Combine sugar and water in a small saucepan; bring to a boil, stirring occasionally until sugar dissolves. Remove from heat. Stir in peppercorns; let stand 20 minutes.
Drain sugar syrup through a fine sieve into a bowl; discard solids. Place half of sugar syrup, half of sliced strawberries, and fresh lemon juice in a blender, and process until smooth. Pour pureed mixture into a bowl. Repeat the procedure with remaining sugar syrup and sliced strawberries.
Pour mixture into the freezer can of an ice-cream freezer; freeze according to manufacturer's instructions. Spoon sorbet into a freezer-safe container; cover and freeze 4 hours or until firm.