[1] Chung H, Lee H H, Kim K O et al. TDM-PON-based optical access network for tactile internet, 5G, and beyond[J]. IEEE Network, 36, 76-81(2022).

[2] Pfeiffer T, Dom P, Bidkar S et al. PON going beyond FTTH[invited tutorial][J]. Journal of Optical Communications and Networking, 14, A31-A40(2022).

[3] Bonk R, Geng D, Khotimsky D et al. 50G-PON: the first ITU-T higher-speed PON system[J]. IEEE Communications Magazine, 60, 48-54(2022).

[4] Wey J S. The outlook for PON standardization: a tutorial[J]. Journal of Lightwave Technology, 38, 31-42(2020).

[5] Zhang D Z, Liu D K, Wu X M et al. Progress of ITU-T higher speed passive optical network (50G-PON) standardization[J]. Journal of Optical Communications and Networking, 12, D99-D108(2020).

[6] van Veen D, Houtsma V. Strategies for economical next-generation 50G and 100G passive optical networks[J]. Journal of Optical Communications and Networking, 12, A95-A103(2020).

[7] Nesset D. PON roadmap [invited][J]. Journal of Optical Communications and Networking, 9, A71-A76(2017).

[8] ITU[S](2015).

[9] Jin Z Y, Bi M H, Teng X Y et al. Design and anti-interference analysis of fault monitoring system based on multi-wavelength grouping for passive optical network system[J]. Acta Optica Sinica, 44, 0106027(2024).

[10] Hsueh Y L, Rogge M S, Shaw W T et al. Smooth upgrade of existing passive optical networks with spectral-shaping line-coding service overlay[J]. Journal of Lightwave Technology, 23, 2629-2637(2005).

[11] Lu Y, Gong Y, Wei Y Z et al. A smooth and gradual evolution to next generation PON based on simple line-coding[J]. IEEE Photonics Technology Letters, 26, 512-515(2014).

[12] Lu Y, Liu H Y, Zhou Q R et al. A smooth evolution to next generation PON based on pulse position modulation (PPM)[J]. IEEE Photonics Technology Letters, 27, 173-176(2015).

[13] Lu Y, Cao L F, Jiang L J et al. A smooth PON evolution based on PAM4 complement code[J]. Optical Fiber Technology, 74, 103058(2022).

[14] Lu Y, Cao L F, Wu S K et al. A novel smooth evolution to TWDM PON based on wavelength complement coding[J]. Optical Fiber Technology, 74, 103053(2022).

[15] Lu Y, Yao C, Ma W T et al. A novel smooth PON evolution based on signal cancellation[J]. Optical Fiber Technology, 80, 103422(2023).

[16] Lu Y, Zhou Q R, Wei Y Z et al. A smooth evolution to next generation PON based on orthogonal modulation[J]. Optics Communications, 339, 182-184(2015).

[17] Lu Y, Bi M H, Hu M et al. Orthogonal modulation application to achieve flexible migration and colorless ONUs for next generation PON[J]. Optics Communications, 403, 252-256(2017).

[18] Yao C, Lu Y, Cheng L et al. A novel multi-ary PolSK modulation for smooth PON evolution[J]. Optical Fiber Technology, 86, 103837(2024).

[19] Yan Y Q, Gan C Q, Liu Z K et al. Grant-sizing-differentiated bandwidth allocation algorithm for the coexistence of ONUs with and without wavelength tunability in WDM/TDM PONs[J]. Annals of Telecommunications, 73, 759-768(2018).

[20] Houtsma V E, van Veen D T. Investigation of modulation schemes for flexible line-rate high-speed TDM-PON[J]. Journal of Lightwave Technology, 38, 3261-3267(2020).

[21] Kaur R, Singh S. Polarization multiplexing and hybrid modulation based bandwidth efficient NG-PON2 coexisting with GPON and XG-PON[J]. Journal of Optical Technology, 88, 196-201(2021).

[22] Shen W W, Wang J Y, Li G Q et al. Auxiliary management and control channel transmission and performance of high-speed coherent frequency division multiplexing passive optical network system[J]. Acta Optica Sinica, 44, 0806001(2024).

[23] Cao L F, Lu Y, Xu K Q et al. A smooth PON evolution on one single wavelength based on mark ratio modulation[J]. Optical Fiber Technology, 71, 102906(2022).

[24] Alharbi A G, Singh M. Downstream performance evaluation of a 4×112 Gbps hybrid wavelength-polarization division multiplexed next generation-passive optical network[J]. Optical and Quantum Electronics, 54, 384(2022).

[25] Effenberger F J, Zhang D Z. WDM-PON for 5G wireless fronthaul[J]. IEEE Wireless Communications, 29, 94-99(2022).

[26] Kaur H, Singh S, Kaur R et al. 50G-next generation passive optical networks stage 2 using millimeter wave over fiber technique under the ITU-T G.9804 standardization[J]. Optical and Quantum Electronics, 55, 449(2023).