Design architecture of optical switching device for PON This paper presents the design architecture of a new optical switching device named Protection Switching Device (PSD) for providing protection and restoration against fiber failures/faults in the distribution region of passive optical network (PON). The developed PSD prototypes are employed at the customer end, just before the optical network units (ONUs) to ensure the data flow continuously due to breakdown occur in the network and instantly repair operation. The network is protected from fiber/equipment failures by using optical switches to bridge the optical signals and dual feed them on diversely routed working line and protection line or neighbor line. When the failure is detected, the protection mechanism will be activated and divert the optical signal direction to the protection line or neighbor line according to the types of failure condition and location of failures in PON.