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6.2.
DESIGN EXAMPLES
6.2.1. Standard Definition 2 km Link
Using the 2405EO3F as the transmitter.
Launch Power =
Connector Loss = 2 x 1
Fiber Loss = 2 x 0.4
Safety Margin =
Power at receiver
The 2405OE has a listed sensitivity of –30 dBm, which is lower than –12.3 dBm so we can implement the
system with no problems, at least with respect to power availability.
Next we need to check the jitter penalty. The system jitter-penalty = 2.5 ps/ x 2 km x 5 nm = 25 ps. So by
going through 2km of fiber, we add 25ps of jitter under the worst conditions (under the best conditions we
would add 2ps total). The standard definition video bit period is 3.7 ns; so if the maximum jitter penalty is
20% or 740 ps., then the added jitter for this system is insignificant.
When would jitter-penalty be a problem? For 1310 nm wavelengths, the cable length where the jitter
penalty becomes significant is calculated as: 740 ps divided by 2.5 ps/km/nm divided by 5 nm = 60 Km
(worst case), or 600 Km (normal condition). At 60 Km cable length the cable loss is 60 x 0.4 = 24 dB. So
the power into the receiver would be: – 6 dBm – 24 dB = – 30 dBm. This is equal to the published
specification of -30 dBm but leaves no margin for connector or other losses. The jitter penalty at 1550 nm
for standard definition video is calculated as: 740 divided by 17 divided by 0.8 = 54 Km (worst case). At
54 Km cable length the cable loss is 54 x 0.3 = 16.2 dB. So the power into the receiver would be:
- 0 dBm – 16.2 dB = - 16.2 dBm. This is above the published specification of -30 dBm, so added jitter may
become significant on cable lengths approaching 54 Km at 1550 nm.
6.2.2. 20 Km Link With 2 Standard Definition Signals On 1 Fiber
EO13 TX1: -7.5 dBm
EO15 TX2 : 0 dBm
For Tx1 < Rx1:
Launch Power =
Connector Loss = 4 x 1
Fiber Loss = 20 x 0.4
Safety Margin =
2405OE-HD SMPTE 292M Re-Clocking Fiber to Electrical Converter
EO13
2 km x 0.4 = 0.8 dB
-7.5 dBm
-2.0 dB
-0.8 dB
-2.0 dB
–12.3 dBm
7705 WDM
1310nm
20 km x 0.4 = 5 dB
1550nm
loss - 4 dB
-7.5 dBm
-4.0 dB
-8.0 dB
-2.0 dB
Revision 1.2
2400 Series Fiber Converter Manual
7705OE
7705 WDM
1310nm
1550nm
loss - 4 dB
OE Rx1: 1310 nm
OE Rx2: 1550 nm
2405OE-HD-11
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