Bisimple inverse $\omega$-semigroups of left I-quotients

A subsemigroup $S$ of an inverse semigroup $Q$ is a left I-order in $Q$ if every element in $Q$ can be written as $a^{-1}b$ where $a,b \in S$ and $a^{-1}$ is the inverse of $a$ in the sense of inverse semigroup theory. If we insist on $a$ and $b$ being $\mathcal{R}$-related in $Q$, then we say that $S$ is a straight left I-order in $Q$. We give necessary and sufficient conditions for a semigroup to be a left I-order in a bisimple inverse $\omega$-semigroup.