Weak signal detection based on pulse width counting method for underwater wireless optical communication with an...

Area of Science:

• Optical Engineering
• Wireless Communication
• Signal Processing

Background:

• Underwater wireless optical communication (UWOC) systems face challenges in detecting weak signals, especially with analog mode photomultiplier tube (PMT) detectors.
• Existing methods like pulse amplitude detection (PAD) and pulse peak counting (PPC) have limitations in sensitivity and performance under weak light conditions.

Purpose of the Study:

• To propose and evaluate a novel weak signal detection method based on pulse width counting (PWC) for on-off keying (OOK) UWOC systems.
• To investigate the signal output model of analog mode PMTs in weak light and analyze the impact of pulse overlap.
• To compare the performance of the PWC method against PAD and PPC under various operational parameters.

Main Methods:

• Development of a pulse width counting (PWC) algorithm for weak signal detection in OOK UWOC systems.
• Modeling the analog mode PMT signal output and accounting for pulse overlap effects.
• Experimental validation of the PWC method in a 7-meter tank, testing different sampling rates, detection thresholds, data rates, and received optical powers (ROPs).

Main Results:

• The proposed PWC method achieved a sensitivity of -71.5 dBm for a 10-Mbps OOK UWOC link over 7 meters, with a total link attenuation of 94.8 dB.
• PWC demonstrated superior performance, showing 1.1-dB and 3.8-dB improvements in sensitivity compared to PPC and PAD, respectively.
• The system successfully utilized an analog mode PMT, leveraging its larger dynamic range for effective weak light signal detection.

Conclusions:

• Pulse width counting (PWC) is an effective method for enhancing weak signal detection in OOK UWOC systems utilizing analog mode PMTs.
• The PWC technique offers significant sensitivity improvements over traditional methods, paving the way for more robust and longer-range underwater optical communication.
• The use of analog mode PMTs with PWC is advantageous for designing advanced, long-distance UWOC systems.