In order to realize multi-access in Ultra-WideBand（UWB）-over-fiber systems

this paper presents a scheme based on PM-IM conversion and multi-channel frequency discrimination for Binary Phase Shift Keying（BPSK）-encoding by using 3rd-order UWB pulse signals

analyzes its working principle and performs the relevant simulation using Optisystem13.0.It obtains different BPSK-encoded sequences with a central frequency of 6.7GHz and a relative bandwidth of 104.5%

complying with FCC specifications for UWB signals.Then

it analyzes the impacts of Gaussian pulse width and optical power on the simulation results

finding that when the Gaussian pulse width is 0.5bit

the frequency spectrum of the obtained signals is the most ideal

while when the light source power is below 26 dBm

the Power Spectral Density（PSD）complies with the FCC requirements.These results provide a possible scheme for the encoding requirements of multi-user access in UWB-over-fiber systems.