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Infrared Laser Communication Links
Frequently Asked Questions
Is the LightStation product line an infrared communication system? What is the operating wavelength?The LightStation is an infrared communication system. Depending on the customer requirements on speed and range it uses either high power light emitting diodes (LEDs) or high power laser diodes ((LDs). The operating wavelength is in the near infrared region of the electromagnetic spectrum at a wavelength around 800 nanometers. What are the advantages of using infrared communication instead of other wireless technologies?Infrared communication offers a much higher bandwidth than other wireless solutions such as spread spectrum or microwave links. Infrared communication does not require FCC approval. Infrared technology is jamming resistant and has a much higher signal security than other wireless solutions. What is the recommended range of the product?The recommended maximum range of the LightStation is 4 km (2.5 miles) at 10 Mbps. For higher speed applications up to 155 Mbps the recommended maximum range is 2 km (1.25 miles). What are the power requirements?LightStation requires only about 12 Watts (maximum) per unit at 115 or 230 VAC. We provide the option to choose also voltages between 12V - 72 V to operate the link unit. How are the links connected to the network?The connection to the network is done by using two multimode (50 or 62.5 mm) optical fibers (send and receive). We recommend to terminate the fiber with standard ST-fiber connectors but we also provide adapters to other types of standard connectors. Can I monitor the performance of the LightStation link?The LightStation can be equipped with an optical management interface (OMI) that connects to the RS-232 port of a PC computer. A windows based program allows to monitor the link performance and reports various status informations. This module can be also connected to an SNMP interface. What about lightning strikes?Contrary to many other wireless communication products, the LightStation has a built-in network isolation from lightning strikes due to fiber optic cabling. What is the physical size and weight of a link unit?The LightStation comes in two versions. The shorter distance links (up to 600 m or 2000 ft.) is (135x165x500) mm and weights 4.5 kg (10 lbs.). The longer distance links (up to 4km or 2.5 miles) is (290x290x470) mm and weights 12 kg (25 lbs.). How does weather affect performance?The effects of weather on the performance of a LightStation system vary as the severity of the weather varies. The receiver margin of the system is about 30 dB. This value is important because rain, snow, fog etc. are changing the attenuation of the atmosphere. A rainfall of 1 inch/h roughly corresponds to an attenuation of 9 dB/km. At a one kilometer range, the systems will operate under the following conditions: a rain rate of about 3 inches per hour, a wet snow rate of less than 2 inches per hour, a dry snow rate of less than 1 inch per hour. In fog the visibility must be greater than 90% of the link distance. What effect does sunlight have on the LightStation link?The LightStation systems use narrowband optical filters to minimize the effect of direct sunlight. Although if possible we recommend that the laser systems not be mounted in a direct East-West orientation to avoid the effects of direct sunlight. Direct sunlight into the front of the unit can result in short periods of time when the receiver will be inoperable due to saturation of the receiver photo diode. These outages can last for several minutes depending on the time of the year and the angle of the sun in the sky. The system will fully recover once the sun is out of the angle of view of the receiver or transmitter. Our experienced engineering team will provide you with installation help on how to mount the link units. What effect does scintillation (heat shimmer) have?Scintillation or heat shimmer imposes a low frequency variation on the amount of light detected by the receiver. If the amount of light detected falls below the required light threshold of the receiver, short bursts of errors will occur. Networks such as Ethernet and Token Ring will retransmit this lost data. The systems are designed to minimize the effects of scintillation. Proper site and optical path selection can eliminate the effects of scintillation entirely. We will provide you with installation help on how to do this. Are special tools required for installation?Only a few simple hand tools and drills are required to install the LightStation laser link. The links are equipped with a binocular for coarse alignment. For the final fine adjustment the system is equipped with an acoustic alignment help (1 KHz tone) and an optical power level meter. How should the LightStation be mounted?Ideally, the units should be mounted on the corner or the wall of the building to which they are attached and preferably to masonry construction or a brick wall. In all cases the base of the mounts must be attached to the supporting structure. The supporting structure cannot be wood or sheet metal. We provide a solid and laboratory tested (test report available upon request) mount for either roof or wall installation. Does the LightStation come in a water-proved housing?All our units are built in weather-tight, self-contained housing equipped with sunshields. We only use high quality and high performance aluminum and steel materials (no plastics!) to manufacture our links. No external housing is required to mount the links outside. Can the LightStation operate through glass?The LightStation can operate through glass, however, for each glass surface the light intensity will be reduced by approximately 4%. The glass should not be coated with an infrared reflecting or absorbing material since all light may be lost. Also, as the angle of the beam with the glass increases, more and more light is reflected until the critical angle of approximately 42 degrees is reached. Above the critical angle all of the light is reflected off the glass and no signal will reach the receiver. Is it possible to connect a PBX system and the data network by using the LightSta tion link?In combination with the LighStation link we offer a multiplexer that allows to run full speed 10 Mbps Ethernet and up to four T1/E1-lines in parallel. Can the LightStation system be used for temporary installations, back-up and disaster recovery?The LightStation systems are very light-weight (10 and 25 lbs., respectively) and may be mounted on tripods for temporary installations. The link may easily be relocated as required. Organizations have purchased these systems for use as a permanent or temporary back-up in the event of fiber optic or copper cable breaks in high data rate applications or where rapid deployment recovery solution is critical. What happens if a bird flies through the beam?Birds can see the infrared region of the spectrum and will usually avoid the beam. Depending on where the bird flies through the beam (close to the transmitting link where the beam diameter is still small or close to the receiving link where the beam diameter is already very large compared to the bird size), a momentary interruption might occur resulting in a retransmission of the data in Ethernet or Token Ring. In any case the bird will not be harmed. |
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