• optical preamplifier
• ppm
• ase
• photon-starved optical link
• photon-efficiency
• photodetector
• snspd
• spad
• photodiode
• ccsds
• matlab
• deep space optical communications

Optical wireless links are of great interest in space communications. Laser communications enable spacecrafts to carry smaller and lighter transceiver equipment. The increased directionality of optical transmitters (laser+telescope) implies a reduction of the power losses towards directions far away from the intended receiver. Thus, power consumption decreases or higher transmission rates are allowed. Laser communications are the most promising technology for long-haul communications, such as deep space communications, which may exhibit a photon-starved regime, according to distance and transmitted power. In order to exploit maximum capacity from the optical link, photon efficient modulations have been developed. For example, m-PPM could ideally carry up to log_2(m) bits per photon.

The first part of my activities is a scientific literature review on the main communication technologies for space applications, with a particular focus on photodetectors. Specifically, I carried out a survey on single-photon detection technologies, employable in terminals for photon-starved links.

In the second part of my activities, I design and implement receiver algorithms for PPM reception, assisted by the Codeword Synchronization Marker defined in the CCSDS standards. I investigate the selection of the PPM slot threshold for a lower complexity and memory efficient synchronization and detection algorithm. Finally, a performance comparison among various detection schemes has been simulated.