SIST EN 61280-2-11:2006

Fibre optic communication subsystem test procedures -- Part 2-11: Digital systems - Averaged Q-factor determination using amplitude histogram evaluation for optical signal quality monitoring

This part of IEC 61280 defines the averaged Q-factor and provides a procedure to measure it by using amplitude histogram parameters such as the standard deviation and average level.

Prüfverfahren für Lichtwellenleiter-Kommunikationsuntersysteme -- Teil 2-11: Digitale Systeme - Bestimmung des mittleren Q-Faktors durch Auswertung des Amplitudenhistogramms zur Qualitätsüberwachung optischer Signale

Procédures d'essai des sous-systèmes de télécommunications à fibres optiques -- Partie 2-11: Systèmes numériques - Détermination du facteur de qualité moyenné par l'évaluation d'histogramme d'amplitude pour la surveillance de la qualité des signaux optiques

La présente partie de la CEI 61280 définit le facteur de qualité moyenné et fournit une procédure pour le mesurer en utilisant les paramètres d'histogramme d'amplitude comme l'écart type et le niveau moyen.

Postopki preskušanja optičnega komunikacijskega podsistema – 2-11. del: Digitalni sistemi – Ugotavljanje s povprečno vrednostjo faktorja Q z uporabo ocenjevanja amplitudnega histograma za nadzorovanje kakovosti optičnega signala (IEC 61280-2-11:2006)

General Information

• Status: Published
• Publication Date: 30-Jun-2006
• ICS: 33.180.01 - Fibre optic systems in general
• Technical Committee: iTEL - Communication cables
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Jul-2006
• Due Date: 01-Jul-2006
• Completion Date: 01-Jul-2006
• Ref Project: EN 61280-2-11:2006 - Fibre optic communication subsystem test procedures - Part 2-11: Digital systems - Averaged Q-factor determination using amplitude histogram evaluation for optical signal quality monitoring

Standards Content (Sample)

SLOVENSKI SIST EN 61280-2-11:2006

STANDARD
julij 2006
Postopki preskušanja optičnega komunikacijskega podsistema – 2-11. del:
Digitalni sistemi – Ugotavljanje s povprečno vrednostjo faktorja Q z uporabo
ocenjevanja amplitudnega histograma za nadzorovanje kakovosti optičnega
signala (IEC 61280-2-11:2006)
Fibre optic communication subsystem test procedures – Part 2-11: Digital systems –
Averaged Q-factor determination using amplitude histogram evaluation for optical
signal quality monitoring (IEC 61280-2-11:2006)
ICS 33.180.01 Referenčna številka
SIST EN 61280-2-11:2006(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

---------------------- Page: 1 ----------------------

EUROPEAN STANDARD
EN 61280-2-11

NORME EUROPÉENNE
April 2006
EUROPÄISCHE NORM

ICS 33.180.10


English version


Fibre optic communication subsystem test procedures
Part 2-11: Digital systems -
Averaged Q-factor determination
using amplitude histogram evaluation
for optical signal quality monitoring
(IEC 61280-2-11:2006)


Procédures d'essai des sous-systèmes  Prüfverfahren für Lichtwellenleiter-
de télécommunications à fibres optiques Kommunikationsuntersysteme
Partie 2-11: Systèmes numériques - Teil 2-11: Digitale Systeme -
Détermination du facteur de qualité Bestimmung des mittleren Q-Faktors durch
moyenné par l'évaluation d'histogramme Auswertung des Amplitudenhistogramms
d'amplitude pour la surveillance zur Qualitätsüberwachung
de la qualité des signaux optiques optischer Signale
(CEI 61280-2-11:2006) (IEC 61280-2-11:2006)


This European Standard was approved by CENELEC on 2006-02-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, the Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels


© 2006 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61280-2-11:2006 E

---------------------- Page: 2 ----------------------

EN 61280-2-11:2006 - 2 -
Foreword
The text of document 86C/682FDIS, future edition 1 of IEC 61280-2-11, prepared by SC 86C, Fibre optic
systems and active devices, of IEC TC 86, Fibre optics, was submitted to the IEC-CENELEC parallel vote
and was approved by CENELEC as EN 61280-2-11 on 2006-02-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-11-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2009-02-01
The International Electrotechnical Commission (IEC) and CENELEC draw attention to the fact that it is
claimed that compliance with this document may involve the use of a patent concerning the averaged
Q-factor measurement.
The IEC and CENELEC take no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured the IEC that he is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In this
respect, the statement of the holder of this patent right is registered with the IEC. Information may be
obtained from:
NTT Corporation
Tokyo
Japan
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights other than those identified above. IEC and CENELEC shall not be held responsible for
identifying any or all such patent rights.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61280-2-11:2006 was approved by CENELEC as a European
Standard without any modification.
__________

---------------------- Page: 3 ----------------------

- 3 - EN 61280-2-11:2006
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year
1) 2)
IEC 61280-2-2 - Fibre optic communication subsystem test EN 61280-2-2 2005
procedures
Part 2-2: Digital systems - Optical eye
pattern, waveform and extinction ratio
measurement

1)
ITU-T - Optical transport network physical layer
Recommendation interfaces
G.959.1


1)
Undated reference.
2)
Valid edition at date of issue.

---------------------- Page: 4 ----------------------

NORME CEI
INTERNATIONALE
IEC



61280-2-11
INTERNATIONAL


Première édition
STANDARD

First edition

2006-01


Procédures d'essai des sous-systèmes de
télécommunications à fibres optiques –
Partie 2-11:
Systèmes numériques – Détermination du facteur
de qualité moyenné par l'évaluation d'histogramme
d'amplitude pour la surveillance de la qualité des
signaux optiques

Fibre optic communication subsystem
test procedures –
Part 2-11:
Digital systems – Averaged Q-factor determination
using amplitude histogram evaluation for optical
signal quality monitoring

 IEC 2006 Droits de reproduction réservés  Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch
CODE PRIX
V
PRICE CODE
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue

---------------------- Page: 5 ----------------------

61280-2-11  IEC:2006 – 3 –
CONTENTS
FOREWORD.7
0 INTRODUCTION .11
0.1 Background.11
0.2 Averaged Q-factor formula .13

1 Scope.15
2 Normative references .15
3 Terms and definitions .17
4 Abbreviated terms .17
5 Apparatus.17
5.1 Optical bandpass filter.19
5.2 Receiver.19
5.3 Clock oscillator.21
5.4 Electrical pulse generator.21
5.5 Sampling module.21
5.6 Signal processing circuit.23
5.7 Monitoring system parameters.23
6 Procedure .23
6.1 Equipment connections .23
6.2 Threshold level definitions.23
7 Calculations .25

Annex A (normative) Measurement accuracy, reliability, and sensitivity .33
Annex B (informative) Crosstalk and frequency detuning of optical bandpass filter .39
Annex C (normative) Highest limit of Q .47
avg
Annex D (informative) Bit rate dependence .51
Annex E (informative) Format dependence .53
Annex F (informative) Dependence of Q σ |µ – µ |, and Q on chromatic
avg, 1,avg, 1,avg 0,avg
dispersion and OSNR .57
Annex G (informative) Relationship between Q and Q with PMD impairment .61
ave

Bibliography.65

Figure 1 – Asynchronous eye-pattern and amplitude histogram .13
Figure 2 – Averaged Q-factor measurement configuration.19
Figure 3 – Dependence of Q on Q for different α, when T = 1/4 × T s, B = 0,75
avg r slot re
14
× B Hz, B = 4 × B Hz, T = 1/256 × T s, N = 16 384 (2 ).29
opt res slot samp
Figure 4 – Dependence of R on α, when T = 1/4 × T s, B = 0,7 × B Hz, B = 4 ×
r slot re opt
14
B Hz, T = 1/256 × T s, N = 16 384 (2 ) .29
res slot samp
Figure 5 – Dependence of optimum value of α on B , when T = 1/4 × T s, B =
opt r slot re
14
0,75 × B Hz, T = 1/64 × T s, N = 16 384(2 ).31
res slot samp

---------------------- Page: 6 ----------------------

61280-2-11  IEC:2006 – 5 –
Figure A.1 – Definition of ΔQ and ΔQ.33
avg
Figure A.2 – Dependence of the standard deviation of Q on N : T = 1/4 × T s,
avg samp r slot
–10
B = 0,7× B Hz, B = 4 × B Hz, T = 1/256 × T s, α = 0,3, Q = 16 dB (BER~10 ) .35
re opt res slot
Figure A.3 – Dependence of linear fitting slope of Q versus Q on B : T = 1/4 × T s,
avg opt r slot
B = 0,7 × B Hz, T = 1/256 × T s, α = 0,3.37
re res slot
Figure A.4 – Dependence of the standard deviation of eight measurement points of
14
Q on T : T = 1/4 × T s, B = 0,75 × B Hz, B = 4 × B Hz, N = 16 384(2 ),
avg res r slot re opt samp
–10
α = 0,3, Q = 16 dB (BER ~ 10 ).37
Figure B.1 – Definition of WDM signal and OBPF frequency response .39
Figure B.2 – Δf dependence of Q and Q for Δf of 100 GHz(a), 50 GHz(b),
obpf avg WDM
and 25 GHz(c) .41
Figure B.3 – Definition of OBPF central frequency detuning δf .43
c
Figure B.4 – δf dependence of Q for Δf of 100 GHz(a), 50 GHz(b), and
c avg WDM
25 GHz(c) .45
Figure C.1 – Dependence of Q on Q when B is 10 Gbit/s: T = 1/4 × T s,
avg r slot
14
B = 0,75 x B Hz, B = 4 x B GHz, T = 1/256 × T s, N = 16 384(2 ), α = 0,3.47
re opt res slot samp
Figure C.2 – Dependence of the highest limit of Q on rise time after O/E converter .49
avg
Figure D.1 – Example of relationship between Q and Q for different bit rates.51
avg
Figure E.1 – Dependence of Q on Q when D = 0 ps/nm, R = 0,4, B = 0,6 × B Hz,
avg duty re
14
B = 240 GHz, T = 1/64 × T s, N = 16 384(2 ) and α = 0,2 or 0,3 .53
opt res slot samp
Figure E.2 – Dependence of Q on Q when D = 1 020 ps/nm, R = 0,4, B = 0,6 × B Hz,
avg duty re
14
B = 240 GHz, T = 1/64 × T s, N = 16 384(2 ) and α = 0,2 or 0,3 .55
opt res slot samp
Figure F.1 (a) Chromatic dispersion dependence and (b) OSNR dependence of σ ,
1
µ -µ and Q for 10-Gbit/s NRZ optical signals when B is 40 GHz and α is 0,3.57
1 0 avg opt
Figure F.2 (a) Chromatic dispersion dependence and (b) OSNR dependence of σ ,
1
µ -µ and Q for 10-Gbit/s NRZ optical signals when B is 240 GHz and α is 0,2.57
1 0 avg opt
Figure G.1 – Dependence of Q on Q when mean DGD = 30 ps .61
avg
Figure G.2 – Histogram of Q when Q ranges from 18,5 dB to 18,7dB.63
avg

Table 1 – Monitoring system parameters.23
Table D.1 – Values of T , B , B and T .51
r re opt res

---------------------- Page: 7 ----------------------

61280-2-11  IEC:2006 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

FIBRE OPTIC COMMUNICATION SUBSYSTEM
TEST PROCEDURES –

Part 2-11: Digital systems –
Averaged Q-factor determination using amplitude histogram
evaluation for optical signal quality monitoring


FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
The International Electrotechnical Commission (IEC) draws attention to the fact that it is claimed that compliance
with this document may involve the use of a patent concerning the averaged Q-factor measurement.
IEC takes no position concerning the evidence, validity and scope of this patent right.
The holders of this patent right have assured the IEC that they are willing to negotiate licenses under reasonable
and non-discriminatory terms and conditions with applicants throughout the world. In this respect, the statement of
the holder of this patent right is registered with the IEC. Information may be obtained from:
NTT Corporation
Tokyo
Japan
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights other than those identified above. IEC shall not be held responsible for identifying any or all such
patent rights.

---------------------- Page: 8 ----------------------

61280-2-11  IEC:2006 – 9 –
International Standard IEC 61280-2-11 has been prepared by subcommittee 86C: Fibre optic
systems and active devices, of IEC technical committee 86: Fibre optics.
The text of this standard is based on the following documents:
FDIS Report on voting
86C/682/FDIS 86C/687/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
IEC 61280 consists of the following parts under the general title Fibre optic communication
1)
subsystem test procedures :
2)
Part 1: General communication subsystems
3)
Part 2: Digital systems
4)
Part 4: Cable plant and links
Part 3 is in preparation.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
—————————
1)
The general title of the IEC 61280 series has changed. Previous parts were published under the general title
Fibre optic communication subsystem basic test procedures
2) The title of Part 1 has changed. Parts 1–1 and 1–3 were published under the title Test procedures for general
communication subsystems.
3) The title of Part 2 has changed. Parts 2–1, 2–2, 2–4 and 2–5 were published under the title Test procedures for
digital systems.
4) The title of Part 4 has changed. Part 4–2 was published under the title Fibre optic cable plant.

---------------------- Page: 9 ----------------------

61280-2-11  IEC:2006 – 11 –
0 INTRODUCTION
0.1 Background
Signal quality monitoring is an important issue for operation and maintenance of optical
transport networks (OTN). From the network operator’s point of view, monitoring techniques
are required to establish connections, protection, restoration, and/or service level
agreements. In order to establish these functions, the monitoring techniques used should
satisfy some general requirements: in-service (non-intrusive) measurement, signal
deterioration detection (both SNR degradation and waveform distortion), fault isolation
(localize impaired sections or nodes), transparency and scalability (irrespective of the signal
bit rate and signal formats), and simplicity (small size and low cost).
There are several approaches, both analog and digital techniques, that make it possible to
detect various impairments: bit error rate (BER) estimation [1,2], error block detection, optical
power measurement, optical SNR evaluation with spectrum measurement [3, 4], pilot tone
detection [5,6], Q-factor monitoring [7], pseudo BER estimation using two decision circuits
[8,9], and histogram evaluation with synchronous eye diagram measurement [10]. A
fundamental performance monitoring parameter of any digital transmission system is its end-
to-end BER. However, the BER can be correctly evaluated only with outside service BER
measurements, using a known test bit pattern in place of the real signal. On the other hand,
in-service measurement can only provide rough estimates through the measurement of digital
parameters (e.g., BER estimation, error block detection, and error count in forward error
correction) or analog parameters (e.g., optical SNR and Q-factor).
What has been much desired and studied is some methods for signal quality monitoring that
will provide a good measure of signal quality without the complexity of termination. When the
system BER is too low to be measured within a reasonable length of time, it is useful to adopt
Q-factor measurements. However, all sampling-based methods require synchronization and
then some analysis, which makes them similar to protocol-aware termination in terms of cost
and complexity. In fact, synchronous sampling requires timing extraction by complex
equipment that is specific to each BER and each format.
The above situation has, fortunately, very recently begun to change. A simple, asynchronous
histogram method was developed for Q-factor measurement [11],[12]. Different degradation
types (i.e., SNR degradation and wavelength distortion due to chromatic dispersion) can be
monitored [13], thus providing information about the origin of the degradations [14].
Asynchronous sampling allows bit-rate independent Q-factor monitoring, and the same
equipment covers bit rates of up to 160 Gbit/s [15]. Moreover, the monitoring is applied to
both NRZ and RZ optical signals [11], and is independent of the bit rate and signal format
used by the wavelength division multiplexed (WDM) channel [16]. Performance monitoring can
be performed at different monitoring points such as optical line repeaters, regenerators, or
optical switching nodes (requires pre-measurement) [17]. In other words, this method is
expected to be applied to the monitoring points where electrical termination is impossible. If
we think of the future all-optical network, an optical switching node has performance
monitoring without electrical regeneration.
Average Q-factor, Q , measurement through asynchronous sampling is a cost-effective
avg
alternative to BER measurements. This is one of the promising performance-monitoring
approaches for intensity modulated direct detection (IM-DD) optical transmission systems. This
method can be utilized for monitoring both relative and absolute values of optical signal quality.

---------------------- Page: 10 ----------------------

61280-2-11  IEC:2006 – 13 –
With the averaged Q-factor obtained from amplitude histogram parameters (the standard
deviation and average level), the over-all effect of the optical signal quality degradations due
to the integral of the causes (such as ASE and Chromatic dispersion) can be monitored. Due
to asynchronous sampling scheme, the averaged Q-factor is insensitive to the optical signal
quality variations created by timing jitter. The following sections define the averaged Q-factor
and provide a procedure to measure the optical signal quality via the averaged Q-factor. With
the amplitude histogram parameters, it is also possible to distinguish the origins of the BER
degradation (SNR degradation, waveform distortion). The information about the dependence
of the amplitude histogram parameters on OSNR and chromatic dispersion is shown in Annex
F (informative).
0.2 Averaged Q-factor formula
Figure 1 uses a typical asynchronous eye-pattern and its amplitude histogram, obtained by
asynchronous optical sampling, to illustrate the principle of this method. Among the sampling
points that constitute the histogram, it is determined that those points whose level is higher
than a predetermined threshold level, µ , belong to level "Mark" (i.e., "1"), while those points
th1
whose level is lower than a predetermined threshold level, µ , belong to level "Space" (i.e.,
th0
"0").
The averaged Q-factor, Q , is defined by
avg
Q = |µ – µ |/( σ + σ ) (1)
avg 1,avg 0,avg 1,avg 0,avg
where µ and σ are the mean and standard deviation of the Mark (i = 1) and Space
i,avg i,avg
level (i = 0) distributions, respectively [12-17]. The data obtained by asynchronous sampling
includes unwanted cross-point data in the eye-diagram, which decreases the measured value
of the averaged Q-factor. The two threshold levels are set (µ and µ ) in order to remove
th1 th0
the cross-point data.
Amplitude
σ
Mark
1,avg
µ

1,avg
σµ

µ
Thresholds
σµ

µ

0,avg
Space
σ

0,avg
Time
Number of times
IEC  2563/05

Figure 1 – Asynchronous eye-pattern and amplitude histogram
The essence of this method is that timing extraction is not used and asynchronous eye
diagrams are evaluated. That is why this method provides signal format, modulation format
and bit rate flexibility.

---------------------- Page: 11 ----------------------

61280-2-11  IEC:2006 – 15 –
FIBRE OPTIC COMMUNICATION SUBSYSTEM
TEST PROCEDURES –

Part 2-11: Digital systems –
Averaged Q-factor determination using amplitude histogram
evaluation for optical signal quality monitoring



1 Scope
This part of IEC 61280 defines the averaged Q-factor and provides a procedure to measure it
by using amplitude histogram parameters such as the standard deviation and average level.
The averaged Q-factor and amplitude histogram parameters are useful for monitoring changes
in optical signal quality in installed optical networks. The average Q-factor is correlated with
the traditional Q parameter of a given optical channel.
With the averaged Q-factor test method signal, quality degradations due to optical signal-to-
noise ratio (OSNR) degradation and to waveform distortion can be monitored:
• OSNR degradation, due to the following causes:
– accumulation of amplified spontaneous emission (ASE);
– transmission line loss;
– channel crosstalk;
• waveform distortion, due to the following causes (usually simultaneously present):
– chromatic dispersion;
– polarization mode dispersion (PMD);
– optical nonlinear effects.
NOTE 1 In some cases the main cause of signal degradation (OSNR degradation or waveform distortion) can be
identified by suitable processing of the measured data
NOTE 2 This method is insensitive to the optical signal quality variations created by timing jitter.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 61280-2-2: Fibre optic communication subsystem basic test procedures – Part 2-2: Test
procedures for digital systems – Optical eye pattern, waveform, and extinction ratio
ITU-T Recommendation G.959.1: Optical transport network physical layer interfaces

---------------------- Page: 12 ----------------------

61280-2-11  IEC:2006 – 17 –
3 Terms and definitions
For the purposes of this document, the following term and definition apply.
3.1
averaged Q-factor
parameter measured asynchronously on live optical digital signals for the purpose of
monitoring the quality of those signals
N
...