**6.5 7.8 Gb/s transmission over 50 m SI-POF**

The WDM channels based on 405 nm (DL-7146-101S), 450, 515, and 639 nm laser diodes were employed in this transmission experiment. To maximize the modulating signal amplitude and thereby improve the SNR of the received signal, the optical output power of each laser diode was adjusted to its maximal possible value. For 405, 450, and 515 nm devices, the operating point was set to comply with the upper limit of the receiver's dynamic range. The 639 nm device was driven with the maximum recommended forward current. The respective used bias currents were 70, 40, 61, and 43 mA. The optical powers coupled into the SI-POF link and the received optical powers measured after the demultiplexer are given in **Table 7**. All diodes were driven in their linear lasing region. The 1 Vpp output amplitude of the AWG was sufficient to modulate 450, 515, and 639 nm laser diodes with the modulation index of approx. 0.9. The signal in 405 nm channel was additionally amplified to achieve the same modulation index. For the amplification, a MERA-556+ wideband amplifier (20.5 dB gain at 0.1 GHz) was used in combination with 10 dB attenuator to avoid amplifier nonlinearities (18 dBm output power at 1 dB compression point at 0.1 GHz).

The maximum transmission rates achieved in the individual channels were 1.7 Gb/s (405 nm channel), 1.9 Gb/s (450 nm channel), 2.2 Gb/s (515 nm channel), and 2 Gb/s (639 nm channel). Thereby, six FFE taps with the tap delay equal to one half of the corresponding bit period were used in each of the channels. The transmission parameters for the individual channels are listed in **Table 8**. The resulting eye diagrams are represented in **Figure 19**. A total of 7.8 Gb/s were transmitted over 50 m SI-POF at the BER < 10–5. After deduction of 3.2% redundant bits required for Reed-Solomon (255,247) FEC, a net bit rate of 7.56 Gb/s was obtained. Compared to the record capacity of a single-channel system over the same fiber length used by Vinogradov et al. [10], an improvement of 1.67 Gb/s was achieved.


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

**Table 8.**

*Transmission parameters for 50 m SI-POF link at an aggregate bit rate of 7.8 Gb/s.*
