Optical Networking.ppt

Optical Networking Technologies

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

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Optical Transmission electrical signal

Optical Fibre Transmission System

optical signal

Optical Fibre Transmission System

electrical signal

Advantages of optical transmission: 1. Longer distance (noise resistance and less attenuation) 2. Higher data rate (more bandwidth) 3. 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 4

Optical Network Architecture DWDM

SONET

Long Haul Network

Metro Network transport network

Metro Network

PON Access Network

Access Network

Access Network

Access Network

CPE (customer premise) 5

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-toend 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 = 3×108 m/sec

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Optical Spectrum 

IR

UV

125 GHz/nm

Visible 850 nm

1550 nm

1310 nm

• Light Bandwidth

– Ultraviolet (UV) – Visible – Infrared (IR) • Communication wavelengths

1550nm

193,548.4GHz

1551nm

193,424.6GHz

1nm

125 GHz

– 850, 1310, 1550 nm – Low-loss wavelengths 8

Optical Fiber • An optical fiber is made of three sections: – The core carries the light signals – The cladding keeps the light in the core – The coating protects the glass

Core

Cladding

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: core=8.3 cladding=125 µm MM: core=50 or 62.5 cladding=125 µm

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Bending of light ray

7.11

Figure 7.12 Propagation modes

7.12

Figure 7.13 Modes

7.13

Figure 7.14 Fiber construction

7.14

Figure 7.15 Fiber-optic cable connectors

7.15

Figure 7.16 Optical fiber performance

7.16

Note: loss is relatively flat

Fiber Installation Support cable every 3 feet for indoor cable (5 feet for outdoor) Don’t 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! 7.17

Optical Transmission Effects Attenuation Dispersion & Nonlinearity Distortion

Transmitted Data Waveform

Waveform After 1000 Km

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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)

Loss of Timing (Jitter)

t

Phase Variation

t

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 (1:32)

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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 λ

1490 &1550

1550

1490 & 1550

Upstream λ

1310

1310

1310

Transmission

ATM

Ethernet

ATM, TDM, Ethernet

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PON Case Study (BPON) Optical Line Terminal (OLT) (Central Office)

Packet Core (IPoATM)

Optical Network Terminal (ONT) (customer premise) Two Ethernet ports One T1/E1 port Optical transport: 622M bps

T1/E1

802.3

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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28

29

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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 ADM

ADM

Metro SONET Ring ADM

Voice Switch

ADM ADM

Access Ring

Access Ring T1

ADM

Access Ring

ADM

T1

PBX 33

IP Over SONET SONET is designed for TDM traffic, and today’s need is packet (IP) traffic. Is there a better way to carry packet traffic over SONET? T1

DS3

OC-3 IP IP ????

SONET

SONET

802.3 RFC2684

IP

IP

AAL5

PPP

802.3

ATM

RFC1619

GFP

SONET

SONET

SONET

TDM Traffic RFC 2684: Encapsulate IP packet over ATM RFC 1619: Encapsulate PPP over SONET

GFP: Generic Frame Procedure

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ATM over SONET (STS-3c) Cell 1

Cell 2

Cell 3

260 columns (octets) Cell 1

Cell 2

Cell 3

OH

9 rows

STS-3c Envelope 35

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. 36

PPP over SONET (STS-3c) PPP Frame 1 (HDLC)

PPP Frame 2 (HDLC)

PPP Frame 3 (HDLC)

260 columns (octets) PPP Frame 1a PPP Frame 2a

PPP Frame 1b

PPP Frame 2b

POH

PPP Frame 2c 2d

Path overhead

9 rows

PPP Frame 3

STS-3c Envelope 37

Dense Wave Division Multiplexing (DWDM)

Ref: Cisco DWDM Primer

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Continue Demands for More Bandwidth Same bit rate, more fibers

More Fibers

Slow Time to Market Expensive Engineering Limited Rights of Way Duct Exhaust

W D M Faster Electronics (TDM)

Same fiber & bit rate, more s Fiber Compatibility Fiber Capacity Release Fast Time to Market Lower Cost of Ownership Utilizes existing TDM Equipment

Higher bit rate, same fiber Electronics more expensive 39

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 Channel n

Single Fiber (One Wavelength)

l1 l2

Single Fiber (Multiple Wavelengths)

ln

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TDM vs. WDM • TDM (SONET/SDH) DS-1 –Take sync and async DS-3 signals and multiplex them OC-1 to a single higher optical OC-3 bit rate OC-12 –E/O or O/E/O conversion OC-48

SONET ADM

Fiber

• WDM –Take multiple optical OC-12c signals and multiplex themOC-48c OC-192c onto a single fiber –No signal format conversion

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

spacing

Spectrum B

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DWDM Economy Conventional TDM Transmission—10 Gbps 40km 40km 40km 40km 40km 40km 40km 40km 40km 1310 1310 1310 1310 1310 1310 1310 1310 TERM TERM RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 TERM TERM RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 TERM TERM RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 TERM TERM RPTR RPTR RPTR RPTR RPTR RPTR RPTR RPTR

OC-48 OC-48 OC-48 OC-48

DWDM Transmission—10 Gbps OA

120 km

120 km OA

4 Fiber Pairs 32 Regenerators

OA

120 km

OA

OC-48 OC-48 OC-48 OC-48

1 Fiber Pair 4 Optical Amplifiers

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Optical Transmission Bands Band “New Band” S-Band C-Band L-Band U-Band

Wavelength (nm) 1360 1460 1530 1565 1625

– – – – –

1460 1530 1565 1625 1675

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DWDM: How does it work? TDM: multiple services onto a single wavelength TDM

DWDM TDM

TDM

Single pair of fiber strand Multiple wave lengths

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DWDM Network

MUX

DEMUX

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DWDM Network Components 1 

15xx

1...n

2 3

Transponder Optical λ => DWDM λ Usually do O-E-O

Optical Multiplexer

1 2

1...n

3

ADM

Optical De-multiplexer Optical Add/Drop Multiplexer (OADM) 47

Optical Amplifier (OA) Pin

gain

Pout



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: λ It is based on λ and λ only. 49

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 50

DWDM Network (point-to-point)

OLA: Optical Line Amplifier

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DWDM Network Add-and-Drop Note: this is a linear topology, and not a ring topology.

Chicago λ1: to Pittsburg λ2: to New York

Pittsburg λ1: drop λ2: pass

New York

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SONET and DWDM DWDM terminal

ADM

ADM

DWDM terminal

Long Hall

SONET Chicago

SONET

SONET

DWDM

DWDM ADM

SONET New York

OC-3

ADM

OC-3

IP

IP

PPP

PPP

SONET

SONET 53

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)

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