S-108.199 OPTICAL COMMUNICATIONS AND INSTRUMENTS SDH and...
Transcript of S-108.199 OPTICAL COMMUNICATIONS AND INSTRUMENTS SDH and...
1 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
S-108.199 OPTICAL COMMUNICATIONS AND INSTRUMENTS
SDH and WDM, 10.3.2004
Antti Pietiläinen
2 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Trend towards simplification of protocol stacks
WDM/Optical Networking LayerWDM/Optical Networking Layer
SDH TransportSDH Transport ATMATM IPIP Digital SignalDigital Signal(FR, FOTS, PDH)(FR, FOTS, PDH)
ATMATM IPIP
IPIPPDHPDH
FRFR
Transport/Application LayerTransport/Application Layer
TimeTime
CurrentSystems Current
R&DFuture
Deployment (3-6 yrs)
From this
Towards this
How the future of layering looked 4 years ago
3 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
PDHPDH
Trend towards simplification of protocol stacks
OTNOTN
SDH TransportSDH Transport EthernetEthernet IPIP
ATMATM IPIP
IPIP FRFR
Transport/Application LayerTransport/Application Layer
CurrentSystems Current
R&Dand future deplyment
From this
Towards this
How the future looks now
GFPGFP
GFPGFP
OTNOTN
4 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Acronyms of previous page
• IP = Internet protocol
• FR = frame relay
• PDH = plesiochronous digital hierarchy
• ATM = asynchronous transfer mode
• SDH = synchronous digital hierarchy
• GFP = generic framing procedure
• WDM = wavelength division multiplexing
• OTN = optical transport network
5 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Digital signal
• Analog telephone connection carries the frequencies between 300 Hz and 3400 Hz.
• The signal can be converted into a digital signal by sampling 8-bit samples at 8000 samples/s.
• Channels are multiplexed together using time domain multiplexing. Each channel gets one-byte timeslot in every frame. Frame rate is 8000 frames per second. 30 or 31 channels fit into 32 time slots where one or two time slots are used for frame alignment and signaling. The total bit rate of E1 frame is 2.048 Mbit/s.
• The ANSI frame T1 includes 24 64-kbit/s channels. A single frame has 24 x 8 =192 payload bits and one framing bit.
• The 64-kbit/s channels collected into one E1 or T1 are digitized using the same clock. Thus, the channels are synchronized with each other.Ramaswami has assumed the framing bit as a stuffing bit, which could accommodate bit rate differences, so p. 365 has an error.
• However, individual E1 and T1 signals are not necessarily synchronized with each other.
6 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Short history multiplexing hierarchy, PDH
• PDH – plesiochronous digital hierarchy. Multiplexing signals, which are running at almost the same speed.
• First standards in the second half of 1960s.• Tributaries and higher order bit streams are allowed to deviate from a
pre-defined bit rate by a specified amount, for example at 2 Mbit/s the value is 50 ppm.
• Justification (bit stuffing) process is therefore required, which brings all the tributaries up to the same bit rate before multiplexing takes place.
97728 Mbit/s139264 Mbit/s139264 Mbit/s432064 Mbit/s34368 Mbit/s44736 Mbit/s36312 Mbit/s8448 Mbit/s6312 Mbit/s2
1544 Mbit/s2048 Mbit/s1544 Mbit/s1
0.064 Mbit/s0.064 Mbit/s0.064 Mbit/s0
JapanEurope
E
North America
DS or T
Level
7 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
PDH multiplexer mountain
• When a signal is demultiplexed, the stuffed bits are removed. Each level knows how to demultiplex the next level.
• To extract a 2-Mbit/s signal from a high- bit rate stream, a “multiplexer mountain” is required.
34 -140 MUX
34 -140 MUX
8 -32
MUX
8 -32
MUX2 -8
MUX
2 -8
MUX
140 Mbit/s 140 Mbit/s
2 Mbit/s Drop/Add
34 Mbit/s
8 Mbit/s
2 Mbit/s
8 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Foundation of SDH/SONET
• Developed during late 1980s
• SDH - Synchronous digital hierarchy (Europe, Japan, Intercontinentalcables, ITU recommendation)
• SONET – Synchronous optical network (North America, ANSI standard)
• All clocks in a network are synchronized to a single master clock.
• All bit rates are integer multiples of the basic bit rates and no bit stuffing is required.
• A lower bit rate stream can be extracted from a multiplexed SONET/SDH stream in a single step.
9 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Other advantages of SONET/SDH
• Management• Incorporates extensive management information for managing the
network• Performance monitoring• Identification of connectivity and traffic type• Identification and reporting of failures• Data communication channel
• Interoperability• PDH standard did not specify standard format on the transmission link.
Therefore different vendors used different line coding, optical interfaces etc. In SDH standardization is more complete. However, there are still some problems in connecting equipment from different vendors
• Network availability• Incorporate specific network topologies and specific protection
techniques and associated protocols to provide high availability. Restoration time after failure can be less than 60 ms.
10 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Multiplexing
• The basic SONET bit rate is 51840 Mbit/s and the basic SDH bit rate is 155.420 Mbit/s. The highest bit rate standardized so far is 39813.120 Mbit/s.
STM-2561327.10438486.01639813.120STS-768OC-768
STM-64331.7769621.5049953.280STS-192OC-192
STM-1682.9442405.3762488.320STS-48OC-48
STM-420.736601.344622.080STS-12OC-12
STM-15.184150.336155.520STS-3OC-3
-1.72850.11251.840STS-1OC-1
SDH Equivalent
Overhead Rate (Mbps)
Payload Rate (Mbps)
Line Rate (Mbps)
Electrical Level
(ANSI)
Optical Level
(ANSI)
11 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
SDH Multiplexing structure (ITU-T G.707)
STM-256
STM-64
STM-16
STM-4
STM-1
STM-0
AUG-256
AUG-64
AUG-16
AUG-4
AUG-1
AUG-4-256c
AUG-4-64c
AUG-4-16c
AUG-4-4c
AU-4
AU-3 VC-3
VC-4
VC-4-256c
VC-4-64c
VC-4-16c
VC-4-4c
C-4-256c
C-4-64c
C-4-16c
C-4-4c
C-4
C-3
C-2
C-12
C-11
VC-3
VC-2
VC-12
VC-11
TU-3
TU-2
TU-12
TU-11
TUG-2
TUG-3
Pointer processingMultiplexingAligningMapping
x 4
x 3
x 1x 7
x 7
x 3x 1
x 3
x 4
x 4
x 4
x 4
x 1
x 1
x 1
x 1
x 1
x 1 x 1
x 1
x 1
x 1
x 1
DS1 1.5M
E1 2M
DS2 6M
DS3 45ME3 34M
DS4 139ME4 139M
SONET
SONET
ETSI
ETSI
SONET
SONET
ETSISONET
SONETETSIETSI
ETSI
149.8M
599.04M
2396.16M
9584.64M
38338.56M
150.336M
12 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Procedures in SDH framing
• SDH mapping: A procedure by which tributaries are adapted into Virtual Containers at the boundary of an SDH network.
• SDH multiplexing: A procedure by which multiple lower order path layer signals are adapted into a higher order path or the multiple higher order path layer signals are adapted into a multiplex section.
• SDH aligning: A procedure by which the frame offset information is incorporated into the Tributary Unit or the Administrative Unit when adapting to the frame reference of the supporting layer.
13 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Cross-connecting VCs
• VCs arrive inside STMs into a cross connect. The VCs are recovered and cross-connected to another port and aligned into another STMs.
Connectionpoints
Connectionpoints
flexiblematrix
Out 1
Out 2
In 1
In 2
STM-1
STM-4 STM-1
STM-4
VC-4 pipes : continuous streamof virtual containers
1
4
1
32
1
31
2
4
14 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Aligning virtual containers into TU (transport unit) or AU (administrative unit)
• Virtual container is a frame (frame rate 8000 frames/s).
• The virtual containers are synchronous because the clock is derived from the master clock of the network.
• However, virtual containers may travel a long way and go through many links.
• Each link transmits frames between two nodes at a frame rate of 8000 frames/s. The bit rate of all consecutive links may be the same but the frame boundaries occur at different moments. Thus, VCs float inside the TUs or AUs and a pointer indicates where the starting point of a VC is within a TU or AU
TU-12 frame
TU-12 frame
VC-12 frame
Pointer
Pointer
15 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Justification bytes and pointer slip
• Sometimes the whole network is not synchronized and VCs may be running at a slightly faster or slower rate than the TU or AU.
• Therefore the pointer must slip one byte every now and then. Forallowing slightly faster rate there has to be an extra byte in the TU or AU that may take the last byte of a frame when there is a negative slip where the VC shifts to a location one byte earlier than before and would otherwise overwrite a byte. Correspondingly, in the case of positive split, one byte in the TU or AU is jumped over and left empty.
16 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Building an STM-1 from E2s
C-122.048 Mbit/s tributary signal in
Add stuffing bits, 128 kbit/s
VC-12 Add VC-12 POH, 64 kbit/s(lower order VC POH)
Mapping
Alignment of VC-12 into TU-12 and add 2-byte TU pointer+justification byte + one empty byte for every 4 frames, 64 kbit/s
Multiplex x3
Multiplex x7
Multiplex x3 + add VC-4 POH, 576 kbit/s(higher order VC POH)
Alignment of VC-4 into AU-4and add AU pointer + 3 justification bytes
TU-12
TUG-2TUG-3
VC-4
AU-4
AUG-1 Multiplex x1
STM-1 Multiplex x1 + MSOH, 2.88 Mbit/s, and RSOH, 1.728 Mbit/s
STM = Synchronous transfer moduleMSOH = Multiplexer section overheadRSOH = Regenerator section overheadAUG = Administrative unit groupAU = Administrative unitTUG = Tributary unit groupTU = Tributary unitPOH = Path overheadVC = Virtual containerC = Container
17 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Moving pointer in a cross connect
TU-12 frame
TU-12 frame
VC-12 frame
Pointer
Multiplex section n
TU-12 frame
TU-12 frame
VC-12 frame
Pointer
Pointer
Multiplex section n + 1
18 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Recovering an E2 from an STM-1
C-122.048 Mbit/s tributary signal out
Remove stuffing bits
VC-12 Read VC-12 POH
Recovery of VC-12 from TU-12(read TU pointer + strip justification byte
Demultiplex ÷ 3
Demultiplex ÷7
Demultiplex ÷3 read VC-4 POH
Recovery of VC-4 from AU-4(read AU pointer + strip justification bytes)
TU-12
TUG-2TUG-3
VC-4
AU-4
AUG-1 Demultiplex ÷ 1
STM-1 Demultiplex ÷ 1, read MSOH and RSOH
STM = Synchronous transfer moduleMSOH = Multiplexer section overheadRSOH = Regenerator section overheadAUG = Administrative unit groupAU = Administrative unitTUG = Tributary unit groupTU = Tributary unitPOH = Path overheadVC = Virtual containerC = Container
19 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
SDH sublayers
Terminalmultiplexer
Terminalmultiplexer
Add/dropmultiplexerRegenerator
Regeneratorsection
Multiplexersection
(VC) path
Tributaries Tributaries
Section
Line
Path
SONET:
•Path, Multiplexer section and Regenerator section each carry management information, which is terminated at the endpoints of the path or section.
20 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
STM-1 frame• The resulting STM-1 frame
1
2
3
4
5
6
7
8
9
1 2 3 4 65 7 8 9 10
125 µs
AU pointers
Multiplex sectionoverhead
Regenerator sectionoverhead
270 bytes
21 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
SDH physical interface example
• V-16.2
STM-16, 2.5 G1550 nm
• Fiber type G.652 standard single-mode fiber
• Loss 22-33 dB
• Allowed dispersion 2400 ps/nm
• Fiber has attenuation of <0.275 dB/km and dispersion 17 ps/nm/km
22 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Optical communications cumulative market size• The hype reached its peak in 2000• Current estimates indicate solid but lower growth
1990 1995 2000 2005 2010
CumulativeMarket
size
Core wave
Metro wave
Access wave
Estimate 2000
Estimate 2004
23 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Laboratory experiments conquering dispersion limits
• Chromatic dispersion limit using standard single-mode fiber: 2.5 Gbit/s -1000 km, 10 Gbit/s - 60 km. Most fiber laid in the ground is standard single mode fiber.
• 1 Terabit/s (100 × 10 Gbit/s) transmission over 7300 km non-zero dispersion shifted fiber, Electronics Lett. 35 (1999) p.2212.
• 1.28 Tbit/s (32 x 40 Gbit/s) over 1000 km non-dispersion-shifted fiber using dispersion compensation fiber, Electronics Lett. 37 (2001) p.43.
• DWDM 40 x 40G transmission over trans-Pacific distance (10,000 km) using CSRZ-DPSK, enhanced FEC and all-Raman amplified 100 kmUltraWave™ fiber spans,” Technical Digest of OFC 2003, post-deadline paper, PD18, (2003).
24 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
WDM layer below SDH layer• WDM has introduced functionality, such as optical add/drop multiplexers
and optical regeneration below SDH in layered model.
• Optical transport network (OTN) layer serves SDH client layer.
Path LAYER
Multiplex Section LAYER
Regenerator Section LAYER
Optical Channel LAYER
Optical Multiplex Section LAYER
Optical Transmission Section LAYER
Fibre LAYER
TDMElectricalLayers
WDMOpticalLayers
25 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Optical sections within a single SDH regeneration section
OPTICAL MULTIPLEX
SECTION
OPTICAL MULTIPLEX
SECTION
OPTICAL TRANSMISSION
SECTION
TRIBUTARYSIGNALS
WDMMULTI-
PLEXER
WDMDEMULTI-PLEXER
OPTICAL CROSS-CONNECT
OPTICALAMPLIFIER
OPTICALAMPLIFIER
TRIBUTARYSIGNALS
Optical Channel
SDH REGENERATOR SECTION
OPTICAL TRANSMISSION
SECTION
OPTICAL TRANSMISSION
SECTION
26 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Optical channel frame• STM-16 + FEC = OTU1, STM-64 + FEC = OTU2, STM-256 + FEC = OTU3
• Other payload mappings available, for example Generic framing procedure.
OTU type OTU nominal bit rate OTU bit rate tolerance
OTU1 255/238 × 2 488 320 kbit/s
±20 ppmOTU2 255/237 × 9 953 280
kbit/s
OTU3 255/236 × 39 813 120 kbit/s
NOTE – The nominal OTUk rates are approximately: 2 666 057.143 kbit/s (OTU1), 10 709 225.316 kbit/s (OTU2) and 43 018 413.559 kbit/s (OTU3).
OTU = Optical channel transport unit, FEC = Forward error correction
Source ITU-T G.709 (03/2003)
27 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Optical transport network functionality
• Service provisioning
• Protection
• Performance monitoring
• Wavelength conversion
• Multiplexing and grooming
• Bit rate transparency (with provisions)• High bit rate more sensitive to dispersion and attenuation• Very high bit rate consumes more optical bandwidth
28 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
WDM network elements
• Optical add/drop multiplexers (OADM)
Ring network Linear network
29 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
WDM network elements
• Optical crossconnects (OXC)
Mesh
OADM
OADM
OADM
OXC
OXC
30 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Protection at different optical layers
Trail Protection Subnetwork Protection
1 + 1 1 : 1 m : n 1 + 1 1 : 1 m : n
Optical Channel Layer (end-to-endtrail, ffs) (section)
Optical MultiplexSection Layer
(meshednetworks)
(ringprotection)
(ringprotection)
(meshednetworks)
(ringprotection)
(ringprotection)
Optical TransmissionSection Layer
OADMOADM
OADM
OXC
OXC
• Optical channel protection• A backup route is planned for a path
• Optical multiplex section protection• A link between two OXCs has a backup
route.
31 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
OADM architectures
• Parallel where all the wavelengths are separated and multiplexed back
λ1, λ2, …, λw
λ1, λ2, …, λw
λ1
λ2
λw
λ1
λ2
Drop Add
32 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
OADM architectures
• Modular version of parallel architecture
λ1, λ2, …, λw
λ1, λ2, …, λw
λ1 λ2
Band 4
Band 3
Band 2
Band 1
Drop Add
33 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
OADM architectures
• Serial
λ1, λ2, …, λw λ1, λ2, …, λw
λ1Drop Add λ2 λ3
Drop Addλ1, λ2, λ3
λ1, λ2, …, λw λ1, λ2, …, λw
• Band drop
34 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
OADM architectures
• Reconfigurable parallel architecture
λ1, λ2, …, λN
λ1λ2λN
λ1, λ2, …, λN
Optical switch
35 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Optical crossconnect (OXC)
OXC
OLT (optical line terminal)
36 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Different scenarios for OXC deployment
Opticalcore
OLT (optical line terminal)• Electrical switch core
O E OO E O
O E OO E O
OO
OO
EE
EE
OO
OO
E OE O
E OE O
EE
EE
OO
OO
O E OO E O
O E OO E O
OO
OO
EE
EE
OO
OO
E OE O
E OE O
EE
EE
OO
OO
OO
OO
OO
OO
• Optical switch core surrounded by O/E/O converters
Electrical core
37 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Different scenarios for OXC deployment
OLT
• Optical switch core connected directly to transponders in OLT
O E OO E O
O E OO E O
OO
OO
EE
EE
OO
OO
• Optical switch core directly connected to multiplexer in OLT
Optical core
Optical core
OLT
38 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Optical core wavelength plane OXC
Local add
λ1, λ2, λ3
λ1, λ2, λ3
λ1, λ2, λ3λ1, λ2, λ3
λ1
λ2
λ3λ1 λ1λ3λ2 λ2
Local drop
39 © NOKIA S_108_199_10_3_2004.ppt / 10.3.2004 / APi
Reading instructions
• SDH, pp. 364-381. SDH multiplexing hierarchy instead of SONET multiplexing hierarchy.
• WDM, pp. 403-430 and optical network layering and the principle of optical protection.