Analytical Analysis of In-Band Crosstalk, Out-of-Band Crosstalk and GVD-Based Power Penalties in DWDM and TDM/DWDM-PONS

Abstract

In addition to the ever-increasing demand for broader bandwidth per user, which results from the continuous development of new bandwidth-hungry services and applications, the consequent upgrade from the currently deployed Time-Division Multiplexing Passive Optical Networks (TDM-PONs) to Next-Generation Optical Access Networks (NG-OANs) has become inevitable. Different architectures for creating a NG-OAN have been proposed in the literature. Among those architectures, the DWDM and TDM/DWDM-Based OANs are very promising candidates. They were mainly proposed to exploit the large wavelength counts available in the fibre (its virtual unlimited bandwidth) to achieve a significant increase in the system capacity. Moreover, they allow coexistence in an open access environment among different network operators. In this study, we first analyze the impact of in-band crosstalk, out-of-band crosstalk to evaluate the performance of the Arrayed Waveguide Grating (AWG). The reason to focus on the AWG is due to this optical device is used almost in all DWDM and TDM/WDM-PONs. We then turn our attention to analyze the impact of group velocity dispersion GVD to estimate the maximum allowable bit rate for optical transmission without the need for using a Dispersion Management Technique (DMT) and/or a Forward Error Correction Technique (FECT). The analysis was performed using Matlab software (The Math works, Inc., Natick, MA, USA) and confirms that the in-band crosstalk has a stronger effect than the out-of-band crosstalk because its noise floor is reached at a lower crosstalk noise and with fewer crosstalk components. The in-band crosstalk noise should be kept below -37 dB and -34 dB to maintain a power penalty of less than 1 dB if 15 and 7 in-band crosstalk components are considered, respectively. The out-of-band crosstalk noise should be kept below -20.3 dB and -17.18 dB to maintain a power penalty of less than 1 dB if 240 and 56 out-of-band crosstalk components are considered, respectively. It was observed that the GVD noise floor is reached at a shorter fiber length as the bit rate increases and it was confirmed that a significant improvement in which the GVD noise floor is reached at longer fiber can be achieved if an externally modulated, small spectral-width source is used when a bit rate of 622 Mbps, 1 Gps, or 2.5 Gbps is used. However, a dispersion management technique becomes necessary if the bit rate increases to 10 Gbps or more.