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DD-OOK Multicore Fiber Systems Impaired by Intercore Crosstalk and Laser Phase Noise

Alves , T. M. F. ; Cartaxo, A. ; Rebola, J.

Journal of Lightwave Technology Vol. 40, Nº 5, pp. 1544 - 1551, February, 2022.

ISSN (print): 0733-8724
ISSN (online):

Scimago Journal Ranking: 1,51 (in 2022)

Digital Object Identifier: 10.1109/JLT.2021.3138186

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Direct-detection on-off keying (DD-OOK) weaklycoupled
multicore fiber (WC-MCF) systems impaired by intercore
crosstalk (ICXT) and laser phase noise are investigated numerically
and experimentally. This is performed for systems with
a product between the bit rate and the absolute value of the
skew between cores much larger than one. It is shown that the
phase noise increases the instantaneous ICXT power fluctuations.
The standard deviation of the short-term average ICXT (STAXT)
power induced by the phase noise depends on the product between
the laser linewidth and the absolute value of the skew between
cores (linewidth ×| skew|). When linewidth ×| skew|1, typical
of distributed feedback (DFB) lasers (linewidth in the few MHz
range) and MCFs with skew in the μs range, the decrease of the
standard deviation of the STAXT power induced by the phase noise
is 5 dB per decade of linewidth ×| skew| increase. For linewidth
×| skew|1, typical of external cavity lasers (ECLs) and DFB
lasers, and MCFs with skew of a few ns, the standard deviation
of the STAXT power remains almost unaffected by the phase
noise. Experimental results showthat, comparedwith lowlinewidth
ECLs, 10 Gb/s DD-OOK WC-MCF systems using DFB lasers as
optical sources in the interfering cores and skew in the range
between 2.4 ns and 5.4 ns,may require an additional ICXT margin
up to 8 dB for a given outage probability. The additional ICXT
margin and the lower amplitude of the STAXT power fluctuations
observed experimentally for DFB lasers suggest that the level of
the fluctuations of the STAXT power may be an inadequate system
performance indicator. The dependence of the outage probability
on the interfering core count is also investigated experimentally. It
is shown that, for systems with bit rate ×| skew|1, the outage
probability only depends on the total ICXT power and not on the
interfering core count.