resistance Card n Input air VVVWVV temperature FIGURE 6.49 Example of simplified thermal equivalent circuit for a DWDM rack. From each heat resistance determine the corresponding, needed air flow from graphs similar to Figure 6.48 or from specific software. Design the air ducts, SO to assure in every point of the system, at least the required flow, often the higher value of the air flow is the only considered and a worst case design is carried out trying to assure the same flow to all the system parts. At the end of the design, the cooling system should be always analyzed with software solving numerically the fluid thermodynamic equations to verify with a less approxi- mated model the expected performance. References 1. Agrawal, G.P., Fiber Optic Communication Systems, Wiley, New York, s.l., 2002, ISBN-13: 978-0471215714. 2. Ramaswami, R., Sivarajan, K.N., Sasaki, G.H., Optical Networks: A Practical Perspective, 3rd edn., Morgan Kaufmann, San Francisco, CA, s.l., 2010, ISBN: 9780123740922. 3. Senior, J., Optical Fiber Communications: Principles and Practice, 3rd edn., Prentice Hall, Essex, U.K., s.l., 2008, ISBN-13: 978-0130326812. 4. Smith, D.R., Digital Transmission Systems, Kluwer Academic Publishers, Norwell, MA, s.l., 2004, ISBN: 1402075851. 5. Recommendations, ITU-T. M.21xx Series. 6. Recommendations, ITU-T. G.821, G.826, G.828, G.829. Transmission Systems Architectures and Performances 7. Cotter, D., Observation of stimulated Brillouin scattering in low loss silica fiber at 1.3 um, Electronics Letters, 18, 495-496 (1982). 8. Iannone, E., Matera, F., Mecozzi, A., Settembre M., Nonlinear Optical Communication Networks, Wiley, New York, s.l., 1998, ISBN-13: 978-0471152705. 9. Boyd, R.W., Nonlinear Optics, Academic Press, San Diego, CA, 2008, ISBN-13: 978-0123694706. 10. Chaplyvy, A.R., Limitations on lightwave communications imposed by optical fiber nonlineari- ties, Journal of Lightwave Technology, 8, 1548-1557 (1990). 11. Loudon, R., The Quantum Theory of Light, 3rd edn., Oxford Science Publications, Oxford