A rack-mounted disk drive enclosure has a plurality of frames, each capable of being individually pulled out of the enclosure from the front. A second semiconductor layer is formed on the first semiconductor layer using a top epitaxial mask covering the top surface of the convex portion. At least some of the monitored andor examined traffic is selected to be blocked based on the degree of trust for the network element. In the inventive switch, an optical signal is spatially split into two polarized beams by a birefringent element, which passes through a polarization rotation device that comprises waveplates, walk-off elements, and an electrically controllable polarization rotator, and recombine into an output fiber, achieving polarization independent operation. As a result, pinch points between the first end and the media are avoided.