Heat a grill to high.
Cook the pasta according to the package's directions. Heat the alfredo sauce in a large, deep skillet over low heat.
Meanwhile, coat the fennel bulb quarters with 1 tablespoon oil and season with salt. Grill, turning once, until grill marks appear on both cut sides, about 5 minutes. Transfer to a cutting board. When cool enough to handle, cut out the core and discard, then thinly slice the bulb.
Coat the shrimp with the remaining tablespoon oil and season with salt and pepper. Grill, turning once, until just opaque throughout, about 2 minutes per side. Transfer to a plate.
Drain the pasta and immediately add to the heated sauce. Add the fennel and toss until everything is evenly coated. Divide among serving dishes and top with the grilled shrimp. Pluck and chop the fennel fronds and sprinkle on top, along with freshly ground black pepper. Serve immediately.
You can use tagliatelle or linguine instead of the fettuccine. You can swap a small head of radicchio for the fennel. You can omit the shrimp for a vegetarian option.