Bring a pot of salted water to a boil and drop in the rice noodles. Cook according to the package directions or until tender with a bit of bite. This will only be a couple of minutes, so don't go anywhere. Taste the noodles frequently to have an idea of when they are getting close. Mine cook in about 3 minutes. Drain noodles and rinse under ice cold water. Leave to drain.
In a small bowl, whisk together the lime juice, soy sauce, fish sauce, rice vinegar and sesame oil.
Slice the cucumber lengthwise and scrape out the seeds with a spoon. You should have two cucumber "canoes". Flip them onto the flat side and thinly slice into half moons. Grate the carrot on the large side of a box grater. Finely chop the green onion.
In a large bowl, toss together the cold rice noodles, shrimp, cucumber, red pepper, grated carrot, and green onions. Pour the vinaigrette over the salad and toss well to coat everything. Chill for about an hour or up to 4 hours.
To serve, heap salad high on a platter. Sprinkle with sesame seeds and serve.
Sliced avocado, sliced mango or chopped cilantro are all additional toppings that are delicious with this salad.Also, this salad is almost as good on the second day. I usually add a little fresh cilantro and send it to school in a chilled thermos for the boy's lunch.