OFDM measurment tools

hi everyone
I want to know if there is a way to measure the number of carriers in OFDM transmitters
thanks

It is a definite value for every type of OFDM transmitter. What is the purpose of such a measurement?

I want to know which parameters of OFDM systems are measurable ( mudulation , EVM , number of carriers , guard interval ...)
I found that the EVM and modulation are measurable with Vector Signal Analyzer , now for the remainders i'm searching

If you try to measure the single OFDM symbol duration (i dont know how, what changes may be detected), you may estimate a subcarrier spacing as 1/T.