Place the orange juice in a small saucepan and bring to a boil. Continue to cook at a simmer until reduced in volume to about 60ml, about 17 minutes.
Cook's Note: be careful near the end of cooking, as this can easily burn if left unattended.
Allow the reduced orange juice to cool to room temperature.
While the orange juice is reducing, trim off and discard the ends of the fennel bulbs, reserving a few fronds for garnish. Cut the fennel bulbs into thin crosswise slices, and place them in a salad bowl. Cut the onion into thin julienne. Pit the olives and cut them in half. Add the onion and olives to the salad bowl.
Using a sharp knife, cut away the peels from the oranges and leaving no white pith. Holding them over a small bowl, segment (supreme) the oranges, cutting in between the membranes to release each segment and letting them fall into the bowl. Refrigerate the segments until you are ready to serve the salad.
Transfer the cooled, reduced orange juice to a mixing bowl, and add the shallot, orange zest, red wine vinegar, and honey. Whisk thoroughly to combine. Add the oil in a thin, steady stream, whisking all the time, until completely incorporated and emulsified. Season the vinaigrette with salt, and pepper, to taste.
Arrange the orange segments over the fennel, red onion, and olives, and drizzle with the vinaigrette. Toss gently to combine. Serve the salad garnished with some of the reserved fennel fronds, and drizzle with additional olive oil, if desired.