5.1 Simplified optical link model for transmission of a carrier¶
The model is based on the Spurious Free Dynamic Range graph :
Thanks to this graph, it is possible for a given RF input power to determine :
Figure 2. RF frequency respone (for several RF input powers).
- RF output power and related gain ;
- Output noise ;
- 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|
|LNB remote supply||Yes, supplied through coaxial cable||No, supply close to antenna for OTX required|
|Current Consumption [mA]||0||700 mA / 12 V|
|Bidirectional link||Yes||Yes, but with additional hardware|
For a distance of 30 m, optical link is not justified : performances and cost are not competitive with coaxial cable.