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title: "Ultra-sensitive UV solar-blind optical wireless communications with an SiPM"
date: 2023-10-15T01:12:21
draft: false
category: paper
excerpt: "Optics Letters, first-authored by Feng Liu: a cooled SiPM receives a 275 nm UV link at 1 Mbit/s from just 30 pW, about 41.5 photons per bit."
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::publication[12]

Published in Optics Letters with Feng Liu as first author.
Sunlight at ground level has almost no power in the ~wave:UV solar-blind~ band (200 nm to 280 nm), so an optical wireless link there sees very little ambient light.
This work cools a SiPM to make a receiver sensitive enough to use that band at very low power.

## Abstract

In this Letter, an SiPM with a dedicated cooling system suitable for receiving ultra-low-power solar-blind wavelengths is reported.
This is designed to decrease the temperature of the detector from 21 °C to −10 °C, and the corresponding dark count rate (DCR) is reduced by approximately 10 dB.
A 275 nm optical wireless communication (OWC) system is established using on–off-keying (OOK) modulation.
Transmission rates ranging from 100 kbit/s to 2 Mbit/s are demonstrated with this cooled SiPM.
The received power is as low as 30 pW (corresponding to 41.5 photons per bit) at a data rate of 1 Mbit/s and a bit error rate of $2.4 \times 10^{-3}$.

## Key Findings

At around 40 photons per bit, the receiver is roughly 240 times more sensitive than recent demonstrations, which needed about $10^4$ photons per bit.
The suggested next steps are higher data rates and equalisation to deal with inter-symbol interference.
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