We experimentally demonstrate an improved orthogonal frequency division multiplexing (OFDM) into the pulse width modulation (PWM) scheme for the X-ray communication (XCOM). The scheme is insensitive to the nonlinearity of the grid-controlled X-ray tube with switching 'on' and 'off' between two points. The dependence of this system's bit-error-rate (BER) performances on the data rates and the working parameters including the anode voltage and filament current of the grid-controlled X-ray tube are studied. The OFDM-PWM scheme reaches the data rate of 360 kbps at a BER of the forward error correction threshold of 3.8 × 10-3 over a 5 cm air channel. In addition, an experiment aided by density-based spatial clustering of applications with noise nonlinear compensation is carried out, and the results demonstrate the improvements in Q-factor by 0.62 dB.