Analysis of Pulse Modulation Schemes in Underwater Communication Using Different Laser Sources

Under sea optical communication provides huge benefit in data transmission. The optical beam passing through the sea water mainly suffers of particle concentration of salty and other impurities present in it. The water wave movement inside the sea also obstructs healthy signal flow in sea water. To study the effect of sea water communication to the optical signal getting through it, test bench sea water like module has been built. Real time optical signal modulated by different pulse modulation schemes (PAM, PPM, PWM) are set to flow through the undersea water module. At the receiver end the signal is demodulated and measured for 3dB bandwidth, phase jitter and time jitter. The experimentation is repeated for each pulse modulation scheme by varying the concentration of salty particle impurities Using Red laser. Jitter observed in pulse position modulation is very low (9.8373 radians) compared to other pulse modulation schemes making it most preferable for under sea water optical communication. Also, this paper compares the performance measures of using different wavelength lasers such as red and green LASER.