Challenges of 40/100Gbps and higher-rate deployments over long-haul transport networks

A low-cost alternative scheme to detect a 100 Gbps PM-DQPSK signal

“…By contrast, the NRZ-DQPSK signal is more tolerant to the filter bandwidth. Figure 4 also shows the simulated sensitivity of the DIs receiver based on Pincemin [4]. As can be seen, the sensitivity of the DIs receiver is about 0.4  0.2 dBm higher than that of the proposed receiver, either for NRZ-DQPSK or for RZ-DQPSK formats.…”

“…Also, due to that the 40 Gbps DQPSK signal is compatible with the 50-GHz ITU grid and the 50-GHz based ROADMs [4], we test the receiver performance under narrow optical filtering in this section.…”

“…Differential quadrature phase shift keying (DQPSK) modulation format has been proposed to further increase the chromatic dispersion and polarization mode dispersion (PMD) tolerance of 40 Gbps channels [1][2][3][4][5][6][7][8]. Owing to its reduced optical bandwidth relative to the traditional binary systems, it is proposed as a promising candidate for high-speed long-haul optical transmission systems.…”

“…In addition, its compatibility with the 50 GHz International Telecommunication Union (ITU) grids could allow mixing 10 Gbps NRZ and 40 Gbps DQPSK channels in a same wavelength division multiplexing (WDM) transmission system. Thus, when a 10 Gbps WDM system is saturated in terms of capacity, one could consider replacing step by step the 10 Gbps channels by the 40 Gbps ones as a function of the capacity needed [4].…”

“…At the transmitter, a DQPSK signal is typically obtained by two embedded Mach-Zehnder modulators, driven by two nonreturn to zero (NRZ) data streams I and Q. At the receiver, direct-detection receiver based on two delay interferometers (DIs) [4] is usually used to detect a DQPSK signal.…”