In a saucepan, bring 2 cups (500 mL) fruit juice and 1 cup (250 mL) water to a simmer over medium-high heat. Add shrimp and return to a simmer. Remove from heat; cool to room temperature. Peel shrimp. Return shrimp to cooled poaching liquid; cover and refrigerate until needed, up to 2 hours.
In a small saucepan over medium heat, reduce remaining 1/2 cup (125 mL) juice by half; set aside to cool. When cool, whisk reduced fruit juice with lime zest, lime juice, olive oil, salt and pepper.
Lightly toss mango, onion, red pepper and cucumber with 3 tbsp (45 mL) of dressing mixture.
To serve, divide salad greens between 8 salad plates or bowls. Spoon mango and vegetable mixture evenly over greens. Drain shrimp; toss with remaining dressing mixture and arrange 3 shrimp on each salad.