SOURCEFORGE » RALF » 2015 Evaluation and test of an optical / L-band tranceiver

h1. 5. Conclusions

h2. 5.1 Simplified optical link model for transmission of a carrier

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

p=. !{width:700px}SFDR.png!

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 :

# 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.

h2. 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.