Languages of the Ottoman Empire
The language of the court and government of the Ottoman Empire was Ottoman Turkish, but many other languages were in contemporary use in parts of the empire. Although the minorities of the Ottoman Empire were free to use their language amongst themselves, if they needed to communicate with the government they had to use Ottoman Turkish.
Ottoman poetry
Even in modern Turkey, however, Ottoman Divan poetry is a highly specialist subject. Much of this has to do with the fact that Divan poetry is written in Ottoman Turkish, which was written using a variant of the Arabic script and made extensive use of Arabic and Persian words, making the language vastly different from modern Turkish. In its own time, knowledge of this form of literary Turkish was largely limited to the educated classes.