**6.1 Experimental setup**

The data transmission setup is shown in **Figure 13**. It comprised an Agilent N4903A bit error rate tester (BERT), four butt-coupled edge-emitting laser diodes, multiplexing POF coupler, 10 m SI-POF link, interference-based POF demultiplexer, optical receivers, and Agilent 86100B sampling oscilloscope.

*Optoelectronic Key Elements for Polymeric Fiber Transmission Systems DOI: http://dx.doi.org/10.5772/intechopen.86423*

**Figure 13.**

*Experimental setup for the measurements employing NRZ modulation: LD, laser diode; MUX, multiplexer; DEMUX, demultiplexer; PD, photodiode; TIA, transimpedance amplifier.*

To provide precise temperature control, prevent possible damage from overheating, and extend the lifetime, the laser diodes were mounted in Thorlabs TCLDM temperature-controlled laser diode mounts. The temperature of an integrated temperature control (TEC) element of the mount was adjusted to +15°C. Only for OSRAM samples the cooling at +10°C was used to provide better stability of the optical output power. Both the temperature of the TEC element and the bias current were controlled over a Thorlabs ITC8022 module. Four of those modules were installed in a Thorlabs PRO8000 modular chassis for the simultaneous control of four operating diodes (see **Figure 15**). To maximize the coupling efficiency from the laser diode into the fiber, a butt-coupling unit based on an *xy*-translator (0.25 mm pitch of the adjustment screws) was utilized. The translator was mounted on the TCLDM9 mount over a 4-rod construction system, as shown in **Figure 15**. To combine the optical signals with different wavelengths onto the SI-POF link, a Comcore 4 × 1 fused POF coupler was used (see **Table 5**).
