High-Order Mode Conversion Employing a Fiber Bundle Scheme

In this paper, a transplantable, low-loss, high-purity, and ultra-broadband mode conversion scheme employing a fiber bundle constructed with one single-mode fiber and multiple coreless fibers is proposed. The feasibility of the mode conversion scheme is theoretically demonstrated and experimentally verified through a 9-core LP 41 mode converter. The purity of selectively excited LP 41 mode group is estimated to be 88.74%. The insertion loss of the LP 41 converter is less than 0.40 dB within a measurement bandwidth exceeding 280 nm. And the transplantability of the mode conversion scheme is verified through a 13-core LP 61 mode converter with an insertion loss less than 0.70 dB at 1550 nm, which is the highest order mode conversion achieved so far with an all-fiber structure to the best of our knowledge. This work provides a new implementation scheme for mode converters, which will undoubtedly promote the development of space-division multiplexing technology.