Handling optical cables: safety aspects

We found that it is very dangerous to stare directly at thQ free end of an optical cable excited by a GaAlAs laser or by a high radiance LED. We determined the minimum tolerable distance between the human eye and the cable end. In the case of a cable with one multimode fiber, the typical safety zone should be 1 m when using a laser light source and 15 cm when using an LED. In the case of a single mode fiber the critical distance is approximately two to four times as large as in the multimode case; however, when taking into account typical values of the power level in single mode fibers, the critical distance is approximately 1 m as well. For N fibers within the cable the critical distance agrees with that of the single fiber, provided that the fibers are not too closely packaged.