Free space optics (FSO) has had more than its share of hype bubbles, but they have always burst quickly, as cost and complexity of the wireless optical transmission technology, and its need for line-of-sight, came to outweigh its ultra-high speeds. However, the need for very fast backhaul and fronthaul for 5G systems is focusing attention on FSO again, for networks where a wireless alternative to fiber would be desirable. Several start-ups and specialists have kept the flame alive for FSO, including LGS Innovations (formerly part of Alcatel-Lucent), BridgeComm (a five-year-old firm formerly called BridgeSat), Collinear Networks, and Canada’s fSona. Each has its own niche markets, but dreams of taking a more mainstream role in the 5G era, which would drive…