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  1. 1. By Ayodeji Morakinyo 1Bimonthly Presentation Dense Wavelength Division Multiplexing (DWDM) AT THE SPEED OF IDEAS
  2. 2. By Ayodeji Morakinyo Bimonthly Presentation 2 1. Introduction 2. Optical Transmission 3. Comparison between DWDM and TDM 4. DWDM Components 5. DWDM Networks 6. Transmission Quality Parameters 7. ALU DWDM solutions Agenda
  3. 3. By Ayodeji Morakinyo Bimonthly Presentation 3 Introduction Multiplexing is the process of combining two or more signals together based on space, time or wavelength division in order to increase the amount of information transmissible over a single communication channel per time. Encoder Communication Channel Decoder Data Data Noise/Interference S o u r c e S i n k Attenuation This presentation will briefly discuss Dense Wavelength Division Multiplexing (DWDM) as a means of achieving effective fibre-optic transmission.
  4. 4. By Ayodeji Morakinyo Bimonthly Presentation 4 Optical Transmission Optical transmission involves the sending of binary signals in form of light pulses over an optical channel (fibre) so that they can be decoded and demodulated at the receiving end.
  5. 5. By Ayodeji Morakinyo Bimonthly Presentation 5 DWDM Offers: Transparency... .ATM, SDH, ESCON, GE, etc. Scalability . MAN, P-to-P, Rings, Meshes, etc. Dynamic Provisioning High BW services in days rather than months DWDM is coupled at 193.1THz (ITU-T) and it is on the 1st layer of the architecture so, it can accommodate ATM, SONET/SDH, ESCON, IP, etc. DWDM is a multiplexing technique of the fibre-optic transmission system that is used to increase the BW of an optical fibre such that several different signals can be transported simultaneously on the fibre. SDH data stream + Ethernet data stream (without interference) 40Gbit/s, 100Gbit/s
  6. 6. By Ayodeji Morakinyo Bimonthly Presentation 6 Combining Signals Separating Signals Transmission on fibre LASER to MUX to TRASNMISSION COMPONENTS to DEMUX to RECEIVERS The Tx components include optical switches, amplifiers, fibre-optic cable, couplers, etc. DWDM Representation n+n+n+n
  7. 7. By Ayodeji Morakinyo Bimonthly Presentation 7 Optical transmission incorporates digital processing technique with optical transmission consequently, error can be detected and corrected. For example, FEC allows errors and optical impairments which may be introduced by NEs such as DXC and OADMS to be corrected. ITU specifies 6 Tx bands for fibre-optic transmission: There is an undefined 7th band: 850nm region O 1260 1310 nm E 1360 1460 nm S 1460 1530 nm C 1530 1565 nm L 1560 1625 nm U 1625 1675 nm
  8. 8. By Ayodeji Morakinyo Bimonthly Presentation 8 Apart from the bandwidth multiplicity advantage, optical transmission also provides link and ring protection to its deployers thereby, ensuring reliable business continuity. Again, theres no risk of getting shocked and installers do not have to wear special protective attires. However, theres a need to be careful of the laser radiation. The beam of the laser radiation unit must not be directly observed. Also, dispersions which often occur can be easily rectified using DCUs while the inherent losses associated with this system of transmission are counterbalanced by applying optical amplifiers at specific points along the transmission line. And, it is not susceptible to EMI.
  9. 9. By Ayodeji Morakinyo Bimonthly Presentation 9 THE FIBRE-OPTIC CABLE is a thin strand of glass or plastic that serves as the DWDM transmission medium. It consists of the section that carries the signal and the part that protects it from environmental and mechanical damage. Fibre types based on manufacturing material can be: Glass Fibre Plastic-clad Silica (PCS) Plastic n2 n1 Cladding Core
  10. 10. By Ayodeji Morakinyo Bimonthly Presentation 10 Light is transmitted through fibre in guided modes i.e. TEmn and TMmn. TE refers to transverse electric field while TM refers to the transverse magnetic field. Hence, we have TE01 TE10 TM01 TM10 modes. In DWDM, the fibre modes used are the single and multi-modes. However, the single mode is preferred by transmission deployers due to the multiplied effects of scattering and absorption on the multi-mode fibre. During the manufacturing process, all impurities cannot be removed from the material. These residual impurities are therefore responsible for the inherent attenuation characteristic of the fibre-optic cable. The other resultant effect of scattering and absorption is modal dispersion. . . . . . . . . . . . . . . . . . . . . . . . . Absorption Scattering
  11. 11. By Ayodeji Morakinyo Bimonthly Presentation 11 DISPERSION & ATTENUATION Dispersion and Attenuation occur in fibre-optic transmission using DWDM and these influence the quality of light signal transmitted along the line. Since both problems are inherent in this transmission system, adequate solution must be provided. This may be in form of dispersion compensating devices. Due to dispersion, clarity is reduced with distance and speed and the light waves tend to scatter. Due to attenuation, power levels are reduced with distance.
  12. 12. By Ayodeji Morakinyo Bimonthly Presentation 12 PATCH CORDS & COUPLERS Patch cords are small fibre optic cables of narrow diameters used to connect the terminal points of one equipment to another on the distribution frame. They are also used to connect to test devices when troubleshooting or measuring power levels of optical signals. Generally, fibre optic cables can either be single mode or multimode. As such, patch cords come in both SMF and MMF types. But SMF is mostly used due to its smaller diameter which in turn reduces the modal dispersion. In MMF, modal dispersion occurs because the rays of light entering at one end of the fibre do not all arrive at the other end at the same time.
  13. 13. By Ayodeji Morakinyo Bimonthly Presentation 13 Patch cords could also be classified based on their type of end connectors. For example, we have FC, LC, MU, SC, ST, MT-RJ, etc. SC MT-RJ SMA FC
  14. 14. By Ayodeji Morakinyo Bimonthly Presentation 14 COUPLERS Couplers are fibre-optic materials used to join one patch cord to another or to extend connections from one patch panel to another. They are often employed during ADM installation to fix patch cords to the trays. This allows for neat and orderly arrangement in the trays. When the two end connectors of a patch cord are of the same type, it is called a coupler.
  15. 15. By Ayodeji Morakinyo Bimonthly Presentation 15 TEST KITS & EQUIPMENT During and after fibre-optic transmission installation, there is a critical need to perform certain tests to ensure proper functionality of the equipment before provisioning can be allowed. The test kits and equipment for DWDM but are not limited to: Fiberscope Cleaners and cleaning set Optical Spectrum Analyzer (OTDR) Gigabit Ethernet Tester Splicing & Labelling Machines Crimping tools, screw drivers, tapes, etc, are used during installation. MTS6000MTS8000 GB TESTER
  16. 16. By Ayodeji Morakinyo Bimonthly Presentation 16 Cleaning spray OLP Cleaning set (pads & swabs) Gigabit Analyzer OLA OLS
  17. 17. By Ayodeji Morakinyo Bimonthly Presentation 17 DWDM Vs TDM DWDM TDM Increase the number of wavelengths Can handle 40Gbps and above. The specific limits of this technology are still unknown. All signals arrive at the same time rather than being broken up and carried in time slots. Increase the bit rate At 40Gbps, severe technical issues occur. PMD and CMD are the most common ones. To increase capacity, time must be sliced into smaller intervals so that the bits from multiple sources can carried on the link
  18. 18. By Ayodeji Morakinyo Bimonthly Presentation 18 Incoming Streams with bit rate of 2.5Gbps Outgoing Streams with bit rate of 4 X 2.5Gbps In TDM, a particular data stream is assigned a time slot with other data streams and the allotted time slots repeat over a given interval.
  19. 19. By Ayodeji Morakinyo Bimonthly Presentation 19 MUXES & DEMUXES Multiplexers combine several laser signals of different wavelengths together to produce a converged beam. Examples of this cards are BMDX 1000, BMDX 1100. ... Multiplexers basically comprise lens and prisms which diffract the impinging light rays and refocus them into a single beam. The reverse is the case for DEMUXES DWDM Components
  20. 20. By Ayodeji Morakinyo Bimonthly Presentation 20 Demultiplexers perform the reverse function of multiplexers. They separate the received multiplexed signals (originally combined into a beam by the MUX) into their wavelength components and couple them into their individual fibres. DEMUX ... MUX/DEMUX alike are either passive or active. Passive designs are based on prism, waveguide and filters while active designs are different from the passive ones because they have tunable filters.
  21. 21. By Ayodeji Morakinyo Bimonthly Presentation 21 TRANSPONDERS Transponders convert energy from one form to another (e.g. electrical to optical energy or vice versa). They accept input from different physical media and protocols in various traffic formats and map them into wavelengths on the MUX. Transponders perform the 3R functions of retiming, reshaping & reamplification. Examples of transponder cards in DWDM are the TRBD and the TRBC cards. Local and remote Loop backs are created on the transponder cards to allow for troubleshooting purposes. Consequently, faults in the transmission path can be identified with the aid of test devices.
  22. 22. By Ayodeji Morakinyo Bimonthly Presentation 22 AMPLIFIERS are devices used to boost signal power after multiplexing and before demultiplexing. Due to attenuation, there are limits to how long a fibre can propagate a signal with integrity before it has to be regenerated. With the use of optical amplifiers, this can be achieved. Examples are the ALU LOFA cards. Post-Amplifiers: are placed directly after the optical transmitter to provide maximum output power. In-Line Amplifiers: modify a small input signal and boost it for retransmission down the fibre. Pre-Amplifiers: are placed prior to the receiver so that much larger signals can presented to it.
  23. 23. By Ayodeji Morakinyo Bimonthly Presentation 23 EDFA: is an optical amplifier made out of erbium material. Erbium is a rare-earth element which when excited emits light around 1.54m and this makes it suitable for usage in DWDM optical amplifier manufacture. Other dopants used to manufacture fibre amplifiers are Tellurite and Thulium. What happens in the EDFA? When a weak signal enters the EDFA, light at 980nm or 1480nm is injected using a laser pump held in place by a coupler and this stimulates the erbium atoms to release their stored energy as additional 1550nm light. As this process continues down the fibre, the signal grows stronger.
  24. 24. By Ayodeji Morakinyo Bimonthly Presentation 24 OADMS Oftentimes along the fibre span and due to access needs, the insertion or removal of certain wavelengths becomes necessary. OADMs are DWDM equipment that make this possible. Though similar to the SDH ADMs, OADMs only add/drop optical signal and no conversion from optical to electrical form occurs. Fixed OADMs: are physically configured to drop specific wavelengths while adding others. Reconfigurable ADMs: are capable of dynamically selecting which wavelengths are dropped and added.
  25. 25. By Ayodeji Morakinyo Bimonthly Presentation 25 DWDM Networks DWDM Networks basically consists of the core (long haul), distribution (MAN) and access networks. Long Haul/Backbone/Core Network: are located at the core of global network consisting of transnational and global carriers. It is the central part of a telecom network that provides services to the customers through MANs. BB or LH networks usually have mesh and/or ring topologies that provide flexible connections between several devices (switches and routers). Examples of technologies used at this network level are DWDM, SDH, ATM, IP, GBE, etc. The BB primarily functions as: operation & maintenance centre user request authentication call control/switching with number portability service charge handling unit service invocation such as call transfer or waiting the gateway
  26. 26. By Ayodeji Morakinyo Bimonthly Presentation 26 DWDM Networks
  27. 27. By Ayodeji Morakinyo Bimonthly Presentation 27 Metropolitan Area Network/ Distribution Network: lies at a critical junction that has many characteristics as the access networks e.g. protocols & channel speeds. Like access networks, MANs have been traditionally SDH-based using point- to-point or ring topologies with ADMs. But because it must meet the needs of the ever-increasing bandwidth at LH network while addressing the growing connectivity requirements at the access level, an efficient means of achieving simpler and faster provisioning such as DWDM is of key importance. Access Networks: are closest to the end users at the edge of the MAN. It is the part of the telecoms network that connects subscribers to their immediate service provider. Access networks are characterised by diverse protocols and infrastructures and span a broad spectrum of access rates. customers range from residential internet users and individual service subscribers to large corporations & institutions.
  28. 28. By Ayodeji Morakinyo Bimonthly Presentation 28 TOPOLOGIES IN DWDM NETWORKS Point-to-Point Topology: are characterised by ultra-high channel speeds (10 to 40Gbps), high signal integrity and reliability, and fast path restoration. It can be implemented with or without an OADM. In LH networks, the distance between Tx and Rx can be hundreds of Kilometres with about 10 amplifiers installed between the endpoints.
  29. 29. By Ayodeji Morakinyo Bimonthly Presentation 29 In Point-to-Point topology, protection can either be at system level where switchover is the responsibility of the client equipment (e.g. router or switch) or at card level where switching (in case of failure) is performed by the DWDM systems. Ring Topology: allows several nodes to provide access to routers, switches or servers by adding or dropping wavelengths on the optical channel. This topology can be configured to support most forms of traffic, accommodate hub stations and one or more OADMs. It is mostly found in the MANs and spans up to a few or ten of kilometres. Bit rate is in the range of 622Mbps to 10Gbps/channel.
  30. 30. By Ayodeji Morakinyo Bimonthly Presentation 30 In ring topology, protection can either be Unidirectional Protection Switched Ring (UPSR) where just two fibre pairs are used or Bidirectional Line Switched Ring (BLSR) where up to 4 fibres may be used.
  31. 31. By Ayodeji Morakinyo Bimonthly Presentation 31 Mesh Topology: consists of interconnected optical nodes that are three or more point-to-point connections linked together. It begins with point-to-point links equipped with OADM nodes at the onset and subsequently interconnects them such that the network evolves into a mesh without complete redesign. It is expected that, in the near future, redundancy will migrate from system, card and fibre levels to the wavelength level. When this happens, a data channel will be able to change wavelength as it makes its way through the network because of a fault.
  32. 32. By Ayodeji Morakinyo Bimonthly Presentation 32 Tx Quality Parameters OSNR is the ratio of power in the signal to the noise that is with the signal. In most cases, an OSNR of 10dB or better is needed for error-free operation. OSNR= 10log(Ps/Pn) Where: Ps is the signal power and Pn is the noise power. Each in-line amplifier (repeater) gives some noise to the system. The build-up of amplifier noise is therefore proportional to the number of amplifiers. And as such, total accumulated noise equals the product of Noise per repeater and the total number of repeaters. Total Accumulated Noise = Noise of 1 repeater Total No of repeatersx
  33. 33. By Ayodeji Morakinyo Bimonthly Presentation 33 BER is the ratio of error bits to the total transmitted bits. BER is a dimensionless and the performance parameter is often expressed as percentage. Bit synchronization problems and attenuation are factors affecting bit error rate but it may be improved by ensuring that adequate error detection and correction techniques are applied and signal strength is fairly strong. 1 1 0 0 1 0 1 Data streams of ones and zeroes
  34. 34. By Ayodeji Morakinyo Bimonthly Presentation 34 Q FACTOR is a measure of how noisy a pulse is for diagnostic purposes. The higher the Q-factor, the freer the pulse is from noise. It is a dimensionless parameter that describes how under-damped a resonator is or relative to the stored energy of the resonator. If the Q-factor of a laser cavity is abruptly changed from a low value to a high one, the laser will emit a pulse of light that is much more intense than the lasers normal continuous output. Eye pattern shows the eye is as open as possible and indicates that the data can be recovered easily with low effects from noise.
  35. 35. By Ayodeji Morakinyo Bimonthly Presentation 35 1626LM ALU DWDM Solutions is a scalable Alcatel DWDM platform initially developed for the core network for LH and ULH applications. It provides a high transmission capacity on a single optical fibre by multiplexing up to 96 x 10Gb/s (STM64/OC192) channels on a 25GHz grid. It is used for: regional terrestrial application reconfigurable OADM: line terminal, line repeater and access to traffic band OADM Back-to-back terminal upgrading existing infrastructure
  36. 36. By Ayodeji Morakinyo Bimonthly Presentation 36 1640WM is a core Alcatel DWDM system supporting up to 160 channels in C and L ands with 50GHz spacing and standard synchronous bit rates from 2.5Gbps to 10Gbps. 1686WM is a regional and metropolitan Alcatel DWDM system scalable up to 32 channels in C band and 40 channels in L band. It supports different bit rates from 100Mbps to 10Gbps.
  37. 37. By Ayodeji Morakinyo Bimonthly Presentation 37 1696MS is a cost-effective metropolitan Alcatel DWDM system supporting a broad range of data rates, easily customized for intra-city networks. 1830PSS is a scalable optical transport platform for regional and MAN transport and services delivery. It provides 88 channel support, wavelength tracking and single fibre bidirectional transmission. It also supports point-to-point linear, ring and mesh-capable networks and is 2.5G/10G/40G transport ready.
  38. 38. By Ayodeji Morakinyo Bimonthly Presentation 38 It is obvious that DWDM enables bandwidth multiplication, provides extra resilience, improves scalability, permits multiple logical topologies over single physical MAN and therefore makes optical transmission more effective. That is why many telecoms service providers adopt it regardless of its initially high cost of implementation. But true investors know that on the long run, the capital will yield good returns by improving their QoS and customer/subscriber base.
  39. 39. By Ayodeji Morakinyo Bimonthly Presentation 39 Thank You for Your attention AT THE SPEED OF IDEAS