5. Conclusions¶

5.1 Simplified optical link model for transmission of a carrier¶

The model is based on the Spurious Free Dynamic Range graph :

Figure 2. RF frequency respone (for several RF input powers).

Thanks to this graph, it is possible for a given RF input power to determine :

1. RF output power and related gain ;
2. Output noise ;
3. 3rd order intermodulation products.

It is possible to calculate Carrier to Noise, Carrier to Intermodulation and Carrier to Noise & Intermodulation ratio.

5.2 Link comparison : Optical link vs Coaxial Cable for 30 m link length (like in a home)¶

In the following table, there is a comparison between coaxial cable to optical link.

Parameter	Coaxial Cable	Optical Link
RF Gain @ 950 MHz [dB]	-3.6	+0.5
RF Gain @ 2150 MHz [dB]	-5.6	+3.0
Noise Figure @ 950 MHz [dB]	+3.6	+30
Noise Figure @ 2150 MHz	+5.6	+33
IIP3 [dBm]	+50	+10
SFDR [dB/Hz2/3]	+145	+102
LNB remote supply	Yes, supplied through coaxial cable	No, supply close to antenna for OTX required
Current Consumption [mA]	0	700 mA / 12 V
LNB telecommand	Yes	No
Bidirectional link	Yes	Yes, but with additional hardware
Cost	Low	High

For a distance of 30 m, optical link is not justified : performances and cost are not competitive with coaxial cable.