54 HS.Abbas,M.A.Gregory Journal of Network and Computer Applications 67(2016)53-74 6.2 Spectral flexibility..................................63 6.3 C0-existence..,………………… 63 6.4 ODN re-use 63 6.5 4 6.6. Additional components 64 7. Precents implementation of TWDM. .64 8 XDM/WDM hybrid technologies................................ 65 8.1. OCDM/WDM-PON 5 8.2. OFDM/WDM-PON 66 9. XDM/TDM hybrid technologies.......... 66 9.1. OCDM/TDM-PON 66 9.2. OFDM/TDM-PON 67 10. Hybrid XDM/TDM/WDM................ 6 11. NG-PON2 challenges...... 67 11.1. Increase the capacity. 67 11.2. Extend the reach. 6 11.3.Power saving,...·..··· 68 12. PON reliability aspects..··. 9 12.1. PON protection mechanisms...... 69 122. PON security..,·· 69 12.3. P0 N monitoring.… 69 13. Future aspects of PON........·· 70 14. Discussion and future works...,....·.,,·.··· 15. Conclusion.++…+ 71 References …….72 1.Introduction splitters by fiber.The optical splitters connect to customer pre- mises making PON a point to multi-point architecture(P2MP) Passive Optical Networks (PONs)are a series of promising (Ragheb and Fathallah,2012). broadband access network technologies that offer enormous The EPON and the GPON standards have the same general advantages when deployed in fiber to the home(FTTH)scenarios. principle in terms of framework and applications but their The advantages include a point to multi-point architecture,high operation is different due to the implementation of the physical quality triple play service capabilities for data,voice and video, and data link layers (Olmos et al.,2011).EPON is defined by IEEE high speed internet access,and other services in a cost-effective 802.3 and it is widely deployed in Asia whilst GPON is deployed in manner(Ragheb and Fathallah,2012). a number of other regions.GPON's requirements were defined by Over the past decade several PON architectures have been the Full Service Access Network (FSAN)group that was ratified as developed by the International Telecommunications Union (ITU) ITU-T G.984 and is implemented in North America,Europe,Middle and the Institute of Electrical and Electronic Engineers(IEEE).The East,and Australasia (Van Veen et al.,2011:Skubic et al.,2009). four main PON variations developed by the ITU and IEEE can be In this paper the advancement of PON technology is classified categorized into two groups.The first kind of architecture is based into three generations:the first generation(deployed PON),next on Asynchronous Transfer Mode (ATM)and includes ATM PON generation stage 1(NG-PON1),and next generation stage 2(NG- (APON),Broadband PON(BPON)and Gigabit PON(GPON)and the PON2).The evolution of the PON architectures and their corre- second group consists of Ethernet PON(EPON).EPON and GPON sponding capacity features are shown in Fig.2. are the most popular PON variations found in use today.A con- The first generation of PON is based on Time Division Multiple ventional PON architecture is presented in Fig.1 (Ragheb and Access(TDMA)and provides an EPON downstream rate of 1 Gbps Fathallah,2012).In the figure,it can be seen that the PON archi- and a GPON downstream rate of 2.4 Gbps.The NG-PON1 increases tecture consists of an Optical Line Terminal (OLT).Optical Dis- the data rate up to 10 Gbps for both standards(Biswas and Adak, tribution Network(ODN),and Optical Network Units(ONU).The 2011).There are two main scenarios to achieve an upgrade that are OLT is placed at the Central Office (CO)and connected to the the upgrade from deployed EPON to XG-EPON and from deployed GPON to XG-GPON.An upgrade from deployed GPON to XG-EPON Central office Optical Distribution Network Customer Side Feeder Fiber】 Distribution Fiber ONU1 NG-PON3 1o0/40 Gb/s XG-EPON NG-PONZ Splitte ONU 2 OLT M0/10D/ 10/10Gb/ N EPON 1Gb/s ONU 3 XG-GPON XG-PON 1o/2.4Gb/ GPON -XG-PON2 2.5/1Gb/ 10/10Gb/s ONU N 2004 2010 Years 2015 2020 Fig.1.PON architecture Fig.2.PON generations6.2. Spectral flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 6.3. Co-existence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 6.4. ODN re-use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 6.5. Pay as you grow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 6.6. Additional components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 7. Precents implementation of TWDM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 8. XDM/WDM hybrid technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 8.1. OCDM/WDM-PON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 8.2. OFDM/WDM-PON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 9. XDM/TDM hybrid technologies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 9.1. OCDM/TDM-PON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 9.2. OFDM/TDM-PON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 10. Hybrid XDM/TDM/WDM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 11. NG-PON2 challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 11.1. Increase the capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 11.2. Extend the reach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 11.3. Power saving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 12. PON reliability aspects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 12.1. PON protection mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 12.2. PON security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 12.3. PON monitoring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 13. Future aspects of PON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 14. Discussion and future works. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 15. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 1. Introduction Passive Optical Networks (PONs) are a series of promising broadband access network technologies that offer enormous advantages when deployed in fiber to the home (FTTH) scenarios. The advantages include a point to multi-point architecture, high quality triple play service capabilities for data, voice and video, high speed internet access, and other services in a cost-effective manner (Ragheb and Fathallah, 2012). Over the past decade several PON architectures have been developed by the International Telecommunications Union (ITU) and the Institute of Electrical and Electronic Engineers (IEEE). The four main PON variations developed by the ITU and IEEE can be categorized into two groups. The first kind of architecture is based on Asynchronous Transfer Mode (ATM) and includes ATM PON (APON), Broadband PON (BPON) and Gigabit PON (GPON) and the second group consists of Ethernet PON (EPON). EPON and GPON are the most popular PON variations found in use today. A con￾ventional PON architecture is presented in Fig. 1 (Ragheb and Fathallah, 2012). In the figure, it can be seen that the PON archi￾tecture consists of an Optical Line Terminal (OLT), Optical Dis￾tribution Network (ODN), and Optical Network Units (ONU). The OLT is placed at the Central Office (CO) and connected to the splitters by fiber. The optical splitters connect to customer pre￾mises making PON a point to multi-point architecture (P2MP) (Ragheb and Fathallah, 2012). The EPON and the GPON standards have the same general principle in terms of framework and applications but their operation is different due to the implementation of the physical and data link layers (Olmos et al., 2011). EPON is defined by IEEE 802.3 and it is widely deployed in Asia whilst GPON is deployed in a number of other regions. GPON's requirements were defined by the Full Service Access Network (FSAN) group that was ratified as ITU-T G.984 and is implemented in North America, Europe, Middle East, and Australasia (Van Veen et al., 2011; Skubic et al., 2009). In this paper the advancement of PON technology is classified into three generations: the first generation (deployed PON), next generation stage 1 (NG-PON1), and next generation stage 2 (NG￾PON2). The evolution of the PON architectures and their corre￾sponding capacity features are shown in Fig. 2. The first generation of PON is based on Time Division Multiple Access (TDMA) and provides an EPON downstream rate of 1 Gbps and a GPON downstream rate of 2.4 Gbps. The NG-PON1 increases the data rate up to 10 Gbps for both standards (Biswas and Adak, 2011). There are two main scenarios to achieve an upgrade that are the upgrade from deployed EPON to XG-EPON and from deployed GPON to XG-GPON. An upgrade from deployed GPON to XG-EPON Fig. 1. PON architecture. Fig. 2. PON generations. 54 H.S. Abbas, M.A. Gregory / Journal of Network and Computer Applications 67 (2016) 53–74