self healing optical access network

Editor's Notes

• #4: Active optical networks rely on some sort of electrically powered equipment in Optical Distribution Network(ONU) to distribute the signal, such as a switch or router. Normally, optical signals need O-E-O transformation in ONU. Each signal leaving the central office is directed only to the customer for which it is intended.Incoming signals from the customers avoid colliding at the intersection because the powered equipment there provides bufferingA passive optical network (PON) is a point-to-multipoint, fiber to the premises network architecture in which unpowered optical splitters are used to enable a single optical fiber to serve multiple premises,Downstream signals are broadcast to all premises sharing multiple fibers. Encryption can prevent eavesdropping.Upstream signals are combined using a multiple access protocol, usually time division multiple access (TDMA). The OLTs "range" the ONUs in order to provide time slot assignments for upstream communication.
• #5: Both tree and ring structures are used for optical access networkTree is used in densly populated area and ring for long ditance
• #6: Among this olt failure and link failure are very important because lots of users effected.
• #8: Cost of olt is very high around There is no built in fault monitoring methods . We must use traditional tools such as OTDR(Optical time division reflectometer)Disruption duration is high to reduce this in dual home architecture we can put the back olt always live and it will increase the power consumption and lead to increase of cot
• #12: Working:If SHOAN works without any disruption the deployed cross bar switches are all in bar state. If a failure occurs bar connection looses their signals and it turn to cross state this lead to automatic service recovery.
• #13: For tree based access networkObviously, themore crossbar switches are placed in SHOAN (for example, atlocations where fault monitoring is desired), the more robustis its survivability. SHOAN can connect two or more accesssystems no matter whether their users are in the same area ornot (for example, see Fig. 4, where we can suppose that eachaccess system is deployed in different areas but they have thesame central office. Even if their central offices are different,we can deploy or adjust their fibers routes, and then putcrossbars where they meet each other on the way). SHOANshould get more robust if it connects two access systems indifferent areas because location-related risks can be furtherdisjointed by distance.
• #14: Cost: in dual home solution each access system need at least 2 olt but shoan need only one and a crossbar switch (its cost is less than the cost of olt)Fault monitoring ; already explained in slide 9Disruptions duration :
• #15: In shon wherever a failure occurs services can be self recovered by just turning the affected cross bars from bar state to cross state , without the process of fault localization and identification. Compared to dual-home architectre SHOAN is more reliable to end users because it reduces the disruption duration.
• #16: It consist of cross bar enabled olt called CEO ONU (optical distribution network) : The combination of fiber and splitter is called ONU.Cross bar functional ONU called CFO. In this solution an N*N switch is used for ONUA CEO sends out downstream signal to corresponding ONU and the signal is split to N portion and broadcast to all CFOs.All upstream signals are multilexed on the other side of ONU and send back to its corresponding CEO.Why do we need cross bars @ ONU ?
• #18: AWG:Arrayed waveguide gratings (AWG) are commonly used as optical (de)multiplexers in wavelength division multiplexed (WDM) systems. These devices are capable of multiplexing a large number of wavelengths into a single optical fiber, thereby increasing the transmission capacity of optical networks considerably.