Optical Networking Technologies

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Optical Networking Technologies
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Outline

• Introduction to Fiber Optics
• Passive Optical Network (PON) point-to-point
  fiber networks, typically to a home or small
  business
• SONET/SDH
• DWDM (Long Haul)

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Optical Transmission
optical signal
electrical signal
electrical signal
Optical Fibre Transmission System
Optical Fibre Transmission System

• Advantages of optical transmission
• Longer distance (noise resistance and less
  attenuation)
• Higher data rate (more bandwidth)
• Lower cost/bit

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Optical Networks

• Passive Optical Network (PON)
• Fiber-to-the-home (FTTH)
• Fiber-to-the-curb (FTTC)
• Fiber-to-the-premise (FTTP)
• Metro Networks (SONET)
• Metro access networks
• Metro core networks
• Transport Networks (DWDM)
• Long-haul networks

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Optical Network Architecture
Long Haul Network
DWDM
SONET
Metro Network
Metro Network
transport network
PON
Access Network
Access Network
Access Network
Access Network
CPE (customer premise)
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All-Optical Networks

• Most optical networks today are EOE
  (electrical/optical/electrical)
• All optical means no electrical component
• To transport and switch packets photonically.
• Transport no problem, been doing that for years
• Label Switch
• Use wavelength to establish an on-demand
  end-to-end path
• Photonic switching many patents, but how many
  products?

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Optical 101

• Wavelength (?) length of a wave and is measured
  in nanometers, 10-9m (nm)
• 400nm (violet) to 700nm (red) is visible light
• Fiber optics primarily use 850, 1310, 1550nm
• Frequency (f) measured in TeraHertz, 1012 (THz)
• Speed of light 3108 m/sec

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Optical Spectrum
l
IR
UV
125 GHz/nm
Visible
850 nm
1550 nm
1310 nm

• Light
• Ultraviolet (UV)
• Visible
• Infrared (IR)
• Communication wavelengths
• 850, 1310, 1550 nm
• Low-loss wavelengths

Bandwidth
1550nm 193,548.4GHz
1551nm 193,424.6GHz
1nm 125 GHz
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Optical Fiber
Core
Cladding

• An optical fiber is made ofthree sections
• The core carries thelight signals
• The cladding keeps the lightin the core
• The coating protects the glass

Coating
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Optical Fiber (cont.)

• Single-mode fiber
• Carries light pulses by laser along single path
• Multimode fiber
• Many pulses of light generated by LED travel at
  different angles

SM core8.3 cladding125 µm MM core50 or 62.5
cladding125 µm
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Bending of light ray
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Figure 7.12 Propagation modes
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Figure 7.13 Modes
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Figure 7.14 Fiber construction
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Figure 7.15 Fiber-optic cable connectors
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Figure 7.16 Optical fiber performance
Note loss is relatively flat
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Fiber Installation Support cable every 3 feet
for indoor cable (5 feet for outdoor) Dont
squeeze support straps too tight. Pull cables by
hand, no jerking, even hand pressure. Avoid
splices. Make sure the fiber is dark when
working with it. Broken pieces of fiber VERY
DANGEROUS!! Do not ingest!

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Optical Transmission Effects
Attenuation
Dispersion
Nonlinearity
Distortion
Waveform After 1000 Km
Transmitted Data Waveform
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Optical Transmission Effects
Attenuation Loss of transmission power due to
long distance
Dispersion and Nonlinearities Erodes clarity
with distance and speed
Distortion due to signal detection and recovery
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Transmission Degradation
Ingress Signal
Egress Signal
Loss of Energy
Optical Amplifier
Shape Distortion
Dispersion Compensation Unit (DCU)
Phase Variation
t
t
Loss of Timing (Jitter)
Optical-Electrical-Optical (OEO) cross-connect
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Passive Optical Network (PON)

• Standard ITU-T G.983
• PON is used primarily in two markets residential
  and business for very high speed network access.
• Passive no electricity to power or maintain the
  transmission facility.
• PON is very active in sending and receiving
  optical signals
• The active parts are at both end points.
• Splitter could be used, but is passive

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Passive Optical Network (PON)
OLT Optical Line Terminal ONT Optical Network
Terminal
Splitter (132)
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PON many flavors

• ATM-based PON (APON) The first Passive optical
  network standard, primarily for business
  applications
• Broadband PON (BPON) the original PON standard
  (1995). It used ATM as the bearer protocol, and
  operated at 155Mbps. It was later enhanced to
  622Mbps.
• ITU-T G.983
• Ethernet PON (EPON) standard from IEEE Ethernet
  for the First Mile (EFM) group. It focuses on
  standardizing a 1.25 Gb/s symmetrical system for
  Ethernet transport only
• IEEE 802.3ah (1.25G)
• IEEE 802.3av (10G EPON)
• Gigabit PON (GPON) offer high bit rate while
  enabling transport of multiple services,
  specifically data (IP/Ethernet) and voice (TDM)
  in their native formats, at an extremely high
  efficiency
• ITU-T G.984

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xPON Comparison
BPON EPON GPON
Standard ITU-T G.983 IEEE 803.2ah ITU-T G.984
Bandwidth Down 622M Up 155M Symmetric 1.25G Down 2.5G Up 2.5G
Downstream ? 1490 1550 1550 1490 1550
Upstream ? 1310 1310 1310
Transmission ATM Ethernet ATM, TDM, Ethernet
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PON Case Study (BPON)
Optical Network Terminal (ONT) (customer premise)
Optical Line Terminal (OLT) (Central Office)
Two Ethernet ports One T1/E1 port Optical
transport 622M bps
T1/E1
802.3
Packet Core (IPoATM)
CES
RFC2684
AAL1
AAL5
SAR/CS
ATM
TDM Core (PSTN)
PON (G.983)
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GPON
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EPON Evolution
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(No Transcript)
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(No Transcript)
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(No Transcript)
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EPON Downstream
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EPON Upstream
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SONET in Metro Network
Long Haul (DWDM) Network
Core Router
Metro SONET Ring
Voice Switch
Access Ring
Access Ring
Access Ring
T1
T1
PBX
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IP Over SONET
SONET is designed for TDM traffic, and todays
need is packet (IP) traffic. Is there a better
way to carry packet traffic over SONET?
T1
OC-3
DS3
IP
802.3
IP
RFC2684
IP
IP
????
AAL5
PPP
802.3
ATM
GFP
RFC1619
SONET
SONET
SONET
SONET
SONET
TDM Traffic
GFP Generic Frame Procedure
RFC 2684 Encapsulate IP packet over ATM RFC
1619 Encapsulate PPP over SONET
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ATM over SONET (STS-3c)
Cell 1
Cell 2
Cell 3
260 columns (octets)
OH
Cell 1
Cell 2
Cell 3
9 rows
STS-3c Envelope
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PPP over SONET

• RFC 1619 (1994)
• The basic rate for PPP over SONET is STS-3c at
  155.520 Mbps.
• The available information bandwidth is 149.760
  Mbps, which is the STS-3c envelope with section,
  line and path overhead removed.
• Lower signal rates use the Virtual Tributary (VT)
  mechanism of SONET.

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PPP over SONET (STS-3c)
PPP Frame 1 (HDLC)
PPP Frame 3 (HDLC)
PPP Frame 2 (HDLC)
260 columns (octets)
PPP Frame 1a
POH
PPP Frame 2a
PPP Frame 1b
PPP Frame 2b
PPP Frame 2c
9 rows
PPP Frame 3
2d
Path overhead
STS-3c Envelope
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Dense Wave Division Multiplexing (DWDM)

• Ref Cisco DWDM Primer

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Continue Demands for More Bandwidth
Same bit rate, more fibers Slow Time to
Market Expensive Engineering Limited Rights of
Way Duct Exhaust
More Fibers
WDM
Same fiber bit rate, more ls Fiber
Compatibility Fiber Capacity Release Fast Time to
Market Lower Cost of Ownership Utilizes existing
TDM Equipment
Faster Electronics (TDM)
Higher bit rate, same fiber Electronics more
expensive
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TDM vs. WDM

• Time division multiplexing
• Single wavelength per fiber
• Multiple channels per fiber
• 4 OC-3 channels in OC-12
• 4 OC-12 channels in OC-48
• 16 OC-3 channels in OC-48
• Wave division multiplexing
• Multiple wavelengths per fiber
• 4, 16, 32, 64 wavelengths per fiber
• Multiple channels per wavelength

Channel 1
Single Fiber (One Wavelength)
Channel n
l1
Single Fiber (Multiple Wavelengths)
l2
ln
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TDM vs. WDM

• TDM (SONET/SDH)
• Take sync and async signals and multiplex them to
  a single higher optical bit rate
• E/O or O/E/O conversion
• WDM
• Take multiple optical signals and multiplex
  themonto a single fiber
• No signal format conversion

DS-1 DS-3 OC-1 OC-3 OC-12 OC-48
SONET ADM
Fiber
OC-12c OC-48c OC-192c
DWDM OADM
Fiber
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FDM vs. WDM vs. DWDM

• Is WDM also a Frequency Division Multiplexing
  (FDM) which has been widely available for many
  years?
• Short Answer Yes. There is no difference
  between Wavelength Division and Frequency
  Division. In general, FDM is used in the context
  of Radio Frequency (MHz GHz) while WDM is used
  in the context of light ( THz)
• WDM The original standard requires 100 GHz
  spacing to prevent signals interference.
• Dense WDM (DWDM) support multiplexing of up to
  160 wavelengths of 10G/wavelength with 25GHz
  spacing
• The use of sub 100GHz for spacing is called Dense
  WDM.
• Some vendors even propose to use 12.5GHz spacing,
  and it would multiplex up to 320 wavelengths

Spectrum A
Spectrum B
spacing
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DWDM Economy
Conventional TDM Transmission10 Gbps
40km
40km
40km
40km
40km
40km
40km
40km
40km
TERM
TERM
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
TERM
TERM
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
TERM
TERM
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
TERM
TERM
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
1310 RPTR
DWDM Transmission10 Gbps
OC-48
OC-48
OC-48
OC-48
120 km
120 km
OC-48
120 km
OC-48
OC-48
OC-48
OA
OA
OA
OA
4 Fiber Pairs 32 Regenerators
1 Fiber Pair 4 Optical Amplifiers
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Optical Transmission Bands
Band Wavelength (nm)
New Band 1360 1460
S-Band 1460 1530
C-Band 1530 1565
L-Band 1565 1625
U-Band 1625 1675
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DWDM How does it work?

• TDM multiple services onto a single wavelength

TDM
DWDM
TDM
Single pair of fiber strand Multiple wave lengths
TDM
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DWDM Network
MUX
DEMUX
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DWDM Network Components
l1
l1...n
850/1310
15xx
l2
l3
Transponder
Optical Multiplexer
Optical ? gt DWDM ? Usually do O-E-O
l1
l1...n
l2
l3
Optical De-multiplexer
Optical Add/Drop Multiplexer (OADM)
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Optical Amplifier (OA)
Pout
Pin
gain

• EDFA (Erbium Doped Fiber Amplifier) amplifier
• Separate amplifiers for C-band and L-band

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Optical ADM (OADM)

• OADM is similar in many respects to SONET ADM,
  except that only optical wavelengths are added
  and dropped, and there is no conversion of the
  signal from optical to electrical.

Q there is no framing of DWDM, so how do we
add/drop/pass light? A ? It is based on ? and
? only.
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Cisco ONS 15800

• TO build a long haul network
• Up to 64 channels (i.e., wavelengths)
• OC-12, OC-48, OC-192
• up to 500 km

LEM Line Extension Module
http//www.cisco.com/warp/public/cc/pd/si/on15800s
/prodlit/ossri_ds.pdf
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DWDM Network(point-to-point)
OLA Optical Line Amplifier
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DWDM NetworkAdd-and-Drop
Note this is a linear topology, and not a ring
topology.
Chicago
New York
Pittsburg
?1 to Pittsburg ?2 to New York
?1 drop ?2 pass
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SONET and DWDM
DWDM terminal
DWDM terminal
Long Hall
SONET
SONET
DWDM
DWDM
SONET Chicago
SONET New York
OC-3
OC-3
IP
IP
PPP
PPP
SONET
SONET
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IP over DWDM ???
IP
IP
IP
???
DWDM terminal
DWDM terminal
DWDM
Note There is no protocol called IP over DWDM
or PPP over DWDM. However, there are many
publications on IP over DWDM and they all
require a layer-2 protocol which provides the
framing to encapsulate IP packets. (see the
previous slide)
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Summary

• Optical Fiber Network the market needs
• Access Network
• Passive Optical Network (PON)
• Metro Network
• SONET/SDH
• Transport Network (Long-Haul)
• DWDM
• DWDM can be applied to metro and access networks
  as well, but unlikely for its high cost.
• Optical network is a layer-1 technology, and IP
  is a layer-3 protocol. There must be a layer-2
  protocol to encapsulate IP packets to layer-2
  framing before it goes to the optical layer
• ATM (via RFC2684)
• SONET (via PPP)
• Ethernet (via GFP)