Dr. Florian Moll Profile

Dr. Florian Moll

at Deutsches Zentrum für Luft- und Raumfahrt e.V.

SPIE Involvement:

Conference Program Committee | Author | Editor

Publications (24)

SPIE Journal Paper | 6 February 2024

Measurement-based characterization of atmospheric background light in satellite-to-ground quantum key distribution scenarios

Stefanie Häusler, Davide Orsucci, Leonard Vollmann, Eltimir Peev, Florian Moll

OE, Vol. 63, Issue 04, 041211, (February 2024) https://doi.org/10.1117/12.10.1117/1.OE.63.4.041211

KEYWORDS: Sensors, Quantum key distribution, Quantum detection, Quantum light, Quantum measurement, Tunable filters, Satellite to ground quantum key distribution, Signal to noise ratio, Satellites, Pulse signals

Read Abstract +

Proceedings Article | 15 March 2023 Presentation + Paper

Optical satellite links at DLR

C. Fuchs, F. Moll, J. Poliak, A. Reeves, C. Schmidt

Proceedings Volume 12413, 1241306 (2023) https://doi.org/10.1117/12.2659377

KEYWORDS: Satellites, Free space optics, Quantum key distribution, Adaptive optics, Satellite communications, Atmospheric optics, Telescopes, Free space optical communications, Laser communication terminals, Quantum optics experiments

Read Abstract +

Proceedings Article | 26 October 2022 Presentation + Paper

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

René Rüddenklau, Eltimir Peev, Florian Moll

Proceedings Volume 12266, 122660E (2022) https://doi.org/10.1117/12.2636111

KEYWORDS: Sensors, Quantum key distribution, Optical tracking, Actuators, Satellites, Mirrors, Free space optical communications, Control systems, Signal processing, Linear filtering, Acquisition tracking and pointing, Laser communications, Beam steering

Read Abstract +

Proceedings Article | 26 October 2022 Presentation + Paper

Analysis of power scintillation and fading margin in the LEO-ground downlink with the OSIRISv1 laser terminal on Flying Laptop and the DLR optical ground station Oberpfaffenhofen

Florian Moll, Dirk Giggenbach, Christopher Schmidt, Christian Fuchs

Proceedings Volume 12266, 122660F (2022) https://doi.org/10.1117/12.2647830

KEYWORDS: Scintillation, Satellites, Telescopes, Statistical analysis, Satellite communications, Atmospheric propagation, Analytical research, Wave propagation

Read Abstract +

Proceedings Article | 12 September 2021 Presentation + Paper

QCalc: a tool to compute classical and quantum communication rates over free-space optical channels

Davide Orsucci, Jorge Rosano Nonay, Amita Shrestha, Florian Moll

Proceedings Volume 11868, 118680F (2021) https://doi.org/10.1117/12.2600016

KEYWORDS: Quantum key distribution, Free space optics, Receivers, Quantum communications, Sensors, Transmitters, Signal attenuation, Optical communications, Telecommunications, Satellites

Read Abstract +

Proceedings Article | 11 June 2021 Open Access

Dual wavelength optical system for multiple quantum communication transmitters in Cubesat platform

Christian Menninger, Florian Moll, Benjamin Rödiger

Proceedings Volume 11852, 118525M (2021) https://doi.org/10.1117/12.2599965

Read Abstract +

Quantum Key Distribution (QKD) systems will play an important role in future networks for secure data communication. In order to provide a global coverage of a future QKD service, satellites are needed to bridge large distances. These satellite systems must be cost efficient to facilitate deployment since many network nodes will be needed. The CubeSat standard is frequently used for New Space projects as a versatile platform for satellite payloads. It is also chosen as a baseline for the construction of the system described in this paper. The DLR Institute of Communications and Navigation develops optical free space communication systems for scientific research in classical and quantum communications. A previous development of a 1/3 U CubeSat communication terminal for up to 100 Mbit/s downlinks is adapted to be used for quantum communications tests with multiple transmitters. Since the original laser terminal was designed for C-band wavelengths, a redesign of the optical system is needed to achieve polychromatic performance for the three sources. The optical system consists of a fiber collimator, a beam steering system and an afocal telescope. Most important requirement of the latter is a similar magnification for all wavelengths to ensure concentric beams pointing to the OGS. Scenarios in which the system is optimized either for lowest divergences or a similar magnification of the telescope are demonstrated in Figure 1. As the afocal telescope is used bidirectionally, it also needs to be optimized for the incident wave-front of the beacon from the OGS with respect to the beam shape at the four quadrant detector. These parameters are important for a correct pointing control. A fiber-based wavelength division multiplexer (WDM) is used for combining signals from three sources into one output fiber. As shown in the block diagram in Figure 2, it is based on cascaded thin film interference filters which are coupled to the fibers. Especially the propagation of 850 nm and 1550 nm signals in one single mode fiber is critical. Therefore the types of optical fibers were selected with respect to the bend loss, single mode propagation behavior, polarization integrity and optimal cladding diameter for the production.

DOWNLOAD PAPER

Proceedings Article | 11 June 2021 Open Access

Modular FSO optical system design for classical and quantum optical communication systems

Shehryar Ishtiaq, Christopher Schmidt, Florian Moll

Proceedings Volume 11852, 118520G (2021) https://doi.org/10.1117/12.2599161

KEYWORDS: Optical design, Beam splitters, Optical components, Optical benches, Optical filters, Telecommunications, Optical communications, Calibration, Quantum communications, Sensors

Read Abstract +

Optical communication systems are picking up pace in the various industries for its many scenarios in which it can be used. This includes satellite, aircraft and ground systems for which the DLR Institute of Communications and Navigation develops laser terminals. Free Space Optics (FSO) based optical systems have different applications ranging from terrestrial to airborne to space, and thus also the associated requirements to these application domains vary even though the primary functional goals remain the same. Furthermore, quantum communication became of interest for its inherently secure key generation process that allows two nodes to securely communicate with each other and share secrets for long term security. Out of the different use cases of free-space optical laser terminal came the concept of having a modular FSO optical system design that could quickly adapt to the changing needs from mission to mission. The idea of a modularity appeals to many despite its challenges in the beginning, as in the long run the pros outweigh the cons and the gained advantages make the initial effort worth the while. The concept was realised by carefully studying different requirements from various on-going and past projects and thereafter segmenting different aspects of the optical system based on three main categories, namely; the received path, the transmitted path and the shared path. To elaborate modularity in system here; a fast steering mirror (FSM) can be replaced with a fold mirror for a simpler design should the requirements not require it, or an exchangeable CPA with integrated telescope mounted at the aperture of the optical bench to allow for different magnifications and ex-aperture beam diameter, all these without major impact on other subsystems. This greatly reduces the effort involved in re-evaluating system performance in the long run. In this study the design and development of such an optical system is presented that lays its ground in the Institute of Communications and Navigation’s OSIRIS project, but still continues to serve as the primary optical system design of choice for future projects.

DOWNLOAD PAPER

Proceedings Article | 11 June 2021 Open Access

Modeling of piezoelectric actuator's hysteresis and its effect on the control accuracy of a LEO-to-GEO laser-communication for a small satellite

Phong Xuan Do, Ryo Suzumoto, Alberto Carrasco-Casado, Florian Moll, Takayuki Hosonuma, Morio Toyoshima, Shinichi Nakasuka

Proceedings Volume 11852, 118523B (2021) https://doi.org/10.1117/12.2599541

Read Abstract +

Compared to conventional large satellites in the past, small satellite classes (less than 150 kg) show their advantages for mass production, such as short time and low cost for development and launch, to cope with the demand for emerging missions that require a sufficient number of satellites in orbit. However, the traditional communication method, in which a low earth orbit (LEO) small satellite sends data to a ground station using radio frequency, has several disadvantages. Firstly, the limitation of radio-frequency bandwidth leads to a low data rate and difficulty in getting a frequency license. Secondly, there is a significant delay during which data cannot be sent to the ground due to lacking a line of sight between the LEO satellite and the ground station. Additionally, the duration time for the small satellite to communicate with the ground station is just less than 10 minutes approximately. To resolve the above issues, we investigate the case that a less-than-150-kg satellite carries out a laser communication link from LEO to a satellite in geostationary orbit (GEO). Due to the constraints of size, weight, and power (SWaP), traditional bulky LEO-GEO relay systems cannot be applied for the small satellite. However, using the combination of the satellite body pointing and a piezo Fast-Steering Mirror (FSM), which reduces the SWaP considerably, makes it feasible that the LEO-to-GEO communication can be implemented in a small satellite for the first time. While utilizing laser communication can increase the data rate, the relay communication via the GEO satellite helps the small satellite to extend the communication duration significantly. Moreover, since there is a line of sight between the two terminals in any of about 15 orbits per day of the LEO satellite, data taken by the small satellite can be downloaded to the ground via the GEO one in almost real time. This research aims at investigating and proving the feasibility of a small satellite to transmit a laser communication link to its GEO counterpart. In this paper, we describe the LEO-to-GEO laser communication of the small satellite with a study of pointing-budget and link-budget analysis. Furthermore, a hardware-based simulation of the fine control mechanism is conducted. The hysteresis that affects severely to the piezo mechanism, and hence, the final control accuracy, is modeled accurately and its effect is shown.

DOWNLOAD PAPER

Proceedings Article | 7 October 2019 Paper

Stratospheric QKD: feasibility analysis and free-space optics system concept

Florian Moll, Thierry Botter, Christoph Marquardt, David Pusey, Amita Shrestha, Andrew Reeves, Kevin Jaksch, Kevin Gunthner, Oemer Bayraktar, Christian Mueller-Hirschkorn, Alberto Diago Gallardo, Dionisio Diaz Gonzalez, Wenjamin Rosenfeld, Peter Freiwang, Gerd Leuchs, Harald Weinfurter

Proceedings Volume 11167, 111670H (2019) https://doi.org/10.1117/12.2539076

KEYWORDS: Quantum key distribution, Free space optics, Telescopes, Adaptive optics, Electronics, Receivers, Atmospheric particles, Polarization, Atmospheric modeling, Telecommunications

Read Abstract +

Quantum key distribution (QKD) is one of the most mature quantum technologies and can provide quantum-safe security in future communication networks. Since QKD in fiber is limited to a range of few hundred kilometers, one approach to bridge continental scale distances may be the use of high altitude pseudo satellites (HAPS) as mobile trusted nodes in the stratosphere. In parallel, free-space laser communication for high rate data transmission has been a subject of research and development for several decades and its commercialization is progressing rapidly. Important synergies exist between classical free-space communication and QKD systems since the quantum states are often implemented using the same degrees of freedom such as polarization or field amplitude and phase. These synergies can be used to benefit from the progress in classical free-space laser communication in QKD applications. In this paper, the use case of QKD in a stratospheric environment is described wherein HAPS may serve as relay station of secret keys and encrypted data. The mission scenario and HAPS capabilities are analyzed to derive special requirements on the stratospheric laser terminal, the link geometry and the ground segment with respect to a feasibility demonstration. To obtain a flexible and compatible system, discrete variable and continuous variable QKD protocols are considered to be implemented side by side in the HAPS payload. Depending on the system parameters, it can be beneficial to use the one or the other kind of protocol. Thus, a direct comparison of both in one and the same system is of scientific interest. Each of the protocols has particular requirements on coupling efficiency and implementation. Link budget calculations are performed to analyze possible distances, key rates and data transmission rates for the different schemes. In case of the QKD system, the mean coupling efficiency is of main interest, i.e. signal fluctuations arising from atmospheric turbulence must be taken into account in the security proof, but the buffered key generation relaxes real-time requirements. This is different to classical communications, where the corresponding fading loss must be assessed. A system architecture is presented that comprises the optical aircraft terminal, the optical ground terminal and the most important subsystems that enable implementation of the considered QKD protocols. The aircraft terminal is interfaced with the dedicated quantum transmitter module (Alice) and the ground station with the dedicated quantum receiver module (Bob). The optical interfaces are SMF couplings which put high requirements on the receiving optics, in particular the need for wave-front correction with adaptive optics. The findings of the system study are reviewed and necessary next steps pointed out.

Proceedings Article | 4 March 2019 Paper

Update on DLR's OSIRIS program and first results of OSIRISv1 on Flying Laptop

Christian Fuchs, Christopher Schmidt, Jonas Keim, Florian Moll, Benjamin Rödiger, Michael Lengowski, Steffen Gaißer, Dirk Giggenbach

Proceedings Volume 10910, 109100S (2019) https://doi.org/10.1117/12.2514349

KEYWORDS: Satellites, Satellite communications, Cameras, Collimators, Telecommunications, Optical tracking, Optical communications, Data communications, Optical amplifiers, Navigation systems

Read Abstract +

Proceedings Article | 6 October 2017 Presentation + Paper

Aspects of scintillation modelling in LEO-ground free-space optical communications

Florian Moll

Proceedings Volume 10437, 104370D (2017) https://doi.org/10.1117/12.2282152

KEYWORDS: Scintillation, Turbulence, Satellites, Atmospheric modeling, Modeling, Atmospheric propagation, Free space optical communications, Wave propagation

Read Abstract +

Free-space optical communications can be used to transmit data from low Earth orbit satellites to ground with very high data rate. In the last section of the downlink, the electro-magnetic wave propagates through the turbulent atmosphere which is characterized by random index of refraction fluctuations. The propagating wave experiences phase distortions that lead to intensity scintillation in the aperture plane of the receiving telescope. For quantification, an appropriate scintillation model is needed. Approaches to analytically model the scintillation exist. Parameterization of the underlying turbulence profile (C_n² profile) is however difficult. The C_n² profiles are often site-specific and thus inappropriate or generic and thus too complex for a feasible deployment. An approach that directly models the scintillation effect based on measurements without claiming to be generic is therefore more feasible. Since measurements are sparse, a combination with existing theoretical framework is feasible to develop a new scintillation model that focuses on low earth orbit to ground free-space optical communications link design with direct detection. The paper addresses several questions one has to answer while analyzing the measurements data and selection of the theoretical models for the LEO downlink scenario. The first is the question of a suitable yet ease to use simple C_n² profile. The HAP model is analyzed for its feasibility in this scenario since it includes a more realistic boundary layer profile decay than the HV model. It is found that the HAP model needs to be modified for a feasible deployment in the LEO downlink scenario for night time. The validity of the plane wave assumption in the downlink is discussed by model calculations of the scintillation index for a plane and Gaussian beam wave. Inaccuracies when using the plane earth model instead of the spherical earth model are investigated by analyzing the Rytov index. Impact of beam wander and non-ideal tracking are also discussed. Eventually, satellite measurements are discussed together with model calculations. It is found that the model calculation with the modified HAP turbulence profile fits the measurements. The plane wave assumption is valid for calculation of scintillation. The flat earth model is accurate enough to model scintillation over elevation when using the extended Rytov theory. The effect of beam wander is negligible. Further work needs to be carried out to elaborate a new scintillation model from the measurements and theory.

Proceedings Article | 25 September 2017 Open Access

system aspects of optical LEO-to-ground links

D. Giggenbach, A. Shrestha, C. Fuchs, C. Schmidt, F. Moll

Proceedings Volume 10562, 105625N (2017) https://doi.org/10.1117/12.2296054

KEYWORDS: Receivers, Satellites, Signal attenuation, Atmospheric optics, Modulation, Scintillation, Astronomical imaging, Data communications, Sensors, Free space optics

Read Abstract +

DOWNLOAD PAPER

Proceedings Article | 25 September 2017 Open Access

Sota optical downlinks to DLR’s optical ground stations

Christian Fuchs, Dimitar Kolev, Florian Moll, Amita Shrestha, Martin Brechtelsbauer, Fabian Rein, Christopher Schmidt, Maki Akioka, Yasushi Munemasa, Hideki Takenaka, Morio Toyoshima

Proceedings Volume 10562, 1056247 (2017) https://doi.org/10.1117/12.2296107

KEYWORDS: Space telescopes, Telescopes, Satellites, Cameras, Astronomical imaging, Optical tracking, Sensors, Optical communications, Satellite communications, Transponders

Read Abstract +

DOWNLOAD PAPER

Proceedings Article | 21 October 2016 Paper

LEO-ground scintillation measurements with the optical ground station Oberpfaffenhofen and SOTA/OPALS space terminals

Florian Moll, Dimitar Kolev, Matthew Abrahamson, Christopher Schmidt, Ramon Mata Calvo, Christian Fuchs

Proceedings Volume 9991, 999102 (2016) https://doi.org/10.1117/12.2254809

KEYWORDS: Scintillation, Satellites, Space telescopes, Receivers, Telescopes, Satellite communications, Cameras, Transmitters, Optical testing, Near field optics

Read Abstract +

Proceedings Article | 29 April 2016 Paper

Aerospace laser communications technology as enabler for worldwide quantum key distribution

Florian Moll, Harald Weinfurter, Markus Rau, Christopher Schmidt, Gwen Melén, Tobias Vogl, Sebastian Nauerth, Christian Fuchs

Proceedings Volume 9900, 99000K (2016) https://doi.org/10.1117/12.2230232

KEYWORDS: Quantum key distribution, Satellites, Laser communications, Aerospace engineering, Free space optics, Satellite communications, Receivers, Polarization, Telecommunications, Telescopes

Read Abstract +

A worldwide growing interest in fast and secure data communications pushes technology development along two lines. While fast communications can be realized using laser communications in fiber and free-space, inherently secure communications can be achieved using quantum key distribution (QKD). By combining both technologies in a single device, many synergies can be exploited, therefore reducing size, weight and power of future systems. In recent experiments we demonstrated quantum communications over large distances as well as between an aircraft and a ground station which proved the feasibility of QKD between moving partners. Satellites thus may be used as trusted nodes in combination with QKD receiver stations on ground, thereby enabling fast and secure communications on a global scale. We discuss the previous experiment with emphasis on necessary developments to be done and corresponding ongoing research work of German Aerospace Center (DLR) and Ludwig Maximilians University Munich (LMU). DLR is performing research on satellite and ground terminals for the high-rate laser communication component, which are enabling technologies for the QKD link. We describe the concept and hardware of three generations of OSIRIS (Optical High Speed Infrared Link System) laser communication terminals for low Earth orbiting satellites. The first type applies laser beam pointing solely based on classical satellite control, the second uses an optical feedback to the satellite bus and the third, currently being in design phase, comprises of a special coarse pointing assembly to control beam direction independent of satellite orientation. Ongoing work also targets optical terminals for CubeSats. A further increase of beam pointing accuracy can be achieved with a fine pointing assembly. Two ground stations will be available for future testing, an advanced stationary ground station and a transportable ground station. In parallel the LMU QKD source size will be reduced by more than an order of magnitude thereby simplifying its integration into future free-space optical communication links with CubeSats.

Proceedings Article | 29 October 2015 Paper

Ground stations for aeronautical and space laser communications at German Aerospace Center

Florian Moll, Amita Shrestha, Christian Fuchs

Proceedings Volume 9647, 96470I (2015) https://doi.org/10.1117/12.2194093

KEYWORDS: Telescopes, Cameras, Space telescopes, Optical tracking, Acquisition tracking and pointing, Computing systems, Satellites, Telecommunications, Receivers, Mirrors

Read Abstract +

Proceedings Article | 17 October 2014 Paper

Demonstration of high-rate laser communications from fast airborne platform: flight campaign and results

Florian Moll, Wolfgang Mitzkus, Joachim Horwath, Amita Shrestha, Martin Brechtelsbauer, Luis Martin, Alberto Lozano, Dionisio Diaz Gonzalez

Proceedings Volume 9248, 92480R (2014) https://doi.org/10.1117/12.2067248

KEYWORDS: Sensors, Laser communications, Free space optics, Fourier transforms, Defense and security, Glasses, Receivers, Dense wavelength division multiplexing, Signal attenuation, Control systems

Read Abstract +

Proceedings Article | 6 March 2014 Paper

Channel characterization for air-to-ground free-space optical communication links

Kevin Shortt, Dirk Giggenbach, Ramon Mata-Calvo, Florian Moll, Christian Fuchs, Christopher Schmidt, Joachim Horwath, Jack Yeh, Vevek Selvaraj, Ranjoy Banerjee

Proceedings Volume 8971, 897108 (2014) https://doi.org/10.1117/12.2039834

KEYWORDS: Cameras, Telescopes, Wavefront sensors, Imaging systems, Optical communications, Telecommunications, Space telescopes, PIN photodiodes, Free space optical communications, Measurement devices

Read Abstract +

Proceedings Article | 6 March 2014 Paper

Transmitter diversity verification on ARTEMIS geostationary satellite

Ramon Mata Calvo, Peter Becker, Dirk Giggenbach, Florian Moll, Malte Schwarzer, Martin Hinz, Zoran Sodnik

Proceedings Volume 8971, 897104 (2014) https://doi.org/10.1117/12.2036554

KEYWORDS: Satellites, Transmitters, Scintillation, Turbulence, Visibility, Telescopes, Sensors, Cameras, Beam splitters, Mirrors

Read Abstract +

Proceedings Article | 25 October 2012 Paper

Air to ground quantum key distribution

Sebastian Nauerth, Florian Moll, Markus Rau, Joachim Horwath, Stefan Frick, Christian Fuchs, Harald Weinfurter

Proceedings Volume 8518, 85180D (2012) https://doi.org/10.1117/12.929790

KEYWORDS: Quantum key distribution, Satellites, Mirrors, Polarization, Quantum communications, Satellite communications, Telecommunications, Signal attenuation, Stray light, Transmitters

Read Abstract +

Proceedings Article | 24 October 2012 Paper

Communication system technology for demonstration of BB84 quantum key distribution in optical aircraft downlinks

Florian Moll, Sebastian Nauerth, Christian Fuchs, Joachim Horwath, Markus Rau, Harald Weinfurter

Proceedings Volume 8517, 851703 (2012) https://doi.org/10.1117/12.929739

KEYWORDS: Quantum key distribution, Telecommunications, Receivers, Polarization, Telescopes, Signal attenuation, Transmitters, Scintillation, Space telescopes, Free space optics

Read Abstract +

Proceedings Article | 24 October 2012 Paper

Probability distributions of link durations with n disruptive channels: application to ground-space optical communications

Nicolas Perlot, Florian Moll

Proceedings Volume 8517, 851710 (2012) https://doi.org/10.1117/12.930604

KEYWORDS: Switches, Clouds, Optical communications, Space operations, Sun, Statistical analysis, Network security, Atmospheric propagation, Data modeling, Free space optical communications

Read Abstract +

Proceedings Article | 25 September 2007 Paper

Optical high-capacity satellite downlinks via high-altitude platform relays

Markus Knapek, Joachim Horwath, Florian Moll, Bernd Epple, Nicolas Courville, Hermann Bischl, Dirk Giggenbach

Proceedings Volume 6709, 67090E (2007) https://doi.org/10.1117/12.734053

KEYWORDS: Satellites, Medium wave, Relays, Clouds, Antennas, Microwave radiation, Modulation, Satellite communications, Atmospheric optics, Telecommunications

Read Abstract +

Proceedings Article | 25 September 2007 Paper

Wavelength selection criteria and link availability due to cloud coverage statistics and attenuation affecting satellite, aerial, and downlink scenarios

Florian Moll, Markus Knapek

Proceedings Volume 6709, 670916 (2007) https://doi.org/10.1117/12.734269

KEYWORDS: Clouds, Signal attenuation, Satellites, Absorption, Particles, Atmospheric particles, Refractive index, Statistical analysis, Mie scattering, Satellite imaging

Read Abstract +