Cisco Multiservice Transport Platform Protection Switch Module security appliances. This optical Protection Switch Module (PSM) for the Cisco ONS 15454 Multiservice Transport Platform (MSTP) provides protection against a fiber cut by optically splitting an optical signal over two diverse paths. The PSM allows three types of protection: single-channel or channel protection; amplified or non-amplified Multiplex Section Protection across the composite C- or L-band; and amplified or non-amplified Path Section Protection across the composite C- or L-band