Electrical and optical measurements of the nerve impulse for different stimulation voltages.
The optical measurements were done in the pulsed mode using 1000 averages. The figures show the signals in time, the square-root of the power spectral density PSD and the 400 Hz frequency component. The plotted electrical signals are after 10 times amplification. The uncertainties on the data points in (c) are to small to be visible in the figure. The uncertainties on the points in (f) can be estimated from the points without stimulation (0 V) which were measured 9 times and resulted in a 0.25(10) pT·ms signal. By dividing the nerve signal (9.1 pT·ms) by the noise floor obtained without stimulation (0.25 pT·ms) we find the signal to noise ratio, SNR ≈ 37.