Citm805 - Free Space Optics

CITM805: SPECIAL TOPICS IN IT Professor Robert Hudyma Ryerson University

Brian Orlotti Mike Warren Farhan Yousaf

980979207 981656705 981676125

Free Space Optics (FSO) Using “Free Air” As Fiber

Table of Contents 1.0 Introduction________________________________________________________________________________ 1 2.0 Technology Overview ________________________________________________________________________ 2 2.1 Factors Affecting FSO Performance ____________________________________________________________ 3 2.2 Advantages of FSO __________________________________________________________________________ 3 2.3 Disadvantages of FSO ________________________________________________________________________ 4 3.0 Analysis of Deployment Options _______________________________________________________________ 5 4.0 Business Case Scenario _______________________________________________________________________ 7 5.0 Conclusion _________________________________________________________________________________ 7 6.0 Annotated Bibliography ______________________________________________________________________ 8 7.0 Additional Sources _________________________________________________________________________ 11 8.0 Appendix _________________________________________________________________________________ 11

Free Space Optics (FSO) 1.0 Introduction Free Space Optics may sound like a new buzz-word-enabled technology that seems to have very outer-space connotations, but in reality it’s an old technology that was originally developed by the military over 30 years ago. In technical terms, Free Space Optics is an optical wireless, point-to-point, line-of-sight high bandwidth broadband solution with data rates ranging from 1 Mbps to over 1.25 Gbps that provides the best solution to the “lastmile” needs of bandwidth hungry applications created due to the convergence of telecommunications and data communications. What makes this technology so special is the compelling economic advantages and the relative speed and ease of deployment when compared to typical fiber or copper connectivity. Most people think that optical communication is only possible through a fiber. However, light can be made to travel through air as its medium for a lot less money than with typical fiber optic deployments. The term Free Space Optics (FSO) may be slightly misleading, as a more precise and self-describing terminology could have been “fiber-free” or “fiber-less” optics. Nonetheless, we will stick with the industry standard terminology of FSO through out this paper. It is worth mentioning that one of the three leading players in the FSO market is fSONA1, based out of Richmond, British Columbia.

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Please see Appendix A for a press release on fSONA’s product offerings.

2.0 Technology Overview This technology uses powerful infrared beams to transmit data through the air between transceivers, or link heads that are typically mounted on rooftops or behind windows. It works over distances of several hundred meters to a few kilometers depending on atmospheric conditions. The transceiver works in the electro-magnetic spectrum above 300 GHz (which includes infrared) that is unlicensed worldwide and does not require the payment of spectrum fees to any governmental bodies. The radiated power, however is subject to limitations established by the IEC60825-1 standard established by International Electrotechnical Commission (IEC). In the United States, the governing body is The Center for Devices and Radiological Health (CDRH) which is part of the Food and Drug Administration (FDA). Currently, the IEC60825-1 standard is being ratified and CDRH is expected to adopt the new revised standard. So in the near future there will be a single worldwide standard for these devices. The lasers in these devices work at one of two wavelengths, 850nm or 1550nm. The former, 850nm lasers are much less expensive (around 30$) than the 1550nm variety which cost around $1000. For short or moderate distances, the 850nm lasers suffice given the price differential. However, the 1550nm beams that are of longer wavelengths are allowed to operate at higher power (almost twice the amount of 850nm) because this boosts “link lengths” by factor of at least 5. One reason why 1550nm can be operated at higher power is that the infrared radiation at this wavelength tends not to reach the retina of the eye and is mostly absorbed by the cornea2. Therefore, for long distances, high bandwidth, and poor propagation conditions like fog, 1550nm lasers are a no-brainer choice. Following diagram illustrates the inner workings of a typical FSO transceiver:

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Please see Appendix B for a whitepaper on Lasers and Eye Safety.

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2.1 Factors Affecting FSO Performance There are functional limits to any emerging technology, and optical wireless systems are no exception. The challenges affecting FSO in terms of reaching 99.999% availability (also known as the five nines) manifest themselves as environmental phenomena that vary significantly from one area to another. Without delving into too much micrometeorological definitions and theory, we will discuss two major factors: 1. Attenuation: Adverse Weather Conditions The greatest loss mechanism is caused by fog particles3. The affect of fog is entirely analogous to attenuation that is suffered by traditional RF wireless systems due to rainfall. However, this technology is relatively unaffected by rain or snow. This effect is dealt with by simply increasing the transmitted power. 2. Swaying Buildings Another hurdle in the way of deploying free-space optics links on tall buildings or towers is sway due to wind or seismic activity; storms and earthquakes can also cause enough movement to affect beam aiming. This problem is dealt with in two ways, beam divergence and active tracking4.

2.2 Advantages of FSO Free-Space Optics (FSO) holds many distinct advantages over other high-speed communications technologies. The fact that FSO uses Terahertz (THz) infrared lasers rather than electrical signals to send packetized data allows for immense bandwidth. FSO equipment currently supports speeds ranging from OC-3 (155 Mbps) to 1.25 Gbps. Some vendors have demonstrated links running as high as 3 Gbps. FSO equipment also benefits from simplicity and rapid deployment time. FSO gear consists mainly of laser terminals which are installed on rooftops or mounted in windows. This is a massive advantage over another technology traditionally seen as bridging the “last mile” -- fibre optics. Fiber Optic installations have proven to be extremely timeconsuming because of the need to negotiate right-of-way permits and to physically dig to lay the cable. FSO equipment can be setup within days, as opposed to months or even years for fiber. FSO’s simplicity and rapid installation provides its greatest advantage; low cost. With no right-of-way permits to secure, and no digging required, FSO can offer ultra-high data rates at a very low price. US telecom giant Qwest recently began installing FSO equipment from LightPointe at a cost of about US $8,000 per link5. With fiber-optic installations running from the hundreds-of-thousands to the millions of dollars, FSO holds an incredible advantage.

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Referred to as Mie scattering in micrometeorological terms This technique was effective during an earthquake in Seattle, where Terabeam had its equipment continue to operate without a link break-down. 5 th Greene, Tim. (2001). Qwest tries out free-space optics service. Retrieved March 9 , 2002 from Network World website: http://www.nwfusion.com/edge/news/2001/125510_09-24-2001.html 4

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FSO also holds some additional advantages over fiber, microwave, and other technologies. FSO terminals are strictly physical layer devices. As such, existing protocols (Ethernet, TCP/IP, ATM, etc.) require no modifications and no additional software is required. Also, FSO terminals use laser diodes and photodetectors similar to those used in fiber optic equipment (DWDM MUXes, hubs, NIC’s, etc). This allows use of off-the-shelf equipment and easy integration with existing fiber installations. In addition, FSO communicates in the Terahertz frequency band—which is currently unregulated. Because of this, FSO eliminates the need for expensive spectrum licenses (from CRTC or FCC).

2.3 Disadvantages of FSO Although FSO holds a great deal of promise, there are several drawbacks which must be addressed if it is to gain wide acceptance. FSO uses high-frequency lasers to transmit data and, as such, is a Line-Of-Sight (LOS) technology. LOS systems require an unobstructed signal path from sender to receiver. Interruption of a laser signal can come from several sources. As discussed previously, these include: ƒ

Inclement weather (rain, snow, fog)

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Building sway (due to winds)

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Transient obstructions (flocks of birds, locust swarms, etc.)

To deal with transient obstructions, FSO laser nodes are designed to automatically reduce power (so the beam may travel through the object) to 1 percent until the obstruction has cleared6. Another drawback of FSO is that of limited range. FSO’s gigabit-per-second speeds can only be provided reliably over a distance of 1-2 kms. This can be addressed however, through proper network design. FSO links can be arranged in mesh or ring topologies to decrease link distances and provide multiple transmission paths.

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Allen, Doug. (2001). The Second Coming of Free-Space Optics. Retrieved March 9 , 2002 from Network Magazine website: http://networkmagazine.com/article/NMG20010226S0007

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3.0 Analysis of Deployment Options Free Space Optics have in fact been used for over a decade in very limited use (Allen, Network Magazine), however their prevalence in end-user solutions has only just begun. The “Last Mile Problem” afflicting fiber optic technology seems to be easily solved with a FSO solution. Without expensive rights of ways, building permits and the actual installation process of digging up roadways, FSO usually repays itself within one year (Allen, Network Magazine). Current FSO technologies offer transmission rates of up to 2 Gbps7, with faster systems still under development. Lucent’s OpticAir DWDM (dense wave division multiplexing) promises further increases in speed to 2.5 Gbps or more (Lucent). FSO is seen as a major player in connecting smaller and medium sized businesses with true broadband access in the OC-3 range (155 Mbps) and above which currently do not have a fiber connection. FSO can be used to provide both Internet and private, corporate network access. FSO links have been available in the past but were rejected by customers and providers due to perceived instability and reliability of the system (Allen, Network Magazine). However, successes of FSO in specialized applications (such as television production8 have proven that the technology is ready to be adapted for business applications, offering close to mission-critical levels of reliability. Mesh connections can also be developed for multi-site links and to increase the number of available paths in case of a disruption to one link site. In-house uses of FSO can be either for a primary link or a backup system to ensure connectivity if the primary link (fiber or otherwise) fails. It can also be used in disasterrecovery situations. After the September 11 attacks on New York, Terabeam installed FSO access for customers such as Merrill Lynch, who had lost connections between offices due to the destruction of Verizon’s telecom facilities located near the World Trade Center (Kagan, Washington Post). The quick deployment of the FSO connection allowed the company to resume business much faster than if it waited for the fiber links to be restored. FSO systems can also be teamed up with microwave equipment to provide a fail-safe, completely wireless solution for connectivity. FSO providers in major cities (at least now) tend to be smaller, niche-driven companies such as AirFiber, with its OptiMesh connection system (see Appendix C). In such a system, a central hub transceiver creates a mesh connection with transceivers on neighboring building’s roof tops. In addition, major telecom service providers have begun to jump on the FSO bandwagon, and are now offering their own services to business clients. Qwest started offering such a service in Denver in September 2001 (Green, NetworkWorld Fusion). Qwest’s service is roughly equivalent to OC-3, at 155 Mbps. While this is not cutting edge technology, the

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OrAccess claims speeds of 10Gbps, but there is insufficient evidence of this speed being achieved in real-world business conditions. 8 See Lucent article regarding HDTV site broadcast transmissions to central hub.

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service provides bandwidth that is more than sufficient for small to medium sized businesses, for either WAN or Internet connectivity9. Local loop connections from service providers would consist of a hub transceiver (preferably at high elevation to maximize customers in the line of sight) and customer transceivers either mounted in windows or on building rooftops. However, the primary drawback of service provider FSO is that it only can serve customers who are close enough to their central hubs. The provider would have to rent and invest in equipment for many additional roof-top locations if access is to be provided to secondary locations, and this is when FSO starts to lose its cost advantage compared to fiber.

3.1 Costs of Deployment When choosing to deploy Free Space Optics connectivity solutions, customers can choose either an in-house solution (provided through a FSO vendor) or one that is purchased through a service provider. While some service providers are now offering prepackaged and transparent FSO solutions to enterprise customers, there is currently insufficient information on pricing available to the general public. It is our assumption that this lack of information is caused by telecom providers not specifically marketing FSO solutions, but transparent solutions where FSO may be employed. In-house solutions are only really justified when the organization has two buildings within the range of the FSO system, such as the Merrill Lynch example. Exact pricing (aside from eBay) is not available for in-house solutions offered by vendors such as Air Fiber and Terabeam, who instead encourage potential customers to call to speak with a salesperson – possibly to avoid competitors from being knowledgeable about their pricing strategy. However, in the Network Magazine article, AirFiber is quoted as providing a price of $20,000 for a complete solution to link two buildings, presumably at 155Mbps. The actual installation of a FSO system usually takes four hours or less by two technicians (AirFiber). In contrast, Network magazine reports that a similar capacity link provided by fiber optics would cost over $200,000 to install, plus leased line charges from the telco provider. In addition, fiber installations have a lead time of between four months to a year, while FSO can by deployed in two days or less.

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Research on eBay has shown that such a FSO equivalent to the one Qwest offers subscribers (~155 Mbps) costs less than $6000 USD in capital expenses if installed by the customer.

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4.0 Business Case Scenario Although FSO services are now beginning to be offered by telecom providers and FSO specialists in major metropolitan areas, there is no such system that integrates FSO and WAN capabilities. The service would be somewhat similar to AirFiber’s OptiMesh system (see Appendix C), however with links to service access points in other cities and to the Internet. Additionally, the service would be marketed differently What we propose is a series of interconnected FSO providers that offer WAN connectivity to organizations that have locations in more than one of the service areas. Linking the access points would be a high-speed fiber backbone leased from a major telecom provider. This would provide a truly integrated service to customers, reducing both costs and complexity in their connectivity needs. Plus, the mesh connection would provide redundant connections in case of problems with one link. FSO links could be used to transmit both data and voice (VOIP) over a VPN to other locations that are also connected via FSO. For example in conjunction with a VOIPcompatible PBX, this could increase call-centre personnel efficiency by routing calls to the location that has a lower holding time. Such a service does not necessarily have to be marketed as a FSO service. Most customers are concerned only with pricing, speed and reliability, not the actually method of transmission.

5.0 Conclusion The lower overall cost and particularly quick deployment speed makes FSO a very attractive option, but not for all customers. The ideal FSO customer has two locations within 1km of each other and has a completely unobstructed line of sight. For fringe applications where the distance is close to the maximum supported by the transceiver or with poor line of sight/poor weather conditions, the savings in costs may well be offset by lower speed and decreased reliability that FSO would offer in such installations.

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6.0 Annotated Bibliography 1. Allen, Doug. (2001). The Second Coming of Free Space Optics. Network Magazine, March 2001 Free Space Optics, or FSO links have actually been used since the late 1980s, but are only now gaining popularity for business applications. Why? In the past, perceived reliability problems and limited installation sites had stifled demand for FSO. But now, it is coming back into focus a solution for the all-important “Last-mile problem” of proving fiberclass broadband connections to business customers premises. Allen introduces prominent vendors and service providers such as LightPointe, AirFiber and Terabeam. There is also discussion of the current technical specifications of FSO systems and their capabilities, and which types of applications are good and not so promising uses for FSO. Also raised is the point that major telecom providers are now considering FSO as a service delivery option, resulting in huge projected increases in FSO equipment sales during the next five years. The article brings together a balanced viewpoint on both the good and bad points of FSO applications, including possible health implications. Some FSO vendors have claimed that their lasers emit low levels of power that are not harmful but the author challenges them to prove these claims. Regulation also comes into play, although currently the frequencies that FSO utilizes (in the terahertz range) are not regulated, they may become regulated if the technology gains widespread acceptance and congestion occurs. 2. Greene, Tim. (2001). Qwest tries out free-space optics service. Retrieved March 9th, 2002 from Network World website: http://www.nwfusion.com/edge/ news/2001/125510_09-24-2001.html Qwest Communications, a well known service provider in the states is using free-space optical gear to supplement its point-to-point broadband service offerings, bringing corporate users high-speed connections that previously were impractical. As an emerging technology, Qwest’s adoption is critical in the success of this new technology. It will take at least several other companies to adopt this technology before one can be reasonably sure of its long term survivability. The FSO gear will be used in customer networks where traditional options such as optical fiber are unavailable or would take too long to install. Gaining permits and rights of way to run fiber can take months, whereas free-space lasers can be set up rapidly, mounted on rooftops or inside windows. Broadband wireless had been considered the front-runner to address fiber unavailability, but licensing and funding problems with wireless carriers slowed this market. In the meantime, the price of FSO gear has dropped dramatically, making it more attractive. Qwest will use equipment from LightPointe that reaches 1.25GBps, but for now, will run the equipment at 155MBps. According to John Griffin, CEO of LightPointe, an OC-3 free-space link that cost $25,000 to $30,000 two years ago now costs $8,000 per link, indicating the improvement in both technology and price structures. Qwest is building fiber networks in 25 cities outside its home states where it is the predominant local exchange carrier. The provider says FSO is being used in at least one corporate user's network supported by Qwest, but it would not identify the customer.

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3. Kagan, Jeff. (2001). Free-Space Optics Come to Rescue of NY Firms. Retrieved March 9th 2002 from Washtech website: http://washtech.com/news/jkagan/128991.html In the aftermath of the September 11 attacks, the ramifications in terms of human life and infrastructural are staggering. Services providers like AT&T, WorldCom, and Sprint, and equipment makers like Lucent, Nortel, ADC and Alcatel worked virtually round the clock to restore the services and put their customers back into business. Imagine not having any connectivity between your various offices, and how this would affect your daily operations. In particular, one company, Merrill Lynch could not function at all and needed to be reconnected to its offices immediately. Executives and engineers from a young start-up company, Terabeam, based out of Seattle Washington, flew in to the rescue the very next day. Within a week they had a single 1-gigabit link up and running, connecting Merrill Lynch buildings in lower Manhattan and Jersey City. 4. Lucent Corporation, Lucent Technologies teams with ABC Sports to transmit uncompressed HDTV signals during Super Bowl XXXIV HD broadcast, Retrieved March 9th, 2002 from Lucent website: http://www.lucent.com/press/0200/000203.nsa.html During the last Super Bowl event, ABC Sports used Lucent’s WaveStar OpticAir system to transmit uncompressed HDTV signals from a remote camera to a mobile production truck, built and outfitted by Panasonic and located at the Georgia Dome. ABC used Lucent’s technology to transmit so-called “beauty shots” during the event’s HDTV broadcast. The HD camera was positioned on a building one-mile away from the stadium, and provided images of Georgia Dome and the Atlanta skyline. Utilizing the high-bandwidth of this technology enabled ABC to minimize the number of times the video signal had to be compressed, resulting in much high-quality transmission of the video and for re-broadcast over satellite for worldwide distribution. Until now, ABC was required to apply for FCC licenses to transmit the video signals over a local radio frequency, which can be not be costly but also have a limited maximum capacity of 155 MBps whereas transmission of these HDTV signals require a transmission capacity of nearly 1.5GBps. Thus, ABC needed to compress the signals before they were transmitted from the camera to their mobile production trucks, resulting in lower image quality (due to lossy compression schemes) as these same images were then recompressed for satellite transmission. Lucent’s WaveStart OpticAir transmission capacity is a whopping 2.5GBps, enough to satisfy virtually any media driven demand with room to spare. 5. Mullen, R.A, H.Wildebrand, et al. (No date). Wireless Optics Protection of Fiber via SONET Ring Closure. Retrieved from LightPointe Communications. Inc. website: http://www.lightpointe.com A free-space laser link closes an otherwise all-fiber SONET ring, demonstrating for the first time the feasibility of using wireless optics as a backup to fiber in an application demanding the highest levels of statistical availability and sub-50-ms protection-restoral times. This experiment demonstrates that protocol-transparent wireless optical links can be readily internetworked with industry-standard fiber-based protection protocols to achieve SONET restoral times in the event of a fiber cut.

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By using the wireless optics as a back-up to fiber rather than as the primary link, endusers are normally protected from the unavoidable burst errors and outages that can arise on a wireless optical link in the event of anomalously poor atmospheric visibility or unanticipated line-of-sight obstructions. While an all-fiber SONET ring operating over physically diverse paths is generally preferred, hybrid fiber/air rings operating over physically-diverse paths (fiber as one path and air as the other) will easily meet or exceed existing Bellcore availability standards for SONET rings. The hybrid part-fiber, part-air ring advantageously protects customers from fiber cuts (a.k.a. “backhoe fade”) and may be preferable to over service via either an unprotected fiber spur or over a “collapsed” fiber ring made up of fiber segments sharing a common conduit. The experiment is performed at an OC-12 (622 Mbps) data rate in a point-to-consecutive point configuration which demonstrates the use of a relay site to work-around a line-of-sight obstruction. 6. Wildebrand, Heinz A. and Ghuman, Baksheesh S. (2001). Fiber Optics without Fiber. IEEE Spectrum, August 2001 In an industry where fiber optic cable is the standard for all your bandwidth woes, one could never have imagined that the virtually the same bandwidth at a fraction of the cost could be provided with inexpensive equipment and using “free air” as the medium. It is no wonder that even with the broad availability of fiber in urban centres, cost remains a formidable obstacle to overcome. Companies like 360 Networks have risen, and then crumbled due to a huge saturation of the fiber bandwidth market. Known within the industry as free-space optics (FSO), this form of delivering communications services has compelling economic advantages. Although it only recently, and rather suddenly, sprang into public awareness, free-space optics is not a new idea. It has roots that go back over 30 years--to the era before fiber-optic cable became the preferred transport medium for high-speed communication. In those days, the notion that FSO systems could provide high-speed connectivity over short distances seemed futuristic, to say the least. But research done at that time has made possible today's freespace optical systems, which can carry full-duplex (simultaneous bidirectional) data at gigabit-per-second rates over metropolitan distances of a few city blocks to a few kilometers. 7. Wildberand, Heinz A. (2002). Free Space Optical Transmission Security. Retrieved March 9th, 2002 from LightPointe Communications Inc. website: http://www.lightpointe.com Network security is one of the major concerns for any business or organization transporting sensitive and confidential information over the network. Such network security concerns involve the lowest network layer, typically referred to as the physical layer (layer one), as well as higher software layers of the networking protocols. Most of the interception activity by outside intruders occurs within higher protocol software layers. Password protection or data encryption are examples of counter measures to protect the network from outside and unwanted tampering. Intrusion of the physical layer itself can be another concern for network operators, although it is a far less likely target for unauthorized access to networking data. This can be a threat if information is transported over a copper-based infrastructure that can be easily intercepted, but Free-Space Optics (FSO) transmission is among the most secure connectivity solutions, regarding network interception of the actual physical layer.

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7.0 Additional Sources ƒ

AirFiber Corporation (2002). AirFiber OptiMesh. Retrieved from AirFiber website: http://www.airfiber.com/products

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eBay Auctions (2002). Free Space Optics Wireless 155Mbps Laser Link. Retrieved from eBay website: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2008684190

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Terabeam Corporation (2002). Solutions for carriers. Retrieved from Terabeam website: http://www.terabeam.com/sol/car_700.shtml

8.0 Appendix ƒ

Appendix A: Press release on fSONA’s product offerings.

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Appendix B: Whitepaper on Lasers and Eye Safety.

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Appendix C: AirFiber’s OptiMesh system.

Please see accompanying CD for appendix items (PDF format) in folder \Appendix\.

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