In the optical communicate system, all of the dimensions of the optical wave (the amplitude, frequency, phase and the polarization) have been utilized to carry signal. For further increasing the communicate capacity, the new dimension of the optical wave is required. Mode-division multiplexing (MDM) is considered as a promising technique in which multiple optical modes are used as independent data channels to transmit optical data for doubling the capacity. Mode selective devices are important building blocks for MDM systems.
Ya Gao, who is the PHD student of the WNLO and instructed by Prof. Junqiang sun, experimentally demonstrate mode conversion by exploiting optical reflection of tilted few-mode fiber Bragg grating (FM-FBG). Mode conversions from LP01 mode to higher symmetric and asymmetric modes are achieved, and more than 99.5% conversion efficiency from LP01 to LP11 mode is obtained using a 1.6°-tilted FM-FBG. Influences of the weakly tilted FM-FBG parameters on the property of mode conversion is analyzed and discussed. A simultaneous mode conversion and demultiplexing scheme for 4-mode ´ 3-wavelength multiplexing transmission is proposed and the modal crosstalk is analyzed based on the transmission spectra of the tilted FM-FBGs. The proposed approach shows potential applications in mode and wavelength division multiplexing communication systems
Figure 1: Intensity patterns of the exporting (a) LP01; (b) LP11; (c) LP21 mode; (d) transmission optical spectra corresponding to wavelengths.
This work supported by the National Natural Science Foundation of China under Grant No. 61377074 and 61404056, has been published by Optics Express（Vol. 23, Issue 8, pp. 9959-9967，2015）.