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Optical ILA Cooling System Description

The cooling system in an optical ILA consists of three 12.4 W fan modules installed in the field-replaceable unit (FRU) panel and two counter-rotating fans housed in each of the power supplies.

The cooling system brings air into the vents in the front panel and exhausts warmed air through the fans. This type of airflow is known as airflow out or front-to-back airflow. When installed, the chassis must be positioned so that the FRUs are next to the hot air exhaust.


Under normal operating conditions, the fan modules operate at a moderate speed. Temperature sensors in the chassis monitor the temperature within the chassis. The system raises an alarm if a fan module fails or if the ambient temperature inside the chassis rises above the acceptable range.

Fan Modules

The fan modules in an optical ILA are hot-removable and hot-insertable FRUs. These fan modules can be hot-swapped—you do not need to power off the optical ILA or disrupt the optical ILA function to replace a fan module. The fan module slots are numbered 0 through 2 from left to right when viewing chassis from the FRU panel side (see Figure 1). Figure 2 shows the fan module for the optical ILA. The numbers are located on the top-side of the chassis.

Figure 1: Fan NumberingFan Numbering
Figure 2: Fan ModuleFan Module

All three fan modules must be installed for optimal operation of the optical ILA. The optical ILA continues to operate for a period of time 30 seconds during the replacement of the fan module without thermal shutdown.