Personnel may drill an array or series of holes (in a floor space for example). Operators follow along with the fiber-optic device(s) making quick assessments.

With the improving technic and the emergence of more and more advance research production, fiber Bragg grating (FBG) had become one of the most successful optic passive device.

Special attention was put on production of millimeter wave, choice of optoelectronic device, architecture of down and up fiber optic links, etc.