We present a scalable and novel modular optical metro core node architecture employing photonic WDM integrated switches. Multi-degree switching ROADM nodes are used at the metro-core level, while access network is constituted by low-cost ROADM nodes. Photonic integrated switches have been designed as the building blocks to realize this modular metro node architectures, namely photonic WDM space switches with express and add/drop ports, photonic integrated WSS aggregation/disaggregation functions for merging/dropping the network traffic, and photonic integrated multi-cast switch (MCS), to achieve, together with bandwidth variable transceivers aggregators, multi-Terabits/second operation per link. In particular, photonic WDM space switches and photonic integrated WSS are designed as building blocks to realize this novel modular metro node architectures. Moreover, dynamic re-configurable metro-access nodes based on low-cost photonic integrated mini-ROADMs will be presented. The lossless photonic WDM switches are based on InP technology and employ semiconductor optical amplifiers as on-chip gain element and for fast switching. The photonic WDM circuits allow to switch multiple format data signals in wavelength, space and time for full flexibility, scalability of the interconnected network elements, as well as capacity. Applications will be discussed and experimental results will be reported. Finally advances in compact photonic integrated InP switch design using the InP generic technology will be discussed.