IEC 61300-3-50:2013

IEC 61300-3-50 ®
Edition 1.0 2013-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures –
Part 3-50: Examinations and measurements – Crosstalk for optical spatial
switches
Dispositifs d’interconnexion et composants passifs à fibres optiques –
Procédures fondamentales d’essais et de mesures –
Partie 3-50: Examens et mesures – Diaphonie relative aux commutateurs
spatiaux optiques
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IEC 61300-3-50 ®
Edition 1.0 2013-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fibre optic interconnecting devices and passive components – Basic test and

measurement procedures –
Part 3-50: Examinations and measurements – Crosstalk for optical spatial

switches
Dispositifs d’interconnexion et composants passifs à fibres optiques –

Procédures fondamentales d’essais et de mesures –

Partie 3-50: Examens et mesures – Diaphonie relative aux commutateurs

spatiaux optiques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX M
ICS 33.180.20 ISBN 978-2-83220-795-6

– 2 – 61300-3-50 © IEC:2013
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 General description . 5
4 Apparatus . 6
4.1 Light source S . 6
4.2 Temporary joint TJ . 7
4.3 Terminations T . 7
4.4 Detector D . 7
5 Measurement procedure . 7
5.1 General . 7
5.2 Test set-up . 7
5.3 Measurement of P . 8
5.4 Measurement of P . 8
5.5 Measurement of P (i=3 to N) . 9
i
5.6 Measurement for other input ports . 9
6 Calculation . 9
6.1 Calculation of crosstalk for specified port pairs . 9
6.2 Calculation of total crosstalk for a specified output port . 10
6.3 Crosstalk of M x N fibre optic switch . 10
6.4 Total crosstalk of M x N fibre optic switch . 10
7 Details to be specified . 10
7.1 Light source . 10
7.2 Temporary joint . 11
7.3 Terminations . 11
7.4 Detector . 11
7.5 DUT . 11
7.6 Others . 11
Bibliography . 12

Figure 1 – Crosstalk for N x 1 optical switch . 6
Figure 2 – Measurement set-up of crosstalk for 1 x N optical switch . 6
Figure 3 – Measurement setup of P . 8
Figure 4 – Measurement set-up of P . 9
61300-3-50 © IEC:2013 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTIC INTERCONNECTING
DEVICES AND PASSIVE COMPONENTS –
BASIC TEST AND MEASUREMENT PROCEDURES –

Part 3-50: Examinations and measurements –
Crosstalk for optical spatial switches

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 61300-3-50 has been prepared by subcommittee 86B: Fibre optic
interconnecting devices and passive components, of IEC technical committee 86: Fibre optics.
The text of this standard is based on the following documents:
FDIS Report on voting
86B/3593/FDIS 86B/3622/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 4 – 61300-3-50 © IEC:2013
A list of all parts in the IEC 61300 series, published under the general title, Fibre optic
interconnecting devices and passive components – Basic test and measurement procedures
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 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.
The contents of the corrigenda 1 (January 2015) and 2 (July 2015) have been included in
this copy.
61300-3-50 © IEC:2013 – 5 –
FIBRE OPTIC INTERCONNECTING
DEVICES AND PASSIVE COMPONENTS –
BASIC TEST AND MEASUREMENT PROCEDURES –

Part 3-50: Examinations and measurements –
Crosstalk for optical spatial switches

1 Scope
This part of IEC 61300 describes the procedure to measure the crosstalk of optical signals
between the ports of a multiport M x N (M input ports and N output ports) fibre optic spatial
switch. The crosstalk is defined as the ratio of the optical power at an output port which
comes from the unconnected input port, to the optical power at the output port which comes
from the connected input port.
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 61300-1, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 1: General and guidance
IEC 61300-3-2, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-2: Examinations and measurements – Polarization
dependent loss in a single-mode fibre optic device
3 General description
The general meaning of crosstalk is the ratio of an undesired signal power to a desired signal
power. The crosstalk of N x 1 (N input ports and one output port) fibre optic spatial switches is
shown in Figure 1. For an N x M (N input ports and M output ports) fibre optic switch, the
crosstalk is the same as that for an N x 1 optical switch but expanded across M output ports.
A fibre optic switch is basically bidirectional, i.e. a 1 x N (1 input port and N output ports)
optical switches can operate as an N x 1 (N input ports and 1 output port) switch. The
crosstalk for an N x 1 optical switch is measured as a 1 x N optical switch, as shown in
Figure 2. When the input port for a 1 x N optical switch is connected to a light source, the
crosstalk for a transmitting output port versus an isolated output port is the ratio of output
power of these two output ports, expressed in decibels. Crosstalk is a negative value in dB.
Do not use “isolation” in place of “crosstalk” as the two have a different values and meanings.
The meaning of isolation is the optical loss for a port pair intended to block transmission, i.e.
for which loss is nominally infinite. Isolation is a positive value in dB. Crosstalk is a negative
value in dB.
NOTE 1 For WDM devices, crosstalk is defined as the value of the ratio between the optical power of the
specified signal and all noise, as defined in IEC 62074-1 [1] . The crosstalk for WDM devices is generally used as
_____________
Numbers in square brackets refer to the Bibliography.

– 6 – 61300-3-50 © IEC:2013
not simply “crosstalk”, but “some prefix” crosstalk, such as adjacent channel crosstalk, total crosstalk and so on.
The measurement method of crosstalk for DWDM devices are described in IEC 61300-3-29 [2].

Port 1 (signal 1)
Common port (signal 1, and
Port 2 (signal 2)
the sum of signals (2 ~ n) as noise)

Port n (signal n)
N × 1 optical switch
IEC  959/13
Figure 1 – Crosstalk for N x 1 optical switch

Port 1 (transmitting port) Optical

detector 1
Port 2 (isolated port) .
Light
.
source
.
Port n (isolated port)
Optical
detector n
1 × N optical switch
IEC  960/13
Figure 2 – Measurement set-up of crosstalk for 1 x N optical switch
For single mode fibre optic switches, the crosstalk may depend on the polarization state of the
input light. A polarization state change system (PSCS; a polarization controller or a
polarization scrambler) should be used with a light source. In this case, the crosstalk is
generally defined as the maximum value of the measured crosstalk for all polarization states
of the input light. For multi-mode fibre optic switches, the launch mode of input light shall be
in accordance with IEC 61300-1.
Since, in practice the crosstalk levels of fibre optic switches can be very small, (of the order of
under –70 dB), the measurement can be degraded by several factors. Therefore, this
procedure is designed to either circumvent these factors, or to point them out so that
adequate care can be taken and the right choice of test apparatus made. Factors which can
degrade a measurement of crosstalk include:
– the coupling of ambient light into measurement channels;
– the reflection of light from the ends of fibre pigtails;
– the light carried in cladding modes;
– the uncertainty of the power meter at low light levels;
– the fibre pigtail lengths since light can scatter (Rayleigh scattering) along the pigtails.
4 Apparatus
4.1 Light source S
The light source is pigtailed or connected to a launch optical fibre compatible with the input
port of the device under test (DUT). It is also designed and conditioned to achieve the
required launch conditions as stated in IEC 61300-1. For measurements of DUTs which are
not inherently broadband in optical performance, the spectral output of the light source shall
be characterized not only in the vicinity of the operating wavelength range by means of full

61300-3-50 © IEC:2013 – 7 –
width at half maximum (FWHM) but also in the region of the spectral tail. This requirement
can be specified as "power less than X dB below peak at wavelengths Y nm from peak output"
and can be achieved by use of in-line bandpass filters. The output power of the light source
shall also be sufficiently high to permit a large measurement dynamic range with the optical
detector used. The output power stability shall be less than or equal to 0,05 dB per hour. The
dynamic range of the source/detector combination shall be at least 10 dB greater than the
absolute value of the minimum crosstalk to be measured.
For the measurement of single mode fibre optic switches, the polarization dependency of
crosstalk shall be considered. A polarization controller is used to measure the polarization
dependency of crosstalk. The detail requirement of a PSCS is described in IEC 61300-3-2.
The launch condition, power stability and dynamic range shall satisfy the requirement as
mentioned above for the output power of a PSCS when a PSCS is used.
4.2 Temporary joint TJ
This is a method, device or mechanical fixture for temporarily aligning two fibre ends into a
reproducible, low loss joint and polarization independent splicing. Typically, a fusion splice is
used since mechanical splices may exhibit some polarization sensitivity if the endfaces are
not perpendicular to the fibre axis. The stability of the temporary joint shall be compatible with
the required measurement precision.
4.3 Terminations T
These terminations are components or techniques to suppress reflected light from the DUT
output ports. Three types of terminations are suggested:
– angled fibre ends;
– the application of an index matching material to the fibre end;
– attenuation of the fibre, for example with a mandrel wrap.
The fibre termination shall have a return loss of at least 10 dB greater than the absolute value
of the minimum crosstalk to be measured.
4.4 Detector D
A high dynamic range optical power meter should be used for the detector. Its wavelength
range shall be wider than the operating wavelength range of the DUT. The linearity of
sensitivity of the detector shall be small enough to minimize the measurement uncertainty.
The detector shall have a sufficiently large detection area and be placed sufficiently close to
the output to capture all of the light emitting from the output fibre of the DUT to be measured.
5 Measurement procedure
5.1 General
This clause describes the measurement procedure of crosstalk for M x N (M input ports and N
output ports) fibre optic switches.
5.2 Test set-up
Figure 3 shows the test set-up for crosstalk measurement. The light source is connected to
the selected input port (I1) of the DUT by means of a TJ where appropriate or by means of a
connector in the case of a DUT fitted with a connector. The detector is connected to a
transmitting output port of the DUT (port O1) which is to be measured for crosstalk against
another chosen output port nominally isolated from the previous one (port O2). All other ports
of the DUT are terminated (T).

– 8 – 61300-3-50 © IEC:2013
TJ
P
in Port I1
Port O1
S D
P
Port O2
DUT
T T
T T
M Inputs
N Outputs
IE
C
Figure 3 – Measurement setup of P
5.3 Measurement of P
Turn on the light source S and allow sufficient time for it to stabilize. Switch the fibre optic
spatial switch DUT to connect between the selected input port and the transmitting output port
(port O1). Measure and record P (dBm).
When a PSCS is used with a light source for measuring single mode fibre optic spatial
switches, change the polarization states of the input light in accordance with IEC 61300-3-2.
Both the “all polarization state” method and Mueller matrix method may be used. P in
Figure 3 changes depending on the state of polarization, from P to P . Use P as
1min 1max 1max
P .
5.4 Measurement of P
Move the detector D to port O2 which is the nominally isolated port for the selected input port
as shown in Figure 4. Terminate port O1, ensuring that this port is still linked to the input port
of the DUT. For the fibre optic switch DUT, this means ensure it is connected to port O1.
Measure and record the output power from port O2 as P (dBm).
When a PSCS is used with a light source for measuring single mode fibre optic spatial
switches, change the polarization states of the input light in accordance with IEC 61300-3-2.
Both the “all polarization state” method and Mueller matrix method may be used. P in
Figure 4 changes depending on the state of polarization, from P to P . Use P as
2min 2max 2min
P .
61300-3-50 © IEC:2013 – 9 –
TJ
P
in
Port I1
S Port O1 T
DUT Port O2
P
T D
T T
M Inputs
N Outputs
IEC
Figure 4 – Measurement setup of P
5.5 Measurement of P (i=3 to N)
i
Repeat the procedure of 5.4 for the output port O1, to measure P (dBm) and record, i = 3 to N.
i
5.6 Measurement for other input ports
Change the connection of light source S to another input port Ij (j = 2 to M). Repeat the
procedure of 5.2 to 5.5.
6 Calculation
6.1 Calculation of crosstalk for specified port pairs
The crosstalk (XT ) for the pairs for port O1 to port I1 and port O2 to port I1 is given by
Equation (1):
XT = P – P (dB) (1)
2 1
This crosstalk is the crosstalk of signal light 1 with signal light 2 as noise for signal light 1 for
output port O1, when this DUT is used for M x N (M input ports and N output ports),
connected port I1 to port O1 and input signal light 1 from port O1, signal light 2 from port O2.
For single mode fibre optic spatial switches, the polarization dependency of crosstalk shall be
considered. In this case, the crosstalk (XT) is calculated by using Equation (2):
XT = IL – IL (2)
12 max,11 min,12
where
IL is the minimum insertion loss for input port 1 to output port 2;
min,12
IL is the maximum insertion loss for input port 1 to output port 1
max,11
when input port 1 is connected to output port 1.
The minimum and maximum insertion loss is calculated from the average insertion loss (IL )
ave
and PDL as Equations (3) and (4):

– 10 – 61300-3-50 © IEC:2013
IL = IL – PDL/2 (3)
min ave
IL = IL + PDL/2 (4)
max ave
P shall be the maximum value of the power for all polarization states of input light, and P
2 1
shall be the minimum value of the power for all polarization states of input light.
6.2 Calculation of total crosstalk for a specified output port
The total crosstalk is the ratio of the total noise (total power of leakage from unconnected
(O1) of the
ports) to the desired signal power from the connected port. The total crosstalk XT
tot
output port of port O1, in case of connecting port I1 and port O1, for the M x N fibre optic
switch of this DUT is given by Equation (5), which is the expansion of Equation (1):
 
i =N
P
i
 
XT (O ) = 10 log 10 − P
tot 1 10 1

 
(5)
 
i =2
 
where P is given in 5.5.
i
For single mode fibre optic spatial switches, the total crosstalk XT (O1) of the output port of
tot
port O1, in the case of connecting port I1 and port O1, for the M x N fibre optic switch is
calculated by using Equation (6), which is the expansion of Equation (2):
 
i =N
− IL
min,1i
 
XT (O ) = IL + 10 log 10
tot 1 max,11 10
 
(6)
 
i =2
 
where
IL is the minimum insertion loss for input port 1 to output port I when input port 1 is
min,1i
connected to output port 1.
In the case where an N x 1 spatial optical switch is used for selecting a port from N input ports
(see Figure 1), all of the optical power from unconnected input ports is noise. For system
suppliers, total crosstalk is necessary to estimate the influence on transmission performance,
especially OSNR.
6.3 Crosstalk of M x N fibre optic switch
The crosstalk of an M x N fibre optic switch is defined as the maximum crosstalk for all
combination of port pairs, calculated using Equation (1).
6.4 Total crosstalk of M x N fibre optic switch
The total crosstalk of an M x N fibre optic switch is defined as the maximum total crosstalk for
all output ports and all switching connecting port pairs, calculated using Equation (6).
7 Details to be specified
The following details, as applicable, shall be specified in the relevant specification and/or
recorded in the measurement report:

61300-3-50 © IEC:2013 – 11 –
7.1 Light source
– Type of light source
– Centre wavelength
– Spectral width
– Output power
– Power stability during measurement
– Type of PSCS and measurement method of polarization dependency (when used)
– Type of mode filter and launch condition (when used)
7.2 Temporary joint
– Type of temporary joint
– Return loss of temporary joint
– Insertion loss of temporary joint
7.3 Terminations
– Type of terminations
– Return loss of terminations
7.4 Detector
– Type of detector
– Dynamic range of sensitivity
– Linearity of sensitivity
– Polarization dependency of sensitivity
7.5 DUT
– Input/output port combinations of the DUT to be measured
– Performance requirements for crosstalk for each speci
...