Conducting polymer electrodes based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are used to record extracellular signals from autonomous cardiac contractile cells and glioma cell cultures. The performance of these conducting polymer electrodes is compared with Au electrodes. A small-signal impedance analysis shows that in the presence of an electrolyte, both Au and polymer electrodes establish high capacitive double-layers. However, the polymer/electrolyte interfacial resistance is 3 orders of magnitude lower than the resistance of the metal/electrolyte interface. The polymer low interfacial resistance minimizes the intrinsic thermal noise and increases the system sensitivity. However, when measurements are carried out in current mode a low interfacial resistance partially acts as a short circuit of the interfacial capacitance, this affects the signal shape.
Radio-over-fiber systems employing remote antenna units (RAUs) based on coherent optical heterodyne detection of two phase uncorrelated lasers and envelope detection have been recently demonstrated. By using two uncorrelated lasers, this system concept allows simple implementation that can additionally be improved, if thermally uncooled lasers are used. Although such asynchronous receiver design is mildly affected by the laser phase noise, it suffers from the wavelength drift that occurs between the uncooled laser sources. Also, there are performance penalties due to high laser line-width when complex modulation formats are used for transmission. In this work, we analyze the performance of heterodyne based optical receivers, using OOK and multilevel modulation.