Fiber to the home. Why? How? And where to? GROUP: 7

Transcription

1 Fiber to the home Why? How? And where to? GROUP: 7 We review briefly the various FTTH architecture options. In addition the trade-offs, challenges and new trends. 1 P a g e

2 Contents I. Introduction a. Overview b. Advantages of FTTH c. Disadvantages of FTTH II. Fiber access network architectures a. Point-to-point architecture b. Point-to-multi-point architecture Active optical network (AON) Passive optical network (PON) III. Multiple access techniques in PONs a. Time division multiple access (TDMA) b. Wavelength division multiple access (WDMA) c. Subcarrier multiple access (SCMA) d. Optical code division multiple access (OCDMA) IV. Next Generation PONs (NG-PONs) a. HPON (hybrid passive optical networks) b. Coherent PONs V. Optical fiber specification. VI. Radio over Fiber(ROF) VII. The growth in FTTH VIII. The future work IX. Conclusion X. References 2 P a g e

3 I. Introduction a. Overview FTTH is using optical fiber in the delivery of a communications signal from the operator s switching equipment all the way to a home or business. Enormous improvements in the bandwidth that can be provided to consumers are enabled through connecting homes directly to fiber optic cable. Two-way transmission speeds of up to 100 megabits per second are provided by current fiber optic technology. Moreover, ongoing improvements in fiber optic equipment are constantly increasing available bandwidth without having to change the fiber, while cable modem and DSL providers are struggling to increase the bandwidth in their technologies. That s why fiber networks are said to be future proof (The term "future-proof" refers to the ability of something to continue to be of value into the distant future; which means that the item does not become obsolete. ). FTTH has been developed because of: The desire for higher speeds in telephony beside plain old telephone service (POTS), and to cope with next generation voice services such as Voice over IP and IP telephony. An increase in services offered by application service providers (ASPs), beside deregulation and pending Federal Communications Commission (FCC) rulings. This raised the competition in the market due to the growing number of competitive local-exchange carriers (CLECs). b. Advantages of FTTH: It is a single fiber to the end user, which provides revenue-generating services with industry standard user interfaces, including voice, high-speed data, and analog or digital CATV, DBS, and video on demand. It features low-power consumption and local battery backup. It is a passive network, so there are no active components from the CO to the end user. This results in minimizing the network maintenance cost and requirements, as well as eliminating the need for a DC power network in an observable way. It is reliable, scalable, and secure. c. Disadvantages of FTTH: Its high deployment cost. Power cannot be supplied to a home along with the signal on the fiber optic lines. Fiber optic cables are susceptible to physical damage. Special test equipment is often required. 3 P a g e

4 II. FIBER ACCESS NETWORK ARCHITECTURES: Here we have three types of architectures: Point-to-point, Passive and Active. Shown in the table below: [6][7] I. Point-to-point (P2P) Each fiber leaving the central office goes to exactly one customer. It has a core switch at the central office, which connects over optical fiber cables to an aggregation switch at the distribution points. These locations are typically your street corners, etc. The aggregation switches have many fiber ports and each port will directly connect to an ONT (Optical Network Termination) placed at the residential localities using fiber cables. a. passive optical network (PON) (point to multipoint ) The same as (P2P) except in the distribution points. Instead of the active switches with fiber ports, passive splitters are used. These splitters do not require any power supply and they can divide an optical signal into 32, 64 or even 128 shared connections. The same signal is transmitted to all the houses beyond the splitter, but each ONT in each house knows how to decipher the information meant only for itself. Of course, the ONTs used in P2P are different from the ones used in PON. Also, the total bandwidth is shared between all these shared connections. It has distance limitation of 10-20km from the CO b. Active optical network (AON) (Point to multipoint ) It looks very similar to PON but instead of having passive splitters,it uses environmentally hardened Ethernet electronics to provide fiber access aggregation (switches ) Instead of sharing BW between subscribers each end user is provided a dedicated pipe that provides full bi-directional BW AON has distance limitation of 80 km from the CO, the number of subscribers is limited by the switched employed. III. MULTIPLE ACCESS TECHNIQUES IN PONS: A technique that is used for sharing a limited resource amongst a number of users. In a PON access system, the shared resource is the communication bandwidth. Four major categories of multiple access techniques for fiber access networks have been developed: Time division multiple access (TDMA). Wavelength division multiple access (WDMA). Subcarrier multiple access (SCMA). Optical code division multiple access (OCDMA). 4 P a g e

5 a. Time Division Multiple Access (TDMA): [6] It is a multiplexing technique that allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium while using only a part of its channel capacity. In the basic method of Operation for downstream distribution on one wavelength of light from OLT to ONU/ONT, all customers receive the same data. The ONU recognizes data targeted at each user, while the upstream from ONU to OLT, a time division multiplex (TDM) technique is used where each user is assigned a timeslot on a different wavelength of light. The upstream transmissions occur at random as a user needs to send data. The system assigns a slot as needed. Because the TDM method involves multiple users on a single transmission, the upstream data rate is always slower than the downstream rate. b. Wavelength division multiple access (WDMA): WDM-PON is a key component in next generation access, since TDM-based systems cannot meet some users demands for bandwidth due the increasing requirements for bandwidth scalability, quality of service, and support of the emerging traffic patterns required by digital services like highquality streaming video and audio, virtual reality, and new graphic-intensive web interfaces, so it is needed to emigrate to systems that can support this demand. WDM PONs are a good way to upgrade existing PON topologies. Main principle of WDM PON: [9][12] WDM-PON is a passive optical networking approach. A WDM-PON design is a perfect mix between the pointto-point and the GPON topologies, that it can be used to separate optical-network units (ONUs) into several virtual point-to-point connections over the same physical infrastructure, a feature that enables efficient use of fiber compared to point-to-point Ethernet and offers lower latency than TDM-based approaches. The central office (CO) contains multiple transceivers at different wavelengths with each output wavelength creating a dedicated channel for a particular user by 5 P a g e

6 passing through a wavelength selective element at the remote node (RN), which enlarges the potential bandwidth per user excessively. Wavelength selection can also be achieved by filtering at the user. One can allocate a Gigabit or a 10 Gigabit connection to each customer-premises equipment (CPE) quite easily. The upstream connection similarly utilizes a dedicated wavelength channel. Advantages: A notable advantage of this approach is the combination of high capacity per user, high security, and longer optical reach. Low latency. Low jitters. The same wavelength channel may be used for upstream communication as well as for downstream simultaneously. By following certain design rules during the installation of the WDM-PON system, it's possible to allow step-wise channel upgrades to higher bit rates when the demand arises. These rules ensure that channel OSNR requirements will be met in the presence of reflections and that inter-channel crosstalk is avoided. The result is an open and flexible access network that can support many applications and services over the same infrastructure. Challenges and possible solutions: It is not everything nice and simple. The present major drawbacks of WDM PONs at present are related to cost of the required components in addition to power consumption as follows: For upstream communication, every ONU needs a wavelength-specific laser diode, which increases costs, and complicates maintenance. Alternatively, universal colorless ONU concepts may be deployed which can support all wavelength channels needed, and thus lower costs. Such a concept may use a light source with a broad spectrum at the ONU, of which the in-field multiplexer makes spectral slicing by cutting out the appropriate part of the spectrum. This approach may yield a reduced effective optical power available from the ONU and thus limits the reach of the system. However, the limitation in power due to Rayleigh backscattering and other reflections from connectors and splices in the fiber link can be alleviated by using a reflective semiconductor optical amplifier (RSOA). At the remote node, a wavelength multiplexer to separate the different wavelengths to each subscriber is required and those are not cheap devices at present. Although they have improved a lot during the last years and now they do not have thermal stability issues as in the past, their cost is still higher than traditional power splitters. [12] The OLT is a technologically equivalent to a point-to-point and therefore the number of optical interfaces is quite high (one per subscriber). This makes that the power requirements at this end are higher than in TDM PON technologies. [12] Where can WDM-PON go next? [10][11] Current research focuses on how to scale WDM-PON toward higher bit rates and longer reach. Forward error correction is a key technology for scaling the current generation of WDM-PON technology to higher bit rates, longer reach, tighter channel spacing, or a combination thereof. Another more interesting application is to enable node consolidation. That means operators can reduce opex by closing down portions of their central offices; at the same time, this goal requires the optical signals to bridge longer distances than what is typical of the access networks of today. 6 P a g e

7 Increase the split ratio up to 128 or more, reducing the cost per subscriber. Extend the geographical reach to a minimum of 100 Km. c. Sub-Carrier Multiplexing (SCM): [3][6] It is a method for multiplexing many different communications signals so that they can be transmitted along a single optical fiber. SCM follows a different approach compared to WDM. In WDM an optical carrier is modulated with a baseband signal of typically hundreds of Mbit/s. In an SCMA, the baseband data is first modulated on a GHz wide subcarrier, then it is modulated on the optical carrier. Advantages: Each frequency band constitutes an independent communication channel from an ONU to the OLT and thus may carry a signal in a format different from that in other channel (e.g. one channel carry digital data signal and other one an analog video signal Disadvantages: The frequency difference between wavelengths may result in beat noise products due to optical beating at the photo-detector in the receiver. d.optical Code Division Multiple Access (OCDMA): [13][14][15] An essential part of the digital communication system now days for long haul, high speed networks. The biggest challenge with OCDMA system is to maintain the performance of the system and offer high bandwidth in case of higher number of users at minimum cost. It is based on spread-spectrum techniques, which have been widely used in mobile-satellite and digital-cellular communication systems. The concept is to spread the energy of the optical signal over a frequency band that is much wider than the minimum bandwidth required to send the information. In OCDMA, each ONU may use a specific optical code word to distinguish itself from the others. Two versions may be discerned: OCDMA using time-sliced code words, and OCDMA using spectrum-sliced code words. Advantages: Support of variable bit rates. Security against unauthorized users. Disadvantages: - As the number of users increase the BER error rate degrades because the effect of MAI increases. So, there is a limitation in number of users, as the number of users increase SNR decrease and probability of error increases. - Error corrections Forward error correction is costly and unusable in O-CDMA because the speed for carrying the information in electrical cables and optical fiber is not same. - Encoding and decoding. The encoding broadband and decoding hardware is expensive for OCDMA. For 7 P a g e

8 generation a large number of wavelengths, the broadband LED is the cheapest option, but the light generated may not have a high enough intensity for OCDMA applications both the laser diode array and the EDFA options have the required power but are currently expensive. I. TDMA PON system : [16][17] The currently deployed PON systems are TDM PON systems depending on TDMA, which include ATM PON (APON), Broadband PON (BPON), Ethernet PON (EPON), Gigabit PON (GPON), 10G EPON, and Next-generation PON (NG-PON). Over the years, various PON standards have been developed. In the late 1990s, the International Telecommunications Union (ITU) created: APON: The first type of PON standard, based on ATM (Asynchronous Transfer Mode) which is a protocol in telecom networking BPON: Coming after APON, it supports other topology WDM (will be discussed later), higher upstream bandwidth. GPON: Based on previous PON types but supports higher data rates and increased security. GPON uses optical wavelength division multiplexing (WDM) so a single fiber can be used for both downstream and upstream data. In GPON networks, up to 64 ONTs can share one fiber connection to the OLT. This makes GPON an attractive option for service providers wanting to replace copper networks with fiber. EPON: It uses WDM with the same optical frequencies as GPON and TDMA. EPON is part of IEEE standard Ethernet for 1/1 Gbit/s,10/1 Gbit/s, and 10/10 Gbit/s. With over 40 million installed EPON ports, it is the most widely deployed PON technology worldwide. 8 P a g e

9 II. Next Generation PONs (NG-PONs): We aim to achieve higher bitrate, long reach and lower power consumption, and here are two possible solutions: a. HPON (hybrid passive optical networks): [18] it is the intermediate step between TDM and WDM-PON networks. Instead of using only one wavelength to provision bandwidth in upstream and downstream as TDM PON does, hybrid WDM/TDM PON increases the number of working wavelengths in each stream to exploit the high bandwidth of optical fibers. On the other hand, provides a more flexible and cost-effective access network solution. The major objectives of HPON are: Backward compatibility: To guarantee the coexistence of current-generation (TDM-PON) and nextgeneration (WDMPON) optical access systems in the same network Easy upgradeability: To provide smooth migration paths from TDM-PON to WDM-PON without drastically changing the fiber infrastructure. b. Coherent PONs [19] :both OLT and ONU select wavelengths according to the principle of coherent detection. This means the OLT and ONU start coherent reception only when the locallyoscillated light and signal light meet the coherent conditions of frequency, phase, and polarization. In this way, the OLT and ONU can select their wavelengths by dynamically changing their locally-oscillated light frequencies. It introduces improved optical budget and channel density. However it is not cheap. Such a technology is more in the status of research and lab demo. Concerns to cost and complexity challenge its applicability in the access network. Latest research results: for Self-coherent reflective PON (shown in fig.) they successfully demonstrated a long-reach fiber-loopback system of over 100 km, so we can realize a long-reach WDM PON with high-split ratio. 9 P a g e

10 III. Optical fiber specifications: [20] IV. Radio over Fiber(ROF): [21] The concept of ROF means to transport information over optical fiber by modulating the light with the radio signal. In other words, to use of optical fiber links to distribute RF (radio frequency) signals from BS to Remote Antenna Unit (RAU). In the communication system, RF signal processing functions such as frequency up-conversion, carrier modulation, and multiplexing, is performed into the antenna. ROF makes it possible to centralize the RF signal processing function in one head end, then to use optical fiber, which offers low signal loss between 0.3 db/km for 1550nm and 0.5 db/km for 1310 nm wavelength. It distributes the RF signals to the RAUs as shown in the following 10 P a g e

11 Architecture of ROF: There are three categories depending on the frequency range of the radio signal to be transported: a) In RF-over-fiber architecture, a data-carrying RF signal with a high frequency (greater than 10 GHz) is imposed on a light wave signal before being transported over the optical link. Therefore, wireless signals are optically distributed to base stations directly at high frequencies and converted from the optical to electrical domain at the base stations before being amplified and radiated by an antenna.so, no frequency up down conversion is required at the various base stations, thereby resulting in simple and rather cost-effective implementation is enabled at the base stations. b) In IF-over-fiber architecture, an IF (intermediate frequency) radio signal with a lower frequency (less than 10GHz) is used for modulating light before being transported over the optical link. Therefore, before radiation through the air, the signal must be up-converted to RF at the base station. Benefits of ROF: Combining the huge bandwidth of fiber with the mobility offered by wireless communication makes fiber wireless networks an attractive access. By transporting the radio signals over fiber, the antenna sites of broadband wireless systems can be significantly simplified and thus system costs be reduced, whereas also more sophisticated signal processing (for e.g., antenna diversity systems) is facilitated. In Radio-over-fiber techniques, augmented with optical routing to accommodate dynamically the hot spots, may provide the best match of the ultimate capacity of fiber with the user freedom of wireless. As it s known that optical fibers offer enormous bandwidth where there are three main transmission windows, which offer low attenuation, namely the 850 nm, 1310 nm, and 1550 nm wavelengths. For a SMF optical fiber, the combined bandwidth of the three windows is in the excess of 50 THz. Other benefits are: i. Low Attenuation Loss: signals transmitted on optical fiber attenuate much less than through other media, especially when compared to wireless medium. By using optical fiber, the signal will travel further, reducing the need of repeaters ii. Easy Installation and Maintenance: In ROF systems, complex and expensive equipment iii. iv. are kept at the head end. Reduced Power Consumption. Immunity to Radio Frequency Interference 11 P a g e

12 V. The growth in FTTH: [22][23] *As mentioned in a Statement by Dr. Suleiman Al Hedaithy, Chairman, Fibre to the Home Council Middle East & North Africa (FTTH Council MENA) : The technology of fiber to the home continues to grow worldwide. The number of countries where FTTH broadband connections were making big gains continued to grow in number. In the MENA region more than 1.5 million households are using FTTH services, with the highest take up rate of 43% in China alone expects to have fiber broadband to nearly 200 million households by 2015 and to 300 million by UAE was ranked no. 1 in FTTH penetration rate globally, for the past two consecutive years. In 2013, there were million FTTH accesses in the world according to the Europe FTTH council. Country(in2013) Asia USA/Canada Russia & neighbors Europe Middle East Latin America Total No. Number(million) VI. The future work: [23] The future is definitely FTTH which will bring people to their connected and smart homes.homes with smart appliances, homes with next-generation entertainment, homes with smart meter and energy, homes with monitoring and security systems. A Sustainable Future and better quality of life are enabled by FTTH. FTTH enables users to benefit from applications, content and services based on ultra-high speed broadband. The highest impact, however, will be in rural areas. VII. Conclusion The future of FTTH is on its way but still needs more research for the mass deployment. However, a combination of WDM-PONs and NG-PONs might dominate the remote future. * During World Telecommunication Development Conference P a g e

13 VIII. References: [1] samenacouncil.org (samena telecommunications council ) [2]The FTTH council site [3] Wikipedia site [4] How Stuff Works site [5] fiber to the home Europe council [6] T. Koonen, H. van den Boom, and G.-D. Khoe BBroadband access and in-house networksvextending the capabilities of multimode fiber networks, presented at the ECOC 2003, Rimini, Italy. [7] N. J. Frigo, P. P. Iannone, and K. C Reichmann, BSpectral slicing in WDM passive optical networks for local access, in Proc ECOC 1998 [8] Fiber to the Home/Fiber to the Premises. Ton Koonen, Senior Member IEEE. [9] High Performance, Low Cost, Colorless ONU for WDM-PON Ryohei Urata, Cedric Lam, Hong Liu, and Chris Johnson. [10] Next Generation Optical Access Networks: from TDM to WDM. Ll. Gutierrez1, P. Garfias1, M. De Andrade1, C. Cervelló-Pastor1 and S. Sallent2 [11] WDM-PON is a key component in next generation access. March 7, Articles of lightwaveonline.com [12] WDM PON PRINCIPLES Posted, Carlos Bock, Articles of ftthexperience.wordpress.com [13]Ahmed Nabih Zaki Rashed1 ; Mohamed M. Zahra2 ; Mohamed Yassin3 ; Ismail A. Abd El-Aziz4 ; Shreen A.El- Bheiry5 Transmission Analysis of Optical Code Division Multiple Access (OCDMA) Communication Systems in the Presence of Noise in Local Area Network Applications International Journal of Basic and Applied Science, Vol 01, No. 04, April 2013, pp [14]Ton Koonen, Senior Member IEEE Fiber to the Home/Fiber to the Premises: What, Where, and When? The solution may be direct fiber to each home, or shared multiplexed fiber links, or hybrid fiber-copper, -coax, or, perhaps, radio-over-fiber. Vol. 94, /$20.00 _2006 IEEE No. 5, May 2006 Proceedings of the IEEE [15]FARAH HAYATI BINTI CHE LAH DEVELOPMENT OF NEW OCDMA ENCODER AND DECODER MODULES APERLIS 2007 [16] The difference between EPON & GPON, Lou Frenzel, Jan 6,2014, an article on ectronicdesign.com [17]FTTH PON types, an article on The Fiber Optic Association (FOA)site [18] SUCCESS-HPON A next-generation optical access architecture for smooth migration from TDM-PO, Sep 3, 2011 on wenku.baidu.com [19] Next-Generation PON Evolution - Huawei [20] TECHNICAL SPECIFICATIONS FOR FTTH CABLE, SUZHOU SPEED OPTIC COMMUNICATION EQUIPMENT CO. DOC NO. : Q/FOC-J [21] Radio over Fiber: Future Technology of Communication Ajay Kumar Vyas1, Dr. Navneet Agrawal2, July August 2012 [22] FTTH in the World, 03/06/2014. An article on teleco.com [23] World Telecommunication Development Conference 2014, Statement by Dr. Suleiman Al Hedaithy, Chairman, Fibre to the Home Council Middle East & North Africa (FTTH Council MENA) posted on 13 P a g e