Pulse-Sharpened OOK Optical Transmission Using MZDI With Saturated EDFA in Space Laser Communication

Free space optical communication has attracted attention owing to its diverse advantages in satellite communication. However, satellite optical communication requires high optical power to overcome diverse losses. This paper proposes a new modulation method that increases the 3 dB optical power of the on-off keying signal without adding additional bandwidth using a single Mach-Zehnder delay interferometer (MZDI) and saturated erbium-doped fiber amplifier (EDFA) at the transmitter. Owing to the average-limiting property of the EDFA, reducing the effective duty cycle ratio increases the peak output optical power of the saturated EDFA. The duty cycle of the optical signal can be reduced by using a MZDI at the transmitter. Mathematical analysis, simulation, and proof-of-concept experiment of the proposed schemes were performed.