This paper studies the performance of optical orthogonal frequency-division multiplexing (OFDM)-based multi-user integrated sensing and communication (ISAC) systems employing non-orthogonal multiple access (NOMA). Due to their inherent high peak-to-average power ratio (PAPR), OFDM waveforms are clipped to fit the limited dynamic range of the optical transmitters (e.g., light-emitting diodes (LEDs)), resulting in clipping distortion. To alleviate the impact of the distortion, we propose a novel transmitter architecture where the clipping processes are performed before NOMA superposition coding. We then analyze the performance of the proposed optical ISAC systems considering the effects of power allocation and clipping distortion. For the communication subsystem, we analyze the effect of NOMA on the achievable sum rate and bit error rate (BER). For the sensing subsystem, the root mean square error (RMSE) and Cram\'er-Rao bound (CRB) of estimating the transmission distance accuracy are obtained. Simulation results reveal that allocating more power to the strong user yields a higher sum rate, lower BER, and better sensing performance, whereas a more balanced power allocation among users results in degraded BER and sensing performance.

翻译：本文研究了采用非正交多址接入（NOMA）技术的光正交频分复用（OFDM）多用户集成感知与通信（ISAC）系统的性能。由于OFDM波形固有的高峰均功率比（PAPR），需对其进行限幅处理以适应光学发射器（如发光二极管LED）有限的动态范围，从而引入限幅失真。为减轻失真的影响，我们提出一种新型发射机架构，将限幅处理置于NOMA叠加编码之前。随后，在考虑功率分配和限幅失真影响的情况下，分析了所提光ISAC系统的性能。针对通信子系统，分析了NOMA对可达和速率与误码率（BER）的影响；针对感知子系统，推导了传输距离估计精度的均方根误差（RMSE）和克拉美-罗界（CRB）。仿真结果表明，为强用户分配更多功率可获得更高的和速率、更低的误码率以及更优的感知性能，而用户间更均衡的功率分配则会导致误码率与感知性能的下降。