The invention discloses a weak-guide annular-structure
optical fiber. The weak-guide annular-structure
optical fiber comprises an annular
fiber core, a central zone and a cladding. The annular
fiber core has step or gradient type
refractive index distribution, and an auxiliary low-refractive-index annular groove can be disposed in an inner or outer side. A
refractive index difference between the annular
fiber core and the clapping / central zone does not exceed 1%. A
refractive index difference between the annular groove and the clapping / central zone does not exceed -1%. The weak-guide annular-structure
optical fiber only supports a multichannel radial first-order mode and is divided into different mode groups. The other mode groups except for the two front mode groups have large refractive index differences. The front two mode groups can be combined and then be multiplexed through a 6*6
Multiple Input Multiple Output (
MIMO)
digital signal processing assist, the other mode groups are multiplexed through a 4*4
MIMO-DSP assist in each mode group, i.e., inter-mode-group low-
crosstalk multiplexing and small-scale
MIMO-DSP assist
multiplexing in mode groups are combined. Expandability is possessed. A mode base can be a
linear polarization / optical vortex / intrinsic mode. And, the weak-guide annular-structure optical fiber has a C+L waveband
broadband characteristic and is compatible with existing mature optical fiber technology, the communication capacity can be effectively improved through a combination with
wavelength division
multiplexing, and loss can be reduced.