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

h1. 4. Results

This section explains how the Outdoor system has been installed and the results obtained measuring a real TV signal from a Satellite. 

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Optical system (transmitter + fiber + receiver)

h2. 4.1 Preparation

The optical transmitter has been put in an hermetic box.

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Hermetic box installed outdoors

Its interface consists of :

* The power supply plug to be connected to the mains ;

* The optical fiber harness (2 fibers) : only the red fiber is actually connected to optical transmitter ; the black fiber is not used, it will enable to have a b.

* The type F coaxial cable to connect the Antenna Low Noise Block, LNB, to optical transmitter.

Optical transmitter is set to :

* To supply 18 V to LNB, which selects Horizontal polarization.

* To provide 0 kHz tone to LNB, which set its Local Oscillator to 9.75 GHz to transpose lower Ku Band from  10.7 to 11.7 GHz into IF Band.

* This hermetic box has been mounted on Antenna mast. This Antenna is pointing to Astra 1KR/1L/1M/1N co-localized satellites on 19.2° East.

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Hermetic box installed on Antenna Mast

h2. 4.2 Trials

h3. 4.2.1 Inter Frequency Spectrum with Optical Link

RF output from Optical receiver has been analyzed with Rohde & Schwartz FSV spectrum analyzer :

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_IF Band, 1 Channel (with Optical Link)_

It is possible to distinguish several channels within the Inter Frequency, IF, band. There is a zoom on left side. The 3 dB channel bandwdith is 22 MHz.

The power is about -32 dBm for the channel centered around 1141 MHz.

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_TV channel at 1141 MHz_

h3. 4.2.2 Link Quality with Optical link

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Measurement setup based on TV, Tuner, IPRICOT SCB router with Optical Receiver (On screen : Einsfestival program on 10744 MHz Horizontal Polarization)

First, optical link performance enables to have a good TV quality (for example, Einsfestival Plus on 10744H).

Channel power and 3 dB Channel bandwidth have been checked with Spectrum Analyzer.

More deeply, physical link quality has been assessed with the information provided by IPRICOT SCB router :

* IPRICOT confirms that input signal is a QPSK modulation with Forward Error Correction Rate of 5/6 (RX_SIG & VITSYNC set to green). Moreover, IPRICOT is able to get the Frame Synchronization (FSYNC set to green) ;

* Eb/No is reported by IPRICOT.

This data has been compared with data from website like [www.lingsat.com] :

|/2. Ku Channel [MHz]|/2. IF Channel [MHz]|_. TV|\2=. www.lingsat.com |\2=. Spectrum Analyzer|\2=. IPRICOT|

|=. Channel|=. Physical Protocol|=. EIRP[dBW]|=. 3dB CH BW [MHz]|=. CH Power [dBm] |=. Physical Protocol|=. Eb/No[dB]|

|=. 10744H |=. 994|=. Eins Plus|=. DVB-S QPSK 22 Msps 5/6|=. |=. About 22|=. -31.44 |=. DVB-S QPSK 22 Msps 5/6|=. 7.7|

|=.11244H |=. 1494|=. Schau TV |=. DVB-S QPSK 22 Msps 5/6|=. |=. About 22|=. -32.31 |=. DVB-S QPSK 22 Msps 5/6|=. 7.9|

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Physical link parameter at 10744 MHz

h3. 4.2.3 Link Quality with Coaxial Cable

Optical link have been replaced by coaxial cable. Similar measurements have been carried out.

A splitter is used to measure the spectrum : this loss has to be taken into account.

Antenna coaxial cable was directly connected to IPRICOT SCB router.

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Spectrum at 944 MHz (related to 10744 MHz H)

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Physical link parameter at 10744 MHz

h3. 4.2. Result analysis : comparison coaxial cable vs optical link

|/2. Ku Channel [MHz]|/2. IF Channel [MHz] |\2=. Optical link |\2=. Coaxial Cable |

|=. CH Power [dBm] |=. Eb/No[dB]|=. CH Power [dBm] |=. Eb/No[dB]|

|=. 10744H |=. 994 |=. -31.44 |=. 7.7|=. -32.84 |=. 7.4|

|=. 11244H |=. 1494|=. -32.31 |=. 7.9|=. -36.67 |=. 8.0|

Performances sounds to be quite similar between coaxial cable and optical link.