Abstract
For their capability of electronic dispersion compensation, transmission systems based on direct detection of single-sideband (SSB) signals are attractive candidates as energy-efficient and cost-effective alternative solutions to intradyne digital coherent systems for interdata center and metro applications. The Kramers–Kronig (KK) receiver scheme has been shown to provide superior performance compared to other schemes in signal-to-signal beat interference (SSBI) cancelation in these direct-detection systems. In this paper, we propose a low-complexity and cost-effective scheme of generating an optical superchannel comprising multiple SSB channels, based on a single quantum-dot mode-locked laser source. The proposed system does not require additional photonic or RF components at the transmitter to generate the required SSB signal with a continuous wave (CW) carrier. It also preserves the full digital-to-analog converters’ bit resolution for data modulation, in contrast to other methods based on digital generation of the CW component. Simulations of system performance with KK receiver, based on measured laser output field, show that the proposed system can achieve bit-error ratio below the hard-decision forward error correction threshold for 16-QAM Nyquist SSB signals after transmission through three amplified spans of single-mode fiber in a 240-km link. Using 8 KK channels at 23 GBaud each, the proposed scheme will be able to achieve a transmission rate of 736 Gb/s with noncoded spectral efficiency of 2.45 b/s/Hz. The impacts of carrier-to-signal power ratio, per channel launch power into the fiber, and component frequency drifting on transmission system performance are also discussed.
Highlights
The increasing demand for high data rate and high interface density optical links for metro, long reach data center interconnect (DCI) and backhaul applications has brought increased interest in developing cost-effective and energy-efficient transmission schemes to operate at ࣙ100 Gb/s
We have proposed a low-complexity and cost-effective scheme for generating a superchannel of SSB modulation based on a single quantum-dot mode-locked laser (QD-MLL) optical source
By utilizing the mutual coherence between adjacent comb lines, the proposed system has been shown through experimental measurement of a QD-MLL and numerical simulations to exhibit good system performance, despite the relatively high individual linewidths and relativeintensity noise (RIN) of QD-MLL comb lines
Summary
The increasing demand for high data rate and high interface density optical links for metro, long reach data center interconnect (DCI) and backhaul applications has brought increased interest in developing cost-effective and energy-efficient transmission schemes to operate at ࣙ100 Gb/s. The CW tone can be added at either side of the spectrum, either digitally, known as the digital virtual carrier [9], or in the analog domain by adding an RF local oscillator signal directly to the optical I/Q modulator driving signals [10], [11] For these two bandwidth-efficient carrier insertion techniques, the first method has the disadvantage of reduced DAC resolution available for data signals by at least 50% because of the increased dynamic range of the signal (by a factor of ࣙ2) to achieve the minimum phase condition, which affects system’s performance for high-order modulation formats, and limits system spectral efficiency [12]. System performance simulations, based on experimentally recorded complex optical field of QD-MLL, show that even in the presence of relatively high-intensity noise, the proposed system performs well below the hard-decision forward error correction (HD-FEC) threshold bit-error ratio (BER) with 16-QAM modulation for up to 240 km of standard single-mode fiber (SSMF) This makes this system an attractive solution for long-reach DCI and metro applications. Results of system performance analysis based on semi-numerical simulations are presented in Section 4, and Section 5 provides the conclusions
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