Training Pdh Sdh Dwdm

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

3

3

3

3

3

3

3

4

4

4

4

4

4

4

4

Low order signals

3

2

1

4

3

2

Higher order signal

1

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 10 11 12 13 14 1516 17 18 19 20 21 22 23 24 2526 27 28 29 30 31

31 Channel

64KBit/s 31 Channels 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1516 17 18 19 20 21 22 23 24 2526 27 28 29 30 31

30 Channel

Framing 15 Channels

15 Channels

0 1 2 3 4 5 6 7 8 9 1011 12 1314 15 16 1718 19 2021 22 23 24 25 26 27 28 29 30 31

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 34

34 8

8 2

140 565

140 34

34 8

2 8

PDH 140 565

140 34

34 2

140 565

140 34

34 2

PDH Limitations Synchronisation The data is transmitted at regular intervals. With timing derived from the transmitters oscillator.

TX

RX

1

1 0

1 0

1 0

1 0

1 0

1 0

1 0

0

The data is sampled at the same rate as it is being transmitted.

PDH Limitations Synchronisation These bits are missed at the receiver end.

The data is transmitted at regular intervals. With timing derived from the transmitters oscillator.

TX

RX

1

1 0

1 0

1 0

1 0

1 0

1 0

1 0

0

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

RX

1

1 0

1 0

1 0

1 0

1 0

1 0

1 0

0

The data is sampled at a faster rate than the transmitter.

PDH Limitations Synchronisation TX MUX

RX HO TX

RX DE MUX

Timing extraction

TX HO RX

Timing extraction

DE MUX

HO RX

HO TX

MUX

PDH Limitations Synchronisation Justification bits

‘fast’ incoming 2Mbit/s channel 4

3

2

1

bit rate adaption

J

J

4

3

2

1

8Mbit/s

Master oscillator

3 ‘slow’ incoming 2Mbit/s channel

2

1

bit rate adaption

J

J

J

Justification bits

3

2

1

PDH Limitations Mux Mountain 140 565

565 140

140 34

140 34

34 8

34 8

2 8

8 2

Add / Drop

Increased equipment requirements Increased space on site. Increased spares requirements.

PDH Limitations Lack Of Traffic Resilience

140 565

Traffic Lost

140 565

Traffic Lost

PDH Limitations Limited Network Management

! DCN

565 140

Traffic Lost

Alarm reported. No diagnosis tools available. Maintenance staff sent to site.

DCN

140 565

Traffic Lost

PDH Limitations No Mid-Fibre Meet

Vendor A

565 140

Vendor B 140 565

SDH

The Synchronous Digital Hierarchy

SDH – Global Networks x24







DS1

DS2

DS3

1.5Mb/s

x4

6Mb/s

x7

45Mb/s

North American bit rates 64Kb/s (PCM)

1st Order

2nd Order

3rd Order

4th Order

European bit rates x32

2Mb/s

x4

8Mb/s

x4

34Mb/s

x4

140Mb/s

E1

E2

E3

E4



X





Not supported in SDH.

x4

565Mb/s

X Non standard

SDH – Network Topologies Line Systems

Terminal

Terminal

SDH – Network Topologies Line Systems

Terminal

Regenerator

Terminal

SDH – Network Topologies Ring Systems

ADM

ADM

ADM

ADM

STM-1

Overheads Pointers Payload Overheads

STM-1 270 Bytes 9 Bytes

261 Bytes

Overheads Pointers 9 Bytes

Payload Overheads

STM-1 270 Bytes

1891

2161

2162

2163

2164

2165

2166

2167

2168

2169

2170

2171

2172

2430

Overheads 1621

270

1351

2429

1081

269

Pointers 811

2428

6 5 4 3

541

Transmission time - 125 µseconds

268

12 11 10 9 8

2

271

Overheads 7

1

Payload 9 Bytes

261 Bytes 9 Bytes

STM-1 Overheads 9 Bytes

3 Bytes

Repeater Section Overheads

1 Byte

AU Pointers

5 Bytes

Multiplex Section Overheads

STM-1 Overheads

SDH

ADM

SDH

Regen

SDH

Regen

SDH

ADM

SDH

STM-1 Overheads

RS

SDH

ADM

SDH

RS

Regen

SDH

RS

Regen

SDH

ADM

SDH

STM-1 Overheads

MS

SDH

ADM

SDH

Regen

SDH

Regen

SDH

ADM

SDH

STM-1 Overheads

SDH

ADM

SDH

Regen

SDH POH

Regen

SDH

ADM

SDH

STM-1 Overheads

MS RS

SDH

ADM

SDH

RS

Regen

SDH POH

RS

Regen

SDH

ADM

SDH

STM-1 RS Overheads A1

A1

A1

A2

A2

B1

MD

MD

E1

D1

MD

MD

D2

A2

J0

X

X

MD

F1

X

X

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

SDH

Paris

SDH

SDH

ADM

SDH ADM

“London”

“Paris”

SDH Path Trace London

SDH

Paris

SDH

SDH

ADM

SDH ADM

“London”

“Paris”

“Paris”

“London”

SDH Path Trace London

Paris



“Paris”

SDH

SDH



“London”

SDH

ADM

SDH ADM

“London”

“Paris”

“Paris”

“London”

SDH Path Trace London

Paris

X



“London”

“Amsterdam”

SDH

SDH

!

SDH

ADM

SDH ADM

“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

ADM

SDH

Regen

SDH

Regen

SDH

ADM

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

SDH

ADM Gateway Node

SDH

DCC Channels

Regen

SDH

DCC Channels

Regen

SDH

ADM Gateway Node

SDH

STM-1 MS Overheads A1

A1

A1

A2

A2

A2

J0

X – Reserved bytes

B1

F1 RepeaterE1 Section Overheads

D1

D2

D3

AU Pointers B2

K1

K2

D4

D5

D6

D7

D8

D9

D10

D11

D12

S1

B2

Z1

B2

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 B1

A1

A1

A2

A2

A2

J0

F1 RepeaterE1 Section Overheads

D1

D2

D3

AU Pointers B2

K1

K2

D4

D5

D6

D7

D8

D9

D10

D11

D12

S1

B2

Z1

B2

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 B1

A1

A1

A2

A2

A2

J0

F1 RepeaterE1 Section Overheads

D1

D2

D3

AU Pointers B2

K1

K2

D4

D5

D6

D7

D8

D9

D10

D11

D12

S1

B2

Z1

B2

Z1

Z2

Z2

M1

E2

X

X

SDH Network Resilience ADM

Standby path

ADM

ADM

Active path

ADM

SDH Network Resilience ADM

Active path

ADM

ADM

Standby path

ADM

SDH Network Resilience Network Management Centre

ADM

Switch

Active path

ADM

ADM

Standby path

ADM

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 B1

A1

A1

A2

A2

A2

J0

F1 RepeaterE1 Section Overheads

D1

D2

D3

AU Pointers B2

K1

K2

D4

D5

D6

D7

D8

D9

D10

D11

D12

S1

B2

Z1

B2

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 B1

A1

A1

A2

A2

A2

J0

F1 RepeaterE1 Section Overheads

D1

D2

D3

AU Pointers B2

K1

K2

D4

D5

D6

D7

D8

D9

D10

D11

D12

S1

B2

Z1

B2

Z1

Z2

Z2

M1

E2

X

X

SDH Network Synchronisation Primary reference

ADM

ADM

Secondary reference

ADM

ADM

SDH Network Synchronisation Primary reference

ADM

ADM

Secondary reference

ADM

ADM

SDH Network Synchronisation Primary reference

ADM

ADM

Secondary reference

ADM

ADM

!

SDH Network Synchronisation Primary reference

ADM

ADM

Secondary reference

!

ADM

ADM

STM-1 MS Overheads The Z1 and Z2 bytes currently have no allocated function.

A1 B1

A1

A1

A2

A2

A2

J0

F1 RepeaterE1 Section Overheads

D1

D2

D3

AU Pointers B2

K1

K2

D4

D5

D6

D7

D8

D9

D10

D11

D12

S1

B2

Z1

B2

Z1

Z2

Z2

M1

E2

X

X

STM-1 MS Overheads The M1 byte is used as a remote error indicator.

A1 B1

A1

A1

A2

A2

A2

J0

F1 RepeaterE1 Section Overheads

D1

D2

D3

AU Pointers B2

K1

K2

D4

D5

D6

D7

D8

D9

D10

D11

D12

S1

B2

Z1

B2

Z1

Z2

Z2

M1

E2

X

X

Remote Error Indication B2 error detected

Multiplex section

SDH

ADM

SDH

Regen

SDH

Regen

Multiplex section

SDH

ADM

SDH

Remote Error Indication B2 error detected

Multiplex section

SDH

ADM

SDH

Regen

SDH

Regen

SDH

ADM

SDH

Multiplex section MS-REI received

MS-REI generated

STM-1 MS Overheads The E2 byte provides an EOW channel within the MS overhead.

A1 B1

A1

A1

A2

A2

A2

J0

F1 RepeaterE1 Section Overheads

D1

D2

D3

AU Pointers B2

K1

K2

D4

D5

D6

D7

D8

D9

D10

D11

D12

S1

B2

Z1

B2

Z1

Z2

Z2

M1

E2

X

X

SDH Pointers

Repeater Section Overheads

AU Pointers

Multiplex Section Overheads

SDH Pointers Payload area Repeater Section Overheads AU Pointers

Multiplex Section Overheads

Actual Payload Repeater Section Overheads AU Pointers

Multiplex Section Overheads Payload area

SDH Pointers Payload area Repeater Section Overheads AU Pointers

Multiplex Section Overheads

Actual Payload Repeater Section Overheads AU Pointers

Multiplex Section Overheads Payload area

SDH Pointers Payload area Repeater Section Overheads AU Pointers

Multiplex Section Overheads

Actual Payload Repeater Section Overheads AU Pointers

Multiplex Section Overheads Payload area

SDH Pointers Payload area Repeater Section Overheads AU Pointers

Multiplex Section Overheads

Actual Payload Repeater Section Overheads AU Pointers

Multiplex Section Overheads Payload area

SDH Pointers H1

H1

H1

H2

H2

9 Bytes

H2

H3

H3

H3

SDH Pointers H1

H1

H1

1 0 0 1 S S 1 1

H2

H2

H2

H3

H3

H3

1 0 0 1 S S 1 1

SDH Pointers H1

H1

H1

1 1 1 1 1 1 1 1

H2

H2

H2

H3

H3

H3

1 1 1 1 1 1 1 1

SDH Pointers H1

H1

NDF NDF NDF NDF S

H1

S

H2

I

D

H2

I

H2

D

I

H3

D

Pointer value

H3

I

D

H3

I

D

SDH Pointers H1

H1

H1

H2

H2

H2

H3

Payload

H3

H3

Past STM-1 STM16 Frame 4320 Bytes 144 Bytes

4176 Bytes

Overheads Pointers Payload

9 Bytes

Overheads

Past STM-1 Signal

Medium

Bit rate

E1

Electrical

2Mit/s

E3

Electrical

34Mit/s

E4

Electrical

140Mit/s

STM-1

Electrical / Optical 155Mbit/s

STM-4

Optical

622Mbit/s

STM-16

Optical

2.5Gbit/s

STM-64

Optical

10Gbit/s

STM-256 (future)

Optical

40Gbit/s

SDH Hierarchy STM-N

xN

AUG

AU-4

C-4 140M

VC-4 x3

x3

AU-3

TUG-3

x1

TU-3

VC-3 C-3 45M 34M

VC-3 x7 x7

TUG-2

x1

x3

Mapping

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

Aligning Multiplexing

x4

SDH Hierarchy C-4 140M

The Container isx3 the basic element of SDH. PayloadAU-3 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

C-3 45M 34M C-2 6M

C-12 2M

C-11 1.5M

SDH Hierarchy C-4 140M

VC-4 VC-3 x3

AU-3

Overhead bytes collectively known as the Lower Order Path Overhead are added to the container to form a Virtual Container.

C-3 45M 34M

VC-3

VC-2

C-2 6M

VC-12

C-12 2M

VC-11

C-11 1.5M

SDH Hierarchy C-4 140M

VC-4 VC-3 x3

The VC-11/12/2 POHAU-3 is comprised of : V5 - Indication and error monitoring. J2 - Path indication N2 - Tandem connection monitoring K4 - Automatic protection switching

C-3 45M 34M

VC-3

VC-2

C-2 6M

VC-12

C-12 2M

VC-11

C-11 1.5M

SDH Hierarchy C-4 140M

VC-4 VC-3

The VC-3/4 POH is comprised of :

x3

AU-3 J1 - Path indication 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

C-3 45M 34M

VC-3

VC-2

C-2 6M

VC-12

C-12 2M

VC-11

C-11 1.5M

SDH Hierarchy C-4 140M

VC-4 TU-3 A Pointer is added x3 to the Virtual Container to create a AU-3 Tributary Unit. 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

VC-3 C-3 45M 34M

VC-3

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

SDH Hierarchy C-4 140M

VC-4 TU-3 x3

AU-3

Four of the TU-11 Tributary Units can be multiplexed together to create A Tributary Unit Group-2 (TUG-2)

VC-3 C-3 45M 34M

VC-3

TUG-2

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

SDH Hierarchy C-4 140M

VC-4 TU-3 x3

AU-3

Alternatively three of the TU-12s can be multiplexed together to form the TUG-2

VC-3 C-3 45M 34M

VC-3

TUG-2

x3

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

SDH Hierarchy C-4 140M

VC-4 TU-3 x3

AU-3

Or the last way to construct the TUG-2 is to use a single TU-2.

VC-3 C-3 45M 34M

VC-3

TUG-2

x1

x3

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

SDH Hierarchy C-4 140M

VC-4 TUG-3 x3

AU-3

TU-3

VC-3 C-3 45M 34M

VC-3 x7

In a typical lower order SDH network carrying 2M traffic 7 TUG-2s will be multiplexed together to create a TUG-3.

TUG-2

x1

x3

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

SDH Hierarchy C-4 140M

VC-4 TUG-3 x3

AU-3

x1

TU-3

VC-3 C-3 45M 34M

VC-3 x7

Alternatively if the network is carrying 34M or 45m traffic the TUG-3 can be created from a single TU-3

TUG-2

x1

x3

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

SDH Hierarchy C-4 140M

VC-4 x3 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.

TUG-3

x1

TU-3

VC-3 C-3 45M 34M

VC-3 x7

TUG-2

x1

x3

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

SDH Hierarchy AU-4

C-4 140M

VC-4 x3

x3

AU-3

TUG-3

x1

TU-3

VC-3 C-3 45M 34M

VC-3 x7

A single VC-4 will have a pointer added to create an Administrative Unit, known as an AU-4

TUG-2

x1

x3

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

SDH Hierarchy AUG

AU-4

C-4 140M

VC-4 x3

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.

TUG-3

x1

TU-3

VC-3 C-3 45M 34M

VC-3 x7

TUG-2

x1

x3

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

SDH Hierarchy STM-N

xN

AUG

AU-4

C-4 140M

VC-4 x3

x3

AU-3 To create the SDH signal 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

TUG-3

x1

TU-3

VC-3 C-3 45M 34M

VC-3 x7

TUG-2

x1

x3

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

SDH Hierarchy STM-N

xN

AUG

AU-4

C-4 140M

VC-4 x3

TUG-3

x1

TU-3

VC-3 C-3 45M 34M

VC-3 x7

TUG-2 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

x1

x3

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

SDH Hierarchy STM-N

xN

AUG

AU-4

C-4 140M

VC-4 x3

TUG-3

x1

TU-3

VC-3 C-3 45M 34M

VC-3 x7 x7

TUG-2

x1

x3 Seven TUG-2s are multiplexed together to form a VC-3. This stage also adds a High Order Path Overhead.

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

SDH Hierarchy STM-N

xN

AUG

AU-4

C-4 140M

VC-4 x3

AU-3

TUG-3

x1

TU-3

VC-3 C-3 45M 34M

VC-3 x7 x7

TUG-2

x1

x3 A pointer is added to the VC-3 to create an AU-3. This pointer is know as an AU Pointer.

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

SDH Hierarchy STM-N

xN

AUG

AU-4

C-4 140M

VC-4 x3

x3

AU-3

TUG-3

x1

TU-3

VC-3 C-3 45M 34M

VC-3 x7 x7

TUG-2

x1

x3 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.

TU-2

VC-2

C-2 6M

TU-12

VC-12

C-12 2M

TU-11

VC-11

C-11 1.5M

x4

DWDM Within The Network Site A

ADM

ADM

ADM

Site D

Site C

Site B

ADM

DWDM Within The Network Site A

ADM

Network 1

Site D

ADM

ADM

Network 2

ADM

Site F

ADM

Site E

ADM

ADM

Site C

Site B

ADM

DWDM Within The Network Site A

Site C

Site B

Site D

M M

D

D

A

M

A

A

M

M

Network 2

D

D

D

A

D

M

Network 1

A

A

M

D

A

D

M

A

Site E

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

DWDM Coupler

Blue direction

Blue Amplifier

Red Amplifier

Blue Amplifier

Red Amplifier

DWDM Coupler

λ5 λ6 λ7 λ8 λ5 λ6 λ7 λ8

DWDM Equalisation

This wavelength has not been equalised

DWDM Equalisation λ5 TX

RX

High Order

ADM

RX

TX

TX

RX

High Order

ADM Low Order

RX

TX

Fibre Management Frame

Fibre Management Frame

λ8

DWDM Coupler

Red Amplifier

Low Order

λ4 λ7 Electrical/Fibre Management Frame

λ6

λ3 Fibre Management Frame

λ1 Electrical/Fibre Management Frame

Variable Output Transmitter

λ2

Variable Optical Attenuator

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.

f221

DWDM channel 1529.16nm ( f2 )

DWDM channel 1528.77nm ( f1 )

f112

Power

f(123)= f1+f2-f3

195.975

196

196.025

196.05

196.075

Frequency (THz)

196.1

196.125

196.15

196.175

Four Wave Mixing DWDM DWDM channel channel 1529.16nm 1528.77nm ( f3 ) ( f2 )

Power

DWDM channel 1529.55nm ( f1 )

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)

f321 f331

f331, f231

f332

f132 f312

f223

f112 f123 f213

f113