Pulse sharpened On-Off Keying Optical modulation for Power Efficient Satellite Optical Communication

Low-earth orbit satellite communications are expected to be the next-generation global wireless network with enhanced data rates. Among them, satellite optical communication (SOC) systems have garnered significant attention owing to their advantages such as wide bandwidth, high directivity, high security, low power consumption, small size, and unregulated spectrum compared with RF-based communication.[l] However, despite its advantages, the SOC link performance deteriorates by various losses such as space loss induced by long distance of hundreds of km and atmospheric losses. To overcome such optical power losses, various optical modulation methods such as pulse position modulation (PPM), and differential phase shift keying (DPSK) have been conventionally used. However, high-order PPM require more bandwidth. Thus the spectral efficiency of PPM is relatively low compared with on-off keying (OOK). DPSK also requires complex structure such as pre-amplifier and balanced detector. [2]