Model 2809
CATV
Linx
®
LDS CATV Receiver
Product Technical Bulletin
Revision 2.0
3
Figure 1.2 shows an expanded view of the frequency response of a typical
2806T/2809R link.
Figure 1.2 Expanded Frequency Response
3) Figure 1.3 show the CNR versus received optical input power and number of
channels. The horizontal axis is the amount of optical light that reaches the
receiver. (It is not the loss between the transmitter and receiver.) The vertical
axis shows the CNR.
Figure 1.3 CNR vs. Receiver Optical Input at 77 Channels (2806T with 2809R)
The link CNR is usually specified for a received optical power of -3 dBm or
more. Thus, a 2806T-SCSP optical transmitter, with an optical output of +4.5
dBm, will provide optimal performance with up to 7.5 dB of optical loss at full
channel loading. If lower channel loading is used, then the link can operate at
higher optical losses and still provide exceptional CNR.
Typical transmitter output is +4.5 dBm, so a received optical power of -3.5
dBm corresponds to an optical loss of 8 dB. Five curves are plotted; the top
curve is the typical result when only 5 channels are transmitted through the
link. It can be seen that very high CNR results and in fact the output is quite
usable with receiver optical inputs as low as -12 dBm, corresponding to 16 dB
of optical loss! As the channel loading gets higher, the maximum achievable
CNR drops.
50
100
150
200
250
300
350
400
450
500
550
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Receiver Optical Input (dBm)
Carrier
-to-Noise Ratio (dB)
5 Ch.
10 Ch.
24 Ch.
40 Ch.
77 Ch.
36
38
40
42
44
46
48
50
52
54
56
58
60
62
64
-12 -11 -10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
