dlr.de • chart 1 dlr’s optical communications program for

DLR’s Optical Communications Program for 2018 and beyond

> DLR’s Optical Communications Program for 2018 and beyond > S. Scalise > October 2017 DLR.de • Chart 1

Dr. Sandro Scalise Institute of Communications and Navigation

Relevant Scenarios

• Unidirectional Links

• Main application areas • Earth observation • Deep space missions

• Inter-Satellite Links • Mainly LEO GEO • Mature and reliable technology

with TRL 9 (EDRS, Tesat LCT)

• Direct Earth-Ground Links • for LEO satellites

• esp. small LEOs (50 to 500 kg)

• For Cubesats


• Bidirectional Links

• Main application areas • Telecom • GNSS (for time transfer)?

• Inter-Satellite Links • HAPs • Mega-Constellations

• LEOs • maybe MEOs?

• Galileo 2-3G?

• Feeder Links for GEOs

> DLR’s Optical Communications Program for 2018 and beyond > S. Scalise > October 2017 DLR.de • Chart 4 DLR OSIRIS Program Optical Space Infrared Downlink System

• OSIRISv1 & OSIRISv2 in Orbit (on Flying Laptop & BIROS)

• Cubesat-Version in Orbit by 2018 • OSIRISv3 in Orbit by 2019

• Further OSIRIS-payloads to be

launched in 2019

OSIRIS Development Roadmap


OSIRISv1: • Open-Loop Body Pointing • Data rate: up to 200 Mbit/s

OSIRISv2: • Closed-Loop Body Pointing with

Tracking Sensor • Data rate: up to 1 Gbit/s

Launch

2017

2016

2018 2019

OSIRIS4CubeSat: • Active Beam Steering

combined with body pointing

• Data rate: up to 100 Mbit/s

OSIRISv3: • Active Beam

Steering with Coarse Pointing Assembly

• Data rate: up to 10 Gbit/s

Commercialization Phase together with:

OSIRISv1 on Flying Laptop Concept


Satellite Bus: • University of Stuttgart • Dimension: 80 x 60 x 50 cm • Mass: 120 kg • Launch: July 14th, 2017 System Parameters: • Laser 1: 200 Mbit/s with 1W • Laser 2: 78 Mbit/s with 125 mW • Power and weight: 26 W, 1,3 kg • Pointing: Open-Loop Body Pointing

Flying Laptop (FLP)

OSIRISv2 on BiROS Concept


Satellite Bus: • DLR Berlin Adlershof • Dimension: 88 x 65 x 55 cm • Mass: 115 kg • Launch: June 22nd, 2016 System Parameters: • Laser 1: 1 Gbit/s with 1W • Laser 2: 150 Mbit/s with 150mW • Power and weight: 37 W, 1,65 kg • Tracking Sensor with optical uplink channel (1 Mbit/s) • Pointing: Closed-Loop Body Poiting

Bispectral Infrared Optical System (BiROS)

OSIRISv2 Flight Model


BiROS satellite, DLR Berlin

OSIRISv3 – under Development… Concept • Modular system concept to adapt to different

missions and spacecraft needs • Commercialization partner: Tesat Spacecom • Designed for 5 years lifetime in orbit • Equipped with a dedicated Coarse Pointing

Assembly (CPA) unit • Data handling + storage included in the OSIRIS

terminal • Optical uplink channel System Parameters: • Weight: 5 kg • Power consumption:

50 W (operation), 10 W (Stand-By) • Downlink data rate: N x 10 Gbit/s Reference implementation for upcoming CCSDS-standard


Concept • Miniaturized OSIRIS version for

cubesat platforms • Highly compact system design • COTS components based on

OSIRIS space qualification • Demonstration mission in 2018 • Commercialization partner: Tesat

Spacecom System Parameters: • Size: 90 x 95 x 35 mm (~0,3U) • Weight: < 300g • Power consumption: < 8W • Downlink data rate: 100 Mbit/s


OSIRIS4CubeSat – under Development…

• Optimized for scientific measurements • 80 cm telescope with coudé room by 2018 • Adaptive Optics by 2019

Optical Ground Station Oberpfaffenhofen


• Optimized for data reception • 60 cm telescope • Worldwide use with short lead-time

Transportable Optical Ground Station


Optical GEO Feeder Links: Motivation

• Currently HT GEO Satellites: Ka-Band (user + feeder)

• Next steps: extensions to Q/V and W bands for feeder-links ( few extra-GHz)

• Number of required gateways increases linearly with throughput

• Approach: Optical Feeder Links • 10-12 OGSs for cloud mitigation • Every gateway provides full

capacity • DWDM Technology from fiber

communication • Several THz of bandwidth and

no-regulation


• Ground-Segment • Site availability vs. connectivity • Fast switching / handover

• Optical Link • Challenging channel esp. in the uplink (atmospheric turbulences)

• Pre-distortion adaptive optics • Transmitter diversity

• Space-Segment (optical RF Payload) • Power & mass budget • Heat dissipation • Space qualified HW

• High-speed ADCs and DACs • DWDM components • Optical pre-amplification

• First Step: Demonstrate DWDM Technology in relevant environment

Technological Challenges


• Ground link emulating the GEO feeder link • Environment defined by the atmospheric turbulence (Cn

2 profile) • 10,45 km link between DLR-Weilheim and DWD Hohenpeißenberg

• Measurement of the communications performance with strong fluctuations • Channel characterization


THRUST (Terabit throughput satellite system technology) Project

DLR-Weilheim

DWD-Hohenpeißenberg

10.45 km

• Satellite terminal with single-mode fiber coupling


THRUST: Hardware Setup for Fiber Coupling

FSM

VIS CAM

SMF

IR CAM

Filter Iris

RX

VIS / IR

T99 / R01

Telescope

4QD

Optics • Signal coupling Electronics • Sensor analysis • Actuator control

• Measurement campaign in October 2016


THRUST: Hardware on the Field during the Demonstration

TX: DLR Weilheim

RX: DWD - Hohenpeißenberg

Alignment Laser seen from DWD - Hohenpeißenberg

• Characterization of the power fluctuations and BER for each channel


THRUST: Test Campaign with Bit Error Ratio Measurements

• Measurements performed in several turbulence conditions

• Measured functionality in worst-case channel turbulence

• 1.72 Tbit/s transmitted with 40 DWDM channels in optical C-Band (Worldwide Record!)

• Coherent modulation schemes • Higher spectral efficiency • Better sensitivity

• Digital homodyne receiver • No need of OPLL • Digital signal processing • Robust to signal fading

• Technology demonstrated in GEO-equivalent turbulent environment

• 10.45 km worst-case channel conditions for GEO link • 30 Gbit/s BPSK demonstrated in October 2016 • 40 Gbit/s BPSK demonstrated in June 2017 • Signal processing optimized for the turbulent channel

Surof, J.; Poliak, J. & Mata Calvo, R., “Demonstration of intradyne BPSK optical free-space transmission in representative atmospheric turbulence conditions for geostationary uplink channel”, Opt. Lett., OSA, 2017, 42, 2173-2176


Coherent Optical Communications

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-42-11-2173

• Definition of the end-to-end communications system • Compatibility and interface with RF standards (DVB-S2X/RCS) • Modulation, coding, error correction approach

• Definition of a suitable payload architecture • Analog transparent vs. fully digital regenerative (many options in between) • Trade-off complexity / robustness

• Development of a robust coherent optical communication system • Higher sensitivity and more robust to channel impairments • Optimization of the post-processing for the atmospheric channel

• Development of channel impairments mitigation techniques • Adaptive optics: for downlink wave-front conjugation and uplink pre-distortion • Blind transmitter-diversity schemes • Laser Guide Stars for uplink channel estimation

• Collaboration with ESO/ESA in joint measurement campaigns


Next Steps towards First In-Orbit Demonstration…

• Optical LEO Satellite Downlinks • Two payloads in orbit, further payloads planned • Currently developed systems enable downlink rates of 10 Gbps • Higher data rates / Smaller terminals ( Cubesat) under development • Standardisation within CCSDS ongoing…

• Optical GEO Feeder Links

• DLR demonstrated DWDM technology in a representative environment • DLR raised the record in free-space optical transmission rate to 1.72 Tbps • Demonstration of 40 Gbit/s BPSK (with only one wavelength) • Goal is the first experimental demonstration by 2020-2021 in

cooperation with industrial partners

… thanks for more than 20 years of experience and heritage in optical free-space communications for space applications, DLR developments and early prototypes are an excellent basis for product development through our industrial partners

Summary & Conclusions


DLR’s Optical Communications Program for 2018 and beyond


Acknowledgments: Christian Fuchs, Dr. Dirk Giggenbach, Dr. Ramon Mata Calvo, Florian Moll, Christopher Schmidt … and all the rest of DLR team working on the subject…

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