Wireless goes "perpetual motion" as BT hatches new company

by Guy Kewney | posted on 17 May 2002

It's magic. Fancy gigabit wireless Ethernet? This can give it to us. They call it "Green Radio" but it's really just wizardry. Feed light into the Microwave Photonics device, and radio waves come out the other side. Feed radio waves into it, and you generate fibre-optic data traffic. It gives us the totally unpowered access point for wireless LAN users.

Guy Kewney

So it's a bi-directional transceiver in a single, solid state passive optical chip. "When I first heard about this, I thought it was magic," acknowledged Maurizio Vecchione, the new CEO of BT's newest "incuband" company, Microwave Photonics - a company being launched onto the world with astonishment this week.

<1/> Maurizio Vecchione

The invention seems impossible. You take a tiny semiconductor device, and feed fibre-optic data into it. Using no more power than the energy it gets from the laser at the other end, it generates wireless - at any frequency from 40 GHz downwards.

And when it receives wireless input, it modulates the incoming laser signal, and sends it back to the other end. In short, it's a wireless access point which requires no external power source - just a fibre-optic link. And maybe, not even that ...

The technology - this is the beauty of it - isn't new. The semiconductor device inside the magic box is perfectly standard Indium Phosphide - something that's been around for years - since 1983, in fact. You'll find InP devices in electro-absorbtion modulators, which are made by many, many semiconductor fab plants already. To adjust it to working as a bidirectional transceiver, requires "only minor tweaks" to the semiconductor process, according to Peter Smyth, chief technical officer. There is almost nothing else in any access point. All the electronics which make it clever, are somewhere else.

To make the access point into a Bluetooth device, you send it ready-modulated optical pulses at the frequency you require. All protocols are handled back at the source of the optical data stream, in a device they call an "optical wireless gateway" (OWG) - which means the same access point can switch from Bluetooth to WiFi, to WiFi5, or even to any other protocol at any other frequency.

Companies like Cisco and Nortel are already negotiating for rights to this technology, because it makes wireless LAN (WLAN) infrastructures vastly cheaper. But it isn't only the price that attracts them. More to the point, is the fact that any InP-driven access points are future-proof. Any upgrades, changes or additions to the protocol are handled by circuit cards which are "hotelled" in the central OWG. It may be no more than a software update, in most cases. As soon as the new software is loaded, your access point is upgraded.

<1/> Peter Smyth

The issue of just how far it can be upgraded is an interesting one. Take the forthcoming WLAN standard, IEEE 802.11a, or WiFi5; it is a 5 GHz protocol, capable of handling 50-odd megabits of data per second. Everybody already has 100 megabit Ethernet wired networks, however, and are moving up to Gigabit Ethernet as we speak; and so wireless users will want something similar.

In theory, if the right licence can be obtained, the Microwave Photonics devices will go way beyond that - right up to 40 gigabits per second. All you need is the rights to broadcast at the appropriate frequency; and there are several licence-free parts of the spectrum to choose from, and there will probably be others.

Of course, it isn't magic; the power has to come from somewhere. The surprise is that there's enough power in a comms laser to do this.

"We use maybe 90% of the incoming power to generate the wireless signal," said Smyth. "The other 10% is used to re-modulate the incoming light signal for the return data."

But of course, you don't have to do that; because you can pick up energy from any source - wireless source, that is. So it really does look as if it will be possible to have very, very cheap wireless networks using almost no wired power at all, in most public areas.

Microwave Photonics, the company, isn't looking at home use at this point; it sees its first opportunity as selling into the enterprise WLAN market. But it is very aware that it has a unique advantage over any other startup" company - BT is its venture capital sponsor, and BT has all the intellectual property rights long-registered, accepted by the international electronics community, and licensing arrangements made. It can move straight into operational mode.

More details on Microwave Photonics' web site; it will be upgraded next week, so it's worth going back for more detail than the single page you'll find there today.