Provided is an optical mode switch that can effect a more compact optical switch. The optical mode switch (100) is provided with: a single input port (1); a single output port (2); two waveguides (10) provided in parallel between the input port (1) and the output port (2); and a refractive index altering means (8) that alters the refractive index of the waveguides. Any given mode light input to the input port (1) is output as any given mode light from the output port (2) in accordance with the refractive index altered by the refractive index altering means (8).

A higher order mode generator is for converting the 0^th order fundamental guiding mode into higher modes higher than the 0^th order in a waveguide. The waveguide is made from thermo-optic materials in which the refractive index is changed according to the applied electrical power. The waveguide has at least two guiding modes and a straight heater or a linear electrode to invoke refractive index perturbation due to temperature or electric field, and is laid across the waveguide at a certain tilt angle α with respect to the waveguide. When there is no external electric power applied to the heater/electrode, the 0^th order single mode light of the waveguide will be propagated through the waveguide without any conversion into higher order modes. When electric power is applied, the refractive index of the waveguide beneath the heater changes and higher order modes can be excited by external control.

The present invention provides a polarizer and a polarization modulation system. The polarizer includes at least one MMI multi-mode waveguide, where one side of each MMI multi-mode waveguide is connected to an input waveguide, and the other side is connected to an output waveguide; an end portion of the side, on which the output waveguide is located, of the MMI multi-mode waveguide is provided with an adjustable portion, and the adjustable portion is connected to the output waveguide; and the polarizer further includes a controller connected to the adjustable portion, where the controller is configured to perform control to change a material property of the adjustable portion, so that the output waveguide outputs optical signals in different polarization states. The present invention implements adjustable polarization, and the structure is simple.

A supercontinuum optical pulse source provides a combined supercontinuum. The supercontinuum optical pulse source comprises one or more seed pulse sources (13), and first and second optical amplifiers (7) arranged along first and second respective optical paths. The first and second optical amplifiers are configured to amplify one or more optical signals generated by said one or more seed pulse sources. The supercontinuum optical pulse source further comprises a first microstructured light-guiding member (9) arranged along the first optical path and configured to generate supercontinuum light responsive to an optical signal propagating along said first optical path, and a second microstructured light-guiding member (9) arranged along the second optical path and configured to generate supercontinuum light responsive to an optical signal propagating along said second optical path. The supercontinuum optical pulse source further comprises a supercontinuum-combining member (5) to combine supercontinuum generated in at least the first and second microstructured light-guiding members to form a combined supercontinuum. The supercontinuum-combining member comprises an output fibre, wherein the output fibre comprises a silica-based multimode optical fibre supporting a plurality of spatial modes at one or more wavelengths of the combined supercontinuum.

A higher order mode generator is for converting the 0^th order fundamental guiding mode into higher modes higher than the 0^th order in a waveguide. The waveguide is made from thermo-optic materials in which the refractive index is changed according to the applied electrical power. The waveguide has at least two guiding modes and a straight heater or a linear electrode to invoke refractive index perturbation due to temperature or electric field, and is laid across the waveguide at a certain tilt angle α with respect to the waveguide. When there is no external electric power applied to the heater/electrode, the 0^th order single mode light of the waveguide will be propagated through the waveguide without any conversion into higher order modes. When electric power is applied, the refractive index of the waveguide beneath the heater changes and higher order modes can be excited by external control.