news / tech talk

Light-based Communication

by Lee LeClair
As seen in Inside Tucson Business

Many business owners in Tucson have several offices within the city and some of those locations are not in a convenient place for data network connectivity. If you have a primary administrative office with a network connection but you also need to reach a satellite office or other location (e.g., motorpool, warehouse, etc.) then your options tend to be pretty limited. Depending on the distance, options might include using a wireless connection, a point-to-point wireless extender (or “cantenna”), stringing Ethernet cable outdoors, microwave shots, trenching and laying cable, or shooting a beam of light. The wireless solutions tend to be very distance limited and provide a fairly meager. As an example, a common 802.11g (54Mbps max) typically has a range of about 35 meters and a throughput of about 19Mbps if you do not have too many interference problems. These systems operate in the crowded 2.4GHz range along with Bluetooth, cordless phones, baby monitors, microwave ovens, and all the other people using wireless (bring up a wireless monitor in a tall office building and make note of how many networks there are). Since wireless network use broadcast radio waves, you must be sure to enable the strongest encryption standards available to keep your network private as well.

If the distance you need to cover is anything like 100 meters or more, your options quickly decline. It is too far for stringing CAT 5 cable. You will most likely try checking (again) on the availability of cable modem coverage, DSL, a commercial ISP dedicated line or maybe even using a mobile phone with an Internet link (e.g., T-mobile and GPSR, Verizon or Sprint with Broadband). If cable or DSL is available then it will likely be the most affordable option and the easiest to setup. If the site is bandwidth-remote (i.e., no connectivity available), then the mobile telephone or Laptop wireless telephone card option may be viable but will be quite slow (600kbps-1.4Mbps download for CDMA; worse for GSM) for a shared network and some services may terminate your data connection if they discover what you are doing (e.g., read Verizon’s license agreement very carefully). That leaves you with microwave shots (a fairly complex endeavor), trenching (rarely possible depending on what is in-between and how far it is), and possibly one other option.

The other option is one you may not be familiar with. It is called Free Space Optics (FSO) and basically consists of directional light devices in a line-of-sight pair. These systems look like surveillance cameras and basically shoot light at each other through the air. The distances that can be covered are up to 4 kilometers (about 2.5 miles). Bandwidth is anywhere from 100Mbps to 1.25Gbps per link (you can setup several in parallel too) depending on the system. Further, the connection is full duplex so throughput is throughput is much higher than wireless. They are pretty straightforward to install since they typically connect right into your copper LAN with standard CAT 5 or 6 cable. They are secure because they broadcast only through a very physically narrow beam and even that is typically encrypted. Because it is light, there is no FCC (or equivalent) regulation on it. This has made these systems very popular internationally where transmissions are very tightly controlled. A pair of FOS transceivers capable of 100Mbps throughput over a 500 meter distance will cost somewhere around $4000-5000 but once established do not require a recurring monthly cost. So keep all the costs, complexities, and transmission options in mind when determining what makes the best sense for your business.

Lee Le Clair is the CTO at Ephibian. His Tech Talk column appears the third week of each month in Inside Tucson Business