 −8
1

Example 9.6
Develop an OTDM to multiplex four 10-Gb/s data streams into a single 40-Gb/s data stream. Assume the
same parameters as in Example 9.5.

10-Gb/s data stream
1 1 1
40-Gb/s signal
Ch. 1
t L 1 Ch. 1 2 3 4 12 3 4 1 2 3 4
1 1 1
11 0 1 11 1 1 11 1 0
Ch. 2
t L 2
0 1 1 Combiner 100 ps

Ch. 3
t L 3
1 1 0

Ch. 4
t
L 4
Figure 9.23 Multiplexing four 10-Gb/s data streams into a 40-Gb/s bit stream.