Multi-aperture digital coherent combining for free-space optical communication receivers

Geisler, David J.; Yarnall, Timothy M.; Stevens, Mark L.; Schieler, Curt; Robinson, Bryan S.; Hamilton, Scott A.

doi:10.1364/oe.24.012661

Cited by 83 publications

(50 citation statements)

References 39 publications

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“…Generally, a diversity system is made more effective by the addition of some signal processing such as Equal Gain Combining (EGC) or Maximal Ratio Combining (MRC) [222], [223]. There have also been some successful demonstrations of MIMO and DSP with sophisticated, coherent receivers [224], [225]. Space-time block codes (for example Alamouti and Golden codes) have also been shown to be effective, but simple repetition codes (i.e.…”

Section: Impact On Optical Signal Processingmentioning

confidence: 99%

Structured Light in Turbulence

Cox

Mphuthi

Nape

et al. 2021

IEEE J. Select. Topics Quantum Electron.

113

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Optical communication is an integral part of the modern economy, having all but replaced electronic communication systems. Future growth in bandwidth appears to be on the horizon using structured light, encoding information into the spatial modes of light, and transmitting them down fibre and free-space, the latter crucial for addressing last mile and digitally disconnected communities. Unfortunately, patterns of light are easily distorted, and in the case of free-space optical communication, turbulence is a significant barrier. Here we review recent progress in structured light in turbulence, first with a tutorial style summary of the core concepts, before highlighting the present state-of-the-art in the field. We support our review with new experimental studies that reveal which types of structured light are best in turbulence, the behaviour of vector versus scalar light in turbulence, the trade-off of diversity and multiplexing, and how turbulence models can be exploited for enhanced optical signal processing protocols. This comprehensive treatise will be invaluable to the large communities interested in free-space optical communication with spatial modes of light.

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Section: Impact On Optical Signal Processingmentioning

confidence: 99%

Structured Light in Turbulence

Cox

Mphuthi

Nape

et al. 2021

IEEE J. Select. Topics Quantum Electron.

113

View full text Add to dashboard Cite

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“…Specifically, each coherent front-end had two stages of amplification and filtering followed by a photonic lightwave circuit that consisted of a 90 • optical hybrid, balanced photodiodes, and trans-impedance amplifiers (see Ref. 5 for further details). The experimental setup in Figure 2 enabled measurements of a CW signal in a double-pass link using the Tx Laser.…”

Section: Experimental Arrangementmentioning

confidence: 99%

“…In our previous work, we identified a ground architecture based on an array of small telescopes. 5 That work included a laboratory demonstration of combining signals from each element of this array in a lossless manner over a significant range of input powers by using coherent detection and digital signal processing techniques. In practice, free-space optical communication through the atmosphere must contend with the unwanted effects of atmospheric turbulence.…”

Section: Introductionmentioning

confidence: 99%

Experimental demonstration of multi-aperture digital coherent combining over a 3.2-km free-space link

et al. 2017

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The next generation free-space optical communications infrastructure will need to support a wide variety of spaceto-ground links. As a result of the limited size, weight, and power on space-borne assets, the ground terminals need to scale efficiently to large collection areas to support extremely long link distances or high data rates. Recent advances in integrated digital coherent receivers enable the coherent combining (i.e., full-field addition) of signals from several small apertures to synthesize an effective single large aperture. In this work, we experimentally demonstrate the coherent combining of signals received by four independent receive chains after propagation through a 3.2-km atmospheric channel. Measured results show the practicality of coherently combining the four received signals via digital signal processing after transmission through a turbulent atmosphere. In particular, near-lossless combining is demonstrated using the technique of maximal ratio combining.

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“…FSOC systems often operate in the photon-starving regime, and thus high sensitivity is a critical requirement for the lasercom terminals. For this reason, the coherent receivers based on the phasediversity technique have attracted much attention in the FSOC field because of their exceptionally high sensitivity [4]- [8]. However, the optical complexity and power consumption of the coherent receivers are too high, especially for space-borne platforms.…”

Section: Introductionmentioning

confidence: 99%

Design of the Real-Time Single-Photodiode Digital Coherent Receiver Suitable for Free Space Optical Communication

Zhou

Cui

et al. 2020

IEEE Photonics J.

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High sensitivity, small size, light weight and low power are the most critical requirements for the lasercom terminals used in free space optical communication (FSOC) systems. Coherent receivers have an exceptionally high sensitivity but their optical complexity and power consumption are too high, especially for the space-borne lasercom terminals. Recently we propose a pseudo-single-side-band-signal based singlephotodiode coherent receiver (P-SCR) with very low optical and algorithm complexity which can potentially satisfy the strict requirement of the FSOC systems. In this paper, we first introduce the working principles of the P-SCR based on the frequency and time domain field reconstruction algorithms (TD-FRA and FD-FRA). We then investigate the relationships between the computation complexity and sensitivity for the two kinds of P-SCR, respectively. We also provide a method to minimize the FD-FRA complexity and demonstrate that its power consumption is only 3.7%, 25.3% and 37.8% of that of the well-known conventional Kramers-Kronig (KK) algorithm, upsampling-free KK algorithm and TD-FRA. Based on the optimized FD-FRA, we develop a highly parallel DSP circuit for the real-time P-SCR using a FPGA chip. The experiments in a 10GBaud QPSK transmission system show that the sensitivity of the real-time P-SCR is only ~4.2dB away from the theoretical limit.

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Multi-aperture digital coherent combining for free-space optical communication receivers

Cited by 83 publications

References 39 publications

Structured Light in Turbulence

Structured Light in Turbulence

Experimental demonstration of multi-aperture digital coherent combining over a 3.2-km free-space link

Design of the Real-Time Single-Photodiode Digital Coherent Receiver Suitable for Free Space Optical Communication

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