IEC 61300-3-29:2014

• Abstract:

  IEC 61300-3-29:2014 identifies two basic measurement methods for characterizing the spectral transfer functions of DWDM devices. The transfer functions are the functions of transmittance dependent of wavelengths. In this standard, optical attenuations are also used. The transfer functions can be used to produce measurements of insertion loss (IL), polarization dependent loss (PDL), isolation, centre wavelength, bandwidth (BW) and other optical performances. This second edition cancels and replaces the first edition published in 2005. It constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:; - terms and definitions have been added and reconsidered in order to be harmonized with IEC 62074-1;; - characterizations of the device under test have been reviewed;; - details to be specified have been reconsidered. Keywords: spectral transfer functions of DWDM devices, measurements of insertion loss (IL), polarization dependent loss (PDL), isolation, centre wavelength, bandwidth (BW)

• Status: Published
• Publication Date: 18-Mar-2014
• ICS: 33.180.20 - Fibre optic interconnecting devices
• Technical Committee: SC 86B - Fibre optic interconnecting devices and passive components
• Drafting Committee: WG 4 - TC 86/SC 86B/WG 4
• Current Stage: PPUB - Publication issued
• Start Date: 19-Mar-2014
• Completion Date: 15-Apr-2014

• Revises: IEC 61300-3-29:2005 - Fibre optic interconnecting devices and passive components - Basic test and measurement procedures - Part 3-29: Examinations and measurements - Measurement techniques for characterizing the amplitude of the spectral transfer function of DWDM components
• Effective Date: 05-Sep-2023

Overview

IEC 61300-3-29:2014 is an international standard developed by the International Electrotechnical Commission (IEC) that specifies methods for examining and measuring the spectral transfer characteristics of Dense Wavelength Division Multiplexing (DWDM) fibre optic devices. This second edition updates and replaces the 2005 version, introducing harmonized terms and enhanced test procedures to better characterize DWDM components, a crucial technology in modern optical communication networks.

The standard focuses on defining two primary measurement methods for characterizing spectral transfer functions-functions that describe the transmittance of devices as a function of wavelength. Through these measurements, it provides detailed optical performance parameters including insertion loss (IL), polarization dependent loss (PDL), isolation, centre wavelength, and bandwidth (BW).

Key Topics

• Spectral Transfer Functions
  Characterization of DWDM devices by analyzing transmittance vs. wavelength and deriving optical attenuation.

• Measurement Methods

  • Method A: Using a tuneable narrowband light source (TNLS)
  • Method B: Using a broadband light source (BBS)
    Both methods incorporate wavelength tracking filters, reference branching devices, polarizers, polarization controllers, and appropriate detectors for accurate measurement.

• Optical Performance Metrics

  • Insertion Loss (IL): Quantifies loss due to device insertion.
  • Polarization Dependent Loss (PDL): Measures signal loss variation with polarization changes.
  • Isolation and Crosstalk: Important for channel separation in DWDM systems.
  • Centre Wavelength and Bandwidth (BW): Defines the operational spectral range for channels.
  • Passband Ripple: Variation in transmitted power across the passband.
  • Out-of-band Attenuation: Signal suppression outside the operational bandwidth.

• Device Under Test (DUT) Characterization
  Includes considerations for input/output optics, spectral transmission/reflection properties, and polarization effects.

• Measurement Apparatus and Setup
  Detailed descriptions of apparatus components such as tuneable light sources, detectors, wavelength meters, and temporary joints ensure repeatable and standardized testing environments.

• Technical Harmonization
  Updated terms and definitions align with IEC 62074-1 to maintain consistency across optical component standards.

Applications

IEC 61300-3-29:2014 is pivotal for manufacturers, test laboratories, and network operators involved with DWDM devices and fibre optic components. It serves to:

• Ensure Quality Assurance
  By providing standardized test methodologies, the standard enables consistent quality verification of DWDM devices such as filters, multiplexers, demultiplexers, and optical add-drop multiplexers (OADMs).

• Optimize Network Performance
  Accurate measurement of spectral characteristics including insertion loss and polarization dependent loss optimizes the configuration and performance of high-capacity DWDM optical networks.

• Facilitate Device Certification and Compliance
  Compliance with IEC 61300-3-29 ensures that devices meet internationally accepted criteria, facilitating interoperability and market acceptance.

• Support Product Development and R&D
  Enables detailed characterization during the design and development of advanced DWDM components to meet evolving network requirements.

Related Standards

• IEC 61300 Series
  The broader family details basic test and measurement procedures for fibre optic interconnecting devices and passive components.

• IEC 62074-1
  Covers terminology and definitions relevant to DWDM devices, harmonized with the terms used in IEC 61300-3-29 to ensure standard coherence.

• IEC 60793 and IEC 60794 Series
  Standards for optical fibre and cables complement the testing of DWDM devices by addressing the physical transmission media.

• ITU-T G.694.1
  Specifies DWDM grid parameters, which interface closely with spectral transfer characteristics measured under IEC 61300-3-29.

---

By adhering to IEC 61300-3-29:2014, stakeholders ensure precise, reliable measurement of DWDM device spectral characteristics, facilitating robust, efficient, and scalable optical communication infrastructures. This standard represents an essential tool for maintaining high performance and interoperability in modern fibre optic networks.

IEC 61300-3-29 ®
Edition 2.0 2014-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures –
Part 3-29: Examinations and measurements – Spectral transfer characteristics of
DWDM devices
Dispositifs d’interconnexion et composants passifs à fibres optiques –
Procédures fondamentales d’essais et de mesures –
Partie 3-29: Examens et mesures – Caractéristiques de transfert spectral des
dispositifs DWDM
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IEC 61300-3-29 ®
Edition 2.0 2014-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Fibre optic interconnecting devices and passive components – Basic test and

measurement procedures –
Part 3-29: Examinations and measurements – Spectral transfer characteristics

of DWDM devices
Dispositifs d’interconnexion et composants passifs à fibres optiques –

Procédures fondamentales d’essais et de mesures –

Partie 3-29: Examens et mesures – Caractéristiques de transfert spectral des

dispositifs DWDM
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX W
ICS 33.180.20 ISBN 978-2-8322-1479-4

– 2 – IEC 61300-3-29:2014 © IEC 2014
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms, definitions, abbreviations and symbols . 7
3.1 Terms and definitions . 7
3.2 Symbols and abbreviations . 8
3.2.1 Symbols . 8
3.2.2 Abbreviations . 8
4 General description . 9
5 Apparatus . 10
5.1 Measurement set-up . 10
5.2 Light source, S . 12
5.2.1 Tuneable narrowband light source (TNLS) – Method A . 12
5.2.2 Broadband source (BBS) – Method B . 12
5.3 Tracking filter (TF) . 12
5.4 Reference branching device (RBD) . 12
5.5 Wavelength meter (WM) . 13
5.6 Polarizer (PL). 13
5.7 Polarization controller (PC) . 13
5.8 Device under test (DUT) . 13
5.8.1 General . 13
5.8.2 Device input/output optics . 14
5.9 Detector (D) . 14
5.9.1 Broadband detectors, BBD1, BBD2, Method A.1 . 14
5.9.2 Tuneable narrowband detector (TND) – Method A.2 and
Method B . 14
5.10 Temporary joints (TJ) . 15
6 Procedure . 15
6.1 General . 15
6.2 Preparation of DUTs . 15
6.3 System initialization . 15
6.4 System reference measurement . 16
6.4.1 General . 16
6.4.2 Measurement of the reference spectra for Method A . 16
6.4.3 Measurement of reference spectra for Method B . 16
6.5 Measurement of device spectra . 16
7 Characterization of the device under test . 17
7.1 Determination of transfer functions . 17
7.1.1 General . 17
7.1.2 Accounting for the source variations . 17
7.1.3 Calculations for the Mueller matrix method . 17
7.2 Transmission (T(λ)) spectra measurements . 18
7.2.1 General . 18
7.2.2 Peak power calculation . 19

7.2.3 Normalization of the transfer function . 20
7.3 Calculation of optical attenuation (A) . 20
7.4 Insertion loss (IL) . 20
7.5 Bandwidth and full spectral width . 21
7.5.1 General . 21
7.5.2 Centre wavelength . 21
7.5.3 Centre wavelength deviation . 22
7.5.4 X dB bandwidth . 22
7.6 Passband ripple . 22
7.7 Isolation (I) and crosstalk (XT) . 23
7.7.1 General . 23
7.7.2 Channel isolation . 24
7.7.3 Channel crosstalk . 24
7.7.4 Adjacent channel isolation . 24
7.7.5 Adjacent channel crosstalk . 25
7.7.6 Minimum adjacent channel isolation . 25
7.7.7 Maximum adjacent channel crosstalk . 25
7.7.8 Non-adjacent channel isolation . 25
7.7.9 Non-adjacent channel crosstalk . 26
7.7.10 Minimum non-adjacent channel isolation . 26
7.7.11 Maximum non-adjacent channel crosstalk . 26
7.7.12 Total channel isolation . 26
7.7.13 Total channel crosstalk . 26
7.7.14 Minimum total channel isolation . 26
7.7.15 Maximum total channel crosstalk . 26
7.8 Polarization dependent loss (PDL(λ)) . 27
7.9 Polarization dependent centre wavelength (PDCW) . 27
7.10 Channel non-uniformity . 28
7.11 Out-of-band attenuation . 28
8 Details to be specified . 28
8.1 Light source (S) . 28
8.1.1 Tuneable narrowband light source (TNLS) . 28
8.1.2 Broadband source (BBS) (unpolarized) . 28
8.2 Polarization controller (PC) . 29
8.3 Polarizer (PL). 29
8.4 Tracking filter (TF) . 29
8.5 Reference branching device (RBD) . 29
8.6 Temporary joint (TJ) . 29
8.7 Wavelength meter (WM) . 29
8.8 Detector (D) . 29
8.8.1 Broadband detector (BBD) . 29
8.8.2 Tuneable narrowband detector (TNBD) . 29
8.9 DUT . 30
Annex A (informative) Reflection spectrum measurements . 31
A.1 General . 31
A.2 Apparatus . 31
A.2.1 General . 31
A.2.2 Reference branching device . 31

– 4 – IEC 61300-3-29:2014 © IEC 2014
A.2.3 Optical termination . 32
A.3 Measurement procedure . 32
A.3.1 General . 32
A.3.2 Determination of source reference spectrum . 32
A.3.3 Determination of system constant . 32
A.3.4 Determination of reference reflectance spectrum . 33
A.3.5 Determination of device reflectance spectrum . 33
A.3.6 Determination of optical attenuation . 33
A.4 Reflection [R(λ)] spectra measurements . 34
Annex B (informative) Determination of the wavelength increment parameter . 35
Annex C (informative) Determination of a mean value using the shorth function . 37
Bibliography . 39

Figure 1 – Basic measurement set-up . 10
Figure 2 – Measurement set-up for tuneable narrowband light source (TNLS) system . 11
Figure 3 – Measurement set-up for TNLS and tuneable narrowband detector (TND)
system . 11
Figure 4 – Measurement set-up for BBS and tuneable narrowband detector (TND)
system . 11
Figure 5 – System reference for transmission measurement . 16
Figure 6 – Normalized transfer functions . 19
Figure 7 – BW and full spectral width for a fibre Bragg grating . 21
Figure 8 – X dB bandwidth . 22
Figure 9 – Passband ripple . 23
Figure 10 – Channel isolation and crosstalk . 24
Figure 11 – Minimum adjacent channel isolation . 25
Figure 12 – Polarization dependence of the transfer function . 27
Figure 13 – Polarization dependent centre wavelength (PDCW) . 28
Figure A.1 – Measurement set-up for a single port device . 31
Figure A.2 – Source reference set-up . 32
Figure A.3 – Set-up for measurement of system constant . 33
Figure C.1 – Example response and –x dB wavelengths . 37
Figure C.2 – Example showing the –0,5 dB wavelengths based on the shorth (dotted
vertical lines) and the mean (solid vertical lines) . 38

Table 1 – Test methods . 10

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTIC INTERCONNECTING
DEVICES AND PASSIVE COMPONENTS –
BASIC TEST AND MEASUREMENT PROCEDURES –

Part 3-29: Examinations and measurements –
Spectral transfer characteristics of DWDM devices

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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International Standard IEC 61300-3-29 has been prepared by sub-committee 86B: Fibre optic
interconnecting devices and passive components, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition published in 2005. It constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
– terms and definitions have been added and reconsidered in order to be harmonized with
IEC 62074-1;
– characterizations of the device under test have been reviewed;

– 6 – IEC 61300-3-29:2014 © IEC 2014
– details to be specified have been reconsidered.
The text of this standard is based on the following documents:
FDIS Report on voting
86B/3718/FDIS 86B/3758/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.
The list of all parts of IEC 61300 series, published under the general title, Fibre optic
interconnecting devices and passive components – Basic test and measurement procedures,
can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability 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.
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.
FIBRE OPTIC INTERCONNECTING
DEVICES AND PASSIVE COMPONENTS –
BASIC TEST AND MEASUREMENT PROCEDURES –

Part 3-29: Examinations and measurements –
Spectral transfer characteristics of DWDM devices

1 Scope
This part of IEC 61300 identifies two basic measurement methods for characterizing the
spectral transfer functions of DWDM devices.
The transfer functions are the functions of transmittance dependent of wavelengths. In this
standard, optical attenuations are also used.
NOTE In this standard, transfer functions are expressed by T(λ) and optical attenuations are expressed by A(λ).
The transfer functions can be used to produce measurements of insertion loss (IL),
polarization dependent loss (PDL), isolation, centre wavelength, bandwidth (BW) and other
optical performances.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. 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 – Chapter 731: Optical fibre
communication
IEC 61300-3-2, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-2: Examinations and measurements – Polarization
dependent loss in a single-mode fibre optic device
IEC 61300-3-7, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-7: Examinations and measurements – Wavelength
dependence of attenuation and return loss of single mode components
IEC 62074-1, Fibre optic interconnecting devices and passive components – Fibre optic WDM
devices – Part 1: generic specification
3 Terms, definitions, abbreviations and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-731, as well
as the following, apply.
– 8 – IEC 61300-3-29:2014 © IEC 2014
3.1.1
bandwidth
(linewidth)
BW
spectral width of a signal or filter
Note 1 to entry: In the case of a laser signal such as a tuneable narrowband light source, the term 'linewidth' is
commonly preferred. Often defined by the width at a set power distance from the peak power level of the device
(i.e. 3 dB BW or 1 dB BW). The bandwidth shall be defined as the distance between the closest crossings on either
side of the centre wavelength in those cases where the spectral shape has more than 2 such points. The distance
between the outermost crossings can be considered the full spectral width.
3.1.2
channel frequency range
(passband)
CFR
specified range of wavelengths (frequencies) from λ (f ) to λ (f ), centred about
hmin hmin hmax hmax
the nominal operating wavelength frequency), within which a WDM device operates to
transmit less than or equal to the specified optical attenuation
Note 1 to entry: Passband is commonly used to convey the same meaning.
3.1.3
dense WDM
DWDM
WDM device intended to operate for channel spacing equal to or less than 1 000 GHz
3.1.4
polarization dependent loss
PDL
maximum variation of insertion loss due to a variation of the state of polarization (SOP) over
all SOP
3.1.5
state of polarization
SOP
distribution of light energy among the two linearly independent solutions of the wave
equations for the electric field
3.1.6
source spontaneous emission
SSE
broadband emissions from a laser cavity that bear no phase relation to the cavity field
Note 1 to entry: These emissions can be seen as the baseline noise on an optical spectrum analyser (OSA)
3.1.7
wavelengths division multiplexer
WDM
term frequently used as a synonym for a wavelength-selective branching device
3.2 Symbols and abbreviations
3.2.1 Symbols
δ wavelength sampling increment during the measurement
λ centre channel or nominal operating wavelength for a component
h
3.2.2 Abbreviations
APC angled physical contact
ASE amplified spontaneous emission

BBD broadband detector
BBS broadband light source
BW bandwidth
CFR channel frequency range
DOP  degree of polarization
DUT  device under test
DWDM dense wavelengths division multiplexer
FBG fibre Bragg grating
IL insertion loss
OPM optical power meter
OSA optical spectrum analyser
PC polarization controller
PC physical contact
PDCW polarization dependent centre wavelength
PDL polarization dependent loss
PSCS polarization state change system
PL polarizer
RBD reference branching devices
S light source
SD standard deviation
SOP state of polarization
SSE source spontaneous emission
TF tracking filter
TJ temporary joint
TLS tuneable laser source.
TND tuneable narrowband detector
TNLS tuneable narrowband light source
WDL wavelength dependent loss
WDM wavelength division multiplexer
WM wavelength meter
4 General description
This standard is complementary to the wavelength dependence of attenuation, and return loss
(IEC 61300-3-7), and polarization dependence of attenuation (IEC 61300-3-2) for DWDM
devices which channel spacing is less than or equal to 1 000 GHz (8 nm at the wavelength
band of 1 550 nm).
The transfer functions can be used to produce measurements of following performance
parameters:
– insertion loss (IL);
– centre wavelength and centre wavelength deviation;
– X dB bandwidth;
– passband ripple;
– isolation;
– 10 – IEC 61300-3-29:2014 © IEC 2014
– crosstalk;
– polarization dependent loss (PDL) and polarization dependent centre wavelength
(PDCW) ;
– channel non-uniformity;
– out-of-band attenuation.
In general, the DWDM devices have channel bandwidths less than 1 nm, filter response
slopes greater than 100 dB/nm, and out-of-band rejection extending over tens of nm.
The methods described in this standard will show how to obtain the transfer function from a
single input to a single output port (single conducting path). For an M x N device, it will be
required to repeat this procedure using all possible combinations of input and output ports.
The methods described in this standard are intended to be applicable to any wavelength band
(C, L, S, O, etc.) although examples may be shown in the C-band for illustrative purposes.
The two methods contained in this standard differ mainly in the way in which the wavelength
resolution is obtained. Method A uses a tuneable narrowband light source, while Method B
used a broadband light source. Method A has two branching methods; Method A.1 and
Method A.2. These three measurement methods are summarized in Table 1. Method A.2 shall
be considered the reference test method for DWDM devices.
Table 1 – Test methods
Method Names Source Detector Examples Remarks
A.1 TNLS in sweep TNLS in sweep mode BBD TNLS + DUT + OPM Alternative
mode + BBD
A.2 TNLS in sweep TNLS in sweep mode TND TNLS + DUT + OSA Reference
mode + TND
B BBS + TND BBS TND BBS + DUT + OSA Alternative

This standard also includes annexes that illustrate the following:
Annex A: Reflection spectrum measurements;
Annex B: Determination of wavelength increment parameter;
Annex C: Determination of a mean value using the shorth function.
5 Apparatus
5.1 Measurement set-up
The basic measurement set-up for the characterization of DWDM devices is shown in Figure 1
below.
TJ2
TJ1
S PL PC DUT D
IEC  0959/14
Figure 1 – Basic measurement set-up
This procedure contains three methods that differ fundamentally in the way in which the
wavelength resolution is achieved. There are three key influences on the wavelength

resolution: the linewidth of the source or bandwidth of the tuneable narrowband detector, the
analogue bandwidth of the detection system and the rate of change of wavelength.
Having determined the wavelength resolution of the measurement, the wavelength sampling
increment (δ) should be less than half the bandwidth of the system in order to accurately
measure the average value of the optical attenuation.
The bandwidth of the system is determined by the convolution of the effective source
bandwidth with the rate of change of wavelength over the time constant of the detector.
Practical constraints may result in smaller or larger bandwidths than recommended. Two
cautions should be noted with smaller bandwidths: first, coherent interference effects can lead
to additional measurement errors, and second, under-sampling of the device could lead to
misrepresentations of the reconstructed transfer function. If larger bandwidths are used, the
reconstructed transfer function could smear out fine structures and distort response slopes.
As the response slopes may exceed 100 dB/nm, small uncertainties in wavelength may result
in large amplitude response errors. In general, the resolution bandwidth of the system needs
to be chosen based on the device characteristics and noted in the details to be specified.
As explained in Table 1, there are three measurement methods. Figures 2, 3, and 4 show the
typical set-ups for Methods A.1, A.2 and B.
TJ2
TJ1 DUT
BBD1
PC RBD
TLS TF RBD
BBD2
WM
IEC  0960/14
Figure 2 – Measurement set-up for tuneable narrowband light source (TNLS) system

TJ2
TJ1
DUT
TNLS PC TND
IEC  0961/14
Figure 3 – Measurement set-up for TNLS and tuneable narrowband detector (TND)
system
TJ2
TJ1
BBS
DUT
PL PC TND
(unpolarized)
IEC  0962/14
Figure 4 – Measurement set-up for BBS and tuneable narrowband detector
(TND) system
– 12 – IEC 61300-3-29:2014 © IEC 2014
5.2 Light source, S
5.2.1 Tuneable narrowband light source (TNLS) – Method A
This method uses a polarized tuneable narrowband light source (TNLS) that can select a
specific output wavelength and can be tuned across a specified wavelength range. The
“source” could also include a tracking filter, reference branching device (RBD), and
wavelength monitor as shown in Figure 2. These additions are optional as they relate to the
measurement requirements and the TLS specifications.
The power stability at any of the operating wavelengths shall be less than ±0,01 dB over the
measuring period. This stability can be obtained using the optional detector BBD2 in Figure 2
as a reference detector. If BBD2 is synchronized with BBD1, then the variations in power can
be cancelled. It should be noted that the dynamic response of the two power meters should
have the same electrical bandwidth. The output power of the TLS shall be sufficient to provide
the apparatus with an order of magnitude range more dynamic than the device exhibits (i.e.
the measurement apparatus should be able to measure a 50 dB notch if the device is a 40 dB
notch filter).
The wavelength uncertainty of the TLS shall be approximately an order of magnitude smaller
than the step size for each point in the measuring range. This uncertainty may be obtained by
having the wavelength monitor feedback to the TLS. The tuning range of the TLS shall cover
the entire spectral region of the DWDM device and the source shall also be free of mode
hopping over that tuning range.
The side mode suppression ratio and the SSE of the TLS should be sufficient to provide a
signal to noise ratio one order of magnitude greater than is required for the measurement, or
the use of a tracking filter shall be required for notch filter measurements. The SSE can be
measured on an optical spectrum analyser using a 0,1 nm resolution bandwidth. The
measured points should be taken at half the distance between possible DWDM channels (i.e.
at 50 GHz from the centre frequency for a 100 GHz DWDM device). As an example, if the
system needs to measure 50 dB of attenuation, the SSE should be –60 dB.
5.2.2 Broadband source (BBS) – Method B
This method uses an unpolarized broadband light source such as an LED or an amplified
spontaneous emission (ASE) source. The source spectrum shall provide sufficient optical
power over the full wavelength range of the DUT. This factor is especially important in the
measurement of notch filters where the dynamic resolution of the system needs to be high
(typically >50 dB) for accurate measurements.
The optical power of the light source shall either be stable over the duration of the test or
normalized in a wavelength-specific fashion by means of a reference path (possibly consisting
of a RBD and a synchronized TND).
5.3 Tracking filter (TF)
The tracking filter is required if the dynamic range of the TLS and the detector does not allow
for measuring a depth of at least 10 dB greater than required due to the shape of the DUT
and the broadband SSE of the TLS. The filter shall track the TLS so as to provide the
maximum SSE suppression and the maximum transmitted power as the TLS is scanned
across the measurement region. It should be noted that the spectral shape of the filter will
affect the effective linewidth of the system.
5.4 Reference branching device (RBD)
The configuration of the RBD is 1 × 2 or 2 × 2. If its configuration is 2 × 2, one port of the RBD
shall be terminated to have a back reflection of less than –50 dB. The splitting ratio of the
RBD shall be stable with wavelength. It shall also be insensitive to polarization. The
polarization sensitivity of transmission attenuation shall be less than one-tenth of the

wavelength dependency of attenuation to be measured. The polarization mode dispersion of
the RBD shall be less than one half of the coherence time of the source so as not to
depolarize the input signal. The split ratio shall be sufficient to provide the dynamic range for
the measurement of the transfer function and the power necessary for the wavelength meter
to operate correctly.
5.5 Wavelength meter (WM)
In this test procedure, the wavelength uncertainty of the source needs to be extremely small
and closely monitored. If the tuning uncertainty of the TLS is not sufficient for the
measurement, the wavelength monitor shall be required. For this measurement method it is
necessary to measure the spectral peak of any input signal within the device bandwidth to an
uncertainty approximately one order of magnitude greater than the step size. Therefore,
acceptable wavelength monitors include an optical wavelength meter or a gas absorption cell
(such as an acetylene cell). If a gas absorption cell is used, the wavelength uncertainty of the
TLS shall be sufficient to resolve the absorption lines.
Regarding the wavelength repeatability of the TLS and the monitor, it should be understood
that if the test apparatus has 0,1 dB of ripple with a 30 pm period, then a random 3 pm
wavelength variation from reference scan to device scan can result in as much as 0,03 dB of
attenuation error.
5.6 Polarizer (PL)
For the BBS method (Method B), the polarizer shall be put after the BBS. A polarization
extinction ratio of polarizer shall be more than or equal to 20 dB.
5.7 Polarization controller (PC)
The polarization controller is used to control the input state of polarization (SOP). The details
of polarization controller are defined as PSCS in IEC 61300-3-2. That standard defines two
types of PSCS, for all polarization methods and the Mueller matrix method. In the event of a
polarization dependent measurement, the controller will be used to generate four known
polarization states for testing purposes. The states shall be distinct and well known in order to
achieve accurate PDL measurements. The return loss on the input to the controller shall be
greater than 50 dB, so as not to return any polarized light back to the TLS cavity for Method A.
This may also be achieved using an isolator to protect the TLS.
5.8 Device under test (DUT)
5.8.1 General
The device under test shall be DWDM devices. For the purposes of this standard, the test
ports shall be a single “input-output” path. The method described herein can be extrapolated
upon to obtain a single measurement system capable of handling even an M x N DWDM
device. It is noted that these measurements are very sensitive to reflections, and that
precautions shall be taken to ensure that reflection cavities are not introduced in the test set-
up.
In many cases, the characteristics of DWDM devices are temperature dependent. This
measurement procedure assumes that any such device is held at a constant temperature
throughout the procedure. The absolute uncertainty of the measurement may be limited by the
uncertainty of any heating or cooling device used to maintain a constant temperature. For
example, if a device is known to have a temperature dependence of 0,01 nm/°C, and the
temperature during the procedure is held to a set temperature ± 1 °C; then any spectral
results obtained are known to have an uncertainty of 0,02 nm due to temperature.

– 14 – IEC 61300-3-29:2014 © IEC 2014
5.8.2 Device input/output optics
If fibre connectors or fibre butt coupling are employed, use physical contact connectors or
index matching fluid to avoid interference effects.
5.9 Detector (D)
5.9.1 Broadband detectors, BBD1, BBD2, Method A.1
The detectors used for this method consist of a broadband optical detector, the associated
electronics and a means of connecting to an optical fibre. The optical connection may be a
receptacle for an optical connector, a fibre pigtail, or a bare fibre adapter. The back reflection
from detectors BBD1 and BBD2 should be minimized with any precautions available. The
preferred options would be to use either an angled physical contact (APC) connector, or a
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