Thermal design of the TW-150 passive optical network access unit. II

The TW-150 unit is a thermally hardened product designed to operate under harsh ambient conditions ranging from -40 to 75/spl deg/C and altitudes of up to 13,000 ft above sea level. The unit is designed so that the case and junction temperatures of any component should not exceed 85 and 90/spl deg/C, respectively. Further, the case temperature of the optical module is to be limited to 76/spl deg/C under all operating conditions. Extensive thermal analysis was conducted so that the box operates reliably under these conditions with an acceptable mean time between failure. We present comparison of CFD results with experiments for selected cases. We then discuss transient modeling and fan failure analysis, the effects of fan speed and altitude on temperature of components, and comparison of honeycomb vent with perforated plate vent. We then discuss miscellaneous effects such as the effects of fan power, leakage through small gaps in the system, and placement of temperature sensors inside the unit.