Crosstalk dynamics in multi-core fibers

Abstract

Inter-core crosstalk is a potential limitation on the achievable data-rates in optical fiber transmission systems using multi-core fibers. Crosstalk arises from unwanted coupling between cores of a homogenous multi-core fiber and it's average power has been observed to vary over time by 10s of decibels, potentially requiring an additional performance margin to achieve acceptable outage probability. Most investigations of crosstalk have so far only considered continuous wave laser light or amplified spontaneous emission as sources of crosstalk. In this paper, we theoretically and experimentally investigate the time-dependence of inter-core crosstalk in a homogeneous multi-core fiber when considering signals with various modulation formats and symbol rates. We find that crosstalk power fluctuations depend on the symbol rate, modulation and skew between cores. For carrier-free signals, such as quadrature amplitude modulation, the crosstalk power is nearly constant for expected conditions of multi-core transmission systems. However, carrier-supported signals, such as OOK, always induce time-varying crosstalk powers.

Inter-Core Crosstalk in Multicore Fibers: Impact on <tex>$56-\text{Gbaud}/\lambda$</tex> /Core PAM-4 Transmission

“…This is confirmed by the BER results. Third, the crosstalk dynamic in weakly-coupled MCF, which is theoretically described previously 5 , was observed during the measurements and are depicted by the error bars, which can substantially differ from the mean BER values averaged over the number of processed measurements.…”

“…Figure 2 compares the BER curves for three configurations of the fiber-link: first, the 56-Gbaud PAM-4 signals are coupled only into the core 1 of the weakly-coupled multicore fiber while other cores are idle; second, signals are coupled into all cores of the uncoupled multicore fiber while the traces of the signals, which are received after transmission over the core 1, are captured by the DSO for further post-processing and a BER counting; third, an optical-back-to-back (OB2B). For each data point, five (5) traces are captured and analyzed. Figure 2 displays the mean BER values.…”

Intercore crosstalk in direct-detection homogeneous multicore fiber systems impaired by laser phase noise

“…Most of the ICXT characterizations performed so far used continuous wave (CW) or a single modulated tone as interfering crosstalk signal. Recently, the time-dependence of the ICXT in a homogeneous MCF has been theoretically and experimentally studied considering signals with various modulation formats and symbol rates [17][18][19]. It was concluded that MCF-based systems employing carrier free signals, such as quadrature amplitude modulation (QAM) typical of long-haul links, exhibit nearly constant ICXT power over time [17].…”

“…Recently, the time-dependence of the ICXT in a homogeneous MCF has been theoretically and experimentally studied considering signals with various modulation formats and symbol rates [17][18][19]. It was concluded that MCF-based systems employing carrier free signals, such as quadrature amplitude modulation (QAM) typical of long-haul links, exhibit nearly constant ICXT power over time [17]. In contrast, direct detection (DD) MCF-based systems using carrier supported signals are impaired by ICXT power that may fluctuate significantly over time and require an additional performance margin to operate adequately [17,18].…”

“…It was concluded that MCF-based systems employing carrier free signals, such as quadrature amplitude modulation (QAM) typical of long-haul links, exhibit nearly constant ICXT power over time [17]. In contrast, direct detection (DD) MCF-based systems using carrier supported signals are impaired by ICXT power that may fluctuate significantly over time and require an additional performance margin to operate adequately [17,18]. In DD-MCF-based systems using carrier supported modulation formats, the signal transmitted in a given core is recovered after the beating between the data and optical carrier signals transmitted in the same core (test core) according to the photodetector square law.…”