Mode Conversion for Mode Division Multiplexing at 850 nm in Standard SMF

A mechanical mode converter for mode division multiplexed systems over SSMF at 850 nm is proposed and evaluated experimentally by the transmission of OOK-modulated optical signals. The proposed mode converter is based on a periodic structure defined by the grating period (A) parameter and the number of mode coupling points, N. A mechanical grating with N=50 points and a tunable grating period (A form 440 to 456 μm) has been designed offering a 124-nm tuning bandwidth. The LP
₀₁
mode to LP
₁₁
mode conversion has been experimentally assessed and a conversion efficiency of 89 % has been achieved in the designed device. Optical transmission of OOK-modulated signals with 1.25 and 2.5 Gb/s bitrates on LP
₀₁
mode or a converted LP
₁₁
mode is demonstrated achieving BER <; 10
^-9
after 1-km optical transmission over SSMF at 850 nm.