RZ-DPSK Format Research Articles

Investigation on Maximum Available Reach for Different Modulation Formats in WDM-PON Systems

Abstract Considering the growing demand for broadband of access networks, in the present paper we investigate various modulation formats as a way of increasing the performance of optical transmission systems. Non-return-to-zero (NRZ) on-off keying, return-to-zero (RZ) OOK, carrier suppressed RZ (CSRZ) OOK, duobinary (DB), NRZ differential phase shift keying (NRZDPSK), RZ-DPSK and CSRZ-DPSK formats are compared using the maximal achievable reach with bit error rate less than 10−9 as a criterion. Simulations are performed by using OptSim software tool. It is shown that using the transmission system without dispersion compensation the best results are shown by duobinary and CSRZ-OOK modulation formats, but with the system using dispersion compensating fiber (DCF) the longest transmission distance is achieved by RZ-DPSK modulation format. By investigating the influence of channel spacing for best-performed modulation formats, network reach decrease for transmission systems with DCF fiber has been observed due to channel crosstalk.

All-optical logic XOR gate for high-speed CSRZ-DPSK signals based on cSFG/DFG in PPLN waveguide

A report is presented on all-optical logic XOR operation for high-speed carrier-suppressed return-to-zero differential phase-shift keying (CSRZ-DPSK) signals based on cascaded sum- and difference-frequency generation (cSFG/DFG) in a periodically poled lithium niobate (PPLN) waveguide. The linear relationship of complex amplitudes between the converted idler and input signals enables a CSRZ-DPSK logic XOR gate with the converted idler carrying the RZ-DPSK format. An all-optical logic XOR gate for 40 Gbit/s CSRZ-DPSK signals is demonstrated in the experiment. Dual-channel-output and wavelength variable-in variable-out operations are also shown for the PPLN-based CSRZ-DPSK logic XOR gate.

Possible scenario for upgrading long-haul undersea optical fiber cable system using RZ-DPSK modulation format

A numerical study focusing on the feasible upgrade scenario of long-haul undersea optical fiber cable system is discussed. At first, appropriateness of the simulated performance is confirmed through conventional IM-DD modulation format. Then, capacity upgrade of the system is attempted by adopting the RZ-DPSK modulation format. As the RZ-DPSK format alone does not make capacity upgrade possible, additional methods are considered, and the modification of the dispersion map is revealed to be effective. The results show that it is possible to double the capacity of the long-haul undersea system using the RZ-DPSK modulation combined with the dispersion map modification.

Single-span transmission of WDM RZ-DPSK signal over 310-km standard SMF without using FEC and remote-pumping

To avoid significant stimulated Brillouin scattering (SBS) generation in a bidirectional Raman-pumped long single-span transmission system, the SBS threshold is studied in both return-to-zero on-off -keying (RZ-OOK) and RZ differential phase-shift keying (DPSK) systems. It shows that SBS threshold in an RZ-DPSK system is more than 10 dB higher than that in an RZ-OOK system, and SBS reflection is dominated by copumping, while counterpumping has minor effect. Error-free eight-channel single-span transmission is demonstrated over 310-km standard single-mode fiber using RZ-DPSK format and bidirectional Raman pumping, without applying forward-error correction and remote-pumping techniques.

Comparison of system performance at 50, 62.5 and 100 GHz channel spacing over transoceanic distances at 40 Gbit/s channel rate using RZ-DPSK

Assuming RZ-DPSK format at 40 Gbit/s channel rate, the impact on the Q-factor of a variable channel spacing has been evaluated in five WDM experiments conducted in a recirculating loop over transoceanic distances. A degradation of the Q-factor by nearly 3 dB is observed when the channel spacing is reduced from 100 to 50 GHz.

Ultra-long-span 500 km 16×10 Gbit/s WDM unrepeatered transmission using RZ-DPSK format

Ultra-long-span 500 km 16×10 Gbit/s WDM unrepeatered transmission without dedicated fibre for remote pumping is successfully demonstrated for the first time. Enabling technologies are the RZ-DPSK format, forward pumped Raman amplification, and second-order backward pumped Raman amplification in combination with enlarged effective area SMF and conventional SMF.