Fiberoptic measurements

Using the long-known principle of light fountains, optical fibers - thin, highly transparent hairs of glass - were first used for decorative purposes, then for more utilitarian applications (lighting, endoscopy), before undergoing spectacular development in the field of telecommunications since the late 1970s. Already proposed by theorists (Charles Kao in 1966, who was awarded the Nobel Prize for Physics in 2009), this development has been made possible by the mastery of semiconductor laser diodes, advances in optical fiber manufacturing technology, enabling very low attenuation and sufficient mechanical strength, and the development of cables, connectors, passive components and connection processes.

The successive introduction of wavelength-division multiplexing, optical amplification, optical switching, coherent transmission and polarization multiplexing techniques, and now mode-division multiplexing, have enabled transmission capacities to explode and have supported the deployment of the Internet, with fiber speeds rising in 30 years from 560 Mbps (TAT8 transatlantic link in 1988) to several tens of Tbps.

With unrivalled qualities in terms of attenuation (the theoretical limit of 0.16 dB/km at 1,550 nm was practically reached years ago) and bandwidth, optical fibers are also remarkably lightweight, flexible, non-corrosive, electrically insulated and, above all, insensitive to electromagnetic interference - and therefore safe, which has led to applications in a wide variety of fields. Alongside spectacular applications such as submarine links (over a million km of cable carrying over 98% of the world's traffic) and FTTH networks (fiber to the home, with several hundred million subscribers worldwide), not forgetting terrestrial networks where they have supplanted other media, optical fibers are being massively deployed in local corporate networks and embedded networks (networks where multimode fibers are still used). And far from being out-competed by mobile networks, they are playing an essential role in the deployment of antennas for 4G and 5G networks. Finally, the introduction of optical fibers has been shown to significantly reduce network energy consumption.

However, the qualities of these fibers open up other applications in a wide range of fields: automotive, aeronautics, medicine, robotics, automation, lighting, imaging (endoscopy), and the transport of even high-power laser beams. In particular, fiber optic instrumentation and sensors have moved out of the laboratory and are widely used in civil engineering, structural monitoring, avionics, medicine, nuclear energy, physico-chemical analysis, and more.

All these applications have naturally required progressive standardization of optical fibers, mainly...