IEC TR 62343-6-9:2015

IEC TR 62343-6-9 ®
Edition 1.0 2015-06
TECHNICAL
REPORT
colour
inside
Dynamic modules –
Part 6-9: Design guide – Study of mechanisms and measurements of crosstalk
in wavelength-selective switches

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IEC TR 62343-6-9 ®
Edition 1.0 2015-06
TECHNICAL
REPORT
colour
inside
Dynamic modules –
Part 6-9: Design guide – Study of mechanisms and measurements of crosstalk

in wavelength-selective switches

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.180.01; 33.180.99 ISBN 978-2-8322-2769-5

– 2 – IEC TR 62343-6-9:2015 © IEC 2015
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references. 7
3 Abbreviations . 7
4 Study of dynamic crosstalk for WSS . 8
4.1 Static crosstalk and dynamic crosstalk . 8
4.2 Generation mechanism of dynamic crosstalk . 8
4.2.1 Configuration example of optical switching functionality . 8
4.2.2 Generation mechanism . 9
5 Measurement methods of dynamic crosstalk . 11
5.1 Study of measurement methods of dynamic crosstalk . 11
5.1.1 Referenced standard documents . 11
5.1.2 Test configuration of tuneable laser source (TLS) and optical power
meter . 12
5.1.3 Test configuration of tuneable laser source, OE converter and
oscilloscope . 12
5.1.4 Comparison of the measurement methods . 13
5.2 Evaluation of the measurement methods. 13
6 Measurement result of dynamic crosstalk . 14
6.1 MEMS type WSS . 14
6.1.1 Measurement conditions . 14
6.1.2 Measurement of different-channel crosstalk . 14
6.1.3 Measurement of same-channel crosstalk . 15
6.2 LCOS type WSS . 16
6.2.1 Measurement conditions . 16
6.2.2 Measurement of different-channel crosstalk . 17
6.2.3 Measurement of same-channel crosstalk . 17
6.3 DLP type WSS . 18
6.3.1 Measurement conditions . 18
6.3.2 Measurement procedure and result. 18
6.4 Summary . 20
7 Conclusion . 21
Bibliography . 22

Figure 1 – Block diagram of optical switching function . 9
Figure 2 – Dynamic crosstalk at WSS . 10
Figure 3 – Dynamic crosstalk at optical coupler for multiplexing . 11
Figure 4 – Dynamic crosstalk at receiver (Rx) . 11
Figure 5 – Test configuration of tuneable laser source (TLS) and optical power meter . 12
Figure 6 – Test configuration of tuneable laser source and oscilloscope . 13
Figure 7 – Experimental set-up . 14
Figure 8 – Measurement set-up of different-channel crosstalk . 15

Figure 9 – Measurement result of different-channel crosstalk for MEMS type WSS . 15
Figure 10 – Measurement result of same-channel crosstalk for MEMS type WSS . 16
Figure 11 – Measurement result of different-channel crosstalk for LCOS type WSS . 17
Figure 12 – Measurement result of same-channel crosstalk for LCOS type WSS . 18
Figure 13 – Switching characteristics for 1 × 2 DLP type WSS . 19
Figure 14 – Crosstalk measurement result of case a) for DLP type WSS . 19
Figure 15 – Crosstalk measurement result of case b) for DLP type WSS . 20
Figure 16 – Crosstalk measurement result of case c) for DLP type WSS . 20

Table 1 – Static crosstalk and dynamic crosstalk . 8
Table 2 – Same-channel crosstalk and different-channel crosstalk . 8
Table 3 – Generating mechanism of same-channel crosstalk and different-channel
crosstalk . 10

– 4 – IEC TR 62343-6-9:2015 © IEC 2015
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DYNAMIC MODULES –
Part 6-9: Design guide – Study of mechanisms and
measurements of crosstalk in wavelength-selective switches

FOREWORD
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example "state of the art".
IEC TR 62343-6-9, which is a Technical Report, has been prepared by subcommittee SC86C:
Fibre optic systems and active devices, of IEC technical committee TC 86: Fibre optics.
The text of this Technical Report is based on the following documents:
Enquiry draft Report on voting
86C/1300/DTR 86C/1321/RVC
Full information on the voting for the approval of this Technical Report 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.
A list of all parts in the IEC 62343 series, published under the general title Dynamic modules,
can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website 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.
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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
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colour printer.
– 6 – IEC TR 62343-6-9:2015 © IEC 2015
INTRODUCTION
A dense wavelength division multiplexing (DWDM) system for fibre optic communication was
developed in the late 1990’s. The first generation DWDM systems were point-to-point optical
networks. In the mid-2000’s, second generation DWDM systems, typically ring networks, were
developed. One of the key optical components for DWDM systems is a wavelength division
multiplexing device. An AWG (arrayed waveguide grating) module has been mainly deployed
for first and second generation DWDM systems.
Due to the increasing demand for communication capacity, more flexible optical
communication systems, such as mesh networks, have been required. In the past several
years, the third generation of DWDM systems, the optical cross-connect system, has been
developed and deployed by some communication network carriers and is expected to be
deployed worldwide. A wavelength-selective switch (WSS) module plays a key role in
realizing the optical switch function in the optical cross-connect system, so that the
performance of the WSS directly impacts on the performance of the optical cross-connect
systems, such as the capacity, transmission distance, etc.
For AWG modules, only static performance, such as insertion loss, bandwidth, pass-band
ripple, polarization dependent loss (PDL), polarization mode dispersion (PMD), coherent
crosstalk, etc., has been evaluated. In addition to static performance, dynamic performance
during switching or changing attenuation should be taken into consideration for the WSS as a
key module of optical cross-connect systems.
For dynamic performance parameters, the influence not only on the controlled channel but
also on other channels should be considered.
Considering this background, the influence of WSS dynamic crosstalk on cross-connect
system performance and the measurements of dynamic crosstalk has been demonstrated.
This Technical Report is based on Optoelectronic Industry and Technology Development
Association (OITDA) – Technical Paper (TP), TP15/TP-2013, "Dynamic crosstalk
measurement for wavelength selective switches”.

DYNAMIC MODULES –
Part 6-9: Design guide – Study of mechanisms and
measurements of crosstalk in wavelength-selective switches

1 Scope
This part of IEC 62343, which is a Technical Report, describes a study of the impact of WSS
dynamic crosstalk on the optical network and includes dynamic crosstalk measurement
examples for three types of WSS. The generating mechanism and the generation factor of
dynamic crosstalk in WSS are clarified, and the evaluation of same-channel crosstalk and
different-channel crosstalk is shown to be necessary.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 61300-3-21, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 3-21: Examinations and measurements – Switching time
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
3 Abbreviations
ADD add port
AWG arrayed waveguide grating
COM common port
CW continuous wave
DLP digital light processor
DRP drop port
DUT device under test
DWDM dense wavelength division multiplexing
EXP express port
LCOS liquid crystal on silicon
MEMS micro electro mechanical system
OE optical-to-electrical
PDL polarization dependent loss
PMD polarization mode dispersion
TLS tuneable laser source
Tx transmitter
Rx receiver
WSS wavelength selective switch

– 8 – IEC TR 62343-6-9:2015 © IEC 2015
4 Study of dynamic crosstalk for WSS
4.1 Static crosstalk and dynamic crosstalk
WSSs can be considered as the combination of optical spatial switches, variable optical
attenuators, and DWDM devices such as AWG modules. For the WSS, dynamic crosstalk,
which is the interference between ports and channels during switching and changing
attenuation, is generated in addition to static crosstalk.
Static crosstalk has been studied, and the definition and standard measurement methods for
WDM devices such as AWG modules have been established. In addition to static crosstalk,
dynamic crosstalk for WSSs has to be considered because WSSs vary attenuation and switch
ports during operation.
Two types of dynamic crosstalk are considered in this Technical Report: same-channel
crosstalk (coherent crosstalk), and different-channel crosstalk (power crosstalk). In this sense,
the word of channel refers to the signal at a particular wavelength.
The impact on signal quality of same-channel crosstalk to cross-connect systems is
considered to be larger than that of different-channel crosstalk, which may be negligible.
The classification of dynamic crosstalk and static crosstalk and that of same-channel
crosstalk and different-channel crosstalk are independent. Therefore, four combinations
(dynamic-same-channel crosstalk, dynamic-different-channel crosstalk, static-same-channel
crosstalk, and static-different-channel crosstalk) have to be considered.
Table 1 and Table 2 show the features of static and dynamic crosstalk and same-channel and
different-channel crosstalk, respectively.
Table 1 – Static crosstalk and dynamic crosstalk
Crosstalk Description
Static crosstalk Crosstalk generated during static state, that is without switching ports or
changing attenuations
Dynamic crosstalk Crosstalk generated during dynamic state, such as switching ports and changing
attenuations
Table 2 – Same-channel crosstalk and different-channel crosstalk
Crosstalk Description
Same-channel crosstalk Crosstalk between same channels. The impact to the cross-connect systems is
larger than that of different-channel crosstalk.
Different-channel crosstalk Crosstalk between different channels. The impact to the cross-connect systems
is smaller than that of same-channel crosstalk.

4.2 Generation mechanism of dynamic crosstalk
4.2.1 Configuration example of optical switching functionality
Figure 1 shows an example block diagram of optical switching functionality in optical mesh
networks. This node is known as a route and select topology, since incoming data are first
routed by the ingress WSS to its correct optical path, where an egress WSS selects the
correct data from all its input ports before multiplexing and passing into the transmission fibre.
This example configuration of a switching functionality is composed of four WSSs. Using
multichannel WSSs, the number of switching optical ports can be increased and can realize
cross-connect systems having many paths. Each WSS is connected to each transmission line

through WDM IN and WDM OUT ports, and the number of WSS pairs is equal to the number
of transmission paths.
Data in the form of DWDM signals are applied to the switching node from th
...