Long-range and high-precision localization method for underwater bionic positioning system based on joint active-passive electrolocation.

Active electrolocation organ of weakly electric fish act as a proximity detection system with high accuracy in recognizing object parameters such as size and shape. In contrast, some fish with passive electrolocation organ are able to detect objects at a greater range. This paper proposes a joint active-passive electrolocation algorithm for long-range and high-precision underwater localization, inspired by the active and passive electroreceptive organs of fish.

Magnetic field measurement based on a fiber laser oscillation circuit merged with a polarization-maintaining fiber Sagnac interference structure.

A compact optical magnetic field sensor based on a fiber laser oscillator circuit merged with a Sagnac loop that contains a polarization-maintaining fiber (PMF) and a magnetostrictive rod is proposed. The combination of the PMF-Sagnac loop and fiber laser oscillation circuit significantly increases the signal-to-noise ratio of the reflection spectrum in the system, which is a mixed spectrum that includes interference fringes and lasers. For the proposed system, an erbium-doped fiber amplifier is used to provide gain, a dispersion compensating fiber is used to compensate for dispersion in the system, a PMF is inserted in the Sagnac loop as a microwave filter, while a section of the PMF is bonded to a magnetostrictive rod to achieve magnetic field sensing.