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How better the connection, how longer the
connection which can be checked. Calculating of the length
depends on the range of the optical meter (OTDR), the quality of
the connection and the number of components. This is further
explained below.
We take the following data/information for this
example:
- Single mode fibre has an attenuation of 0.5 dB/kilometre
(1.310/1.550 nm).
- Splices are 0.3 dB each.
- Interconnections are 0.75 db each.
- There is 1 splice for each kilometre.
- There is 1 interconnection by 5
kilometres.
- The total length is 20 kilometres.
- The range of the optical meter is -50
dBm.
The attenuation of the fibre = 10.0 dB
(0.5 dB x 20 kilometres).
The attenuation of the splices = 4.8 dB
(0.3 dB x 16 splices).
The attenuation of the interconnections =
2.25 dB (0.75 dB x 3 interconnections).
The total attenuation of the connection =
17.05 dB (10 dB + 4.8 dB + 2.25 dB).
With the use of an optical source
laser with a capacity of -10 dBm, the total attenuation of the
connection and the optical source is -27,05 dBm.
At the use of an optical source
laser high power with a capacity of 0 dBm is the total
attenuation of the connection and the optical source is -17,05
dBm.
As long as the total attenuation on the
side of the optical meter is lower than -27,05 dBm every optical
source will function. Most of optical the meters can measure to
-50 dBm, so in this case each optical source can be used.
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Calculationsheet working field situation
(ideal): |
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Device: |
Pieces/km: |
Pieces total: |
Attenuation dBm: |
Attenuation total dBm: |
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Optical Source (example): |
1 |
1 |
-10 |
-10 |
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Single mode Fiber length(1.310/1.550nm): |
20 |
20 |
-0,5 |
-10 |
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Splices: |
1/1km |
16 |
-0,3 |
-4,8 |
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Interconnection: |
1/5km |
3 |
-0,75 |
-2,25 |
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0 |
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Attenuation dBm total: |
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-27,05 |
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If “attenuation dBm total” > “attenuation
dBm reciever” than ok |
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Optical receiver: |
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-50 |
-50 |
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