Xinglin Zeng

All-Fiber Broadband Degenerate Mode Rotator for Mode-Division Multiplexing Systems

An all-fiber broadband degenerate mode rotator for the rotation between arbitrary degenerate modes is proposed and investigated numerically. Furthermore, the rotator combined with a mode selective coupler (MSC) can be used to realize mode multiplexing. The mode multiplexing can be implemented in one physical dimension, which is considered easier than 3-D cascading MSCs. It is found that the rotator for any two degenerate modes rotation possesses a high rotating efficiency from 1450 to 1650 nm, and the insertion loss at the interconnection of a fiber-based rotator and a normal fiber is lower than 3 dB for any modes. Moreover, the rotators in performance are not sensitive to the four geometrical parameters of design. Finally, a six-mode multiplexer using the proposed rotator combined with MSC is modeled and analyzed. It is shown that multiplexing efficiencies of higher than 70% and mode extinction ratios of more than 20 dB for mode LP01, LP11a/LP11b, LP21a/LP21b, and LP02 are achieved in the C-band.

Experimental Investigation of LP 11 Mode to OAM Conversion in Few Mode-Polarization Maintaining Fiber and the Usage for All Fiber OAM Generator

In this paper, the LP₁₁ mode evolution in a few mode-polarization maintaining fiber is experimentally investigated. Selective conversion from the LP₁₁a/LP₁₁b mode to the LP₁₁b/LP₁₁a , OAM₊₁, and OAM_-1 modes are demonstrated with varying wavelengths and fiber lengths. This property may have nice applications in spatial division multiplexing (SDM) systems, and one of them, i.e., the all-fiber compact and robust scalar orbital angular momentum (OAM) generator, which is cascaded by a mode-selective coupler and a few mode-polarization maintaining fiber, is also demonstrated with expected performance for conversion between LP₀₁ mode and OAM₊₁/OAM_-1.

Tunable mode rotator for space-division multiplexing based on a few mode-polarization maintaining fiber

In this paper, a fiber-based tunable mode rotator is proposed and demonstrated by using the few mode-polarization maintaining fiber (FM-PMF). The mode birefringence in the FM-PMF causes phase difference between two orthogonal degenerate modes. With rotating the FM-PMF segment and getting a variation of aligning angle between the injected LP11 (LP21) mode axis and FM-PMF axis, another intended LP11 (LP21) mode with a certain orientation can be controllably generated at the FM-PMF output.

Elliptical-core mode-selective photonic lanterns for MIMO-free mode division multiplexing systems

We design a three mode elliptical-core mode-selective photonic lantern (EC-MSPL) which can match well with the elliptical core few mode fiber in MIMO-free MDM systems. The mode crosstalk of the EC-MSPL are below −20dB for all three modes.

Experimental measurement of effective refractive index difference for few mode polarization maintaining fibers using S2 method

Polarization maintaining fibers (PMFs) can keep linear polarization state against external perturbations by inducing a high effective refractive index difference (Δneff) along one polarization axis. For few mode polarization maintaining fibers (FM-PMFs), Δneff is applicable between both orthogonal linear polarization modes (e.g. LP01x and LP01y) and orthogonal degenerated modes (e.g. LP11a and LP11b), which can enable advanced functionalities in multiple-input multiple- output-free spatial division multiplexing systems and optical fiber sensing systems. Therefore, the measurement of Δneff for polarization modes and degenerated modes is very important for determining the quality of a FM-PMF. However, measurement of the Δneff for FM-PMFs can be complicated due to the requirement for generating and demultiplexing of the higher order modes (HOMs). In this paper, we propose to measure the Δneff of FM-PMFs using Spatially and Spectrally resolved imaging (S2) method for the first time. The presented method is simply by employing a tunable laser and an IR CCD camera, can avoid any mode converter or mode multiplexer/demultiplexer, featuring a rapid testing speed. A proof-of-concept experiment is carried out to measure FM-PMFs with a length of 1.1m and 5m. The Δneff between the orthogonal polarization modes (i.e. LP11ax-11ay, LP11bx-11by, LP21ax-21ay, and LP21bx-21by) are characterized as 7.05×10-4, 6.91×10-4, 1.02×10-3 and 1.04×10-3 respectively. The Δneff of the orthogonal degenerated modes (i.e. LP11ax-11bx, LP11ay-11by, LP21ax-21bx and LP21ay-21by) are also characterized to be 1.39×10-4, 1.24×10-4, 5.61×10-5 and 6.53×10-5 respectively.

Mode evolution in polarization maintain few mode fibers and applications in mode-division-multiplexing systems

In few-mode polarization-maintaining-fiber (FM-PMF), the effective-index splitting exists not only between orthogonally polarization state but also between degenerated modes within a high-order mode group. Hence besides the polarization state evolution, the mode patterns in each LP set are need to be analyzed. In this letter, the completed firstorder mode (LP11 mode) evolution in PM-FMF is analyzed and represented by analogous Jones vector and Poincarésphere respectively. Furthermore, with Jones matrix analysis, the modal dynamics in FM-PMFs is conveniently analyzed. The conclusions are used to propose a PM-FMF based LP11 mode rotator and an PM-FMF based OAM generator. Both simulation and experiments are conducted to investigate performance of the two devices.

All fiber based broadband mode-selective couplers with 200nm wavelength bandwidth

An all-fiber based tapered mode selective coupler (AFTMSC) is proposed and it can convert LP01 mode to higher-order modes (LP11, LP21 and LP02 mode) with coupling efficiency better than 70% in wavelength range of 1450nm to 1650nm.