Telecommunications payload
The photonic telecom payload enables high-bandwidth, low-latency data transmission in space-based communication systems through integrated optical technologies. A typical architecture mainly comprises conventional low-noise front-end receivers and high-power amplifier chains. It functions as a photonic repeater, routing RF signals from any input port to any output port. The core elements of the architecture include optical distribution of the high-frequency microwave local oscillator (LO) signal, RF-photonic frequency conversion, signal routing via photonic switching matrices, and signal filtering. The group has been involved in the design of each component to meet the requirements of future space missions.
In particular, reconfigurable photonic filters have demonstrated their ability to adapt to the continuously changing space environment by dynamically adjusting both the central frequency and bandwidth. By suppressing unwanted interference in an adaptive manner, these filters ensure reliable signal reception and transmission for precise and targeted communication with ground stations or other space platforms. The group has devised a reconfigurable filter based on carrier injection in a photonic crystal ring resonator, achieving a central frequency tuning range of 15 GHz [1]. The group is currently involved in the design of a fully reconfigurable photonic filter, that can be tuned both in central frequency and bandwidth independently. A solution has been presented comprising two decoupled thermally tunable ring resonators. A stopband rejection of 45 dB, bandwidth and central frequency reconfigurations of 20 MHz and 180 MHz, respectively, have been demonstrated [2].
Signal routing is implemented through the design of switches appropriately arranged in a matrix architecture, whose key element is a subwavelength-period lattice with thermo-optic tunability. This component offers a wide bandwidth (150 nm), high suppression of interference (38 dB), compact footprint (1620 μm × 576 μm), and relatively low power consumption (276 mW) [3].
Moreover, the optoelectronic oscillator is based on a positive feedback loop, where the optical signal in the upper arm is phase-modulated, filtered, delayed, and converted by a photodiode. In the lower arm, the corresponding electrical signal undergoes RF manipulation. Self-sustained oscillation occurs when the semiconductor optical amplifier (SOA) compensates for round-trip losses. A phase noise of −140 dBc/Hz at a 10 kHz offset from the carrier and an output power exceeding 10 dBm have been demonstrated within a compact volume of approximately 1 cm³ [4].
In the realm of space exploration, 5/6G wireless communication generating a comprehensive and ubiquitous high-speed, broadband, low latency network is highly desirable to which phased array antenna (PAA) system fed by a small scale, lightweight, stable, power efficient beamforming network (BFN) integrated to the satellite telecom payload have seen an astonishing growth in last few years both academically and from commercialization point of view. The traditional electrical BFNs often suffer from beam squinting effect, higher loss as well as size especially in higher frequency of operation (Ka- band and above) to which the future of wireless communication will be highly rely on. The optical BFN can remove the bottleneck since it offers broadband, power efficient, high-speed operation which is also immune to the electromagnetic interference. In the setup of BFN, optical delay lines play a pivotal role in setting up the relative delays among different antenna elements and thus generating high resolution steerable beams. In this context, over a decade our research group has been focused on developing highly efficient and compact delay lines as well as optical BFN which can address the future of telecommunication [5-8]. We successfully demonstrated a highly efficient graphene-based delay line in the standard silicon-on-insulator platform. The delay line has an ultra-compact footprint of 1.3×10-3 mm2 with fast switching time < 8 ns, excellent delay-to-loss ratio of 0.03 dB/ps and operating bandwidth of 1.2 GHz [5]. In another study the high delay tuning range (920 ps) is reported with a compact footprint of 4.15 mm2 through integrating graphene in ring resonator [6]. Recently we developed a low loss phase change material (PCM) based optical delay line in standard Triplex waveguide platform showing two orders of lower power consumption than the traditional thermos-optic tuning. Moreover, the localized tunning effect breaks the delay-bandwidth constraint enables continuous tunning of bandwidth from 2 to 6 GHz for a squint free beam steering over a large point of view of ±60o [7]. Currently we are developing full scale system for optical beamforming utilizing the advantages of phase change materials in standard waveguide platforms for high frequency broadband operation.
References
[1] G. Brunetti, F. Dell’Olio, D. Conteduca, M. N. Armenise, C. Ciminelli, “Ultra-compact tuneable notch filter using silicon photonic crystal ring resonator,” Journal of Lightwave Technology, vol. 37, no. 13, pp. 2970-2980, 2019. doi: 10.1109/JLT.2019.2908364
[2] A. di Toma, G. Brunetti, N. Saha, C. Ciminelli, “Fully reconfigurable photonic filter for flexible payloads,” Applied Sciences, vol. 14, no. 2, pp. 488, 2024. doi: https://doi.org/10.3390/app14020488
[2] G. Brunetti, G. Marocco, A. Di Benedetto, A. Giorgio, M. N. Armenise, C. Ciminelli, “Design of a large bandwidth 2× 2 interferometric switching cell based on a sub-wavelength grating,” Journal of Optics, vol. 23, no. 8, p. 085801. doi: 10.1088/2040-8986/ac0a8c
[3] G. Brunetti, M.N. Armenise, C. Ciminelli, “Chip-scaled Ka-band photonic linearly chirped microwave waveform generator,” Frontiers in Physics, vol. 10, p. 785650, 2022. doi: https://doi.org/10.3389/fphy.2022.785650
[4] G. Brunetti, D. Conteduca, F. Dell’olio, C. Ciminelli, and M. N. Armenise ‘Design of an ultra-compact graphene-based integrated microphotonic tunable delay line’, Opt Express, vol. 26, no. 4, pp. 4693-4704, 2018. https://doi.org/10.1364/OE.26.004593.
[5] T. Tatoli, D. Conteduca, F. Dell’Olio, C. Ciminelli, and M. N. Armenise, ‘Graphene-based fine-tunable optical delay line for optical beamforming in phased-array antennas’, Appl Opt, vol. 55, no. 16, pp. 4342-4349 (2016). https://doi.org/10.1364/AO.55.004342.
[6] C. Ciminelli, G. Brunetti, D. Conteduca, F. Dell’Olio, and M. N. Armenise. ‘Integrated Microphotonic Tuneable Delay Lines for Beam Steering in Phased Array Antennas.’ in 2018 20th International Conference on Transparent Optical Networks (ICTON), pp. 1-4. IEEE, 2018. https://doi.org/10.1109/ICTON.2018.8473592.
[7] C. Ciminelli, N. Saha, G. Brunetti, A. Di Toma, M. N. Armenise, ‘Reconfigurable Optical Beam Forming Network for Telecom Payloads.’ in 2024 24th International Conference on Transparent Optical Networks (ICTON), pp. 1-4. IEEE, 2024. https://doi.org/10.1109/ICTON62926.2024.10647596.