This paper analyzes perturbations caused by nonlinear intrachannel effects and shows how to cancel them by symmetric configuration of transmission and dispersion-compensating fiber. From an analytical study of amplitude and timing jitter conditions are derived to reduce them effectively. Simulations are performed using different schemes of dispersion compensation and improvement and limits of regenerative symmetric links are also discussed. Finally, the paper presents a simple fiber-based configuration to reduce timing jitter in particular. The quality of existing transmission systems is improved.