Wireless connections of sensor network using RF and free space optical links

Abstract

In this paper, we compare the power consumption of a "line-of-sight" free space optical (FSO) link and a radio frequency (RF) data link. We investigate a 2.5 Gbps line-of-sight FSO interconnection, which consists of a vertical cavity surface emitting laser (VCSEL) driver (MAX3795), a VCSEL laser diode (LD), a PIN photodiode (PD), a transimpedance amplifier (MAX3864), and a limiting amplifier (MAX3746). It is shown that the total power consumption is about 370.6 mW in simple NRZ on-off keying (OOK) modulation format. Different lens configurations are discussed in terms of the integration/setup efforts and the beam controlling effects. A 250 Kbps commercial radio frequency (RF) link comprised in Tmote sky module (Moteiv Corporation) is explored to compare with the FSO link. The average power supplied to the radio transceiver is about 50.76 mw. The estimated energy consumption for the aforementioned RF link is 2.03×10^-4 mJ/bit, while the end-to-end FSO consumes 1.48×10^-7 mJ/bit. This paper provides design outlines from the aspect of the power consumption of FSO and RF wireless communication technologies for distributed sensor network applications.