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 60825-17:2015(E) 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 power optical fibre communication systems. It 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. This second edition cancels and replaces the first edition published in 2010. This edition constitutes a technical revision.

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Status
Published
Publication Date
08-Oct-2015
Current Stage
PPUB - Publication issued
Completion Date
09-Oct-2015
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IEC TR 60825-17
Edition 2.0 2015-10
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 60825-17:2015-10(en)
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IEC TR 60825-17
Edition 2.0 2015-10
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
ICS 31.260; 33.180.01 ISBN 978-2-8322-2959-0

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TR 60825-17:2015 © IEC 2015
CONTENTS

FOREWORD ........................................................................................................................... 3

INTRODUCTION ..................................................................................................................... 5

1 Scope .............................................................................................................................. 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 Fibre coating damage occurring when bending at high powers ................................ 8

4.3 Information on automatic power reduction (APR) .................................................... 9

4.4 Information for manufacturers, operating organizations and users ......................... 10

4.5 Fibre and connector damage induced by high optical powers ................................ 11

4.5.1 Fibre fuse and other effects ........................................................................... 11

4.5.2 Contamination particles ................................................................................. 12

4.6 Degradation or burn-through of dust cap and/or shutter ........................................ 12

4.7 Potentially collimated beam profile resulting in an increased optical hazard .......... 12

4.7.1 General ......................................................................................................... 12

4.7.2 High power expanded beam connectors ........................................................ 13

4.8 Increases in the temperatures of attenuators, collimators, splitters and other

passive components ............................................................................................. 13

4.9 Additional labelling ................................................................................................ 14

Bibliography .......................................................................................................................... 15

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IEC TR 60825-17:2015 © IEC 2015 – 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

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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an 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) 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 TR 60825-17, which is a Technical Report, has been prepared by IEC technical
committee TC 76: Optical radiation safety and laser equipment.

This second edition cancels and replaces the first edition published in 2010. This edition

constitutes a technical revision.

The changes with respect to the previous edition include changes to harmonize with SC86A

and SC86B documents.
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– 4 – IEC TR 60825-17:2015 © IEC 2015
The text of this Technical Report is based on the following documents:
Enquiry draft Report on voting
76/510/DTR 76/526/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 website under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
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IEC TR 60825-17:2015 © IEC 2015 – 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 but not exclusively 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 – IEC TR 60825-17:2015 © IEC 2015
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 power optical fibre communication systems.

This part of IEC 60825 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 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 60825-1:2014, Safety of laser products – Part 1: Equipment classification and

requirements

IEC 60825-2:2004, Safety of laser products – Part 2: Safety of optical fibre communication

systems (OFCS)
IEC 60825-2:2004/AMD1:2006
IEC 60825-2:2004/AMD2:2010

ITU-T Recommendation G.664, Optical safety procedures and requirements for optical

transmission systems
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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

feature of an optical fibre communication system (OFCS) by which the accessible power is

reduced to a specified level within a specified time, whenever there is an event which could

result in human exposure to radiation, e.g. a fibre cable break
___________

A consolidated edition 3.2 exists, including IEC 60825-2:2004 and its Amendment 1 and Amendment 2.

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IEC TR 60825-17:2015 © IEC 2015 – 7 –

Note 1 to entry: The term “automatic power reduction” (APR) used in this document encompasses the following

terms used in recommendations of the International Telecommunication Union ITU:
– automatic laser shutdown (ALS);
– automatic power reduction (APR);
– automatic power shutdown (APSD).
[SOURCE: IEC 60825-2:2004, 3.2]
3.3
controlled location
location with controlled access

accessible location where an engineering or administrative control is present to make it

inaccessible, except to authorized personnel with appropriate laser safety training

[SOURCE: IEC 60825-2:2004, 3.13]
3.4
hazard level

potential hazard at any accessible location within an OFCS, based on the level of optical

radiation which could become accessible in a reasonably foreseeable event, e.g. a fibre cable

break

Note 1 to entry: It is closely related to the laser classification procedure in IEC 60825-1.

[SOURCE: IEC 60825-2:2004, 3.4, modified — Supplementary information has been moved

from the definition to a Note to entry.]
3.5
high optical power

optical power of 500 mW or greater potentially capable of causing damage to fibres, optical

components or systems (typically Class 4)

Note 1 to entry: 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 to entry: Studies have shown damage is significantly more likely at powers in excess of 1 W, but damage

has also been shown to occur at powers as low as 200 mW – see [1] and [2] .
3.6
loss of continuity of an optical link

event which may cause hazardous optical power levels to be emitted from some point along

the path of an optical transmission system

Note 1 to entry: Common causes of loss of continuity of an optical link are a cable break, equipment failure,

connector unplugging, etc.
3.7
optical fibre communication system
OFCS

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
[SOURCE: IEC 60825-2:2004, 3.18]
___________
The numbers in square brackets refer to the Bibliography.
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– 8 – IEC TR 60825-17:2015 © IEC 2015
3.8
restricted location
location with restricted access

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
[SOURCE: IEC 60825-2:2004, 3.14]
3.9
unrestricted location
location with unrestricted access

accessible location where there are no measures restricting access to members of the

general public
[SOURCE: IEC 60825-2:2004, 3.15]
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 [3]):

• fibre fuse and its propagation;
• loss-induced heating at connectors or splices;
• connector end-face damage induced by dust/contamination;
• fibre coating burn/melt induced by tight fibre bending.
4.2 Fibre coating damage occurring when bending at high powers

Studies [4–12] 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. [6] 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-T Recommendation G.657

specifications and IEC product specification IEC 60793-2-50, category B6 fibres – are a

possible solution (see Section 2.5 in [7] and Subclause 4.5.3.2 of IEC TR 62547:2013).

However, for extreme situations more resilient coatings may also be required.
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IEC TR 60825-17:2015 © IEC 2015 – 9 –

The long-term damage effects of high power in other optical components, described for

example in 4.7, show the need to consider the implications of high power damage research,

as discussed in IEC TR 62547.

Well documented experiences of the ageing of coatings of fibres in tight bends under high

power have shown that catastrophic effects can occur after hundreds of hours [3]. Coating

ageing has been seen to be the trigger for catastrophic failure; the use of thermal imaging

cameras as described by Bigot-Astruc, M et al. [6] and in IEC TR 62547 has shown that

equilibrium temperatures can be a good indicator of lifetime and such cameras can be used to

reduce the time required for high power evaluation and damage testing. Also, note that the

rate of fibre coating ageing is usually temperature dependent, thus ambient environmental

conditions may affect component resilience – see Sikora et al [8].
4.3 Information on 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. OFCSs employing high optical power may necessitate the incorporation of

APR within one section of a main optical path in the event of recovery from the loss of optical

power or loss of continuity of an optical link within that particular section.

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).

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 power present in both

directions on the optical path, as described in the following excerpts reproduced with

permission from Recommendation ITU-T G.664 (10/2012):

“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

---------------------- Page: 11 ----------------------
– 10 – IEC TR 60825-17:2015 © IEC 2015

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,

i.e. "Automatic power reduction (APR) and restart pulses" and "Disabling of the APR".

4.4 Information for manufacturers, operating organizations and users

Due to the potentially increased hazards arising from higher optical powers, additional user

information may be needed. 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.

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. 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, i.e. restricted

or unrestricted location (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.

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

should be allowed to operate high optical power OFCS.

The operating organization should provide appropriate training in laser safety for 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.

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.

The following instructions are relevant to fibres carrying high optical powers and can be used

in addition to already published documents which could include IEC 60825-2, IEC TR 62547

and IEC TR 62627-01. Instructions should be provided to personnel handling connectors in

high optical power systems. The following are examples.
---------------------- Page: 12 ----------------------
IEC TR 60825-17:2015 © IEC 2015 – 11 –
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: Refer to IEC TR 62547.
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.
IEC 61300-3-35 provides guidance on end-face inspection and
IEC TR 62627-01 on cleaning.
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 and Where practical, power the laser off. Exercise care when
connector protection: cleaning.

When optical instruments or viewing optics are not used, devices of hazard level 1 or 1M are

considered safe to the retina but risks to the anterior parts of the eye or cornea may exist.

Additionally,
...

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