## 2 Results and Discussion
### Physical Properties and Fabrication Process of PFGI-POF
#### 2.1.1 Material Properties and Fabrication Process
This fabrication process is applied to fabricate the fiber preform at Asahi Glass Company (AGC): the obtained fiber is known under the Lucina acronym. Owing to the density difference between the two monomers, the centrifuging method [11] could be used to produce POF preforms. More specifically, a gravitational field is used in the process to generate and to fix compositional gradients in homogeneous mixtures of monomers, mixtures of  
Figure 4: Interfacial gel polymerization method used by [PERSON] _et al._[8-10]. Figure 3: Spectral attenuation of the graded index POF as compared to glass fiber [7]. polymers and polymer-monomer mixtures according to the molecular weight. In this manufacturing method, the rotation speed is kept below 25,000 rotations per min (rpm). The PFGI-POF is then obtained by using both the fabricated preform and classical means able to draw the fiber. The Chromis fiberoptics company lead by [PERSON] has performed the fabrication of POF based on the CYTOP(r) material with the use of the co-extrusion process (no preform fabrication has to be done). Two extruders, containing respectively the CYTOP(r) material for the cladding and the CYTOP(r) fluoropolymer including dopant for the fiber core, are used to fill a heated tube (Figure 5). Owing to the thermal polymerization, the dopant diffuses from the center to the outer edge in order to form the graded index profile [12]. The fiber attenuation shape depends strongly on the manufacturing process as some impurities could be added inside the core material leading to extrinsic losses. The optical backscattering reported in Figure 6 clearly shows that the co-extrusion process leads to high fiber attenuation contrary to the classical process (preform and fiber draw tower). Defects are materialized by the smaller backscattering peaks that appear all along the propagation. The PFGI-POF issued by Chromis Fiberoptics (in particular the 50  sample) exhibit some intensity peaks unlike the ones from the Asahi Glass (Lucina). Figure 5: Manufacturing processes used by Chromis Fiberoptics (co-extrusion process [12]). Figure 6: Optical backscattering measurement of the PFGI-POF. The fiber length inside a building is generally limited between 50 m and 300 m [13] and the PFGI-POF seems to have suitable properties to achieve the link budget requirement (bandwidth and attenuation) for high data rate baseband transmission and RoF systems. In fact, the relative low attenuation (\(\sim\)30 dB/km) in the expected spectral range (850 nm-1,300 nm), contrary to the PMMA based PFGI-POF (more than 100 dB/km in the visible range), as well as their bandwidth, allows using them to design high speed and low losses small office/home office networks. Currently, two manufacturers have been identified as supplying perfluorinated graded index polymer optical fibers. As mentioned previously, Asahi Glass Company commercialized the Lucina fiber in early 2000 (technological transfer of the interfacial gel polymerization method from [PERSON], _et al._). The high purity of the fluoropolymer developed by Asahi Glass Company leads to very promising products with small losses and high bandwidth performance (Table 1). This fiber has a 120 \(\upmu\)m core diameter and a numerical aperture close to 0.185. Since April 2009, AGC Company has proposed Lucina-X PFGI-POF that includes a double cladding in order to decrease the sensitivity of such fibers to bending effects. Since 2005, Chromis Fiberoptics used the co-extrusion process to fabricate the PFGI-POF. This process is well adapted to mass production as no preform is needed. The core diameter of the Chromis Fiber Optics PFGI-POF varies from 50 \(\upmu\)m up to 120 \(\upmu\)m (Table 1). Actually, only the 120 \(\upmu\)m core diameter based PFGI-POF Lucina and GigaPOF-120 SR have been standardized under the A4G category. A PFGI-POF based on a 62.5 \(\upmu\)m core diameter is standardized under the A4h acronym but this fiber exhibits a 245 \(\upmu\)m cladding diameter value contrary to the GigaPOF-62 SR (500 \(\upmu\)m).