Introduction To Transmission

Introduction To Transmission

Introduction Telecommunications Communication over distance Transmission networks deal with getting information from one location to another.

Transmission Technologies FDM Frequency division multiplexing. TDM Time Division Multiplexing. DWDM Dense Wave Division Multiplexing

Time Division Multiplexing 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 4 3 2 1 4 3 2 1 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 Higher order signal Low order signals

Dense Wave Division Multiplexing One Wavelength ( λ )

Dense Wave Division Multiplexing

Dense Wave Division Multiplexing λ1 λ2 λ3 λ4 λ1 λ2 λ3 λ4 DWDM Signal λ5 λ6 λ7 λ8 λ5 λ6 λ7 λ8

Primary Rate Multiplexing Analogue Signal Sampling Quantising Encoding PCM Signal Multiplexing

Primary Rate Multiplexing Analogue signal Sampled at 8000 Hz

Primary Rate Multiplexing Quantising 10110010110010010101010 Encoding

Primary Rate Multiplexing 2MBit/s 0 1 2 3 4 5 6 7 8 9 10111213141516171819202122232425262728293031 64KBit/s 31 Channel 30 Channel 31 Channels 0 1 2 3 4 5 6 7 8 9 10111213141516171819202122232425262728293031 Framing 15 Channels 15 Channels 0 1 2 3 4 5 6 7 8 9 10111213141516171819202122232425262728293031 Framing Signalling

PDH Plesiochronous Digital Hierarchy Plesiochronous Almost Synchronous Multiplexing of 2Mbit/s signals into higher order multiplexed signals. Laying cable between switch sites is very expensive. Increasing traffic capacity of a cable by increasing bit rate. 4 lower order signals multiplexed into single higher order signal at each level.

PDH 140 565 140 565 140 34 140 34 834 348 28 82

PDH 140 565 140 565 140 34 140 34 234 342

PDH Limitations Synchronisation The data is transmitted at regular intervals. With timing derived from the transmitters oscillator. TX 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 RX The data is sampled at the same rate as it is being transmitted.

PDH Limitations Synchronisation The data is transmitted at regular intervals. With timing derived from the transmitters oscillator. These bits are missed at the receiver end. TX 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 RX The data is sampled at a slower rate than the transmitter.

PDH Limitations Synchronisation The data is transmitted at regular intervals. With timing derived from the transmitters oscillator. These bits are sampled twice at the receiver end. TX 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 RX The data is sampled at a faster rate than the transmitter.

PDH Limitations Synchronisation TX RX MUX HO TX HO RX DE MUX RX TX Timing extraction DE MUX HO RX HO TX MUX Timing extraction

PDH Limitations Synchronisation fast incoming 2Mbit/s channel Justification bits 4 3 2 1 bit rate adaption J J 4 3 2 1 Master oscillator 8Mbit/s slow incoming 2Mbit/s channel 3 2 1 bit rate adaption J J J 3 2 1 Justification bits

PDH Limitations Mux Mountain 140 565 140 565 140 34 140 34 348 34 8 82 28 Increased equipment requirements Increased space on site. Increased spares requirements. Add / Drop

Lack Of Traffic Resilience PDH Limitations 140 565 140 565 Traffic Lost Traffic Lost

PDH Limitations Limited Network Management! Alarm reported. No diagnosis tools available. Maintenance staff sent to site. DCN DCN 140 565 140 565 Traffic Lost Traffic Lost

No Mid-Fibre Meet PDH Limitations Vendor A Vendor B 140 565 140 565

SDH The Synchronous Digital Hierarchy

SDH Global Networks DS1 DS2 DS3 x24 1.5Mb/s x4 6Mb/s x7 45Mb/s North American bit rates 64Kb/s (PCM) 1 st Order 2 nd Order 3rd Order 4th Order European bit rates x32 2Mb/s x4 8Mb/s x4 34Mb/s x4 140Mb/s x4 565Mb/s E1 E2 E3 E4 X Not supported in SDH. X Non standard

SDH Network Topologies Line Systems Terminal Terminal

SDH Network Topologies Line Systems Terminal Regenerator Terminal

SDH Network Topologies Ring Systems

STM-1 Overheads Pointers Payload Overheads

STM-1 9 Bytes 270 Bytes 261 Bytes Overheads 9 Bytes Pointers Overheads Payload

STM-1 9 Bytes 270 Bytes 261 Bytes 270 269 268 12 11 10 9 8 7 6 5 4 3 2 1 9 Bytes 271 541 811 1081 1351 1621 1891 Overheads Pointers Overheads Payload 2430 2429 2428 2172 2171 2170 2169 2168 2167 2166 2165 2164 2163 2162 2161 Transmission time - 125 µseconds

STM-1 Overheads 9 Bytes 3 Bytes Repeater Section Overheads 1 Byte AU Pointers 5 Bytes Multiplex Section Overheads

STM-1 Overheads SDH SDH SDH SDH Regen Regen SDH

STM-1 Overheads RS RS RS SDH SDH SDH SDH Regen Regen SDH

STM-1 Overheads MS SDH SDH SDH SDH Regen Regen SDH

STM-1 Overheads SDH SDH SDH SDH Regen Regen SDH POH

STM-1 Overheads MS RS RS RS SDH SDH SDH SDH Regen Regen SDH POH

STM-1 RS Overheads A1 A1 A1 A2 A2 A2 J0 X X B1 MD MD E1 MD F1 X X D1 MD MD D2 MD D3 AU Pointers X Reserved bytes MD Media dependent Multiplex Section Overheads

STM-1 RS Overheads A1 A1 A1 A2 A2 A2 J0 B1 E1 F1 D1 D2 D3 AU Pointers The A1 & A2 bytes are used for frame alignment. Multiplex Section Overheads

STM-1 RS Overheads A1 A1 A1 A2 A2 A2 J0 B1 E1 F1 D1 D2 D3 AU Pointers The J0 byte is used to carry the RS Path Trace. This is a repetitively transmitted string used to identify the transmitting node. Multiplex Section Overheads

SDH Path Trace London Paris SDH SDH SDH SDH London Paris

SDH Path Trace London Paris SDH SDH SDH SDH London Paris Paris London

SDH Path Trace London Paris Paris London SDH SDH SDH SDH London Paris Paris London

SDH Path Trace London Paris X Amsterdam London SDH SDH! SDH SDH London Paris Paris London

STM-1 RS Overheads A1 A1 A1 A2 A2 A2 J0 B1 E1 F1 D1 D2 D3 AU Pointers The B1 byte is used for parity error checking. It carries the parity of the complete previous frame. Multiplex Section Overheads

STM-1 RS Overheads A1 A1 A1 A2 A2 A2 J0 B1 E1 F1 D1 D2 D3 AU Pointers The E1 byte provides a 64Kbit/s channel that can be used to carry voice for engineering order wire use. As this is in the RS overhead this channel can be accessed at any node. Multiplex Section Overheads

SDH EOW SDH SDH SDH SDH Regen Regen SDH

STM-1 RS Overheads A1 A1 A1 A2 A2 A2 J0 B1 E1 F1 D1 D2 D3 AU Pointers The F1 byte is reserved for user purposes. Multiplex Section Overheads

STM-1 RS Overheads A1 A1 A1 A2 A2 A2 J0 B1 E1 F1 D1 D2 D3 AU Pointers The D1, D2, & D3 bytes provides a 192Kbit/s channel that is used as a data communications channel between nodes for management purposes. Multiplex Section Overheads

SDH Management Network Management Centre DCN Network DCN Connection DCN Connection DCC Channels DCC Channels DCC Channels SDH SDH SDH SDH Regen Regen SDH Gateway Node Gateway Node

STM-1 MS Overheads X Reserved bytes A1 A1 A1 A2 A2 A2 J0 Repeater Section Overheads B1 E1 F1 D1 D2 D3 AU Pointers B2 B2 B2 K1 K2 D4 D5 D6 D7 D8 D9 D10 D11 D12 S1 Z1 Z1 Z2 Z2 M1 E2 X X

STM-1 MS Overheads The B2 byte allows for parity error checking within the MS overhead. Parity is computed from the previous frame with the exception of the RS overheads. A1 A1 A1 A2 A2 A2 J0 Repeater Section Overheads B1 E1 F1 D1 D2 D3 AU Pointers B2 B2 B2 K1 K2 D4 D5 D6 D7 D8 D9 D10 D11 D12 S1 Z1 Z1 Z2 Z2 M1 E2 X X

STM-1 MS Overheads The K1 & K2 bytes are for used for automatic protection switching. The are used to control the switches that occur on the network. A1 A1 A1 A2 A2 A2 J0 Repeater Section Overheads B1 E1 F1 D1 D2 D3 AU Pointers B2 B2 B2 K1 K2 D4 D5 D6 D7 D8 D9 D10 D11 D12 S1 Z1 Z1 Z2 Z2 M1 E2 X X

SDH Network Resilience Standby path Active path

SDH Network Resilience Active path Standby path

SDH Network Resilience Network Management Centre Switch Active path Standby path

STM-1 MS Overheads The Dx bytes are for used for a DCC channel within the MS overhead. 576Kbit/s are available for communication within this channel. A1 A1 A1 A2 A2 A2 J0 Repeater Section Overheads B1 E1 F1 D1 D2 D3 AU Pointers B2 B2 B2 K1 K2 D4 D5 D6 D7 D8 D9 D10 D11 D12 S1 Z1 Z1 Z2 Z2 M1 E2 X X

STM-1 MS Overheads The S1 byte is used for synchronisation messaging. It denotes the quality level of the synchronisation that can be derived from this incoming signal. A1 A1 A1 A2 A2 A2 J0 Repeater Section Overheads B1 E1 F1 D1 D2 D3 AU Pointers B2 B2 B2 K1 K2 D4 D5 D6 D7 D8 D9 D10 D11 D12 S1 Z1 Z1 Z2 Z2 M1 E2 X X

SDH Network Synchronisation Primary reference Secondary reference

SDH Network Synchronisation Primary reference Secondary reference

SDH Network Synchronisation Primary reference Secondary reference!

SDH Network Synchronisation Primary reference! Secondary reference

STM-1 MS Overheads The Z1 and Z2 bytes currently have no allocated function. A1 A1 A1 A2 A2 A2 J0 Repeater Section Overheads B1 E1 F1 D1 D2 D3 AU Pointers B2 B2 B2 K1 K2 D4 D5 D6 D7 D8 D9 D10 D11 D12 S1 Z1 Z1 Z2 Z2 M1 E2 X X

STM-1 MS Overheads The M1 byte is used as a remote error indicator. A1 A1 A1 A2 A2 A2 J0 Repeater Section Overheads B1 E1 F1 D1 D2 D3 AU Pointers B2 B2 B2 K1 K2 D4 D5 D6 D7 D8 D9 D10 D11 D12 S1 Z1 Z1 Z2 Z2 M1 E2 X X

Remote Error Indication B2 error detected Multiplex section SDH SDH SDH SDH Regen Regen SDH Multiplex section

Remote Error Indication B2 error detected Multiplex section SDH SDH SDH SDH Regen Regen SDH MS-REI received Multiplex section MS-REI generated

STM-1 MS Overheads The E2 byte provides an EOW channel within the MS overhead. A1 A1 A1 A2 A2 A2 J0 Repeater Section Overheads B1 E1 F1 D1 D2 D3 AU Pointers B2 B2 B2 K1 K2 D4 D5 D6 D7 D8 D9 D10 D11 D12 S1 Z1 Z1 Z2 Z2 M1 E2 X X

SDH Pointers Repeater Section Overheads AU Pointers Multiplex Section Overheads

SDH Pointers Repeater Section Overheads Payload area AU Pointers Multiplex Section Overheads Actual Payload Repeater Section Overheads AU Pointers Multiplex Section Overheads Payload area

SDH Pointers Repeater Section Overheads Payload area AU Pointers Multiplex Section Overheads Actual Payload Repeater Section Overheads AU Pointers Multiplex Section Overheads Payload area

SDH Pointers Repeater Section Overheads Payload area AU Pointers Multiplex Section Overheads Actual Payload Repeater Section Overheads AU Pointers Multiplex Section Overheads Payload area

SDH Pointers Repeater Section Overheads Payload area AU Pointers Multiplex Section Overheads Actual Payload Repeater Section Overheads AU Pointers Multiplex Section Overheads Payload area

SDH Pointers H1 H1 H1 H2 H2 H2 H3 H3 H3 9 Bytes

SDH Pointers H1 H1 H1 H2 H2 H2 H3 H3 H3 1 0 0 1 S S 1 1 1 0 0 1 S S 1 1

SDH Pointers H1 H1 H1 H2 H2 H2 H3 H3 H3 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

SDH Pointers H1 H1 H1 H2 H2 H2 H3 H3 H3 NDF NDF NDF NDF S S I D I D I D I D I D Pointer value

SDH Pointers H1 H1 H1 H2 H2 H2 H3 H3 H3 Payload

Past STM-1 STM16 Frame 4320 Bytes 144 Bytes 4176 Bytes Overheads 9 Bytes Pointers Payload Overheads

Past STM-1 Signal E1 E3 E4 STM-1 STM-4 STM-16 STM-64 STM-256 (future) Medium Electrical Electrical Electrical Electrical / Optical Optical Optical Optical Optical Bit rate 2Mit/s 34Mit/s 140Mit/s 155Mbit/s 622Mbit/s 2.5Gbit/s 10Gbit/s 40Gbit/s

SDH Hierarchy STM-N xn AUG AU-4 VC-4 C-4 140M x3 TUG-3 x1 TU-3 VC-3 x3 AU-3 VC-3 C-3 x7 45M 34M x7 TUG-2 x1 TU-2 VC-2 C-2 6M Mapping x3 TU-12 VC-12 C-12 2M Aligning Multiplexing x4 TU-11 VC-11 C-11 1.5M

SDH Hierarchy C-4 140M The Container is x3 the basic element of SDH. Payload signals that are to be transported across the SDH layer are mapped into the appropriate container. 1.5M maps into a C-11 2M maps into a C-12 6M maps into a C-2 34M maps into a C-3 45M maps into a C-3 140M maps into a C-4 AU-3 C-3 C-2 C-12 45M 34M 6M 2M C-11 1.5M

SDH Hierarchy VC-4 C-4 140M x3 AU-3 Overhead bytes collectively known as the Lower Order Path Overhead are added to the container to form a Virtual Container. VC-3 VC-3 C-3 VC-2 C-2 45M 34M 6M VC-12 C-12 2M VC-11 C-11 1.5M

SDH Hierarchy VC-4 C-4 140M x3 The VC-11/12/2 POH AU-3 is comprised of : VC-3 VC-3 C-3 45M 34M V5 - Indication and error monitoring. J2 - Path indication N2 - Tandem connection monitoring K4 - Automatic protection switching VC-2 VC-12 C-2 C-12 6M 2M VC-11 C-11 1.5M

SDH Hierarchy VC-4 C-4 140M The VC-3/4 POH is comprised of : x3 J1 - Path indication AU-3 B3 - Quality monitoring C2 - Container format G1 - Transmission error acknowledgment F2 - Maintenance H4 - Superframe indication F3 - Maintenance K3 - Automatic protection switching N1 - Tandem connection monitoring VC-3 VC-3 C-3 VC-2 C-2 VC-12 C-12 45M 34M 6M 2M VC-11 C-11 1.5M

SDH Hierarchy VC-4 C-4 140M TU-3 VC-3 A Pointer is added x3 to the Virtual Container to create a Tributary Unit. AU-3 VC-3 C-3 45M 34M This pointer functions in the same way as the pointer within the section overheads but is applied at a lower level and should not be confused with the higher level pointer. This lower level pointer is known as the TU Pointer TU-2 TU-12 VC-2 VC-12 C-2 C-12 6M 2M TU-11 VC-11 C-11 1.5M

SDH Hierarchy VC-4 C-4 140M TU-3 VC-3 x3 AU-3 VC-3 C-3 45M 34M Four of the TU-11 Tributary Units can be multiplexed together to create A Tributary Unit Group-2 (TUG-2) TUG-2 TU-2 VC-2 C-2 6M TU-12 VC-12 C-12 2M x4 TU-11 VC-11 C-11 1.5M

SDH Hierarchy VC-4 C-4 140M TU-3 VC-3 x3 AU-3 VC-3 C-3 45M 34M Alternatively three of the TU-12s can be multiplexed together to form the TUG-2 TUG-2 TU-2 VC-2 C-2 6M x3 TU-12 VC-12 C-12 2M x4 TU-11 VC-11 C-11 1.5M

SDH Hierarchy VC-4 C-4 140M TU-3 VC-3 x3 AU-3 VC-3 C-3 45M 34M Or the last way to construct the TUG-2 is to use a single TU-2. TUG-2 x1 TU-2 VC-2 C-2 6M x3 TU-12 VC-12 C-12 2M x4 TU-11 VC-11 C-11 1.5M

SDH Hierarchy VC-4 C-4 140M TUG-3 TU-3 VC-3 x3 AU-3 In a typical lower order SDH network carrying 2M traffic 7 TUG-2s will be multiplexed together to create a TUG-3. VC-3 C-3 x7 x1 TUG-2 TU-2 VC-2 C-2 45M 34M 6M x3 TU-12 VC-12 C-12 2M x4 TU-11 VC-11 C-11 1.5M

SDH Hierarchy VC-4 C-4 140M TUG-3 x1 TU-3 VC-3 x3 AU-3 Alternatively if the network is carrying 34M or 45m traffic the TUG-3 can be created from a single TU-3 VC-3 C-3 x7 x1 TUG-2 TU-2 VC-2 C-2 45M 34M 6M x3 TU-12 VC-12 C-12 2M x4 TU-11 VC-11 C-11 1.5M

SDH Hierarchy VC-4 C-4 140M x3 TUG-3 x1 TU-3 VC-3 x3 AU-3 3 TUG-3s can be multiplexed together to create a VC-4. When this is created another layer of path overhead is added. This is known as the High Order Path Overhead. VC-3 C-3 x7 x1 TUG-2 TU-2 VC-2 C-2 x3 TU-12 VC-12 C-12 45M 34M 6M 2M x4 TU-11 VC-11 C-11 1.5M

SDH Hierarchy AU-4 VC-4 C-4 140M x3 TUG-3 x1 TU-3 VC-3 x3 AU-3 A single VC-4 will have a pointer added to create an Administrative Unit, known as an AU-4 VC-3 C-3 x7 x1 TUG-2 TU-2 VC-2 C-2 45M 34M 6M x3 TU-12 VC-12 C-12 2M x4 TU-11 VC-11 C-11 1.5M

SDH Hierarchy AUG AU-4 VC-4 C-4 140M x3 TUG-3 x1 TU-3 VC-3 x3 AU-3 The Administrative Unit Group is created when multiplexing several Administrative Units. Using this route through the hierarchy only one AU-4 is needed to create the AUG, no processing is performed or overhead added. VC-3 C-3 x7 x1 TUG-2 TU-2 VC-2 C-2 x3 TU-12 VC-12 C-12 45M 34M 6M 2M x4 TU-11 VC-11 C-11 1.5M

SDH Hierarchy STM-N xn AUG AU-4 VC-4 C-4 140M x3 TUG-3 x1 TU-3 VC-3 x3 To create the SDH signal AU-3 several AUGs are multiplexed together with the section overheads added to create the STM-N signal. For example, one AUG would be used in an STM-1, whereas sixteen AUGs would be used to create an STM-16 signal VC-3 C-3 x7 x1 TUG-2 TU-2 VC-2 C-2 x3 TU-12 VC-12 C-12 45M 34M 6M 2M x4 TU-11 VC-11 C-11 1.5M

SDH Hierarchy STM-N xn AUG AU-4 VC-4 C-4 140M x3 TUG-3 x1 TU-3 VC-3 VC-3 C-3 x7 x1 TUG-2 TU-2 VC-2 C-2 45M 34M 6M There is an alternative way to create the signal, although the one shown here is typically used. The alternative route is mainly used when interconnecting with SONET networks or for SDH radio applications where lower bit rate STM-0 / OC-1s are used as the building block instead of STM-1 x3 x4 TU-12 TU-11 VC-12 VC-11 C-12 C-11 2M 1.5M

SDH Hierarchy STM-N xn AUG AU-4 VC-4 C-4 140M x3 TUG-3 x1 TU-3 VC-3 VC-3 C-3 x7 x7 x1 TUG-2 TU-2 VC-2 C-2 45M 34M 6M x3 TU-12 VC-12 C-12 2M Seven TUG-2s are multiplexed together to form a VC-3. This stage also adds a High Order Path Overhead. x4 TU-11 VC-11 C-11 1.5M

SDH Hierarchy STM-N xn AUG AU-4 VC-4 C-4 140M x3 TUG-3 x1 TU-3 VC-3 AU-3 VC-3 C-3 x7 x7 x1 TUG-2 TU-2 VC-2 C-2 45M 34M 6M x3 TU-12 VC-12 C-12 2M A pointer is added to the VC-3 to create an AU-3. This pointer is know as an AU Pointer. x4 TU-11 VC-11 C-11 1.5M

SDH Hierarchy STM-N xn AUG AU-4 VC-4 C-4 140M x3 TUG-3 x1 TU-3 VC-3 x3 AU-3 VC-3 C-3 x7 45M 34M x7 TUG-2 x1 TU-2 VC-2 C-2 6M Three AU-3s can be multiplexed together to form an AUG if an STM-1 or higher is going to be created. The AUG then has the section overheads added. x3 x4 TU-12 TU-11 VC-12 VC-11 C-12 C-11 2M 1.5M

DWDM Within The Network Site A Site B Site C Site D

DWDM Within The Network Site A Site B Network 1 Site C Site D Network 2 Site E Site F

DWDM Within The Network Site A Site C Site E Network 1 Network 2 Site B Site D Site F

Protocol Independent DWDM networks are protocol independent. They transport wavelengths of light and do not operate at the protocol layer. SDH SONET Ethernet Digital Video.

DWDM Amplifiers Red direction λ1 λ2 λ3 λ4 λ1 λ2 λ3 λ4 λ5 λ6 λ7 λ8 DWDM Coupler Red Amplifier Blue Amplifier Red Amplifier Blue direction Blue Amplifier DWDM Coupler λ5 λ6 λ7 λ8

DWDM Equalisation This wavelength has not been equalised

DWDM Equalisation Electrical/Fibre Management Frame Electrical/Fibre Management Frame Low Order Low Order TX TX TX TX High Order RX RX High Order RX RX Fibre Management Frame Fibre Management Frame λ1 λ5 λ2 λ6 Fibre Management Frame Variable Optical Attenuator λ3 λ4 λ7 λ8 DWDM Coupler Red Amplifier Variable Output Transmitter

Optical Dispersion

Chromatic Dispersion

Polarisation Mode Dispersion While a light pulse is not itself polarised, it consists of two perpendicularly polarised components.

Polarisation Mode Dispersion An imperfectly shaped core can affect one of the components of the pulse Impurities within the core can delay the arrival of one of the components.

Four Wave Mixing With two wavelength within the fibre, two additional wavelengths are generated. DWDM channel DWDM channel 1529.16nm 1528.77nm f 221 ( f2 ) ( f 1 ) f 112 f (123) = f 1 +f 2 -f 3 Power 195.975 196 196.025 196.05 196.075 196.1 196.125 196.15 196.175 Frequency (THz)

Four Wave Mixing DWDM channel 1529.55nm ( f 1 ) DWDM channel 1529.16nm ( f 2 ) DWDM channel 1528.77nm ( f 3 ) Power DWDM Channels FWM Channels 195.9 195.9 195.9 196 196 196 196 196.1 196.1 196.1 196.1 196.2 196.2 196.2 196.2 Frequency (THz) f 321 f 331, f 332 f 132 f 223 f 112 f 331 f 231 f 312 f 123 f 113 f 213