Cost effective OLT designed from optical frequency comb generator based EML for1.22 Tbps wavelength division multiplexed passive optical network

In this article we have proposed a novel cost effective optical frequency comb (OFC) generator by using pair of Mach zehnder modulators (MZMs) in cascaded configuration with a single external modulated laser (EML) source, where the two MZMs were driven by low powered RF source with 30 GHz frequency by incorporating no extra electrical components. More than 60 flattened carriers were generated in cascade mode with such simplified model having high tone to noise ratio (TNR) of over 40 dB, 0.5 dB amplitude difference in most of the carriers, 30 GHz frequency spacing, and 37 dB side mode suppression ratio, all the frequency tones lies in optical C-band. The EML's power was kept at 10 dBm while the extinction ratios (ER) were studied from 0 to 20 dB where we found that the TNR and amplitude difference of the OFC were directly connected with the ER value of EML. OFC was deployed at optical line terminal (OLT) side that decreases the costs, size, and power usage for wavelength division multiplexed passive optical network (WDM-PON). Furthermore, we utilized new setup at ONU side of WDM-PON which replaces the conventional IM-OOK with DD-MZM-NRZ. This way power consumption was reduced at ONU side by 3.5 dBm, and the receivers’ sensitivity was also improved at OLT side for the uplink transmission including the system performance. Colorless ONUs were achieved by utilizing the downlink signal's power. In downlink transmission, OFC was deployed at OLT side of WDM-PON network where each wavelength supported 20 Gbps data based QPSK, this system is capable of 20 * 61 Gbps data transmission from 25 km to 50 km fiber span. This model could support 1.22 Tbps downlink and 610 Gbps uplink transmission effectively. The system's performances were investigated in terms of bit error rate, power penalties, and eye patterns. The average power penalties were founded as 2.5 dBm, and 3 dBm across 25 km fiber in the downlink-uplink transmission respectively, similarly the power penalties across 50 km fiber span in downlink-uplink transmission were 4.5 dBm and 5 dBm respectively.