IEC 62496-4:2011

IEC 62496-4 ®
Edition 1.0 2011-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Optical circuit boards –
Part 4: Interface standards – General and guidance

Cartes à circuits optiques –
Partie 4: Normes d'interface – Généralités et lignes directrices

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IEC 62496-4 ®
Edition 1.0 2011-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Optical circuit boards –
Part 4: Interface standards – General and guidance

Cartes à circuits optiques –
Partie 4: Normes d'interface – Généralités et lignes directrices

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX U
ICS 33.180.01 ISBN 978-2-88912-317-9
– 2 – 62496-4  IEC:2011
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
3.1 General definitions . 6
3.2 Core shape definitions . 7
4 Coordinates of I/O ports of waveguide OCB . 9
4.1 Structural types of waveguide OCB . 9
4.2 Origin point and coordinate axis . 11
4.2.1 General . 11
4.2.2 Origin point and coordinate axis by internal coordinate . 12
4.2.3 Origin point and axis by external coordinate . 14
4.2.4 Origin point and axis employing both internal and external
coordinates. 15
5 Misalignment angle of I/O ports . 16
5.1 General . 16
5.2 Misalignment angle of I/O port in edge type . 16
5.3 Misalignment angle in surface type I/O port . 18
6 Mirror angle . 19
7 Hole . 21
8 Dimensioning system . 22
9 Gauges . 22
10 Tolerance grade of the OCB . 22
10.1 General . 22
10.2 Shape accuracy of the OCB body of fibre flexible OCB . 23
10.3 Position accuracy of the OCB port/I/O port of fibre flexible OCB . 23
10.4 Length accuracy of the OCB tails of fibre flexible OCB . 24
Annex A (normative) OCB interfaces . 25
Annex B (informative) Example of the OCB . 28
Bibliography . 30

Figure 1 – Examples of shapes of square core (quasi-square made by extrapolation or

interpolation) . 8
Figure 2 – Examples of shapes of circular core . 8
Figure 3 – Six structural parameters of square core shape of waveguide OCB . 9
Figure 4 – Example of OCB with end face I/O ports at edge of board . 10
Figure 5 – Example of OCB with end face I/O type. 10
Figure 6 – Example of OCB with surface I/O ports . 11
Figure 7 – Example of OCB with surface I/O ports . 11
Figure 8 – Definition of origin point 1): A specific port is used as the origin point . 12
Figure 9 – Definition of origin point 2): Determination of an origin point at a place
where there is no port (a mid-point of adjacent two ports at the centre of bottom line is
used as the origin) . 13

62496-4  IEC:2011 – 3 –
Figure 10 – Definition of the direction of coordinate axis 1): Use the direction of
alignment of multiple ports . 13
Figure 11 – Definition of direction of coordinate axis 2): Along a specific optical circuit
(only if the wire is recognizable). 13
Figure 12 – Origin point and coordinate axis (1) . 14
Figure 13 – Origin point and coordinate axis (2) . 14
Figure 14 – Origin point and direction of coordinate axis (combination of Figure 12 and
Figure 13) . 15
Figure 15 – Use of both internal coordinate and external coordinate systems: Internal
for the origin point (a specific optical input/output port) and external for the direction of
the axis (dedicated structures) . 15
Figure 16 – Use of both internal coordinate and external coordinate systems: Internal
for the origin point (coordinates of a specific optical input/output port) and external for
the direction of the axis (periphery of the board) . 16
Figure 17 – Definition of misalignment angle of I/O port in edge type . 17
Figure 18 – Definition of vertical and horizontal rotational misalignment angle of I/O
port in edge type . 17
Figure 19 – Definition of misalignment angle of I/O port in surface type . 18
Figure 20 – Definition of longitudinal and lateral misalignment angle of I/O port in
surface type . 19
Figure 21 – Mirror angle 1 . 19
Figure 22 – Mirror angle 2 . 19
Figure 23 – Mirror angle 3 . 20
Figure 24 – Mirror angle 4 . 20
Figure 25 – Mirror tilt angle . 21
Figure 26 – Example of optical alignment hole . 21
Figure 27 – Hole and objects to be measured . 22
Figure 28 – Classification of shape accuracy of OCB body of fibre flexible OCB . 23
Figure B.1 – Example of the fibre flexible OCB . 28
Figure B.2 – Origin point and coordinate for the fibre flexible OCB . 29

Table 1 – The coordinate system, origin point and coordinate axis . 12

– 4 – 62496-4  IEC:2011
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL CIRCUIT BOARDS –
Part 4: Interface standards –
General and guidance
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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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 62496-1 has been prepared by IEC technical committee 86: Fibre
optics.
The text of this standard is based on the following documents:
FDIS Report on voting
86/379/FDIS 86/386/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.

62496-4  IEC:2011 – 5 –
A list of all the parts in the IEC 62496 series, under the general title Optical circuit boards,
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.
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.
– 6 – 62496-4  IEC:2011
OPTICAL CIRCUIT BOARDS –
Part 4: Interface standards –
General and guidance
1 Scope
This part of IEC 62496 covers general information on the subject of Optical Circuit Board
(OCB) interfaces. It includes normative references, definitions and rules for creating and
interpreting the standard drawings.
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 60793-1-45, Optical fibres – Part 1-45: Measurement methods and test procedures –
Mode field diameter
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 General definitions
3.1.1
OCB interface
sizes and relative locations for the features comprising the OCB. It also includes the location
of the coordinates of the alignment mark
3.1.2
OCB body
portion of an OCB where optical fibres/waveguides are fixed/fabricated to form an optical
routing pattern. The typical shape of an OCB body is rectangular
3.1.3
shape of the OCB body
outline of the OCB body which consists of a straight line and a curved line
NOTE The straight line is defined by coordinates of start point and end point, and the curved line is defined by the
coordinates of the start and the end points of the curve and by radius of curvature.
3.1.4
OCB tail
(OCB leg)
projection from the OCB body for interconnection with optical fibre cables and/or optical
components
3.1.5
length of the OCB tail
distance between the edge of an OCB body and the end of the OCB tail protruding from the
edge of the OCB body
62496-4  IEC:2011 – 7 –
NOTE If the OCB tail has a mark in the vicinity of its end, the OCB tail length is the distance between the mark
and the end of the OCB body.
3.1.6
OCB port
position on the edge of the OCB body where OCB tails protrude from the OCB body
NOTE Relative positional accuracy between the OCB port and alignment mark or origin point is important for
connection with other boards or devices. The OCB port is defined only for the fibre flexible OCB.
3.1.7
position of the OCB port
coordinates at the intersectional point of the central axis of the optical fibre and the edge of
the OCB body
NOTE The coordinates of the OCB port consisting of closely arrayed fibres shall be defined by the coordinates of
the OCB port closest to the origin point.
EXAMPLE In a case where the OCB body of the fibre flexible OCB is put in the first quadrant and an outline or an
angle of the OCB is in contact with the X-axis or the Y-axis, as shown in Figure B.2 of Annex B, the coordinates of
origin are defined as the origin point of the fibre flexible OCB. It is recommended to set one side of the OCB body
parallel to the X-axis or the Y-axis. In another case where the alignment mark for assembly of optical components
on the OCB is located near the I/O ports, the centre of the alignment mark is defined as the origin point of the OCB.
3.1.8
I/O port
window in the OCB through which optical energy enters and/or exits
NOTE The I/O port is located at the end of the OCB tail, at the edge of the OCB body or at the surface of the OCB
where the OCB is connected to optical fibre cables and/or optical components.
3.1.9
alignment mark for assembly of OCB
mark on the OCB body, typically a through hole in the OCB body, for assembly of the OCB to
another board and/or equipment
NOTE The coordinates of the alignment mark are defined by the coordinates at the centre of the mark. The
alignment mark is used instead of a datum target in Annex A.
3.2 Core shape definitions
There are two types of core shape, square or circular, for waveguide OCBs
EXAMPLE 1 Square shape consists of four corners formed by extrapolating or interpolating an arbitrary shape by
four straight lines, as shown in Figure 1.

– 8 – 62496-4  IEC:2011
Typical core Typical core Typical core Typical core
Typical core
cross-section (2) cross-section (3) cross-section (4) cross-section (5)
cross-section (1)
Typical core Typical core
Typical core Typical core Typical core
shape (4) shape (5)
shape (1) shape (2) shape (3)
IEC  018/11
Figure 1 – Examples of shapes of square core
(quasi-square made by extrapolation or interpolation)
EXAMPLE 2 Circular shape has round boundaries. It is not necessarily perfectly circular and includes elliptical
shapes or any round shapes. Examples of circular shapes are shown in Figure 2.
Typical core
Typical core Typical core
cross-section (6)
cross-section (7) cross-section (8)

IEC  019/11
Figure 2 – Examples of shapes of circular core
The six structural parameters for the square core shape are shown in Figure 3. Structural
parameters for the circle core shape are defined by NFP (near field pattern) observation of a
cross section (see IEC 60793-1-45).
3.2.1
core width (top)
upper horizontal component of the core shape
3.2.2
core width (bottom)
lower horizontal component of the core shape
3.2.3
core height
distance between the lower and upper horizontal lines

62496-4  IEC:2011 – 9 –
3.2.4
core centre
intersection point of two diagonal lines of a quadrangle consisting of four midpoints of four
lines of the core shape, as illustrated in Figure 3
NOTE This intersection point corresponds to the centre of gravity in a system of material points.
3.2.5
core inner diameter
diameter of an inscribing circle with its centre at the core centre
3.2.6
core outer diameter
twice the distance between the core centre and the farthest corner of the core shape
Core width (top)
Core
centre
Core
height
Core width (bottom)
Core width Core height and core centre
Circle
(Centre of circle is the core centre)
Core
centre
Core inner diameter
Inscribing
core
Core outer
diameter
core inner diameter Core outer diameter
IEC  020/11
Figure 3 – Six structural parameters of square core shape of waveguide OCB
4 Coordinates of I/O ports of waveguide OCB
4.1 Structural types of waveguide OCB
OCBs are divided into two types defined by the positions and orientations of their optical I/O
ports. According to one type, the input / output port is defined by the exposed cross-section of
a waveguide at an edge of the board (end face I/O type), as illustrated in Figure 4, or at an
edge of a hole formed inside the area of the board, as illustrated in Figure 5. According to
another type, the input / output port contains an optical path converter such as a mirror to
deflect optical signals out of or into the surface of the board (surface I/O type), as illustrated
in Figure 6. An optical path converter can also be defined by a waveguide, which is bent
towards the surface of the board, such that its cross-section is exposed on the surface of the

– 10 – 62496-4  IEC:2011
board and thereby forms a surface I/O port, as illustrated in Figure 7. A board may contain
both types of I/O port. The coordinates of an end face I/O port, as illustrated in Figure 4, are
defined by the core centre as set out in 3.10.1.4. A surface I/O port is defined by the
projection of an optical path converter, such as a mirror, on the surface of the board, as
illustrated in Figure 6. The position of the I/O port in the axis orthogonal to the plane of the
board is defined at the surface of the board on which the projection appears. The coordinates
of the surface I/O port are defined by the centre of the projected area of the optical path
converter on the surface or the centre of the core of a bent waveguide exposed on the surface,
as set out in 3.10.1.4. Optical I/O ports on both types of OCB can be distributed in 2
dimensions across a plane shared by the I/O port cross-section, as shown in Figure 4 and
Figure 6.
I/O ports (end face of OCB)
I/O ports (end face of OCB) Optical circuit
(a) Side view (b) View from left side
Substrate
IEC  021/11
Figure 4 – Example of OCB with end face I/O ports at edge of board

(a) Bird’s eye view
Hole
I/O port
(b) Side view
IEC  022/11
Figure 5 – Example of OCB with end face I/O type

62496-4  IEC:2011 – 11 –
(a) Top view
I/O port
I/O port
Optical circuit
Optical circuit layer
Mirror
Substrate
(b) Side view
IEC  023/11
Figure 6 – Example of OCB with surface I/O ports

(a) Top view
I/O port Optical circuit
Optical layer
Substrate
(b) Side view
Bent waveguide
IEC  024/11
Figure 7 – Example of OCB with surface I/O ports
4.2 Origin point and coordinate axis
4.2.1 General
It is necessary to clearly define the origin point and coordinate axis of a port for transfer of
coordinate data between optical Input/output ports. They are defined in the following way:
There are two reference systems, the internal reference system and external reference
system according to the definition of an origin point. The internal reference system is the
system with the origin point at a specific optical input/output port, or the system with the origin
point at the mid-point of two optical Input/output ports. There are cases for the external
reference system, one with an origin point of a dedicated structure such as a marker and the
other with an origin point of one point of an OCB such as an edge of the board. The
coordinate system, origin point and coordinate axis are summarized in Table 1.

– 12 – 62496-4  IEC:2011
Table 1 – The coordinate system, origin point and coordinate axis
Coordinate system Origin point Example of Axis Applicable to
Internal coordinate Specific I/O port Aligned direction of
system multiple I/O ports
End face I/O port type
A specific position on an Direction of aligned I/O
OCB ports in a specific
direction
A dedicated newly Use a dedicated newly Surface I/O port type
formed structure formed structure
External coordinate
system A structure existing on an Use one outer edge of an End face I/O port type
OCB OCB
Internal coordinate A specific I/O port as the origin and use an external Surface I/O port type
system/ coordinate system as the coordinate axis
external Coordinate
system
4.2.2 Origin point and coordinate axis by internal coordinate
They are defined by means of the coordinates of specific optical input/output ports for an OCB
which does not have a specific structure for an origin point and coordinate axis. A definition
made in this way is known as definition by internal coordinate system. Examples of the
definition of origin point are 1) use of specific optical input/output ports as the origin point, as
illustrated in Figure 8, and 2) to define an origin at a specific point on a board, a point where
there are no optical input/output ports but which can easily be identified (see Figure 9). Figure
9 is an example of defining an origin at the mid-point between two neighbouring ports at the
centre of the bottom line of ports on a board. There are two ways of defining the direction of
an axis 1) the direction of a line intersecting multiple ports (Figure 10), or 2) use of the
direction of a specific optical circuit (Figure 11) when the wiring is recognisable and straight.
Definitions of names of axis (e. g., “x” or “y”) and sign (“-x” or “-y”) are also to be defined
simultaneously. When the direction of one axis is defined, the direction of the other axis is at
a right angle to the direction of the axis defined first. This coordinate system is suitable for an
OCB with end face type ports (cross section), but can also be applicable to a board with
surface type input/output ports.
I/O ports
Origin point
IEC  025/11
Figure 8 – Definition of origin point 1): A specific port is used as the origin point

62496-4  IEC:2011 – 13 –
I/O ports
Origin point
IEC  026/11
Figure 9 – Definition of origin point 2): Determination of an origin point at a place
where there is no port (a mid-point of adjacent two ports
at the centre of bottom line is used as the origin)

I/O ports
+x
Coordinate axis (x)
IEC  027/11
Figure 10 – Definition of the direction of coordinate axis 1):
Use the direction of alignment of multiple ports

Optical circuit I/O ports
+y
Optical circuit
Coordinate axis (y)
IEC  028/11
Figure 11 – Definition of direction of coordinate axis 2):
Along a specific optical circuit (only if the wire is recognizable)

– 14 – 62496-4  IEC:2011
4.2.3 Origin point and axis by external coordinate
A way of defining the origin point and coordinate axis of an OCB using a structure formed on
the board for the purpose of indicating the origin point and coordinate axis, or using a specific
visible structure on the OCB is known as the definition of origin point and axis by external
coordinate system. Figure 12 shows the case where a structure is formed on a board to
indicate the origin point and the direction of coordinate axis, and Figure 13 shows the case
where a structure already exists on a board is used for reference. Figure 13 is the case of
using peripheral (edge) of a board. This method is effective especially for a board with edge-
type optical input/output ports when the precision of the dimension of the edge is high enough.
The OCB may be connected to an optical connector with passive alignment in reference to the
outer shape of the OCB. It is possible for one of the origin points or axes to be based on an
internal coordinate system while the other is based on an external coordinate system, as
illustrated in Figure 14.
I/O ports
+x
Mark for
Mark for
coordinate axis
coordinate axis
Mark for origin point
IEC  029/11
Figure 12 – Origin point and coordinate axis (1)

Outline of OCB
I/O ports
＋y
Coordinate axis (y)
Coordinate axis (x)
Origin point (corner of OCB)
IEC  030/11
Figure 13 – Origin point and coordinate axis (2)

62496-4  IEC:2011 – 15 –
Outline of OCB
I/O ports
+y
+x
Mark for origin point
IEC  031/11
Figure 14 – Origin point and direction of coordinate axis
(combination of Figure 12 and Figure 13)
4.2.4 Origin point and axis employing both internal and external coordinates
It is possible to define the origin point and coordinate axis using both of the coordinate
systems. Examples are shown in Figures 15 and 16. The origin point is defined by the internal
coordinate system in both examples using a specific input/out port and the direction of the
axis is defined by the external coordinate system. A dedicated structure is used in Figure 15,
and the peripheral of a board is used in Figure 16.
I/O ports
Coordinate axis (x) +x
Mark for
Mark for
coordinate axis
coordinate axis
Origin point
IEC  032/11
Figure 15 – Use of both internal coordinate and external coordinate systems:
Internal for the origin point (a specific optical input/output port) and external
for the direction of the axis (dedicated structures)

– 16 – 62496-4  IEC:2011
Outline of OCB
I/O ports
+y
Coordinate axis (y)
Coordinate axis (x) +x
Origin point
IEC  033/11
Figure 16 – Use of both internal coordinate and external coordinate systems:
Internal for the origin point (coordinates of a specific optical input/output port)
and external for the direction of the axis (periphery of the board)
5 Misalignment angle of I/O ports
5.1 General
Misalignment angle of I/O ports is angle between the cross section of I/O ports and the axis of
the waveguide (or the surface of the board) is required to estimate the optical coupling
efficiency with other I/O ports. The misalignment angle is defined by the angle between the
surface of the I/O port and the perpendicular plane to the axis of the waveguide. Since tilting
of a plane in three dimensions is possible toward three independent directions, it is necessary
to describe the tilt angles separately for edge type and surface type I/O ports.
5.2 Misalignment angle of I/O port in edge type
For the end face I/O type, the misalignment angle θ is defined in Figure 17. The plane of the
t
I/O port is the surface plane of the I/O port where reflection and refraction occur when a light
passes through the I/O port. The axis of the waveguide is the axis passing through the centre
of the core in a short range near the I/O port. The angle θ of I/O port is determined by the
t
angle between the normal direction of the plane of the I/O port and the z direction, when the
waveguide axis is aligned to the -z direction.

62496-4  IEC:2011 – 17 –
y
– x
π – θ
t
– z
z
θ
t
Optical axis
Optical circuit
I/O port
IEC  008/11
Figure 17 – Definition of misalignment angle of I/O port in edge type
When the misalignment angle is measured from a cross section of the waveguide, the angle
may be represented on two orthogonal cross sections, as shown in Figure 18 (a) and (b). On
a vertical cross section of OCB which is cut along the core of a waveguide, An angle of
vertical rotational misalignment θ (V) is defined by the angle subtended by the plane of the I/O
t
port and the vertical axis y as illustrated in Figure 17. An angle of horizontal rotational
misalignment θ (H) is defined by the angle subtended by the plane of the I/O port and the
t
horizontal axis x as illustrated in Figure 17. The angle θ defined by the normal direction of the
t
plane of the I/O port in Figure 17 is approximated by equation 1:
2 2
sinθ ≈ sin θ (V )+ sin θ (H )  (1)
t t t
when θ (V) and θ (R) are small angles.
t t
y
θ (H)
t
y
θ (V)
t
x
x
z
z
Optical circuit
Optical axis
Optical axis
θ (H)
Optical circuit
t
θ (V)
t
Side view
I/O port
Top view
I/O port
IEC  010/11 IEC  011/11
(a) Vertical (rotational) misalignment angle (b) Horizontal (rotational) misalignment angle
Figure 18 – Definition of vertical and horizontal rotational
misalignment angle of I/O port in edge type

– 18 – 62496-4  IEC:2011
5.3 Misalignment angle in surface type I/O port
For the surface I/O type, the misalignment angle is defined in Figure 19. The axis of the
waveguide and the normal direction of the plane of the I/O port are determined by the same
manner as those in the end face I/O port. The angle θ of the I/O port is determined by the
t
angle between the normal direction to a plane of the I/O port and the z direction of the axis of
the waveguide. If the plane of the surface I/O port corresponds to the surface of the OCB, the
normal direction to a plane of the I/O port becomes the perpendicular direction to the surface
of the OCB.
Optical axis
z
θ
t
I/O port
Optical circuit
IEC  009/11
Figure 19 – Definition of misalignment angle of I/O port in surface type
In the surface type I/O port, the misalignment angle may be also divided into two angles,
according to the selection of the cross section, as illustrated in Figure 20 (a) and Figure 20 (b).
On a longitudinal cross section of the OCB, along the core of a waveguide, a longitudinal
angle θ (Lg) is revealed from the plane of the surface I/O port. On a lateral cross section of
t
OCB across a waveguide array, which is perpendicular to the longitudinal cross section,
lateral angle θ (Lt) is revealed from the plane of the surface I/O port. The misalignment angle
t
θ defined by the normal direction of the plane of the I/O port in Figure 19 is approximated by
t
equation 2:
2 2
sinθ ≈ sin θ (Lg)+ sin θ (Lt) (2)
t t t
when θ (Lg) and θ (Lt) are small angles.
t t
62496-4  IEC:2011 – 19 –
y
I/O port
x
Cross section line for
side view
I/O port
θ (Lt)
t
Top view
Optical circuit
z
z
Optical axis
y
θ (Lg)
t
x
Front view Top view
Cross section line
for front view
Optical axis
Side view
IEC  012/11 IEC  013/11
(a) Longitudinal misalignment angle of I/O (b) Lateral misalignment angle
port in surface type
Figure 20 – Definition of longitudinal and lateral misalignment angle
of I/O port in surface type
6 Mirror angle
A mirror angle is defined as the angle between a mirror surface and a reference line.
(1) mirror angle 1
angle θ subtended by a mirror surface and a core bottom boundary shown in Figure
21. The reference line was set on boundary edge between core and cladding. Another
reference line is a tangential to the plane of the mirror at the core cladding interface.
Cladding
Reference line
Core
θ
Cladding
IEC  034/11
Figure 21 – Mirror angle 1
(2) mirror angle 2
angle θ subtended by a mirror surface and an optical waveguide surface shown in
Figure 22. The reference line was set on the surface of an optical waveguide. Another
reference line is a tangential to the plane of the mirror at the waveguide surface.
Cladding
Core
Reference line
θ
Cladding
IEC  035/11
Figure 22 – Mirror angle 2
– 20 – 62496-4  IEC:2011
(3) mirror angle 3
angle θ of subtended by a mirror surface and an OCB surface is shown in Figure 23.
The reference line was set on the surface (or bottom) of an OCB. Either of the angles
defined in 3.14 (1) or 3.14 (2) may be used instead of this angle if the bottom of the
OCB cannot be measured. Another reference line is a tangential one at the OCB
surface.
Cladding
Core OCB
Cladding
θ
Reference line
IEC  036/11
Figure 23 – Mirror angle 3
(4) angle between mirror and OCB, optical waveguide and upper surface of the
core:
it is permissible to use the upper boundary edge of the board as in 3.13 (1) to 3.13 (3).
The reflection angle θ is the angle subtended by the upper boundary of the board and
the tangent to the plane of the mirror at the upper boundary as illustrated in Figure 24.
θ
Cladding
Core
Reference line
Cladding
IEC  037/11
Figure 24 – Mirror angle 4
(5) mirror tilt angle
angle φ subtended by a mirror surface and the plane normal to the optical axis of the
t
waveguide shown in Figure 25.
62496-4  IEC:2011 – 21 –
Reference line
Top view
Mirror
Cladding
Core
Cladding
Cross section view
IEC  038/11
Figure 25 – Mirror tilt angle
7 Hole
A hole made on the surface of an OCB or on the edge of the board to insert a component
such as an optical device is called a hole. A hole required for accurate optical alignment of
the optical I/O ports between an OCB and an optical component is defined as an optical
alignment hole. The optical alignment can be achieved by inserting guide pins into the
alignment holes which are formed on both sides of an OCB and an optical component, as
illustrated in Figure 26.
Optical component
Optical alignment hole
Guide pin
Optical I/O port
OCB
Waveguide
IEC  039/11
Figure 26 – Example of optical alignment hole
A typical example of the hole is shown in Figure 27. Structural parameters for hole are as
follows.
(1) long diameter on the top side (V )
1t
the longest distance across a hole when seen from above on a board is the long
diameter of a hole. When a hole is a true circle or square, the long diameter and the
short diameter of a hole are the same.
)
(2) short diameter on the top side (V
2t
the shortest distance across a hole on a board when seen from above is the short
diameter of a hole. When a hole is a true circle or square, the long diameter and the
short diameter of a hole are the same.

– 22 – 62496-4  IEC:2011
(3) long diameter on the bottom side (V )
1b
the longest distance across a hole on a board when seen from below is the long
diameter of a hole. When a hole is a true circle or square, the long diameter and the
short diameter of a hole are the same.
(4) short diameter on the bottom side (V )
2b
the shortest distance across a hole on a board when seen from below is the short
diameter of a hole. When a hole is a true circle or square, the long diameter and the
short diameter of a hole are the same.
(5) depth of a hole (V )
d
when a hole does not completely penetrate a board (i.e. a blind hole), the depth of the
hole is defined as the hole depth.

V V
2t 2t
V V
1t 1t
V V
1b 1b
V V
2 2
V
d
IEC  040/11
Figure 27 – Hole and objects to be measured
8 Dimensioning system
The interface dimensions listed in subsequent parts of IEC 62496-4-1 are presented and
interpreted using the tolerancing methods described in Annex A.
9 Gauges
This standard is not intended as a gauging standard. It shall not be assumed that gauges that
are included as a method for specifying sizes and locations of features must be designed
exactly as illustrated.
10 Tolerance grade of the OCB
10.1 General
The OCB is graded by tolerance. Each grade tolerance is identified in the standard by a grade
number. The grades and the grade numbers are as follows.

62496-4  IEC:2011 – 23 –
10.2 Shape accuracy of the OCB body of fibre flexible OCB
Classification of accuracy of shape of an OCB body of the fibre flexible OCB in comparison
with design is given below.
Class A:
Less than ± 1 mm for the designated dimension less than 200 mm
Less than ± 0,5 % of the designated dimension for the dimension ranging
...