It can't be a pure catenary because once the bridge is fully constructed and loaded the cables won't only be under its self-weight. If the cable is light compared to the deck (likely) then it'll tend to be a parabola.
I assume that this is the same pedestrian bridge that you have asked about before. What is your role in this project?
To answer your question, the cables geometry depends on the loading. If you look at a large suspension bridge for road traffic or railway traffic the permanent load will be a large part of the total load. One advantage for that is that the permanent load does not move. And that simplifies some things.
For a pedestrian bridge the bridge deck is probably more lightweight. This may mean that the live load will be a larger part of the total load and that has to be managed. This requires some thought that is hard to describe in a short post.
But I have one question for you. If you have a bridge with 125 m span, why a suspension bridge and not a cable stayed bridge?
To choose the best type of bridge for a given situation requires experience. Have you designed bridges before?
