IEC 62074-1:2025

IEC 62074-1 ®
Edition 3.0 2025-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fibre optic interconnecting devices and passive components - Fibre optic WDM
devices -
Part 1: Generic specification
Dispositifs d’interconnexion et composants passifs fibroniques - Dispositifs
MRL fibroniques -
Partie 1: Spécification générique
ICS 33.180.01, 33.180.20 ISBN 978-2-8327-0497-4

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CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
3.1 Device terms . 7
3.2 Performance terms . 8
4 Requirements . 25
4.1 Classification . 25
4.1.1 General. 25
4.1.2 Technology . 26
4.1.3 Port configuration . 26
4.1.4 Wavelength (channel) spacing . 26
4.1.5 Internal structure . 26
4.1.6 Wavelength band . 27
4.1.7 Temperature control . 27
4.1.8 Interface style . 27
4.2 Documentation . 27
4.2.1 Symbols . 27
4.2.2 Drawings . 27
4.2.3 Tests and measurements . 27
4.2.4 Test report . 28
4.2.5 Instructions for use . 28
4.3 Standardisation system . 28
4.3.1 Interface standards . 28
4.3.2 Performance standards. 28
4.3.3 Reliability standards . 28
4.4 Design and construction . 28
4.4.1 Materials . 28
4.4.2 Workmanship . 29
4.5 Quality . 29
4.6 Performance requirements . 29
4.7 Identification and marking . 29
4.7.1 General. 29
4.7.2 Device marking . 29
4.7.3 Package marking . 29
4.8 Packaging . 30
4.9 Storage conditions . 30
4.10 Safety. 30
Annex A (informative) Transfer matrix . 31
A.1 General . 31
A.2 Transfer matrix . 31
A.3 Transfer matrix coefficient . 32
A.4 Logarithmic transfer matrix . 32
Annex B (informative) Specific performances of WDM devices for bidirectional
transmission system (example) . 34
B.1 Generic . 34
B.2 Definition of near-end isolation and near-end crosstalk . 35
Annex C (informative) Transfer matrix as applications of WDM devices (example) . 36
C.1 Generic . 36
C.2 Wavelength multiplexer . 36
C.3 Wavelength demultiplexer . 37
C.4 Wavelength multiplexer/demultiplexer . 38
C.5 Wavelength router . 39
C.6 Wavelength channel add/drop . 40
Annex D (informative) Example of technology of thin film filter WDM devices . 42
D.1 General . 42
D.2 Thin film filter technology. 42
D.3 Typical characteristics of thin film filter . 43
Annex E (informative) Example of technology of fibre fused WDM devices . 44
E.1 General . 44
E.2 Typical characteristics of fibre fused WDM devices . 45
Annex F (informative) Example of arrayed waveguide grating (AWG) technology . 46
F.1 General . 46
F.2 Typical characteristics of AWG . 46
Annex G (informative) Example of FBG filter technology . 48
G.1 General . 48
G.2 Typical characteristics of FBG filter . 49
Annex H (informative) Example of interface style . 50
Bibliography . 51

Figure 1 – Illustration of channel wavelength range . 9
Figure 2 – Illustration of insertion loss . 10
Figure 3 – Illustration of ripple . 10
Figure 4 – Illustration of channel insertion loss variation . 11
Figure 5 – Illustration of isolation wavelength . 12
Figure 6 – Illustration of isolation wavelength range . 13
Figure 7 – Illustration of adjacent channel isolation . 14
Figure 8 – Illustration of non-adjacent channel isolation. 15
Figure 9 – Illustration of maximum adjacent channel crosstalk. 16
Figure 10 – Illustration of maximum non-adjacent channel crosstalk . 17
Figure 11 – Illustration of a four-wavelength bidirectional system . 20
Figure 12 – Illustration of channel extinction ratio . 21
Figure 13 – Illustration of free spectral range . 22
Figure 14 – Illustration of polarization dependent centre wavelength (PDCW) . 23
Figure 15 – Illustration of X dB bandwidth . 25
Figure A.1 – Example of a six-port device, with two input and four output ports . 31
Figure A.2 – Illustration of transfer matrix coefficient . 32
Figure B.1 – Uni-directional and bi-directional transmission system application of a
1 × 2 WDM device . 34
Figure C.1 – Example of a wavelength multiplexer . 36
Figure C.2 – Example of a wavelength demultiplexer. 37
Figure C.3 – Example of a wavelength multiplexer/demultiplexer . 38
Figure C.4 – Example of a wavelength router . 39
Figure C.5 – Example of wavelength channel add/drop . 40
Figure D.1 – Schematic configuration of a thin film filter WDM device . 42
Figure D.2 – Structure of multilayer thin film . 43
Figure D.3 – Typical characteristics of 1 510 nm and C-band WDM device using thin
film filter technology. 43
Figure E.1 – Structure of a fused bi-conical tapered 2x2 coupler . 44
Figure E.2 – Typical scheme for a fused coupler . 45
Figure E.3 – Typical characteristics of a fibre fused WDM device . 45
Figure F.1 – Basic configuration of AWG. 46
Figure F.2 – Example of AWG characteristics . 47
Figure G.1 – Usage of fibre Bragg grating filter . 48
Figure G.2 – Function and mechanism of fibre Bragg grating . 48
Figure G.3 – Example of FBG filter characteristics . 49
Figure H.1 – Example of interface style for WDM devices . 50

Table 1 – Example of a typical fibre optic WDM device classification . 26

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Fibre optic interconnecting devices and passive components -
Fibre optic WDM devices -
Part 1: Generic specification
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
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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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
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shall not be held responsible for identifying any or all such patent rights.
IEC 62074-1 has been prepared by subcommittee SC 86B: Fibre optic interconnecting devices
and passive components, of IEC technical committee 86: Fibre optics. It is an International
Standard.
This third edition cancels and replaces the second edition published in 2014. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) harmonization of terms and definitions with IEC TS 62627-09;
b) simplified classification, documentation and standardization system in Clause 4, and moving
interface style to Annex H.
The text of this International Standard is based on the following documents:
Draft Report on voting
86B/5031/FDIS 86B/5074/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 62074 series, published under the general title Fibre optic
interconnecting devices and passive components – Fibre optic WDM devices, can be found on
the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
1 Scope
This part of IEC 62074 applies to fibre optic wavelength division multiplexing (WDM) devices.
These have all of the following general features:
• they are passive, in that they contain no optoelectronic or other transducing elements;
however they can use temperature control only to stabilize the device characteristics; they
exclude any optical switching functions;
• they have three or more ports for either the entry or exit of optical power, or both, and share
optical power among these ports in a predetermined fashion depending on the wavelength;
• the ports are optical fibres, or optical fibre connectors.
This document establishes uniform requirements for the following:
• optical, mechanical and environmental properties.
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 60050-731, International Electrotechnical Vocabulary (IEV) – Part 731: Optical fibre
communication (available at www.electropedia.org)
61300 (all parts), Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures
IEC 61753 (all parts), Fibre optic interconnecting devices and passive components -
Performance standard
IEC 62005 (all parts), Reliability of fibre optic interconnecting devices and passive components
IEC TS 62627-09:2016, Fibre optic interconnecting devices and passive components –
Vocabulary for passive optical devices
ISO 129-1, Technical product documentation (TPD) — Presentation of dimensions and
tolerances – Part 1: General principles
ISO 286-1, Geometrical product specifications (GPS) – ISO code system for tolerances on
linear sizes – Part 1: Basis of tolerances, deviations and fits
ISO 1101, Geometrical product specifications (GPS) – Geometrical tolerancing – Tolerances of
form, orientation, location and run-out
ISO 8601-1, Date and time – Representations for information interchange – Part 1: Basic rules
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-731 and
IEC TS 62627-09 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1 Device terms
3.1.1
wavelength-selective branching device
passive device with three or more ports that shares optical power among its ports in a
predetermined fashion, only depending on the wavelength, in the sense that at least two
different wavelength ranges are nominally transferred between two different pairs of ports
[SOURCE: IEC TS 62627-09:2016, 3.3.12, modified – “wavelength multiplexer” and
“wavelength demultiplexer” have been removed from the term, and in the definition “optical
device (component)” has been replaced with “device”, “without any amplification or other active
modulation but” has been removed.]
3.1.2
wavelength division multiplexing device
wavelength division multiplexer
WDM device
wavelength-selective branching device
Note 1 to entry: The term of wavelength-selective device is the contrast with the term of non-wavelength-selective
branching device. The term of WDM device is frequently used.
3.1.3
DWDM device
dense wavelength division multiplexing device
WDM device which is intended to operate for a channel spacing ≤ 1 000 GHz
Note 1 to entry: The channel spacing is approximately 8 nm at 1 550 nm and 5,7 nm at 1 310 nm.
3.1.4
CWDM device
coarse wavelength division multiplexing device
WDM device which is intended to operate for channel spacing < 50 nm and > 1 000 GHz
3.1.5
WWDM
wide WDM device
WDM device which is intended to operate for channel spacing ≥ 50 nm
3.1.6
wavelength multiplexer
MUX
WDM (DWDM, CWDM or WWDM) device which has n input ports and one output port, and
whose function is to combine n different optical signals differentiated by wavelength from n
corresponding input ports on to a single output port
3.1.7
wavelength demultiplexer
DEMUX
WDM (DWDM, CWDM or WWDM) device which has one input port and n output ports, and
whose function is to separate n different optical signals differentiated by wavelength from a
single input port to n corresponding output ports
3.1.8
interleaver
DWDM device which has three ports, and which function is to separate n different optical signals
differentiated by wavelength from a common port and transmit an odd channel signal to one
branching port and an even channel signal to the other branching port alternately
Note 1 to entry: An interleaver can operate as a wavelength multiplexer (OMUX) by reversing the demultiplexer.
3.2 Performance terms
3.2.1
operating wavelength
nominal wavelength λ at which a WDM device operates with the specified performance
h
Note 1 to entry: The term "operating wavelength" includes the wavelength to be nominally transmitting, designated
attenuating and isolated.
Note 2 to entry: Operating frequency is also used for DWDM devices.
3.2.2
operating wavelength range
specified range of wavelengths including all operating wavelengths
Note 1 to entry: It includes all passbands and isolation wavelength ranges corresponding to all channels.
Note 2 to entry: The term "operating wavelength range" is defined for a WDM device, not for each channel or port.
3.2.3
channel wavelength range
passband
channel passband
range within which a CWDM or WWDM device operates with less than or equal to a specified
optical attenuation for the conducting port pair
Note 1 to entry: For a particular nominal channel centre wavelength, λ , this wavelength range from
nom
λ = (λ – ∆λ ) to λ = (λ + ∆λ ), where ∆λ is the maximum channel centre wavelength deviation.
imin nom max imax nom max max
Note 2 to entry: For CWDM devices, channel centre wavelengths and maximum channel centre wavelength
deviations are defined as nominal central wavelengths and wavelength deviations in ITU-T Recommendation G 694.2.
Note 3 to entry: An illustration of channel wavelength range is shown in Figure 1.
Note 4 to entry: Passband is frequently used.
Note 5 to entry: There are two or more passbands for WDM devices. Each passband is defined corresponding to
each channel.
Figure 1 – Illustration of channel wavelength range
3.2.4
channel frequency range
frequency range within which a DWDM device is required to operate with less than or equal to
a specified optical attenuation for the conducting port pair
Note 1 to entry: For a particular nominal channel frequency, f , this frequency range is from f = (f – ∆f )
nomi imin nomi max
to f = (f + ∆f ), where ∆f is the maximum channel centre frequency deviation.
imax nomi max max
Note 2 to entry: Nominal channel centre frequency and maximum channel centre frequency deviation are defined
in ITU-T G.694.1.
3.2.5
insertion loss
maximum value of a (where i ≠ j) within the passband for conducting port pair

ij
Note 1 to entry: It is the optical attenuation from a given port to a port which is another port of conducting port pair
of the given port of a WDM device. Insertion loss is a positive value in decibels. It is calculated as:
 P 
out
IL =−10×log
10  
P
 in 
where
P is the optical power launched into the port;
in
P is the optical power received from the other port of the conducting port pair.
out
Note 2 to entry: An illustration of insertion loss is shown in Figure 2.
Figure 2 – Illustration of insertion loss
Note 3 to entry: For a WDM device, the insertion loss shall be specified as a maximum value of the insertion losses
of all channels
3.2.6
channel insertion loss
maximum value of a (where i ≠ j) within the passband at the specific channel
ij
3.2.7
passband ripple
maximum peak-to-peak variation of the insertion loss over the passband
Note 1 to entry: Insertion loss is expressed as a positive value.
Note 2 to entry: The term of passband is applied both for the unit of wavelength (WWDM and CWDM) and the unit
of frequency (DWDM).
Note 3 to entry: Refer to Figure 3.

a) Ripple at band edges b) Ripple in band

Figure 3 – Illustration of ripple
3.2.8
maximum channel insertion loss deviation within the passband
maximum variation of the insertion loss
Note 1 to entry: Insertion loss is a positive value.
Note 2 to entry: The channel frequency range for a DWDM device or channel wavelength range for a coarse WDM
(CWDM) and a wide WDM (WWDM) device can be used for passband.
Note 3 to entry: See Figure 4.
Note 4 to entry: Channel insertion loss deviation should not be confused with ripple defined in Figure 3 above.

Figure 4 – Illustration of channel insertion loss variation
3.2.9
channel non-uniformity
insertion loss channel non-uniformity
difference between the maximum and the minimum insertion loss at the common port for a
specified set of branching ports
Note 1 to entry: Channel non-uniformity is defined for a MUX (N × 1 WDM device) and a DEMUX (1 × N WDM
device). Channel non-uniformity is a positive value and expressed in dB.
Note 2 to entry: For CWDM and DWDM devices, channel non-uniformity should be defined as the differences
between the maximum and the minimum insertion loss at nominal wavelengths (frequencies) of all channels.
3.2.10
centre wavelength deviation
difference between the centre wavelength and nominal wavelength (frequency) of the specified
channel for DWDM devices
Note 1 to entry: The centre wavelength is defined as the centre of the wavelength range which is x dB less than the
minimum optical attenuation for the specified passband (channel).
Note 2 to entry: 0,5, 1 or 3 are generally used for x.
3.2.11
crosstalk
ratio of the noise power in the specified channel(s) versus the signal power in the specified
channel
Note 1 to entry: Crosstalk is a negative value given in dB. The crosstalk is defined for each output port. Crosstalk
for WDM devices is defined for a DEMUX (1 × N WDM device). The crosstalk for port o to port j is subtraction from
the insertion loss of port i to o (conducting port pair) to the isolation of port j to o (isolated port pair). Crosstalk for
WDM devices is defined for a DEMUX (1 × N WDM device). For an MxN WDM device, crosstalk can be defined to as
expanding M of a 1 × N WDM device.
Note 2 to entry: For WDM devices with three of more ports, the crosstalk should be specified as the maximum value
of the crosstalk for each output port.
Note 3 to entry: Care should be taken not to confuse crosstalk and isolation.
3.2.12
isolation
minimum value of a (where i ≠ j) within an isolation wavelength range for an isolated port pair
ij
Note 1 to entry: Isolation is a positive value expressed in dB.
3.2.13
isolation wavelength
for a pair of ports i and j (where i ≠ j), that are conducting port pair at a wavelength λ , nominal
h
wavelength λ (where λ ≠ λ ), that is an operating wavelength for a different pair of ports, at
k h k
which i and j are isolated port pair
Note 1 to entry: Refer to Figure 5.
Note 2 to entry: Isolation frequency is also used for DWDM device.

Figure 5 – Illustration of isolation wavelength
3.2.14
isolation wavelength range
for a pair of ports i and j that are a conducting port pair at wavelength λ , range of wavelengths
h
from λ to λ centred about an operating wavelength λ that is an operating wavelength
kmin kmax k
for a different pair of ports but at which i and j are an isolated port pair
Note 1 to entry: Refer to Figure 6.
Note 2 to entry: Isolation frequency range is also used for DWDM devices.

Figure 6 – Illustration of isolation wavelength range
3.2.15
wavelength isolation
value of a (where i ≠ j) in the isolation wavelength range
ij
Note 1 to entry: The wavelength isolation shall be defined as the minimum value of wavelength isolation over the
isolation wavelength range.
3.2.16
adjacent channel isolation
isolation with the restriction that x, the isolation wavelength number, is restricted to the channels
immediately adjacent to the (channel) wavelength number associated with port o
Note 1 to entry: Adjacent channel isolation is a positive value expressed in dB.
Note 2 to entry: This is illustrated in Figure 7 below. The adjacent channel isolation is different from adjacent
channel crosstalk. In Figure 7, the upward-pointing arrow indicates a positive value, and the downward-pointing arrow
indicates a negative value. Generally, there are two adjacent channel isolations for the shorter wavelength (higher
frequency) side and the longer wavelength (lower frequency) side.
3.2.17
adjacent channel crosstalk
crosstalk with the restriction that x, the isolation wavelength number, is restricted to the
channels immediately adjacent to the (channel) wavelength number associated with port o
Note 1 to entry: Adjacent channel crosstalk is a negative value expressed in dB.
Note 2 to entry: This is illustrated in Figure 7 below. Adjacent channel crosstalk is different from adjacent channel
isolation. In Figure 7, the upward-pointing arrow indicates a positive value, and the downward-pointing arrow
indicates a negative value. Generally, there are two adjacent channel crosstalks for the shorter wavelength (higher
frequency) side and the longer wavelength (lower frequency) side.
Figure 7 – Illustration of adjacent channel isolation
3.2.18
non-adjacent channel isolation
isolation with the restriction that the isolation wavelength (frequency) is restricted to each of
the channels not immediately adjacent to the channel associated with port o
Note 1 to entry: Refer to Figure 8.
Note 2 to entry: The non-adjacent channel isolation is different from non-adjacent channel crosstalk. In Figure 8,
the upward-pointing arrow indicates a positive value, and the downward-pointing arrow indicates a negative value.
3.2.19
non-adjacent channel crosstalk
crosstalk where the isolation wavelength (frequency) is restricted to each of the channels not
immediately adjacent to the channel associated with port o
Note 1 to entry: Refer to Figure 8.
Note 2 to entry: Non-adjacent channel crosstalk is different from non-adjacent channel isolation. In Figure 8, the
upward-pointing arrow indicates a positive value, and the downward-pointing arrow indicates a negative value.
Figure 8 – Illustration of non-adjacent channel isolation
3.2.20
minimum adjacent channel isolation
minimum value of a within the adjacent operating wavelength (or frequency) range (adjacent
ij
channel passband)
Note 1 to entry: The minimum adjacent channel isolation is positive in dB.
Note 2 to entry: Refer to Figure 9 below. Generally, there are two minimum adjacent channel isolations. For a
channel, the minimum value of two minimum adjacent channel isolations is selected.
Note 3 to entry: The minimum adjacent channel isolation is different from the maximum adjacent channel crosstalk.
In Figure 9, the upward-pointing arrow indicates a positive value, and the downward-pointing arrow indicates a
negative value.
3.2.21
maximum adjacent channel crosstalk
maximum value of adjacent channel crosstalk within adjacent channel wavelength (frequency)
range (adjacent channel passband)
Note 1 to entry: This is the maximum value of the subtraction from the maximum insertion loss to the minimum
adjacent isolation. Maximum adjacent channel crosstalk is negative value in dB. Refer to Figure 9 below. Generally,
there are two maximum adjacent channel crosstalks. For a channel, the maximum value of two maximum adjacent
channel crosstalks is selected.
Note 2 to entry: The maximum adjacent channel crosstalk is different from the minimum adjacent channel isolation.
In Figure 9, the upward-pointing arrow indicates a positive value, and the downward-pointing arrow indicates a
negative value.
Figure 9 – Illustration of maximum adjacent channel crosstalk
3.2.22
minimum non-adjacent channel isolation
minimum value of a in the non-adjacent operating wavelength (or frequency) range (non-
ij
adjacent channel passband)
Note 1 to entry: Refer to Figure 10.
Note 2 to entry: The minimum adjacent channel isolation is different from the maximum adjacent channel crosstalk.
In Figure 10, the upward-pointing arrow indicates a positive value, and the down-pointing arrow indicates a negative
value.
3.2.23
maximum non-adjacent channel crosstalk
minimum difference between the maximum peak of a in the operating wavelength (or
ij
frequency) range and the minimum value of a in a specified range of wavelengths (or
ij
frequencies) from λ to λ centred about an isolation wavelength (or frequency) λ for any
kmin kmax k
and λ defining an operating wavelength (or frequency) range for a
two ports i and j, λ
kmin kmax
different pair of ports for which λ is an operating wavelength (or frequency)
k
Note 1 to entry: Refer to Figure 10.
Note 2 to entry: The minimum adjacent channel isolation is different from the maximum adjacent channel crosstalk.
In Figure 10, the upward-pointing arrow indicates a positive value, and the downward-pointing arrow indicates a
negative value.
Figure 10 – Illustration of maximum non-adjacent channel crosstalk
3.2.24
total channel isolation
logarithm with a base of 10 of the cumulative transmitting matrix element, t (where i ≠ j) for the
ij
number of channels
Note 1 to entry: The total channel isolation is defined as:
N

It=−10×log λ
( )
tot 10 ∑ ij k

k(k≠h)

where
N is the number of channels of the device;
h is the channel number corresponding to the conducting port pair of i and j;
λ are the nominal isolation wavelengths (frequencies) for the same pair of ports.
k
Note 2 to entry: Total channel isolation is positive in dB. For a WDM device, total channel isolation shall be specified
as a minimum value of the total channel isolations of all channels.
3.2.25
total channel crosstalk
logarithm with a base of 10 of the transmitting matrix element, t (where i ≠ j) divided by the
ij
cumulative transmitting matrix element t (where i ≠ j) for the number of channels
ij
Note 1 to entry: The total channel crosstalk is defined as:


t ()λ

ij h
XT =−10×Log
tot 10 
N

t ()λ
∑
ij k

kk()≠h

where
N is the number of channels of the device;
λ is the nominal operating wavelength (frequency) for the couple of ports i and j;
h
λ are the nominal isolation wavelengths (frequencies) for the same pair of ports.
k
Note 2 to entry: Total channel crosstalk is also expressed by total channel isolation as shown in the following
formula:
XT a λI−
( )
tot ij h tot
Note 3 to entry: Total channel crosstalk is negative value in dB. For a WDM device, total channel crosstalk shall be
specified as the maximum value of total channel crosstalks of all channels.
3.2.26
minimum total channel isolation
for any two ports i and j (where i ≠ j) the minimum value of the cumulative isolation due to the
minimum spectral contributions about all the isolation wavelengths (frequencies)
Note 1 to entry: The minimum total channel isolation is defined as:
N
min  * * 
It=−10×log λ
tot 10 ∑ ij ( k )
 k k≠h 
( )
 
where
N is the number of channels of the device;
h is the channel number corresponding to the conducting port pair of i and j;
k is the channel number except corresponding to the conducting port pair of i and j. It is the channel number to
be isolated for the combination of ports i and j;
t * is the maximum value of t at the wavelength λ * (channel wavelength range; (passband) of channel k);
ij ij k
λ * are the wavelengths (frequencies) corresponding to the maximum value of t in the specified ranges of
k ij
wavelengths (frequencies) from λ to λ about the isolation wavelengths (frequencies) λ for the pair of
kmin kmax k
ports i and j, λ and λ defining the operating wavelength (frequency) range for the pair of por
...