Lasercom-on-chip for next generation, high-speed satellite constelation interconnectivity

Periodic Reporting for period 3 - ORIONAS (Lasercom-on-chip for next generation, high-speed satellite constelation interconnectivity)

Reporting period: 2021-05-01 to 2022-04-30

The sustained entry of optical inter-satellite links (OISLs) in satellite constellations requires compact photonic devices to deliver the critical transmission and amplification functions. Following the terrestrial optical communication trends where photonic integration has been the tool to continuously shrink the physical size of transceivers, modern OISLs are also expected to leverage photonic integrated circuits (PICs) made within semiconductor foundries to combine compactness and cost-effectiveness. Space transceiver PICs are also expected to merge optical and electronic functions to optimize footprint and RF performance, but also to relieve the system costs from the procurement and manual assembly of discrete, rad-hard electronics. Silicon photonics (SiPh) is of particular interest for the development of OISL transceivers since it allows monolithic integration of optical waveguides, opto-electronics and electronic integrated circuits within a CMOS process. Moving forward, flavors of SiPh that engage SiGe bipolar transistor technologies to manufacture the transceiver electronic circuitry would be of special interest due to their inherent radiation hardness. To further assist system compactness, optical fiber amplifiers will follow the trends in hi-rel aerospace sensing devices such as fiber optic gyroscopes which rely on small form factor (SFF) fiber optics. The availability of reduced clad Erbium doped fiber (RC-EDF) and hi-rel SFF components can be exploited to reduce the SWaP of optical pre-amplifiers at the receiver side. Finally, the physical size of booster optical amplifiers deployed at the transmit side can shrink significantly exploiting manufacturing of semiconductor optical amplifiers (SOAs) within InP foundries.
The H2020-SPACE-ORIONAS project has evolved with the aim to provide the above cited photonic technologies and demonstrate transceiver and amplifier circuits and modules that can disrupt both the shape of laser-com modems as well as the way they are built and tested. Leveraging these technologies, ORIONAS has demonstrated a number of compact transceivers and amplifiers applicable to high data rate direct or coherent detection OISLs. More specifically the project has demonstrated the following:
o Miniaturized electronic photonic (ePIC) modulator and receiver circuits for DPSK and coherent QPSK modulation formats.
o Assembly, integration and test (AIT) of the modulator and receiver circuits in bread-board modules.
o Compact erbium doped optical fiber amplifier featuring credit card footprint and low mass.
o Compact SOA booster amplifier featuring >20 dBm optical output power.
o Functional evaluation of the devices in the end-user system testbed.
In terms of technology readiness, ORIONAS has delivered critical designs, manufacturing of critical parts, assembly/integration of bread-board models and finally testing at part and BBM level to reach a TRL level of 3-4. Through its achievements and industrialization plan, ORIONAS is opening the opportunity for building a new generation of high-performance and low SWaP laser terminals within Europe and using high-end photonic technologies in which Europe has and continues to invest. ORIONAS has made targeted contributions to the evolution of European research and technology ecosystem as well as establishing a strong European supply chain for critical space photonic systems.

1. Design and fabrication of two generations of modulator and receiver integrated circuits in a 0.25 um photonic-BiCMOS process available by IHP. Using this process, photonics, opto-electronics and SiGe BiCMOS electronic circuits have been monolithically integrated on chips that occupy a few mm2 of silicon area. ORIONAS transceiver electronic-photonic integrated circuits include DPSK and coherent QPSK modulators and receivers which exhibit dense photonic integration (up to 45 integrated elements) merging the following functions on a single chip: a) spot-size conversion for edge coupling to standard SMF, b) variable optical attenuation, c) phase modulation, d) high-speed electrical driving, e) signal demodulation/mixing, f) balanced photodetection, g) transimpedance amplification and h) thermo-optic tuning. The integrated elements included: a) MMI couplers, b) doped silicon waveguides, c) passive silicon waveguides, d) waveguide coils, e) Ge diodes, f) thermal tuning heaters.
Highlights of the ePIC chip-level testing performed within ORIONAS are: a) Demonstration of SSC structures with losses as low as 1.7 dB when coupled to SMF lensed fiber, b) Ge photodiodes with low dark current (~45 nA) and high responsivity (>0.6 A/W), c) Verification of on-chip VOA and thermal tuning functions
2. AIT of the modulator and receiver ePICs into prototype bread-board model (BBM) sub-assemblies including the following: a) DPSK optical transmitter, b) DPSK optical receiver, c) IQ modulator and d) Coherent receiver.
Highlights of the modulator and receiver BBM testing performed within ORIONAS are: a) Demonstration edge coupled ePIC to standard SMF with coupling losses < 4 dB, b) 28 Gb/s DPSK demodulation and detection using the DPSK receiver BBM, c) 20 Gb/s modulation using the IQ modulator BBM, d) 100 Gb/s QPSK coherent detection using the coherent receiver BBM
3. Design and MAIT of compact radiation resistant high gain optical fiber pre-amplifier built with hi-rel SFF optics, radiation resistant RC-EDF, hi-rel opto-electronics and COTS electronics. The Engineering Model (EM)-level LNOA features credit card footprint and 100gram mass. In terms of optical performance, the LNOA delivers a typical (1550 nm) small signal gain >45 dB. The radiation induced gain drop at 40 krad is >3 dB which was verified through TID testing on the active fibers.
4. Design and MAIT of booster (>20 dBm) Semiconductor Optical Amplifier (SOA) chips using the Semi Insulating Buried Heterostructure (SiBH) process and assembly of the SOAs into compact butterfly packages. The SOA package includes the amplifier chip, TEC elements, the fiber assemblies as well as micro-optics for beam expansion, isolation and collimation within the gold-box module. Two SOAs were assembled into a BBM device for system-level testing. In terms of optical performance, the SOA was measured to deliver >100 mW saturated output power at 2A of driving current and at a typical wavelength of 1550 nm.

ORIONAS has completed the its lifetime which was dedicated to integrated circuit manufacturing, module assembly / packaging and system integration. Through its technical achievements ORIONAS is advancing the state-of-the-art in the following aspects:
a) development of the first edge-coupled optical transceiver integrated circuits that feature full flesh monolithic integration of silicon photonic and BiCMOS electronic integrated circuits. Such approach can facilitate integrated optical devices for high-bandwidth applications that require a higher degree of miniaturization.
b) development of module assembly method for co-packaging of modulator PICs with laser diodes toward integrated PIC-based transceiver modules
c) development of semiconductor booster amplifiers that reduce drastically the amount of components to be qualified and assembled compared to conventional booster fiber amplifier technology.
d) development of the first radiation resistant miniaturized optical pre-amplifier that demonstrates >80% savings in mass and unit area.

Periodic Reporting for period 3 - ORIONAS (Lasercom-on-chip for next generation, high-speed satellite constelation interconnectivity)

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