ATTO: Wireless Networking at Fiber Speed

ATTO targets wireless networking at fiber speed: 100 Gb/s/m
²
with latencies smaller than 10 μs. To provide this tremendous wireless capacity, ultrasmall floor-integrated cells are proposed. In this way, short-reach communication can be established, reducing the effect of interference and providing full frequency reuse in the wireless domain. Radio frequency (RF)-over-fiber coherent communication and a dedicated 2-D passive optical network structure support the interconnection and selection of the cells and minimize the required transceiver electronics. To evaluate the feasibility of the proposed architecture, key principles are validated at lower frequency bands. Two main building blocks are addressed in this paper: a fully passive opto-antenna to prove that a passive remote antenna head can be realized owing to the short transmission distances. Furthermore, a low-cost RF-over-fiber system is demonstrated: sigma-delta modulation drives nonlinear optical modulators, such as electroabsorption modulators and vertical-cavity surface-emitting lasers, using a digital transmitter while remaining compatible with the passive opto-antenna. Finally, two important properties of the ATTO floor are evaluated. The exposure of a human body model to RF fields by the antenna floor is evaluated. Measurements ensure a 200-fold margin with respect to the International Commission on Non-Ionizing Radiation Protection basic restriction. To guarantee that multiple devices can communicate with the ATTO floor simultaneously, the interference between cells spaced 300 mm apart was evaluated.