RF frequency conversion is a key function of telecom satellite payloads. Hereafter are presented new photonic RF sub-system concepts supporting multi-channel, wideband frequency-conversion, thus drastically reducing the amount of equipment, for frequency down- and up-conversions respectively at the inputs and outputs of a digital processor. Proof-of-concept demos are presented and the measured RF performance reviewed vs. predictions and system requirements. The so-called dual-band, multi-LO frequency-converter (DB-MLFC) concept is an extension of the multi-LO frequency-conversion scheme already proven by Thales Alenia Space. It makes use of a dual-drive modulator with wavelength-multiplexed LO input and RF signal inputs in separate frequency bands. It can be applied to digital processor-based payloads and perform down-conversion of Ka or V-band sub-bands to the C-band of the processor input. The DB-MLFC concept was proven to support down-conversion of 2 and 3 sub-bands from the Ka (~30 GHz) and V (~50 GHz) bands to the C (~6 GHz) band of the processor input. The second concept called multi-RF frequency-converter (MRFC) consists in mixing multiple RF signals on separate optical carriers with an electrical LO signal into one electro-optical mixer. RF signals to undergo the same frequency conversion are combined via a WDM and fed into the optical input port of an electro-optical modulator, the RF port being driven by the LO. The RF performance of the MRFC concept, were measured with up-conversion of up to 8 C-band RF signals from the processor output to Ka-band payload output frequencies (~20 GHz).
KEYWORDS: Free space optics, Transmitters, RF photonics, Analog electronics, Modulation, Optical transmission, Digital modulation, Analog modulation, Satellites, Laser applications
Optical technologies play an increasing role in telecom satellite payloads for analog or digital applications. When large SWaP (size, weight, and power) is prohibitive or for applications where low cost is a major design goal, an electro-absorption modulated laser (EML) can provide a good balance between integration and performance optimization through separated control of emission and modulation. 1550 nm EML for ground applications were evaluated for optical local oscillator (LO) distribution, photonic RF frequency conversion, digital and analog free-space optical (FSO) communications. An EML-based LO distribution was assessed in terms of RF output power, spectral purity and phase noise. Using optical amplification, large-scale distribution of a 13 GHz LO was achieved with similar or greater RF power and a limited noise floor penalty compared to what is possible with a CW laser and Mach-Zehnder modulator (MZM). Photonic RF frequency-conversion was assessed as well and EML was found to perform better than direct modulation laser. For optical inter-satellite links in constellations, SWAP and cost really matter and EML is therefore an interesting candidate. An EML-based transmitter was evaluated for digital modulation at 10 and 20 Gbps as well as for RF analog modulation in transmit Ka band (20 GHz). For digital modulation, an EML module exhibited a similar dynamic extinction ratio as a MZM, and a limited penalty in detection sensitivity. For RF modulation, the carrier-to-noise ratio was measured as a function of the received optical power for various EML operating conditions: equivalent RF performance were achieved as well.
The European H2020-SPACE-ORIONAS project targets the development of optical transceiver and amplifier integrated circuits and modules applicable to high-speed and compact laser communication terminals. This paper presents the most recent project achievements in two areas. Firstly, the fabrication of high-speed electronic-photonic modulator and receiver circuits monolithically integrated in the silicon photonics platform and their assembly in bread-board level photonic modules. Secondly, the assembly, integration and testing of a radiation resistant, high-gain optical fiber preamplifier which exploits hi-rel small form factor fiber optics to shrink the module mass and footprint.
The EU-SIPhoDiAS project deals with the development of critical photonic building blocks needed for highperformance and low size, weight, and power (SWaP) photonics-enabled Very High Throughput Satellites (VHTS). In this presentation, we report on the design and fabrication activities during the first year of the project concerning the targeted family of digital and microwave photonic components. This effort aims to demonstrate components of enhanced reliability at technology readiness level (TRL) 7. Specifically, with respect to microwave photonic links, we report: (i) the design of Ka and Q-bands analogue photodetectors that will be assembled in compact packages, allowing for very high bandwidth per unit area and (ii) on the design of compact V-band GaAs electro-optic modulator arrays, which use a folded-path optical configuration to manage all fiber interfaces packaged opposite direct in-line RF feeds for ease of board layouts and mass/size benefits. With respect to digital links, we report on the development of 100 Gb/s (4 x 25 Gb/s) digital optical transceiver sub-assemblies developed using flip-chip mounting of electronic and opto-parts on a high-reliability borosilicate substrate. The transceiver chipset developed specifically for this project refers to fullycustom 25 Gb/s radiation hard (RH) VCSEL driver and TIA ICs designed in IHP’s 130 nm SiGe BiCMOS Rad-Hard process.
H2020-SPACE-ORIONAS is a 3-year Research and Innovation Action program funded by the European Commission focusing on the development of compact optical transceiver and amplifier modules applicable to new generation optical inter-satellite links. ORIONAS explores photonic integrated circuits and small form factor fiber optics leveraging their success in datacenter interconnect and hi-rel aerospace applications to deliver miniaturized modules and devices that can shrink considerably the SWaP of lasercom terminals. This paper presents the most recent project achievements.
This paper reports on the assessment of the communication performance of DPSK- and OOK-based free-space optical (FSO) links in satellite-based applications, including LEO downlinks, LEO inter-satellite links, and feeder links for GEO Satellites. The performance is assessed by means of simulations as well as transmission experiments at 10 Gbps. The impact of optical filter bandwidth, optical delay-line-interferometer accuracy, frequency offset between transmitter laser and receiver, is quantified. OOK performance critically depends on transmitter extinction ratio, and proves robust to Doppler-induced frequency offsets. DPSK is sensitive to any laser wavelength drift and offset with the DLI response. Nevertheless, compensation of this drift is considered manageable, making it possible to maintain the 3dB advantage of DPSK vs. OOK in practical use conditions.
We present the development and verification testing of a high speed multimode, multicore transceiver technology for intra-satellite optical interconnects. We report the fabrication and functional testing of opto-parts including 25 Gb/s 850 nm VCSEL/PD as well as the verification testing of the VCSELs against radiation and lifetime performance. In addition we report the development and evaluation testing of a multi-core cable assembly that was fabricated and mated with MiniAVIM multi-core connectors to develop hi-rel multi-core optical patchcords for pigtailing the transceiver modules. The fiber optic, electronic and opto-parts were used to assemble the first ever fully packaged and pigtailed, six-core optical transceiver prototype module that operates at 25 Gb/s channel bit rate at an energy consumption of ∠4.5 mW/Gb/s.
KEYWORDS: Laser applications, RF photonics, Free space optics, Laser development, Free space optical communications, Frequency conversion, High power lasers, Telecommunications, Satellites, Laser damage threshold
This article reports the development of 200-mW 1.55-μm DFB laser module with RIN below -162 dB/Hz which are well suited for microwave photonics or free space optical communication applications. Specific design has allowed reaching high power (>300 mW), low noise and high spectral purity laser chip. The chip has been packaged in Butterfly module optimized for reducing the module power consumption. DFB laser module system validations have been done on three laboratory test-beds representative of target applications, namely high-frequency optical LO distribution, photonic RF frequency conversion, and free space optical communication links.
Interest in free space optical communications has increased in the last decades as it has many advantages over RF communications, especially for space-borne applications. However, high power, good spectral quality and beam quality are needed for efficient data transmission over long distances. To meet the need of having lightweight and compact laser sources with such qualities for FSO, semiconductor based MOPA systems (Master Oscillator Power Amplifier) have been developed. In this paper we present the experimental results and compare them to simulation results for a threesection monolithically integrated semiconductor Master Oscillator Power Amplifier emitting at 1.5 μm wavelengths, designed for LIDAR applications that can also be used for free space telecommunications. The MOPA includes a distributed feedback laser section for single mode light emission, an intermediate section for data modulation and a flared semiconductor optical amplifier section for power amplification, which allows us to generate a high power beam with good spectral characteristics. The impact of bias conditions of the different device sections and device design on performances have been studied. Single mode operation at 4 different wavelengths near 1550 nm is achieved for optical output power up to 400 mW in continuous-wave (CW) regime for a SOA current of 3 A and 800 mW for SOA pulsed operation for currents up to 5 A. Near-field profile is also analyzed for different modulator current. Small-signal dynamic response is measured and analyzed.
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