Which of the following is NOT recommended to be used in OSP design?

In the context of Outside Plant (OSP) design, pole height is a critical factor that influences the overall effectiveness and efficiency of the telecommunications infrastructure. The recommendation against using 2.2m poles is primarily due to their insufficient height for the typical applications required in OSP setups. Such a low pole height may not provide adequate clearance for hardware installations, such as overhead cables, to avoid interference with the ground, vegetation, or vehicular traffic.

Higher pole options, like those around 6m, 8m, or 10m, offer better clearance and support for various telecommunications features. They also accommodate necessary safety standards by ensuring that lines are elevated enough to reduce risks associated with weather events and normal maintenance activities. Thus, while there are specific contexts where shorter poles might be applicable, generally in OSP design, 2.2m poles fall short of the recommended standards for effective telecommunications infrastructure.