Design Examples; Standard Definition 2 Km Link - evertz 2405EO-HD Instruction Manual

2400 Series Fiber Converter Manual
2405EO-HD SMPTE292M Re-Clocking Electrical to Fiber Converter
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. 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.
Therefore, 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.
added jitter may become significant on cable lengths approaching 54 Km at 1550 nm.
2405EO-HD-14
EO13
2 km x 0.4 = 0.8 dB
-7.5 dBm
-2.0 dB
-0.8 dB
-2.0 dB
–12.3 dBm
This is above the published specification of -30 dBm, therefore
Revision 1.3
7705OE