Basics of incoherent and coherent digital optical communications

C. Bendjaballah, Osamu Hirota, Serge Reynaud

Bernard B. Wu, Anjali Agrawal, Ivan Glesk +3 more

Stealth communication using coherent SPE-OCDMA is demonstrated. The coherent approach can provide higher spectral efficiency than incoherent optical CDMA.

Murat Azizoá ̧¡lu

Черёмхин Павел Аркадьевич, Vitaly V Krasnov, Vladislav G. Rodin +1 more

Abstract Optical encryption is an actively developing field of science. The majority of encryption techniques use coherent illumination and suffer from speckle noise, which severely limits their applicability. The spatially incoherent encryption technique does not have this drawback, but its effectiveness is dependent on the Fourier spectrum properties of the image to be encrypted. The application of a quick response (QR) code in the capacity of a data container solves this problem, and the embedded error correction code also enables errorless decryption. The optical encryption of digital information in the form of QR codes using spatially incoherent illumination was implemented experimentally. The encryption is based on the optical convolution of the image to be encrypted with the kinoform point spread function, which serves as an encryption key. Two liquid crystal spatial light modulators were used in the experimental setup for the QR code and the kinoform imaging, respectively. The quality of the encryption and decryption was analyzed in relation to the QR code size. Decryption was conducted digitally. The successful decryption of encrypted QR codes of up to 129 × 129 pixels was demonstrated. A comparison with the coherent QR code encryption technique showed that the proposed technique has a signal-to-noise ratio that is at least two times higher.

Daniel O. Bezerra, João Paulo Amaral, E. J. S. Fonseca +2 more

Coherent optical vortices have promising applications in quantum and classical optical communication. They add new degrees of freedom to code information. In this context, to implement a tool enabling sorting of spatially multiplexed vortex states is fundamental. By other hand, spatially incoherent vortices can be more robust in propagation through noise media, such as turbulent atmosphere or obstacles that block part of the light. Therefore, in this work we propose directly applying a high-resolution sorting scheme to spatially incoherent vortex states.

Murat Azizoğlu