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Differences from draft-bernstein-ccamp-wson-impairments-00.txt
Network Working Group G. Bernstein
Internet Draft Grotto Networking
Y. Lee
D. Li
Huawei
Intended status: Informational October 29, 2008
Expires: April 2009
A Framework for the Control and Measurement of Wavelength Switched
Optical Networks (WSON) with Impairments
draft-bernstein-ccamp-wson-impairments-01.txt
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Abstract
The operation of optical networks can require a level of detail in
the characterization of network elements, subsystems, devices, and
cabling not typically encountered with other networking technologies.
In addition, these physical characteristics may be important to
consider during typical day-to-day operations such as optical path
establishment and connection monitoring, as well as during the
network planning, installation, and turn-up phases. This document
discusses how the definition and characterization of optical fiber,
devices, subsystems, and network elements contained in various ITU-T
recommendations can be combined with common control and measurement
plane and path computation element technologies to support impairment
aware Routing and Wavelength Assignment (RWA) in optical networks.
Table of Contents
1. Introduction...................................................3
2. Impairment Aware Optical Path Computation......................4
2.1. IA-RWA Computing Architectures............................6
2.1.1. Combined Routing, WA, and IV.........................7
2.1.2. Separate Routing, WA, or IV..........................7
2.1.3. Distributed WA and/or IV.............................7
2.2. Information Model for Impairments.........................8
2.3. Protocol Extension Implications...........................8
2.3.1. Routing..............................................8
2.3.2. Signaling............................................9
2.3.3. PCE..................................................9
3. Security Considerations........................................9
4. IANA Considerations............................................9
5. Acknowledgments...............................................10
APPENDIX A: Overview of Optical Layer ITU-T Recommendations......11
A.1. Fiber and Cables.........................................11
A.2. Devices..................................................12
A.2.1. Optical Amplifiers..................................12
A.2.2. Dispersion Compensation.............................13
A.2.3. Optical Transmitters................................14
A.2.4. Optical Receivers...................................14
A.3. Components and Subsystems................................15
A.4. Network Elements.........................................16
6. References....................................................18
6.1. Normative References.....................................18
6.2. Informative References...................................20
Author's Addresses...............................................20
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Intellectual Property Statement..................................21
Disclaimer of Validity...........................................22
1. Introduction
As an optical signal progresses along its path it may be altered by
the various physical processes in the optical fibers and devices it
encounters. When such alterations result in signal degradation, we
usually refer to these processes as "impairments". An overview of
some critical optical impairments and their routing (path selection)
implications can be found in [RFC4054]. Roughly speaking, optical
impairments accumulate along the path (without 3R regeneration)
traversed by the signal. They are influenced by the type of fiber
used, the types and placement of various optical devices and the
presence of other optical signals that may share a fiber segment
along the signal's path. The degradation of the optical signals due
to impairments can result in unacceptable bit error rates or even a
complete failure to demodulate and/or detect the received signal.
Therefore, path selection in any WSON requires consideration of
optical impairments so that the signal will be propagated from the
network ingress point to the egress point with acceptable amount of
degradation.
Some optical subnetworks are designed such that over any path the
degradation to an optical signal due to impairments never exceeds
prescribed bounds. This may be due to the limited geographic extent
of the network, the network topology, and/or the quality of the
fiber and devices employed. In such networks the path selection
problem reduces to determining a continuous wavelength from source
to destination (the Routing and Wavelength Assignment problem).
These networks are discussed in [WSON-Frame]. In other optical
networks, impairments are important and the path selection process
must be impairment-aware.
Although [RFC4054] describes a number of key optical impairments, a
more complete description of optical impairments and the processes
that spawn them can be found in textbooks or reference books on
optical communications [Agrawal02], [Agrawal07]. To be useful to
consumers and producers of optical fiber, components, and subsystems,
optical characteristics need to be precisely defined along with
methods for their measurement, estimation and approximation. The ITU-
T and other SDOs have assumed this responsibility and as optical
technology has advanced these documents have been updated. Appendix
A of this document provides an overview of the extensive ITU-T
documentation in this area.
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The benefits of operating networks of different technologies using an
intelligent control plane have been described in many places, and the
Generalized Multiprotocol Label Switching (GMPLS) control plane is
described in [RFC3945]. The advantages of using a path computation
element (PCE) to perform complex path computations are discussed in
[RFC4655].
Given the existing standards covering optical characteristics
(impairments) and the knowledge how the impact of impairments may be
estimated along a path, this document provides a framework for
impairment aware path computation and establishment utilizing GMPLS
protocols and the PCE architecture. As in the impairment free case
covered in [WSON-Frame] a number of different control plane
architectural options are described.
2. Impairment Aware Optical Path Computation
One of the most basic questions in communications is whether one can
successfully transmit information from a transmitter to a receiver
within a prescribed error tolerance, usually specified as a maximum
permissible bit error ratio (BER). This generally depends on the
nature of the signal transmitted between the sender and receiver and
the nature of the communications channel between the sender and
receiver. The optical path utilized (along with the wavelength)
determines the communications channel.
The optical impairments incurred by the signal along the fiber and at
each optical network element along the path determine whether the BER
performance or any other measure of signal quality can be met for
this particular signal on this particular path.
From a control plane perspective it is useful to classify optical
networks into categories based on how one determines whether a
particular optical signal on a particular optical path can meet
desired signal quality objectives such as BER [WD24],[WD05]. In the
following we say a path is "conformant" for a particular type of
signal if the signal quality objectives are achieved at the receiver.
The four classes of optical networks with regards to impairments are:
1. Networks designed such that every possible path is conformant for
the signal types permitted on the network. In this case
impairments are only taken into account during network design and
after that, for example during optical path computation, they can
be ignored. This is the case discussed in [WSON-Frame] where
impairments could be ignored by the control plane.
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2. Networks in which a limited number of pre-calculated paths are
conformant for each type of signal permitted in the network. In
this case the control plane is not have any detailed information
about optical impairments. Instead we are given a list of
qualified paths for each permitted signal in the network. This
might occur if proprietary impairment models are used to evaluate
paths or a vendor chooses not to publish impairment information.
For example if a single WDM line system vendor is used within an
optical subnetwork and chooses not to publish optical impairment
information, that vendor with knowledge of the characteristics of
the ROADMS and PXCs used in the network could pre-calculate a list
of valid paths. Note that the structure of such a qualified
path/wavelength list could be useful to standardize as part of an
impairment aware information model.
3. Networks in which impairment effects can be estimated via
approximation techniques such as link budgets and dispersion (rise
time) budgets [Agrawal02],[G.680],[G.sup39]. As networks grow
larger listing all useable paths for each signal type can
encounter scaling issues. Instead the viability of most optical
paths for a particular class of signals is performed using well
defined approximation techniques [G.680], [G.sup39]. Much work at
ITU-T has gone into developing impairment models at this and more
detailed levels. Impairment characterization of network elements
could then made available via the control plane and then used to
calculate which paths are conformant with a specified BER for a
particular signal type. This case requires that all relevant
impairment information is available from all optical subsystems.
4. Networks in which impairment effects must be more accurately
estimated. This typically includes detailed dispersion,
interference and/or nonlinear effect simulations. This includes
evaluation of the impact to any existing paths prior to the
addition of a new path. This is currently performed via methods
that solve the partial differential equations describing signal
propagation in fiber along with more detail models for the other
network elements [Agrawal02],[Agrawal07]. The
estimation/simulation time required can be very situation
dependent. The implication is that a significant amount of time
could be required to "qualify" a path and this would need to be
taken into account in a PCE architecture that includes impaired
path validation. ITU-T recommendations contain a good deal of more
detailed optical characteristics (see Appendix A) for fibers and
devices, however these are not currently assembled into a single
modeling document as was done for the approximate analysis model
in [G.680].
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2.1. IA-RWA Computing Architectures
As previously stated from the point of view of RWA we may take
optical impairments into account by being given:
1. A list of valid paths with corresponding wavelength constraints;
2. Sufficient approximate impairment information to determine valid
paths;
3. A validation decision from an estimation incorporating more
complete impairment models;
Hence to take into account optical impairments we add additional
constraints to the impairment-free RWA process described in [WSON-
Frame]. In IA-RWA, there are conceptually three functions to be
considered in path computation.
o Routing (R): finding a route for the given source-destination.
o Wavelength Assignment (WA): assigning a wavelength for the route
o Impairment Validation (IV): applying a set of impairment
constraints to the route and selected wavelength to see whether
they would provide signal quality satisfaction.
The IA-RWA architecture options can be built from the non-IA RWA
computation architectures defined in the WSON framework document
[WSON Frame]. Recall that the following three RWA computation
architecture options [WSON-Frame].
o Combined RWA --- Both routing and wavelength assignment are
performed at a single computational entity. This choice assumes
that computational entity has sufficient WSON network link/nodal
and topology information to be able to compute RWA.
o Separate Routing and WA --- Separate entities perform routing and
wavelength assignment. The path obtained from the routing
computational entity must be furnished to the entity performing
wavelength assignment.
o Routing with Distributed WA --- Routing is performed at a
computational entity while wavelength assignment is performed in a
distributed fashion across the nodes along the path.
The following subsections consider three major classes of IA-RWA path
computation architectures.
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2.1.1. Combined Routing, WA, and IV
We can conceptually or algorithmically combine the processes of
routing, wavelength assignment and impairment validation if we are
given: (a) the impairment-free WSON network information as discussed
in [WSON-Frame] and (b) either a list of validated paths/wavelengths
or sufficient approximate impairment information to perform
calculations to validate potential paths. In this case routing (R)
and wavelength assignment (WA) and impairment validation (IV) are
performed at a single computational entity.
This situation could benefit from an information model that compactly
describes a list of valid paths/wavelengths or characterizes
impairments at a level similar to that in [G.680].
2.1.2. Separate Routing, WA, or IV
As was discussed in [WSON-Frame] there can be advantages to
separating routing from WA. In addition, as previously described in
the case of detailed impairment modeling we may want to logically
separate IV from RWA. In addition for systems operating closer to
physical limits the validation computations could be proprietary and
hence by necessity may be logically separated.
The following conceptual architectures belong in this general
category:
o R+WA+IV -- separate routing, wavelength assignment, and impairment
validation
o R + (WA & IV) -- routing separate from a combined wavelength
assignment and impairment validation process. Note that impairment
validation is typically wavelength dependent hence combining WA
with IV can lead to efficiencies.
o (RWA)+IV - combined routing and wavelength assignment with a
separate impairment validation process.
2.1.3. Distributed WA and/or IV
In the case where the effects of impairments can be calculated via
approximate models such as those in [G.680] standard methods can be
applied to calculate the combined potential impairment effects on a
signal following a prescribed network path. This can allow for the
distributed computation of impairment effects and avoid the need to
distribute impairment characteristics of network elements and links
via route protocols or by other means. An example of such an approach
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is given in [Martinelli] and utilizes enhancements to RSVP signaling
to carry accumulated impairment related information. For such a
system to be interoperable the various impairment measures to be
accumulated would need to be agreed upon. Section 9 of [G.680] can be
useful in deriving such cumulative measures but doesn't explicitly
state how a distributed computation would take place. For example in
the computation of the optical signal to noise ratio along a path
(see equation 9-3 of [G.680]) one could accumulate the linear sum
terms and convert to dBs at the destination or one could convert in
and out of dBs at each intermediate point along the path.
If distributed WA is being done at the same time as distribute IV
then we may need to accumulate impairment related information for all
wavelengths that could be used. This is somewhat winnowed down as
potential wavelengths are discovered to be in use, but could be a
significant burden for lightly loaded high channel count networks.
2.2. Information Model for Impairments
As previously discussed we are either given a list of conformant
optical paths through a network or we are given information
concerning the impairments for each network element which we can use
to validate a path for a particular signal type.
GMPLS and other IETF protocols have included descriptions of paths in
the past and methods for compact representations of available
wavelengths have been discussed in [WSON-Info]. A number of ITU-T
recommendations cover detailed as well as approximate impairment
characteristics of fibers and a variety of devices and subsystems. A
well integrated impairment model for optical network elements is
given in [G.680] and is used to form the basis for an optical
impairment model in a companion document [Imp-Info].
2.3. Protocol Extension Implications
Given the previous architectures and information models we have the
following implications for routing, signaling and PCE related
protocols.
2.3.1. Routing
Different approaches to path/wavelength impairment validation gives
rise to different demands placed on GMPLS routing protocols.
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In the case where a list of conformant paths/lambdas needs to be
distributed to PCEs (or network elements with co-located PCEs) the
routing protocol might be expected to help distribute this list.
In the case where approximate impairment information is used to
validate paths GMPLS routing may be used to distribute the impairment
characteristics of the network elements and links.
In the case where a separate path/wavelength validation server is
used no additional demands may be require of GMPLS routing.
2.3.2. Signaling
Although we see impacts on signaling in cases where distributed
impairment validation is performed, we may also want to add
information to a connection request such as desired egress signal
quality (defined in some appropriate sense). In addition, since the
characteristics of the signal itself, such as modulation type, can
play a major role in the tolerance of impairments, this type of
information will need to be implicitly or explicitly signaled.
In the cases of distributed validation of path/wavelength and
distributed wavelength assignment and validation we need to
accumulate impairment information as discussed in section 2.1.3.
2.3.3. PCE
For a PCE involved with impairment related computations we have two
potential areas of impact: (a) impairment information model, (b) PCEP
extensions for dealing with impairment related requests.
3. Security Considerations
This document discusses a number of control plane architectures that
incorporate knowledge of impairments in optical networks. If such
architecture is put into use within a network it will by its nature
contain details of the physical characteristics of an optical
network. Such information would need to be protected from intentional
or unintentional disclosure.
4. IANA Considerations
This draft does not currently require any consideration from IANA.
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5. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
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APPENDIX A: Overview of Optical Layer ITU-T Recommendations
For optical fiber, devices, subsystems and network elements the ITU-T
has a variety of recommendations that include definitions,
characterization parameters and test methods. In the following we
take a bottom up survey to emphasize the breadth and depth of the
existing recommendations. We focus on digital communications over
single mode optical fiber.
A.1. Fiber and Cables
Fibers and cables form a key component of what from the control plane
perspective could be termed an optical link. Due to the wide range of
uses of optical networks a fairly wide range of fiber types are used
in practice. The ITU-T has three main recommendations covering the
definition of attributes and test methods for single mode fiber:
o Definitions and test methods for linear, deterministic attributes
of single-mode fibre and cable [G.650.1]
o Definitions and test methods for statistical and non-linear
related attributes of single-mode fibre and cable [G.650.2]
o Test methods for installed single-mode fibre cable sections
[G.650.3]
General Definitions[G.650.1]: Mechanical Characteristics (numerous),
Mode field characteristics(mode field, mode field diameter, mode
field centre, mode field concentricity error, mode field non-
circularity), Glass geometry characteristics, Chromatic dispersion
definitions (chromatic dispersion, group delay, chromatic dispersion
coefficient, chromatic dispersion slope, zero-dispersion wavelength,
zero-dispersion slope), cut-off wavelength, attenuation. Definition
of equations and fitting coefficients for chromatic dispersion (Annex
A). [G.650.2] polarization mode dispersion (PMD) - phenomenon of PMD,
principal states of polarization (PSP), differential group delay
(DGD), PMD value, PMD coefficient, random mode coupling, negligible
mode coupling, mathematical definitions in terms of Stokes or Jones
vectors. Nonlinear attributes: Effective area, correction factor k,
non-linear coefficient (refractive index dependent on intensity),
Stimulated Billouin scattering.
Tests defined [G.650.1]: Mode field diameter, cladding diameter, core
concentricity error, cut-off wavelength, attenuation, chromatic
dispersion. [G.650.2]: test methods for polarization mode dispersion.
[G.650.3] Test methods for characteristics of fibre cable sections
following installation: attenuation, splice loss, splice location,
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fibre uniformity and length of cable sections (these are OTDR based),
PMD, Chromatic dispersion.
With these definitions a variety of single mode fiber types are
defined as shown in the table below:
ITU-T Standard | Common Name
------------------------------------------------------------
G.652 [G.652] | Standard SMF |
G.653 [G.653] | Dispersion shifted SMF |
G.654 [G.654] | Cut-off shifted SMF |
G.655 [G.655] | Non-zero dispersion shifted SMF |
G.656 [G.656] | Wideband non-zero dispersion shifted SMF |
------------------------------------------------------------
A.2. Devices
A.2.1. Optical Amplifiers
Optical amplifiers greatly extend the transmission distance of
optical signals in both single channel and multi channel (WDM)
subsystems. The ITU-T has the following recommendations:
o Definition and test methods for the relevant generic parameters of
optical amplifier devices and subsystems [G.661]
o Generic characteristics of optical amplifier devices and
subsystems [G.662]
o Application related aspects of optical amplifier devices and
subsystems [G.663]
o Generic characteristics of Raman amplifiers and Raman amplified
subsystems [G.665]
Reference [G.661] starts with general classifications of optical
amplifiers based on technology and usage, and include a near
exhaustive list of over 60 definitions for optical amplifier device
attributes and parameters. In references [G.662] and [G.665] we have
characterization of specific devices, e.g., semiconductor optical
amplifier, used in a particular setting, e.g., line amplifier. For
example reference[G.662] gives the following minimum list of relevant
parameters for the specification of an optical amplifier device used
as line amplifier in a multichannel application:
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a) Channel allocation.
b) Total input power range.
c) Channel input power range.
d) Channel output power range.
e) Channel signal-spontaneous noise figure.
f) Input reflectance.
g) Output reflectance.
h) Maximum reflectance tolerable at input.
i) Maximum reflectance tolerable at output.
j) Maximum total output power.
k) Channel addition/removal (steady-state) gain response.
l) Channel addition/removal (transient) gain response.
m) Channel gain.
n) Multichannel gain variation (inter-channel gain difference).
o) Multichannel gain-change difference (inter-channel gain-change
difference).
p) Multichannel gain tilt (inter-channel gain-change ratio).
q) Polarization Mode Dispersion (PMD).
A.2.2. Dispersion Compensation
In optical systems two forms of dispersion are commonly encountered
[RFC4054] chromatic dispersion and polarization mode dispersion
(PMD). There are a number of techniques and devices used for
compensating for these effects. The following ITU-T recommendations
characterize such devices:
o Characteristics of PMD compensators and PMD compensating receivers
[G.666]
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o Characteristics of Adaptive Chromatic Dispersion Compensators
[G.667]
The above furnish definitions as well as parameters and
characteristics. For example in [G.667] adaptive chromatic dispersion
compensators are classified as being receiver, transmitter or line
based, while in [G.666] PMD compensators are only defined for line
and receiver configurations. Parameters that are common to both PMD
and chromatic dispersion compensators include: line fiber type,
maximum and minimum input power, maximum and minimum bit rate, and
modulation type. In addition there are a great many parameters that
apply to each type of device and configuration.
A.2.3. Optical Transmitters
The definitions of the characteristics of optical transmitters can be
found in references [G.957], [G.691], [G.692] and [G.959.1]. In
addition references [G.957], [G.691], and [G.959.1] define specific
parameter values or parameter ranges for these characteristics for
interfaces for use in particular situations.
We generally have the following types of parameters
Wavelength related: Central frequency, Channel spacing, Central
frequency deviation[G.692].
Spectral characteristics of the transmitter: Nominal source type
(LED, MLM lasers, SLM lasers) [G.957], Maximum spectral width, Chirp
parameter, Side mode suppression ratio, Maximum spectral power
density [G.691].
Power related: Mean launched power, Extinction ration, Eye pattern
mask [G.691], Maximum and minimum mean channel output power
[G.959.1].
A.2.4. Optical Receivers
References [G.959.1], [G.691], [G.692] and [G.957], define optical
receiver characteristics and [G.959.1], [G.691] and [G.957]give
specific values of these parameters for particular interface types
and network contexts.
The receiver parameters include:
Receiver sensitivity: minimum value of average received power to
achieve a 1x10-10 BER [G.957] or 1x10-12 BER [G.691]. See [G.957] and
[G.691] for assumptions on signal condition.
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Receiver overload: Receiver overload is the maximum acceptable value
of the received average power for a 1x10.10 BER [G.957] or a 1x10-12
BER [G.691].
Receiver reflectance: "Reflections from the receiver back to the
cable plant are specified by the maximum permissible reflectance of
the receiver measured at reference point R."
Optical path power penalty: "The receiver is required to tolerate an
optical path penalty not exceeding X dB to account for total
degradations due to reflections, intersymbol interference, mode
partition noise, and laser chirp."
When dealing with multi-channel systems or systems with optical
amplifiers we may also need:
Optical signal-to-noise ratio: "The minimum value of optical SNR
required to obtain a 1x10-12 BER."[G.692]
Receiver wavelength range: "The receiver wavelength range is defined
as the acceptable range of wavelengths at point Rn. This range must
be wide enough to cover the entire range of central frequencies over
the OA passband." [G.692]
Minimum equivalent sensitivity: "This is the minimum sensitivity that
would be required of a receiver placed at MPI-RM in multichannel
applications to achieve the specified maximum BER of the application
code if all except one of the channels were to be removed (with an
ideal loss-less filter) at point MPI-RM." [G.959.1]
A.3. Components and Subsystems
Reference [G.671] "Transmission characteristics of optical components
and subsystems" covers the following components:
o optical add drop multiplexer (OADM) subsystem;
o asymmetric branching component;
o optical attenuator;
o optical branching component (wavelength non-selective);
o optical connector;
o dynamic channel equalizer (DCE);
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o optical filter;
o optical isolator;
o passive dispersion compensator;
o optical splice;
o optical switch;
o optical termination;
o tuneable filter;
o optical wavelength multiplexer (MUX)/demultiplexer (DMUX);
- coarse WDM device;
- dense WDM device;
- wide WDM device.
Reference [G.671] then specifies applicable parameters for these
components. For example an OADM subsystem will have parameters such
as: insertion loss (input to output, input to drop, add to output),
number of add, drop and through channels, polarization dependent
loss, adjacent channel isolation, allowable input power, polarization
mode dispersion, etc...
A.4. Network Elements
The previously cited ITU-T recommendations provide a plethora of
definitions and characterizations of optical fiber, devices,
components and subsystems. Reference [G.Sup39] "Optical system design
and engineering considerations" provides useful guidance on the use
of such parameters.
In many situations the previous models while good don't encompass the
higher level network structures that one typically deals with in the
control plane, i.e, "links" and "nodes". In addition such models
include the full range of network applications from planning,
installation, and possibly day to day network operations, while with
the control plane we are generally concerned with a subset of the
later. In particular for many control plane applications we are
interested in formulating the total degradation to an optical signal
as it travels through multiple optical subsystems, devices and fiber
segments.
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In reference [G.680] "Physical transfer functions of optical networks
elements", a degradation function is currently defined for the
following optical network elements: (a) DWDM Line segment, (b)
Optical Add/Drop Multiplexers (OADM), and (c) Photonic cross-connect
(PXC). The scope of [G.680] is currently for optical networks
consisting of one vendors DWDM line systems along with another
vendors OADMs or PXCs.
The DWDM line system of [G.680] consists of the optical fiber, line
amplifiers and any embedded dispersion compensators. Similarly the
OADM/PXC network element may consist of the basic OADM component and
optionally included optical amplifiers. The parameters for these
optical network elements (ONE) are given under the following
circumstances:
o General ONE without optical amplifiers
o General ONE with optical amplifiers
o OADM without optical amplifiers
o OADM with optical amplifiers
o Reconfigurable OADM (ROADM) without optical amplifiers
o ROADM with optical amplifiers
o PXC without optical amplifiers
o PXC with optical amplifiers
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6. References
6.1. Normative References
[G.650.1] ITU-T Recommendation G.650.1, Definitions and test methods
for linear, deterministic attributes of single-mode fibre
and cable, June 2004.
[650.2] ITU-T Recommendation G.650.2, Definitions and test methods
for statistical and non-linear related attributes of
single-mode fibre and cable, July 2007.
[650.3] ITU-T Recommendation G.650.3
[G.652] ITU-T Recommendation G.652, Characteristics of a single-mode
optical fibre and cable, June 2005.
[G.653] ITU-T Recommendation G.653, Characteristics of a dispersion-
shifted single-mode optical fibre and cable, December 2006.
[G.654] ITU-T Recommendation G.654, Characteristics of a cut-off
shifted single-mode optical fibre and cable, December 2006.
[G.655] ITU-T Recommendation G.655, Characteristics of a non-zero
dispersion-shifted single-mode optical fibre and cable,
March 2006.
[G.656] ITU-T Recommendation G.656, Characteristics of a fibre and
cable with non-zero dispersion for wideband optical
transport, December 2006.
[G.661] ITU-T Recommendation G.661, Definition and test methods for
the relevant generic parameters of optical amplifier
devices and subsystems, March 2006.
[G.662] ITU-T Recommendation G.662, Generic characteristics of
optical amplifier devices and subsystems, July 2005.
[G.671] ITU-T Recommendation G.671, Transmission characteristics of
optical components and subsystems, January 2005.
[G.680] ITU-T Recommendation G.680, Physical transfer functions of
optical network elements, July 2007.
[G.691] ITU-T Recommendation G.691, Optical interfaces for
multichannel systems with optical amplifiers, November
1998.
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[G.692] ITU-T Recommendation G.692, Optical interfaces for single
channel STM-64 and other SDH systems with optical
amplifiers, March 2006.
[G.872] ITU-T Recommendation G.872, Architecture of optical
transport networks, November 2001.
[G.957] ITU-T Recommendation G.957, Optical interfaces for
equipments and systems relating to the synchronous digital
hierarchy, March 2006.
[G.959.1] ITU-T Recommendation G.959.1, Optical Transport Network
Physical Layer Interfaces, March 2006.
[G.694.1] ITU-T Recommendation G.694.1, Spectral grids for WDM
applications: DWDM frequency grid, June 2002.
[G.694.2] ITU-T Recommendation G.694.2, Spectral grids for WDM
applications: CWDM wavelength grid, December 2003.
[G.Sup39] ITU-T Series G Supplement 39, Optical system design and
engineering considerations, February 2006. [RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945, October 2004.
[RFC4054] Strand, J., Ed., and A. Chiu, Ed., "Impairments and Other
Constraints on Optical Layer Routing", RFC 4054, May 2005.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[WSON-Frame] G. Bernstein, Y. Lee, W. Imajuku, "Framework for GMPLS
and PCE Control of Wavelength Switched Optical Networks",
work in progress: draft-ietf-ccamp-wavelength-switched-
framework-00.txt, July 2008.
[WSON-Info] G. Bernstein, Y. Lee, D. Li, W. Imajuku, "Routing and
Wavelength Assignment Information Model for Wavelength
Switched Optical Networks", work in progress: draft-ietf-
ccamp-rwa-info-00.txt, August 2008.
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6.2. Informative References
[Agrawal02] Govind P. Agrawal, Fiber-Optic Communications Systems -
Third Edition, Wiley-Interscience, 2002.
[Agrawal07] Govind P. Agrawal, Nonlinear Fiber Optics - Fourth
Edition, Academic Press, 2007.
[Imp-Info] G. Bernstein, Y. Lee, D. Li, "A Framework for the Control
and Measurement of Wavelength Switched Optical Networks
(WSON) with Impairments", work in progress: draft-
bernstein-wson-impairment-info-00.txt, October 2008.
[Martinelli] G. Martinelli (ed.) and A. Zanardi (ed.), "GMPLS
Signaling Extensions for Optical Impairment Aware Lightpath
Setup", Work in Progress: draft-martinelli-ccamp-optical-
imp-signaling-01.txt, February 2008.
[WD05] Malcolm Betts, Hing-Kam Lam, " Report of Q12/15 and Q14/15
Joint Interregnum Meeting in Beijing, 22 - 26 September
2008", Study Group 15, Question 12 & 14, WD 05r2, September
2008.
[WD24] Malcolm Betts, "Considerations on the model of media layer
networks", Study Group 15, Question 12, WD 24, September
2008.
Author's Addresses
Greg M. Bernstein (ed.)
Grotto Networking
Fremont California, USA
Phone: (510) 573-2237
Email: gregb@grotto-networking.com
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Young Lee (ed.)
Huawei Technologies
1700 Alma Drive, Suite 100
Plano, TX 75075
USA
Phone: (972) 509-5599 (x2240)
Email: ylee@huawei.com
Dan Li
Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base,
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28973237
Email: danli@huawei.com
Contributor's Addresses
Ming Chen
Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base,
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28973237
Email: mchen@huawei.com
Rebecca Han
Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base,
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28973237
Email: hanjianrui@huawei.com
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Acknowledgment
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