## 2 Materials and Methods
### Experimental Methodology  
The experimental protocol was the following: We started with the longest fiber length whose input end was cleaved, stripped and inserted into a ST connector. The connector end was polished using two pieces of sandpaper with different roughness levels, and connected to the laser mount, where it remained invariable throughout the duration of the experiment to ensure that all fiber lengths were tested under the same launching conditions. Then, we applied the same process to the output fiber end and connected it to the different devices to measure S\({}_{21}\) parameter, optical power, FFP and BER. For each fiber length, the output end was cleaved, stripped and polished twice. The optical power and S\({}_{21}\) parameter were measured at least five times, always changing the receiver or power-meter connection. Fifteen FFP images were registered to obtain an average. The BER was measured as a function of data rate for a basic OOK transmission using a pseudorandom binary sequence (PRBS) pattern length of 2\({}^{23}\)-1. When the whole set of measurements was completed, a fiber segment was cut from its output end to get a shorter fiber. The output end of the remaining fiber was prepared, and a complete set of measurements was repeated for that fiber length. This protocol was applied to the three fibers considered, but starting from different fiber lengths depending on their different characteristics. This starting length was 130 m for MH, 150 m for GH, and 100 m for BH. All the analyzed fibers were reeled over a 20-cm spool. For the GH fiber, we used the advantage of the GH duplex reeI to run this experimental protocol simultaneously for red and green light. One of the two fibers of the duplex was connected to the LD520 and the other to a red laser diode, LD650P007 (LD650, 7 mW at 650 nm), that was placed in another LDM9T mount driven by a LDC200 controller set to 35 mA at 25 \({}^{\circ}\)C. In this duplex experiment, the input ends of both fibers were fixed, and the output ends were connected sequentially to the different devices to obtain the complete set of measurements for both wavelengths at a given fiber length. The input ends of the two fibers of the duplex were split over a segment of 10 cm to permit the connection of each end in a different laser mount. At the output end, the split segment of the duplex fibers was only 3 cm, because the fibers were alternatively connected to the various devices. We also designed a control experiment to determine if the fibers have different frequency responses depending on the wavelength. In this experiment, we fixed the launching conditions using a 15 cm ST-connectorized fiber pigtail to inter-connect one of the two LD sources to the tested fiber. The purpose of this launching technique was to provide an overfilled launch where the source optical power was coupled up to the fiber's high-order modes or angles [6]. Conversely, direct injection, as achieved in the previously described cut-back method, is usually underfilled; i.e., optical power is concentrated only at low angles, and in addition, is prone to large variability [20]. The wider angular distribution provided by the pigtail is very stable and more independent of the source's spatial characteristics. Thus, we measured the S\({}_{21}\) transmission parameter with one end of the pigtail connected to one of the two LD sources, and with the other connected to one of the fibers. The other end of the tested fiber was connected to the receiver and remained connected when the pigtail input end was changed from the LD520 to the LD650. Thus, the detection conditions were exactly the same for the two wavelengths, and the variability of the input conditions was minimized by the indirect launch. This protocol was applied to the three fiber types using individual segments of three different lengths, 15, 20 and 50 m, and was repeated several times using the SPD receiver.