A fibre laser for transmitting secret information

XLIM has developed a 50 km fibre laser for the secure exchange of data. This so-called “ultra-long” type of laser presents new, original characteristics: its very long length “miniaturises” the spacing between the cavity modes and reduces them to a few kHz. One potential application is the transmission of secure data between the two ends of the laser. A system associated with a simple and inexpensive protocol has been designed, and it allows to data to be exchanged securely through a common laser operating at two indistinguishable configurations. This laser is well suited to the transmission of secret keys for private key encryption. Although the level of protection is less than for more complex systems based on quantum encryption, these ultra-long lasers can enhance security by using standard components at low cost

This work, completed in collaboration with the Aston Institute of Photonic Technologies in Birmingham, England, and El Instituto de Óptica du Consejo Superior de Investigaciones Científicas (CSIC) in Madrid, Spain, has been published in Light: Science and Applications, Nature Publishing Group.