IEC 60825-2:1993/AMD1:1997

Amendment 1 - Safety of laser products - Part 2: Safety of optical fibre communication systems

Amendement 1 - Sécurité des appareils à laser - Partie 2: Sécurité des systèmes de télécommunication par fibres optiques

General Information

• Status: Published
• Publication Date: 10-Dec-1997
• ICS: 31.260 - Optoelectronics. Laser equipment
• ICS: 33.180.01 - Fibre optic systems in general
• Technical Committee: TC 76 - Optical radiation safety and laser equipment
• Drafting Committee: WG 5 - TC 76/WG 5
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 19-May-2000

Relations

• Revised: IEC 60825-2:2000 - Safety of laser products - Part 2: Safety of optical fibre communication systems
• Effective Date: 05-Sep-2023

Standards Content (Sample)

INTERNATIONAL
IEC
STANDARD
60825-2
AMENDMENT 1
1997-12
Amendment 1
Safety of laser products –
Part 2:
Safety of optical fibre communication systems
Amendement 1
Sécurité des appareils à laser –
Partie 2:
Sécurité des systèmes de télécommunication
par fibres optiques
 IEC 1997 Droits de reproduction réservés  Copyright - all rights reserved
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International Electrotechnical Commission
For price, see current catalogue

– 2 – 60825-2 Amend. 1  IEC:1997

FOREWORD
This amendment has been prepared by IEC technical committee 76: Optical radiation safety
and laser equipment.
The text of this amendment is based on the following documents:

FDIS Report on voting
76/162/FDIS 76/169/RVD
Full information on the voting for the approval of this amendment can be found in the report on
voting indicated in the above table.
___________
Page 3
CONTENTS
Add the titles of the following two new annexes D and E as follows:
D Application notes for the safe use of optical fibre communication systems
E Bibliography
Page 31
Add, after annex C, the new annex D as follows:
Annex D
(informative)
Application notes for the safe use of optical fibre communication systems

D.1 Introduction
This annex provides guidance on the application of IEC 60825-2 to specific practical situations.
This annex applies to optical fibre communication systems (OFCS) where optical power is
normally confined in a fibre and may be accessible at a great distance from the optical source.
It does not apply to optical fibre systems primarily designed to transmit optical power for
applications such as material processing or medical treatment.
It is an informative annex to assist OFCS operators in applying the requirements of IEC 60825-1
and IEC 60825-2 to their specific application. It does not contain any manufacturer or installer
requirements.
60825-2 Amend. 1  IEC:1997 – 3 –

D.2 Definitions
For the purpose of this annex D, the following definitions apply:

D.2.1
accessible location
a location anywhere in an optical fibre communications system where optical radiation might

become accessible in reasonably foreseeable circumstances

D.2.2
FITs:
an indicator of reliability defined as the number of failures per 10 h
D.2.3
HITs
the number of hazard incidents per 10 h
D.3 Areas of application
D.3.1 Typical optical fibre installations
a) Locations with controlled access (see 3.13):
cable ducts;
street cabinets;
manholes;
dedicated and delimited areas of network operator distribution centres;
test rooms in cable ships.
b) Locations with restricted access (see 3.14):
secured areas within industrial premises not open to the public;
secured areas within business/commercial premises not open to the public
(for example telephone PABX rooms, computer system rooms, etc.);
general areas within switching centres;
delimited areas not open to the public on trains, ships or other vehicles;
overhead fibre optic cables and cable drops to a building;
optical test sets.
c) Locations with unrestricted access (see 3.15):
domestic premises;
industrial commercial or business premises;
public areas on trains, ships or other vehicles;
open public areas such as parks, streets, etc.
Distributed fibre networks may pass through unrestricted public areas (for example in the
home), restricted areas within industrial premises, as well as controlled areas such as cables
ducts or street cabinets.
OFCS Local Area Networks (LANs) may be deployed entirely within restricted business
premises.
– 4 – 60825-2 Amend. 1  IEC:1997

Fibre systems may be entirely in unrestricted domestic premises such as hi-fi interconnections.

Infra-red (IR) wireless LANS are outside the scope of this annex.

D.3.2 Typical hardware components

a) Fibre cables: single/multiple/ribbon construction;

single/multimode;
carrying single/multiple wavelengths;

uni/bidirectional, fibre;
communications/power feeding.
b) Optical sources: LEDs, communications lasers, pump lasers, optical amplifiers,
bulk/distributed, continuous/low/high-frequency emission.
c) Connectors: permanent/semi-permanent, single/multiple.
d) Power splitters, wavelength de/multiplexers, attenuators.
e) Enclosures and protective housings.
f) Fibre distribution frames.
D.3.3 Typical conditions
a) Installation.
b) Operation.
c) Maintenance.
d) Servicing.
e) Fault.
f) Measurement (including optical time domain reflectometry – OTDR).
D.4 Optical fibre power system limits
Mean power fibre limits for the laser classes are presented below at various wavelengths in the
optical fibre. For most typical systems with duty cycles of between 10 % to 100 %, the peak
power can be allowed to increase as the duty cycle decreases. However, for duty cycles
of ≤ 50 %, it is most straightforward to limit the peak powers to twice these mean power limits,
although IEC 60825-1 can be used for a more sophisticated analysis in order to identify any
increase in peak powers permissible for these types of systems.

D.5 Hazard level evaluation examples
NOTE – For optical sources, enclosures and protective housings already classified according to IEC 60825-1 by the
manufacturer, the hazard level according to IEC 60825-2 may be different from the classification according to
IEC 60825-1. The reasons for these differences are:
– IEC 60825-2 has a hazard level k × 3A for restricted and controlled access situations;
– operator uses automatic power reduction (APR) for determination of the hazard level;
– results from fault analysis in IEC 60825-2 may be different from single fault analysis in IEC 60825-1.
D.5.1 Multiple wavelengths over the same fibre
When more than one wavelength is used on the same fibre, such as on a wavelength division
multiplex system (WDM), then the hazard level depends on both the power levels and whether
the wavelengths are additive. For skin exposure to wavelengths usually used in optical fibre
communication systems, the hazards are always additive. For most fibre systems, 1 400 nm is
the point at which addition conditions change:

60825-2 Amend. 1  IEC:1997 – 5 –

a) if two wavelengths are both below 1 400 nm they add, i.e. the combined hazard is higher;

b) if two wavelengths are both above 1 400 nm they add, i.e. the combined hazard is higher;

c) if one is above 1 400 nm, and one below, then retinal hazards do not add, i.e. the combined

hazard does not increase.
It is necessary to calculate separately for skin and retinal hazards. To calculate the combined

hazard level in a multi-wavelength system, it is necessary to calculate the system power at

each wavelength as a proportion of the AEL for that class at that wavelength (for example

25 %, 60 %, etc. up to 100 %), and add together. If the totalled proportion exceeds 1 (100 %),

then the hazard level exceeds that class.

Multi-wavelength example
An optical transmission system using multimode fibre of 50 micrometres core diameter and a
numerical aperture 0,2 ± 0,02 carries six optical signals: at wavelengths of 840 nm, 870 nm,
1 290 nm, 1 300 nm, 1 310 nm and 1 320 nm. Each of these signals has a maximum time-
averaged power of –8 dBm (0,16 mW). Determine the location hazard level at the transmitter
site.
In the absence of any other information concerning the transmitter emission duration when a
connector is removed, assume that no shut-down system operates, and classify on the basis of
the power levels accessible at the transmitter connector (removing the connector is a
reasonably foreseeable event).
Assess on the basis of:
100 s emission duration (see 9.3 e) of IEC 60825-1), and
a minimum viewing distance of 100 mm (see 8.2 c) of IEC 60825-1).
Table 5 of IEC 60825-1 indicates that the effects of all wavelengths are additive. The
evaluation must therefore be made on the basis of the ratio of the accessible emission at each
wavelength to the AEL for the laser class at that wavelength (see 9.3b) of IEC 60825-1).
Note, however, that the AELs are constant in the wavelength range 1 200 nm to 1 400 nm;
hence, the four signals in the vicinity of 1 300 nm may be considered as a single signal with a
power level equal to the sum of powers in those signals.
First compare the emission levels with the AEL for class 1:
–4 0,75
AEL = 7 × 10 t C C J
840 nm or 870 nm 4 6
–4
–0,25
= 7 × 10 t C C W
4 6
0,002(λ – 700)
where C = 10
and for a point source, C = 1
–3 0,75 –3 –0,25
AEL = 3,5 × 10 t C C J = 3,5 × 10 t C C W
1 300 nm 6 7 6 7
where C = 8
hence AEL = 0,42 mW
840 nm
AEL = 0,49 mW
870 nm
AEL = 8,9 mW
1 300 nm
– 6 – 60825-2 Amend. 1  IEC:1997

Using the expression for the diameter of the beam from an optical fibre (equation (1) in A.6
of IEC 60825-1), the diameter at the 63 % (1/e) points for the smallest NA fibre (worst case) is:

××
2 Nr A 2 100 0,18
d = = = 21,2 mm
1,7 1,7
The fraction of the beam that would pass through the 50 mm aperture specified in the
measurement conditions is therefore (using equation (3) of example A.6 of IEC 60825-1):

η = 1 – exp(– [d /d ] ) = 0,99
a 63
Thus, in this case, all of the fibre power would be collected by the 50 mm aperture, and no
correction is needed.
Summing the ratios of the power at each wavelength to the corresponding AEL yields:
(Power) 0,16 0,16 4 × 0,16
= + + = 0,78
∑  
 AEL  0,42 0,49 8,9
This ratio is less than 1; thus, the accessible emission is within class 1 limits and a location
hazard level 1 applies.
D.5.2 Bi-directional (full duplex) transmission
There is no additive effect from each separate direction of transmission, as each broken fibre
cable end represents a separate hazard if the fibre breaks. The hazard level is determined by
the transmission direction with the higher power.
D.5.3 Automatic power reduction
Automatic power reduction is an available option for optical fibre communications systems in
order to classify an end to end OFCS at a lower hazard level than the laser/LED power of that
system would otherwise permit. This is important when the hazard level of the internal optical
transmitters of a system may put a limitation on where that system may be deployed.
See annex B.
Following the indications of this standard, assessment of the hazard level shall take place at
the time of reasonably foreseeable human access to radiation (for example after a fibre break)
unless measurement at a later time would result in a larger exposure (see 4.4.1). This could be
almost instantaneously after an unprotected fibre splice, after approximately 1 s after a fibre
connector disconnect, or after several hours as in the time it takes for a ship to pull up a

broken cable from the bottom of the ocean.
Automatic power reduction should not take the place of good work practices and proper
servicing and maintenance. Also, the reliability of the APR mechanism shall be taken
into account when assessing the hazard level.
Automatic power reduction cannot be regarded as a universally protective measure because after a
fibre break, it is common practice to use an optical test set (usually an optical time domain
reflectometer, OTDR) to determine the location of the break. This instrument launches laser power
down the fibre under test. Therefore, even if the normal telecommunications transmitter is shut
down or removed, the diagnostic tools may impart laser power at a later time.
These OTDRs typically operate at class 1, so no potential hazard is present. However, higher
power may require class 3A or class 3B OTDRs to detect the break. Also, OTDR signals may
be amplified to a higher class if sent through an optically amplified system.

60825-2 Amend. 1  IEC:1997 – 7 –

It is also important that the laser safety professionals of the OFCS operator consider the
hazard level under which it is desirable to work. Hazard level 3A or k × 3A is often cited
because workers would be trained not to use any optical (collimating) instruments that would

increase the hazard and typically they would have no need to examine the fibre at a close

range. Hazard level 3B is acceptable in controlled environments with proper labelling and

connector conditions.
This subclause will examine APR under several circumstances:

– on a readily accessible fibre in a splice tray;

– at a fibre optic connector;
– on a fibre not readily accessible in a submerged/buried cable;
– in restricted and unrestricted environments;
– ribbon cables.
For these tables, the following upper limit powers are calculated for the typical wavelengths
using worst case singlemode fibre (see clause D.4):
1 300 nm: hazard level 1 = 8,85 mW
hazard level 3A = 24 mW
hazard level k × 3A = 83 mW
hazard level 3B = 500 mW
1 550 nm: hazard level 1 = 10 mW
hazard level 3A = 50 mW
hazard level k × 3A = 54 mW
hazard level 3B = 500 mW
D.5.3.1 Fibre in a splice tray
As powers increase in an OFCS, it is important that splicing operations on potentially energized
fibres of hazard level 3B or greater powers take into consideration the safety of the operator,
and a fully enclosed splicing system should be employed. If splicing is not to take place in a
protective enclosure, automatic power reduction is an option for reducing the hazard level and
therefore the exposure. Because accessibility to the cut fibre is immediate, power reduction
should also be immediate. Table D.2 outlines some timing requirements at typical wavelengths.
D.5.3.2 Connectorized systems

Another area where access to energized fibre is reasonably foreseeable, is when an energized
system has one or several of its fibres disconnected at an optical connector. A possible and
likely assumption that could be made is that human accessibility to the energized fibre would
not occur until 1 s after the disconnection. As a result, the power reduction durations specified
in table D.2 would be increased by 1 s for this application.
However, another alternative that would result in a safer hazard classification for the
transmission equipment itself would be the use of shuttered connectors. These connectors,
provided that they meet the reliability characteristics outlined in clause D.6 of this annex, could
be a mechanical solution that could be implemented at any connector point along the OFCS.
Such a solution would be desirable for controlling exposures from unmated connectors. These
shutters should operate within the time restrict
...