User's Manual
Powerwave Fiber Optics
VM100 56/EN – User’s Manual Rev. P1A9-Draft 2004-11 4 - 5
6. Optical transmission
In the example shown in Figure 4-2, the optical downlink transmission (between the
optical transmitter and the optical receiver) is built-up with two optical connectors and
one single-mode fiber.
The optical connectors are of DIN/APC type. The coupling loss (gap and misalignment
losses) for this connector type is approximately 0.5dB.
The single-mode fiber loss is approximately 0.35dB/km for 1310nm and 0.20dB/km for
1550nm.
The maximum fiber attenuation should not exceed 15dB.
Example:
At a distance of three kilometers, the optical transmission loss for a 1310nm signal is
approximately 2dB (0.5dB + 3x0.35dB + 0.5dB), and for a 1550nm signal
approximately 1.6dB (0.5dB + 3x0.20dB + 0.5dB).
The optical transmission loss will increase for devices used to split the signal path to
more than one receiver or to use the same fiber for both transmission directions. This is
further described in the Simplex Transmission section on page 4-12, and in the Duplex
Transmission section on page 4-13.
Note that all optical losses, except for FOT/FOT and FON/FON conversion losses, are
to be multiplied by two when converting to electrical RF losses.
The reason why the optical loss has to be multiplied by two (in dB) is that the light
detector in the optical receiver has a square shaped input area and thus extracts the
square root of the input power.
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