Phototransistors interfacing with a serial port

So I really don't have too much experience with interfacing stuff and PCs (read: none) and I have a question. If I was to wire up about 5 phototransistors in series, all with a laser aimed at all of them, with the anode hooked up to TxD, and the cathode hooked up to RxD, and I had a program sending 500 bits to it per second, and checking for response.. will it basically be able to detect if one of the lasers are broken? Thanks!