The upper transmission range of the wavelength division multiplexing passive optical network (WDM-PON) can be restricted by chromatic dispersion (CD). This paper contains the investigation of till 16-channel WDM-PON system with efficient CD pre-compensation and post-compensation methods. It is shown that CD offset has a marginal role for guaranteed optical link downstream performance and maximum length of high-speed WDM-PON system. The results show that employment of extra 7 km long dispersion compensating fiber (DCF) placed in central office (pre-compensation configuration) enhances the WDM-PON network link length by 19.3% (from 57 km up to 68 km), but if extra 2 km long DCF fiber is used in remote terminal (post-compensation configuration) link length can be extended up to 5.3% (from 57 km to 60 km). It was found that usage of fiber Bragg grating (FBG) in central office (pre-compensation configuration) improves network reach up to 26.3% (from 57 km up to 72 km), but using this FBG for CD post-compensation in remote terminal network reach can be improved by 15.8% or 9 km in length - from 57 km to 66 km. Basis on the results authors recommend to use FBG as the best solution for CD compensation in pre-compensation configuration (before SMF line) in future high speed long-reach DWDM-PON systems.

Comparison of Chromatic Dispersion Compensation Techniques for WDM-PON Solution

The authors have investigated the impact of self-phase modulation (SPM) induced distortions to optical signal transmission over proposed configuration of spectrally efficient wavelength division multiplexed (WDM) fiber-optic transmission system (FOTS). In chosen model of ultra-dense mixed-WDM system optical signals are transmitted with two different per channel bitrates (i.e., 10 and 40 Gbit/s) and three different optical signal modulation formats are used for the encoding of transmitted data (i.e., non-return to zero encoded on-off keying or NRZ-OOK, orthogonal polarization shift keying or 2-POLSK and NRZ encoded differential phase shift keying or NRZ-DPSK). In addition, “non ITU-T” defined minimum and equal frequency intervals are used for the channels separation. This research revealed that 2-POLSK modulated signals are more susceptible to the impact of SPM in such ultra-dense mixed transmission mode than e.g., NRZ-DPSK signals.

Evaluation of SPM-Induced Optical Signal Distortions in Ultra-Dense Mixed-WDM System

In this paper, the effect of nonlinearity has been investigated with different techniques such as non-return-to-zero (NRZ), return-to-zero (RZ), duo-binary return-to-zero (DRZ), and modified duo-binary return-to-zero (MDRZ) modulations. We have explored the fiber nonlinearities by taking dispersion of single-mode optical fiber at 2.5 Gbps communication system with various transmission lengths; i.e., 72–132 km is evaluated with respect to the nonlinearity in fibers. The evaluation is done in terms of Q factor and BER with the 0 dBm input launched power. Along with this pre-compensation, post-compensation and symmetrical compensation techniques are also applied, and it is observed that the Q factor in symmetrical compensation is higher in comparison to the pre-compensation and post-compensation techniques. Therefore, it is examined that nonlinearity effects are less effective in symmetrical compensation instead of pre-compensation and post-compensation.

Rukhsana Kouser

Papers

Analysis and Reduction of Fiber Non-linearity in Optical Communication System