Free space communication


Free space optical communications (FSOC) offer very high data-rate links for a wide range of applications. However, the availability and reliability of long-range links are restricted by turbulence-induced fading. This is specifically the case when small aperture standard single-mode fibers are used to collect light.




TILBA: turbulence-mitigating optics for FSO receiver


TILBA by CAILabs is a unique passive optical component designed to increase light collection in free space optical communication and imaging systems in the presence of atmospheric turbulence. By using spatial mode diversity and enlarged numerical aperture, TILBA passively mitigates turbulence fading by collecting multiple spatial modes (in free space or multi-mode fibers), therefore increasing the link reliability in the case of strong turbulence. It is passive, compatible with standard telecom components and available in an airborne packaging.




TILBA is compatible with intensity-modulation direct-detection and coherent detection; it is a highly efficient solution that decreases the detection threshold at the FSOC receiver:


  • Link reliability improved to 99.7%
  • Passive optical system
  • Compatible with telecom standards
  • Airborne packaging





Demonstrated by our partners:


Adding up 6 spatial modes in direct detection improves the “coupling efficiency for the worst 5% case of the sum of the six modes […] by 7 dB compared to that of SMF”1


In coherent detection, using 3 spatial modes “relax the required transmitted power by 9 dB” in LEO-to-ground transmission with constant FEC compared to a single mode aperture.2


Reference: Demonstrated by NEC corporation in 1Arikawa & al, Sum. Top. (2016) & 2Arikawa & al, ECOC (2017)

Find out more about TILBA:

Tilba Product sheet