With the maturity of various fiber optic devices, more and more applications of fiber optics in lidar, especially the use of fiber arrays to solve the problems encountered in lidar detection.
The laser pulse emitted by the laser is emitted after the pulse modulation and beam expansion system and irradiates the target. The scattered echo pulse is converged on the focal plane through the focusing lens, that is, the front face of the optical fiber array. An area scanning device is placed on the front end to control the transmission of light so that only one small array area has light passing through at a time, and then through the optical fiber, it is received by a separate photodetector, and then the signal is processed and imaged.
If you design a 16×16 fiber array, divided into 16 areas, the first optical fiber of each area is bundled at the back end, as the first optical fiber, is connected to the first photodetector; The second optical fiber in each area is bundled into a bundle at the back end, as the second optical fiber, connected to the second photodetector... similarly until the 16th optical fiber is connected to the 16th photodetector. Through this structural design, and placing a spatial light modulator at the front end of the optical fiber array for scanning, it is ensured that only one area receives light at a time so that the 16 detectors at the back end can receive signals from only one area at the same time.
For the optical fiber array unit imaging laser radar system, the echo signal is coupled through the lens fiber, and the coupling efficiency is not high due to end-face reflection. The numerical aperture of a single-mode fiber is usually 6°~7°, and the numerical aperture of a multi-mode fiber is usually 10°~13°, so the use of a multi-mode fiber with a larger numerical aperture will greatly improve the received power. Moreover, the shorter the length of the optical fiber in the system, the larger the dispersion of the multi-mode optical fiber, which has little effect on the signal. Therefore, the system selects multimode fiber for the reception.