Abstract: A photonic switch uses a cost-effective DWDM optimized switch architecture allowing the introduction of DWDM into the metro network. In order to implement this architecture cost-effective ways of implementing the optical carrier frequency/wavelength precision required for a Dense Wavelength Division Multiplexing 100 GHz or 50 GHz on-grid solutions are needed. The photonic switch acts as an intermediary between the WDM density of the access portion of the metropolitan photonic network and the DWDM density of the core photonic network. The metro photonic switch introduces optical carriers that are all generated in the photonic layer adjacent to it and allocates them out to the photonic access nodes for modulation. This has the advantage of providing the optical carriers to be modulated from a centralized highly stable and precise source, thereby meeting the requirements for DWDM carrier precision, whilst generating these carriers in relatively close proximity to the modulators.