Optical modulation formats for high-speed DWDM systems

Abstract

State-of-the-art of high-capacity optical modulation formats used in high-speed DWDM transmission systems are presented. Simulations of 320 km transmission of DWDM signal show that DQPSK modulation is superior to CS-RZ and duobinary phase modulation with respect to signal degradation due to Kerr nonlinearities.

Performance analysis of NRZ, RZ, CRZ and CSRZ data formats in 10 Gb/s optical soliton transmission link under the impact of chirp and TOD

“…One of the most important facts in the system, which affects the choices of all other system parameters, is the signal optical modulation format. In fact, signal optical spectral bandwidth, tolerance to chromatic dispersion, resistance to nonlinear effects, susceptibility to accumulated noise and other system performance measures are directly related to the optical modulation format [5][6][7]. For high-speed optical soliton communication, the data transmission reliability is degraded by the system impairments like GVD and fiber non-linearities.…”

Comparative investigations of DWDM transmission system with PMD for different orthogonally modulated signals at 80 Gb/s

“…The proposed modulation formats use hybridization of different schemes like optimized OP, carrier‐suppressed return‐to‐zero (CSRZ) signal, and DPSK because of their special characteristics such as DPSK format has increased robustness to cross‐phase modulation, and RZ format has smaller inter‐symbol interference and high receiver sensitivity. CSRZ signal provides higher efficiency in spectrum utilization by reducing the nonlinear interactions between adjacent pulses . Here, every other bit is shifted in optical phase by 180°, leading to the suppression of carrier, and mean signal amplitude becomes null.…”

Impact of third-order dispersion in ultra-high speed long-haul optical fiber communication system

“…Dynamic dispersion compensation is becoming a concern of vital importance in high-speed optical fiber communication systems operating at 40 Gb/s and beyond as such expansion of the transmission bandwidth results in signal waveform distortion. Even if the transmission bandwidth is limited to a single channel, third-order dispersion (TOD) causes pulses to have trailing ripples which degrades the performance of the ultrahigh speed optical transmission systems [4][5][6]. Therefore, in such a high bit rate system, it becomes increasingly important to exactly compensate not only the second-order dispersion, but also the TOD or dispersion slope of the fiber.…”

“…One of the most important factors in the system, which affects the choices of all other system parameters, is the signal optical modulation format. In fact, signal optical spectral bandwidth, tolerance to chromatic dispersion, resistance to non-linear effects, susceptibility to accumulated noise and other system performance measures are directly related to the optical modulation format [6][7]. It has been found that for high-speed optical communication, RZ line coding with a duty cycle of 50% is inherently superior to the conventional NRZ-transmission scheme [8][9].…”