Combine chicken broth, salt, and black pepper in a large soup pot and bring to a coil over high heat. Add carrots, fennel, and orzo; return to a boil. Reduce heat to low and simmer, partially covered, until orzo and vegetables are tender, eight to ten minutes. Stir in chicken and cook until heated through, about five minutes. Switch off heat, stir in lemon juice and dill. Yields eight servings.