High sensitivity receivers for free-space optical communication links
Doktorsavhandling, 2024
Space exploration today rely on radio frequency (RF) technologies to transmit data collected by space missions back to earth. Such RF communication links constitute a bottle-neck for new discoveries as their data rates fail to keep up with that generated by sophisticated instrumentation aboard modern space probes and rovers. As RF is reaching the limits of its capacity, the emerging technology of laser-based space communication is poised for take-over of future short- and long range space networks. The reduced diffraction loss of shorter wavelength-transmission is the driving factor behind this development which offers the opportunity to resolve the RF bottle-neck of deep space communications, if paired with efficient data modulation and sensitive reception.
A receiver technology offering both high sensitivity and spectral efficiency is that of optically pre-amplified coherent detection. When paired with a phase sensitive amplifier (PSA) as pre-amplifier, it provides the highest sensitivity for any coherent modulation format. Such a receiver could significantly boost both communication throughput and reach. However, the implementation of PSAs and coherent detection for large-area receivers is non-trivial as it requires single-mode reception and phase-locking of the received signal wave in practice.
This thesis addresses these practical challenges by (I): investigating different telescope architectures such as multi-mode and multi-aperture solutions, together with coherent combining of signals for realizing efficient and sensitive large-area single-mode coupled receivers; and by (II): simplifying the phase-locking of PSAs for practical free-space links. Results and demonstrations reported within this work showcases the possibility to achieve high data rate sensitive links and constitute important steps towards the practical implementation of PSA-preamplified large-area receivers for deep space communications.
A receiver technology offering both high sensitivity and spectral efficiency is that of optically pre-amplified coherent detection. When paired with a phase sensitive amplifier (PSA) as pre-amplifier, it provides the highest sensitivity for any coherent modulation format. Such a receiver could significantly boost both communication throughput and reach. However, the implementation of PSAs and coherent detection for large-area receivers is non-trivial as it requires single-mode reception and phase-locking of the received signal wave in practice.
This thesis addresses these practical challenges by (I): investigating different telescope architectures such as multi-mode and multi-aperture solutions, together with coherent combining of signals for realizing efficient and sensitive large-area single-mode coupled receivers; and by (II): simplifying the phase-locking of PSAs for practical free-space links. Results and demonstrations reported within this work showcases the possibility to achieve high data rate sensitive links and constitute important steps towards the practical implementation of PSA-preamplified large-area receivers for deep space communications.
Phase sensitive amplifier
Optical phase-locked loop
Noise figure
sensitivity
Coherent combining
multi-aperture receiver
Kollektorn, MC2 floor 4, Kemivägen 9
Opponent: Zhixin Liu, University College London - Department of Electronic and Electrical Engineering, United Kingdom
Författare
Rasmus Larsson
Chalmers, Mikroteknologi och nanovetenskap, Fotonik
Coherent combining of low-power optical signals based on optically amplified error feedback
Optics Express,;Vol. 30(2022)p. 19441-19455
Artikel i vetenskaplig tidskrift
Rasmus Larsson, Magnus Karlsson, Peter A. Andrekson. Sensitive optical free-space receiver architecture for coherent combining of deep-space communication signals through atmospheric turbulence
Zero-Offset Frequency Locking of Lasers At Low Optical Powers With an Optical Phase Locked Loop
Journal of Lightwave Technology,;Vol. 42(2024)p. 1183-1190
Artikel i vetenskaplig tidskrift
Low-noise phase-sensitive optical parametric amplifier with lossless local pump generation using a digital dither optical phase-locked loop
Optics Express,;Vol. 31(2023)p. 36603-36614
Artikel i vetenskaplig tidskrift
Rasmus Larsson, Ruwan U. Weerasuriya, Peter A. Andrekson. Ultralow noise preamplified optical receiver using conventional single wavelength transmission
In the modern world we use electromagnetic waves as carriers of information everywhere from the optical fiber network, connecting the different parts of the planet, to the deep space network, relaying images taken by martian rovers back to earth. While the fiber network can sustain you with live streaming of high-definition videos and Gbit/s download speeds, the link connecting Mars and earth cannot. Yet we still send high quality camera and measurement equipment to the red planet that could leverage new discoveries quicker if only the connection was fast enough.
Just as a faint star in the night sky must be bright enough for you to see it, so bright must the data-carrying electromagnetic waves sent from Mars be for the receiver on earth to detect them. The transmitter on Mars has limited power to transmit, it can either allocate that power into fewer data bits with more energy, or more data bits with lesser energy. At risk of the receiver not being able to see ''faint'' bits, the former option is typically preferred, hence the limited speed of current deep-space communications. However, there is a solution.
Due to the wave-nature of electromagnetic radiation, the signal expands through space like the beam from a flashlight widens with distance. Interestingly, if the wavelength of the radiation is shorter, the spreading is reduced. This is the reason behind the emerging laser space-communication technology we see today. For deep space communications, lasers enable a narrower beam than traditional radio frequencies, which means more power striking the receiver, which in turn could allow more bits per second to be transmitted.
Even more bits per second could be transmitted if both the collecting area of the receiver was increased and the detector noise was decreased. These are the two aspects investigated in this thesis. It turns out that the short wavelength of laser light is a double-edged sword as although we get a narrower beam, we then also require more accurate pointing and high quality telescopes to efficiently focus the light into the sensitive low-noise detector. Here we consider different telescope designs and free-space to detector-coupling technologies for efficient detection. We also consider a specific type of detector based on a phase-sensitive optical amplifier that can amplify the light with half as much noise as commonly used amplifiers. The implementation of phase sensitive amplifiers do however require the received wave to be synchronized with the detector which poses significant practical challenges, many of them we solve within this thesis.
Just as a faint star in the night sky must be bright enough for you to see it, so bright must the data-carrying electromagnetic waves sent from Mars be for the receiver on earth to detect them. The transmitter on Mars has limited power to transmit, it can either allocate that power into fewer data bits with more energy, or more data bits with lesser energy. At risk of the receiver not being able to see ''faint'' bits, the former option is typically preferred, hence the limited speed of current deep-space communications. However, there is a solution.
Due to the wave-nature of electromagnetic radiation, the signal expands through space like the beam from a flashlight widens with distance. Interestingly, if the wavelength of the radiation is shorter, the spreading is reduced. This is the reason behind the emerging laser space-communication technology we see today. For deep space communications, lasers enable a narrower beam than traditional radio frequencies, which means more power striking the receiver, which in turn could allow more bits per second to be transmitted.
Even more bits per second could be transmitted if both the collecting area of the receiver was increased and the detector noise was decreased. These are the two aspects investigated in this thesis. It turns out that the short wavelength of laser light is a double-edged sword as although we get a narrower beam, we then also require more accurate pointing and high quality telescopes to efficiently focus the light into the sensitive low-noise detector. Here we consider different telescope designs and free-space to detector-coupling technologies for efficient detection. We also consider a specific type of detector based on a phase-sensitive optical amplifier that can amplify the light with half as much noise as commonly used amplifiers. The implementation of phase sensitive amplifiers do however require the received wave to be synchronized with the detector which poses significant practical challenges, many of them we solve within this thesis.
Brusfria optiska faskänsliga förstärkare och dess tillämpningar
Vetenskapsrådet (VR) (2015-00535), 2016-01-01 -- 2025-12-31.
Ämneskategorier
Telekommunikation
Atom- och molekylfysik och optik
Reglerteknik
ISBN
978-91-8103-085-3
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5543
Utgivare
Chalmers
Kollektorn, MC2 floor 4, Kemivägen 9
Opponent: Zhixin Liu, University College London - Department of Electronic and Electrical Engineering, United Kingdom