Elements and technical features » History » Version 21

HAENNIG, Gerald, 12/15/2015 09:23 AM

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h1. 2.1 Elements 
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h2. 2.1.1 Optical link : Radio Frequency Over Fiber
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Figure 1. Optical Link (source Miteq).
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On optical link consists of :
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* an optical transmitter ; it modulates input Radio Frequency (RF) signal onto the optical wavelength intensity. 
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Optical intensity is varied either directly by varying Laser Diode current or indirectly through a Mach-Zehnder Modulator modulating a constant laser source.
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* fiber optic : in general, monomode fiber optic is used to avoid dispersion especially for long link. Morever, wavelengths around 1300 nm are used as dispersion is minimum in this region.
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* an optical receiver : it is based on a photodectector. It detects RF modulation on the optical wavelength and outputs the RF signal.
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Such an optical link is referred to as Radio Over Fiber (RoF), as well.
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The main parameters for an optical link are gain, bandwidth, Noise Figure (NF) and Spurious Free Dynamic Range (SFDR).   
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MITEQ, Fiber optic products : https://www.miteq.com/docs/MITEQ_FiberOptic_c40.pdf
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Main applications are 
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* antenna remoting : 
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for satellite broadcast TV, signal is received on the antenna on the roof but actually demodulated in the tuner in the living room.
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for teleports, Radio-frequency signal transport through optical fibres from Antenna to the main building (containing Modulator/Demodulator, Network Equipments).
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* signal distribution : 
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for phased array radar application, it could be used to distribute the Local Oscillator to the different array elements.
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for cable television (CATV : Community Antenna TeleVision) : to distribute the TV channels to the homes.
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h2. 2.1.2 Antenna remoting : Intermediate Frequency (IF) transport from Antenna Low Noise Block to Tuner for Satellite Broadcast TV
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Earth stations are based on an indoor/outdoor unit architecture. In our system we will count on: 
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* Outdoor: L-band reception antenna, the coaxial cable relying the antenna and the modulator transmitter (allows to convert from L-band to optic frequencies) and the 30m of Monomode FO. 
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* Indoor: consists of the receiver L-band/optic demodulator and the coaxial cable to rely the demodulator with the TV. 
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