Dual excitation band fiber photometry measurements use a Fluorescence Mini Cube with 4 ports: one port for the functional fluorescence excitation light, one for the isosbestic excitation, one for the fluorescence detection, and one for the sample. The cube has dichroic mirrors to combine isosbestic and fluorescence excitations and separate the fluorescence emission and narrow bandpass filters limiting the excitation fluorescence spectrum. E stands for fluorescence excitation, IE for isosbestic excitation, F for fluorescence, and S for the sample port on the cube's schematic. The separation of functional and isosbestic fluorescence signals of GCaMP is possible with modulated light sources. Compared to Fluorescence Mini Cubes with only FC connectors on all ports, the ones with integrated photodetectors provide a 100% better signal-to-noise ratio (30% signal increase and a 40% noise reduction). Moreover, in the latest generation of Mini Cubes, LEDs and LED drivers are integrated as well to reduce the number of connections and the system’s overall footprint. In his generation, it is also possible to replace the excitation filter and decrease the excitation power by adding attenuating filters (for low power photometry).
