Heat oil in a large pot over medium-high heat. Add shrimp; stir-fry 2 to 3 minutes or just until shrimp turn pink. Transfer shrimp to a plate. Add ginger, garlic, and bell pepper to pot, and sauté 1 to 2 minutes or until tender. Stir in curry paste, broth, coconut milk, and, if desired, fish sauce. Add lime juice and brown sugar, and bring to a boil; reduce heat, and let simmer 5 minutes. Stir in shrimp. Garnish, if desired.
*Available in your grocer's ethnic foods section; red Asian chili sauce may be substituted.