IEC 60793-1-48:2007

INTERNATIONAL IEC
STANDARD
CEI
60793-1-48
NORME
Second edition
INTERNATIONALE
Deuxième édition
2007-06
Optical fibres –
Part 1-48:
Measurement methods and test procedures –
Polarization mode dispersion
Fibres optiques –
Partie 1-48:
Méthodes de mesure et procédures d’essai –
Dispersion du mode de polarisation
Reference number
Numéro de référence
IEC/CEI 60793-1-48:2007
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INTERNATIONAL IEC
STANDARD
CEI
60793-1-48
NORME
Second edition
INTERNATIONALE
Deuxième édition
2007-06
Optical fibres –
Part 1-48:
Measurement methods and test procedures –
Polarization mode dispersion
Fibres optiques –
Partie 1-48:
Méthodes de mesure et procédures d’essai –
Dispersion du mode de polarisation
PRICE CODE
X
CODE PRIX
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
Pour prix, voir catalogue en vigueur

– 2 – 60793-1-48 © IEC:2007
CONTENTS
FOREWORD.4
INTRODUCTION.6

1 Scope.7
2 Normative references .7
3 Terms and definitions .8
4 General .8
4.1 Methods for measuring PMD .8
4.2 Reference test method .10
4.3 Applicability.10
5 Apparatus.11
5.1 Light source and polarizers .11
5.2 Input optics .11
5.3 Input positioner .12
5.4 Cladding mode stripper .12
5.5 High-order mode filter.12
5.6 Output positioner.12
5.7 Output optics.12
5.8 Detector .12
5.9 Computer .12
6 Sampling and specimens.12
6.1 General .12
6.2 Specimen length.13
6.3 Deployment .13
7 Procedure .14
8 Calculation or interpretation of results .14
9 Documentation .14
9.1 Information required for each measurement .14
9.2 Information to be available .14
10 Specification information .15

Annex A (normative) Fixed analyser measurement method .16
Annex B (normative) Stokes evaluation method .27
Annex C (normative) Interferometry method.32
Annex D (informative) Determination of RMS width from a fringe envelope .42
Annex E (informative) Glossary of symbols .46

Bibliography.48

Figure A.1 – Block diagrams for Method A .16
Figure A.2 – Typical results from Method A.19
Figure A.3 – PMD by Fourier analysis .22
Figure A.4 – Cross-correlation and autocorrelation functions .26

60793-1-48 © IEC:2007 – 3 –
Figure B.1 – Block diagram for Method B .27
Figure B.2 – Typical random-mode-coupling results from Method B .29
Figure B.3 – Typical histogram of DGD values .29
Figure C.1 – Schematic diagram for Method C (generic implementation).32
Figure C.2 – Other schematic diagrams for Method C .34
Figure C.3a – Random mode-coupling using a TINTY-based measurement system
with one I/O SOP .37
Figure C.3b – Negligible mode-coupling using a TINTY-based measurement system
with one I/O SOP .37
Figure C.3 – Fringe envelopes for negligible and random polarization mode-coupling .37
Figure C.4a – Random mode-coupling using a GINTY-based measurement system
with I/O-SOP scrambling.38
Figure C.4b – Negligible mode-coupling using a GINTY-based measurement system
with I/O-SOP scrambling.38
Figure C.4c – Mixed mode-coupling using a GINTY-based measurement system with
I/O-SOP scrambling .39
Figure C.4 – Fringe envelopes for negligible and random polarization mode-coupling
(Ginty procedure).39
Figure D.1 – Parameters for interferogram analysis .42

Table A.1 – Cosine transform calculations .25

– 4 – 60793-1-48 © IEC:2007
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRES –
Part 1-48: Measurement methods and test procedures –
Polarization mode dispersion
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
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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 60793-1-48 has been prepared by subcommittee 86A: Fibres and
cables, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition published in 2003. It constitutes a
technical revision. In this edition, reference to IEC 61282-9 has resulted in the removal of
Annexes E, F, G and H as well as the creation of a new Annex E.
The text of this standard is based on the following documents:
CDV Report on voting
86A/1038/CDV 86A/1078/RVC
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.

60793-1-48 © IEC:2007 – 5 –
This standard is to be read in conjunction with IEC 60793-1-1.
A list of all parts of the IEC 60793 series, published under the general title Optical fibres, can
be found on the IEC website.
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.
– 6 – 60793-1-48 © IEC:2007
INTRODUCTION
Polarization mode dispersion (PMD) causes an optical pulse to spread in the time domain.
This dispersion could impair the performance of a telecommunications system. The effect can
be related to differential phase and group velocities and corresponding arrival times δτ of
different polarization components of the signal. For a sufficiently narrow band source, the
effect can be related to a differential group delay (DGD), Δτ, between pairs of orthogonally
polarized principal states of polarization (PSP) at a given wavelength. For broadband
transmission, the delays bifurcate and result in an output pulse that is spread out in the time
domain. In this case, the spreading can be related to the average of DGD values.
In long fibre spans, DGD is random in both time and wavelength since it depends on the
details of the birefringence along the entire fibre length. It is also sensitive to time-dependent
temperature and mechanical perturbations on the fibre. For this reason, a useful way to
characterize PMD in long fibres is in terms of the expected value, <Δτ>, or the mean DGD
over wavelength. In principle, the expected value <Δτ> does not undergo large changes for a
given fibre from day to day or from source to source, unlike the parameters δτ or Δτ. In
addition, <Δτ> is a useful predictor of lightwave system performance.
The term "PMD" is used both in the general sense of two polarization modes having different
group velocities, and in the specific sense of the expected value <Δτ>. The DGD Δτ or pulse
broadening δτ can be averaged over wavelength, yielding <Δτ> , or time, yielding <Δτ> , or
λ t
temperature, yielding <Δτ> . For most purposes, it is not necessary to distinguish between
T
these various options for obtaining <Δτ>.
The coupling length l is the length of fibre or cable at which appreciable coupling between
c
,
the two polarization states begins to occur. If the fibre length L satisfies the condition L << l
c
mode coupling is negligible and <Δτ> scales with fibre length. The corresponding PMD
coefficient is
"short-length" PMD coefficient = <Δτ>/L.
Fibres in practical systems are nearly always in the L >> l , regime and mode coupling is
c
random. If mode coupling is also found to be random, <Δτ> scales with the square root of
fibre length, and
"long-length" PMD coefficient = <Δτ>/ L

60793-1-48 © IEC:2007 – 7 –
OPTICAL FIBRES –
Part 1-48: Measurement methods and test procedures –
Polarization mode dispersion
1 Scope
This part of IEC 60793 applies to three methods of measuring polarization mode dispersion
(PMD), which are described in Clause 4. It establishes uniform requirements for measuring
the PMD of single-mode optical fibre, thereby assisting in the inspection of fibres and cables
for commercial purposes.
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 60793-1-1, Optical fibres – Part 1-1: Measurement methods and test procedures –
General and guidance
IEC 60793-1-44, Optical fibres – Part 1-44: Measurement methods and test procedures –
Cut-off wavelength
IEC 60793-2-50, Optical fibres – Part 2-50: Product specifications – Sectional specification for
class B single-mode fibres
IEC 60794-3, Optical fibre cables – Part 3: Sectional specification – Outdoor cables
IEC 61280-4-4, Fibre optic communication subsystem test procedures – Part 4-4: Cable
plants and links – Polarization mode dispersion measurement for installed links
IEC/TR 61282-3, Fibre optic communication system design guides – Part 3: Calculation of link
polarization mode dispersion
IEC/TR 61282-9, Fibre optic communication system design guides – Part 9: Guidance on
polarization mode dispersion measurements and theory
IEC 61290-11-1, Optical amplifier test methods – Part 11-1: Polarization mode dispersion –
Jones matrix eigenanalysis method (JME)
IEC 61290-11-2, Optical amplifiers – Test methods – Part 11-2: Polarisation mode dispersion
parameter – Poincaré sphere analysis method
IEC/TR 61292-5, Optical amplifiers – Part 5: Polarization mode dispersion parameter –
General information
IEC 61300-3-32, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 3-32: Examinations and measurements – Polarization
mode dispersion measurement for passive optical components
ITU-T Recommendation G.650.2, Definitions and test methods for statistical and non-linear
related attributes of single-mode fibre and cable

– 8 – 60793-1-48 © IEC:2007
3 Terms and definitions
For the purposes of this document, the terms and definitions contained in ITU-T
Recommendation G.650.2 apply.
NOTE Further explanation of their use in this document is provided in IEC 61282-9.
4 General
4.1 Methods for measuring PMD
Three methods are described for measuring PMD (see Annexes A, B and C for more details).
The methods are listed below in the order of their introduction. For some methods, multiple
approaches of analyzing the measured results are also provided.
– Method A
• Fixed analyser (FA)
• Extrema counting (EC)
• Fourier transform (FT)
• Cosine Fourier transform (CFT)
– Method B
• Stokes parameter evaluation (SPE)
• Jones matrix eigenanalysis (JME)
• Poincaré sphere analysis (PSA)
• State of polarization (SOP)
– Method C
• Interferometry (INTY)
• Traditional analysis (TINTY)
• General analysis (GINTY)
The PMD value is defined in terms of the differential group delay (DGD), Δτ, which usually
varies randomly with wavelength, and is reported as one or another statistical metric.
Equation (1) is a linear average value and is used for the specification of optical fibre cable.
Equation (2) is the root mean square value which is reported by some methods. Equation (3)
can be used to convert one value to the other if the DGDs are assumed to follow a Maxwell
random distribution.
PMD = Δτ (1)
AVG
1/ 2
PMD = Δτ (2)
RMS
1/ 2
⎛ ⎞ 1/ 2
Δτ =⎜ ⎟ Δτ (3)
3π
⎝ ⎠
NOTE Equation (3) applies only when the distribution of DGDs is Maxwellian, for instance when the fibre is
randomly mode coupled. The generalized use of Equation (3) can be verified by statistical analysis. A Maxwell
distribution may not be the case if there are point sources of elevated birefringence (relative to the rest of the
fibre), such as a tight bend, or other phenomena that reduce the mode coupling, such as a continual reduced bend
radius with fibre in tension. In these cases, the distribution of the DGDs will begin to resemble the square root of a
non-central Chi-square distribution with three degrees of freedom. For these cases, the PMD value will
RMS
generally be larger relative to the PMD that is indicated in Equation (3). Time domain methods such as Method
AVG
C and Method A, cosine Fourier transform, which are based on PMD , can use Equation (3) to convert to
RMS
PMD . If mode coupling is reduced, the resultant reported PMD value from these methods may exceed those
AVG
that can be reported by the frequency domain measurements that report PMD , such as Method B.
AVG
60793-1-48 © IEC:2007 – 9 –
The PMD coefficient is the PMD value normalized to the fibre length. For normal transmission
fibre, for which random mode coupling occurs and for which the DGDs are distributed as
Maxwell random variables, the PMD value is divided by the square root of the length and the
1/2
PMD coefficient is reported in units of ps/km . For some fibres with negligible mode
coupling, such as polarization maintaining fibre, the PMD value is divided by the length and
the PMD coefficient is reported in units of ps/km.
All methods are suitable for laboratory measurements of factory lengths of optical fibre and
optical fibre cable. For all methods, changes in the deployment of the specimen can alter the
results. For installed lengths of optical fibre cable that may be moving or vibrating, either
Method C or Method B (in an implementation capable of millisecond measurement time
scales) is appropriate.
All methods require light sources that are controlled at one or more states of polarization
(SOPs). All methods require injecting light across a broad spectral region (i.e. 50 nm to
200 nm wide) to obtain a PMD value that is characteristic of the region (i.e. 1 300 nm or
1 550 nm). The methods differ in:
a) the wavelength characteristics of the source;
b) the physical characteristics that are actually measured;
c) the analysis methods.
Method A measures PMD by measuring a response to a change of narrowband light across a
wavelength range. At the source, the light is linearly polarized at one or more SOPs. For each
SOP, the change in output power that is filtered through a fixed polarization analyser, relative
to the power detected without the analyser, is measured as a function of wavelength. The
resulting measured function can be analysed in one of three ways.
– By counting the number of peaks and valleys (EC) of the curve and application of a
1)
formula that has been shown [1] to agree with the average of DGD values, when the
DGDs are distributed as Maxwellian. This analysis is considered as a frequency domain
approach.
– By taking the FT of the measured function. This FT is equivalent to the pulse spreading
obtained by the broadband transmission of Method C. Appropriate characterisation of the
width of the FT function agrees with the average of DGD values, when the DGDs are
distributed as Maxwellian.
– By taking the cosine Fourier transform of the difference of the normalized spectra from two
orthogonal analyzer settings and calculating the RMS of the squared envelope. The
PMD value is reported. This is equivalent to simulating the fringe pattern of the cross-
RMS
correlation function that would result from interferometric measurements.
Method B measures PMD by measuring a response to a change of narrowband light across a
wavelength range. At the source, the light is linearly polarized at one or more SOPs. The
Stokes vector of the output light is measured for each wavelength. The change of these
Stokes vectors with angular optical frequency, ω and with the (optional) change in input SOP
yields the DGD as a function of wavelength through relationships that are based on the
following definitions:
()
ds ω
= Ω()ω × s(ω) (4)
dω
Δτ()ω = Ω(ω) (5)
where
s is the normalized output Stokes vector;
___________
1)
Figures in square brackets refer to the Bibliography.

– 10 – 60793-1-48 © IEC:2007
Ω is the polarization dispersion vector (PDV) in the direction of the PSPs;
Δτ is the DGD.
For both the JME and PSA analysis approaches, three linear SOPs at nominally 0°, 45°, and
90° (orthogonal on the Poincaré sphere) must be launched for each wavelength.
The JME approach is completed by transforming the output Stokes vectors to Jones matrices
[2], appropriate combination of the matrices at adjacent wavelengths, and a calculation using
the eigenvalues of the result to obtain the DGD, by application of an argument formula, at the
base frequency.
The PSA approach is completed by doing matrix algebra on the normalized output Stokes
vectors to infer the rotation of the output Stokes vector on the Poincaré sphere at two
adjacent wavelengths, using the application of an arcsine formula to obtain the DGD. The
JME and PSA approaches are mathematically equivalent for common assumptions (see
IEC 61282-9).
The SOP approach is based on a piecewise evaluation of Equation (4) using the normalized
measured Stokes vectors. The SOP approach can yield good results when the transit of the
output Stokes vector is well behaved (negligible mode-coupling) but can produce incorrect
results when the output Stokes vector changes rapidly and randomly (see IEC 61282-9). The
extra measurement time required for the three input SOPs for JME and PSA result in a more
robust measurement.
Method C is based on a broadband light source that is linearly polarized. The cross-
correlation of the emerging electromagnetic field is determined by the interference pattern of
output light, i.e. the interferogram. The determination of the PMD delay for the wavelength
range associated with the source spectrum is based on the envelope of the fringe pattern of
the interferogram. Two analyses are available to obtain the PMD delay (see IEC 61282-9),
both of which measure the PMD value:
RMS
– TINTY uses a set of specific operating conditions for its successful applications and a
basic setup;
– GINTY uses no limiting operating conditions but in addition to the same basic set-up also
using a modified setup compared to TINTY.
With the exception of the Method B SOP approach, the analysis approaches represent an
evolution of the understanding of PMD. The GINTY is, for example, more complete than
TINTY. The reproducibility of PMD depends on the PMD level and the wavelength range of
the measurement [3]. Better relative reproducibility is achieved for broader wavelength ranges
and higher PMD values for a given range. For measurements of higher PMD values, e.g.,
0,5 ps, the differences in the analysis methods are less important than for the measurements
of low PMD values.
Information common to all three methods is contained in Clauses 4 to 10, and requirements
pertaining to each individual method appear in Annexes A, B, and C, respectively. IEC 61282-9
provides the mathematical formulations for all methods.
4.2 Reference test method
Method B, SPE (only JME and PSA approaches), is the reference test method (RTM), which
shall be the one used to settle disputes.
4.3 Applicability
PMD in fibre is a statistical parameter. IEC 60794-3 includes a statistical requirement on
PMD, called PMD or link design value, that is based on sampled measurements of optical
Q
fibre cable and calculations for concatenated links. The PMD of a cabled fibre can vary from
the PMD of the uncabled fibre due to effects of cable construction and processing. A limit on

60793-1-48 © IEC:2007 – 11 –
the PMD of the uncabled fibre is, however, required to limit the PMD on cabled fibre.
Q Q
Uncabled fibre PMD less than half the cabled fibre PMD limit is generally considered as a
Q Q
conservative rule. Alternative limits may be determined for particular constructions and stable
cable processes.
The fibre or cable deployment should be selected so externally induced mode-coupling is
minimized. Sources of such external mode-coupling can be:
a) excessive tension;
b) excessive bending induced from
• fibre cross-overs on a shipping reel;
• crimping of fibre within a cable on a spool that is too small;
• too small a bend radius;
c) excessive twist.
Reproducibility of individual measurements should be evaluated after perturbing the fibre to
allow sampling the full range of mode-coupling combinations. This can be done by, for
example, changing the temperature slightly or making small adjustments in the deployment.
Gisin [3] reported a fundamental relative reproducibility limit for measurements and showed
that the relative reproducibility improves as the PMD increases and as the spectral width of
the source increases. When PMD measurements are combined to evaluate the statistical
specification of optical fibre cable (see IEC 60794-3), this variability leads to a possible
overstatement of the link design value.
Guidelines for the calculation of PMD for systems that include other components such as
dispersion compensators or optical amplifiers are given in IEC 61282-3. Test methods for
optical amplifiers are given in IEC 61290-11-1 and IEC 61290-11-2, and other design guides
in IEC 61292-5. Test methods for testing links including amplified ones are given in
IEC 61280-4-4. Test methods for optical components are given in IEC 61300-3-32. General
information about PMD, the mathematical formulation related to the application of the present
methods, and some considerations related to the sampling theory related to the use of
different light sources and detection systems are given in IEC 61282-9.
5 Apparatus
The following apparatus is common to all three measurement methods. Annexes A, B, and C
include layout drawings and other equipment requirements for each of the three methods,
respectively.
5.1 Light source and polarizers
See Annexes A, B, and C for detailed options of the spectral characteristics of the light
source. The source shall produce sufficient radiation at the intended wavelength(s) and be
stable in intensity over a time period sufficient to perform the measurement. IEC 61282-9
provides additional guides concerning the source input SOP, degree of polarization (DOP),
use of polarizers and polarization controllers.
5.2 Input optics
An optical lens system or fibre pigtail may be employed to excite the specimen. It is recom-
mended that the power coupled into the specimen be relatively insensitive to the position of
its input end face. This can be accomplished by using a launch beam that spatially and
angularly overfills the input end face.
If using a butt splice, employ index-matching material between the fibre pigtail and the
specimen to avoid interference effects. The coupling shall be stable for the duration of the
measurement.
– 12 – 60793-1-48 © IEC:2007
5.3 Input positioner
Provide means of positioning the input end of the specimen to the light source. Examples
include the use of x-y-z micropositioner stages, or mechanical coupling devices such as
connectors, vacuum splices, three-rod splices, etc. The position of the fibre shall remain
stable over the duration of the measurement.
5.4 Cladding mode stripper
Use a device that extracts cladding modes. Under some circumstances the fibre coating will
perform this function.
5.5 High-order mode filter
Use a means to remove high-order propagating modes in the desired wavelength range that is
greater than or equal to the cut-off wavelength (see IEC 60793-1-44) of the specimen. For
example, a one-turn bend of radius = 30 mm on the fibre is generally sufficient.
5.6 Output positioner
Provide a suitable means for aligning the fibre output end face to the output optics. Such
coupling may include the use of lenses, or may be a mechanical connector to a detector
pigtail.
Provide means such as a side-viewing microscope or camera with a crosshair to locate the
fibre at a fixed distance from the output optics. It may be sufficient to provide only longitudinal
adjustment if the fibre is constrained in the lateral plane by a device such as a vacuum chuck.
5.7 Output optics
See Annex A, B, or C, as appropriate.
5.8 Detector
For signal detection, an optical detector is used which is linear and stable over the range of
intensities and measurement times that are encountered in performing the measurement.
A typical system might include synchronous detection by a chopper/lock-in amplifier, an
optical power meter, optical spectrum analyser, or a polarimeter. To use the entire spectral
range of the source, the detection system must have a wavelength range which includes the
wavelengths produced by the light source. See Annex A, B, or C, as appropriate, for
additional details.
5.9 Computer
Use a computer to perform operations such as controlling the apparatus, taking intensity
measurements, and processing the data to obtain the final results.
6 Sampling and specimens
6.1 General
A specimen is a known length of single-mode optical fibre (IEC 60793-2-50) which may or
may not be cabled. The sample and pigtails must be fixed in position at a nominally constant
temperature throughout the measurement. Standard ambient conditions shall be employed
unless otherwise specified. In the case of installed fibres and cables, prevailing deployment
conditions may be used.
Mechanical and temperature stability of the test device may be observed by the following
procedures. For Method A, the output power from the fibre at a fixed wavelength is measured

60793-1-48 © IEC:2007 – 13 –
with the output analyser in place. In a time period corresponding to a typical complete
measurement, the output power change should be small relative to the changes produced by
a wavelength increment. For Method B, the output SOP of the test fibre on a Poincaré sphere
display is viewed. In a time period corresponding to an adjacent pair of Jones matrix
measurements, the output SOP change should be small relative to the change produced by a
wavelength increment. Method C is normally robust with regard to slight temperature change
or fibre movements.
End faces for the input and output ends of the test sample must be prepared as appropriate
for the requirements of the apparatus and procedure. Precautions shall be taken to avoid any
reflections.
6.2 Specimen length
The specimen length is dictated by three factors:
a) minimum desired PMD coefficient;
b) mode-coupling regime;
c) signal to noise ratio.
Each test method and implementation is limited to a minimum PMD value (ps) that can be
measured. In many cases, this minimum can be determined on the basis of theory. It can also
be determined experimentally by examining the measured distribution. For fibres in the
random mode-coupling regime, the minimum PMD coefficient is determined by dividing the
PMD value by the square root of the fibre length (km). For the negligible mode-coupling case,
the division is by the length. The length that is measured and the minimum measurable PMD
value will therefore determine the minimum measurable PMD coefficient. Fibres or cables with
lengths sufficient to achieve this minimum can be selected for measurement. Alternatively,
specimens can be cut to a length that is satisfactory. The minimum measurable PMD value
shall be documented. The length of the individual specimens shall be recorded.
NOTE The length may also be limited by the deployment method (see 6.3) and instrument dynamic range.
The values specified in IEC 60794-3 and IEC 60793-2-50 express the PMD coefficient in
terms of ps/√km – in effect, these documents assume that the length measured is sufficient to
induce the randomly mode-coupled regime. For a given fibre type or cable construction, this
can be confirmed by doing a cut-back experiment in which the PMD value is measured on a
specimen at each of several lengths – achieved by cutting the specimen back between
measurements. Lengths above which there is a square root dependence of the PMD value on
length may be considered as randomly mode-coupled.
The dynamic range is limited by the method, the source power, and the overall loss of the
specimen, which is affected by length. This limit must generally be determined on the basis of
specific implementations by experimental means. This limit shall be documented.
6.3 Deployment
The deployment of the fibre or cable can influence the result. For normal measurements to be
used in specification conformance evaluation, the following requirements apply.
6.3.1 Uncabled fibre
It is important to minimize deployment induced mode coupling when measuring uncabled
fibres, which is done in order to support the primary requirements of cabled fibre PMD . In
Q
this case, the fibre shall be supported in some manner (usually on a reel having a minimum
wind radius of 150 mm), with essentially zero fibre tension (typically less than 5 g), and no
tensioned crossovers. These deployment requirements can limit the length that can be
measured, depending on the spool diameter, and can make the measurement a destructive
one. Multi-layer windings are possible, but should be qualified by comparison with single-layer
results on shorter lengths.
– 14 – 60793-1-48 © IEC:2007
The measurement of uncabled fibre deployed on shipping spools is not recommended. PMD
results with this deployment have been shown to be substantially less than what would be
obtained in cable form for high PMD fibre and substantially greater than what would be
obtained in cable form for low PMD fibre.
6.3.2 Optical fibre cable
PMD measurements on fibres in cables wound on shipping drums may not always reflect the
functionally relevant PMD values for fibres in the installed cable deployment configuration.
Consequently, to demonstrate compliance with the cabled-fibre PMD specification, alternative
deployment configurations or mapping functions relating on-drum PMD value to off-drum PMD
value may be used for factory measurements. The exact deployment configuration shall be
agreed upon between the supplier and the customer.
7 Procedure
7.1 Deploy the fibre or cable and prepare the ends.
7.2 Attach the ends to the input and output optics.
7.3 Engage the computer to complete the scans and measurements found in Annexes A, B,
and C for the three measurement methods.
7.4 Complete documentation.
8 Calculation or interpretation of results
Annexes A, B, and C provide calculations to convert the measured data into PMD values. The
calculation of the PMD coefficient is carried out according to whether random mode coupling
or negligible mode coupling is present. For the fibres specified in IEC 60793-2-50, the PMD
1/2
value is normalized by the square root of the fibre length in units of ps/km .
9 Documentation
9.1 Information required for each measurement
a) Specimen identification
b) Testing date
c) Specimen length
d) Wavelength region (for example, 1 550 nm)
e) PMD in units of ps, and whether PMD or PMD is reported
AVG RMS
f) PMD coefficient and its units (ps/√km or ps/km)
9.2 Information to be available
a) Measurement method used
b) Calculation approach used
c) Description of the deployment method (including any fibre support mechanism)
d) Wavelength range used
e) For Methods A and B with a narrowband source and a step mode, the number of
wavelengths sampled
f) For Method C, the type of fringe-detection technique

60793-1-48 © IEC:2007 – 15 –
g) Description of the equipment
h) Date of latest calibration
i) Evidence supporting the mode-coupling regime (indicated by units of the PMD coefficient)
j) For Method B with narrowband source and a step mode, the wavelength range resolution
k) For Method B with broadband source (BBS), the centre wavelength and –3 dB linewidth
10 Specification information
a) Type of fibre or cable
b) Failure or acceptance criteria
c) Wavelength region
d) Any deviations from this procedure

– 16 – 60793-1-48 © IEC:2007
Annex A
(normative)
Fixed analyser measurement method

This annex contains requirements specific to Method A (FA).
A.1 Apparatus
Figure A.1 shows possible block diagrams.

Monochromator
Test fibre
Lamp Chopper
Polarizer
Analyzer
Computer
Lock-in
Detector
amplifier
IEC  781/07
Figure A.1a – Narrowband source

Polarizer
Analyzer
Test
Splice
Splice
Broadband
fibre
Optical spectrum
source
analyzer
IEC  782/07
Figure A.1b – Broadband source
Figure A.1 – Block diagrams for Method A
A.1.1 Light source
In all cases, two kinds of light sources may be used, depending on the type of analyser.
A narrowband source such as the broadband lamp and monochromator combination shown in
Figure A.1a can be used with a polarization analyser. A BBS, shown in Figure A.1b, can be
used with a narrow bandpass filtering analyser, such as an opti
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