How does Tennyson convey Ulysses' optimism?
Ulysses' optimism about setting sail once again that is. Particularly his optimism in the last few lines (There lies the port; the vessel puffs....To strive, to seek, to find, and not to yield)
It seems to me that the subtext of the question helps to answer the original question. Ulysses' characterization is not one that is rendered of fear. After enduring his harrowing journey, Ulysses is not shown to have been scarred or scared from his experience. Rather, he is one who is active, ready to get back to what it is he loved to do. Tennyson constructs his version of the Greek hero with a sense of unbridled optimism. The pain and experience of being isolated from home and wife is a far distant concern in his mind. Consider how Ulysses describes the journey about to be undertaken:
...touch the Happy Isles,/ And see the great Achilles that we knew.
This represents the positive energy with which Ulysses sets sail. The closing lines help to confirm this, as well. It should be noted that Tennyson might be doing this only to be add a complex level to the characterization of Ulysses. There is a sense that what he is about to undertake is uncertain and something in which death is present. Yet, in showing Ulysses as one who holds a note of positive energy towards this, the characterization is a complex one, reflecting that the Greek heroes are more than simplistic and one dimensional.