Optical supply arrangement

Abstract

In an optical supply arrangement, a laser source () provides transmitted laser light down an optical supply line (). A first coupler (), remote from the laser source () along the optical supply line (), taps off a small proportion of the transmitted laser light to be returned along the optical supply line () to a photo detector () driving a monitor () and a controller (). If the monitor () detects that the photo detector () is experiencing a loss of return laser light, possibly due to a break in the optical supply line (), the monitor () causes the controller () to extinguish the laser source () in less time than escaping laser light can cause damage to property, person or eyesight. A first embodiment has the transmitted light on a transmission fiber optic () and the return laser light on a separate return fiber optic (). A second embodiment has the return laser light being sent back down the transmission fiber optic (). A reflective key (), monochromatic to the wavelength of the laser source, is selectably removable to disable the laser source () for maintenance or conditional access. The monitor () can operate on absolute levels, averages or rates of change to establish if a loss of transmission has occurred.