2. 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)
2
6. 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?
6
7. Optical 101
• Wavelength (λ): length of a wave and is measured in
nanometers, 10-9
m (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
7
9. 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
9
CladdingCore
Coating
10. 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
10
SM: core=8.3 cladding=125 µm
MM: core=50 or 62.5 cladding=125 µm
17. 7.17
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!
19. Optical Transmission Effects
19
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
20. Transmission Degradation
20
Loss of Energy
Loss of Timing (Jitter)
t t
Phase Variation
Shape Distortion
Ingress Signal Egress Signal
Optical Amplifier
Dispersion Compensation Unit (DCU)
Optical-Electrical-Optical (OEO) cross-connect
21. 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
21
23. 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
23
33. SONET in Metro Network
33
Long Haul
(DWDM)
Network
Metro SONET Ring
Access Ring
Access Ring
Access Ring
ADMADM
ADMADM
ADMADM
ADMADM
ADMADM
ADMADMADMADM
Voice Switch
PBX
Core Router
T1
T1
34. IP Over SONET
34
SONET
IP
????
SONET
IP
ATM
AAL5
RFC2684
802.3
SONET
IP
PPP
SONET
T1 DS3 OC-3
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?
SONET
GFP
802.3
IP
GFP: Generic Frame ProcedureTDM Traffic
RFC1619
RFC 2684: Encapsulate IP packet over ATM
RFC 1619: Encapsulate PPP over SONET
36. 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
39. Continue Demands for More Bandwidth
39
Faster Electronics
(TDM)
Higher bit rate, same fiber
Electronics more expensive
More Fibers
Same bit rate, more fibers
Slow Time to Market
Expensive Engineering
Limited Rights of Way
Duct Exhaust
W
D
M
Same fiber & bit rate, more λs
Fiber Compatibility
Fiber Capacity Release
Fast Time to Market
Lower Cost of Ownership
Utilizes existing TDM Equipment
40. 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
40
SingleSingle
Fiber (OneFiber (One
Wavelength)Wavelength)
Channel 1
Channel n
Single FiberSingle Fiber
(Multiple(Multiple
Wavelengths)Wavelengths)
l1l1
l2l2
lnln
41. 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 them
onto a single fiber
–No signal format conversion
41
DS-1
DS-3
OC-1
OC-3
OC-12
OC-48
OC-12c
OC-48c
OC-192c
FiberFiber
DWDMDWDM
OADMOADM
SONETSONET
ADMADM
FiberFiber
42. 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
42
Spectrum A Spectrum Bspacing
43. DWDM Economy
43
TERM
TERM
TERM
Conventional TDM Transmission—10 Gbps
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
TERM
40km
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
TERM
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
TERM
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
1310
RPTR
TERM
120 km
OC-48
OA OAOA OA
120 km 120 km
OC-48
OC-48
OC-48
OC-48
OC-48
OC-48
OC-48
DWDM Transmission—10 Gbps
1 Fiber Pair
4 Optical Amplifiers
TERM
4 Fiber Pairs
32 Regenerators
40km 40km 40km 40km 40km 40km 40km 40km
49. 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.
49
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.
53. SONET and DWDM
53
SONET
Chicago
SONET
New York
ADMADM ADMADM
DWDM
terminal
DWDM
terminal
Long Hall
ADMADM ADMADM
OC-3 OC-3
IP
PPP
SONET
IP
PPP
SONET
SONET
DWDM
SONET
DWDM
54. IP over DWDM ???
54
DWDM
terminal
DWDM
terminal
IP IPIP
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)
55. 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)
55
Notes de l'éditeur
http://www.hakko-opto.com/pdf/TW_300_LAN_PLUS.pdf
FSAN: Full Service Access Network
As the need for more capacity increased over the years, first for voice traffic, today mostly for internet traffic, different solutions have been adopted.
The simplest one is Space Division Multiplexing: it simply means to deploy and use more links of the same type. This approach is very expensive since it uses up all available resources and asks for infrastructure upgrades
A more efficient solution came in with TDM technologies. In this case, we keep the same transmission medium but we increase the bit rate over it. If you go back a few years, SDH/SONET equipment, and routers as well, was transmitting at 155 Mbps, then 622 Mbps, finally 2.5 Gbps and just recently 10 Gbps. It is true that the transmission medium is always the same, but the transmission equipment is getting more and more complicated and expensive. Additionally, the maximum transported capability over a fiber pair is iin the range of a few Gbps.
The way to scale to higher transported capacity is WDM. This technology keeps the same fiber, the same bit rate, but uses multiple colours to multiply transported capacity.
The majority of DWDM systems today operate in the C-Band. Moving into L next, then potentially S. CWDM operates primarily across S-C-L, with Extended Band fibers (like Allwave and SMF-28e) opening up the 1360-1460 window to support additional CWDM wavelengths.