Arrange the salmon slices on four individual plates and arrange the slices of fennel on top. then scatter over the cucumber julienne strips.
Mix together the lemon juice and pepper in a small bowl. Slowly whisk in the olive oil to make a creamy vinaigrette. Stir in the chopped dill.
Spoon a little vinaigrette over the fennel and cucumber. Drizzle the remaining vinaigrette over the salmon and garnish with sprigs of dill.
Top each salad with a spoonful of caviar, if you like.