Olson Technology OTPN-800CH - Manual (Page 8)

System Setup & Troubleshooting
Fiber Loss at 1310nm is 0.330dB/km, and 1550 is 0.188dB/km. Using these values, if
the fiber run is 6km (3.73 miles), then a 2dBm transmitter is required for the distance. If
the forward band is being split, then the additional loss must be accounted for. A fiber
splitter generally splits the signal equally between each output. If the forward path is to
be split 4 ways, then a +8dBm transmitter is required to cover the 6 km. If the links
coming out of the splitter are different lengths, then be sure to have enough transmitting
power to reach the receiver with the longest link. Those with shorter links can be
attenuated to lower the signal to a level the receiver can use. To be sure the receiver is in
the correct range, measure the Receive T.P. using a DVM. The best operating range for
most OT forward receivers is 0.5V to 0.9V (approximately -3dBm to -0.5dBm). Some
have operating ranges down to -8dBm.
If the fiber run is less than a few km, then the optical signal must be lowered before the
system can operate correctly. Failure to do so may cause an overloaded or distorted
picture. The easiest way to lower the signal is to use an optical attenuator. OT makes an
easy to use attenuator called the OTOA-1000. This provides for an easy way of lowering
the optical signal by wrapping the fiber tightly into the slot inside of it. Every fiber is
different, some may require more wraps then others. Generally one wrap around the
largest of the three post will lower the optical signal by approximated 1.75dB. The two
smaller post attenuate the signal more. If the received power is too low, but the correct
power transmitter is being used, please consult the following:
1: Be sure all fiber connectors are clean using an approved fiber cleaner.
2: Be sure the fiber connectors are all of the same type. All OT units ship with either
SC/APC or FC/APC style connectors. These will be green in color. You can NOT mix
green and blue connectors, as the end terminations are different. This can also result in
low signal or snowy picture.
3: Broadband RF transmitters such as those made by OT require the use of SM fiber.
MM will not work.Attempting to use MM fiber will result in low signal or snowy picture.
DC DC