Is it dangerous to look into an optical fibre? It depends on what is upstream

“Can you look into a fibre?” The question always comes up, and it gets one of the two wrong answers: “no, you will burn your retina” or “relax, it is a strand of glass”. Neither helps anyone about to open a splice closure on a live cable. The useful answer is that it depends on what sits upstream: in Italy, establishing that is not prudence but a duty with a penalty attached.

While the fibre stays closed, the system is Class 1.

This is where the misunderstanding that breeds all the others begins. Under normal conditions an optical link is fully enclosed radiation: read the product standard strictly and almost any system would come out as Class 1, that is, safe. ITU-T G.664 (10/2012), which reproduces the text of IEC 60825-2 under licence, adds the sentence that carries the whole article: it is not until the fibre breaks or a connector is unplugged that someone might be exposed to a potentially hazardous level, if the emitters or amplifiers upstream are powerful enough.

Two standards, and the second overrides the first.

The base reference is IEC 60825-1:2014, edition 3.0 of 15 May 2014, Safety of laser products – Part 1: Equipment classification and requirements, in force (stability date 2027). It covers 180 nm to 1 mm and sets out Classes 1 to 4, with the 1M, 2M and 3R variants and Class 1C, added by edition 3. We are not quoting the emission tables — the standard is paywalled — but the criterion is public: classification rests on the accessible emission level under reasonably foreseeable conditions, single fault included, looking only at harm to the eyes and skin.

For an installation, Part 1 is not enough. IEC 60825-2:2021, edition 4.0 of 16 March 2021, Safety of laser products – Part 2: Safety of optical fibre communication systems (OFCSs), replaces the 2004 edition with its 2006 and 2010 amendments and requires the hazard level to be assessed at each accessible location, as a replacement for product classification. The object is the installed system as an end-to-end assembly, and responsibility is split by role: manufacturer, installer, service and operating organisations.

Three kinds of location, and power that restarts by itself.

Part 2 divides accessible locations into three categories — unrestricted, restricted and controlled — each with its own marking and requirements. G.664 states the ceiling: hazard level no higher than 1M in restricted locations, 3B in controlled ones, and 1 for the parts of access networks in unrestricted locations. Mind the edition: G.664 dates from 2012 and cites the 2010 version of IEC 60825-2, whereas the 2021 edition technically revised that clause and is paywalled. The criterion holds: the ceiling depends on who can reach that point.

Where power exceeds it, automatic power reduction (APR) comes in: the system detects the loss of continuity — cut cable, unplugged connector, fault — and drops the power. G.664 recommends APR procedures with automatic restart, and that is the line anyone opening a closure needs to know: a system that comes back on by itself the moment continuity returns is not off. IEC 60825-2 devotes a subclause to disabling the APR.

In Italy the same subject has its own title of law.

This is the part almost nobody connects. Legislative decree 9 April 2008, no. 81, Title VIII, Chapter V — articles 213 to 218 — protects workers from artificial optical radiation, “with particular regard to the risks due to harmful effects on the eyes and the skin” (art. 213). Article 214 defines optical radiation between 100 nm and 1 mm and separates the IRA (780-1400 nm) and IRB (1400-3000 nm) bands: the 1310 nm and 1550 nm of a backbone fall into two different bands. Exposure limit values for laser radiation sit in Annex XXXVII, part II (art. 215).

The hinge is article 216. Paragraph 1: the employer assesses and, “where necessary, measures and/or calculates” the levels, using a methodology that “complies with the standards of the International Electrotechnical Commission (IEC) as regards laser radiation”. The reference to IEC sits inside Italian law, and paragraph 2, letter l), repeats it: among the elements to be considered is “a classification of lasers established in accordance with the relevant IEC standard”. Paragraph 3 requires the risk assessment document to spell out the measures under articles 217 and 218: an action programme where limits may be exceeded, signage and restricted access (art. 217, paragraph 2), health surveillance “as a rule once a year” (art. 218). Information and training sit in article 184, which also covers the limit values of Chapter V.

The penalties are in the following chapter. Article 219 punishes the employer — and, under paragraph 2, the manager too — with three to six months’ arrest or a fine of 2,500 to 6,400 euro for breaching article 216 (paragraph 1, letter a), 2,000 to 4,000 euro for article 217, paragraph 1, and 750 to 4,000 euro for articles 184 and 217, paragraphs 2 and 3 (paragraph 2, letters a and b).

Where the risk actually sits.

Not in “looking at the fibre”, but in three situations: an open fibre with the source live upstream; the use of optical inspection instruments, which bring the eye close and concentrate; and work inside a splice closure on a live cable, where the fibres passing through are not yours. Position in the network changes everything: a multiplexed or amplified run adds up channels and pumps, an access network does not. And G.664 notes that at high powers a fire can start from local heating in a contaminated connector: a dirty end-face is not only a testing problem.

What to demand in the specification.

This article informs: it does not replace the risk assessment or the training, which remain the employer’s responsibility. Anyone commissioning work on a live network is, however, entitled to ask in writing for:

the hazard levels of the accessible locations involved, assessed to IEC 60825-2:2021, with the location type stated;
the written procedures for taking the link out of service and back into service: who authorises, how the absence of power is verified, how the APR is handled;
documented training for whoever opens joints and closures, consistent with articles 184 and 216;
signage and demarcation of the area where the case requires it (art. 217, paragraph 2);
suitable instruments, with optical inspection on a de-energised source as a written rule.

The point.

The right question is not “how dangerous is it”, but “who has written down, for this point of the network, how much power runs through it and who switches it off”. It is one line of documentation, and in most specifications it is missing. That is why, in the work we carry out, the state of the link and the consent to proceed are part of the record, not a verbal agreement.

Commissioning work on a live network? Talk to us: settling up front who switches off, who verifies and who switches back on costs less than an accident to explain.