Aiming at the phenomenon of the narrowness of the output spctrum form the narrow linewidth laser in the micro-ring resonant cavity underwater acoustic sensing system

which makes it difficult to be locked

leading to drift in optical transmission power and causing inaccurate acoustic sensing results

a under water acoustic sensing control systemis designed

primarily comprises a signal demodulation system and a digital frequency-locking control system.The signal demodulation system employs high-frequency sinusoidal wave signals to modulate the incident light field and utilizes the transmission spectrum for synchronous demodulation

output the demodulated signal as an error signal.The digital frequency-locking control system is mainly consists of a signal acquisition circuit and an incremental PI digital frequency-locking circuit.Under the control of a field programmable gate array(FPGA)

it collects the error signals

and locks the operating frequency point to the resonant frequency point.Then

the system feeds the scanning signal back to the laser

ensuring its output matches the frequency requirements of the micro-ring resonant cavity and the entire system

thereby enhancing the system’s performance and stability.Test results show that the sensing system can achieve locking onto the resonant frequency of the micro-ring resonant cavity and can detect acoustic signals at 1kHz.The designed sensor system provides technical support for underwater acoustic detection and related fields.