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NETE0510 Optical Networking

NETE0510 Optical Networking. Supakorn Kungpisdan supakorn@mut.ac.th. Outline. History of Optical Networking SONET/SDH Standards DWDM. History of Optical Networking. Optical telegraph was invented in the 1790s In 1880, Alexander Graham Bell patented the optical telephone system

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NETE0510 Optical Networking

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  1. NETE0510Optical Networking Supakorn Kungpisdan supakorn@mut.ac.th NETE0510: Communication Media and Data Communications

  2. Outline • History of Optical Networking • SONET/SDH Standards • DWDM NETE0510: Communication Media and Data Communications

  3. History of Optical Networking • Optical telegraph was invented in the 1790s • In 1880, Alexander Graham Bell patented the optical telephone system • Modern optical communications started in 1950s with the development of pulsing-laser technology (light) across fiber (glass or plastic) with low loss rates to achieve high-speed data and voice communications transfer • SONET/SDH define basic transmission rates and characteristics, frame formats and testing, and an optical interface-multiplexing scheme • Had been main WAN transport technology through 1990s • Now DWDM allows 160 wavelengths per fiber, each 2.5-10 Gbps NETE0510: Communication Media and Data Communications

  4. Outline • History of Optical Networking • SONET/SDH Standards • DWDM NETE0510: Communication Media and Data Communications

  5. SONET/SDH • SONET and SDH are U.S. and International standards, respectively, for optical telecommunication transport • Provide a technology that enables the major service providers to internationally standardize and control broadband network transport media through a common fiber interface called a “midspan meet”. NETE0510: Communication Media and Data Communications

  6. SONET/SDH Advantages • Reduction of equipment needed and increase network reliability and availability • Centralized fault isolation and management of payload (traffic carried) • Synchronous multiplexing formats for DS1 and E1 allowing easy access for switching and multiplexing • International vendor interoperability • Flexible architecture able to accommodate future requirements NETE0510: Communication Media and Data Communications

  7. Synchronous, Plesiochronous, Asynchronous • Synchronous • All clocks are traceable to one Stratum 1 primary reference clock (PRC) • All digital transitions in the signals occur at exactly the same rate • Plesiochronous • Clocks are extremely accurate and almost exact, but small difference between them • Asynchronous • The clocks do not have to match or be equal NETE0510: Communication Media and Data Communications

  8. Layers in SONET NETE0510: Communication Media and Data Communications

  9. Layers in SONET(cont’d) • Physical Layer • Define physical fiber type, path, and characteristics • Include many electrical interfaces which become virtual channels within the Synchronous Transport Signal-1 (STS-1) frame – the base level building block of SONET • Section Layer • Build SONET frames from either lower SONET interfaces or electrical interfaces • Line Layer • Provide synchronization, channel multiplexing, and protection switching • Path Layer • Manage actual data transport across the SONET network NETE0510: Communication Media and Data Communications

  10. SONET Network Structure NETE0510: Communication Media and Data Communications

  11. SONET Network Structure (cont’d) • Path: information carried end-to-end • Line: information carried for STS-n signals between multiplexers • Section: information carried for communication between adjacent network equipment, e.g. regenerator • Path-terminating equipment (PTE): user interface at the CPE • Line-terminating equipment (LTE): a terminal, switch, add/drop multiplexer, or cross-connect • Section-terminating equipment (STE): a regenerator NETE0510: Communication Media and Data Communications

  12. SONET Structure NETE0510: Communication Media and Data Communications

  13. SONET Structure (cont’d) NETE0510: Communication Media and Data Communications

  14. Frame Format NETE0510: Communication Media and Data Communications

  15. SONET Frame Format NETE0510: Communication Media and Data Communications

  16. STS-1 Overhead • Section Overhead (9 bytes  3 columns x 3 rows) • Performance monitoring • Framing • Messaging communication between STEs for control, monitoring, administration, and other communication needs\ • Voice communication between STE • Line Overhead (18 bytes  3 columns x 6 rows) • Locating the SPE in the frame • Multiplexing or concatenating signals • Performance monitoring • Automatic protection switching • Line maintenance NETE0510: Communication Media and Data Communications

  17. STS-1 Overhead (cont’d) • Path Overhead (9 bytes  1 column x 9 rows) • Performance monitoring of the SPE • Path signal label, which indicates the content of the SPE • Path status, which conveys status and performance back to the originating terminal • Path trace, which allows verification of continues connection with the originating terminal NETE0510: Communication Media and Data Communications

  18. STS-1 Synchronous Payload Envelope (SPE) • SPW is defined as 783 bytes  87 columns x 9 rows • The first column is the path overhead • Columns 30 and 59 are not used for payload, but designated to fixed stuff columns • So it remains 84 columns x 9 rows  756 bytes of payload • To support service that requires a payload larger than STS-1, SONET allows concatenating STS-1s together to support NETE0510: Communication Media and Data Communications

  19. Pointers • Located in the line overhead of each frame • Used for frame synchronization • Identify subchannels down to the DS0 level within a SONET transmission NETE0510: Communication Media and Data Communications

  20. Pointers NETE0510: Communication Media and Data Communications

  21. Virtual Tributary (VT) • VTs are the building blocks of the SPE • VTxx designates VTs of xx Mbps NETE0510: Communication Media and Data Communications

  22. Virtual Tributary (VT) • 7 VT groups • 4 VT1.5s • 3 VT2s • 2 VT3s • 1 VT6 • 2 bit-stuffed unused columns • 1 path overhead column Locked mode: fix the VT structure within an STS-1 and is designed for channelized operation Floating mode: allow these values to be changed by cross-connects and switches NETE0510: Communication Media and Data Communications

  23. Multiplexing • SONET provides direct multiplexing of both SONET speeds and current asynchronous and synchronous services into the STS-n payload • Payload types range from DS1 and DS3 to OC-3c and OC-12c payloads • STS-1 supports direct multiplexing of DS1 and DS3 into single or multiple STS-1 envelopes, which are called VTs • Multiple STS-1 envelopes are multiplexed into an STS-n signal • Each individual signal down to DS1 can be accessed without the need to demultiplex and remultiplex the entire OC-n level signal •  use a SONET digital cross-connect (DXC) or multiplexer • SONET multiplexing requires an extremely stable clocking source with a stable reference point • Frequency of every clock within the network must be the same as or synchronous with the others • The central clocking source is typically a Stratum 1 source NETE0510: Communication Media and Data Communications

  24. Multiplexing NETE0510: Communication Media and Data Communications

  25. SONET Hardware • Most common equipment term used is the SONET terminal equipments: • SONET Terminating Multiplexer • SONET Add/Drop Multiplexer (SADM) • SONET Digital-Loop Carrier Systems (DLCs) • SONET Digital Cross-Connects (SDXCs) • SONET Regenerators and Optical Amplifiers NETE0510: Communication Media and Data Communications

  26. SONET Terminating Multiplexer • Provide user or customer premises equipment (CPE) access to the SONET network • Aka terminal adapter, edge multiplexer, or terminal • Similar to M13 multiplexer and allow low-speed access to SONET backbone • Turn electrical interfaces into optical signals by multiplexing multiple DS1, DS3, or E1 VTs into the STS-n signals required for OC-n transport • Arranged in point-to-point configuration NETE0510: Communication Media and Data Communications

  27. SONET Add/Drop Multiplexer (SADM) • Add/Drop Multiplexer • Add one or more lower-bandwidth signal on to a high-bandwidth stream • Drop or extract other signals, removing them from the stream and redirecting them to some other network paths • Traditional ADM is asynchronous at DS3 and lower speed. • Require multiple equipments e.g. M13 MUX • SADM enables provider to drop and add not only the lower SONET rates, but also electrical interface rates sown to the DS1 level NETE0510: Communication Media and Data Communications

  28. SONET Add/Drop Multiplexer (SADM) • Standard features: • drop-and-insert:a process that diverts (drops) a portion of the multiplexed aggregate signal at an intermediate point, and introduces (inserts) a different signal for subsequent transmission in the same position, e.g., time slot or frequencyband, previously occupied by the diverted signal. • drop-and-continue: drop some signals while allowing others to pass • Used for distributed point-to-point network connectivity • A CO device forming the building blocks of the SONET network • Enable easy expansion and are often used in SONET ring architectures • Operate at the higher transmission speeds of OC-3 through OC-192 NETE0510: Communication Media and Data Communications

  29. SONET Add/Drop Multiplexer (SADM) NETE0510: Communication Media and Data Communications

  30. SONET Digital-Loop Carrier Systems (DLCs) • Concentrate multiple DS0 traffic from remote terminals into a single OC-3 signal • Situated at local service providers and handle both voice and data traffic providing a SONET network interface for non-SONET equipment NETE0510: Communication Media and Data Communications

  31. SONET Digital Cross-Connects (SDXCs) Act as a gateway to SONET network NETE0510: Communication Media and Data Communications

  32. SONET Regenerators and Optical Amplifiers • Both perform optical signal regeneration over fiber optics • Optical amplifiers just amplify the signal and noise • Regenerators reshape, retime, and retransmit signals that have incurred dispersion or attenuation over long transmission distances NETE0510: Communication Media and Data Communications

  33. SONET Network Configurations • Point-to-point • Two PTE pieces of equipment are connected directly together with a STE/regenerator in line • Point-to-multipoint • The PTE equipment is connected to a LTE/SADM that enables circuits to be added or dropped along the way • Ring • Are deployed in most large-scale service provider networks NETE0510: Communication Media and Data Communications

  34. SONET Ring Architecture Normal operation Fiber cut of both pairs Working pair outage NETE0510: Communication Media and Data Communications

  35. SONET Advantages • Reduced network complexity and cost through SADM and SDXC capabilities • Ability to transport all forms of traffic: voice, data (ATM, IP), and video • Capability to build optical interconnects between carriers • Efficient management of bandwidth at the physical layer • Aggregation of low-speed data channels into common high-speed backbone trunk transport • Standard optical interface and format specification providing vendor interoperability • Increased reliability and restoration over electrical systems • Increased bandwidth management through logical path grooming • Smart OAM&P features with uniformity NETE0510: Communication Media and Data Communications

  36. SONET Disadvantages and Challenges • Strict synchronization schemes required • Complex and costly SONET equipment contrast to chapter optical Ethernet and other alternate MAN technologies • High percentage of SONET protocol overhead • Fiber laying unutilized in a ring architecture, waiting on a failure NETE0510: Communication Media and Data Communications

  37. Outline • History of Optical Networking • SONET/SDH Standards • DWDM NETE0510: Communication Media and Data Communications

  38. Dense Wavelength Division Multiplexing (DWDM) • Three methods to relieve capacity shortage: • Increase the bit rate of existing systems, such as moving OC-48 systems to OC-192 systems • Install new fiber • Optimize the use of existing fiber using methods like increasing the number of wavelengths (and thus bandwidth available) per fiber • DWDM NETE0510: Communication Media and Data Communications

  39. WDM NETE0510: Communication Media and Data Communications

  40. DWDM VS WDM • Similar  enable more than one wavelength to be added to a single-mode fiber • Increased capacity depends on the number of wavelengths added • Current systems support 160 wavelengths per fiber • DWDM spaces the wavelengths closer than WDM and therefore has a greater overall capacity than WDM NETE0510: Communication Media and Data Communications

  41. Advantages of DWDM • Every wavelength is independent of the others • Can transport SONET, gigabit Ethernet, or native ATM on the same optical fiber cable • Do not require a large amount of overhead as that of SONET • Optical amplifier can apply to all wavelengths  cost savings • Having 160 wavelengths on a DWDM fiber will save amplifier 160:1 NETE0510: Communication Media and Data Communications

  42. DWDM Hardware • DWDM multiplexer/demultiplexer • Combine multiple optical signal into a single optical fiber • Separate optical wavelengths into a single wavelength fiber • Optical add/drop multiplexer (OADM) • Like SADM, but in the optical domain • Allow wavelengths to be split or added to a DWDM fiber • OXC • A cross-connect between n-input ports and m-output ports • Perform management of wavelengths at the optical layer • Optical amplifier • Amplify signal strength to travel over long distances • Regenerator • Same functionality as amplifier with resharing and retiming capabilities NETE0510: Communication Media and Data Communications

  43. Optical Amplifiers/Regenerators NETE0510: Communication Media and Data Communications

  44. Interfaces • DWDM supports many different types of interfaces: • SONET • Ethernet (1Gbps, 10Gbps, and fast) • Fiber channel • ATM NETE0510: Communication Media and Data Communications

  45. DWDM Network Configuration • Point-to-point • The network must have the characteristics of ultra high-speed channels (10-40Gbps), high signal integrity and reliability, and fast path restoration • Distance btw transmitters and receivers can be several hundred kms with less than 10 amplifiers • Ring • SONET rings can be built with the combination with DWDM • Mesh (partial or full) • Mesh architectures connect all-optical nodes together with two routes, and implement intelligence in the notes to reroute wavelengths on faults • Extremely expensive to implement andmanage NETE0510: Communication Media and Data Communications

  46. Advantages of DWDM • Support 160 wavelengths  over 1 Tbps of traffic to be carried • Each wavelength can be a different traffic type e.g. SONET, gigabit Ethernet, IP over PPP, and can operate at different speeds • Optical amplifiers provide cost saving NETE0510: Communication Media and Data Communications

  47. Disadvantages of DWDM • Some fiber plant are not suitable for DWDM and do not support DWDM • Difficult to troubleshoot, manage, and provision. • Need to manage DWDM-specific equipment • Vendor interoperability issues NETE0510: Communication Media and Data Communications

  48. Questions? Next Lecture Physical Layer Protocols and Access Technologies NETE0510: Communication Media and Data Communications

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