Electro-optical intensity modulator closed-loop control system and method in quantum key distribution system

Abstract

The invention discloses an electro-optical intensity modulator closed-loop control system and method in a quantum key distribution system. The electro-optical intensity modulator closed-loop control system comprises a laser device, an electro-optical intensity modulator IM, a beam splitter, photoelectric conversion module, a lock-in amplifier module, a direct-current offset module, an A/D conversion module, a D/A conversion module, a bias voltage drive module and an FPGA main control module, wherein the laser device is connected with the electro-optical intensity modulator IM; the electro-optical intensity modulator IM is connected with the beam splitter; one end of the beam splitter is connected with the photoelectric conversion module; the photoelectric conversion module is connected with the lock-in amplifier; the lock-in amplifier is connected with the direct-current offset module; the direct-current offset module is connected with the A/D conversion module; and the A/D conversionmodule is connected with the FPGA main control module. In the invention, through the control scheme of an IM direct-current working point formed by the lock-in amplifier feed performing real-time feedback and self-calibration, the problem of security threat caused by a decoy state preparation module in a QKD system is solved.

Description

technical field [0001] The invention relates to a quantum key distribution system, in particular to a closed-loop control system and method for an electro-optic intensity modulator in the quantum key distribution system. Background technique [0002] At present, most of the practical optical fiber quantum key distribution systems (hereinafter referred to as QKD) use a strongly attenuated weakly coherent laser as an ideal single photon source, and this light source has a certain probability of containing multiple photons, so that an eavesdropper can obtain information by intercepting excess photons without being detected. In order to deal with this threat, a decoy-state BB84 quantum key distribution protocol is proposed to defend against attacks. [0003] At present, there are mainly two schemes for decoy state generation: one is the internal modulation scheme, that is, the laser is driven by current pulse signals of different amplitudes, thereby generating optical signals o...

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Problems solved by technology

However, due to the structure of the IM itself, when mechanical vibration or other factors such as ambient temperature change, the DC operating point of the IM will slowly dri

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