IEC 62343-5-2:2018
(Main)Dynamic modules - Part 5-2: Test methods - 1 x N fixed-grid WSS - Dynamic crosstalk measurement
Dynamic modules - Part 5-2: Test methods - 1 x N fixed-grid WSS - Dynamic crosstalk measurement
IEC 62343-5-2:2018 describes the measurement methods of dynamic crosstalk during port switching for 1 x N fixed-grid wavelength selective switches (WSSs). The objective of this document is to establish a standard test method for different-channel dynamic crosstalk and same-channel dynamic crosstalk that occur when a particular optical channel signal is switched to the specific branching port against a common port in ITU‑T 50 GHz and 100 GHz fixed grid 1 x N (N ≥ 3) WSSs.
Modules dynamiques - Partie 5-2: Méthodes d'essai - Commutateurs sélectifs en longueur d'onde à grille fixe 1 x N - Mesure de diaphonie dynamique
IEC 62343-5-2: 2018 décrit les méthodes de mesure de diaphonie dynamique pendant la commutation des ports pour les commutateurs sélectifs en longueur d'onde à grille fixe 1 x N. Le présent document a pour but d'établir une méthode d'essai normalisée sur la diaphonie dynamique sur différents canaux et la diaphonie dynamique sur un même canal qui se produisent lorsque le signal d'un canal optique particulier est commuté sur le port de couplage spécifique par rapport à un port commun dans des commutateurs sélectifs en longueur d'onde à grille fixe 1 x N (N ≥ 3) de 50 GHz et 100 GHz selon l'UIT-T.
Mots clés: diaphonie dynamique
General Information
Standards Content (Sample)
IEC 62343-5-2 ®
Edition 1.0 2018-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Dynamic modules –
Part 5-2: Test methods – 1 x N fixed-grid WSS – Dynamic crosstalk measurement
Modules dynamiques –
Partie 5-2: Méthodes d'essai – Commutateurs sélectifs en longueur d'onde à
grille fixe 1 x N – Mesure de diaphonie dynamique
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IEC 62343-5-2 ®
Edition 1.0 2018-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Dynamic modules –
Part 5-2: Test methods – 1 x N fixed-grid WSS – Dynamic crosstalk measurement
Modules dynamiques –
Partie 5-2: Méthodes d'essai – Commutateurs sélectifs en longueur d'onde à grille
fixe 1 x N – Mesure de diaphonie dynamique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.01 33.180.99 ISBN 978-2-8322-5267-3
– 2 – IEC 62343-5-2:2018 © IEC 2018
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviated terms . 6
3.1 Basic terms . 6
3.2 Performance parameter terms . 8
3.3 Abbreviated terms . 9
4 Apparatus . 10
4.1 Test set-up . 10
4.2 Light source . 10
4.2.1 Tuneable laser source (TLS) . 10
4.2.2 Broadband light source and tuneable filter . 11
4.3 Device under test . 11
4.4 Detector . 12
4.4.1 Optical power meter (OPM) . 12
4.4.2 OE converter and oscilloscope . 12
5 Measurement condition . 13
5.1 General conditions . 13
5.2 Recommendations on selections of a branching port and channel . 13
6 Procedure . 13
6.1 Preparation . 13
6.2 Measurement . 14
6.2.1 Measurement of input power and insertion loss of DUT . 14
6.2.2 Measurement of noise power for dynamic crosstalk . 14
6.2.3 Measurement of noise power for different channel crosstalk . 14
6.2.4 Measurement of noise power for same channel crosstalk . 14
7 Example of transient characteristics of noise power . 15
8 Calculation . 17
9 Measurement report . 19
Bibliography . 21
Figure 1 – Noise observed in port during conducting port switching in 1 x N WSS . 9
Figure 2 – Test set-up to measure dynamic crosstalk . 10
Figure 3 – Transient characteristics for measurement of different channel dynamic
crosstalk . 16
Figure 4 – Transient characteristics for measurement of same channel dynamic
crosstalk . 17
Table 1 – Example of template for measurement results for different channel dynamic
crosstalk . 19
Table 2 – Example of summary of crosstalk measurement . 20
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DYNAMIC MODULES –
Part 5-2: Test methods – 1 x N fixed-grid WSS –
Dynamic crosstalk measurement
FOREWORD
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International Standard IEC 62343-5-2 has been prepared by subcommittee 86C: Fibre optic
systems and active devices, of IEC technical committee 86: Fibre optics.
The text of this International Standard is based on the following documents:
CDV Report on voting
86C/1449/CDV 86C/1480/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62343 series, published under the general title Dynamic modules,
can be found on the IEC website.
– 4 – IEC 62343-5-2:2018 © IEC 2018
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document 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.
INTRODUCTION
Dynamic crosstalk is attributed to both channel crosstalk (due to same wavelength and/or
other wavelengths) and port isolation. It is predicted to change during port switching
operations and is a significant performance issue studied and summarized in
IEC TR 62343-6-9 for 1 x N (N ≥ 3) wavelength selective switches (WSSs).
It was revealed that dynamic crosstalk exists in actual 1 x N (N ≥ 3) WSSs in
IEC TR 62343-6-9 and predicted that it would influence transmission properties to some
extent when a specific channel passes through the WSS.
This document standardizes the measurement method of dynamic crosstalk of 1 x N (N ≥ 3)
WSSs.
This document is based on OITDA DM 01 from the Optoelectronic Industry and Technology
Development Association (OITDA).
– 6 – IEC 62343-5-2:2018 © IEC 2018
DYNAMIC MODULES –
Part 5-2: Test methods – 1 x N fixed-grid WSS –
Dynamic crosstalk measurement
1 Scope
This part of IEC 62343 describes the measurement methods of dynamic crosstalk during port
switching for 1 x N fixed-grid wavelength selective switches (WSSs).
The objective of this document is to establish a standard test method for different-channel
dynamic crosstalk and same-channel dynamic crosstalk that occur when a particular optical
channel signal is switched to the specific branching port against a common port in
ITU-T 50 GHz and 100 GHz fixed grid 1 x N (N ≥ 3) WSSs.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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 61300-3-29, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 3-29: Examinations and measurements – Spectral
transfer characteristics of DWDM devices
IEC TR 61931, Fibre optic – Terminology
IEC 62343, Dynamic modules – General and guidance
IEC TS 62538, Categorization of optical devices
ISO/IEC Guide 99, International vocabulary of metrology – Basic and general concepts and
associated terms (VIM)
3 Terms, definitions and abbreviated terms
For the purposes of this document, the terms and definitions given in IEC TR 61931,
IEC 62343, IEC TS 62538, ISO/IEC Guide 99, and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Basic terms
3.1.1
fixed grid
grid where the frequency of channel spacings of WSSs having a port configuration of 1 x N
(N ≥ 2) is predetermined for all channels and not variable
3.1.2
port pair
combination of one input port and one arbitrary output port among N ports, as for a WSS
having a port configuration of 1 x N (N ≥ 2)
Note 1 to entry: It is also valid when the WSS is used as an N x 1 port configuration. In this case, the port pair is
defined as a combination of one arbitrary input port among N ports and one output port, as for the WSS having a
port configuration of N x 1 (N ≥ 2).
3.1.3
conducting port pair
two ports, i and j, between which transfer coefficient, t , which is defined in IEC TS 62627-09,
ij
is nominally greater than zero
Note 1 to entry: The conducting port pair is defined at a specific switching state and a specified wavelength.
3.1.4
isolated port pair
two ports, i and j, between which transfer coefficient, t , which is defined in IEC TS 62627-09,
ij
is nominally zero, and logarithmic transfer coefficient, a , which is defined in IEC TS 62627-09,
ij
is nominally infinite
Note 1 to entry: The isolated port pair is defined at a specific switching state and a specified wavelength.
3.1.5
attenuating port pair
two ports, i and j, between which transfer coefficient, t , which is defined in IEC TS 62627-09,
ij
is nominally greater than zero and smaller than the insertion loss
Note 1 to entry: The attenuating port pair is defined at a specific switching state and a specified wavelength.
3.1.6
conducting channel
channel intended to be conducted at the specific conducting port pair
3.1.7
isolated channel
channel intended to be isolated at the specific conducting port pair
3.1.8
common port
port for the "1" side, not for the "N" side, with a WSS having a port configuration of 1 x N
(N ≥ 2)
3.1.9
branching port
port for the "N" side, not for the "1" side, with a WSS having a port configuration of 1 x N
(N ≥ 2)
3.1.10
static state
state when the conducting port pair, isolated port pair and attenuating port pair are not under
switching and/or attenuating operation, and the optical power is kept within 10 % in linear
scale at any intended conduction port pair
3.1.11
dynamic state
state when at least one conducting port pair, isolated port pair or attenuating port pair is
under switching and/or attenuating operation, and the optical power varies more than 10 % in
linear scale at a specific intended conduction port pair in this state
– 8 – IEC 62343-5-2:2018 © IEC 2018
3.2 Performance parameter terms
3.2.1
crosstalk
ratio of the transfer coefficient of the power to be isolated to the transfer coefficient for the
power to be conducted for an output port
Note 1 to entry: Crosstalk is generally a negative value expressed in dB.
Note 2 to entry: For fibre optic filters and WDM devices, crosstalk is defined for one port pair at two or more
different wavelengths (channels).
Note 3 to entry: For fibre optic switches, crosstalk is defined for two or more port pairs at one wavelength.
Note 4 to entry: Crosstalk for a passive optical device (component) is generally the maximum value of crosstalks
for all port pairs defining crosstalks.
Note 5 to entry: For WSSs, crosstalk is defined for two or more port pairs at two or more different wavelengths
(channels).
[SOURCE: IEC TS 62627-09:2016, 3.4.10, modified — Note 5 has been added.]
3.2.2
static crosstalk
crosstalk in a static state for a 1 x N (N ≥ 2) WSS, specified by the unintended signal
transmission ratio divided by the intended signal transmission ratio
Note 1 to entry: Static crosstalk is generally a negative value expressed in dB.
Note 2 to entry: Two types of static crosstalk are defined: different channel static crosstalk and same channel
static crosstalk.
3.2.3
different channel static crosstalk
static crosstalk, specified by the ratio of the isolated channel power divided by the conducting
channel power in the same conducting port pair, when the input channel power in the isolated
channel and conducting channel is the same
Note 1 to entry: Different channel static crosstalk is generally a negative value expressed in dB.
3.2.4
same channel static crosstalk
static crosstalk, specified by the ratio of the channel power in the isolated port pair divided by
the channel power in the conducting port pair, when the input channel power in the isolated
port pair and the conducting port pair are the same
Note 1 to entry: Same channel static crosstalk is generally a negative value expressed in dB.
3.2.5
dynamic crosstalk
transient crosstalk
crosstalk attributed to both channel crosstalk (due to the same wavelength and/or other
wavelengths) and port isolation, predicted to change during the switching operation in the
WSS module
Note 1 to entry: Dynamic crosstalk is generally a negative value expressed in dB.
Note 2 to entry: Two types of dynamic crosstalk are defined: different channel dynamic crosstalk and same
channel dynamic crosstalk.
Note 3 to entry: Dynamic crosstalk is applied to 1 x N (N ≥ 3) WSSs.
[SOURCE: IEC 62343-3-3:2014, 3.15, modified — The term "dynamic crosstalk" has been
added as a first preferred term, and the note to entry has been replaced by three new notes.]
3.2.6
different channel dynamic crosstalk
optical power ratio of the isolated channel power divided by the conducting channel power in
the selected output port, when the input power of the conducting channel and the isolated
channel are the same
Note 1 to entry: Different channel dynamic crosstalk is generally a negative value expressed in dB.
Note 2 to entry: Signal leakage of the blue isolated channel in port 2 is the noise component for the red
conducting channel signal in port 2 for the demultiplexing WSSs shown in Figure 1 a).
Note 3 to entry: Different channel dynamic crosstalk is applied to 1 x N (N ≥ 3) WSSs.
3.2.7
same channel dynamic crosstalk
optical power ratio of the isolated channel power in the isolated port pair divided by the
conducting channel power in the conducting port pair, when the channel power in the input
port of the conducting port pair and the channel power in the input port of the isolated port
pair are the same
Note 1 to entry: Same channel dynamic crosstalk is applied to 1 x N (N ≥ 3) WSSs.
Note 2 to entry: Same channel dynamic crosstalk is generally a negative value expressed in dB.
Note 3 to entry: Red coloured signals in ports 1 and N are the noise components for the red signal in port 2, when
the conducting port pair for the blue signal is switched from port 1 to N in the multiplexing WSS shown in
Figure 1 b). All red signals in the isolated port pairs will be noise components. However, same channel dynamic
crosstalk is defined by the ratio of the optical loss between the conducting port pair and an isolated port pair.
Port 1
Port 1
Port 2
Port 2
Common
Port N
Common
port
port Port N
IEC
IEC
Noise observed in port during switching operation
a) Demultiplexing WSS b) Multiplexing WSS
Figure 1 – Noise observed in port during conducting port switching in 1 x N WSS
3.3 Abbreviated terms
ASE amplified spontaneous emission
DLP digital light processor
ITU-T International Telecommunication Union, Telecommunication Standardization Sector
LC liquid crystal
LCOS liquid crystal on silicon
LED light emitting diode
MEMS micro-electro-mechanical system
OE optical-to-electrical
OPM optical power meter
RBD reference branching device
TJ temporary joint
TLS tuneable laser source
WSS wavelength selective switch
– 10 – IEC 62343-5-2:2018 © IEC 2018
4 Apparatus
4.1 Test set-up
The test set-up consists of a light source, i.e. tuneable laser source (TLS) or broadband light
source, detector, i.e. optical power meter (OPM) or OE converter, and other equipment. An
example of the measurement set-up for measurement of the noise power to obtain the
dynamic crosstalk is given in Figure 2. The light of wavelength λ is input into the common port
of the WSS as a device under test (DUT) using TLS. Optical power, which is output from all
branching ports 1 to N, is measured simultaneously and continuously with a multi-port OPM
connected to each branching port. All apparatus are connected by the temporary joint (TJ). If
necessary, the wavelength meter with a reference branching device (RBD) may be used.
Power variation during switching of the the conducting port of the WSS is measured with the
OPM and recorded.
Figure 1 shows noise power that influences the different channel dynamic crosstalk is
generated in the case where the WSS is used as a demultiplexer, and noise power that
influences the same channel crosstalk is generated in the case where the WSS is used as a
multiplexer. However, optical noise power to measure both dynamic crosstalks is measured
with the test set-up shown in Figure 2, because the WSS is bidirectional.
In this test set-up, not only optical noise power in dynamic state but also optical noise power
in static state before and after switching the conducting port can be measured.
Port 1 to N
Common port
TJ2
Optical power meter
Wavelength: λ
Optical power meter
RBD TJ1
DUT
・・・
(WSS)
TLS
Optical power meter
Wavelength
meter
Data computation,
collection and
instrumentation
control
Electrical control and data interface
Optical connection
IEC
Figure 2 – Test set-up to measure dynamic crosstalk
4.2 Light source
4.2.1 Tuneable laser source (TLS)
The wavelength range of the TLS should be wider than the signal wavelength range of the
DUT. Optical output of the TLS should be more than 10 dB higher than the sum of the
minimum sensitivity of the optical detector, insertion loss of the test set-up [reference
branching device (RBD) and temporary joints (TJs)], insertion loss of the DUT and the
absolute value of measured dynamic crosstalk.
The side mode suppression ratio and signal to total source spontaneous emission ratio of the
TLS should be more than 10 dB higher than the absolute value of measured dynamic
crosstalk. For example, when the expected minimum value of dynamic crosstalk on the DUT is
–40 dB, the signal to total source spontaneous emission of the TLS should be more than
50 dB. When the signal to total source spontaneous emission ratio of the TLS is insufficient,
an appropriate tracking filter should be placed behind the TLS.
In the case of an ITU-T 50 GHz and 100 GHz fixed grid, the wavelength accuracy of the TLS
should be within ±10 pm and ±20 pm, respectively. When the wavelength accuracy is
insufficient, the output wavelength should be monitored by a wavelength meter and calibrated
when necessary.
The spectral width of the TLS should be narrow enough for the pass band of the WSS. Less
than 10 % of pass band is desirable.
In order to remove the influence of polarization dependent loss of the WSS, a polarization
scrambler shall be placed after the TLS. The polarization scrambler shall have a speed fast
enough (more than 10 times is desirable) than the averaging time of the detector.
4.2.2 Broadband light source and tuneable filter
A substitute system for the TLS is a test set-up that combines a broadband light source and
tuneable filter.
The broadband light source should be an LED or light source that is depolarized and has a
wide ASE spectrum. The spectrum of the light source should be wider than the signal
wavelength range of the DUT.
A tuneable filter is used to set the wavelength to be measured. The wavelength range of the
tuneable filter should be wider than the operating wavelength range of the DUT.
The accuracy of the centre wavelength of the tuneable filter should be within ±10 pm. The
tuneable filter has a pass band that is narrow enough compared to that of the WSS (less than
10 % of the pass band is desirable) and wavelength isolation of more than 50 dB between the
pass band and the stop band.
The optical output power generated by combining the broadband light source and tuneable
filter should be more than 10 dB higher than the sum of the minimum sensitivity of the optical
detector, insertion loss of the test set-up (RBD and TJs), insertion loss of the DUT and
absolute value of the measured dynamic crosstalk.
4.3 Device under test
The driving engine of the WSS is one of the following:
• one dimensional arrayed MEMS mirror that uses MEMS technology;
• two dimensional arrayed MEMS mirrors that use a digital light processor (DLP);
• one dimensional arrayed LC element that uses LC technology;
• two dimensional arrayed LCOS element;
• hybrid technology combining MEMS and LC.
There are two types of WSS: one that provides an electronic switching signal and the other
which does not. In the former case, the switching signal can be used as a synchronizing
(trigger) signal for the instrumentation. In the latter case, the optical output signal of the
output port can be used as an external trigger.
– 12 – IEC 62343-5-2:2018 © IEC 2018
4.4 Detector
4.4.1 Optical power meter (OPM)
The OPM should have more than two input channels that can be triggered simultaneously and
a wavelength range of the optical detector that is wider than the operating wavelength range
of the DUT.
Also, the OPM should have a minimum sensitivity that is more than 10 dB lower than the
value of removing the sum of the insertion loss of the test set-up (RBD and TJs), insertion
loss of the DUT and absolute value of the measured dynamic crosstalk from the optical output
of the light source. For example, when the optical power of the light source is 0 dBm, the
insertion loss of the set-up is 5 dB and the insertion loss of the WSS is 5 dB, the minimum
sensitivity of the OPM should be less than –60 dBm in order to make the measurement range
of dynamic crosstalk less than –40 dB.
When measuring noise power in a dynamic state, the OPM that has a measurement dynamic
range of more than 50 dB on a single range should be used because it is necessary to
measure continuously the variation of optical power of more than 40 dB, which is generated
within about one second. Generally, the OPM has a measurement dynamic range of about
30 dB on a single range.
Sometimes, when measuring variation of optical power that is larger than the measurement
dynamic range in a single range, the maximum value of noise power in the dynamic state
cannot be measured, because the switching measurement range needs about 100 ms.
Linearity of the OPM sensitivity influences the measurement uncertainty of dynamic crosstalk.
The averaging time should be set less than 25 μs when the OPM measures transient
response during switching of the conducting port of the WSS. It is desirable that the OPM has
sufficient memory length to acquire variation of noise power in the dynamic state and can
acquire data before and after switching the conducting port of the WSS automatically by
detecting the variation of optical power during switching of the conducting port with the
software function.
4.4.2 OE converter and oscilloscope
A substitute system for the OPM is equipment that combines an OE converter and an
oscilloscope.
The OE converter has a wider wavelength range than the operating signal wavelength range
of the DUT. The OE converter should have a minimum sensitivity that is more than 10 dB
lower than the value of removing the sum of insertion loss of the test set-up (RBD and TJs),
insertion loss of the WSS and absolute value of measured dynamic crosstalk from the optical
output of the light source.
The OE converter and oscilloscope should have enough high frequency response to measure
transient response during switching of the conducting port of the WSS. Frequency bandwidth
of more than 100 kHz is desirable.
Linearity of the OE converter sensitivity influences the measurement uncertainty of dynamic
crosstalk.
The oscilloscope should have more than two input channels that can be triggered
simultaneously and sufficient memory length to acquire variation of noise power in a dynamic
state.
When measuring the DUT of the output switching signal, it is desirable that the switching
signal is used as a trigger signal for the oscilloscope.
5 Measurement condition
5.1 General conditions
Measurement conditions of the optical power of noise terms in a dynamic state are as follows,
unless otherwise specified in the relevant specification.
a) Measurement environmental condition, input power, applied electric voltage and current
shall be within the specification defined by the DUT.
b) Measurement time resolution and measurement sampling points shall be determined by
the specification and device principle of the DUT, including port switching time, static
crosstalk and dynamic crosstalk.
c) Measurement conditions, including the spectral linewidth of the TLS and the wavelength
accuracy to ITU-T grid centre wavelength shall be determined by the specification and the
device principle of the DUT, including the spectral pass band.
d) The optical power of the noise at a branching port is measured in a dynamic state. It is a
combination from an initial state to a final state during port switching. Power is measured
in the channel of conducting port pairs determined by the port number of the DUT, the
ITU-T fixed grid channel spacing, channels and the channel frequency range.
5.2 Recommendations on selections of a branching port and channel
The noise measured at a branching port transitions from the initial state to the final state
during port switching. Optical power including the desirable optical power (signal) and the
undesirable optical power (noise) are measured at as many as possible conducting port pairs
to evaluate port and channel dependencies for dynamic crosstalk.
For example, in the case of a 1 x 9 WSS of C-band, ITU-T 100 GHz fixed grid 40 channels,
which are most commonly used in the industry, the possible combinations of conducting port
pairs and channels are 72 states in 2 ports from a selection of 9 ports and 1 560 states in
channels. Since the measurement of all of these states is not realistic in limited time, a
switching conducting port pair, branching port measured noise ports, and channels measured
optical powers at a conducting port pair and the other noise ports should be determined by
the following steps.
a) Two channels of a switching conducting port pair and noise ports should be selected to be
adjacent channels.
b) The adjacent channels should be maximum, minimum, and centre channels.
c) In a combination of a switching conducting port pair, maximum and minimum branching
ports (e.g. 1 x 9 WSS, a branching port 1 and port 9) should be selected with
consideration of the physical port configuration and internal optics. In the case where a
common port and all branching ports are aligned in a plane, a switching conducting port
pair should be selected so that large noise terms of dynamic crosstalk are detected.
6 Procedure
6.1 Preparation
Prepare OPMs or OE converters for the number of branching ports of the DUT. When the
temperature dependency is to be measured, the DUT shall be placed in the chamber. Connect
the optical input and output ports of the DUT to the measurement equipment with optical fibre.
Connect the electrical terminals of the power supply and control of the DUT to the
measurement equipment with electric cable. Measurement shall be started after the DUT is
turned on and the internal temperature of the DUT reaches a stable state. The DUT should be
turned on earlier than the warming-up time defined in the relevant specification, such as the
product specification.
– 14 – IEC 62343-5-2:2018 © IEC 2018
6.2 Measurement
6.2.1 Measurement of input power and insertion loss of DUT
Before measuring noise power during switching, measure the optical power launched into the
DUT and the insertion loss of the DUT. Measure the optical power for all channels where
dynamic crosstalk is to be measured. Measure the insertion loss by the method defined in
IEC 61300-3-29. Measure the insertion loss for all channels and all port pairs of the common
port and the branching port where the noise power is to be measured during switching. Notice
that the insertion loss of one port pair is different between channels.
6.2.2 Measurement of noise power for dynamic crosstalk
As shown in Figure 2, the common port shall be connected to the light source. Connect all
branching ports to OPMs or OE converters. The procedure for noise power measurement for
different channel crosstalk is explained in 6.2.3. The procedure for noise power measurement
for same channel crosstalk is explained in 6.2.4. Measure the noise power for intended
combinations of the following parameters:
– the branching port to be measured;
– the combination of branching ports before and after switching;
– the signal channel;
– the noise channel.
6.2.3 Measurement of noise power for different channel crosstalk
The measurement procedure is as follows.
a) All branching ports shall be set to the blocking state for all channels.
b) Input the optical signal of channel s to the common port, and connect the common port to
branching port i for channel s.
c) Switch the conducting port of the common port from branching port i to branching port j.
During this switching, measure the output power of channel s for all branching ports.
6.2.4 Measurement of noise power for same channel crosstalk
The measurement procedure is as follows.
a) All branching ports shall be set to the blocking state for all channels.
b) Input the optical signal of channel r (with the frequency of f ) to the common port.
r
c) Switch the conducting port of the common port from branching port i to branching port j for
channel s (with the frequency of f , s ≠ r). During this switching, measure the output power
s
of channel r for all branching ports.
Although channel r may be selected from (channel number – 1) choices other than channel s,
the maximum crosstalk is generally measured when channel r is adjacent to channel s.
Therefore, as explained in 5.2, channel r should be selected to satisfy the following conditions
in accordance with the fixed grid of the DUT defined in the product specification:
– f = f ± 100 GHz for an ITU-T 100 GHz-fixed grid;
r s
– f = f ± 50 GHz for an ITU-T 50 GHz-fixed grid.
r s
7 Example of transient characteristics of noise power
An example of transient characteristics of noise power is shown in Figure 3 for different
channel crosstalk and Figure 4 for same channel crosstalk.
NOTE IEC TR 62343-6-9 describes the measurement results of dynamic crosstalk for WSSs.
Figure 3 shows the optical power changing of channel s for branching port i, branching port j
and branching port k, when the signal of channel s is incident on the common port, and the
conducting port of the common port is switched from branching port i to branching port j for
channel s. The two vertical dotted lines are the starting time and the completion time of
switching, respectively. The time before the starting time and after the completion time of
switching is in static state; from the starting time to completion time it is in dynamic state. The
subscript "i", the superscript "s" and the superscript "(s:i,j)" indicate the branching port, the
channel of measurement, and switching the conducting port from the branching port i to the
branching port j for the channel s, respectively. The optical power from the branching port i
s,(s:i,j)
before switching P (t) (t ≤ t1) is not equal to the optical power from branching port j after
i
s,(s:i,j)
switching P (t) (t ≥ t2), because the insertion losses are different for the port pair, where,
j
t1 and t2 show the starting time and the completion time for measurement.
The leakage power of channel s to the branching port is the noise power related to different
channel crosstalk. Branching port 1, branching port 2 and branching port N in Figure 1 a)
correspond to branching port i, branching port k and branching port j, respectively. The blue
channel and the red channel in Figure 1 a) correspond to channel s and channel r,
respectively. As the power for channel s is the noise of the signal power for channel r for
branching port k, crosstalk is expressed as the difference between the noise power for the
r
channel s, and the insertion loss between the common port and branching port k, IL . In
k
Figure 3, crosstalk is expressed as the difference between the noise power for channel s,
s,(s:i,j) s
P (t) and the subtraction of the incident power for channel s to the common port P from
k
r s r
the insertion loss IL , P－IL , as the vertical axis is the optical power.
k k
s,(s:i,j)
The maximum different
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