IEC 61290-11-1:2008

IEC 61290-11-1
Edition 2.0 2008-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical amplifiers – Test methods –
Part 11-1: Polarization mode dispersion parameter – Jones matrix eigenanalysis
(JME)
Amplificateurs optiques – Méthodes d’essais –
Partie 11-1: Paramètre de dispersion du mode de polarisation – Analyse des
vecteurs propres de la matrice de Jones (JME)

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IEC 61290-11-1
Edition 2.0 2008-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical amplifiers – Test methods –
Part 11-1: Polarization mode dispersion parameter – Jones matrix eigenanalysis
(JME)
Amplificateurs optiques – Méthodes d’essais –
Partie 11-1: Paramètre de dispersion du mode de polarisation – Analyse des
vecteurs propres de la matrice de Jones (JME)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
M
CODE PRIX
ICS 33.180.30 ISBN 2-8318-8771-2

– 2 – 61290-11-1 © IEC:2008
CONTENTS
FOREWORD.3

1 Scope and object.5
2 Normative references .5
3 Acronyms, symbols and abbreviations .6
4 Apparatus.6
4.1 General .6
4.2 Tuneable laser .7
4.3 Polarization adjuster.7
4.4 Polarizers.7
4.5 Input optics .7
4.6 Fibre pigtail .7
4.7 Optical lens system .7
4.8 Output optics.7
4.9 Polarimeter.7
5 Procedure .8
6 Calculations .8
6.1 Jones matrix eigenanalysis calculations .8
6.2 Display of DGD versus wavelength.9
6.3 Average DGD .9
6.4 Maximum DGD .9
7 Test results .9

Annex A (informative) Degree of polarization reduction due to optical amplifier ASE.11

Bibliography.13

Figure 1 – Schematic diagram of equipment (typical) .6
Figure 2 – Measurement example of the DGD for a typical optical amplifier .9
Figure A.1 – Spectrum of optical amplifier output .11

61290-11-1 © IEC:2008 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL AMPLIFIERS –
TEST METHODS –
Part 11-1: Polarization mode dispersion parameter –
Jones matrix eigenanalysis (JME)

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 61290-11-1 has been prepared by subcommittee 86C: Fibre optic
systems and active devices, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition, published in 2003, and is a
technical revision that specifically addresses additional types of optical amplifiers. It also
includes updated references.
The text of this standard is based on the following documents:
CDV Report on voting
86C/752/CDV 86C/786/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.

– 4 – 61290-11-1 © IEC:2008
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 61290 series, under the general title Optical amplifiers – Test
methods, 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.
61290-11-1 © IEC:2008 – 5 –
OPTICAL AMPLIFIERS –
TEST METHODS –
Part 11-1: Polarization mode dispersion parameter –
Jones matrix eigenanalysis (JME)

1 Scope and object
This part of IEC 61290 applies to all commercially available optical amplifiers (OAs), including
optical fibre amplifiers (OFAs) using active fibres, semiconductor optical amplifiers (SOAs),
and planar waveguide optical amplifiers (PWOAs).
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 group velocity and corresponding arrival times of different
polarization components of the signal. For a narrowband source, the effect can be related to
a differential group delay (DGD) between pairs of orthogonally polarized principal states
of polarization (PSP). Other information about PMD may be found in IEC 61282-9 in general
and in IEC 61292-5 on OAs in particular.
This test method describes a procedure for measuring the PMD of OAs. The measurement
result is obtained from the measurement of the normalized Stokes parameters at two closely
spaced wavelengths.
The test method described herein requires a polarized signal at the input of the polarimeter
with a degree of polarization (DOP) of at least 25 %. Although the test source is highly
polarized, the DOP at the output of the OA is reduced by amplified spontaneous emission
(ASE). Annex A analyses the impact of ASE on the DOP. In order to assure an accurate
measurement, the DOP is measured as part of the measurement procedure.
The method described herein has been shown to be immune to polarization-dependent gain
(PDG) and polarization dependent loss (PDL) up to approximately 1 dB.
Although the Jones matrix eigenanalysis (JME) test method is in principle also applicable to
unpumped (that is, unpowered) OAs, the JME technique in this standard applies to pumped
(that is, powered) OAs only.
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/TR 61282-9, Fibre optic communication system design guides – Part 9: Guidance on
polarization mode dispersion measurements and theory
IEC/TR 61292-5, Optical amplifiers – Part 5: Polarization mode dispersion parameter –
General information
– 6 – 61290-11-1 © IEC:2008
3 Acronyms, symbols and abbreviations
Δλ Wavelength interval
Δτ Differential group delay (DGD)
ν Optical frequency
ω Angular optical frequency
F OA noise factor
G Gain
h Plank’s constant
N(γ) Power spectral density of the ASE
P Amplified signal power
s
ASE Amplified spontaneous emission
DGD Differential group delay
DOP Degree of polarization
DUT Device (optical amplifier) under test
JME Jones matrix eigenanalysis
OA Optical amplifier
OFA Optical fibre amplifier
PDG Polarization-dependent gain
PDL Polarization-dependent loss
PMD Polarization-mode dispersion
PWOA Planar waveguide optical amplifier
PSP Principal states of polarization
SOA Semiconductor optical amplifier
4 Apparatus
4.1 General
Figure 1 provides a schematic diagram of the key components in a typical measurement
system.
Polarimeter
Tunable laser
Polarization
adjuster
DUT
0° 45° 90°
Linear polarizers
IEC  393/03
Figure 1 – Schematic diagram of equipment (typical)

61290-11-1 © IEC:2008 – 7 –
4.2 Tuneable laser
Use single-line lasers or narrowband sources that can be varied or tuned across the intended
measurement wavelength range. The spectral distribution shall be narrow enough so that light
on the DUT remains polarized under all conditions of the measurement.
4.3 Polarization adjuster
If the source is polarized, a polarization adjuster follows the laser and is set to provide
roughly circularly polarized light to the polarizers, so that the polarizers never cross polar-
ization with the input light. If the source is unpolarized, this is not necessary. For the
polarized source, adjust the polarization as follows.
a) Set the tuneable laser wavelength to the centre of the range to be measured.
b) Insert each of the three polarizers into the beam and perform three corresponding power
measurements at the output of the polarizer.
c) Adjust the source polarization via the polarization adjuster in such a way that
the three powers fall within approximately a 3-dB range of one another.
In an open-beam version of the set-up, waveplates may perform the polarization adjustment.
4.4 Polarizers
Three linear polarizers at relative angles of approximately 45 ° are arranged to be inserted
into the light beam in turn. The actual relative angles shall be known.
4.5 Input optics
An optical lens system or single-mode fibre pigtail may be employed to excite the DUT.
4.6 Fibre pigtail
If pigtails are used, interference effects due to reflections should be avoided. This may require
index matching materials or angled cleaves. The pigtails shall be single-mode.
4.7 Optical lens system
If an optical lens system is used, some suitable means, such as a vacuum chuck, shall be
used to support in a stable manner the input end of the fibre.
4.8 Output optics
Couple all power emitted from the test fibre to the polarimeter. An optical lens system, a butt-
splice to a single-mode fibre pigtail or an index-matched coupling made direct to the detector
are examples of means that may be used.
4.9 Polarimeter
Use a polarimeter to measure the three output states of polarization corresponding to
insertion of each of the three polarizers. The wavelength range of the polarimeter shall
include the wavelengths produced by the light source.

– 8 – 61290-11-1 © IEC:2008
5 Procedure
a) Couple the light source through the polarization adjuster to the polarizers.
b) Couple the output of the polarizers to the input of the DUT.
c) Couple the output of the DUT to the input of the polarimeter.
λ over which the normalized Stokes parameters are
d) Select the wavelength interval Δ
to be measured. The maximum allowable value of Δλ (around the nominal wavelength λ )
is set by the requirement
λ
Δτ Δλ ≤ (1)
max
2c
where Δτ is the maximum expected DGD within λ ± Δλ/2. For example, the product of
max 0
the maximum DGD and the wavelength interval shall remain less than 4 ps×nm at 1 550 nm
and less than 2,8 ps×nm at 1300 nm. This requirement ensures that from one test
wavelength to the next, the output state of polarization rotates less than 180 ° about
the principal states axis on the Poincaré sphere. If a rough estimate of Δτ cannot be
max
made, perform a series of sample measurements across the wavelength range, each
measurement using a closely spaced pair of wavelengths appropriate to the spectral width
and minimum tuning step of the optical source. Multiply the maximum DGD measured in
this way by a safety factor of 3, substitute this value for Δτ in the above expression
max
and compute the value of Δλ to be used in the actual measurement. If there is concern
that the wavelength interval used for a measurement was too large, the measurement may
be repeated with a smaller wavelength interval. If the shape of the curve of DGD versus
wavelength and the mean DGD is essentially unchanged, the original wavelength interval
was satisfactory.
e) Gather the measurement data. At the selected wavelengths, insert each of the polarizers
and record the corresponding normalized Stokes parameters from the polarimeter.
f) Calculate the DOP from the measured normalized Stokes parameters to determine if the
measurement is valid.
2 2 2
DOP = s + s + s (2)
1 2 3
If the DOP is greater than 25 %, the measurement is valid. If the DOP is less than 25 %,
increase the tuneable laser power and repeat step e).
6 Calculations
6.1 Jones matrix eigenanalysis calculations
From the normalized Stokes parameters, compute the response Jones matrix at each
wavelength. For each wavelength interval, compute the product of the Jones matrix Τ(ω+Δω)
−1
at the higher optical frequency and the inverse Jones matrix Τ (ω) at the lower optical
frequency. The radian optical frequency ω is expressed in radians per second and is related
to the optical frequency ν by ω = 2πν.
Find the DGD Δτ for the particular wavelength interval from the following expression:
⎛ ⎞
ρ
⎜ ⎟
Arg
⎜ ⎟
ρ
⎝ 2⎠
(3)
Δτ =
Δω
61290-11-1 © IEC:2008 – 9 –
–1
where ρ and ρ are the complex eigenvalues of Τ(ω+Δω) Τ (ω) and Arg denotes the
1 2
iθ
argument function, that is Arg(ηe ) = θ. For the purposes of data analysis, each DGD value is
taken to represent the differential group delay at the midpoint of the corresponding
wavelength interval.
6.2 Display of DGD versus wavelength
Data arising from Jones matrix eigenanalysis calculations may be plotted in an x-y format with
DGD on the vertical axis and wavelength on the horizontal axis as shown in Figure 2.
0,2
0,15
0,1
Average DGD = 0,12 ps
0,05
1 540 1 545 1 550 1 555 1 560 1 565
Wavelength  nm
IEC  394/03
NOTE The DOP for this measurement ranges from 57 % to 79 %.
Figure 2 – Measurement example of the DGD for a typical optical amplifier
6.3 Average DGD
The expected PMD value of a single measurement is simply the average of the DGD
measurement values corresponding to the wavelength intervals. If multiple measurements
are performed under different conditions to increase the sample size, the ensemble average
is used.
6.4 Maximum DGD
The maximum DGD is the maximum measured value over the wavelength range.
7 Test results
Report the following information for each test:
a) the wavelength range over which the measurement was performed, and the wavelength
step size (nm);
b) the value of DGD at each wavelength (ps);
c) the average DGD across the specified wavelength range (ps);
d) the maximum DGD across the specified wavelength range (ps);
e) the minimum DOP across the wavelength range;
f) arrangement of the test set-up, including the type of tunable laser and its spectral
linewidth;
DGD  ps
– 10 – 61290-11-1 © IEC:2008
g) an indication of the amplifier operating condition during measurement, for example, optical
pump power (if applicable) for OFAs or electrical pump conditions (if applicable) for SOAs;
h) ambient temperature (if required).

61290-11-1 © IEC:2008 – 11 –
Annex A
(informative)
Degree of polarization reduction due to optical amplifier ASE

In order for the polarimeter to measure the Stokes parameters accurately, the DOP of the
measured signal must be greater than 25 %. The ASE generated in the DUT is unpolarized
and therefore reduces the DOP of the highly polarized tunable laser source. Figure A.1 shows
a typical OFA output spectrum as viewed on an OSA.
+10 dBm
Amplified signal
ASE
–40 dBm
1 575 nm
1 525 nm
IEC  395/03
NOTE The OSA resolution bandwidth is 0,5 nm.
Figure A.1 – Spectrum of optical amplifier output
Assuming that the signal is highly polarized and the ASE is unpolarized, the DOP is given by
the following equation:
P
s
DOP = (A.1)
P + N(λ)dλ
s
∫
where P is the amplified signal power and N(λ) is the power spectral density of the ASE. The
s
integral in the denominator is the total ASE power. For an OFA, the value of N at the signal
wavelength can be calculated as follows:
N = FGhν  (A.2)
where F is the OA noise factor, G is the gain, h is Plank’s constant, and ν is the optical
frequency. Typical values for a heavily saturated amplifier are as follows:
F = 4   (6 dB)
G = 100  (20 dB)
P = 10 mW (+10 dBm)
s
–19
For h ν = 1,28 × 10 , N is calculated as follows:

– 12 – 61290-11-1 © IEC:2008
–19 –17 –6
N = 4 × 100 × 1,28 × 10 = 5,12 × 10 W/Hz ~ 6,4 × 10 W/nm = −21,9 dBm/nm.
Assuming a 30 nm bandwidth, the total ASE power is 0,19 mW = −7,2 dBm. Using Equation
(A.1), DOP is calculated as 10/(10 + 0,19) = 98 %. This value is more than adequate for
making DGD measurements.
However, if the signal level is low
...