Higher Capacity Passive Optical Network [HCPON] For FTTX Broadband Access Applications

Transcription

1 Higher Capacity Passive Optical Network [HCPON] For FTTX Broadband Access Applications Ram Krishna Dy. Director General (FLA) TEC New Delhi, DoT, Govt. of India. R. K. Siddhartha Director (FLA) TEC New Delhi, DoT, Govt. of India. Naveen Kumar Asstt. Director General (FLA) TEC New Delhi, DoT, Govt. of India. Abstract In this paper various aspects of fibre-based broadband passive optical access networks technologies have been presented. Various existing, present and future PON (Passive Optical Network) technologies have been compared and explained in this paper. The need of higher capacity PON, i.e. Next Generation passive optical network is developed on the basis of day to day emerging high data rate demands. Fibre-To-The-Home (FTTH) for broadband application may be considered an effective solution for higher capacity next generation access networks. PON based technologies are new for Indian telecom network and will grow extensively in near future for higher capacity applications, e.g. Triple Play services (telephony, data and TV etc.). Also High Capacity PON is a better option for network operators who want to supply a very large number of subscribers. Keywords Fibre-To-The-Home (FTTH), PON (Passive Optical Network), broadband, Next Generation Passive Optical Network (NGPON), Triple Play Services, Internet Protocol (IP), Gigabit passive optical network (GPON), Ethernet Passive Optical Network (EPON), Wavelength Division Multiplexing PON (WDM - PON). Page 1 of 16

2 1. Introduction The Internet has produced higher demands for broadband services, leading to extensive growth in Internet Protocol (IP) data traffic and putting pressure on service providers to upgrade their existing networks. Fibre-To-The-Home (FTTH) for broadband access applications may be considered as an effective solution for higher capacity access networks as optical fiber in telecommunications have huge capacity, small size, light in weight, very high bandwidth, and immunity to electromagnetic interference, etc. The PON based technologies are somewhat new for Indian telecom environment and will grow extensively in due course. The Gigabit passive optical network (GPON) and Ethernet Passive Optical Network (EPON) is considered to be a very attractive solution for implementing FTTX (Tiber To The Home/Business/Curb/Premises etc). The question will rise that what will be the next fiber access technology? Two technologies stand out in the industry would be 10G PON as a continuation of GPON and/or EPON & WDM-PON. Fig. 1: Typical PON topology 2. Passive Optical Network (PON) PON is a combination of network elements in an ODN (Optical Distribution Network) - based optical access network that includes an optical line termination (OLT) and multiple optical network units (ONU) and implements a particular coordinated suite of physical medium dependent layer, transmission convergence layer, and management protocols. The General schematic of passive optical network applications is shown below: Page 2 of 16

3 Fig. 2: General schematic of PON Architecture There are two important types of systems that make fiber-to-the-home (FTTH) broadband connections possible. These are active optical networks and passive optical networks. An active optical system uses electrically powered switching equipment, such as a router or a switch aggregator, to manage signal distribution and direct signals to specific customers. A passive optical network, on the other hand, does not include electrically powered switching equipment and instead uses optical splitters to separate and collect optical signals as they move through the network. A passive optical network shares fiber optic strands for portions of the network. Powered equipment is required only at the source and receiving ends of the signal. 3. PON Architecture PON has a point-to-multipoint tree topology that carries data frames between an optical line termination (OLT) and multiple optical network units (ONU) via a passive optical splitter. To share the upstream bandwidth among ONUs without collisions, robust and efficient medium access control is required. The various elements of PON architecture are shown in following diagram: Page 3 of 16

4 Fig. 4: Various components of PON Architecture Optical-access networks have been developed to remove the access-network bandwidth bottleneck. However, the current solutions do not adequately address the network economics to provide a truly cost-effective solution. Long-reach optical-access networks introduce a cost-effective solution by connecting the customer directly to the core network, bypassing the metro network, and, hence, removing significant cost. 4. Evolution of Passive Optical Networks In term of evolution, PON can be classify in to the following generations: Past Generation PONs (APON & BPON) Current Generation PONs (EPON & GPON) Next Generation PONs (10G EPON, XG-PON1 & XG-PON2) Future PONs (WDM - PON) 4.1 Past Generation PONs: APON and BPON Asynchronous Transfer Mode Passive Optical Networks (APONs) were developed in the mid 1990s through the work of the full-service access network (FSAN) initiative. FSAN Page 4 of 16

5 was a group of 20 large carriers that worked with their strategic equipment suppliers to agree upon a common broadband access system for the provisioning of both broadband and narrowband services. British Telecom organized the FSAN Coalition in 1995 to develop standards for designing the cheapest, fastest way to extend emerging high-speed services, such as Internet protocol (IP) data, video, and 10/100 Ethernet, over fiber to residential and business customers worldwide. At that time the two logical choices for protocol and physical plant were ATM and PON. ATM was thought to be suited for multiple protocols, PON because it is the most economical broadband optical solution. The APON format used by FSAN was accepted as an International Telecommunications Union (ITU) standard (ITU T Rec. G.983.x series). The ITU started releasing the G.983 series recommendations and amendments in These deal with the broadband optical access systems based on BPONs. Passive optical networks (PONs) address the last mile of the communications infrastructure between the service provider s CO, head end, or point of presence (POP) and business or residential customer locations. The APON format developed by the FSAN alliance was used as the basis for an international standard released by ITU-TS (Rec. G. 983.x), designated by BPON (Broadband PON). This standard supports more broadband services, including high-speed Ethernet and video distribution. After some initial deployment of BPON, the industry belatedly realized that a BPON ODN could not be incrementally upgraded to any next-generation technologies. 4.2 Current Generation PONs: EPON and GPON A PON system supporting transmission rates in excess of 1.25 Gbit/s in at least one direction, and implementing the suite of protocols specified in the IEEE 802.3ah is said to be EPON Ethernet Passive Optical Network and a PON system supporting transmission rates in excess of 2.5Gbit/s in at least one direction, and implementing the suite of protocols specified in the ITU-T G.984 series of recommendations is said to be Gigabit Passive Optical Network (G-PON). Therefore, The GPON and EPON are based upon ITU-T G.984.x and IEEE 802.3ah standards respectively. Page 5 of 16

6 The development of EPONs has been spearheaded by one or two visionary start-ups that feel that the APON standard is an inappropriate solution for the local loop because of its lack of video capabilities, its insufficient bandwidth, its complexity, and its expense. Also, as the move to fast Ethernet, gigabit Ethernet, and now 10-gigabit Ethernet picks up steam, these start-ups believe that EPONs will eliminate the need for conversion in the wide-area network (WAN)/LAN connection between ATM and IP protocols. 4.3 Next Generation PONs In the context of ITU-T standards development activity, a generic term referencing the PON system evolutionary beyond G-PON. The concept of NG-PON currently includes NG-PON1, where the ODN is maintained from BPON and G-PON, and NG-PON2, where a redefinition of the ODN is allowed from that defined in BPON and G-PON. In the optical access area, a set of three G.987.x series XG-PON Recommendations of ITU were prepared for consent, providing definitions, service requirements, and PMD specifications for passive optical network systems capable of 10 Gigabit per second transmission. There may be following technologies stand out in the industry for higher capacity solutions: - 10G PON, as a continuation of GPON (ITU G.987.x standards) and/or EPON (IEEE P802.3av standards) - WDM-PON, taking advantage of the wavelength domain Gigabit Passive Optical Network (XG-PON) A PON system supporting transmission rates in excess of 10Gbit/s in at least one direction, and implementing the suite of protocols specified in the ITU-T G.987 series of recommendations. Much effort on NG-PON is currently being done in prestandardization and standardization bodies FSAN/ITU-T for 10GPON. This has two variants: XG-PON1 It is a variant of XG-PON system that operates at a nominal line rate of 10 Gbit/s downstream and 2.5 Gbit/s upstream. It has asymmetrical downstream and upstream data Page 6 of 16

7 rate. XG-PON1 (G.987) is planned to be consented in ITU-T studied during period : Physical layer (PMD) October 2009 Transmission convergence (TC) and Management (OMCI) in June XG-PON2 It is a variant of XG-PON system that operates at a nominal line rate of 10 Gbit/s downstream and upstream. It is said to be 10G symmetrical data rate. The architecture of 10 GPON is shown in following figure. Fig 5: Architecture of 10 GPON To satisfy for more bandwidth requirement, the current 2.5 GPON system will be upgraded to support 10 Gbps in the downstream direction for FTTX solutions. The next generation 10G PON candidate will have a serial 2.5 Gbps wavelength in the upstream; in FSAN terms this corresponds to XG-PON1 & XG-PON2. The 10G GPON physical layer and optical components must be cost-effective while offering the same link-budget as GPON. Especially for the ONTs, due to their large numbers, it is critical to use low cost components G EPON Efforts on NG-PON are also currently being done in standardization for 10G EPON by IEEE P802.3av standards. 10G EPON provide physical layer specifications: Page 7 of 16

8 PRX 10G/1G Asymmetric - 10 Gbps downstream/1 Gbps upstream, single SM fiber PR 10G/10G Symmetric - 10 Gbps downstream/10 Gbps upstream, single SM fiber Define up to 3 optical power budgets that support split ratios of 1:16 and 1:32, and distances of at least 10 and at least 20 km. 4.4 Future PON - Wavelength Division Multiplexing PON (WDM - PON) It is unclear when and exactly how WDM-PON will be standardized, possibly 1-2 years after XG-PON. DWDM (Digital Wavelength Division Multiplexing) based access is a general transport technology where different services and networks can co-exist on the same fiber by using different wavelengths. Although WDM-PON standards are still being developed, manufacturers and service providers anticipate that it will use the same physical architecture as today s PON systems, with an OLT feeding 32 ONTs. The difference is that each ONT will be fed by a separate wavelength, enabling each customer to get higher bandwidth. WDM-PON expands on that idea by increasing the number of wavelengths in the fiber from the OLT to a neighborhood node. This WDM-PON is known as a promising technology for future access network. The performance of a novel 2.5 Gbps WDM-PON Network architecture which employs new PON Optical Add/Drop Multiplexer (OADM), in order to support high coverage in unlimited scaling. Based on the architecture, higher installation and maintenance costs can be reduced, and the access network design can support symmetric transmission rate 10 Gbps for distance up to 30 km. WDM-PON offers an alternative to the GPON time-shared transmission scheme by having each ONT transmitting and receiving at a specific wavelength. Thus, the main Page 8 of 16

9 difference between WDM-PON and the use of wavelengths on GPON (for overlaying several GPONs and/or 10G GPONs) is that WDM-PON may not use the GPON protocol but can use for example point-to-point Gigabit Ethernet. Fig. 6: WDM PON Architecture In the future the end customer will be demanding high definition TV (HDTV). Although many of us do not realize it, daily activities that are now considered trivial consume a significant amount of bandwidth. PONs solutions must support data, voice and video delivery in efficient manner. The most demanding of these applications is the use of video especially high-definition television (HDTV) followed by standard-definition television (SDTV). to support multi-resolution streams over Passive Optical Networks (PONs). The benefits of WDM-PON include: (Physical layer) un-contended bandwidth similar to point-to-point fiber, i.e. no bandwidth scheduling is needed as in GPON. Effective use of fiber - up to 64 subscribers/fiber (similar to GPON) Page 9 of 16

10 Longer reach is possible, using the low-loss AWG in contrast to the high-loss power splitter needed for GPON. Using the 28 db link-budget of Table 1 and assuming a 64-way split, a WDM-PON at 1550 nm could reach >80 km compared to around 16 km for a GPON. Physical separation of subscriber signals. The main obstacle to WDM-PON is the cost, since the transmitters need to emit at a specified wavelength. This is especially critical for the subscriber units (ONTs) since this cost directly affects each subscriber line. At the CO side, the cost of the multi-wavelength signal can be lowered by optical integration. 4.5 Comparison of various PON technologies The basic difference among the various PON technologies and generation is summarized in the following table: PON Technology Standard Maximum Bandwidth Maximum Downstream Line Rate Maximum Upstream Line Rate Downstream wavelength Upstream wavelength Traffic Modes A/BPON ITU G.983/ FSAN EPON (GEPON) IEEE 802.3ah GPON 10 GEPON 10 G PON (XG-PON1/ XG-PON2) ITU G.984 IEEE P802.3av 622 Mb/s 1.2 Gb/s 2.4 Gb/s Gb/s 622 Mbps 1.2 Gbps 2.4 Gbps IP; 2.4 Gbps, Broadcast; 5 Gb/s Ondemand; 2.5 Gb/s 155/622 Mbps 1490 and 1550 nm ITU-T G.987/ FSAN 2.5 Gb/s & 10 Gb/s WDM PON ITU G Gb/s per channel 10 Gbit/s 1-10 Gbit/s per channel 1.2 Gbps 1.2 Gbps 2.5 Gbps 2.5 Gb/s 1-10 Gbit/s per channel 1550 nm 1490 and 1550 nm 1550 nm 1577 nm Individual wavelength/ channel 1310 nm 1310 nm 1310 nm 1310 nm 1270 nm Individual wavelength/ channel ATM Ethernet ATM Ethernet or TDM Ethernet GEM Protocol Independent Video RF/IP RF/IP RF/IP RF/IP RF/IP 1550 nm overlay/ IP Max PON Page 10 of 16

11 Splits Max Distance 20 Km 20 Km 60 Km 10 Km 20 Km 20 Km Average > 100 > 100 Mb/s 1-10 Gbit/s Bandwidth per User Mbit/s Mbit/s Mbit/s Mbit/s Cost Low Low Medium High High Very high Table Benefits of Higher Capacity NG PON Technologies PON are simpler, more efficient, and less expensive than alternate multiservice access solutions. Key advantages of NG PONs include the following: Higher bandwidth: up to 10 Gbps or more Lower costs: lower up-front capital equipment and ongoing operational costs More revenue: broad range of flexible service offerings means higher revenues Higher Splitting Ratio Higher distance 5.1 Higher Bandwidth NG PONs provides a number of benefits: More subscribers per PON More bandwidth per subscriber Higher split counts Video capabilities Better QoS Cost - reduction applications 5.2 Lower Costs NGPON systems are riding the steep price/performance curve of optical and Ethernet components. As a result, NGPONs offers the features and functionality of fiber-optic equipment at price points that are comparable to DSL and copper T1s. Further cost reductions are achieved by the simpler architecture, more efficient operations, and lower maintenance needs of PON. NGPONs delivers the following cost reduction opportunities: Page 11 of 16

12 Eliminate complex and expensive ATM and SONET elements and dramatically simplify network architecture Long-lived passive optical components reduce outside plant maintenance Standard Ethernet interfaces eliminate the need for additional DSL or cable modems No electronics in outside plant reduces need for costly powering and right-of-way space 5.3 More Revenue Revenue opportunities from NG PONs include: Support for legacy TDM, ATM, and SONET services Delivery of new gigabit Ethernet, fast Ethernet, IP multicast, and dedicated wavelength services Provisioning of bandwidth in scalable 64 kbps increments up to 10 Gbps Tailoring of services to customer needs with guaranteed SLAs Quick response to customer needs with flexible provisioning and rapid service reconfiguration. 5.4 Higher Splitting Ratio The splitting ration may be more than 1: Higher distance The distance may be extended upto 100 km. 5.6 Cost - Reduction Applications NG PONs offer service providers unparalleled opportunities to reduce the cost of installing, managing, and delivering existing service offerings. For example, NG PONs do the following: Replace active electronic components with less expensive passive optical couplers that are simpler, easier to maintain, and longer lived Conserve fiber and port space in the central office (CO) Page 12 of 16

13 Share the cost of expensive active electronic components and lasers over many subscribers Deliver more services per fiber and slash the cost per megabit Promise long-term cost-reduction opportunities based on the high volume and steep price/performance curve of Ethernet components Save the cost of truck rolls because bandwidth allocation can be done remotely 6. Conclusions In this paper an overview of the differences between Past Generation PON, Current Generation PON, NG - PON and Future generation 10G PON and WDM-PON has been presented.. 10GPON has many advantages in terms of standardization, maturity, cost and power consumption. In respect of management, point-to-point systems are typically easier to maintain than point-to-multipoint systems. Thus, the trend is that 10GPON is envisioned for residential applications. However, for longer distances e.g. 100 km or more, the solutions are needed with remote monitoring from the CO to the end-user. WDM-PON can offer higher bandwidth and reach and additional advantages with respect to security as WDM-PON with its dedicated wavelength channel per subscriber is often considered to be more secure. It is somewhat difficult to migrate to WDM-PON and 10 Gbps or more capacity because TDM used in current system have limitations over huge bandwidth of the optical fibers and therefore will restrict to meet increasing demands for higher bandwidth by future network applications. As today however, Triply Play services (telephony, data and TV down one single line) are transmitted to the subscriber, therefore QoS applies more than ever. The PON architecture is proving to be a cost-efficient way to deliver converged voice, video and high-speed data services to the home or business. One of the most distinctive features of the Fiber Path PON system is its ability to support both upstream and downstream data transmissions at equally fast speeds - speeds. The more future work is required on high capacity media streaming services over PON architecture, which enhances the client Quality of Services and security. Page 13 of 16

14 References 1. ADC Krone The Book on Next Gen Networks The essential information you need to know when deploying FTTX, from the central office to the outside plant to the customer premises. 2. Alex Vukovic, Khaled Maamoun, Heng Hua, Michel Savoie Performance Characterization of PON Technologies, Broadband Applications and Optical Networks, Communications Research Centre (CRC), Ottawa, ON, Canada, K2H 8S2. 3. Broadband Forum Technical report TR-156 Using GPON Access in the context of TR- 101, Issue 1, December Ericsson AB 2008 Full Service Broadband with GPON Rev A FTTxtra Tutorial, 10G GPON web 6. Hilbk U., Hermes T., Saniter J. and Westphal F. J., High-capacity upgrade of a PON by means of wavelength-routers and WDM techniques WDM Technology and Applications (Digest No. 1997/036), IEE Colloquium on Volume, Issue, 6 Feb 1997 Page(s) 3/1 to 3/5. 7. Kyeong Soo Kim, On The Evolution of PON-Based FTTH Solutions Advanced System Technology, STMicroelectronics Stanford Networking Research Center, Packard Building, Room 073, Stanford, CA Shea D.P. and Mitchell J.E. A 10-Gb/s 1024-Way-Split 100-km Long-Reach Optical- Access Network Lightwave Technology, Journal of Volume 25, Issue 3, March 2007 Page 685 to Sami Lallukka & Pertti Raatikainen VTT PUBLICATIONS 597 Passive Optical Networks - Transport concepts ESPOO The International Engineering Consortium web ProForum Tutorial Ethernet passive optical networks. 11. The Metro Ethernet Forum 2005 Tutorial Ethernet Passive Optical Network (EPON). 12. Wen-Kang Jia and Yaw-Chung Chen Performance Evaluation of Ethernet Frame Burst Mode in EPON Downstream Link ETRI Journal, Volume 30, Number 2, April Page 14 of 16

15 Glossary APON Asynchronous Transfer Mode Passive Optical Network ATM Asynchronous Transfer Mode BPON Broadband PON CATV Cable Television CO Central Office CPE Customer-Premises equipment CSMA/CD Carrier Sense Multiple Access with Collision Detection DHCP Dynamic Host Configuration Protocol DNS Domain Name System DS Down-Stream DS1 Digital Signal 1 DSL Digital Subscriber Line DSLAM DSL Access Multiplexer DWDM Digital Wavelength Division Multiplexing E1 E-carrier level 1 EFM Ethernet in the First Mile EPON Ethernet PON FMC Fixed Mobil Convergence FSAN Full Service Access Network FTTB Fiber To The Building FTTC Fiber To The Curb, FTTH Fiber To The Home FTTN Fiber-To-The-Neighborhood FTTN Fiber To the Node GPON Gigabit-capable PON HDTV High Definition Television HSPA High-Speed Packet Access IEEE Institute of Electrical and Electronics Engineers IP Internet Protocol IPTV IP Television ITU-T International Telecommunication Union - Telecommunication Standardization Sector Page 15 of 16

16 LTE NAT NGA NG-PON NNI ODN OLT ONT ONU OPEX PON POTS RF SBU SDH SONET SFU STB STP STS TDM UNI US VDSL VLAN VoD VoIP VPN WBF WDM XG-PON Long-Term Evolution Network Address Translation Next Generation Architecture Next Generation PON Network-Network Interface Optical Distribution Network Optical Line Termination Optical Network Termination Optical Network Unit Operational EXPenditure Passive Optical network Plain Old Telephony System Radio Frequency Single Business Unit Synchronous Digital Hierarchy Synchronous Optical Network Single Family Unit Set Top Box Signalling Transfer Point Synchronous Transfer Mode Time Division Multiplexing User-Network Interface Up-Stream Very High-speed Digital Subscriber Line Virtual LAN Video on Demand Voice Over Internet Protocol Virtual Private Network Wavelength Blocking Filter Wavelength Division Multiplexing 10 Gbps GPON Page 16 of 16