IEC TR 60825-17:2010

IEC/TR 60825-17
®
Edition 1.0 2010-11
TECHNICAL
REPORT

Safety of laser products –
Part 17: Safety aspects for use of passive optical components and optical
cables in high power optical fibre communication systems


IEC/TR 60825-17:2010(E)

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IEC/TR 60825-17
®
Edition 1.0 2010-11
TECHNICAL
REPORT

Safety of laser products –
Part 17: Safety aspects for use of passive optical components and optical
cables in high power optical fibre communication systems


INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
R
ICS 31.260; 33.180.01. ISBN 978-2-88912-237-0
® Registered trademark of the International Electrotechnical Commission

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– 2 – TR 60825-17 Ó IEC:2010(E)
CONTENTS
FOREW ORD . 3
INTRODUCTION . 5
1 Sc o pe . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Recommendations . 8
4.1 General considerations – the background to optical fibre damage at high
powers . 8
4.2 Additional recommendations for automatic power reduction (APR) . 8
4.3 The need for additional user information and its recommended format . 9
4.4 Fibre and connector damage induced by high optical powers . 11
4.4.1 Fibre fuse and other effects . 11
4.4.2 Contamination particles . 12
4.5 Splicing, polishing, and cleaning of connectors and fibre, and fibre
preparation . 12
4.5.1 General . 12
4.5.2 Fibre in a splice tray . 12
4.6 Other fibre core damage, coating or cladding damage and damage to
adjacent services . 13
4.7 Degradation or burn-through of protection cap and/or shutter . 13
4.8 Potentially collimated beam profile resulting in an increased optical hazard . 13
4.8.1 General . 13
4.8.2 High power expanded beam connectors . 14
4.8.3 Secondary hazards – fire hazard . 14
4.9 Increases in the temperatures of attenuators, collimators, splitters and other
passive components . 14
4.10 Additional labelling . 15
4.11 Potential problems arising from incompatibly between fibre types. 15
4.12 Identification of non-standard damage-resistant fibres . 15
4.13 Other effects due to novel coatings or construction . 16
Bibliography . 17

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TR 60825-17 Ó IEC:2010(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

SAFETY OF LASER PRODUCTS –

Part 17: Safety aspects for use of passive optical components
and optical cables in high power optical fibre communication systems


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
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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.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 60825-17, which is a technical report, has been prepared by IEC technical committee 76:
Optical radiation safety and laser equipment.

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– 4 – TR 60825-17 Ó IEC:2010(E)
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
76/425/DTR 76/435/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 of the IEC 60825 series, published under the general title Safety of laser
products, 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.
A bilingual version of this publication may be issued at a later date.

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TR 60825-17 Ó IEC:2010(E) – 5 –
INTRODUCTION
The rapid growth of applications such as the internet and business intranets requiring high
bitrates has caused a dramatic increase in the need for high capacity data connections. This
increase in capacity has resulted in a requirement for a corresponding increase in power
levels used in optical fibre communications systems. There are a number of areas of concern
including the use of erbium doped fibre amplifiers (EDFA), high power dense wavelength
division multiplexing (DWDM) systems, and Raman amplification.
The power levels associated with these systems are typically greater than 500 mW
(i.e. Class 4), but some studies have shown additional thermal effects can occur at lower
powers. These additional thermal and related hazards mean that it is necessary to address a
number of new issues. It should be noted that the vast majority of these systems use single
mode fibre.

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– 6 – TR 60825-17 Ó IEC:2010(E)
SAFETY OF LASER PRODUCTS –

Part 17: Safety aspects for use of passive optical components
and optical cables in high power optical fibre communication systems



1 Scope
This part of IEC 60825 recommends safety measures to protect against effects caused
exclusively by thermal, opto-mechanical and related effects in passive optical components
and optical cables used in high optical power fibre communication systems.
This technical report does not apply to the use of high power optical systems in explosive
atmospheres or the use of optical fibres in material processing machines. Throughout this part
of IEC 60825, a reference to ‘laser’ is taken to include light-emitting diodes (LEDs) and optical
amplifiers.
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 60825-1:2007, Safety of laser products – Part 1: Equipment classification and
requirements
IEC 60825-2:2005, Safety of laser products – Part 2: Safety of optical fibre communication
systems (OFCS)
IEC/TR 61292-4, Optical Amplifiers – Part 4: Maximum permissible optical power for the
damage-free and safe use of optical amplifiers, including Raman amplifiers
IEC/TR 62547, Guidelines for the measurement of high-power damage sensitivity of single-
mode fibres to bends – Guidance for the interpretation of results
3 Terms and definitions
3.1
automatic laser shutdown (ALS)
technique (procedure) to automatically shutdown the output power of laser transmitters and
optical amplifiers to avoid exposure to hazardous levels
3.2
automatic power reduction (APR)
technique (procedure) to automatically reduce the output power of optical amplifiers to avoid
exposure to hazardous levels
3.3
automatic power shutdown (APSD)
technique (procedure) to automatically shutdown the output power of optical amplifiers to
avoid exposure to hazardous levels
NOTE In the context of this technical report the term APSD is equivalent to the term ALS.

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TR 60825-17 Ó IEC:2010(E) – 7 –
3.4
optical fibre communication system (OFCS)
an engineered, end-to-end assembly for the generation, transfer and reception of optical
radiation arising from lasers, LEDs or optical amplifiers, in which the transference is by means
of optical fibre for communication and/or control purposes
3.5
loss of continuity (of an optical link)
any event which may cause hazardous optical power levels to be emitted from some point
along the path of an optical transmission system
NOTE Common causes of loss of continuity of an optical link are a cable break, equipment failure, connector
unplugging, etc.
3.6
high optical power
an optical power of 500 mW or greater (in the context of this technical report)
NOTE 1 500 mW is recommended partly as it is the breakpoint between Class 3B laser products (unlikely to
cause fire) and Class 4 laser products (may cause fire).
NOTE 2 Studies have shown damage is significantly more likely at powers in excess of 1 W, but damage has also
1)
been shown to occur at powers as low as 200 mW – see references [1] and [2].
3.7
hazard level
the potential hazard at any accessible location within an OFCS. It is based on the level of
optical radiation which could become accessible in a reasonably foreseeable event, e.g. a
fibre cable break. It is closely related to the laser classification procedure in IEC 60825-1
[IEC 60825-2, definition 3.4]
3.8
unrestricted location
location with unrestricted access
an accessible location where there are no measures restricting access to members of the
general public
[IEC 60825-2, definition 3.15]
3.9
restricted location
location with restricted access
an accessible location that is normally inaccessible by the general public by means of any
administrative or engineering control measure but that is accessible to authorized personnel
who may not have laser safety training
[IEC 60825-2, definition 3.14]
3.10
controlled location
location with controlled access
an accessible location where an engineering or administrative control is present to make it
inaccessible, except to authorized personnel with appropriate laser safety training
[IEC 60825-2, definition 3.13]
___________
1)
Figures in square brackets refer to the Bibliography.

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– 8 – TR 60825-17 Ó IEC:2010(E)
3.11
class of laser product
see IEC 60825-1, sections 3.18 to 3.23 for definition of ‘class of laser product’
4 Recommendations
4.1 General considerations – the background to optical fibre damage at high powers
When optical fibres are operated at high power levels (typically > 500 mW), fibres and optical
connectors can be damaged. In optical communications systems the optical power is
transmitted in CW mode or at high repetition rates, and therefore catastrophic damage is
predominantly caused by thermal mechanisms. It has been shown that several effects can
cause high optical power-induced damage of single mode fibre systems leading to fibre
failures. Systems employing high optical power operation in fibres, connectors, collimators
and attenuators thus carry additional safety concerns. For example, local heating in
contaminated connectors/attenuators carrying high optical power can pose a potential fire
hazard to surrounding materials, depending on the flammability of those materials.
IEC/TR 61292-4 provides extensive guidance on the following topics (see also [7]):
– fibre fuse and its propagation;
– loss-induced heating at connectors or splices;
– connector end-face damage induced by dust/contamination;
– fibre-coat burn/melt induced by tight fibre bending.
Studies [3] on tight fibre bending at high power show that coating ageing can occur slowly and
catastrophic damage effects can occur after hundreds of hours. The main implication is that
damage testing must be carried out for sufficiently long times; some early experiments were
conducted over short times, possibly leading to incorrect conclusions. IEC/TR 62547 should
be followed for the measurement of high power damage sensitivity at bends.
As discussed by Bigot-Astruc M et al [4] and in IEC/TR 62547, a fast method of testing for
potential damage effects at high powers can use a thermal imaging camera. Equilibrium
temperatures are established relatively quickly, allowing the consequences of high power to
be rapidly assessed. The issues concerning high power at tight bends arise because of
exposure of the fibre coating to high power at or near to the bend. Coating ageing occurs at a
rate determined by bend loss, launch power, environmental conditions and coating resilience.
New bend insensitive fibre designs – described by the ITU G.657 specifications – are a
possible solution (see Section 2.5 in [8]). However, for extreme situations more resilient
coatings may also be required.
The long-term damage effects of high power in other optical components, described for
example in 4.5 and 4.9, show the need to consider the implications of high power damage
research, as discussed in IEC/TR 62547.
4.2 Additional recommendations for automatic power reduction (APR)
Extra recommendations for automatic power reduction (APR) are made because APR will
become more critical in systems where fire, fibre and connector damage, and other hazards
are possible if fibre is mishandled. These recommendations may include additional network
management and administrative controls, electrical connectivity testing for higher reliability of
APR, and others. Systems employing high optical power operation in fibres may necessitate
the incorporation of automatic power reduction within one section of a main optical path in the
event of recovery from the loss of optical power within that particular section of the main
optical path.

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TR 60825-17 Ó IEC:2010(E) – 9 –
Automatic power reduction should be specified and shown to have a high level of reliability for
systems using high optical power operation in fibres at all installed locations. IEC 60825-2
describes an ‘adequate’ level of reliability for APR systems (500 FITs).
9
NOTE IEC 60825-2 defines FITs as “an indicator of reliability defined as the number of failures per 10 h.”
Automatic power reduction should take into account all optical signals present in both
directions on the optical path, as described in the following excerpt reproduced with
permission from Recommendation ITU-T G.664 (1999), Optical safety procedures and
requirements for optical transport systems):
“APR techniques are necessary when the sum of operational power (main optical signal)
and pump-laser output power at the optical interfaces exceeds the applicable Hazard
Levels defined in IEC 60825-2. The total power is the sum of the power in any one
direction from all optical channels, the power from all pump-lasers and the power from
Optical Auxiliary Channels (OAC), if used. Within the context of this Recommendation,
an Optical Supervisory Channel (OSC) is regarded as a specific case of an OAC.
After power reduction, the total power level (the sum of the power from all optical
channels, the remaining power from pump-lasers and power from an OAC) must be
within Hazard Level 1M (or 3B in controlled locations), but reduction of the total power
to Hazard Level 1 or even complete shutdown is acceptable.
Optical transmission systems employing distributed Raman amplification need extra
care to ensure safe optical working conditions, because high pump powers (power
levels above +30 dBm are not uncommon) may be injected into optical fibre cables.
Therefore, it is recommended to use APR in all systems employing distributed Raman
amplification with operational power levels above Hazard Level 1M (or 3B in controlled
locations). In this way hazards from laser radiation to the human eye or skin, and
potential additional hazards such as temperature increase (or fire) caused by locally
increased absorption due to connector contamination or damage are avoided. Further
guidance is provided by IEC/TR 61292-4.
Distributed Raman-based systems differ from discrete optically amplified systems due to
the possible presence of pump lasers at the "receiving" side of a link, launching high
optical powers backward into the fibre. In order to ensure that the power levels radiating
from broken or open fibre connections are at safe levels, it is necessary to reduce the
power not only from the main optical signal sources but also from all pump lasers
employed, including the reverse pump lasers. Because the operating wavelength of the
Raman pump lasers is usually different from the actual data signal, separate
assessments at various wavelengths may need to be made both at pump laser
wavelength and at main signal wavelength.”
ITU-T G.664 Appendix II.3 describes automatic laser shutdown (ALS) and restart procedures
for single channel synchronous digital hierarchy systems with the additional presence of
optical amplification.
Operational aspects of APR should also comply with all relevant subclauses in
IEC 60825-2:2005, notably 4.5 (“Automatic power reduction (APR) and restart pulses”) and
4.5.4 (”Disabling of the APR”).
4.3 The need for additional user information and its recommended format
Due to the potentially increased hazards arising from higher optical powers, additional user
information may be needed. This subclause describes possible extra requirements that may
be placed on manufacturers, operating organizations and users (including extra training,
additional user manual requirements and others). Manufacturers of high optical power OFCS,
turnkey end-to-end high optical power systems or subassemblies intended to be incorporated
into high optical power systems should ensure that the equipment satisfies IEC 60825-2 and
the applicable advice of this technical report.

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– 10 – TR 60825-17 Ó IEC:2010(E)
The organization responsible for the installation and servicing of high optical power OFCS
should follow the manufacturer’s instructions for installation of equipment in a manner that will
ensure that the accessible radiation satisfies the applicable requirements of IEC 60825-2 and
the recommendations of this technical report, under all reasonably foreseeable conditions.
The operating organization has the ultimate responsibility for the safety of the high optical
power end-to-end system. This includes the determination of the location type (defined by
IEC 60825-2) at all accessible locations of the entire high optical power OFCS and ensuring
that access to any location is appropriately controlled with respect to laser safety. In addition
to the required markings of IEC 60825-2, it is suggested that hazard levels 2, 2M, 3R and 3B
locations in a high optical power OFCS should bear the label shown in Figure 1 of
IEC 60825-1.
At any location in a high optical power OFCS where access to a fibre end or a connector is
foreseeable, instructions should be provided to the operator or other persons having access.
These instructions should include directions to avoid direct exposure to laser radiation. It may
also be necessary to consider the need for the use of appropriate laser safety eyewear.
Only persons who have received appropriate training in optical fibre and high power hazards
(optical powers in excess of 500 mW is suggested) should be allowed to operate high optical
power OFCS.
Those persons responsible for ensuring that all required markings, protection and safeguards
are incorporated in a hazard level 3B location of a high optical power OFCS should have
received appropriate training in laser safety.
In high optical power systems, losses due to high power absorption can produce elevated
temperatures which cause damage and possible ignition. Therefore, those persons dealing
with optical components intended for use in high optical power systems, i.e. connectors,
attenuators, collimators, splices, etc., should have received appropriate laser safety training
according to IEC 60825-2 and IEC/TR 61292-4.
Instructions should be provided to personnel handling connectors in high optical power
systems. The following are examples:
Connector end-face: Do not touch connector end face, and clean each
connection with appropriate cleaning techniques.
Connection: Caution; note any anti-rotation keys or similar
locating features.
Dust cap: It is recommended that dust caps be removed
only during operation (to protect connectors from
contamination).
Bending and twisting: Exercise care when handling cables – avoid all
unnecessary bending and twisting. Take extra
care when (e.g.) unwinding cables from drums
Test/Check: Checks should be made for any contamination or
damage to connectors or fibre ends. A high
magnifying power viewing microscope (with
approved attenuating filters to eliminate the
possibility of eye exposure to unsafe levels of
optical radiation) or an indirect viewing instrument
should be used. Use only approved attenuating
direct viewing magnifying instruments.

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TR 60825-17 Ó IEC:2010(E) – 11 –
IEC 61300-3-35 provides guidance on end-face
inspection, and IEC/TR 62627-01 on cleaning.
NOTE It is the responsibility of the user, his or her
employer, the Laser Safety Officer or the manufacturer to
determine an appropriate level of attenuation.
Personal safety: It is recommended that high power lasers be
powered down before opening connectors or
commencing splicing procedures. The
recommendations of this document do not
supersede those in IEC 60825-1 or IEC 60825-2.
Front face of cable & connector protection: Where practical, power the laser off. Exercise
care when cleaning.
When optical instruments or viewing optics are not used, devices classified as 1M are
considered safe under the conditions indicated in IEC 60825-1. However, they may be
hazardous if the user employs non-attenuating optical instruments or viewing optics within the
beam. It is recommended to use indirect viewing instruments in all cases.
The laser radiation hazards present in high optical power systems and detailed safety
precautions necessary to prevent exposure to hazardous laser radiation should be contained
in the user manual and installation instructions.
4.4 Fibre and connector damage induced by high optical powers
4.4.1 Fibre fuse and other effects
Optical connectors can fail in high optical power transmission systems as the end surface of
the glass core of the optical fibre can be destroyed due the very high optical power density.
Exposure to high temperatures (potentially in excess of 1 000 °C) can cause a tension crack
and destroy the connector. Destruction of the fibr
...