Enhancing Throughput of Optical Wireless Communication by Multi-Branch Dual-stage Cascode Receiver

In an optical wireless communication (OWC) system, the choice of the photo-diode (PD) receiver faces a trade-off between detecting area and bandwidth. If the PD size is increased to receive a strong signal, the capacitance also increases, hence the receiver suffers not only from bandwidth limitations but also from noise amplification. This paper studies adaptive bit and power loading to cope with gain and noise issues. The paper also improves the design of a TransImpedance Amplifier to improve throughput. We propose to use one cascode switch per receiver segment, and we also propose a second cascode amplifier stage. Through circuit simulations, we show that this extends the receiver bandwidth and reduces the noise. To analyze the communication performance of such a system, we analytically model the electro-opto-electro conversion of the transmit signal power. The throughput achieved by various receiver alternatives is estimated for DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM). Our new segmentation approach significantly improves throughput compared to known receiver designs.