I did my sons first passport too we travel to mexico and you do need to send the original, it doesn't matter if it's the long one or the short one l, they will send it back.
We just went through this process you need to send the original one in. The person on the phone said that they recommend you get tracking when sending the application. They will send it back once they have processed the application (no more than 2 weeks) you do need to sign for your package when they mail the birth certificate back.
You need to send the original birth certificate. They will send it back. If you present yourself to an office, they will do a copy but they need to see the original one.
U need Original birth certificate
What do I have to do after birth and how do I fasten the process and how much time do I need to get the passport