[1] [1] AKKARI N, DIMITRIOU N. Mobility management solutions for 5G networks: architecture and services[EB/OL].[2020-10-23]. https://www.sciencedirect.com/science/article/abs/pii/S1389128619306346.

[2] [2] PIZZINAT A, CHANCLOU P, SALIOU F, et al. Things you should know about fronthaul[J]. Journal of Lightwave Technology, 2015, 33(5): 1077-1083.

[3] [3] MA Y, XU Z, LIN H, et al. Demonstration of CPRI over self-seeded WDM-PON in commercial LTE environment[C]//Optical Fiber Communication Conference and Exhibition, March 22-26, 2015, Los Angeles, USA. Piscataway: IEEE, 2015: 1-3.

[4] [4] ZHANG D Z, ZHE D, JIANG M, et al. High speed WDM-PON technology for 5G fronthaul network[C]//2018 Asia Communications and Photonics Conference (ACP), November 19-23, 2018, Hong Kong, China. Piscataway: IEEE, 2018: 1-3.

[5] [5] FENG Q, LI W, WANG Y, et al. Colorless long-reach duplex WDM-PON with rayleigh backscattering noise mitigation using orthogonal codes[J]. Journal of Lightwave Technology, 2016, 34(3): 845-853.

[7] [7] BANERJEE A, PARK Y, CLARKE F, et al. Wavelength-division- multiplexed passive optical network(WDM-PON) technologies for broad-band access: a review[J]. Journal of optical networking, 2005, 4(11): 737-758.

[9] [9] LI X, GAN C, LIU Z, et al. Resilient intersection-ring architecture featuring online expansion and intersectional mutual protection[J]. IEEE/OSA Journal of Optical Communications and Networking, 2018, 10(6): 613-623.

[10] [10] YAO H, LI W, FENG Q, et al. Ring-based colorless WDM-PON with rayleigh backscattering noise mitigation[J]. IEEE/OSA Journal of Optical Communications & Networking, 2017, 9(1): 27-35.

[12] [12] ZHANG S, JI W, LI X, et al. Efficient and reliable protection mechanism in long-reach PON[J]. IEEE/OSA Journal of Optical Communi-cations and Networking, 2016, 8(1): 23-32.

[13] [13] BERGHMANS F. Reliability of optical fibers and components (invited paper)[C]//SPIE. Proceedings of SPIE-The International Society for Optical Engineering. New York: SPIE, 2005: 20-23.

[14] [14] GONG Y, GAN C, WU C, et al. Novel cobweb-topology WDM access network architecture featuring ultra-high reliability and easy scalability[J]. Optical and Quantum Electronics, 2014, 46(8): 999-1019.