Availability of AirBridge link
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The product of AirBridge series produced by BTC can serve the user by
providing the transmission link with availability from 99.9% to 99.999%.
While laser beam is propagating in the atmosphere, the energy of
laser beam will be attenuated in different degree subject to different
weather, such as rain, snow, fog and scintillation etc. So while
designing a FSO link, all of those different atmospheric attenuation
conditions should be considered, to select the proper launch power
and proper relaying range ensure that the relay system margin of
gain is big enough to satisfy the requirement of availability of
transmission link
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Relaying
range of AirBridge |
The products among AirBridge series have different the recommended relaying
distance for each other.The recommended relay distance is not the
maximum distance that the relay link could be reached,it is the relay
distance in ordinary weather as some system margin of gain has been
included. Generally the maximum relay range can be reached to in
clear weather. Because the requirements for data rate and link availability
are different, the required system margins of gain are different.
Generally the higher the data rate of link and the link availability
are, the shorter the relay range is. And vice versa, the lower the
data rate and availability are, the longer the relay range is, such
as the relay link of Fast Ethernet.
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Data
rate and sensitivity of AirBridg |
AL-155M is designed for the data with the speed from 2Mbps to 156Mbps
among AirBridge series. While the data rate is 155Mbps, the typical
sensitivity of the receiver is -40dBm, and it is -47dBm while the
rate is 16.896Mbps. AL-1250S is designed for the data with the speed
of 1.25Gbps and it has the sensitivity of -35dBm.
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The
emitting power and system gain margin of AirBridge |
All of the AL-100E, AL-155M and AL-1250S among Air Bridge series have
two laser emitters of VCSEL which produce two laser beams passing
through two independent optical systems. The mean emitting power
of each laser emitter is 12mW (10.8dBm), the mean emitting power
of one set of equipment could reach 24mW (13.8dBm) and the maximum
emitting power could reach 48mW (16.8dBm). All of the equipments
among AirBridge series have the emitting power controllers with three
steps in order of that one set of equipment is suitable for the transmission
link with long haul and short haul in the mean time. The user can
select the proper the step according to the range of transmission
link to satisfy the requirements of laser safety standards.
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| Application
range (m) |
150-350 |
350-800 |
800-1600 |
1600-3000 |
| Laser
number |
1 |
2 |
1 |
2 |
1 |
2 |
1 |
2 |
| Emittinf
power (mWAVG) |
1.15 |
2.3 |
5 |
10 |
12 |
24 |
12 |
24 |
| Horizontal
/ Vertical beam angle (mrad) |
2 |
2 |
2 |
2 |
| Optic & Coupler
attenuation (dBm) |
3 |
3 |
3 |
3 |
| Geometry
attenuation(dBm) |
9.54-16.9 |
16.9-24.08 |
24.08-30.1 |
30.1-35.56 |
| Sensitivity
(@155Mbps)dBm |
-40 |
-40 |
-40 |
-40 |
| System
Gain (dBm) |
40.6 |
43.6 |
47 |
50 |
50.79 |
53.79 |
50.79 |
53.79 |
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Laser
safety standards |
IEC
60825-1(Part 1) Equipment classification, requirements
and user's guide .
IEC 60825 -12 (Part 12) Safety of free space optical communication system
used for transmission of information |
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