The only way to get a fiber optic field trip is to have a gibberish question on question 3 or 4. If you get a gibberish question on 3, your field trip will be on question 7; if your gibberish question is 4 your trip will be on question 8.
Cheats
On a gibberish question type in "fuck you". Different things will happen depending on the version of YDKJ that you are playing. Do this three times and the program will shut down because you are a true vulgarian.