446
COMMUNITY ANTENNA TELEVISION (CABLE TELEVISION)
-2 -4 -6 -8 -10 -12 -14 -16 -18 -20 -22 -24 -26 -28 -30
dBm
8-Channel FM/FDM system
S/N Ratio versus receiver sensitivity
CCIR w
eighted S/N r
atio
Worst
channel
limit
Best channel
limit
Average of
8 channels
S/N
= 67 dB
Use optical
attenuator
in this
region
69
68
67
66
65
64
63
62
61
60
59
58
57
Figure 17.13
Link performance of an FM system. (Courtesy of ADC Video Systems.).
Table 17.1
Link Budgets for AM Fiber Links
Distance
(mi)
Distance
(km)
Fiber
Loss/km
Total
Fiber
Loss
Splice
Loss/2 km
Total
Splice
Loss
Total
Path
Loss
Link
Budget
Link
Margin
Mileage, Losses, and Margins--1310 nm
12.40
19.96
0.5 dB
9.98
0.1 dB
1.00
10.98
13.00
2.02
15.15
24.38
0.4 dB
9.75
0.1 dB
1.22
10.97
13.00
2.03
17.00
27.36
0.35 dB
9.58
0.1 dB
1.37
10.94
13.00
2.06
Mileage, Losses, and Margins--1550 nm
22.75
36.61
0.25 dB
9.15
0.1 dB
1.83
10.98
13.00
2.02
Calculation of Video S/N for FM System. Given the CNR for a particular FM system,
the S/N of a TV video channel may be calculated as follows:
SNRw
= K + CNR + 10 log
B
IF
B
F
+ 20 log
1
.6 F
B
F
,
(17.13)
where
K = a constant (23.7 dB) made of weighting network, deemphasis, and
rms to p-p conversion factors,
CNR
= carrier-to-noise ratio in the IF bandwidth,
B
IF
= IF bandwidth,
B
F
= baseband filter bandwidth, and
F = sync tip-to-peak white (STPW) deviation.
Summary :
Table 17.1 Link Budgets for AM Fiber Links Distance (mi) Distance (km) Fiber Loss/km Total Fiber Loss Splice Loss/2 km Total Splice Loss Total Path Loss Link Budget Link Margin Mileage, Losses, and Margins--1310 nm 12.40 19.96 0.5 dB 9.98 0.1 dB 1.00 10.98 13.00 2.02 15.15 24.38 0.4 dB 9.75 0.1 dB 1.22 10.97 13.00 2.03 17.00 27.36 0.35 dB 9.58 0.1 dB 1.37 10.94 13.00 2.06 Mileage, Losses, and Margins--1550 nm 22.75 36.61 0.25 dB 9.15 0.1 dB 1.83 10.98 13.00 2.02 Calculation of Video S/N for FM System.
Tags :
system,link,1300,fiber,total,channel,ideo,loss,bandwidth,cnr,splice,teleision,limit