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Optical Networking Technologies. 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). Optical Transmission. optical signal. electrical signal. electrical signal. Optical

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outline
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)
optical transmission
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
optical networks
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
optical network architecture
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)

all optical networks
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?
optical 101
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
optical spectrum
Optical Spectrum

l

IR

UV

125 GHz/nm

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

Visible

850 nm

1550 nm

1310 nm

Bandwidth

optical fiber
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

optical fiber cont
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

slide16

Figure 7.16 Optical fiber performance

Note: loss is relatively flat

slide17

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!

optical transmission effects
Optical Transmission Effects

Attenuation

Dispersion

& Nonlinearity

Distortion

Waveform After 1000 Km

Transmitted Data Waveform

optical transmission effects1
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

transmission degradation
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

passive optical network pon
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
passive optical network pon1
Passive Optical Network (PON)

OLT: Optical Line Terminal

ONT: Optical Network Terminal

Splitter

(1:32)

pon many flavors
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
pon case study bpon
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)

sonet in metro network
SONET in Metro Network

Long Haul

(DWDM)

Network

Core Router

Metro SONET Ring

Voice Switch

Access Ring

Access Ring

T1

Access Ring

T1

PBX

ip over sonet
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

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

atm over sonet sts 3c
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

ppp over sonet
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.
ppp over sonet sts 3c
PPP over SONET (STS-3c)

PPP Frame 1 (HDLC)

PPP Frame 2 (HDLC)

PPP Frame 3 (HDLC)

260 columns (octets)

POH

PPP Frame 1a

PPP Frame 2a

PPP Frame 1b

PPP Frame 2b

PPP Frame 2c

9 rows

PPP Frame 3

2d

Path overhead

STS-3c Envelope

continue demands for more bandwidth
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

tdm vs wdm
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

l2

Single Fiber

(Multiple Wavelengths)

ln

tdm vs wdm1
TDM vs. WDM

DS-1

DS-3

OC-1

OC-3

OC-12

OC-48

  • 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

SONET

ADM

Fiber

OC-12c

OC-48c

OC-192c

DWDM

OADM

Fiber

fdm vs wdm vs dwdm
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

dwdm economy
DWDM Economy

Conventional TDM Transmission—10 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 Transmission—10 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

dwdm how does it work
DWDM: How does it work?

TDM: multiple services onto a single wavelength

TDM

DWDM

TDM

Single pair of fiber strand

Multiple wave lengths

TDM

dwdm network
DWDM Network

MUX

DEMUX

dwdm network components
DWDM Network Components

l1

l1...n

850/1310

15xx

l2

l3

Transponder

Optical Multiplexer

Optical λ => DWDM λ

Usually do O-E-O

l1

l1...n

l2

l3

Optical De-multiplexer

Optical Add/Drop Multiplexer

(OADM)

optical amplifier oa
Optical Amplifier (OA)

Pout

Pin

gain

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

cisco ons 15800
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

dwdm network point to point
DWDM Network(point-to-point)

OLA: Optical Line Amplifier

dwdm network add and drop
DWDM NetworkAdd-and-Drop

Note: this is a linear topology, and not a ring topology.

Chicago

New York

Pittsburg

λ1: to Pittsburg

λ2: to New York

λ1: drop

λ2: pass

sonet and dwdm
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

ip over dwdm
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)

summary
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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