Janse, 30, is an ex-Netherlands Under-21 international and previously played for Italian Serie B side Ternana.
He predominantly plays at right-back but he can play anywhere across the back four and on the right of midfield.
Janse is the second addition at Brisbane Road in as many days after the arrival of midfielder Zan Benedicic on a deal until January.
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Leyton Orient have signed Dutch defender Jens Janse on a deal until the end of the season.