Phase Noise Correlation and Properties of Skew Between Heterogeneous Cores in MCF

We propose a multi-core fiber (MCF) containing a low-latency core as a transmission line for master-slave carrier phase estimation (MS-CPE). To utilize a low-latency signal as a master channel, we previously proposed a coherent detection setup that ensures laser phase noise correlation between the low-latency master channel and the slave channels. However, skew variation is inevitable due to changes in fiber temperature, which affects the phase noise correlation. In this paper, we evaluate the temperature coefficient of skew of the fabricated MCF containing a single low-latency core (LLC) and conventional silica cores (SCs), and we numerically investigate the signal-to-noise ratio (SNR) penalty resulting from the temperature dependence of the skew. We show that a temperature coefficient of 0.3 ps/km/°C can support an SNR penalty of less than 1 dB in QPSK transmission for a transmission length of up to approximately 1500 km in a temperature change of ±55 °C. However, in 10,000-km QPSK and 16QAM transmissions, more stringent requirements of ±10 °C and ±2 °C, respectively, are needed in order to maintain the SNR penalty of less than 1 dB.