An Ethernet communications system for a power monitoring system includes an Ethernet communications device having a processor, a communications interface capable of gathering, under control of the processor, real-time information from one or more slave devices. This depolarization causes a concomitant decrease in the absolute value of the trans-membrane potentials \u0394\u03a8 of the irradiated mitochondrial and plasma membranes. Preferably, an index value based on a volatile indicator is stored. The first and second cavities are located and dimensioned to passively align the optical transmitter, the waveguide and the photodetector when the transmitter is inserted into the first cavity and the photodetector is inserted into the second cavity. , femtosecond pulses, while exposing that location to a substance, e.