CVQKD using iXblue Modulators and matching RF amplifiers
Modern society relies heavily on private telecommunications. Among the many activities that depend on it are e-banking, e-health, or secure government communications. However, modern encryption techniques used to establish privacy have limitations as they rely most often on the supposition that an eavesdropper has access to a limited computational power. This supposition depends on whether the eavesdropper is an individual or a state agency. Also, his computational power may be much larger in a decade (20-years-old communications are much easier to decrypt nowadays).
Quantum Key Distribution (QKD) offers a forever privacy guaranteed by the laws of physics. A spy trying to intercept some information is detected before a message is even sent. And this is achieved simply by adapting the emitter and receiver hardware of an optical link (no need to send guards all along your optical fiber).
In practice, QKD is achieved with optical telecommunication links, either via optical fibers or the propagation of light in vacuum (or the atmosphere) for satellite links where iXblue modulators are used.
An example of Continuous Variable QKD (CVQKD) is given. The information is encoded in both the amplitude and the phase of laser pulses using iXblue solutions: two amplitude modulation blocks AM1 and AM2 are cascaded with a phase modulation PM1.
Fig. 1: CV-QKD emitter and receiver
BS: Beam Splitter, AM: Amplitude Modulation, PM Phase modulation, AMP: RF Amplification stage,
AWG: Arbitrary Waveform Generator, SMF28: Single Mode Fiber, BHD: balanced homodyne detectors
Using an AWG, a first modulation block AM1 is used to generate short optical pulses. Using iXblue NIR-MX800, MXER1300 and MXER high contrast and wide bandwidth amplitude modulators, very short optical pulses width from 70 ps can be achieved at 850 nm, 1310 nm and 1550 nm respectively. The modulator is combined with the driver DR-VE-10-MO which can be set either as a limiting or linear amplifier for either square or gaussian pulse waveforms. Using iXblue bias controller MBC-DG-LAB, a high pulse contrast stability is obtained for frequency repetition rates up to several GHz.
Fig. 2 : 70 ps optical pulse generate with the MXER-LN-10 combined with the DR-VE-10-MO
Fig. 3: Multi-level output driver DR-VE-10-MO versus electrical input level
A phase modulator PM1 sets the phase of each pulse. The MPZ-LN-01 (coming with more than 3 GHz electro-optical bandwidth) or the MPZ-LN-10 (typical 16 GHz of bandwidth) is used in combination with the driver The DR-AN-10-HO to continuously modulate the phave over the range 0 to 2π. For the O-Band operation, the MPZ-LN-10 is selected to operate at both wavelengths 1310 nm or 1550 nm. For 850 nm, NIR-MPX800-LN-05 (8 GHz bandwidth operation) or the NIR-MPX800-LN-10 (more than 16 GHz bandwidth) are used.
iXblue provides modulation solutions to QKD manufacturers and to research institutions. In addition to the solutions listed above, iXblue also offers polarization switches and pulse pickers. iXblue is also participating to the OpenQKD consortium. By offering dedicated modulators, bias controllers and RF drivers, pulse-pickers for receiver temporal pulse selection, iXblue is proud to contribute efficiently to the deployment QKD.
12 GHz VErsatile RF Amplifier