434
10 Wavelength Division Multiplexing (WDM)
10.7 (a) The coupling loss is found from the area mismatch between the fiber-core
end-face areas and the coupling-rod cross-sectional area. If a is the fiber-core
radius and R is the coupling-rod radius, then the coupling loss is
L coupling = 10 log
P out
P in
= 10 log
7π a
2
π R
2
= 10 log
7(25)
2
(150) 2 = −7.11 dB
(b) Similarly, for the linear-plate coupler
L coupling = 10 log 7π a
2
/(length × width) = 10 log
7π(25)
2
800(50)
= −4.64 dB
10.8 (a) The diameter of the circular coupling rod must be 1000 μm. The coupling
loss is
L coupling = 10 log
7π a
2
π R
2
= 10 log
7(100)
2
(500) 2 = −5.53 dB
(b) The size of the plate coupler must be 200 μm by 2600 μm.
The coupling loss = 10 log
7π(100)
2
200(2600)
= −3.74 dB
10.9 n = 9 and N = 2
n
= 512
10.10 (a) 1549, 1550, and 1551 nm;
(b) L 1 = 0.4 mm, L 3 = 0.8 mm
10.11 L 1 = 0.75 mm, L 2 = 1.5 mm, L 3 = 3.0 mm
10.12 λ 1 loss: 2.55 dB, λ 2 loss: 3.15 dB, λ 3 loss: 2.30 dB, λ 4 loss: 1.45 dB
10.13 (a) 523 nm; (b) 1547 nm; (c) 4.2 cm
−1 ; (d) 3.9 nm; (e) 94%
10.14 λ 1 loss: 1.2 dB, λ 2 loss: 1.8 dB, λ 3 loss: 1.4 dB, λ 4 loss: 1.0 dB
References
1. C.A. Brackett, Dense wavelength division multiplexing networks: principles and applications.
IEEE J. Sel. Areas Commun. 8, 948–964 (1990)
2. G. Keiser, FTTX Concepts and Applications (Wiley, New York, 2006)
3. N. Antoniades, G. Ellias, I. Roudas, (eds.), WDM Systems and Networks (Springer, 2012)
4. C. Kachris, K. Bergman, I. Tomkos, Optical Interconnects for Future Data Center Networks
(Springer, Berlin, 2013)