An add-drop photonic chip configurable between an add role and a drop role for a transponder aggregator, the chip comprising: a plurality of photonic switch cells (120, 220) for collectively implementing switching functions for either an add transponder aggregator or a drop transponder aggregator; characterized in that the add-drop photonic chip further comprises: a plurality of bidirectional tap-monitors for control of the plurality of photonic switch cells (120, 220), wherein each bidirectional tap-monitor is adapted to detect an optical signal power carried by a through waveguide and includes: a tap waveguide for coupling a fraction of the optical signal power carried by the through waveguide, the tap waveguide including two ports at opposite ends of the tap waveguide; and a single waveguide-type photodetector for detecting the coupled fraction of the optical signal power, the photodetector including two ports that are connected respectively to the two ports of the tap waveguide, wherein when the plurality of photonic switch cells (120, 220) collectively implement switching functions for the add transponder aggregator, the coupled fraction of the optical signal power is fed to the photodetector via one of the two ports of the tap waveguide, and when the plurality of photonic switch cells (120. 220) collectively implement switching functions for the drop transponder aggregator, the coupled fraction of the optical signal power is fed to the photodetector via the other one of the two ports of the tap waveguide. a plurality of photonic switch cells (120, 220) for collectively implementing switching functions for either an add transponder aggregator or a drop transponder aggregator; characterized in that the add-drop photonic chip further comprises: a plurality of bidirectional tap-monitors for control of the plurality of photonic switch cells (120, 220), wherein each bidirectional tap-monitor is adapted to detect an optical signal power carried by a through waveguide and includes: a tap waveguide for coupling a fraction of the optical signal power carried by the through waveguide, the tap waveguide including two ports at opposite ends of the tap waveguide; and a single waveguide-type photodetector for detecting the coupled fraction of the optical signal power, the photodetector including two ports that are connected respectively to the two ports of the tap waveguide, wherein when the plurality of photonic switch cells (120, 220) collectively implement switching functions for the add transponder aggregator, the coupled fraction of the optical signal power is fed to the photodetector via one of the two ports of the tap waveguide, and when the plurality of photonic switch cells (120. 220) collectively implement switching functions for the drop transponder aggregator, the coupled fraction of the optical signal power is fed to the photodetector via the other one of the two ports of the tap waveguide. a tap waveguide for coupling a fraction of the optical signal power carried by the through waveguide, the tap waveguide including two ports at opposite ends of the tap waveguide; and a single waveguide-type photodetector for detecting the coupled fraction of the optical signal power, the photodetector including two ports that are connected respectively to the two ports of the tap waveguide, wherein when the plurality of photonic switch cells (120, 220) collectively implement switching functions for the add transponder aggregator, the coupled fraction of the optical signal power is fed to the photodetector via one of the two ports of the tap waveguide, and when the plurality of photonic switch cells (120. 220) collectively implement switching functions for the drop transponder aggregator, the coupled fraction of the optical signal power is fed to the photodetector via the other one of the two ports of the tap waveguide.