Free For All

After more than 30 years of development and deployment, free space optics (FSO) seems to be finally finding its niche.

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By  Richard Agnew Published  November 2, 2003

|~||~||~|After more than 30 years of development and deployment, free space optics (FSO) seems to be finally finding its niche.

Originally used by the US military and NASA to beam data across the air in remote locations - space, for example - the technology then struggled to ground itself in commercial reality. Mother nature, scepticism about its reliability and, more recently, the industry slowdown, have all combined to hold FSO's adoption in the telecoms industry back.

Now, however, carriers and service providers are taking a second look at the technology as a viable solution for backing-up terrestrial optical infrastructure and backhauling traffic from access networks. FSO is also increasingly intriguing operators as a means to build short-distance network 'bridges' across roads and areas where fibre would be too expensive or the alternatives can't reach.

Although FSO systems are old hat in the enterprise market, for tasks such as local area network (LAN) to LAN connectivity and storage area networks, they have yet to fill their potential role within telecoms carriers' infrastructure.

In the Middle East and Africa, however, interest in the technology is increasing. Various FSO systems are being promoted as a means to extend metro networks, and to provide Gigabit Ethernet access.

Mobile operators have also taken a look at the technology as an alternative way to backhaul voice and data traffic from cell sites where microwave and other technologies are less feasible.

For example, PAV FSO, the UK-based equipment vendor, has provided its FSO systems as an urban solution to Egyptian GSM operator, Mobinil. "We have over 500 links installed in [Mobinil's] network," says Chris Emerson, managing director, PAV FSO. "MobiNil has predominantly installed them in Cairo to provide E1 connectivity on the edge of the network," he adds.

While Mobinil first adopted the solution around five years ago, Emerson says that the last year has seen similar deals involving GSM backhauling with Djezzy, Orascom Telecom's subsidiary in Algeria, and Kenyan telecoms operators, Safaricom and Kencell.

The two operators in Kuwait, MTC-Vodafone and Wataniya Telecom, have also adopted the technology to varying degrees.
Additionally, the expansion of broadband into areas with a current shortage of fibre or copper-based infrastructure is also fostering demand for FSO in countries such as Saudi Arabia. "We see a lot of opportunity in the internet service provider (ISP) space, where governments are rolling out services into communities," says Mike Penner, vice president of corporate development at US-based vendor, fSONA Communications.

"A lot of countries worldwide have wireline cultures, where they have copper lines everywhere. However, FSO give you the ability to create a high-speed wireless backbone to enable service providers to reach [remote] areas and rural communities," he adds.

FSO systems are also being used to provide back-up in situations where fibre or other conventional connections are readily available. For example, after the September 11th tragedy, FSO was deployed when existing networks were cut.

Regionally, vendors have also adapted the way they market the technology following the telecoms slowdown and bandwidth glut, and are emphasising FSO's role as an alternative if networks go down.

"We came to the market with the idea to solve bottlenecks in the optical ring and GSM networks," says Malek Charles Akilie, director of sales for the Middle East with Silicon Valley-based FSO start-up, Lightpointe. "Now, optical bandwidth has exploded and DWDM has solved a lot of the bottleneck problems in the core network, but we've been able to play on that in terms of extending from those rings and in terms of disaster recovery," he adds.

Similarly, FSO vendors are seeing opportunities open up as mobile operators begin to offer more bandwidth-hungry multimedia services and rollout new network technologies; investments that were delayed as wallets were tightened during the slump. "Back in 1997, everyone thought 3G was just around the corner, but it's only recently that GSM providers are really starting to look at GPRS and UMTS from the business side," Akilie says.

"[As a result,] as they move to full coverage or from GSM into GPRS, we're seeing a need for more cell sites and cell sites [that are] closer together, and a need for more than a couple of E1s," he adds.

In turn, Lightpointe says it is undergoing interoperability testing with local mobile operators, Orascom and Saudi Telecom, in preparation for their GPRS and UMTS deployment. However, it is not just the operators that are showing an interest.

For example, the last few months have seen Lightpointe secure strategic alliances with Huawei, Siemens, and Cisco.

The latter has made an investment in the vendor, while Siemens is currently using Lightpointe for disaster recovery applications in Europe. The deal with Huawei involves the Chinese firm distributing the vendor's products in its home country.

However, despite these advances, FSO's limitations still remain. While terrestrial fibre transmits data over a relatively predictable medium, FSO's performance can be significantly affected by bad weather and other factors outside of vendors and operators' control.

As a line of sight technology, FSO is also subject to obstructions that can block signals and disturbances that can move transmitters and receivers out of kilter.
The major challenge, though, to FSO is fog or, more specifically, the water droplets contained within it that can modify light's characteristics and hinder its passage. This is also the case with absorption, which happens when water molecules suspended in the air decrease the power density of the laser beam.

Other things that can decrease FSO's performance are as diverse as birds straying into beams, rain, warm air rising from man-made heating ducts, and building shifts or tremors that can upset the alignment of transmitters and receivers. Additionally, alignment with the sun and other factors more relevant to the region can have an effect. "In the Middle East, clearly dust, sand and extreme heat conditions are concerns," says Akilie.

FSO vendors have attempted to tackle these problems in a number of ways. For instance, the launch of Flightstrata-G, Lightpointe's latest product in June, was accompanied by claims of full-duplex bandwidth at distances of up to 1,000 metres and new features, including four transmitters and receivers as well as wider beams to take building sway and movement into account.

"We built the [product] to have redundancy in the system over different paths, using multiple lasers, so you don't have a single point of failure," says Akilie. "[The system] also widens the beam [and has] automatic adjusters, which readjust the lasers every three or four seconds," he adds.

fSONA's new E Series range, announced at the ITU Telecom World exhibition in Geneva in October, also includes two high-powered lasers, rather than one, and is being promoted for connections of up to 4,600 metres.

Meanwhile, systems that transmit via light emitting diodes (LEDs), rather than lasers, are also being looked at by various FSO vendors. Although perceived to be more applicable to shorter distance and lower speed connections, LEDs, like light-bulbs, transmit a wider beam so are apparently less vulnerable to transmitters and receivers shifting out of line.
"We are looking to deploy LEDs for low-cost, 'point and go across the road'-type connections," says PAV FSO's Emerson.

Aside from technical improvements, however, an emphasis is also being called on for changes to the way vendors market the technology, as well as attempts to cast it in a more realistic light.

"FSO is a technology a lot of companies have tried to oversell and we don't find that the telecoms operators buy [that]," says Emerson. "We've improved the sensitivity of our receivers and the output and capability of our transmitters - but at the end of the day you can't change the laws of physics," he adds.

Instead, part of the problem seems to be image. While vendors have succumbed to the temptation to overplay the technology's capability in the past, its future could be brighter if estimates of distance and reliability are cut down to size. "We can achieve ranges of four or five kms but the operators really only look at FSO over small distances anyhow," says Emerson.

A certain amount of realism, therefore, seems to be the way forward for FSO, so that it can be properly applied to situations where it actually works better than the alternatives. If this means its future is merely filling in gaps or backing up existing networks, then vendors say 'so be it.'

"If you can use fibre, use fibre, because it is not weather sensitive and doesn't care about electromagnetic or heat conditions," says Akilie. "[However,] cutting across roads and motorways and digging city streets is incredibly difficult and in some cases impossible, so the need for this bottleneck to be removed is still there," he adds.

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