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Modern information security

Receiving of hidden optical signals of a visible spectrum

Volodymyr Brailovsky, Michael Ivanchuk, I. V. Pyslar, Marharyta Rozhdestvenska, V. O. Pshonnik

Published Jan 1, 2019• 0 citations
Publisher

Abstract

ПРИЙМАННЯ ПРИХОВАНИХ ОПТИЧНИХ
DOI
10.31673/2409-7292.2019.024753

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We observe optical sideband interference using an optical IQ modulator at the transmitter and a Mach-Zehnder modulator at the receiver. We measure 82% interference visibility in back-to-back configuration and 71% interference visibility over 25 km optical fiber channel. We also show the simulation of optical sideband interference using IQ modulator and Mach-Zehnder modulator. We measure 77% visibility by simulation in back-to-back connection of transmitter and receiver. We study the effect of the linewidth of the laser on the optical spectrum of the sideband. We derive expressions for sideband power as a function of the applied phase difference between transmitter and receiver in the presence of chromatic dispersion in the fiber.
We propose and experimentally demonstrate an optical steganography method in which a data signal is transmitted using amplified spontaneous emission (ASE) noise as a carrier. The ASE serving as a carrier for the private signal has an identical frequency spectrum to the existing noise generated by the Erbium doped fiber amplifiers (EDFAs) in the transmission system. The system also carries a conventional data channel that is not private. The so-called "stealth" or private channel is well-hidden within the noise of the system. Phase modulation is used for both the stealth channel and the public channel. Using homodyne detection, the short coherence length of the ASE ensures that the stealth signal can only be recovered if the receiver closely matches the delay-length difference, which is deliberately changed in a dynamic fashion that is only known to the transmitter and its intended receiver.
The low-cost small aperture commercial optical ground stations (OGSs) will play an important role in the realization of a global scale satellite-to-ground quantum key distribution (QKD) networks. OGSs with < 60 cm diameter telescope and a small mount, can have stringent size and weight limits on the payload that can be accommodated. In order to ensure easy integration with an OGS, we have designed and produced a 40×30×10 cm receiver module which comprises polarization detection optics, fine point and track (PAT) subsystem and coarse wavelength division multiplexing optics for receiving optical signals over the visible, near-infrared and infrared spectrum. The tracking capability of the module to track multiple beams of different wavelength is evaluated in an emulated beam-wander induced free-space link. The receiver module is characterized for transmission loss and polarization extinction ratio (PER) by sending an 844 nm collimated beam to the module in a 3 m free-space link and measuring the power coupled into the four single mode fibers (SMF) for H, V, D and A polarized components. Furthermore, we have used the receiver module in our satellite-to-ground QKD emulator and have measured the secure key that can be generated within different maximum elevation satellite overpasses when the quantum signal is coupled into AR-coated SMF. Such modules can be incorporated into optical ground stations (OGS) to mitigate atmospheric beam-wandering and coarse misalignment while allowing wavelength division multiplexing of multiple visible, near-infrared and infrared beams to enable co-propagation of classical and quantum communication beams for real-time QKD.