Design and Performance Analysis of Hybrid Multidimensional OAM-DM-WDM-OFDM-PON System with High-Capacity and Long-Distance Transmission  
[PERSON] College of Electronic and Information Engineering, Shandong University of Science and Technology, 579 Front Bay Harbour Road, Qingdao 266590, China; [EMAIL_ADDRESS] (Q.D.); [EMAIL_ADDRESS] (L.Z.); [EMAIL_ADDRESS] (H.L.); [EMAIL_ADDRESS] (Q.L.); [EMAIL_ADDRESS] (X.C.); [EMAIL_ADDRESS] (Z.D.); [EMAIL_ADDRESS] (Q.Y.); [EMAIL_ADDRESS] (L.L); [EMAIL_ADDRESS] (Q.L.); [EMAIL_ADDRESS] (L.L); [EMAIL_ADDRESS] (Q.Y.); [EMAIL_ADDRESS] (L.L); [EMAIL_ADDRESS] (Q.L.); [EMAIL_ADDRESS] (L.L); [EMAIL_ADDRESS] (Q.L.); [EMAIL_ADDRESS] (L.L); [EMAIL_ADDRESS] (L.L); [EMAIL_ADDRESS] (L.L); [EMAIL_ADDRESS] (L.L); [EMAIL_ADDRESS] (L.L); [EMAIL_ADDRESS] (L.L); 20218213007@dsduet.  
conventional dimension resources of the photon has reached a limitation. In addition to the known physical dimension (e.g., amplitude, phase, frequency/wavelength), the spatial structure of the light wave should be fully considered. Meanwhile, mode division multiplexing (MDM) using orthogonal spatial modes to load signals was an emerging technique for large-capacity data communication [7]. Recently, a lot of research works have been carried out on spatial modes in linearly polarized (LP) modes [8], orbital angular momentum (OAM) modes [9], and vector modes [10]. Particularly, LP and OAM modes are most widely used in MDM for efficiently increasing the capacity of the optical fiber link.  
[PERSON] et al. successfully revealed the property of Laguerre-Gaussian (\(LG_{lp}\)) carrying OAM in 1992 [11]. Since then, OAM of light was a promising means for exploiting the spatial dimension of light to increase the communication capacity. However, the bottleneck to implement this technique relies on the generation and detection of OAM states, either inside free space optic (FSO) [12] or in optical fibers [13]. In addition, OAM is also used in optical imaging [14], quantum communication field [15], and so on. For OAM-FSO communication, [PERSON] and [PERSON] demonstrated OAM beams carrying four-level pulse-amplitude modulation (PAM-4) signal in FSO polarization-insensitive links [16]. [PERSON] et al. proved that a data rate of 200 Gbps was achieved on a 1 m FSO link using two LG beams with different radial indexes [17]. Various MDM efforts have been focused on FSO links, but have little report devoted to optical fiber communication. Furthermore, the combination of OAM with polarization modulation (PM), OFDM, and other multi-dimensional modulation techniques is rarely considered in recent OAM optical fiber communication research. For OAM optical communication, a report on two-dimensional multiplexing of TDM and OAM was achieved in [18; 19]. [PERSON] et al. demonstrated the MDM-PON based on three-dimensional carrier-less amplitude/phase (3D-CAP) modulation that transmits over 4.1 km ring-core fiber (RCF) [20].  
In this work, a more dimensional multiplexing OAM-DM-PON system, which combines WDM and OFDM is discussed in great detail to further improve the communication capacity of the access network. And the BER performance versus transmission distance is investigated. On the one hand, LG modes with different wavelengths are used to load OFDM signals at the transmitter side and a 10-80 km multimode fiber (MMF) for OAM multiplexing is required at the downstream transmission link. On the other hand, the case of a single OAM mode and a single wavelength system is examined and evaluated. Furthermore, the simulation results of three (OFDM, OOK, QPSK) modulation schemes with two LG modes multiplexing are also presented and compared. The simulation results verified that OAM is compatible with other dimensions of photons and can well meet the needs of high-capacity communication.