  Laser inter-satellite links (LISLs) between satellites in a free-space
optical satellite network (FSOSN) can be divided into two classes: permanent
LISLs (PLs) and temporary LISLs (TLs). TLs are not desirable in next-generation
FSOSNs (NG-FSOSNs) due to high LISL setup time, but they may become feasible in
next-next-generation FSOSNs (NNG-FSOSNs). Using the satellite constellation for
Phase I of Starlink, we study the impact of TLs on network latency in an
NG-FSOSN (which has only PLs) versus an NNG-FSOSN (which has PLs and TLs) under
different long-distance inter-continental data communications scenarios,
including Sydney-Sao Paulo, Toronto-Istanbul, Madrid-Tokyo, and New
York-Jakarta, and different LISL ranges for satellites, including 659.5 km,
1,319 km, 1,500 km, 1,700 km, 2,500 km, 3,500 km, and 5,016 km. It is observed
from the results that TLs provide higher satellite connectivity and thereby
higher network connectivity, and they lead to lower average network latency for
the NNG-FSOSN compared to the NG-FSOSN in all scenarios at all LISL ranges. In
comparison with the NG-FSOSN, the improvement in latency with the NNG-FSOSN is
significant at LISL ranges of 1,500 km, 1,700 km, and 2,500 km, where the
improvement is 16.83 ms, 23.43 ms, and 18.20 ms, respectively, for the
Sydney-Sao Paulo inter-continental connection. For the Toronto-Istanbul,
Madrid-Tokyo, and New York-Jakarta inter-continental connections, the
improvement is 14.58 ms, 23.35 ms, and 23.52 ms, respectively, at the 1,700 km
LISL range.
