Performance validation of a high-bandwidth fine steering mirror for optical communications

Witvoet, Gert; Kuiper, Stefan; Meskers, Arjan J. H.

doi:10.1117/12.2536136

Cited by 8 publications

(6 citation statements)

References 4 publications

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“…The maximum misalignment that our system was able to tolerate while maintaining the classical communication links was 250 μrad. This matches the coarse pointing accuracy of state-of-theart satellite and ground station platforms (34,35) and is greater than the expected pointing misalignment due to first-order turbulence effects (36).…”

Section: Introductionsupporting

confidence: 75%

Real-time gigahertz free-space quantum key distribution within an emulated satellite overpass

Roger,

Singh,

Perumangatt

et al. 2023

Sci. Adv.

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Satellite quantum key distribution (SatQKD) intermediated by a trusted satellite in a low-Earth orbit to ground stations along the satellite’s path allows remote users to connect securely. To establish a secure connection, a SatQKD session must be conducted to each user over a dynamically changing free-space link, all within just a few hundred seconds. Because of the short time and large losses under which the QKD protocol will be implemented, it has not yet been possible to form a complete key by transmitting all the relevant information required within a single overpass of the satellite. Here, we demonstrate a real-time QKD system that is capable of forming a 4.58-megabit secure key between two nodes within an emulated satellite overpass. We anticipate that our system will set the stage for practical implementations of intercontinental quantum secure communications that can operate over large networks of nodes and enable the secure transmission of data globally.

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Section: Introductionsupporting

confidence: 75%

Real-time gigahertz free-space quantum key distribution within an emulated satellite overpass

Roger,

Singh,

Perumangatt

et al. 2023

Sci. Adv.

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“…The CPA2s are still relatively large and the control bandwidth on this mechanism is limited and certainly not high enough to provide the required <0.65µrad, or even 0.25µrad pointing accuracy. The main function of the CPA2s is to 'offload' the Fast Steering Mirrors (FSMs) 17 in terms of required range, which is placed in the third optical module.…”

Section: Optical Design Space Segmentmentioning

confidence: 99%

GEOQKD: quantum key distribution from a geostationary satellite

Dirks

Ferrario

Pera

et al. 2021

International Conference on Space Optics — ICSO 2020

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Due to the distance limitation of quantum communication via ground-based fibre networks, space-based quantum key distribution (QKD) is a viable solution to extend such networks over continental and, ultimately, over global distances. Compared to Low Earth Orbits (LEO), QKD from a Geostationary Orbit (GEO) offers substantial advantages, such as large coverage, continuous link to ground stations (cloud cover limited), 24/7 operation (background limited), and no tracking required. As a downside, QKD from GEO comes with large link losses due to the space-ground distance, lowering the achievable key rates. From our feasibility and conceptual design study it is concluded that although link losses are high, QKD from GEO is technically feasible, and a favourable solution if the satellite needs to act as an untrusted node (that is, no security assumptions required for the space segment). However, the optimal solution, generating a higher value-for-money, is to have the possibility to operate it in trusted mode as well, as higher key rates can be obtained. But this will be at the cost of security as key material needs to be (temporarily) stored on board of the satellite. In order to arrive at a minimum required secure bit rate of ~1 bit/s in untrusted mode, two ~0.5m diameter telescopes in the space segment are required with <0.65μrad pointing accuracy each, a >1GHz entangled photon pair generation rate, in combination with ~2.5m diameter telescopes on ground, operating at 810nm wavelength. In trusted mode, with the same optical system but only using one telescope in the space segment, a factor of ~300 to ~10000 more key can be obtained. Details on our assumptions and results and drawings of the high level system design are presented, as well as a description of the required technology improvements and building blocks needed, which is applicable to non-GEO applications as well.

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“…In order to come as close as possible to a system that can also be used in satellite missions, a prototype FSM developed by Demcon and explicitly designed for space applications was evaluated. 3 1.1 QuNET-alpha…”

Section: Introductionmentioning

confidence: 99%

Development of a cascaded fine pointing and tracking control loop for quantum key distribution via free-space optical communications

Rüddenklau

Peev²,

Moll³

2022

Environmental Effects on Light Propagation and Adaptive Systems V

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Satellite based quantum key distribution (QKD) enables the delivery of keys for quantum secure communications over long distances. Maturity of the technology as well as industrial interest are ever increasing. Same is true for satellite free-space optical communications (FSOC). In order to enable a robust channel for transmission it is indispensable to account for static and dynamically changing misalignments between the transmitter and receiver pair. This work will focus on the transmitter terminal (Alice) and the design and verification process of the active beam steering system. The novelty is a recently developed variable reluctance fine steering mirror (FSM) including eddy current sensors (ECS) to measure its tip and tilt. A cascaded architecture was chosen in order to combine the optical stabilization objective with the dynamics of the mirror platform. The inner control loop makes use of an observer model whose estimated output is fed into a state controller allowing for an increased responsiveness. While high gains increase the closed loop bandwidth the eigenfrequency of the system introduces a pole to the plant which has to be avoided by the controller output. A digital notch filter was introduced to reject the excitation of the critical frequency band which gets obsolete in a system with high frequency sampling capabilities. The outer loop is engaged when a valid optical signal is received and a transition from a closed loop pointing to a closed loop tracking mode is performed. A proportional-integral (PI) controller keeps the received beam at the 4-quadrant-diode (4QD) whose center is used as the main reference through prior calibration with the transmit beam launching on the same path. The presented cascaded control scheme allows improvements in system performance and reliability.

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Performance validation of a high-bandwidth fine steering mirror for optical communications

Cited by 8 publications

References 4 publications

Real-time gigahertz free-space quantum key distribution within an emulated satellite overpass

Real-time gigahertz free-space quantum key distribution within an emulated satellite overpass

GEOQKD: quantum key distribution from a geostationary satellite

Development of a cascaded fine pointing and tracking control loop for quantum key distribution via free-space optical communications

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