Are laser emissions from an open optical fiber less hazardous than MPES suggest?

Abstract

Two widely used fiber-optical communication wavelength bands correspond to bands where laser energy penetrates deeply into tissue and where ocular exposure limits are highest. These two bands are around 1550 and 1315 nm, or more specifically: 1530 nm – 1565 nm (“C-Band”) and 1260 nm – 1360 nm (“O-Band”). In the most recent (2013-2014) laser safety guidelines and standards, the spectral correction factor CC (C7 in IEC) was increased even more in the 1260-1360-nm band. The ocular MPE for viewing a CW (modulated or non-modulated) “point”-source at 1350 nm would now be 50 W·cm−2 if it were not limited by a corneal protection factor, which differs between ANSI Z136.1 and IEC 60825-1. And the AEL for Class 1 would be 19.5 W, except that this emission value is limited to the AEL for Class 3B, which is only 500 mW CW. The AEL for 1550 nm is only 10 mW despite the fact that the penetration depth and tissue-absorption volume is greatest at 1.55 μm compared to other wavelengths in the IR-B spectral band and this low power cannot be sensed by touch! The limits appear to be overly restrictive when compared to injury thresholds in the eye and skin.Two widely used fiber-optical communication wavelength bands correspond to bands where laser energy penetrates deeply into tissue and where ocular exposure limits are highest. These two bands are around 1550 and 1315 nm, or more specifically: 1530 nm – 1565 nm (“C-Band”) and 1260 nm – 1360 nm (“O-Band”). In the most recent (2013-2014) laser safety guidelines and standards, the spectral correction factor CC (C7 in IEC) was increased even more in the 1260-1360-nm band. The ocular MPE for viewing a CW (modulated or non-modulated) “point”-source at 1350 nm would now be 50 W·cm−2 if it were not limited by a corneal protection factor, which differs between ANSI Z136.1 and IEC 60825-1. And the AEL for Class 1 would be 19.5 W, except that this emission value is limited to the AEL for Class 3B, which is only 500 mW CW. The AEL for 1550 nm is only 10 mW despite the fact that the penetration depth and tissue-absorption volume is greatest at 1.55 μm compared to other wavelengths in the IR-B spectral band and this low...