Transverse mode switchable all-fiber high-order mode Brillouin laser

A transverse mode switchable all-fiber high-order mode Brillouin laser, characterized in that:

• the laser comprises a narrow linewidth pump laser, an optical amplifier, a 1×N optical switch (N≥2), a fiber mode selection coupler group, a first polarization controller, a fiber circulator, a fiber coupler, a second polarization controller, and a few-mode fiber;
• the 1×N optical switch comprises one input port and N output ports;
• the fiber mode selection coupler group comprises N fiber mode selection couplers, which are respectively denoted as a first fiber mode selection coupler to an Nth fiber mode selection coupler;
• each of the N fiber mode selection couplers comprises a first port, a second port, a third port, and a fourth port;
• the fourth port of the N−1th fiber mode selection coupler is connected to the third port of the Nth fiber mode selection coupler;
• the fiber circulator comprises a first port, a second port, and a third port;
• the fiber coupler comprises a first port, a second port, a third port, and a fourth port;
• the narrow linewidth pump laser is connected to the optical amplifier, which is connected to the input port of the 1×N optical switch;
• the N output ports of the 1×N optical switch are respectively connected to the first ports of the N fiber mode selection couplers;
• the fourth port of the Nth fiber mode selection coupler is connected to the first port of the fiber circulator through the first polarization controller;
• the second port of the fiber circulator is connected to the first port of the fiber coupler;
• the second port of the fiber coupler is connected to the third port of the fiber circulator through the second polarization controller and the few-mode fiber to form a ring cavity;
• and the third port of the fiber coupler outputs laser beams.