Dispersion equalization of a 10 Gb/s repeatered transmission system using dispersion compensating fibers

We have investigated theoretically and experimentally the transmission performance of a 10 Gb/s repeatered transmission system using dispersion compensating fibers (DCFs), The system configuration that we considered is a 360 km standard (1300 nm zero-dispersion) fiber transmission system with an optical repeater including DCF´s located every 120 km (or every 2100 ps/nm dispersion). The transmitter was a DFB-laser externally modulated by a zero-chirp LiNbO₃ modulator with NRZ (non-return to zero), 2²³-1 PRBS data. The system performance is evaluated in terms of electrical eye margin in the receiver/regenerator. We present a complete description of the system performance including the nonlinear SPM (self-phase modulation) effect in both standard fibers and DCFs. The results of this investigation clearly demonstrate that the use of DCF´s is an extremely effective method to overcome the chromatic dispersion in high-speed transmission systems. The main results of this study are (1) the new “eye position method” which presents the eye margin degradation from both “1” and “0” levels as a function of dispersion values describes the system performance more effectively than the conventional “EOP (eye opening penalty) method”, (2) a rule of thumb is that the total dispersion must be slightly undercompensated to include the SPM effect, (3) a very wide range of dispersion compensation values offers acceptable system performance, and (4) the “equal modular compensation” which is desirable from a practical point of view provides sufficiently large eye margin (33.3% for 10^-15 BER after 360 km) although the “customized modular compensation” where the dispersion compensation is tailored to achieve the maximum eye margin without considering the performance at the intermediate repeater locations provides the largest eye margin (48.5% for 10^-15 BER)