Optical Wireless Alternative
Optical Wireless technology, such as that offered by Plaintree Systems, is faster to deploy, less subject to intereference, and more secure than the fixed wireless competition.
by Alex Goldman
Associate Editor, ISP-Planet
[October 13, 2000]
Optical Wireless (OW) is an alternative to traditional Radio Frequency (RF) wireless. OW systems can be densely deployed in urban areas without incurring interference problems. They can offer much higher capacities than RF systems, require no licencing, and can be very cost-competitive.
Plaintree Systems, Inc. of Ontario, Canada, has a product line of point-to-point OW systems geared to ISPs. Their commercial clients are demanding high speed Internet access for services such as web hosting and e-commerce.
ISPs are using OW solutions such as Plaintree's to provide high speed Internet access directly to their clients with minimal planning or installation delays.
Freedom is light
David Kahn, Plaintree's Vice President of Product Development, explained the technology to ISP-Planet:
Plaintree's OW systems use Light-Emitting Diodes (LEDs), which are safer and more reliable than lasers. The company's ATM series is still in the lab but this product achieves data rates up to that of Fast Ethernet (100 Mbps). It is currently shipping models that combine a telecom T1 channel with an Ethernet channel.
OW systems work on a line-of-sight, point-to-point basis and have ranges extending up to and beyond 2 km (1.25 miles).
Terminals need not be deployed outdoors—they can be set up in an office by a window. The only requirement is a clear view of the other end of the link.
After the beam leaves the terminal, it spreads out. Systems with a beam spread of half a degree or less can be used but alignment will be upset by building movements caused by winds unless active autotracking is used. Systems with larger beam spreads are more immune to building shake but have lesser range. Plaintree offers both types of systems.
The future's so bright, I gotta wear shades
Optical networks promise transmission without interference, and promise to provide higher security, simply because the transmission involves a beam rather than a radiated signal.
OW systems are basically free of interference; many terminals can be located close together on the same rooftop. This contrasts with the RF radio situation where great care has to be taken with deployment and frequency re-use to minimise interference, and the task is almost impossible in urban areas using the unlicensed RF bands.
OW systems also provide higher security. This is because the beams are so well confined and high in the air. Any interception operation is very exposed and liable to disrupt transmission in a very obvious way, warning system managers.
Blinded by nature
There are two major issues for OW: fog and direct sunlight.
Direct sunlight is only a problem if the link is on an East-West line: It may disable one receiver for a minute or two during dawn and dusk.
Fog, however, can be real problem, and OW systems should not be deployed in areas where thick fog is a frequent occurrence. Rain, snow, and light fog are not major problems, as OW systems are all designed with sufficient margins to cope with these effects.
Other strong points
OW systems use a unregulated part of the spectrum, and so avoid the delays—and costs—of licensing.
The LED-based systems offered by Plaintree are extremely reliable, with an estimated lifetime of 25 years. This greatly reduces the costs of preventive or corrective maintenance.
The LED based systems are also much less of a threat to the eyes, producing power densities on the retina 1,000 times less than those from lasers. They can safely be viewed at close range or through binoculars. It is like the difference between a TV remote controller and a laser pointer.
Actual sales
We spoke to Bill White, Director of Sales and Marketing, who told us that many clients have been large instutitions with specific point-to-point needs, such as a university that needed to cross a government-owned highway that cut through the campus, and could not get permission to dig. The university used an OW connection between two science buildings to complete its network.
With each link (a pair of OW units) costing $9,995 for LED or $13,000 for laser, this is not a residential access solution, but is appropriate for businesses and multiple tenant residential units (MTUs).
In its new product announcement on October 10, 2000, Plaintree touts its WaveBridge Multiplex (MT) series for GSM providers and ISPs. These links enable customers to transmit data at Ethernet speeds while still accessing alternate lines, essentially allowing a user to access phone lines and Ethernet data transmission over the same link.
Expect more in the near future. Said Plaintree CEO and President David Watson, "This is just the first of a number of product releases that Plaintree will be announcing over the next two quarters." |
