1. Optical networks: From point-to-point transmission to full

Report
1
TTM 1: Access and core
networks, advanced
Based on paper:
“Optical networks: From point-to-point transmission to
full networking capabilities”
Presented by: Zekarias Teshome
2
Contents




Introduction
Transmission aspects
Opaque versus transparent
Re-configurable optical networks
 OADM
 Optical cross connects
 MPLS/GMPLS
 Network architectures
 The overlay model
 The peer model
 Reference network
 Future IP solutions
 Summery
3
Introduction
 It was early realized that optical fiber has a
tremendous bandwidth and
 Also the low electromagnetic interference of the
medium makes it ideal for secure communication
 The main issue would be to find technically feasible
and economical ways to capitalize on this potential.
4
Contents




Introduction
Transmission aspects
Opaque versus transparent
Re-configurable optical networks
 OADM
 Optical cross connects
 MPLS/GMPLS
 Network architectures
 The overlay model
 The peer model
 Reference network
 Future IP solutions
 Summery
5
Transmission aspects
Transmission systems use WDM( method used to increase
the capacity of a single strand of fiber)
 From the transmitter side: many different colored lights combined
by the WDM multiplexing device and put in to the single strand of fiber.
 On the receiver side: each color is separated into its own color by
WDM Demultiplexing device
6
Cont.
 Due to the characteristic attenuation curve of fiber, there
are two regions typically used for communications.
7
Cont.
 Dense Wavelength Division Multiplexing(DWDM) and
 Coarse Wavelength Division Multiplexing (CWDM)
 The difference is the channel spacing.
 And the range of the optical spectrum they typically cover.
8
DWDM Vs. CWDM
DWDM
 all frequencies spaced at multiples of 50 GHz
 with wavelengths in the 1530 – 1565 nm range,
 The tight spacing between these channels requires temperature
control of the lasers and increases cost.
CWDM
 Here the channel spacing is increased to 200 GHz,
– both the fabrication and the temperature control requirements of these
lasers are lower, and
– the overall cost dramatically reduced.
9
Contents




Introduction
Transmission aspects
Opaque versus transparent
Re-configurable optical networks
 OADM
 Optical cross connects
 MPLS/GMPLS
 Network architectures
 The overlay model
 The peer model
 Reference network
 Future IP solutions
 Summery
10
Opaque versus transparent
 A core optical network architecture can be opaque or
transparent.
 An opaque architecture implies that the optical signal carrying traffic
undergoes an optical to electronic to optical (OEO) conversion at
different places in the network.
 A transparent architecture implies that the optical signal carrying
traffic stays in the optical domain.
11
Contents




Introduction
Transmission aspects
Opaque versus transparent
Re-configurable optical networks
 OADM
 Optical cross connects
 MPLS/GMPLS
 Network architectures
 The overlay model
 The peer model
 Reference network
 Future IP solutions
 Summery
12
Re-configurable optical
networks
 The key NEs in order to realize re-configurable
optical networks are
 Reconfigurable optical add-drop multiplexer (R-OADM) and
 optical cross connects (OXC).
13
OADM
 Typically close to 70 % of the traffic that arrives at a
node is through-passing traffic, i.e.
 traffic with destination another node.
 Instead of processing and switching/routing all traffic
an optical add-drop multiplexer (OADM) can allow
 some of the through-passing traffic to be forwarded optically,
directly through the node.
 The wavelengths that have been dropped may be added back in
the link.
14
Cont.
• There are two main types of OADM that can be used
in WDM optical networks;
 Fixed OADMs: that are used to drop or add data
signals on dedicated WDM channels, and
 Reconfigurable OADMs: re-configurability refers to
the ability to select the desired wavelengths to be
dropped and added on the fly, as opposed to having
to plan ahead and deploy appropriate equipment.
15
Cont.
16
Optical cross connects
 Optical networks consist of a multiple of sub-networks.
 These will need to be interconnected by optical links in
an arbitrary topology, i.e. in a mesh topology
 In order to be able to realize mesh networks, optical
cross connects are required.
17
Cont.
 An OXC performs in essence the same function as an R-OADM
but for a larger number of line ports and directions.
Schematic of an optical cross-connect; optoelectronic , all-optical
18
Cont.
 An OXC provides several key functions in a large
network:
 Service provisioning
– An OXC can be used to provide end-to-end light paths in a large
network in an automated manner.
 Protection and restoration
– The OXC combined with monitoring equipment can provide swift
restoration of huge amounts of traffic by redirecting wavelengths
from the failed paths to alternative paths.
19
Cont.
 Wavelength conversion
‒ Light paths need not use one single wavelength through the whole
network since this complicates wavelength management in the
network.
 Multiplexing and grooming
- in its purest form the OXC is all-optical. However, the OXC
comprises also an add-drop part where multiplexing and
grooming of ingress and egress signals can take place.
20
Cont.
 OXCs can be an opaque and employ an electrical
core.
 A large number of alternative all-optical solutions
have been explored,
 One of the most prominent OXC solutions is based
on: a two-dimensional or three-dimensional array of
miniature mirrors (MEMS based)
21
Cont.
a) A picture of a miniature MEMS mirror, b) schematic of an OXC using miniature MEMS
mirrors
22
Cont.
 A new OXC architecture that uses tunable lasers and
Array Waveguide Gratings (AWG) as shown in Figure below.
A schematic of an OXC based on an Arrayed Waveguide Grating and tunable
wavelength converters
23
Cont.
 The port a signal will exit the OXC from, is explicitly
determined by its wavelength and the AWG input it
arrives at.
 Hence the OXC is re-configured by tuning the wavelength of the signal in
a wavelength converter using tunable lasers
24
Contents




Introduction
Transmission aspects
Opaque versus transparent
Re-configurable optical networks
 OADM
 Optical cross connects
 MPLS/GMPLS
 Network architectures
 The overlay model
 The peer model
 Reference network
 Future IP solutions
 Summery
25
MPLS/GMPLS
 MPLS involves setting up a specific path for a given
sequence of packets by
 labeling every packet in order to figure out which outward path a packet
should be switched toward its destination.
 multiprotocol because it works with the Internet Protocol (IP),
Asynchronous Transport Mode (ATM), and frame relay network
protocols.
 GMPLS (Generalized Multiprotocol Label Switching),
 is a technology that provides enhancements to Multiprotocol Label
Switching (MPLS) to support network switching for time, wavelength, and
space switching as well as for packet switching.
26
Contents




Introduction
Transmission aspects
Opaque versus transparent
Re-configurable optical networks
 OADM
 Optical cross connects
 MPLS/GMPLS
 Network architectures
 The overlay model
 The peer model
 Reference network
 Future IP solutions
 Summery
27
Network architectures
 Traditional transport networks can be modeled as the
interaction of two operating planes:
 a transport plane and
 a management plane.
 In this model, the transport plane carries the user
data and comprises network equipment, such as line
 interface cards, switch fabrics, backplanes and fiber plant.
 Network OAM&P (operations, administration,
maintenance and provisioning) is fully handled by the
management plane.
28
Cont.
 Now, we are beginning to see the deployment of
optical control planes
 sit between the management and transport planes. The control
plane moves some of the network intelligence down to the NEs.
29
Cont.
 In the optical transport field, the control plane has
been called by the IETF as,
 Generalized Multi-Protocol Label Switching, or GMPLS.
 The IP and optical control planes can be loosely or
tightly coupled in terms of,
 firstly, the details of the optical network topology, resources, and
routing information that is revealed to the IP layer, and
 secondly, the degree of control IP routers have on optical network
elements and thus the degree to which they can determine the
exact paths through this optical network.
30
Cont.
 Based on this:
 The overlay model
 The peer model
31
The overlay model
 In this architecture option the optical network has full
control over its network resources
o by means of a fully independent optical control plane.
A schematic of the Automatically Switched Optical Network, according to the overlay
model
32
The peer model
 In this architecture the control planes of the optical
network and IP are fully integrated.
 the optical part unintelligent and
 rely on IP intelligence to run the network.
33
Contents




Introduction
Transmission aspects
Opaque versus transparent
Re-configurable optical networks
 OADM
 Optical cross connects
 MPLS/GMPLS
 Network architectures
 The overlay model
 The peer model
 Reference network
 Future IP solutions
 Summery
34
Reference network
 The network can be seen as comprising three parts:
 The core and long-haul part,
 The metropolitan area network, and
 The access part.
35
Cont.
 The core part
 is a national network connecting major cities.
 The metro network
 extends over a large city or a province, comprises less
aggregated traffic than the core as it is closer to customers
and end users, and involves lower capacities than the core.
 Access part
 is the part that provides a connection between an end user
(e.g. a home) or a business to the metro and core networks.
36
Contents




Introduction
Transmission aspects
Opaque versus transparent
Re-configurable optical networks
 OADM
 Optical cross connects
 MPLS/GMPLS
 Network architectures
 The overlay model
 The peer model
 Reference network
 Future IP solutions
 Summery
37
Future IP solutions
 IP routers do not appear to be able to scale gracefully
to meet the needs of multi-Terabit networks.
 Alternatively, better scalable large switching matrices
may be created using both electrical and optical
switches.
A schematic of a hybrid optical-electrical router, using both optical switching matrices and
electrical switches
38
Cont.
 A next step is optical packet or burst switching (OPS/
OBS) – or so-called optical routers.
39
Contents




Introduction
Transmission aspects
Opaque versus transparent
Re-configurable optical networks
 OADM
 Optical cross connects
 MPLS/GMPLS
 Network architectures
 The overlay model
 The peer model
 Reference network
 Future IP solutions
 Summery
40
Summery
 Optical networks may well be the key to high capacity
intelligent networks that utilize
 their resources in an efficient way and can provide a range of
differentiated services.
 Optical switching provides an economical way to
handle large amounts of traffic and to build reliable
networks.
 Optical functionality can be introduced at a separate
layer and complement higher network layers, and/or it
can be directly integrated and controlled by IP routers.
 Optical technology can also be employed to realize
larger/higher throughput and more robust IP routers.

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