FSO Guide – Free Space Optics, Optical Wireless

FSO (Free Space Optics, Laser, Optical Wireless) Guide

Free Space Optics (FSO) communications, also called Optical Wireless (OW) or Infrared Laser, refers to the transmission of modulated visible or infrared (IR) beams through the atmosphere to obtain optical communications. Like fibre, Free Space Optics (FSO) uses lasers to transmit data, but instead of enclosing the data stream in a glass fibre, it is transmitted through the air. Free Space Optics (FSO) works on the same basic principle as Infrared television remote controls, wireless keyboards or IRDA ports on laptops or cellular phones.

History of Free Space Optics (FSO)
The engineering maturity of Free Space Optics (FSO) is often underestimated, due to a misunderstanding of how long Free Space Optics (FSO) systems have been under development. Historically, Free Space Optics (FSO) or optical wireless communications was first demonstrated by Alexander Graham Bell in the late nineteenth century (prior to his demonstration of the telephone!). Bell’s Free Space Optics (FSO) experiment converted voice sounds into telephone signals and transmitted them between receivers through free air space along a beam of light for a distance of some 600 feet. Calling his experimental device the “photophone,” Bell considered this optical technology – and not the telephone – his pre-eminent invention because it did not require wires for transmission.

Although Bell’s photophone never became a commercial reality, it demonstrated the basic principle of optical communications. Essentially all of the engineering of today’s Free Space Optics (FSO) or free space optical communications systems was done over the past 40 years or so, mostly for defense applications. By addressing the principal engineering challenges of Free Space Optics (FSO), this aerospace/defence activity established a strong foundation upon which today’s commercial laser-based Free Space Optics (FSO) systems are based.

How Free Space Optics (FSO) Works
Free Space Optics (FSO) transmits invisible, eye-safe light beams from one “telescope” to another using low power infrared lasers in the terahertz spectrum. The beams of light in Free Space Optics (FSO) systems are transmitted by laser light focused on highly sensitive photon detector receivers. These receivers are telescopic lenses able to collect the photon stream and transmit digital data containing a mix of Internet messages, video images, radio signals or computer files. Commercially available systems offer capacities in the range of 100 Mbps to 2.5 Gbps, and demonstration systems report data rates as high as 160 Gbps.

Free Space Optics (FSO) systems can function over distances of several kilometres. As long as there is a clear line of sight between the source and the destination, and enough transmitter power, Free Space Optics (FSO) communication is possible.

FSO: Wireless Links at the Speed of Light
Unlike radio and microwave systems, Free Space Optics (FSO) is an optical technology and no spectrum licensing or frequency coordination with other users is required, interference from or to other systems or equipment is not a concern, and the point-to-point laser signal is extremely difficult to intercept, and therefore secure. Data rates comparable to optical fibre transmission can be carried by Free Space Optics (FSO) systems with very low error rates, while the extremely narrow laser beam widths ensure that there is almost no practical limit to the number of separate Free Space Optics (FSO) links that can be installed in a given location.

How Free Space Optics (FSO) benefits you
FSO is free from licensing and regulation which translates into ease, speed and low cost of deployment. Since Free Space Optics (FSO) transceivers can transmit and receive through windows, it is possible to mount Free Space Optics (FSO) systems inside buildings, reducing the need to compete for roof space, simplifying wiring and cabling, and permitting Free Space Optics (FSO) equipment to operate in a very favourable environment. The only essential requirement for Free Space Optics (FSO) or optical wireless transmission is line of sight between the two ends of the link.

For Metro Area Network (MAN) providers the last mile or even feet can be the most daunting. Free Space Optics (FSO) networks can close this gap and allow new customers access to high-speed MAN’s. Providers also can take advantage of the reduced risk of installing an Free Space Optics (FSO) network which can later be redeployed.

The Market. Why FSO? Breaking the Bandwidth Bottleneck
Why FSO? The global telecommunications network has seen massive expansion over the last few years. First came the tremendous growth of the optical fiber long-haul, wide-area network (WAN), followed by a more recent emphasis on metropolitan area networks (MANs). Meanwhile, local area networks (LANs) and gigabit Ethernet ports are being deployed with a comparable growth rate. In order for this tremendous network capacity to be exploited, and for the users to be able to utilize the broad array of new services becoming available, network designers must provide a flexible and cost-effective means for the users to access the telecommunications network. Presently, however, most local loop network connections are limited to 1.5 Mbps (a T1 line). As a consequence, there is a strong need for a high-bandwidth bridge (the “last mile” or “first mile”) between the LANs and the MANs or WANs.

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A recent New York Times article reported that more than 100 million miles of optical fibre was laid around the world in the last two years, as carriers reacted to the Internet phenomenon and end users’ insatiable demand for bandwidth. The sheer scale of connecting whole communities, cities and regions to that fiber optic cable or “backbone” is something not many players understood well. Despite the huge investment in trenching and optical cable, most of the fibre remains unlit, 80 to 90% of office, commercial and industrial buildings are not connected to fibre, and transport prices are dropping dramatically.

Free Space Optics (FSO) systems represent one of the most promising approaches for addressing the emerging broadband access market and its “last mile” bottleneck. Free Space Optics (FSO) systems offer many features, principal among them being low start-up and operational costs, rapid deployment, and high fiber-like bandwidths due to the optical nature of the technology.

Broadband Bandwidth Alternatives
Access technologies in general use today include telco-provisioned copper wire, wireless Internet access, broadband RF/microwave, coaxial cable and direct optical fiber connections (fiber to the building; fiber to the home). Telco/PTT telephone networks are still trapped in the old Time Division Multiplex (TDM) based network infrastructure that rations bandwidth to the customer in increments of 1.5 Mbps (T-1) or 2.024 Mbps (E-1). DSL penetration rates have been throttled by slow deployment and the pricing strategies of the PTTs. Cable modem access has had more success in residential markets, but suffers from security and capacity problems, and is generally conditional on the user subscribing to a package of cable TV channels. Wireless Internet access is still slow, and the tiny screen renders it of little appeal for web browsing.

Broadband RF/microwave systems have severe limitations and are losing favor. The radio spectrum is a scarce and expensive licensed commodity, sold or leased to the highest bidder, or on a first-come first-served basis, and all too often, simply unavailable due to congestion. As building owners have realized the value of their roof space, the price of roof rights has risen sharply. Furthermore, radio equipment is not inexpensive, the maximum data rates achievable with RF systems are low compared to optical fiber, and communications channels are insecure and subject to interference from and to other systems (a major constraint on the use of radio systems).

Free Space Optics (FSO) Advantages
Free space optical (FSO) systems offers a flexible networking solution that delivers on the promise of broadband. Only free space optics or Free Space Optics (FSO) provides the essential combination of qualities required to bring the traffic to the optical fiber backbone – virtually unlimited bandwidth, low cost, ease and speed of deployment. Freedom from licensing and regulation translates into ease, speed and low cost of deployment. Since Free Space Optics (FSO) optical wireless transceivers can transmit and receive through windows, it is possible to mount Free Space Optics (FSO) systems inside buildings, reducing the need to compete for roof space, simplifying wiring and cabling, and permitting the equipment to operate in a very favorable environment. The only essential for Free Space Optics (FSO) is line of sight between the two ends of the link.

Security and Free Space Optics (FSO)
The common perception of wireless is that it offers less security than wireline connections. In fact, Free Space Optics (FSO) is far more secure than RF or other wireless-based transmission technologies for several reasons:
Free Space Optics (FSO) laser beams cannot be detected with spectrum analyzers or RF meters
Free Space Optics (FSO) laser transmissions are optical and travel along a line of sight path that cannot be intercepted easily. It requires a matching Free Space Optics (FSO) transceiver carefully aligned to complete the transmission. Interception is very difficult and extremely unlikely
The laser beams generated by Free Space Optics (FSO) systems are narrow and invisible, making them harder to find and even harder to intercept and crack
Data can be transmitted over an encrypted connection adding to the degree of security available in Free Space Optics (FSO) network transmissions.
Free Space Optics (FSO) Challenges
The advantages of free space optical wireless or Free Space Optics (FSO) do not come without some cost. When light is transmitted through optical fiber, transmission integrity is quite predictable – barring unforseen events such as backhoes or animal interference. When light is transmitted through the air, as with Free Space Optics (FSO) optical wireless systems, it must contend with a a complex and not always quantifiable subject – the atmosphere.

Attenuation, Fog and Free Space Optics (FSO)
Fog substantially attenuates visible radiation, and it has a similar affect on the near-infrared wavelengths that are employed in Free Space Optics (FSO) systems. Note that the effect of fog on Free Space Optics (FSO) optical wireless radiation is entirely analogous to the attenuation – and fades – suffered by RF wireless systems due to rainfall. Similar to the case of rain attenuation with RF wireless, fog attenuation is not a “show-stopper” for Free Space Optics (FSO) optical wireless, because the optical link can be engineered such that, for a large fraction of the time, an acceptable power will be received even in the presence of heavy fog. Free Space Optics (FSO) optical wireless-based communication systems can be enhanced to yield even greater availabilities.

Fog is a major source of attenuation of FSO (Free Space Optics) infrared signals
Fog is a major source of attenuation of FSO (Free Space Optics) infrared signals

Free Space Optics (FSO) and Physical Obstructions
Free Space Optics (FSO) products which have widely spaced redundant transmitters and large receive optics will all but eliminate interference concerns from objects such as birds. On a typical day, an object covering 98% of the receive aperture and all but 1 transmitter; will not cause an Free Space Optics (FSO) link to drop out. Thus birds are unlikely to have any impact on Free Space Optics (FSO) transmission.

Free Space Optics (FSO) Pointing Stability – Building Sway, Tower Movement
Only wide-beamwidth fixed pointed Free Space Optics (FSO) systems are capable of handling the vast majority of movement found in deployments on buildings. Narrow beam systems are unreliable, requiring manual re-alignment on a regular basis, due to building movement. ‘Wide beam’ means more than 5milliradians. Narrow systems (1-2mRad) are not reliable without a tracking system
The combination of effective beam divergence and a well matched receive Field-of-View (FOV) provide for an extremely robust fixed pointed Free Space Optics (FSO) system suitable for most deployments. Fixed-pointed Free Space Optics (FSO) systems are generally preferred over actively-tracked Free Space Optics (FSO) systems due to their lower cost.

Free Space Optics (FSO) and Scintillation
Performance of many Free Space Optics (FSO) optical wireless systems is adversely affected by scintillation on bright sunny days; the effects of which are typically reflected in BER statistics. Some optical wireless products have a unique combination of large aperture receiver, widely spaced transmitters, finely tuned receive filtering, and automatic gain control characteristics. In addition, certain optical wireless systems also apply a clock recovery phase-lock-loop time constant that all but eliminate the affects of atmospheric scintillation and jitter transference.

Solar Interference and Free Space Optics (FSO)
Solar interference in Free Space Optics (FSO) free space optical systems can be combated in two ways. Optical narrowband filter proceeding the receive detector used to filter all but the wavelength actually used for intersystem communications. To handle off-axis solar energy, sophisticated spatial filters have been implemented in CableFree systems, allowing them to operate unaffected by solar interference that is more than 1 degree off-axis.

Free Space Optics (FSO) Reliability
Employing an adaptive laser power (Automatic Transmit Power Control or ATPC) scheme to dynamically adjust the laser power in response to weather conditions will improve the reliability of Free Space Optics (FSO) optical wireless systems. In clear weather the transmit power is greatly reduced, enhancing the laser lifetime by operating the laser at very low-stress conditions. In severe weather, the laser power is increased as needed to maintain the optical link – then decreased again as the weather clears. A TEC controller that maintains the temperature of the laser transmitter diodes in the optimum region will maximize reliability and lifetime, consistent with power output allowing the FSO optical wireless system to operate more efficiently and reliably at higher power levels.

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Free Space Optics Technology

Introduction to Free Space Optics

CableFree FSO - Free Space Optics
CableFree Free Space Optics

FSO is a line-of-sight wireless communication technology that uses invisible beams of light to provide high speed wireless connections that can send and receive voice, video, and data information. Today, FSO technology – pioneered and championed by CableFree’s optical wireless offerings – has enabled the development of a new category of outdoor wireless products that can transmit voice, data, and video at bandwidths up to 1.25 Gbps. Free Space Optics connectivity doesn’t require expensive fibre-optic cable and removes need for securing spectrum licenses for radio frequency (RF) solutions. FSO technology requires light. The use of light is a simple concept similar to optical transmissions using fiber-optic cables; the only difference is the medium. Light travels through air faster than it does through glass, so it is fair to classify FSO technology as optical communications at the speed of light.

History of Free Space Optics

Optical communications, in various forms, have been used for thousands of years. The Ancient Greeks used a coded alphabetic system of signalling with torches developed by Cleoxenus, Democleitus and Polybius. In the modern era, semaphores and wireless solar telegraphs called heliographs were developed, using coded signals to communicate with their recipients. In 1880 Alexander Graham Bell and his assistant Charles Sumner Tainter created the Photophone, at Bell’s newly established Volta Laboratory in Washington, DC. Bell considered it his most important invention. The device allowed for the transmission of sound on a beam of light. On June 3, 1880, Bell conducted the world’s first wireless telephone transmission between two buildings, some 213 meters (700 feet) apart.  Its first practical use came in military communication systems many decades later, first for optical telegraphy. German colonial troops used Heliograph telegraphy transmitters during the 1904/05 Herero Genocide in German South-West Africa (today’s Namibia) as did British, French, US or Ottoman signals.

During the trench warfare of World War I when wire communications were often cut, German signals used three types of optical Morse transmitters called Blinkgerät, the intermediate type for distances of up to 4 km (2.5 miles) at daylight and of up to 8 km (5 miles) at night, using red filters for undetected communications. Optical telephone communications were tested at the end of the war, but not introduced at troop level. In addition, special blinkgeräts were used for communication with airplanes, balloons, and tanks, with varying success. A major technological step was to replace the Morse code by modulating optical waves in speech transmission. Carl Zeiss Jena developed the Lichtsprechgerät 80/80 (literal translation: optical speaking device) that the German army used in their World War II anti-aircraft defense units, or in bunkers at the Atlantic Wall.

The invention of lasers in the 1960s revolutionized free space optics. Military organizations were particularly interested and boosted their development. However the technology lost market momentum when the installation of optical fiber networks for civilian uses was at its peak.

FSO vendor CableFree has extensive experience in this area: CableFree developed some of the world’s first successful commercial FSO links, with world-first achievements including

  • World’s first commercial 622Mbps wireless link:  1997
  • World’s first commercial Gigabit Ethernet 1.25Gbps wireless link:  1999

While fibre-optic communications gained worldwide acceptance in the telecommunications industry, FSO communications is still considered relatively new. CableFree Free Space Optical technology from Wireless Excellence enables bandwidth transmission capabilities that are similar to fibre optics, using similar optical transmitters and receivers and even enabling WDM-like technologies to operate through free space.

How Free Space Optics / Laser Communications Work

CableFree Free Space Optics at London 2012 OlympicsThe concept behind FSO technology is very simple. It’s based on connectivity between FSO-based optical wireless units, each consisting of an optical transceiver with a transmitter and a receiver to provide full-duplex (bi-directional) capability. Each optical wireless unit uses an optical source, plus a lens or telescope that transmits light through the atmosphere to another lens receiving the information. At this point, the receiving lens or telescope connects to a high-sensitivity receiver via optical fibre. This Free Space Optics technology approach has a number of advantages: Requires no RF spectrum licensing. Is easily upgradeable, and its open interfaces support equipment from a variety of vendors, which helps enterprises and service providers protect their investment in embedded telecommunications infrastructures. Requires no security software upgrades. Is immune to radio frequency interference or saturation. FSO Can be deployed behind windows, eliminating the need for costly rooftop rights.

Choosing Free Space Optics or Radio Frequency Wireless

CableFree FSO links in Cairo, EgyptOptical wireless, using FSO technology, is an outdoor wireless product category that provides the speed of fibre, with the flexibility of wireless. It enables optical transmission at speeds of up to 1.25 Gbps and, in the future, is capable of speeds of 10 Gbps using WDM. This is not possible with any fixed wireless or RF technology. Optical wireless also eliminates the need to buy expensive spectrum (it requires no FCC or municipal license approvals worldwide), which further distinguishes it from fixed wireless technologies. Moreover, FSO technology’s narrow beam transmission is typically two meters versus 20 meters and more for traditional, even newer radio-based technologies such as millimeter-wave radio. Optical wireless products’ similarities with conventional wired optical solutions enable the seamless integration of access networks with optical core networks and helps to realize the vision of an all-optical network.

Free Space Technology in Communication Networks

CableFree FSO used in CCTV NetworksFree-space optics technology (FSO) has several applications in communications networks, where a connectivity gap exists between two or more points. FSO technology delivers cost-effective optical wireless connectivity and a faster return on investment (ROI) for Enterprises and Mobile Carriers. With the ever-increasing demand for greater bandwidth by Enterprise and Mobile Carrier subscribers comes a critical need for FSO-based products for a balance of throughput, distance and availability. During the last few years, customer deployments of FSO-based products have grown. Here are some of the primary network uses:

CableFree FSO NetworkEnterprise

Because of the scalability and flexibility of FSO technology, optical wireless products can be deployed in many enterprise applications including building-to-building connectivity, disaster recovery, network redundancy and temporary connectivity for applications such as data, voice and data, video services, medical imaging, CAD and engineering services, and fixed-line carrier bypass.

Mobile Carrier Backhaul

FSO - Free Space Optics InstallationFree Space Optics is valuable tool in Mobile Carrier Backhaul: FSO technology and optical wireless products can be deployed to provide traditional PDH 16xE1/T1, STM-1 and STM-4, and Modern IP Gigabit Ethernet backhaul connectivity and Greenfield mobile networks.

Front-Haul: Mobile Carrier Base Station “Hoteling”

Free Space Optics CPRI Front-Haul for 4G NetworksFSO-based products can be used to expand Mobile Carrier Network footprints through base station “hoteling.” using CPRI interface. Free Space Optics with CPRI enables “front haul” networks where the remote radio heads can be separated by up to 2km from the Base station with a 1.22Gbps CPRI “native” link between them.

Low Latency Networks

CableFree Free Space OpticsFree Space Optics is an inherently Low Latency Technology, with effectively no delay between packets being transmitted and received at the other end, except the Line of Sight propagation delay.  The Speed of Light through the air is approximately 40% higher than through fibre optics, giving customers an immediate 40% reduction in latency compared to fibre optics.  In addition, fibre optic installations are almost never in a straight line, with realities of building layout, street ducts and requirement to use existing telecom infrastructure, the fibre run can be 100% longer than the direct Line of Sight path between two end points.  Hence FSO is popular in Low Latency Applications such as High Frequency Trading and other uses.

Planning a Gigabit Wireless Network

Planning a Gigabit Wireless Network

Planning involves a Gigabit Wireless network requires some consideration to ensure a reliable, high performance network and choice of appropriate technologies.
Some topics include:

Gigabit Wireless Technology
Gigabit Wireless Technology

Site Survey

  • Does Line of Sight (LOS) exist?
  • Desktop Survey / feasibility check
  • Physical Survey
  • RF / Spectral Survey
  • Distances required to cover

Choice of Technology:

Our expert team has over 18 years experience in planning and deploying Gigabit Wireless Networks in over 65 countries, including indoor and outdoor wireless networks.  Our team will be delighted to assist with all aspects of design, planning and deployment.

For more information or questions on Technologies for Gigabit Wireless Networking please Contact Us

Gigabit Wireless Technologies

Gigabit Wireless Technologies

Which technologies can we consider for a modern Gigabit Wireless Network?

Building a Gigabit Wireless Network
Building a Gigabit Wireless Network

Building a modern Gigabit Wireless Network will require choosing the appropriate technology for the precise network requirements.  With wireless, there is no “magic technology” or “one size fits all” approach – a successful network deployment will consider which technologies are best suited

Choosing the correct technology for a Gigabit Wireless Network is essential to ensure you have the very best throughput, capacity and network uptime.

Ask our team of experts who will be delighted to assist in designing an choosing exactly the right products and solutions to meet your needs

Contact us with any questions and requirements:

 

Welcome to Gigabit-Wireless.com!

Welcome to Gigabit-Wireless.com

Welcome – to the informational site for Gigabit Wireless Networking.  We consider the available technologies for Gigabit Wireless Metropolitan Area Networks including:

Welcome to Gigabit-Wireless.com
Welcome to Gigabit-Wireless.com

Feel welcome to read our site and find out more about building modern, reliable and scalable Gigabit Wireless Networks for Wireless Metropolitan Area Networks (Wi-Man), 4G/LTE backhaul networks, Small Cell Backhaul, Corporate Networks and Campus and CCTV wireless networks.

We include technology introduction papers as well as usage cases to guide users in the very latest in Gigabit Wireless technology and deployment.  Modern wireless products can reach 10Gbps or higher capacity.

Applications for Wireless

Welcome - Gigabit Wireless
Gigabit Wireless Technology

Gigabit Wireless networks are used in a wide range of applications which include

  • Safe Cities
  • Smart Cities
  • 4G/LTE Backhaul Networks
  • Broadband Wireless
  • Last Mile Networks
  • Campus Sites
  • Corporate Networks
  • Education networks
  • Metro WiFi
  • Security and CCTV

If you are considering a wireless network with 10Gbps or higher capacity, please ask our team of experts who will be delighted to assist:

For further Information on 10GBE Wireless

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