## 2 Results and Discussion
### Radio over Fiber System with PFGI-POF  
The previous section of the paper has clearly demonstrated that the PFGI-POF is a suitable candidate for high speed baseband signal transmission up to 10 Gbps with fiber length close to 100 m. This length value is compatible with an in-building network. Before describing the RoF technology, the CATV over POF is introduced as the transmitted signal is of the same nature as those used in RoF transmission. The feasibility of transmitting analogue CATV signals over a combination of singlemode and POF links has been demonstrated [25]. Recently, some new POFs have been developed with better performances and at a lower cost. These products greatly enhance the POF LAN research and have been utilized to transmit digital baseband and radiofrequency modulated signals for in-door application. Nevertheless, none of the above architectures have been considered to transmit optical CATV signals all the way from the central office (CO) to the home and then to the consumer in-house devices.  
The RoF technology allows the transmission of the radiofrequency narrow band or ultra wide band signal (RF) from a central office to several picocell access points able to provide RF coverage in shadowed areas. Of the POF available on the market, only the perfluorinated CYTOP(r) based plastic fiber is used for the distribution of radio signals over optical multimode fiber (RoF), mainly owing to its relative low attenuation in the infrared domain (contrary to the PMMA based POF). In [26], the improvement of the indoor coverage of radiocellular signals such as GSM and UMTS has been realized with the Lucina fiber using a RoF topology based on the Intensity Modulation-Direct Detection (IMDD) technique. The Error Vector Magnitude (EVM)--which is the best figure of merit to analyze a radiofrequency signal--has been evaluated after the transmission over glass [27] and POF multimode fibers in order to exhibit the different behavior according to the radio signals propagation inside the fiber core (Figure 18).  
The results show that the Lucina fiber constitutes without any doubt a promising candidate in RoF system using commercially available components manufactured for glass fibers. Moreover, because of its higher core diameter, POF does not induce modal noise penalties as in glass multimode fiber links [28] and the alignment is also less critical, thus reducing the cost of the optical active and passive devices including the installation and maintenance costs of the connections. Its higher flexibility based on \"plastic\" material offers a great advantage compared to the silica fiber which is more brittle.  
Nevertheless, the higher core diameter of the fiber with respect to the active area of some high speed detectors causes an additional power penalty.  
[PERSON] _et al._[29,30] has demonstrated the potential of glass and plastic multimode fibers to transmit the Wimedia multiband orthogonal frequency division multiplexing ultra wide band (MB OFDM UWB) standard over more than 1 km and 200 m respectively for the glass and the plastic fibers. The data rate of the wireless tested ultra wide band signal is between 200 Mbps and 480 Mbps. The influence of the fibers properties (attenuation, bandwidth/length product, _etc._) on the link quality (Figure 19) has been exhibited and two different behaviors of the core material have been observed.  
Figure 19: In Phase/Quadrature (IQ) constellation diagrams ((QPSK Quadrature Phase Shift Keying) and Dual Carrier Modulation schemes) and evolution of the EVM as a function of the fiber length (GMMF: glass multimode fiber _vs._ PMMF: polymer multimode fiber) and the fiber attenuation.  
Figure 18: EVM variation as a function of fiber type and length for UMTS signal: (**a**) 100 m; and (**b**) 300 m.