EN 62129:2006

SLOVENSKI SIST EN 62129:2006
STANDARD
julij 2006
Umerjanje analizatorjev optičnega spektra (IEC 62129:2006)
Calibration of optical spectrum analyzers (IEC 62129:2006)
ICS 33.180.01 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

EUROPEAN STANDARD
EN 62129
NORME EUROPÉENNE
March 2006
EUROPÄISCHE NORM
ICS 33.180.30
English version
Calibration of optical spectrum analyzers
(IEC 62129:2006)
Etalonnage des analyseurs  Kalibrierung von optischen
de spectre optique Spektrumanalysatoren
(CEI 62129:2006) (IEC 62129:2006)

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 62129:2006 E
Foreword
The text of document 86/245/FDIS, future edition 1 of IEC 62129, prepared by IEC TC 86, Fibre optics,
was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 62129 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
This European Standard makes reference to International Standards. Where the International Standard
referred to has been endorsed as a European Standard or a home-grown European Standard exists, this
European Standard shall be applied instead. Pertinent information can be found on the CENELEC web
site.
__________
Endorsement notice
The text of the International Standard IEC 62129:2006 was approved by CENELEC as a European
Standard without any modification.
__________
NORME CEI
INTERNATIONALE
IEC
INTERNATIONAL
Première édition
STANDARD
First edition
2006-01
Etalonnage des analyseurs de spectre optique
Calibration of optical spectrum analyzers

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62129  IEC:2006 – 3 –
CONTENTS
FOREWORD.7

1 Scope.11
2 Normative references.11
3 Terms and definitions .13
4 Calibration test requirements .21
4.1 Preparation.21
4.2 Reference test conditions .21
4.3 Traceability.21
5 Resolution bandwidth (spectral resolution) test.23
5.1 Overview .23
5.2 Resolution bandwidth (spectral resolution) test.23
6 Displayed power level calibration .27
6.1 Overview .27
6.2 Displayed power level (DPL) calibration under reference conditions.29
6.3 Displayed power level (DPL) calibration for operating conditions .33
6.4 Calculation of expanded uncertainty in displayed power level .43
7 Wavelength calibration.45
7.1 Overview .45
7.2 Wavelength calibration under reference conditions.47
7.3 Wavelength calibration for operating conditions.49
7.4 Calculation of expanded uncertainty in wavelength.53
8 Documentation .55
8.1 Measurement data and uncertainty .55
8.2 Measurement conditions .55

Annex A (normative) Mathematical basis for calculation of calibration uncertainty .57
Annex B (informative) Examples of calculation of calibration uncertainty.65
Annex C (informative) Using the calibration results .81
Annex D (informative) Wavelength references .91
Annex E (informative) Further reading and references for calibration of wavelength scale . 101

Figure 1 – Setup using a gas laser whose wavelength is known .23
Figure 2 – Setup using a broadband source with a transmission device.23
Figure 3 – Setup using an LD with an unknown wavelength.25
Figure 4 – Setup for calibration of displayed power level under reference conditions .29
Figure 5 – Test configuration for determining the wavelength dependence of displayed
power level uncertainty.33

62129  IEC:2006 – 5 –
Figure 6 – Test configuration for determining the polarization dependence of displayed

power level uncertainty.37
Figure 7 – Configuration for testing linearity error of displayed power level uncertainty.39
Figure 8 – Test configuration for determining the temperature dependence of displayed
power level uncertainty.41
Figure 9 – Test configuration for determining the temperature dependence of
wavelength uncertainty.53
Figure A.1 – Deviation and uncertainty type B, and how to replace both with an
appropriately larger uncertainty .59
95 % confidence intervals shown.89
Figure C.1 – Calibration of OSA wavelength scale using krypton emission lines .89
Figure D.1 – Absorption of LED light by acetylene ( C H ) .95
2 2
13 14
Figure D.2 – Absorption of LED light by hydrogen cyanide (H C N).97

Table 1 – Recommended light sources .25
Table C.1 – OSA calibration results .87
Table C.2 – Summary of OSA calibration parameters .89
Table D.1 – Vacuum wavelengths (nm) of selected gas laser lines.91
Table D.2 – Vacuum wavelengths (nm) of noble gas reference lines .91
Table D.3 – Vacuum wavelengths (nm) for the ν +ν band of acetylene C H
1 3 2 2
absorption lines [11].93
Table D.4 – Vacuum wavelengths (nm) for the ν +ν band of acetylene C H
1 3 2 2
absorption lines [11].95
13 14
Table D.5 – Vacuum wavelengths (nm) of selected hydrogen cyanide (H C N)
absorption lines [12].97

62129  IEC:2006 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CALIBRATION OF OPTICAL SPECTRUM ANALYZERS

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.
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 has been prepared by IEC technical committee 86: Fibre
optics.
IEC 62129 cancels and replaces IEC/PAS 62129, published in 2004, and constitutes a
technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
86/245/FDIS 86/250/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.

62129  IEC:2006 – 9 –
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.
62129  IEC:2006 – 11 –
CALIBRATION OF OPTICAL SPECTRUM ANALYZERS

1 Scope
This International Standard provides procedures for calibrating an optical spectrum analyzer
designed to measure the power distribution of an optical spectrum. This analyzer is equipped
with an input port for use with a fibre-optic connector.
An optical spectrum analyzer is equipped with the following minimum features:
a) the ability to present a display of an optical spectrum with respect to absolute wavelength;
b) a marker/cursor that displays the optical power and wavelength at a point on the spectrum
display.
NOTE This standard applies to optical spectrum analyzers developed for use in fibre-optic communications, and is
limited to equipment that can directly measure the optical spectrum output from an optical fibre, where the optical
fibre is connected to an input port installed in the optical spectrum analyzer through a fibre-optic connector.
In addition, an optical spectrum analyzer can measure the spectral power distribution with
respect to the absolute wavelength of the tested light and display the results of such measure-
ments. It will not include an optical wavelength meter that measures only centre wavelengths, a
Fabry-Perot interferometer or a monochromator that has no display unit.
The procedures outlined in this standard are considered to be mainly performed by users of
optical spectrum analyzers. The document, therefore, does not include correction using the
calibration results in the main body. The correction procedures are described in Annex C.
Of course, this standard will be useful in calibration laboratories and for manufacturers of
optical spectrum analyzers.
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 60050-731, International Electrotechnical Vocabulary (IEV) – Chapter 731: Optical fibre
communication
IEC 60359, Electrical and electronic measurement equipment – Expression of performance
IEC 60793-1 (all parts), Optical fibres – Part 1: Measurement methods and test procedures
IEC 60825-1, Safety of laser products – Part 1: Equipment classification, requirements and
user's guide
IEC 60825-2, Safety of laser products – Part 2: Safety of optical fibre communication systems
IEC 61290-3-1, Optical amplifiers – Test methods – Part 3-1: Noise figure parameters – Optical
spectrum analyzer method
62129  IEC:2006 – 13 –
BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, and OIML:1993, International vocabulary of basic terms
in metrology (VIM)
BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, and OIML, Guide to the expression of uncertainty in
measurement (GUM)
3 Terms and definitions
For the purposes of this document, the terms and definitions contained in IEC 60050-731 and
the following terms and definitions apply.
3.1
calibration
set of operations which establishes, under specified conditions, the relationship between the
values indicated by the measuring instrument and the corresponding known values of that
quantity (see also VIM, definition 6.11)
3.2
calibration under reference conditions
calibration which includes the evaluation of the test analyzer uncertainty under reference
conditions (3.17)
3.3
calibration for operating conditions
the calibration for operating conditions of an optical spectrum analyzer (3.16) including the
evaluation of the test analyzer operational uncertainty
3.4
centre wavelength
λ
centre
the power-weighted mean wavelength of a light source in a vacuum, in nanometers (nm)
For a continuous spectrum the centre wavelength is defined as:
∫
λcentre = (1 / Ptotal ) ρ(λ) λ dλ (1)
For a spectrum consisting of discrete lines, the centre wavelength is defined as:
λ = Pλ / P (2)
centre ∑ i i ∑ i
ii
where
ρ(λ) is the power spectral density of the source, for example in W/nm;
th
λ is the i discrete wavelength;
i
P is the power at λ , for example, in watts;
i i
P is ΣP = total power, for example, in watts.
total i
NOTE The above integrals and summations theoretically extend over the entire spectrum of the light source.
3.5
confidence level
an estimation of the probability that the true value of a measured parameter lies in the given
range (see expanded uncertainty (3.11))

62129  IEC:2006 – 15 –
3.6
coverage factor
k
the coverage factor, k, is used to calculate the expanded uncertainty (3.11) U from the
standard uncertainty (3.21), σ (see 3.11)
3.7
displayed power level
DPL
the power level indicated by an optical spectrum analyzer (3.16) undergoing calibration (3.1)
at a specified wavelength resolution setting
NOTE With an optical spectrum analyzer, the power level for a set resolution is measured and displayed.
3.8
displayed power level deviation
∆P
the difference between the displayed power level measured by the test analyzer, P , and the
OSA
corresponding reference power, P , divided by the reference power
ref
∆P = (P – P ) / P = P / P –1 (3)
OSA ref ref OSA ref
3.9
displayed power level uncertainty
σ
∆P
the standard uncertainty (3.21) of the displayed power level deviation
σ = σ(P / P – 1) (4)
∆P OSA ref
NOTE In the above formula, σ is to be understood as the standard uncertainty (3.21).
3.10
displayed wavelength range
the complete wavelength range shown in an optical spectrum analyzer (3.16) display for a
particular instrument state (3.12)
3.11
expanded uncertainty
U
confidence interval
the expanded uncertainty, U, is the range of values within which the measurement parameter,
at the stated confidence level (3.5), can be expected to lie. It is equal to the coverage factor
(3.6), k, times the combined standard uncertainty (3.21) σ:
U = k σ (5)
NOTE When the distribution of uncertainties is assumed to be normal and a large number of measurements are
made, then confidence levels (3.5) of 68,3 %, 95,5 % and 99,7 % correspond to k values of 1, 2 and 3 respectively.
The measurement uncertainty of an optical spectrum analyzer (3.16) should be specified in
the form of expanded uncertainty, U.
3.12
instrument state
a complete description of the measurement conditions and state of an optical spectrum
analyzer (3.16) during the calibration process
NOTE Typical parameters of the instrument state are the displayed wavelength range (3.10) in use, the
resolution bandwidth (spectral resolution) (3.18), the display mode (watt or dBm), warm-up time and other
instrument settings.
62129  IEC:2006 – 17 –
3.13
measurement result
the displayed or electrical output of any optical spectrum analyzer (3.16) in wavelength, in
units of nm or µm, and in power level, in units of mW or dBm, after completing all operations
suggested by the operating instructions, for example warm-up
3.14
measurement wavelength range
the wavelength range of injected light over which an optical spectrum analyzer (3.16)
performance is specified
3.15
operating conditions
all conditions of the measured and influential qualities, and other important requirements which
the expanded uncertainty (3.11) of an optical spectrum analyzer (3.16) is intended to be
met
[VIM, definition 5.5 modified]
3.16
optical spectrum analyzer
OSA
an optical instrument for measuring the power distribution of a spectrum with respect to
wavelength (frequency)
NOTE An OSA is equipped with an input port for use with a fibre-optic connector, and the spectrum is obtained
from light injected into the input port; the instrument also includes a screen-display function.
3.17
reference conditions
an appropriate set of influencing parameters, their nominal values and their tolerance bands,
with respect to which the uncertainty at reference conditions is specified
[IEC 60359, definition 3.3.10 modified]
NOTE Each tolerance band includes both the possible uncertainty of the condition and the uncertainty in
measuring the condition.
The reference conditions normally include the following parameters and, if necessary, their tolerance bands:
reference date, reference temperature, reference humidity, reference atmospheric pressure, reference light source,
reference displayed power level (3.7), reference fibre, reference connector-adapter combination, reference
wavelength, reference (spectral) bandwidth and resolution bandwidth (spectral resolution) (3.18) set.
3.18
resolution bandwidth
R
spectral resolution
full width at half maximum (FWHM) of the displayed spectrum obtained by the test analyzer
when using a source whose spectral bandwidth (3.20) is sufficiently narrow, that is, very
much less than the resolution bandwidth being measured
3.19
side-mode suppression ratio
SMSR
the peak power ratio between the main mode spectrum and the largest side mode spectrum in
a single-mode laser diode such as a DFB-LD
NOTE The side-mode suppression ratio is usually described in dB.

62129  IEC:2006 – 19 –
3.20
spectral bandwidth
B
for the purpose of this standard, the FWHM of the spectral width of the source
If the source exhibits a continuous spectrum, then the spectral bandwidth, B, is the FWHM of
the spectrum.
If the source is a laser diode with a multiple-longitudinal mode spectrum, then the FWHM
spectral bandwidth B is the RMS spectral bandwidth, multiplied by 2,35 (assuming the source
has a Gaussian envelope):
  1/2
(6)
B = 2,35 [{(1 / P ) ×  Pλ  } – λ ]
total ∑ i i centre
 
 i 
where
λ is the centre wavelength (3.4) of laser diode, in nm;
centre
P is ∑P = total power, in watts;
total i
th
P
is the power of i longitudinal mode, in watts;
i
th
λ is the wavelength of i longitudinal mode, in nm.
i
3.21
standard uncertainty
σ
uncertainty of a measurement result expressed as a standard deviation
NOTE For further information, see Annex A and the ISO/IEC Guide to the Expression of Uncertainty in
Measurement (ISO/IEC GUIDE EXPRES).
3.22
uncertainty type A
type of uncertainty obtained by a statistical analysis of a series of observations, such as when
evaluating certain random effects of measurement (see ISO/IEC GUIDE EXPRES)
3.23
uncertainty type B
type of uncertainty obtained by means other than a statistical analysis of observations, for
example an estimation of probable sources of uncertainty, such as when evaluating systematic
effects of measurement (see ISO/IEC GUIDE EXPRES)
NOTE Other means may include previous measurement data, experience with or general knowledge of the
behaviour and properties of relevant materials, instruments, manufacturers’ specifications, data provided in
calibration and other certificates, and uncertainties assigned to reference data taken from handbooks.
3.24
wavelength deviation
∆λ
the difference between the centre wavelength (3.4) measured by the test analyzer, λ , and
OSA
the reference wavelength, λ , in nm or µm
ref
∆λ = λ – λ (7)
OSA ref
3.25
wavelength uncertainty
σ
∆λ
the standard uncertainty (3.21) of the wavelength deviation (3.24), in nm or µm

62129  IEC:2006 – 21 –
4 Calibration test requirements
4.1 Preparation
The following recommendations apply.
Calibrations should be carried out in facilities that are separate from other functions of the
organization. This separation should include laboratory accommodation and measurement
equipment.
The calibration laboratory should operate a quality control system appropriate to the range of
measurement it performs (for example ISO 9000), when the calibration is performed in
calibration laboratories. There should be independent scrutiny of the measurement results,
intermediary calculations and preparation of calibration certificates.
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).
Perform all tests at an ambient room temperature of (23 ± 3) °C with a relative humidity of
(50 ± 20) % unless otherwise specified. Give the test equipment a minimum of 2 h prior to
testing to reach equilibrium with its environment. Allow the optical spectrum analyzer a warm-
up period in accordance with the manufacturer’s instructions.
4.2 Reference test conditions
The reference test conditions usually include the following parameters and, if necessary, their
tolerance bands: date, temperature, relative humidity, displayed power level, wavelength, light
source, fibre, connector-adapter combination, (spectral) bandwidth and resolution bandwidth
(spectral resolution) set. Unless otherwise specified, use a single-mode optical fibre input
pigtail as prescribed by the IEC 60793-1 series, having a length of at least 2 m.
Operate the optical spectrum analyzer 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 analyzer under test. Choose these
parameters so as to optimize the analyzer’s accuracy and resolution capabilities, as specified
by the manufacturer’s operating procedures.
Document the conditions as specified in Clause 8.
The calibration results only apply to the set of test conditions used in the calibration process.
Because of the potential for hazardous radiation, be sure to establish and maintain conditions
of laser safety. Refer to IEC 60825-1 and IEC 60825-2.
4.3 Traceability
Make sure that any test equipment which has a significant influence on the calibration results is
calibrated in an unbroken chain to the appropriate national standard or natural physical
constant. Upon request, specify this test equipment and its calibration chain(s). The re-
calibration period(s) shall be defined and documented.

62129  IEC:2006 – 23 –
5 Resolution bandwidth (spectral resolution) test
5.1 Overview
The resolution bandwidth (spectral resolution) of the test analyzer should be tested prior to
displayed power level and wavelength calibration because the resolution bandwidth influences
their calibration. This test is performed under reference calibration conditions. Wavelength is
shown in a vacuum. Calibration of optical bandwidth is described in IEC 61290-3-1.
NOTE The result of the resolution bandwidth (spectral resolution) test described here should be employed as the
optical bandwidth (in wavelength units) for the measurement of optical-amplifier noise-figure.
5.2 Resolution bandwidth (spectral resolution) test
Alternative setups for the resolution bandwidth are shown in Figures 1, 2, and 3. In the Figure 1
setup, a gas laser whose wavelength is known is used as the light source. Figure 2 shows a
setup in which a broadband source is used in conjunction with a transmission device with
known (traceable) wavelengths of peak (or null) transmission. Figure 3 shows a setup in which
a laser diode (LD) whose wavelength is unknown is used for the light source.

Optical fibre
Test
Light
analyzer
source
IEC  2591/05
a) For resolution bandwidth test,
b) for wavelength calibration under reference conditions, and
c) for determining the wavelength dependence of wavelength uncertainty.
Figure 1 – Setup using a gas laser whose wavelength is known

Optical fibre Transmission Optical fibre
Broadband
Test
source device
analyzer
IEC  2592/05
a) For resolution bandwidth test,
b) for wavelength calibration under reference conditions, and
c) for determining the wavelength dependence of wavelength uncertainty.
Figure 2 – Setup using a broadband source with a transmission device

62129  IEC:2006 – 25 –
Optical fibre
Light Test
source
analyzer
Wavelength
meter
IEC  2593/05
a) For resolution bandwidth test,
b) for wavelength calibration under reference conditions, and
c) for determining the wavelength dependence of wavelength uncertainty.
Figure 3 – Setup using an LD with an unknown wavelength
5.2.1 Equipment for resolution bandwidth (spectral resolution) test
a) Light source: use the light source prescribed for calibrating the test analyzer; if a light
source is not prescribed, use one with a spectral bandwidth and wavelength stability
sufficient for the minimum resolution bandwidth prescribed for the test analyzer.
Recommended light sources are lasers such as those listed in Table 1, a laser diode (LD)
or other laser (which may be tunable) having a spectral bandwidth much narrower than the
resolution bandwidth of the test analyzer. Also, a broadband source may be used in
conjunction with a transmission device with known (traceable) wavelengths of peak (or null)
transmission. The transmission device may be, for example, a series of fixed narrowband
filters, absorption lines in gaseous media, or Fabry-Perot interferometers. Annex D
tabulates many stable wavelength references. The reference used should have a
wavelength stability, spectral bandwidth and power stability sufficient for the resolution
bandwidth test.
Table 1 – Recommended light sources
Wavelength
Light source
(nm) [vac]
488,122
Ar laser
514,673
632,991
He-Ne laser
1 152,590
1 523,488
b) Wavelength meter: an instrument for measuring the wavelength of a light source. Its
precision must be sufficiently better than the precision required in the wavelength test. This
instrument is used when a laser diode (LD) with an unknown wavelength is used as the
light source.
c) Optical fibre: single-mode optical fibre as prescribed by the IEC 60793-1 series.

62129  IEC:2006 – 27 –
5.2.2 Test procedure for resolution bandwidth (spectral resolution)
Using the test setup shown in Figure 1, 2 or 3, set the wavelength measurement range of the
test analyzer so that it includes the wavelength of the light source.
a) Set the resolution bandwidth of the test analyzer to its specified value. Let the specified
value be R .
set
d) Measure the resolution of the displayed spectral bandwidth, i.e. the wavelength interval
3 dB below the peak value, as R . Repeat this measurement at least ten times and
OSAi
calculate the average resolution.
m
R = R / m (8)
OSAi
OSA ∑
i =1
where m is the number of measurements.
e) Calculate the difference ratio of the OSA value from the resolution bandwidth setting using
Equation (9).
∆r = R / R – 1 (9)
diff OSA set
f) If necessary, repeat this procedure with different resolution bandwidth settings.
NOTE 1 When the test analyzer has a wavelength span linearity error, it is necessary to tune the light source
slightly around the wavelength of interest, while making multiple measurements of the displayed 3 dB bandwidth to
obtain an accurate measurement of the true resolution bandwidth at a given wavelength. The required tuning range
is of the order of ±1 nm, so this measurement can be made with a temperature-tuned DFB laser, an external cavity
laser or a tunable fibre laser. By averaging the resolution bandwidth readings, a more accurate measurement of the
true resolution bandwidth can be obtained.
NOTE 2 If the resolution bandwidth must be corrected based on the calibration results, this is typically
implemented by making software corrections to the instrument, mathematical corrections to the results, or
instrument hardware adjustments. Once the adjustments have been made, it is advisable to repeat the test to verify
that the correction has operated correctly. See Annex C.
6 Displayed power level calibration
6.1 Overview
The factors making up uncertainty in the displayed power level of the test analyzer consist of
a) the intrinsic uncertainty of the test analyzer as found in the test under reference conditions,
and
b) partial uncertainties due to wavelength dependence, polarization dependence, linearity and
temperature dependence as found in tests under operating conditions.
If the test analyzer is used beyond the reference conditions, it is necessary to obtain the partial
uncertainties.
The intrinsic uncertainty under the reference conditions is obtained by the calibration procedure
described in 6.2. The partial uncertainties are obtained by the calibration procedure described
in 6.3.1 to 6.3.4 in compliance with the individual factor, i.e. wavelength, polarization, linearity
and temperature. When the test analyzer is only used under reference conditions, the
calibration procedures described in 6.3 are not essential, that is, they are not mandatory.
NOTE 1 Since the unit generally used for measurement values, dBm, is not appropriate for uncertainty
accumulation, linear units (mW, µW) are used. Results of such accumulations can be converted back to dB to
express overall uncertainty when needed.
NOTE 2 A power meter or a reference power meter will be needed to check the light source power each time a
new source wavelength is used.
NOTE 3 The state of polarization should not be changed during calibration except controlling by an optional
polarization controller.
62129  IEC:2006 – 29 –
6.2 Displayed power level (DPL) calibration under reference conditions
Figure 4 shows the test configuration for determining the uncertainty in the displayed power
level (DPL). This test is performed under reference calibration conditions.
NOTE The light source used for the displayed power level calibration should be depolarized, or else a polarization
controller should be used. This will calibrate the test analyzer at the mid-point of its variation due to polarization

Optical Optical Optical
Light fibre Variable fibre fibre Test
Polarization
source attenuator analyzer
controller
(Optional)
Reference
power
meter
IEC  2594/05
Figure 4 – Setup for calibration of displayed power level under reference conditions
6.2.1 Equipment for DPL calibration under reference conditions
a) Light source: use a light source which can emit stable optical-fibre light with an output
from 0,1 mW (–10 dBm) to 1 mW (0 dBm), and which offers good suppression of side-
modes and optical noise (>40 dB, when measured with a resolution bandwidth which is the
same as that of the test analyzer) outside its spectral bandwidth. The source spectral
bandwidth should be in turn sufficiently narrower than the resolution prescribed for the test
analyzer. The light sources shown in Table 1, a laser diode (LD) (SMSR > 40 dB: see 3.19)
or a fibre laser (also with SMSR > 40 dB) are recommended.
NOTE The wavelength of the light source should be measured in advance by using a wavelength meter if a
laser diode (LD) or a fibre laser is used.
b) Variable attenuator: use a variable attenuator that can be adjusted over the optical power
range used in the test.
c) Reference optical power meter: either of the following operated under reference
calibration conditions:
1) an optical power meter calibrated by an official institution that performs calibration
services with a stated uncertainty; or
2) an optical power meter calibrated according to standards specified by such an official
institution with a stated uncertainty.
Namely the uncertainty of the reference power meter, σ , is already known and is
PPM
described in its certification.
d) Optional polarization controller: a polarization controller is used which controls the state
of polarization of incident light to obtain an optical fibre output with an extinction ratio of
20 dB or more. The level variation when the state of polarization is changed should be far
smaller than the polarization dependence of the test analyzer. Some polarization controllers
are combinations of a polarizer, a 1/2-wavelength plate and a 1/4-wavelength plate; some
rotate two fibre loops.
62129  IEC:2006 – 31 –
6.2.2 Test procedure for DPL calibration under reference conditions
Using the test configuration shown in Figure 5, set the resolution of the test analyzer
sufficiently larger than the spectral bandwidth of the light source. Adjust the variable attenuator
so that the power level of the outgoing light to the test analyzer is optimized. If the wavelength
of the light source is not already known, it should be measured by using a wavelength meter.
The measurement sequence is as follows.
a) Measure the value of the outgoing optical-fibre light as P using a reference optical
REF,i
power meter. If a polarization controller is used, measure multiple times at different states
of polarization and average these values.
b) After this, connect the outgoing optical-fibre light to the test analyzer and read the peak
power level measured by the test analyzer as P use a linear scale (in units of mW or
OSAi;
µW) to read the value. If a polarization controller is used, measure multiple times at
different states of polarization and average these values.
c) Calculate the difference ratio of the OSA value from the power meter measurement using
Equation (10).
∆P = P / P – 1 (10)
diff,i OSAi REF,i
d) Repeat this measurement at least ten times.
6.2.3 Calculation of DPL uncertainty under reference conditions
Calculate the mean and standard deviation of the difference ratio using the following equations.
m
∆P = ( /ΔP ) m (11)
diff ∑ diff,i
i =1
m
2 1/2
σ = (ΔP −∆P ) / (m – 1 ) (12)
[ ]
∆Pdiff ∑ diff,i diff
i =1
where m is the number of measurements used.
The uncertainty σ with respect to the displayed power level for the test analyzer operated
∆Pref
under reference calibration conditions is given by Equation (13).
2 2 1/2
σ = (σ + σ ) (13)
∆Pref PPM ∆Pdiff
where
σ is the uncertainty of the reference optical power meter described in its certification;
PPM
σ is the standard deviation of the values measured during the test.
∆Pdiff
The displayed power level deviation ∆P is given by Equation (14), which is the same as the
ref
mean value of the difference ratio.
∆P = ∆P (14)
ref diff
62129  IEC:2006 – 33 –
6.3 Displayed power level (DPL) calibration for operating conditions
The calibration described in this chapter is not mandatory. Perform the calibration procedure
when the test analyzer is used beyond the reference calibrations.
Individual factors in the displayed power level uncertainty for the operating conditions may
consist of the following:
1) wavelength dependence;
2) polarization dependence;
3) linearity; and
4) temperature dependence.
6.3.1 Wavelength dependence
Figure 5 shows the test configuration for determining wavelength dependence. This test is
performed under reference calibration conditions except for the wavelength.

Optical
Variable-
Optical fibre
Polarization
fibre Test
wavelenght
controller analyzer
light source
(Optional)
Optical
power
meter
Wavelength
meter
IEC  2595/05
Figure 5 – Test configuration for determining the wavelength dependence
of displayed power level uncertainty
6.3.1.1 Equipment for determining DPL wavelength dependence
a) Light source: use a variable-wavelength light source such as a tunable laser. It should
supply the needed amount of light power stably within the test wavelength range of the test
analyzer, and its spectral bandwidth should be far narrower than the specified resolution
bandwidth of the test analyzer.
b) Wavelength meter: use to measure the wavelength of the variable-wavelength light source.
It is unnecessary if the light source has been calibrated.
c) Optical power meter: use a non-wavelength-dependent optical power meter, or one whose
wavelength dependence has been calibrated.

62129  IEC:2006 – 35 –
d) Optional polarization controller: a polarization controller is used which controls the state
of polarization of incident light to obtain an optical fibre output with an extinction ratio of
20 dB or more. The level variation when the state of polarization is changed should be far
smaller than the polarization dependence of the test analyzer. Some polarization controllers
are combinations of a polarizer, a 1/2-wavelength plate and a 1/4-wavelength plate; some
rotate two fibre loops.
6.3.1.2 Test procedure for determining DPL wavelength dependence
Use the test configuration shown in Figure 5.
The test procedure is as follows.
a) After the environmental temperature is completely stabilized, input light from the light
source to the wavelength meter for wavelength measurement. The reading provided by the
wavelen
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