We proposed recently a new «Smart Grids Plus» concept for digital energy grids design. These grids, in addition to layers of intelligent energy grids and information communication channels, include a layer of diagnostic monitoring based on a passive fiber optic sensor networks. Sensor networks have a hybrid TWDM structure – information exchange channels and integrated fiber optical sensors – core, based on a new technology for address interrogation and multiplexing – special addressable fiber Bragg gratings, combined for arbitrary topologies - point and quasi-distributed. Some examples of diagnostic monitoring nets for temperature control of complete switchgear contacts (point) and bus bars (quasi-distributed) are considered. Their principles of operation are discussed. The main advantages of these sensor networks are using of addressable fiber Bragg gratings simultaneously as sensors and multiplexing elements, and using of PON structure simultaneously as sensor and communication networks.