Calibration of wavelength/optical frequency measurement instruments - Part 3: Optical frequency meters internally referenced to a frequency comb (IEC 62129-3:2019)

This part of IEC 62129 describes the calibration of optical frequency meters using an optical
frequency comb as an internal reference. It is applicable to instruments measuring the optical
frequency emitted from sources that are typical for the fibre-optic communications industry. It
is assumed that the optical radiation will be coupled to the optical frequency meter by a singlemode
optical fibre. This document is part of the IEC 62129 series on the calibration of
wavelength/optical frequency measurement instruments. Refer to IEC 621291
[3] for the
calibration of optical spectrum analyzers, and refer to IEC 62129-2 [4] for calibration of
Michelson interferometer single wavelength meters.

Kalibrierung von Messgeräten für die Wellenlänge/optische Frequenz –Teil 3: Optisches Frequenzmessgerät mit internem Bezug auf einen Frequenzkamm (IEC 62129-3:2019)

Étalonnage des appareils de mesure de longueur d'onde/appareil de mesure de la fréquence optique - Partie 3: Fréquencemètres optiques faisant référence en interne à un peigne de fréquence (IEC 62129-3:2019)

IEC 62129-3:2019 décrit l'étalonnage des fréquencemètres optiques à l'aide d'un peigne de fréquence optique en référence interne. Elle s'applique aux appareils de mesure de la fréquence optique provenant des sources habituelles dans les secteurs des communications à fibres optiques. Il est pris pour hypothèse que le rayonnement optique est couplé au fréquencemètre optique par une fibre optique unimodale. Le présent document fait partie de la série IEC 62129 relative à l'étalonnage des appareils de mesure de longueur d'onde/appareils de mesure de la fréquence optique. Voir l'IEC 62129­1 [3] pour l'étalonnage des analyseurs de spectre optique, et l'IEC 62129­2 [4] pour l'étalonnage des appareils de mesure de longueur d'onde unique à interféromètre de Michelson. Cette première édition annule et remplace l'IEC TS 62129-3, parue en 2014. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente. a) un texte a été ajouté en 5.2.3 concernant l'étalonnage à une seconde fréquence optique; b) l'Annexe D est désormais normative; c) Le paragraphe 4.2 a été amélioré; d) la méthode de mesure de la fréquence a été déplacée à l'Annexe B; e) l'exemple de peigne de fréquence optique a été déplacé à l'Annexe C; f) l'incertitude de dépendance à la fréquence a été déplacée à l'Annexe D. Mots clés : étalonnage des fréquencemètres optiques

Umerjanje valovno-dolžinskih/optično-frekvenčnih merilnih instrumentov - 3. del: Merilniki optične frekvence z notranjo referenco na frekvenčni glavnik (IEC 62129-3:2019)

Ta del standarda IEC 62129 opisuje umerjanje merilnika optične frekvence z optičnim frekvenčnim glavnikom kot notranjo referenco. Uporablja se za instrumente za merjenje optične frekvence, ki jo oddajajo viri, značilni za industrijo opreme za komunikacijo po optičnih vlaknih. Domneva se, da bo optično sevanje združeno z merilnikom optične frekvence prek enorodovnega optičnega vlakna. Ta dokument je del skupine standardov IEC 62129 o umerjanju instrumentov za merjenje valovne dolžine/optične frekvence. Glej IEC 621291 [3] za
umerjanje analizatorjev optičnega spektra in glej IEC 62129-2 [4] za umerjanje merilnikov enotne valovne dolžine z Michelsonovim interferometrom.

General Information

Status
Published
Publication Date
18-Aug-2019
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
25-Jul-2019
Due Date
29-Sep-2019
Completion Date
19-Aug-2019

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SLOVENSKI STANDARD
SIST EN IEC 62129-3:2019
01-oktober-2019
Umerjanje valovno-dolžinskih/optično-frekvenčnih merilnih instrumentov - 3. del:

Merilniki optične frekvence z notranjo referenco na frekvenčni glavnik (IEC 62129-

3:2019)

Calibration of wavelength/optical frequency measurement instruments - Part 3: Optical

frequency meters internally referenced to a frequency comb (IEC 62129-3:2019)

Kalibrierung von Messgeräten für die Wellenlänge/optische Frequenz –Teil 3: Optisches

Frequenzmessgerät mit internem Bezug auf einen Frequenzkamm (IEC 62129-3:2019)
Étalonnage des appareils de mesure de longueur d'onde/appareil de mesure de la

fréquence optique - Partie 3: Fréquencemètres optiques faisant référence en interne à

un peigne de fréquence (IEC 62129-3:2019)
Ta slovenski standard je istoveten z: EN IEC 62129-3:2019
ICS:
17.180.30 Optični merilni instrumenti Optical measuring
instruments
33.180.01 Sistemi z optičnimi vlakni na Fibre optic systems in
splošno general
SIST EN IEC 62129-3:2019 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN IEC 62129-3:2019
---------------------- Page: 2 ----------------------
SIST EN IEC 62129-3:2019
EUROPEAN STANDARD EN IEC 62129-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2019
ICS 33.180.01
English Version
Calibration of wavelength/optical frequency measurement
instruments - Part 3:Optical frequency meters internally
referenced to a frequency comb
(IEC 62129-3:2019)

Étalonnage des appareils de mesure de longueur Kalibrierung von Messgeräten für die Wellenlänge/optische

d'onde/appareil de mesure de la fréquence optique - Partie Frequenz -Teil 3: Optisches Frequenzmessgerät mit

3: Fréquencemètres optiques faisant référence en interne à internem Bezug auf einen Frequenzkamm

un peigne de fréquence (IEC 62129-3:2019)
(IEC 62129-3:2019)

This European Standard was approved by CENELEC on 2019-06-24. 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 CEN-CENELEC

Management Centre 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 CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the

Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN IEC 62129-3:2019 E
---------------------- Page: 3 ----------------------
SIST EN IEC 62129-3:2019
EN IEC 62129-3:2019 (E)
European foreword

The text of document 86/551/FDIS, future edition 1 of IEC 62129-3, prepared by IEC/TC 86 "Fibre optics" was

submitted to the IEC-CENELEC parallel vote and approved by CENELEC as EN IEC 62129-3:2019.

The following dates are fixed:

• latest date by which the document has to be implemented at national level by (dop) 2020-03-24

publication of an identical national standard or by endorsement

• latest date by which the national standards conflicting with the (dow) 2022-06-24

document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice

The text of the International Standard IEC 62129-3:2019 was approved by CENELEC as a European Standard

without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards indicated:

IEC 62129-1 NOTE Harmonized as EN 62129-1
IEC 62129-2:2011 NOTE Harmonized as EN 62129-2:2011 (not modified)
ISO/IEC 17025 NOTE Harmonized as EN ISO/IEC 17025
IEC 61315 NOTE Harmonized as EN IEC 61315
IEC 60359 NOTE Harmonized as EN 60359
---------------------- Page: 4 ----------------------
SIST EN IEC 62129-3:2019
EN IEC 62129-3:2019 (E)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents are referred to in the text in such a way that some or all of their content constitutes

requirements 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 1 Where an International Publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here: www.cenelec.eu.

Publication Year Title EN/HD Year
IEC 60793-2-50 - Optical fibres - Part 2-50: Product EN IEC 60793-2- -
specifications - Sectional specification for 50
class B single-mode fibres
IEC 60825-1 - Safety of laser products - Part 1: Equipment EN 60825-1 -
classification and requirements
IEC 60825-2 - Safety of laser products - Part 2: Safety of EN 60825-2 -
optical fibre communication systems (OFCS)
IEC/TR 61931 - Fibre optic - Terminology - -
ISO/IEC Guide 98-3 2008 Uncertainty of measurement - Part 3: Guide - -
to the expression of uncertainty in
measurement (GUM:1995)
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SIST EN IEC 62129-3:2019
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SIST EN IEC 62129-3:2019
IEC 62129-3
Edition 1.0 2019-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Calibration of wavelength / optical frequency measurement instruments –
Part 3: Optical frequency meters internally referenced to a frequency comb
Étalonnage des appareils de mesure de longueur d'onde / appareil de mesure de
la fréquence optique –
Partie 3: Fréquencemètres optiques faisant référence en interne à un peigne de
fréquence
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.01 ISBN 978-2-8322-6922-0

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 7 ----------------------
SIST EN IEC 62129-3:2019
– 2 – IEC 62129-3:2019  IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 3

INTRODUCTION ..................................................................................................................... 5

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms and definitions ...................................................................................................... 6

4 Calibration test requirements ........................................................................................... 8

4.1 Organization ........................................................................................................... 8

4.2 Traceability ............................................................................................................. 8

4.3 Preparation ............................................................................................................. 8

4.4 Reference calibration conditions ............................................................................. 8

5 Optical frequency calibration ........................................................................................... 8

5.1 Establishing the calibration conditions .................................................................... 8

5.2 Calibration procedure .............................................................................................. 9

5.2.1 General ........................................................................................................... 9

5.2.2 Measurement configuration .............................................................................. 9

5.2.3 Detailed procedure ........................................................................................ 10

5.3 Calibration uncertainty .......................................................................................... 10

5.4 Reporting the results ............................................................................................. 11

6 Absolute power calibration ............................................................................................. 11

Annex A (normative) Mathematical basis for measurement uncertainty calculations ............. 12

A.1 General ................................................................................................................. 12

A.2 Type A evaluation of uncertainty ........................................................................... 12

A.3 Type B evaluation of uncertainty ........................................................................... 12

A.4 Determining the combined standard uncertainty .................................................... 13

A.5 Reporting .............................................................................................................. 14

Annex B (informative) Measurement method for the frequency of a stabilized laser

with an optical frequency comb ............................................................................................. 15

Annex C (informative) Examples of stabilized optical frequency comb source ...................... 17

C.1 Method A (pump pulse source and nonlinear optical effect) ................................... 17

C.2 Method B (stabilized laser and electro-optical modulator) ..................................... 17

Annex D (normative) Frequency-dependence of uncertainty ................................................ 19

Bibliography .......................................................................................................................... 20

Figure 1 – Optical frequency meter measurement using a reference source ............................ 9

Figure 2 – Optical frequency meter measurement using a reference optical frequency

meter .................................................................................................................................... 10

Figure B.1 – Schematic configuration of optical frequency measurement technique

using an optical comb ........................................................................................................... 15

Figure B.2 – Optical spectra of lasers and optical frequency combs ...................................... 16

Figure C.1 – Pump pulse source and nonlinear optical effect ................................................ 17

Figure C.2 – Electro-optical modulator type comb source ...................................................... 18

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SIST EN IEC 62129-3:2019
IEC 62129-3:2019  IEC 2019 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CALIBRATION OF WAVELENGTH /
OPTICAL FREQUENCY MEASUREMENT INSTRUMENTS –
Part 3: Optical frequency meters internally
referenced to a frequency comb
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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

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.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent

rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 62129-3 has been prepared by IEC technical committee 86: Fibre

optics.
This first edition cancels and replaces IEC TS 62129-3, published in 2014.

This edition includes the following significant technical changes with respect to the previous

edition:
a) text has been added to 5.2.3 about calibration at a second optical frequency;
b) Annex D is now normative;
c) Subclause 4.2 has been improved;
d) measurement method of frequency has been moved to Annex B;
e) example of optical frequency comb has been moved to Annex C;
f) frequency-dependence uncertainty has been moved to Annex D.
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SIST EN IEC 62129-3:2019
– 4 – IEC 62129-3:2019  IEC 2019
The text of this International Standard is based on the following documents:
FDIS Report on voting
86/551/FDIS 86/554/RVD

Full information on the voting for the approval of this International Standard can be found in the

report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 62129 series, published under the general title Calibration of

wavelength/optical frequency measurement instruments, can be found on the IEC website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct understanding

of its contents. Users should therefore print this document using a colour printer.

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SIST EN IEC 62129-3:2019
IEC 62129-3:2019  IEC 2019 – 5 –
INTRODUCTION

It is essential for realizing fibre optic systems that optical channels are defined in the optical

frequency domain, not the wavelength domain. One example: the anchor frequency of the ITU-

T grid is 193,1 THz, and the channel spacings of the ITU-T grid are 12,5 GHz, 25 GHz, 50 GHz,

and 100 GHz [1] .

ITU-T has also discussed λ-interface systems such as "black link" [2]. "Black link" includes

WDM MUX/DEMUX and a transmission fibre, and provides λ-interfaces. Especially in DWDM

systems (channel spacing < 100 GHz), the uncertainty in specifying optical frequency needs to

be minimized.

To implement future telecom systems, it is expected that optical frequency measurements will

need to be extremely precise. For example, to achieve the channel spacing of 25 GHz, signal

optical frequency uncertainty (Uf ) and required measurement uncertainty (Uf ) need to be

sig meas
-5 -6 -6 -8
2 GHz to 200 MHz (Uf / f = 10 to 10 ) and 200 MHz to 2 MHz (Uf / f = 10 to 10 ),
sig meas

respectively. Unfortunately, conventional wavelength meters have measurement uncertainties

-6 -7

of 10 to 10 . The solution is to use optical frequency measurements since measurement

uncertainties can be as small as 10 , which satisfies the above telecom requirement

-6 -8

(Uf / f = 10 to 10 ). Therefore, an optical frequency measurement scheme is necessary

meas
for the calibration of future telecom systems.

The frequency meter to calibrate with the procedure described in this document is the

measurement equipment internally utilizing the optical frequency comb. In Annex A, the

mathematical basis for the uncertainty of measurement is described. The measurement

procedure of the frequency with the frequency meter utilizing the optical frequency comb is

shown in Annex B and the example of the optical frequency comb sources are shown in Annex C.

Additionally, the uncertainty depending on the frequency is shown in Annex D.

This document defines all the steps involved in the calibration process of the frequency

measuring with the optical frequency meter internally utilizing an optical frequency comb:

establishing the calibration conditions, carrying out the calibration, calculating the uncertainty,

and reporting the uncertainty, the calibration conditions and the traceability.
____________
Numbers in square brackets refer to the Bibliography.
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SIST EN IEC 62129-3:2019
– 6 – IEC 62129-3:2019  IEC 2019
CALIBRATION OF WAVELENGTH /
OPTICAL FREQUENCY MEASUREMENT INSTRUMENTS –
Part 3: Optical frequency meters internally
referenced to a frequency comb
1 Scope

This part of IEC 62129 describes the calibration of optical frequency meters using an optical

frequency comb as an internal reference. It is applicable to instruments measuring the optical

frequency emitted from sources that are typical for the fibre-optic communications industry. It

is assumed that the optical radiation will be coupled to the optical frequency meter by a single-

mode optical fibre. This document is part of the IEC 62129 series on the calibration of

wavelength/optical frequency measurement instruments. Refer to IEC 62129-1 [3] for the

calibration of optical spectrum analyzers, and refer to IEC 62129-2 [4] for calibration of

Michelson interferometer single wavelength meters.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements 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 60793-2-50, Optical fibres – Part 2-50: Product specifications – Sectional specification for

class B single-mode fibres

IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements

IEC 60825-2, Safety of laser products – Part 2: Safety of optical fibre communication systems

(OFCS)
IEC TR 61931, Fibre optic – Terminology

ISO/IEC Guide 98-3:2008, Uncertainty of measurement – Part 3: Guide to the expression of

uncertainty in measurement (GUM:1995)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC TR 61931, and the

following apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
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SIST EN IEC 62129-3:2019
IEC 62129-3:2019  IEC 2019 – 7 –
3.1
accredited calibration laboratory

calibration laboratory authorized by the appropriate national organization to issue calibration

certificates with a minimum specified uncertainty, which demonstrate traceability to national

measurement standards (3.3)
3.2
calibration

set of operations that establish, under specified conditions, the relationship between the values

of quantities indicated by a measuring instrument and the corresponding values realized by

measurement standards

Note 1 to entry: The result of a calibration permits either the assignment of values of measurands to the indications

or the determination of corrections with respect to indications.

Note 2 to entry: A calibration may also determine other metrological properties such as the effect of influence

quantities.

Note 3 to entry: The result of a calibration may be recorded in a document, sometimes called a calibration certificate

or a calibration report.

[SOURCE: ISO/IEC Guide 99:2007 [5], 2.39, modified – Only the first part of the definition has

been used and the notes to entry have been modified.]
3.3
national measurement standard

standard recognized by a national decision to serve, in a country, as the basis for assigning

values to other standards for the quantity concerned

[ISO/IEC Guide 99:2007, 5.3, modified – Some terms have been replaced with similar meaning.]

3.4
reference standard

standard, generally having the highest metrological quality available at a given location or in a

given organization, from which measurements made therein are derived

Note 1 to entry: The general definition of this term is described in ISO/IEC Guide 99:2007, 5.6.

3.5
traceability

property of the result of a measurement or the value of a measurement standard whereby it can

be related to stated references, usually national or international measurement standards,

through an unbroken chain of comparisons all having stated uncertainties

Note 1 to entry: The general definition of this term is described in ISO/IEC Guide 99:2007, 2.41.

3.6
traceability chain
unbroken chain of comparison

Note 1 to entry: The general definition of this term is described in ISO/IEC Guide 99:2007, 2.42.

3.7
working standard

measurement standard that is used routinely to calibrate or check measuring instruments

Note 1 to entry: A working standard is usually calibrated against a reference standard.

Note 2 to entry: The general definition of this term is described in ISO/IEC Guide 99:2007, 5.7.

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SIST EN IEC 62129-3:2019
– 8 – IEC 62129-3:2019  IEC 2019
4 Calibration test requirements
4.1 Organization

The calibration laboratory should ensure that suitable requirements for calibration are followed.

NOTE Guidance about good practices for calibration can be found in ISO/IEC 17025 [6].

There shall be a documented measurement procedure for each type of calibration performed,

giving step-by-step operating instructions and equipment to be used.
4.2 Traceability

The calibration laboratory should ensure that suitable requirements for traceability are followed.

NOTE Guidance about good practices for traceability can be found in ISO/IEC 17025.

Make sure that any test equipment which has a significant influence on the calibration results

is calibrated. Upon request, specify this test equipment and its calibration chain(s). The

recalibration period(s) shall be defined and documented.
4.3 Preparation

The environmental conditions shall be commensurate with the degree of uncertainty that is

required for calibration:
a) the environment shall be clean;
b) temperature monitoring and control is required;

c) all laser sources shall be safely operated (refer to IEC 60825-1 and to IEC 60825-2).

4.4 Reference calibration conditions

The reference calibration conditions usually include the following parameters and, if necessary,

their tolerance bands: date, temperature, relative humidity, displayed power level, displayed

optical frequency, fibre, (spectral) bandwidth and resolution bandwidth (spectral resolution) set.

Unless otherwise specified, use a single-mode optical fibre input pigtail as specified in

IEC 60793-2-50, having a length of at least 2 m.

The calibration should be made in a temperature-controlled environment. The recommended

temperature is 23 °C. Depending on the desired uncertainty, the temperature, atmospheric

pressure and humidity may need to be monitored during the measurement.

Operate the optical frequency meter in accordance with the manufacturer's specifications and

operating procedures. Where practical, select a range of test conditions and parameters which

emulate the actual field operating conditions of the optical frequency meter under test. Choose

these parameters so as to optimize the optical frequency meter's uncertainties, as specified by

the manufacturer's operating procedures.

NOTE The calibration results only apply to the set of test conditions used in the calibration process.

5 Optical frequency calibration
5.1 Establishing the calibration conditions

Establishing and maintaining the calibration conditions is an important part of the calibration,

because any change of these conditions is capable of producing erroneous measurement

results. The calibration conditions should be a close approximation to the intended operating

conditions. This ensures that the (additional) uncertainty in the operating environment is as

small as possible. The calibration conditions should be specified in the form of nominal values

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SIST EN IEC 62129-3:2019
IEC 62129-3:2019  IEC 2019 – 9 –

with uncertainties when applicable. In order to meet the requirements of this document, the

calibration conditions shall at least consist of:
a) date of calibration;

b) ambient temperature, for example 23 °C. The temperature may need to be monitored

continuously to ensure that it remains within the requisite limits;

c) ambient relative humidity, for example 30 % to 70 %. The ambient relative humidity may

need to be monitored continuously to ensure that it remains within the requisite limits. A

relative humidity below the condensation point is assumed by default;

d) input optical power (that has to fall within the allowable specification for the optical

frequency meters);

e) if a transition locked source is used, then the quality of the lock shall be continuously

monitored during the measurements; a lock indicator can be sufficient.

The above conditions may not be exhaustive. There might be other parameters that have a

significant influence on the calibration uncertainty.
5.2 Calibration procedure
5.2.1 General
The main steps of the calibration procedure are as follows:

a) establish and record the appropriate calibration conditions (see 5.1). Switch on all

instrumentation and wait until it stabilizes;
b) set up the reference source in accordance with condition 5.1 d);

c) set up the instrument state of the test optical frequency meter according to the instruction

manual. Select appropriate units;
d) record the instrument states of the optical frequency meter.
5.2.2 Measurement configuration
Two possible configurations can be used for calibration. One uses
...

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