ESA Intended Invitation To Tender

18.1TT.26


Title: ASSESSMENT OF ANALOGUE OPTICAL LINKS THROUGH THE ATMOSPHERE (SCYLIGHT SL.007)
Program ref.: ScyLight
Tender Type: C
Quarter: 182
Tender Status: INTENDED
Price Range: > 500 KEURO
Budget Ref.: E/0502-01A - ScyLight
Proc. Prop.: DIPC
Special Prov.: DK+FR+DE+IT+NL+CH+GB+IE+AT+LU+CZ+RO+CA+NO
Establishment: ESTEC
Directorate: Directorate Telecom & Integrated Applica
Department: Telecom Technologies,Product&Systems Dep
Division: Technologies and Products Division
Responsible: Schmitt, Dietmar
Products: Satellites & Probes / Optical Communication / Optical Comm. / Optical terminals
Technology Domains: Optics / Optical Equipment and Instrument Technology / Optical Communications
Industrial Policy Measure: N/A - Not apply
Publication Date: 16-FEB-18

The objective of this activity is demonstrate reliable bidirectional analogue optical transmission (e.g., in C-band and in Ka-band)through the atmosphere in a scenario representative (in terms of link attenuation and optical turbulence) of an optical feeder linkbetween a geostationary telecommunication satellite and an optical ground station. Targeted Improvements:Demonstration of reliable analogue optical links through the atmosphere. Demonstrations of free-space optical communications has mainly focused on digital links (i.e., the optical carrier is modulated by a binary user data stream). Digital optical links can support regenerative payloads(requiring on-board demodulation/re-modulation of the user data stream) and transparent digital payloads (requiring digitalisation of the user data signal prior to the modulation of the optical carrier). For example, optical inter-satellite links implemented in the EDRS system are of the regenerative type (e.g., the user data stream is demodulated in the geostationary satellite's optical receiver and is then used to modulate the Ka-band carriers of the space-to-ground link). Regenerative systems are inherently specific and therefore cannot cope with the requirement of transparency for feeder links. Furthermore, digital optical links for transparent digital payloads would have to operate at much higher data rates (factor 10 to 20) compared to digital optical links for regenerativepayloads, due to the need to sample and digitalise the user signals, which, in turn, limits the size of feasible digital transparent processors for telecommunication satellites due to on-board mass, size and power consumption constraints. Analogue optical links constitute an interesting alternative for transparent payloads. In an analogue optical link, the radio frequency (RF) analogue signals (e.g., in C-band, Ku-band or Ka-band) modulate the intensity of the optical carrier, hence there is no bandwidth expansion and noneed for an on-board processor. The benefit of this approach is that, after analogue demodulation on board the satellite, the RF carriers can be processed by a standard payload. This concept is widely used in terrestrial fibre applications ("radio-over-fibre" links), and was already proposed by Contraves Space AG back in 2001 as an efficient manner to optically transmit analogue signals between standard bent-pipe satellites. Analogue optical links have been extensively investigated for intra-satellite communications (e.g., optical handling of microwave signals, including optical frequency conversion, optical switching and signal distribution). Atmospheric turbulence effects degrade the quality of an optical signal (wave front distortion, scintillation, beam spreading, beam wandering). Countermeasures using coding and interleaving schemes typically employed in digital optical links through the atmosphere cannotbe applied to analogue optical links. In this activity the feasibility of analogue optical links through the atmosphere will be investigated, including the development and trade-off of novel methods to minimise the signal to noise ratio degradation of an analogueoptical signal due to atmospheric propagation. The activity will include the design, manufacture and test of an end-to-end optical communications breadboard representative of a bidirectional analogue optical feeder link through the atmosphere. The breadboard willsubsequently be used to demonstrate the feasibility of analogue optical links through the atmosphere under relevant field conditions (e.g., a ground-to-ground link) and to quantify the achievable performance (e.g., maximum achievable bandwidth, supported RF bands, noise performance, link availability).