In general, signal processing is achieved with the help of electronic circuits but electronic bandwidth is limited by the transit frequency of available transistors. Therefore, the electronic circuits are fundamentally limiting our future communication systems. As a consequence, the extreme bandwidth and transmission capacity of optical signals can only be exploited with massively parallel usage of electronic circuits. The basic idea of this proposal is a photonic preprocessing circuit followed by a special time interleaving electronic demultiplexing circuit. In the receiver the broad optical bandwidth of beyond one THz is subdivided into many frequency bands by appropriate filters. An integrated arrayed waveguide grating filter (AWG) can fulfill this task. The approach in this proposal is the additional use of optical phase shifters in intermediate coupling structures of two multimode interference couplers (MMIs) to select a specific wavelength channel electronically with low power and fast switching speed. The resulting device can also be used as an optical switch fabric. Using the proposed concept with MMIs with tuneable phase shifters and scaling them up to an M x M cross bar switch allows a high speed electronically controlled spatial optical switch with lower excess losses compared to a cascaded 2x2-switch network. At the transition from photonics to digital electronics, the bandwidth is limited by the chain of photodetector, transimpedance amplifier and the analog-to-digital converter (ADC). To benefit from the larger bandwidth of photodetectors and transimpedance amplifiers, a special current demultiplexing circuit enables the use of several ADCs in parallel. We propose to realize this special circuit as electronic current-track-and-hold circuit with sampling rates of more than 100 GS/s. In combination with wavelength division multiplexing this solution enables bandwidths of several THz.