Patent ID: 9329416
Filing Date: 2016-05-03
CPC Classification: G02B,G02F,H01S

Claim Text:
1. A method for lowering a number of higher modes in a multimode (MM) beam propagating in a MM fiber, said method comprising: (a) activating at least one phase control actuator to introduce local controlled phase changes in said fiber at the input or output of said fiber; (b) monitoring the electro-magnetic field intensity distribution of the phase corrected beam with at least one of a wavefront sensor and a power sensor; and (c) applying actuator control algorithms to the output of at least one of said wavefront sensor and said power sensor to provide control feedback to said phase control actuators in a closed feedback loop; thereby allowing mode population control with no power loss by shifting higher modes into lower modes; wherein the phase correction takes place within the MM fiber by causing local controlled refractive index changes in at least one of the following ways: (i) applying controlled mechanical stress at least one point along the fiber; (ii) applying electric fields in MM fibers having a considerable electro-optic coefficient; (iii) inserting the MM fiber into a waveguide made of material with a considerable electro-optic coefficient; and (iv) using the magneto-optical Kerr effect in polarization maintaining fibers.