Abstract
In this work, we propose to use four-level pulse amplitude modulation (PAM4) and multi-core fibers (MCFs) to support very high capacity datacenter interconnect (DCI) links. The limitations imposed by inter-core crosstalk (ICXT) on the performance of 112 Gb/s up to 80 km-long optically amplified PAM4 inter-DCI links with intensity-modulation and direct-detection and full chromatic dispersion compensation in the optical domain are analyzed through numerical simulation for high and low skew-symbol rate product (SSRP). With only one interfering core, we show that those PAM4 inter-DCI links achieve an outage probability (OP) of 10−4 with a maximum ICXT level of −13.9 dB for high SSRP and require an ICXT level reduction of about 8.1 dB to achieve the same OP for low SSRP. Due to using full dispersion compensation, for an OP of 10−4, the maximum acceptable ICXT level shows only a 1.4 dB variation with the MCF length increase from 10 km to 80 km. When considering the ICXT induced by several interfering cores, the maximum ICXT level per interfering core for an OP of 10−4 decreases around 3 dB when doubling the number of interfering cores. This conclusion holds for high and low SSRP regimes. For two interfering cores, we show that a single interfering core with low SSRP is enough to induce a severe reduction of the maximum acceptable ICXT level.
Highlights
In the last few years, worldwide traffic in telecommunication networks has been increasing dramatically around 30% per year [1,2]
Two different skew-symbol rate products (SSRPs) are analyzed: (i) |Smn · Rs | 1, where the symbol rate of the PAM4 signal is much higher than the ICXT decorrelation bandwidth [14], and the ICXT creates amplitude levels in the received eye-pattern that seem to exhibit a “noise”-like behavior [21], and (ii) |Smn · Rs | 1, where the symbol rate of the PAM4 signal is much lower than the ICXT decorrelation bandwidth [14] and well-defined amplitude levels in the eye-patterns are created due to Receiver electrical filter bandwidth
As the maximum number of interfering cores effectively affecting the performance is typically 8, an ICXT level per interfering core not exceeding around −32.5 dB leads to an outage probability (OP) lower than 10−4 in the amplified PAM4 link studied in this work
Summary
In the last few years, worldwide traffic in telecommunication networks has been increasing dramatically around 30% per year [1,2] This growth is fueled by the progressive development of next-generation 5G mobile broadband technologies, expansion of the Internet of Things, and increasing of high data-rate applications such as streaming video, real-time gaming, cloud computing, and big data analysis [3]. The ICXT impact on the system performance of an optically amplified inter-datacenter link with a single interfering core, optical amplification, and chromatic dispersion compensation has been assessed in terms of the BER, eye-patterns, and OP [26]. The OP due to ICXT induced by multiple interfering cores in IM-DD interDCI links up to 80 km-long with PAM4 signal transmission, full loss and perfect optical dispersion compensation, is assessed and analyzed using numerical simulation. This work extends the preliminary work presented in [26] by assessing the ICXT impact on the OP, for a single interfering core and MCF lengths ranging from 10 km to 80 km, for several interfering cores with the same skew and for two interfering cores with different skews
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