Abstract: An optical fiber filter includes a fiber core, inner cladding, and outer cladding. A refractive index of the fiber core, a refractive index of the inner cladding, and a refractive index of the outer cladding progressively decrease in sequence. The fiber core is configured to transmit at least two mutually different first optical signal modes, the inner cladding is configured to transmit at least two mutually different second optical signal modes, and at least one fiber grating is etched on the fiber core. At least part of optical power of a target first optical signal mode is coupled to only a target second optical signal mode at the fiber grating. The target first optical signal mode is one of the at least two first optical signal modes, and the target second optical signal mode is one of the at least two second optical signal modes.

Abstract: An optical fiber filter includes a fiber core, inner cladding, and outer cladding. A refractive index of the fiber core, a refractive index of the inner cladding, and a refractive index of the outer cladding progressively decrease in sequence. The fiber core is configured to transmit at least two mutually different first optical signal modes, the inner cladding is configured to transmit at least two mutually different second optical signal modes, and at least one fiber grating is etched on the fiber core. At least part of optical power of a target first optical signal mode is coupled to only a target second optical signal mode at the fiber grating. The target first optical signal mode is one of the at least two first optical signal modes, and the target second optical signal mode is one of the at least two second optical signal modes.

Abstract: A method, device, system for realizing polarization mode dispersion (PMD) compensation are provided. The method for realizing PMD compensation includes: de-multiplexing a polarization-multiplexed optical signal, to obtain a first polarization light and a second polarization light; and joint-equalizing the first polarization light and the second polarization light, to obtain a first equalization signal and a second equalization signal. Since the polarization-multiplexed optical signal is de-multiplexed and then joint-equalized, not only the intra-channel symbol interference but also the inter-channel symbol interference during transmission of the polarization-multiplexed optical signal is eliminated, so as to realize the PMD compensation.