In my view smoked fish - especially salmon - and raw fennel tastes are made for each other. The crispness of the fennel complements the subtlety of smoked or cured salmons (e.g. gravad lax).
I like to dress the fennel rather than have it raw, but I think that choosing the components of the dressing is crucial. Stronger oils or vinegars work with some food but are overpowering with fish. For example some years ago, when first doing fennel salad with fish I tried olive oil. The problem was the salmon taste was overpowered by the olive oil taste.
After a bit of experimentation I have settled on the following:
1 medium to large fennel bulb
30 ml (2 tbsp) rapeseed oil
15 ml (1 tbsp) rice wine vinegar
1. Slice the fennel vertically through the bulb in thin slices (I set my machine to 1.5 mm). For a large fennel I halve the slices to make them more manageable
2. Mix dressing ingredients
3. Toss fennel and dressing
4. Serve in small container (I do this to stop the dressing getting on the salmon on the plate)