OPTICAL ACCESS NETWORK’s (OAN’s) 1. History & Reason of Existence The experience with active and passive optical networks have been gained within ten years of experience with active and passive optical networks .These networks has different features that causes both of them to have advantages and disadvantages. Fiber optics network can be laid directly to households (Fiber to Home [FTTH]) by using direct networks which include the main types of network that are Passive optical networks (PON) & Active optical networks (AON). In the mid-1990s, the first large-scale PON installations were commissioned in Japan. In many other parts of the world, FTTH concepts were a long way off. The existence of the internet and the need of better bandwidth has a great attract to customers but the technology was much too expensive in any case ,so earlier customers didn’t believe it’s necessary to have a higher bandwidth capacity until the beginning of the new millennium. The subsequent escalation of bandwidth, fuelled by the availability of broadband DSL connections via copper wire, has turned the internet and associated services into an unparalleled success story. Today, considering all the new services like high definition IPTV, online gaming and remote surveillance, ICT service providers are well advised to seek access network solutions with even more bandwidth for the post-DSL era. However, due to the physical properties of copper wire in the last mile, VDSL2 has reached its limits, even if technology called DSM (Dynamic Spectrum Management) is being developed to boost the transmission capacity on copper. Communication solutions like WiMAX, or LTE in mobile telephony, reach the limits of their capabilities even more quickly because of poorer physical transmission properties (in comparison with copper). To date, the only solution for seemingly infinite bandwidths has been the optical wave guide, also called Fiber optics. 2. Basic Facts The main difference between PON & AON is that PON uses passive splitters. The splitter is basically a kind of that distributes the optical signal for the subscriber line to fiber optic routes without any electrical current (which is why it is called passive).
receive. Synchronization of the right user time slot is carried out in the ONT. 2.2 Active Optical Networks (AONs) AON is a point-to-point network structure (PTP), i.e. each subscriber has their own fiber optic line that is terminated on an optical concentrator (Access Node [AN]). This type of AN can be designed differently, depending on specific locations. Usually Metro IP-Edge routers or Access Nodes (MSANs) with optical Ethernet interfaces are used in this case. The Fiber optics can be terminated by an ONT here too, but also by any Ethernet switch or IP router with an optical uplink interface. If the last mile to the subscriber is to be bridged using copper wire, DSLAMs or other MSANs are used. When MSANs are used, both copper and optical lines can be used for the last mile from the same access node. 3. AON vs. PON 3.1. Bandwidth The trend towards increasing bandwidth continues unabated. Due to the launch of TV-over-IP (IPTV) there is no sign of the increase in bandwidth tailing off, in fact quite the opposite. Because of the recent launch of (HDTV) and other technically complex services Such as online gaming, network operators are being encourage to outdo one another by providing more and more bandwidth. The following table compares PON and AON transmission bandwidth.
Not all QoS aspects can be responded to with bandwidth and neither PON nor AON can really provide unlimited bandwidth. Nowadays, the Triple Play offerings, implemented via copper wire often consist of two television channels with standard resolution (SDTV), a Internet connection (>3 Mbps) and at least one POTS or ISDN telephone connection. The current state of the art is that network operators are planning approx. 15 Mbps downlink capacity. In the future the end customer will be demanding high definition TV (HDTV). Two simultaneous TV channels will mean an unacceptable restriction for a family of four in the long term. Furthermore, currently ADSL 16 Mbps Internet access is already being marketed to private customers and including n telephone lines. Online gaming – in the Far East popular for years – is also looking promising in Europe. In this case, top rates of 50 Mbps per subscriber line could easily be reached. Today, standard VDSL2 access would not be able to cope. The scenario described above indicates what the private consumer will look like in the near future. If such a scenario appears exaggerated, we only have to recall the situation 10 years ago when modern end customers still used 56 kbps dial-up modems to read emails, for sending faxes and for home banking. In comparison to today’ s standard 3.5 Mbps ADSL connection, the bandwidth has increased 62-fold! Special requirements from business customers, or demands for the backhaul of server connections or high performance IT applications would easily exceed these quality specifications and require even greater high quality performance. 3.3. Business case aspects Using fiber optic cable promises virtually unlimited bandwidths, however the network operator only ever has just the copper wire line in the last mile. That means that if the DSL technology is no longer adequate, new optical cables must always be laid. But when making a comparison between POS and AOS from different Investment views it can be noticed that PON Vs.AON in Cost AON PON Low High Cost of (active components) High Low Costs of (passive components and infrastructure) High LOW Network rollout costs High Low