IEC 61290-10-1:2009

IEC 61290-10-1 ®
Edition 2.0 2009-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical amplifiers – Test methods –
Part 10-1: Multichannel parameters – Pulse method using an optical switch and
optical spectrum analyzer
Amplificateurs optiques – Méthodes d'essai
Partie 10-1: Paramètres à canaux multiples – Méthode d’impulsion utilisant un
interrupteur optique et un analyseur de spectre optique
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IEC 61290-10-1 ®
Edition 2.0 2009-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical amplifiers – Test methods –
Part 10-1: Multichannel parameters – Pulse method using an optical switch and
optical spectrum analyzer
Amplificateurs optiques – Méthodes d'essai
Partie 10-1: Paramètres à canaux multiples – Méthode d’impulsion utilisant un
interrupteur optique et un analyseur de spectre optique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
T
CODE PRIX
ICS 33.180.30 ISBN 978-2-88910-479-6
– 2 – 61290-10-1 © IEC:2009
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope and object.7
2 Normative references .7
3 Abbreviated terms .7
4 Apparatus.8
5 Test sample.10
6 Procedure .10
6.1 Calibration.11
6.1.1 Calibration of OSA power measurement .11
6.1.2 Calibration of the pulse duty ratio .11
6.1.3 Calibration of the sampling module.12
6.1.4 Calibration of dynamic isolation .13
6.2 OA measurement .15
6.2.1 Timing adjustment for ASE and amplified signal power measurement.15
6.2.2 ASE measurement.16
6.2.3 Amplified signal power measurement.16
7 Calculation .17
7.1 General .17
7.2 Noise factor calculation .18
7.3 ASE power .18
7.4 Gain calculation .19
7.5 Average output signal power .19
7.6 Noise figure calculation .19
8 Test results .19
Annex A (informative) Output waveforms for various EDFAs at 25 kHz and 500 kHz
pulse rates.20
Annex B (informative) Measurement accuracy versus pulse rate.22
Annex C (informative) Pulse repetition frequency measurements.23
Bibliography.24

Figure 1 – Typical arrangement of the optical pulse test method .8
Figure 2 – Two arrangements of the optical pulse source.9
Figure 3 – Static isolation of an optical switch.9
Figure 4 – Definitions of rise time and fall time, t and t of optical pulses .10
r f
Figure 5 – Measurement flow chart .11
Figure 6 – Arrangement for the sampling switch calibration.12
Figure 7 – Arrangement for timing adjustment.13
Figure 8 – Timing adjustment of the sampling switch .14
Figure 9 – Timing chart for dynamic isolation calibration .15
Figure 10 – Arrangement for OA measurement .16
Figure 11 – Timing chart for ASE measurement .17
Figure 12 – Timing chart for amplified signal power measurement .17

61290-10-1 © IEC:2009 – 3 –
Figure A.1 – EDFA output waveforms for various EDFAs .21
Figure B.1 – NF measurement accuracy versus pulse rate.22
Figure C.1 – Set-up to evaluate gain recovery error versus modulation rate.23
Figure C.2 – Gain recovery error versus modulation frequency with pump current as a
parameter .23

– 4 – 61290-10-1 © IEC:2009
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL AMPLIFIERS –
TEST METHODS –
Part 10-1: Multichannel parameters –
Pulse method using an optical switch
and optical spectrum analyzer
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 61290-10-1 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. It is a technical
revision with updated references and cautions on proper use of the procedure.
This International Standard is to be read in conjunction with IEC 61291-1.
The text of this standard is based on the following documents:
CDV Report on voting
86C/778/CDV 86C/809/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.

61290-10-1 © IEC:2009 – 5 –
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 61290 series, published under the general title Optical amplifiers –
1)
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.
___________
1)
The first editions of some of these parts were published under the general title Optical fibre amplifiers – Basic
specification or Optical amplifier test methods.

– 6 – 61290-10-1 © IEC:2009
INTRODUCTION
This International Standard is devoted to the subject of optical fibre amplifiers. The technology
of optical fibre amplifiers is still rapidly evolving, hence amendments and new editions to this
standard can be expected.
61290-10-1 © IEC:2009 – 7 –
OPTICAL AMPLIFIERS –
TEST METHODS –
Part 10-1: Multichannel parameters –
Pulse method using an optical switch
and optical spectrum analyzer
1 Scope and object
This part of IEC 61290 applies to optical amplifiers (OAs) using active fibres and waveguides,
containing rare-earth dopants, currently commercially available.
The object of this standard is to establish uniform requirements for accurate and reliable
measurements of the signal-spontaneous noise figure as defined in IEC 61291-1.
The test method independently detects amplified signal power and amplified spontaneous
emission (ASE) power by launching optical pulses into the OA under test and synchronously
detecting "on" and "off" levels of the output pulses by using an optical sampling switch and an
optical spectrum analyzer (OSA).
Such measurement is possible because the gain response of the rare-earth doped OA is
relatively slow, particularly in Er-doped OAs. However, since the OA gain dynamics vary
with amplifier types, operating conditions and control schemes, the gain dynamics should be
carefully considered when applying the present test method to various OA. The manufacturer of
the OA should present data validating the required modulation frequency to limit the error to
<1 dB. The measurements for obtaining this information are described in Annex C.
The test method is described basically for multichannel applications, which includes single
channel applications as a special case of multichannel (wavelength-division multiplexed)
applications.
NOTE All numerical values followed by (‡) are currently under study.
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 61291-1, Optical amplifiers – Part 1: Generic specification
3 Abbreviated terms
For the purposes of this document, the following abbreviated terms apply:
AGC automatic gain control
ALC automatic level control
AOM acousto-optic modulator
APC automatic power control
ASE amplified spontaneous emission
CW continuous wave
– 8 – 61290-10-1 © IEC:2009
DBR distributed Bragg reflector (laser diode)
DC direct current
DFB distributed feed-back (laser diode)
ECL external cavity laser (diode)
EDFA erbium-doped fibre amplifier
ER erbium
FWHM full width at half maximum
LED light emitting diode
LD laser diode
NF noise figure
OA optical amplifier
OSA optical spectrum analyzer
SW switch
4 Apparatus
The basic measurement set-up is given in Figure 1.

OA under test
Optical pulses
typical repetition rate
500 kHz to 1 000 kHz
Optical spectrum
Optical pulse
OA
SW
analyzer
source
Trigger
IEC  310/09
Figure 1 – Typical arrangement of the optical pulse test method
The test equipment needed, with the required characteristics, is listed below.
a) Optical pulse source: Two arrangements of the optical pulse source are possible as shown in
Figure 2. Optical pulse source a (Figure 2a) consists of CW optical sources with an external
optical switch and attenuator(s). Optical pulse source b (Figure 2b) consists of directly
modulated optical sources and attenuator(s).
Optical pulse source
Optical attenuator(s)
Optical sources
operating at CW
dB
Optical switch
IEC  311/09
Figure 2a – Arrangement with external optical switch

61290-10-1 © IEC:2009 – 9 –
Optical pulse source
Optical attenuator(s)
Optical sources
pulsated by direct
modulation dB
IEC  312/09
Figure 2b – Arrangement with directly modulated optical source

Figure 2 – Two arrangements of the optical pulse source
Unless otherwise specified, the full width at half maximum (FWHM) of the output spectrum of
optical pulse source a or b shall be narrower than 0,1 nm (‡) so as not to cause any
interference to adjacent channels. In the case of a single-channel source, it shall be
narrower than 1 nm (‡). Distributed feedback (DFB) lasers, distributed Bragg reflection (DBR)
lasers, and external cavity lasers (ECLs), for example, are applicable. The suppression ratio
of the side modes of these DFB lasers shall be higher than 30 dB (‡). The output power
fluctuation shall be less than 0,05 dB (‡), which may be more easily attainable with an optical
isolator placed at the output port of each source.
Optical pulse source a simultaneously pulsates wavelength-division multiplexed light with an
optical switch, where the switching time is common to all the channels; timing adjustment is
not needed. Moreover, frequency chirping and spontaneous emission can be minimum; the
extinction ratio of the "on" versus "off" stages can be uniquely determined at a high level if a
high extinction-ratio switch is used. An acousto-optic modulator (AOM) is typically used as
the switch.
For optical pulse source b, the leakage power at the off-state should be as small as possible
to minimize the measurement error, although calibration is possible by subtracting the
leaked power. This may demand a zero-bias operation of laser diode sources. Moreover,
care must be taken in synchronizing optical pulses because the pulse timing may differ from
one source to another.
b) Variable optical attenuator: The attenuation range and stability shall be over 40 dB (‡) and
better than ± 0,1 dB (‡), respectively. The reflectance from this device shall be smaller than
−40 dB (‡) at each port. The variable optical attenuator may be incorporated in the optical
pulse source.
c) Optical switch: This device shall have a polarization sensitivity less than ± 0,1 dB (‡), static
isolation better than 65 dB (‡), transition time less than 50 ns (‡), and switching delay time
less than 2 ms (‡). The reflectance from this device shall be smaller than –40 dB (‡) at each
port. Figure 3 defines the optical switch static isolation. The optical switch is not required for
optical pulse source b.
Switching signal
Output
pulse
Power
Light
SW
meter
source
P
IEC  313/09 off -state
ISO =
static
P
on-state
Figure 3 – Static isolation of an optical switch
d) Pulse generator: This device is used to drive optical pulse sources and the optical sampling
switch. When using an internally modulated optical pulse source, an independent pulse
generator is not required. Pulse train(s) shall be generated with a pulse interval of, typically,
1 μs to 2 μs (‡). The pulse widths shall be adjustable from 100 ns to 2 ms (‡) with a step of
5 ns or finer. The delay shall be adjustable at least from 100 ns to 4 μs (‡) in steps of 5 ns or

– 10 – 61290-10-1 © IEC:2009
finer. The rise time and fall time, t and t , of the output optical pulse shall be less than 10 ns
r f
(‡). Definitions of t and t are given in Figure 4.
r f
SW
output
10 % pulse
to
90 %
Time
t
f
t
r
IEC  314/09
Figure 4 – Definitions of rise time and fall time, t and t of optical pulses
r f
e) Optical spectrum analyzer: This device shall have polarization sensitivity less than
0,1 dB (‡), stability better than ±0,1 dB (‡),wavelength accuracy better than ±0,5 nm (‡), and
wavelength reproducibility better than 0,01 nm (‡). The device shall have a measurement
range at least from –75 dBm to +20 dBm (‡) with a resolution better than 0,1 nm (‡). The
reflectance from this device shall be smaller than –40 dB (‡) at its input port.
f) Optical power meter: This device shall have a measurement accuracy better than ±0,2 dB
(‡), irrespective of the state of the input light polarization, within the operational wavelength
band of the OA and within a power range from –40 dBm to +20 dBm (‡).
g) Optical connectors: The connection loss repeatability shall be better than ±0,1 dB (‡). The
reflectance from this device shall be smaller than –40 dB (‡).
h) Optical fibre jumpers: The mode field diameter of the optical fibre jumpers shall be as close
as possible, so as not to cause excessive loss and reflectance, to that of fibres used as input
and output ports of the OA. The reflectance from optical fibre jumpers shall be smaller than
–40 dB (‡), and the device length shall be short (<2 m).
5 Test sample
The OA shall operate at nominal operating conditions. If the OA is likely to cause laser
oscillations due to unwanted reflections, optical isolators should be used to bracket the OA
under test. This will minimize the signal instability and the measurement inaccuracy.
Care shall be taken in the state of polarization of the input light during the measurement.
Changes in the polarization state of the input light may result in input optical power changes
because of the slight polarization dependency expected from all the optical components used,
leading to measurement errors.
6 Procedure
The test procedure consists of four parts:
a) initial system setting and calibration;
b) sampling window adjustment;
c) OA measurement and
d) calculation.
61290-10-1 © IEC:2009 – 11 –
The measurement flow is given in Figure 5. This procedure enables self-consistent calculation of
not only OA noise factor but also ASE power and signal gain.

Start
Initial system setting
λ to λ
1 N
Initial calibration
OA setting
Sampling window
adjustment for OA
OA parameter setting
λ to λ
1 N
Measurement
Calculation
and printout
Parameter change
IEC  315/09
Figure 5 – Measurement flow chart
6.1 Calibration
6.1.1 Calibration of OSA power measurement
Calibrate the OSA power measurement by using a calibrated power meter.
NOTE The calibrated optical power meter detects all the optical power including source spontaneous emission,
whereas the OSA measurement detects just the optical power within the resolution bandwidth of the OSA. Therefore,
use of an optical filter with a FWHM passband of 1 nm to 3 nm is recommended at the output of the optical pulse source
to increase the calibration accuracy.
6.1.2 Calibration of the pulse duty ratio
Follow the steps below to calibrate the pulse duty ratio.
a) Activate any one channel of the optical pulse source at CW and the specified power and
wavelength.
b) Set the pulse width T and the pulse interval T of the optical pulse source output as
source
specified in the product specification. T and T shall be sufficiently shorter than the
source
gain-response time of the OA under test. For EDFAs, T and T are typically 0,4 μs (‡)
source
– 12 – 61290-10-1 © IEC:2009
and 1 μs (‡), respectively. These values, however, depend on the amplifier saturation
condition.
NOTE Measurement accuracy versus pulse rates is given in informative Annex B. EDFA output waveforms for
various EDFAs are given in informative Annex A.
c) Measure the average output power, P , with a power meter.
pulse-ave
d) Drive the optical pulse source with 100 % duty pulse (DC drive), and measure the output
power, P , with a power meter.
DC
e) Calculate the equivalent duty ratio by using Equation (1).

P
pulse-ave
DR = (1)
source
P
DC
NOTE For the optical pulse source using an external optical switch, the calibration result is applicable to the
other channels.
For the optical pulse source using direct modulation, the calibration shall be repeated for all the
channels, because the optical-pulse shape generated by each source can be different.
6.1.3 Calibration of the sampling module
Follow the steps below to calibrate the sampling module.
a) Arrange the optical pulse source, sampling SW, OSA and calibrated power meter as shown
in Figure 6.
T
sampler
Sampling pulse
T
P
CW-calibrated
CW light
OSA
SW
source
Calibrated
power meter
IEC  316/09
Figure 6 – Arrangement for the sampling switch calibration
b) Activate the optical pulse source to emit CW light at a channel wavelength to be tested.
c) Set the OSA optical bandwidth, B , in a way to accommodate the spectral bandwidth of the
o
pulse signal.
d) Adjust the OSA centre wavelength to the wavelength selected at step b).
e) Set the sampling pulse width, T , as specified in the product specification. The sum of
sampler
the duty ratios, the source duty ratio plus sampler duty ratio, shall be less than 100 % while
still keeping some margin, e.g., 80 % to 90 %. T shall be smaller than T . Measure
sampler source
the average output power, P with the OSA.
OSA-pulse-ave
f) Drive the sampling switch with a 100 % duty pulse (DC drive).
g) Measure P with the OSA.
OSA-DC
h) Calculate the equivalent sampling switch duty ratio by using Equation (2).
P
OSA −pulse−ave
DR = (2)
sampler
P
OSA-DC
61290-10-1 © IEC:2009 – 13 –
NOTE The value of DR thus obtained at one channel wavelength is applicable to the other channel
sampler
wavelengths.
i) Measure the input power to the sampling switch, P , with a calibrated power meter.
CW-calibd
j) Activate the optical pulse source to emit CW light at the next channel wavelength to be tested.
Repeat steps g) through i) for the next channel wavelength to be measured.
k) Calculate the calibration factor, CAL(λ ), of the sampler including the OSA by using
k
Equation (3).
P
OSA −DC
CAL(λ )= (3)
k
P
CW −calibd
6.1.4 Calibration of dynamic isolation
6.1.4.1 Timing adjustment of the sampling switch (SW)
Follow the steps below for timing adjustment of the sampling switch.
a) Connect the optical pulse source and the sampling switch plus OSA with a fibre cord as
shown in Figure 7, in which optical pulse source a is illustrated as the optical pulse source.
Optical pulse source b is also applicable here.
Optical pulse source
Fibre cord
Narrow band
Sampling SW OSA
SW
dB
optical source
CH-1
Pulse
generator
CH-2
T
d
IEC  317/09
Figure 7 – Arrangement for timing adjustment
b) Activate the optical pulse source to emit light at all channel wavelengths.
NOTE Although the delay time can be determined by using just one channel, the present test procedure
activates all the channels at this stage so that the multichannel optical pulse source can be better stabilized for
later stages of the measuring procedure.
c) Adjust the OSA centre wavelength to one arbitrary channel wavelength.
d) Set the drive pulse timing for the optical pulse source and the sampling switch as shown in
Figure 8. DR shall be smaller than DR .
sampler source
e) Find the delay time, T , that minimizes the received optical power with the OSA by tuning
d-min
the CH2 delay time T .
d
f) Calculate the delay time T that maximizes the received optical power with the OSA by
d-max
using Equation (4).
T
p
T = T – (4)
d-max d-min
NOTE The delay time thus obtained at one channel wavelength is applicable to the other channel wavelengths.

– 14 – 61290-10-1 © IEC:2009
Source output
Source module
SW output
Fibre cord
input pulses
Fibre cord
output pulses
Fibre cord delay
Sampling
SW output
T
d
OSA input
Time
Leakage signal Leakage signal
from source module from sampler
IEC  318/09
Figure 8 – Timing adjustment of the sampling switch
6.1.4.2 Dynamic isolation
Follow the steps below to calculate the dynamic isolation.
a) Keep activating the optical pulse source to emit light pulses at all channel wavelengths.
NOTE All the channels need to be active when measuring the dynamic isolation. This is because, although the
dynamic isolation is measured by tuning the OSA to one channel, the OSA should receive all the optical powers
including those from adjacent channels.
b) Connect the optical pulse source and the sampling switch plus OSA with a fibre cord as
shown in Figure 7.
Sig
c) Set the sampling switch timing as shown in Figure 9a. Measure P with the OSA
OSA-ave
tuned to the channel to be tested.
Leak
d) Set the sampling switch timing as shown in Figure 9b. Measure P with the OSA

OSA-ave
tuned to the same channel as in step c).
e) Repeat steps c) and d) for the different channels to be tested.
f) Calculate the average dynamic isolation of each channel, ISO(λ ) , by using
k
dyna-ave
Equation (5).
Leak
OSA−ave
P
ISO(λ ) = (5)
k
dyna-ave
Sig
OSA−ave
P
61290-10-1 © IEC:2009 – 15 –
Fibre cord
output
Sampling
Sw output
T
d_min
T
d_max
OSA input
Time
Leakage signal Leakage signal
from source module  from sampler
IEC  319/09 IEC  320/09
Sig Leak
Figure 9a – Measurements of P Figure 9b – Measurements of P
OSA-ave OSA-ave
Figure 9 – Timing chart for dynamic isolation calibration
6.2 OA measurement
6.2.1 Timing adjustment for ASE and amplified signal power measurement
Follow the steps below to adjust the timing for ASE and amplified signal power measurement.
a) Keep activating the optical pulse source to emit pulsed light at all channel wavelengths.
NOTE Although the timing can be adjusted by using just one channel, all the channels are kept activated so that
the multichannel optical pulse source can be stable.
b) Connect the optical pulse source, the OA under test, the sampling switch and the OSA as
shown in Figure 10, in which optical pulse source a is illustrated. Optical pulse source b is
also applicable instead.
c) Activate the OA under test as specified in the detail specification while avoiding surge
generation.
d) Tune the OSA to one arbitrary channel wavelength.
e) Set the drive pulse timing to the optical pulse source and the sampling switch as shown in
Figure 10, in which the sampling switch is driven out of phase with the optical pulse source
for ASE measurement.
ASE
f) Find the delay time of T that minimizes P by tuning the CH2 delay time T .
d-ASE OSA-ave d
Sig-OA-out
g) Calculate the delay time T , that maximizes P by using Equation (6).
d-sig OSA-ave
T
p
T = T − (6)
d-sig d-ASE
NOTE The delay time thus obtained at one channel wavelength is applicable to the other channel wavelengths.

– 16 – 61290-10-1 © IEC:2009
OFA under test
Optical pulse source
Optical spectrum
Narrow-band
Sampling
OA
dB
SW
analyzer
optical source
SW
λ ∼ λ
1 N Tuned at one
wavelength
Pulse generator
CH1
CH2
Typically at 1 MHz
For ASE measurement
For gain measurement
Switch time chart
IEC  321/09
Figure 10 – Arrangement for OA measurement
6.2.2 ASE measurement
Follow the steps below to measure the ASE.
a) Keep activating the optical pulse source to emit pulsed light at all channels.
b) Set the average signal power of each channel into the OA, P , as specified in a detail
OA-in-ave
specification. P can be adjusted by using an OSA as follows:
OA-in-ave
1) Connect the optical pulse source and the sampling switch with a fibre cord.
2) Set the sampling switch timing: T as given in Equation (4)
d-max,
Sig
3) Measure P with the OSA at the wavelength under test.
OSA-ave
4) P is given in Equation (7).
OA-in-ave
DR
source
sig-OA-in
P(λ ) = P(λ ) (7)
k OA-in-ave k OSA-ave
CAL (λ ) × DR
k sampler
c) For single-channel applications, instead of following the above steps 1) to 4), P can
OA-in-ave
be adjusted by using the calibrated power meter.
d) Set the sampling module timing, as determined by item e) of 6.2.1, to measure the ASE
power. The timing chart is given in Figure 11.
ASE
e) Measure P with the OSA at the channel under test.
OSA-ave
NOTE This power depends on the resolution bandwidth of the OSA.
ASE
f) Measure P with the OSA at the next channel to be tested while keeping other
OSA-ave
conditions unchanged.
6.2.3 Amplified signal power measurement
a) Keep activating the optical pulse source to emit pulsed light at all channels.
b) Set the sampling switch timing as determined by step g) of 6.2.1 to measure the signal power.
The timing chart is given in Figure 12.
c) Keep P for all the channels at the same levels as for the ASE measurement.
OA-in-ave
sig-OA-out
d) Measure P with the OSA at the wavelength under test.
OSA-ave
61290-10-1 © IEC:2009 – 17 –
sig-OA-out
e) Measure P with the OSA at the next channel to be tested while keeping other
OSA-ave
conditions unchanged.
Source
SW output
OFA input
OFA output
OFA delay
Sampling
SW output
T
d
OSA input
Time
IEC  322/09
Figure 11 – Timing chart for ASE measurement

Source
SW output
OFA input
OFA outputs
OFA delay
Sampling
SW output
T
d_signal
OSA input
Time
IEC  323/09
Figure 12 – Timing chart for amplified signal power measurement
7 Calculation
7.1 General
Since the following parameter values differ depending on the channel under test, the calculation
needs to be conducted at each channel by using the parameter values specific to each channel.

– 18 – 61290-10-1 © IEC:2009
P(λ ) Average input signal power, mW
k OA-in-ave
ASE
Average ASE power measured with the OSA, mW
P(λ )
k OSA-ave
sig-OA-out
Average output signal power from OA measured with the OSA, mW
P(λ )
k OSA-ave
ASE(λ , B ) ASE power within the optical bandwidth of the OSA, mW
k 0
CAL(λ ) Calibration factor of the sampler plus OSA
k
Average dynamic isolation, dB
ISO(λ )
k dyna-ave
Linear gain
G(λ )
k
F(λ ) Signal-spontaneous noise factor (expressed in linear form)
k sig-sp
NF(λ ) Signal-spontaneous noise figure, dB
k sig-sp
7.2 Noise factor calculation
,
Noise factor, F at each channel at a wavelength, λ, is given by using the following
sig-sp
equations:
ASE
P ISO × P
dyna−ave OA −in−ave
OSA −ave
F = − (8)
sig−sp
CAL × Ghνh DR hv B DR
0 sampler 0 0 source
or
ASE sig-OA-out
F = (P − ISO × P ) (9)
sig-sp OSA-ave dyna-ave OSA-ave
CAL × GhvB DR
0 sampler
where
B is the OSA resolution bandwidth, in Hz,
h is Planck's constant,
ν is the optical signal frequency, in Hz.
NOTE The second terms in Equations (8) and (9) are used to cancel the effect of the signal leakage in ASE
measurement.
By measuring the ASE power distribution around the signal wavelength, the ASE power
excluding the signal leakage at the signal wavelength can be estimated by an interpolation
technique. F can be given by using Equation (10)
sig-sp
ASE
P OSA - ave - interpolated
F = (10)
sig-sp
CAL × GhvB DR
0 sampler
7.3 ASE power
ASE power at the OA output is given by using Equation (11) or (12).
ASE
ISO
P dyna-ave
OSA -ave
ASE(B ) = − G × P -in-ave (11)
OA
o
CAL × DR DR
sampler source
or
61290-10-1 © IEC:2009 – 19 –
ASE sig-OFA-out
ASE(B ) = (12)
(P − ISO × P
OSA -ave OSA -ave
o dyna-ave
CAL × DR
sampler
7.4 Gain calculation
Signal linear gain is given by using the following equations;
sig-OFA-out ASE
{ P (1+ ISO ) − P } DR
OSA -ave OSA -ave
dyna-ave source
= (13)
G
CAL × P × DR
OFA-in-ave sampler
or
sig-OFA-out ASE
P (1+ ISO ) − P
OSA -ave OSA -ave
dyna-ave
G = (14)
sig-OFA-IN
P
OSA -ave
7.5 Average output signal power
Average output signal power is given by using Equation (15).
sig-OFA-out ASE
{ P (1+ ISO ) − P } DR
OSA -ave OSA -ave
dyna-ave source
P = (15)
OA-out-ave
CAL × DR
sampler
7.6 Noise figure calculation
Noise figure NF is obtained from noise factor F by using Equation (16).
NF = 10 log(F) (16)
8 Test results
The following details shall be presented for each channel:
a) Wavelength range of the measurement
b) Spectral linewidth (FWHM) of the optical source
c) Input signal wavelength: λ
k
OSA optical bandwidth: B
o
d)
e) Indication of the optical pump power (if applicable)
f) Ambient temperature
Pulse interval: T Signal pulse width: T , Sampler width: T
g) , source sample
Average input signal power: P
OA-in-ave
h)
Average output signal power: P
OA-out-ave
i)
j) Linear gain, G
k) ASE power: ASE(B )
o
l) Noise factor: F or Noise figure: NF
SIG-SP SIG-SP
– 20 – 61290-10-1 © IEC:2009
Annex A
(informative)
Output waveforms for various EDFAs at 25 kHz and 500 kHz pulse rates

Figure A.1 shows examples of the output waveform for various types of EDFAs (see NOTE). It is
seen from a) to c) of Figure A.1, in which the pulse rate is 25 kHz, that the EDFA gain changes
within one pulse waveform and also varies with EDFA types of A, B and C.
NOTE Type A EDFA is operated at a constant pump power under saturated regime. Type B EDFA has a relatively
slow automatic power control (APC), whereas type C EDFA has a quick APC with an operating band >25 kHz.
The gain change disappears for type C EDFA when the pulse rate is increased to 500 kHz as is
seen from c) and d) of Figure A.1. Thus, the gain measurement and, accordingly, the NF
measurement are accurate at > 500 kHz.

61290-10-1 © IEC:2009 – 21 –
IEC  324/09
a) EDFA type A at 25 kHz
IEC  325/09
b) EDFA type B at 25 kHz
IEC  326/09
c) EDFA type C at 25 kHz
IEC  327/09
d) EDFA type C at 500 kHz
Figure A.1 – EDFA output waveforms for various EDFAs

– 22 – 61290-10-1 © IEC:2009
Annex B
(informative)
Measurement accuracy versus pulse rate

Examples of the NF measurement accuracy versus pulse rate are shown in Figure B.1, where
optical pulse source a (see Clause 4, Figure 2) was used. The AOM switches were used for
source pulsation and sampling, respectively. Measurement conditions were AOM switches:
1 MHz; pulse duty ratios: 0,4 for pulsation and 0,2 for sampling; wavelength-division multiplexed
channels: 1 550,4 nm, 1 551,2 nm, 1 552,0 nm and 1 552,8 nm; Total OA input power: 0 dBm;
OA gain: 9 dB to 17 dB.
NF
Deviation
[dB ]
0,5
–0,5
–1
1 000 750 500 250 100 75 50 25
Pulse repetition rate [kHz]
1 550,4 nm 1 551,2 nm
1 552,0 nm 1 552,8 nm
IEC  328/09
Figure B.1 – NF measurement accuracy versus pulse rate
The NF value was stable for pulse rates higher than about 250 kHz, where the effect of the
waveform distortion due to the slow gain dynamics of EDFAs, as seen in Figure A.1, no longer
exists. Figure B.1 indicates that high measurement accuracy is achieved at a pulse rate
>250 kHz.
61290-10-1 © IEC:2009 – 23 –
Annex C
(informative)
Pulse repetition frequency measurements
The measurements described in this annex are possible because the gain response of the
rare-earth doped fibre amplifier is relatively slow, that is >100 μs for Er-doped fibre amplifiers.
Currently, the gain recovery times allow pulse repetition rates in the 25 kHz to 100 kHz range. A
simple set-up to evaluate OA gain response versus modulation frequency is shown in Figure C.1.
An optical source with variable modulation frequency is applied to the OA. The average output
power of the OA is measured on an optical power meter. As the modulation frequency is
increased, the power meter reading asymptotically approaches a final value. At low modulation
frequencies there is an increasing error due to non-linear gain recovery of the OA.
OA
Optical power
Pulse modulated
meter
optical source
IEC  329/09
Figure C.1 – Set-up to evaluate gain recovery error versus modulation rate
Figure C.2 shows a measurement on a 980 nm pumped Er-doped fibre amplifier with three
values of pump current. As pump power increases, the gain recovery time constant becomes
shorter, resulting in a larger deviation from the high-frequency value. For this particular amplifier,
a modulation frequency above 20 kHz is required to give <0,1 dB error in measured gain at
500 mA pump current.
–0,2
100 mA
–0,4
200 mA
–0,6
–0,8
500 mA
–1,0
–1,2
–1,4
1 10 100 1 000
Modulation frequency  (kHz)
IEC  330/09
Figure C.2 – Gain recovery error versus modulation frequ
...