Classifications of Fiber & Safety

Classifications of Fiber & Safety

| 9/15/2012 8:03:00 AM

Fiber Optic lasers fall into classifications based on the specifications by the IEC 60825-1 standard. The old standard was based on Roman numerals (I-IV) in the US and Arabic numerals (1-4) in the EU. Today the revised system uses Arabic numerals in all jurisdictions.

The classification of a laser is based on the concept of Accessible Emission Limits (AEL) that is defined for each laser class (defined in maximum power of mW); the classification is then identified with a warning label relevant to the hazard the laser may provide.

The following is a list of the current Classifications for lasers:

Class 1
Class 1M
Class 2
Class 2M
Class 3R
Class 3B
Class 4

Class 1 is safe under all conditions of normal use. Ethernet equipment commonly uses Class 1, and it is further denoted as “eye-safe”. Support documentation such as manuals or data sheets list this important information about the lasers.
Laser Radiation Class 1 Laser Product Label

Class 1M is safe for all conditions except when passed through a magnifying optic such as a microscope or telescope. Class 1M lasers produce large-diameter beams. This type of laser is not used on Ethernet equipment and the label below must be affixed to the product.
Warning Label for Class 1M

Class 2 Lasers & above must have the warning label below visibly located on products.
Laser Radiation Class 2 Laser Product Label

Class 2 lasers can be treated as "safe" because of the (eye) blink reflex, if not viewed through optical instruments. Class 2 is limited to an AEL value of 1mW. Many laser pointers and measuring instruments are Class 2. However, precaution is still advised and labeled as such.

Class 2M lasers are also "safe" due to the blink factor; as with Class 1M, it applies to laser beams with a large diameter, for which the amount of light cannot exceed the limits for Class 2. To summarize, handling Class 2 lasers is safe, but viewing directly poses a danger to the human eye.
Laser Radiation Class 2M Laser Product Label

Class 3R lasers have a low risk of injury, and it can be considered safe if carefully handled. Laser sights for firearms fall in this category. It has an AEL value of 5mW.
Class 3R Laser Product Label

Class 3B is hazardous to the eye if exposed directly, but can be viewed if the reflection is bounced off paper or a matte surface; protective eyewear is usually required; it’s AEL value is 30 mW.

Class 3B lasers are used inside CD and DVD writers.
Laser Radiation Class 3B Laser Product Label

Class 4 lasers are the highest and most dangerous class of lasers; it’s AEL value exceeds all Class 3 lasers. It can burn the skin, cause permanent eye damage; even ignite combustible materials. Most industrial, scientific, military and medical lasers fall into this category.
Laser Radiation Class 4 Laser Product Label

In conclusion, the Classifications of fiber are relevant to the industries and types of equipment. The Classifications of fiber is the same, regardless of its form factor, ie, fixed transceivers or SFPs.

This brings me to the topic of Automatic Laser Shut off (ALS) for SFPs. ALS is a diagnostic function that will be triggered when a TX fault occurs, in other words, if the transmit side of the fiber fails, the laser will shut down. Some vendors will market this as an important safety feature for SFPs that can be installed in Ethernet equipment. However, as discussed above, Ethernet equipment uses Class 1, Eye-safe lasers, so safety is just not an issue. ALS is basically an indicator for a failure on the fiber segment.

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