Presentation on theme: "Fiber Optic Communication By"— Presentation transcript:
1 Fiber Optic Communication By Engr. Muhammad Ashraf Bhutta
2 Lecture Outlines SDH Overview Frame structure and multiplex-ing methodsOverheads and Pointers
3 SDH Overview Background of SDH Disadvantages of PDH Advantages of SDH Disadvan-tages of SDH
4 Background about SDH emergence What is SDH--Synchronous Digital Hierarchy. Similar toPDH，they are all digital signal transmission system.Why did SDH emerge?1)What we need in info-society:huge volume of info, and digital, integrated, personal.2)What we want the transmission network to be:Broadband---info-highwayStandard---universal interface all over the world
5 Disadvantages of PDH: 1 Interfaces Electrical interfaces---only regional standards, no universal standard.3 rate hierarchies for PDH:European(2Mb/s) Japanese, North American(1.5Mb/s).Optical interfaces---no standards at all, manufacturers develop at their will.
6 Multiplexing methods: Asynchronous Multiplexing for PDH:The location of low-rate signals in high-rate signals is notregular nor predictable. So it is impossible to directlyadd/drop low-rate signals from high-rate signals.Wheredid I putthe signals?
7 Low-rate signals have to be separated from high-rate signals level by level. Multiple levels of multiplexing/de-multiplexing cause signals to deteriorate, it is not suitable for huge-volume transmission.
8 OAM 4 No universal network management interface OAM function affects the maintenance cost.It is determinedby the number of overhead bytes(redundant bytes);There are VERY few redundant byes available in PDHsignals which can be used as OAM purpose, so OAM in PDHis very poor, it is unreliable either.4 No universal network management interfaceIt is hard to set up an integrated networkmanagement. No way to form a universal TMN.PDH is inappropriate to transmit huge-volume signals, soSDH came to play the part.
9 Advantages of SDH: 1 Interfaces Electrical interfaces:standard rate hierarchy(transmission speed level)The basic rate level is called Synchronous Transfer Module(STM-1), the other rate levels are the multiple of STM-1.Optical interfaces:only scramble the electrical signals.SDH: optical code pattern is scrambled NRZ,PDH: optical code pattern is scrambled mBnB.
10 SDH:high-rate signal is exactly 4 times that SDH SignalsBit rate(Mb/s)STM-1or 155MSTM-4or 622MSTM-16or 2.5GSTM-64or 10GSDH:high-rate signal is exactly 4 times thatof the next low-rate signal.
14 PDH Pkg Packing PKG a PKG b Other signals→SDH: Using pointers to align the low-rate signals in SDH frame,so the receivers can directly drop low-rate signals.E.g.:PDHPackingPkgAlignmentPKG aPKG bSTM-1
15 3 OAM 4 Compatibility More bytes in SDH frame structure are used for OAM purpose, about 5% of total bytes. SDH boastsof high capability of OAM.4 CompatibilitySDH is compatible with the existing PDH system.SDH allows new types of equipment to be used,allows broadband access, such as ATM.
17 Disadvantages of SDH 2M STM-1 (155M) 34M 140M 1 low bandwidth utilization ratio--- contradictionbetween efficiency and reliability.140M34M2M1140M=642M334M=482M632MSTM-1(155M)2 Mechanism of pointer adjustment is complex, it cancause pointer adjustment jitters3 Large-scale application of software makes SDH systemvulnerable to viruses or mistakes.
18 Frame Structure and Multiplexing methods Multiplexing ProcedureComponents and functions140M34M2MSTM-N
19 STM-N Frame Structure Transmission direction 1 SOH 3 4 AU-PTR 9×270 ×N bytesTransmission direction1Transmitleft to rightup to downSOH34AU-PTRSTM-N payload(including POH)5SOH99×N261×N270×N columns
20 1 Characteristics of SDH signals: block frame in units of bytes(8bit),transmission---from left to right, from top to bottom,frame frequency constant frames/s,frame period 125us.2 Composition of SDH signals:1) Payload:It is where we put all the information in STM-N framestructure. All kinds of effective info, such as 2M, 34M ,140M are first packed before being stored here. Thenthey are carried by STM-N signals over the SDH network.
21 If we should consider STM-N signal to be a truck, then info payload would be the carriage of the truck. In order tomonitor the transmission status of the goods duringtransportation, POH are added to each information package.PkgPayloadLow-rate signals 1Low-rate signals nloadingPOHpackingSTM-N
22 2) Section Overhead:Accomplishes monitoring of STM-N signal streams. To checkwhether the “goods” in STM-N “carriage” is damaged or not.Regenerator Section Overhead(RSOH): monitor the overallSTM-N signals.Multiplex Section Overhead(MSOH): monitor each STM-1in STM-N signal.RSOH, MSOH and POH set up SDH layeredmonitoring mechanism.
23 Sections and Paths SDH Section signal (SOH) low-rate path signal(POH) .SDHSection signal(SOH)Low-rate signal 1Low-rate signal 2Low-rate signal nlow-rate path signal(POH)Sections and Paths
24 3) Administrative Unit Pointer(AU-PTR): Indicates the location of low-rate signals in STM-Nframe(payload), makes the location of low-ratesignals in high-rate signals predictable.
25 According to the value of AU, the receiver can directly drop low-rate signals from STM-N frame. That is tosay we can get the “goods” directly from the “carriage”if we know the label of the “goods”.Because the “goods” are placed regularly in the“carriage”, we only need to know the first piece of“goods”.
26 Receiving: Sending: According to the value of AU-PTR, get the first infopackage, through theregularity of byte interleavedmultiplexing, get the otherpackagesSending:AU-PTR indicates the firstinfo package键入文本键入文本(SDH transmissionnetwork)
27 For low-rate signals such as 2M, 34M. We need two-levels of pointers to align.First, small information “goods” is packed into middleinformation “goods”. Tributary unit pointer(TU-PTR)is used to align the location of small “goods” in middle “goods”.Then these middle “goods” are packed into big “goods”,AU-PTR is to align the location of middle info package.2M34MTU-PTRPrimary alignmentAU-PTRSecondary alignment
28 Multiplexing procedures of SDH low-rate SDH→high-rate SDH:byte interleaved multiplexing, 4 into 1.PDH signals→STM-N: synchronous multiplexing:140M→STM-N34M→ STM-N2M→STM-NMultiplexing is based on the multiplexing route diagram.ITU-T defines several different multiplexing routes, but forany country or region, the method is unique.
30 C4 VC4 140M multiplexing procedures(140M →STM-N) P O H 1 1 POH 140M 9 RateAdaptationPOHC4VC4To be continued140M99125us125usC4---Container 4: A standard info structure corresponding to 140M,performs bit rate justification.VC4---Virtual Container 4: A standard info structure correspondingtoC4, performs real-time performance monitoring of 140M
31 140M multiplexing procedures AU-4STM-111(continue)RSOHpayloadAU-PTR1270xNalignmentSOHAU-PTR119MSOH99102701270STM-N125us125usAU-4---Administrative Unit 4, a info structurecorresponding toVC4, performs pointer alignment.140M—VC4—AU-4—STM-1,One STM-1 can only incorporate one 140M signal.9125us
32 C3 VC3 34M multiplexing procedures P O H 1 1 POH 34M 9 9 1 84 1 85 Rate adaptationTo be continued34M99125us125usC3---Container 3: A standard info structure corresponding to 34M,performs bit rate justification.VC3---Virtual Container 3: A standard info structure correspondingto C4, performs real-time performance monitoring of 140M
33 VC4 34M multiplexing procedures TU-3 TUG-3 P O R R H 125us (continue) PTRH1H2H3FillGapRBIM125us1869261×3TU3---Tributary Unit 3: A standard info structure corresponding toVC3, performs primary alignment.TUG3---Tributary Unit Group 3: A standard info structurecorresponding toTU3.34M—VC3—TU3—TUG3；3 TUG3—VC4—STM-1；One STM-1 can hold 3 34M.
35 2M multiplexing procedures (2M →VC4) C12--Container 12: A standard info structurecorresponding to 2M, performs bit rate justificationfor 2M signals, 4 basic frames constitute a multi-frame.VC12---Virtual Container 12:A standard info structurecorresponding to 2M, performs real-time monitoring.TU12---Tributary Unit 12: A standard info structurecorresponding to VC12, performs primary pointeralignment forVC12.
36 TUG3 TUG2 2M multiplexing procedures (2M →VC4) R R 125us 125us 1 86 1 ×3×7ByteInterleavedMultiplexingByte InterleavedMultiplexingTUG2TUG3R R(continue)99125us125us
37 2M Multiplexing procedures(2M →VC4) TUG2---Tributary Unit Group 2TUG3---Tributary Unit Group 32M—C12—VC12—TU12；3TU12—TUG2；7 TUG2—TUG3；3TUG3—VC4—STM-1。One STM-1 is able to hold 3×7×3= 63 2M.Multiplexing structure for 2M is
38 SDH Multiplexer Concept of multi-frame: STM-1 1#3#2#4#63 2MConcept of multi-frame:4 C12 basic frames make up1 multi-frame.Both basic frames andmulti-frame carry the same2M signal.One basic frame can holdthe info segment of 2Msignal during 125us period.One multi-frame holds theinfo for 2M signal during500us period.
39 Relations between info structures VC12TU12E3C3VC3TU3E4C4VC4
40 Summary STM-N frame structure and functions of different parts of the frameMethods for multiplexing PDH into STM-N frames140M multiplexed into STM-N frames34M multiplexed into STM-N frames2M multiplexed into STM-N frames
44 SOH(take STM-1 as an example) 123456789A1*A1*A1*A2*A2*A2*J0***B1E1F1RSOHD1D2D3AU-PTRB2B2B2K1K2D4D5D6D7D8D9MSOHD10D11D12S1M1E2Bytes reserved for domestic useMarked bytes are not scrambled*
45 1) Framing bytes:A1,A2 to locate the frame heads STM-NSignal stream
46 N Y Frame Head? Give OOF Over 3ms Generate LOF Insert AIS Next process FoundA1,A2?Give OOFYOver 3msGenerate LOFNext processInsert AIS
47 2) DCC Data Communication Channel bytes:D1—D12 An info channel for OAM between NE-NED1-D3 is in Regenerator section(DCCR),D4-D12 is in Multiplex section(DCCM),OAM info includes: performance monitoring, alarms inquiry, command issue,etc.DCC channelNMUTP
48 3) Order wire bytes: E1,E2Each provides a 64kb/s order wire digital telephone.E1is for RS order wireE2 is for MS order wireE2can not be used by a REGs4) Bit interleaved parity byte:B1Performs real-time monitoring over the signal stream
50 If error blocks occurred B1 working mechanism:Detect B1Insert B1SDHEquipmentSendingSDHEquipmentReceivingSTM-NIf error blocks occurredproduce: RS-BBEperformance event
51 If error blocks occurred 5) Bit interleaved Parity B2 bytemonitor the error blocks of MSDetect B2Insert B2SDHEquipmentSendingSDHEquipmentReceivingSTM-NIf error blocks occurredproduce: MS-BBEperformance event
52 STM-N 6) Multiplex section Remote Error Indication byte:M1 Sent from receiver to senderInforms the sender: the error blocks detected by receiverthrough B2SDHEquipmentSenderReceiverSTM-NError blocks foundproduce: MS-BBEperformance eventSend M1byteM1 receivedproduce: MS-REI
53 7) Automatic Protection Switching(APS) bytes---K1,K2 Carries APS protocol for MSP switchingMS Remote Defect Indication byte:K2(b6-b8)=111, indicates that all “1” signals havebeen received, receiver will give MS-AIS alarmK2(b6-b8)=110, indicates that MS-RDI has beenreceived, which means the counter-part has receivedsignal deterioration, such as MS-AIS, RLOF etc.
54 K2 Detection Found 110 111 K2(b6-b8) Giving MS-AIS Sending back MS-RDI ProducingMS-RDI