optical splice closures are used to distribute, splice, and store the
outdoor optical cables which enter and exit from the ends of the
closure. There are two connection ways: direct connection and splitting
connection. They are applicable to situations such as overhead, manwell
of pipeline, embedded situation etc. Comparing with terminal box,
the closure requires much stricter requirement of seal. Sealing ring and
air valve are required for closure, but that are not necessary for
terminal box.