Over 100 nm Bandwidth Orbital Angular Momentum Modes Amplification For MDM and WDM Transmission With a Ring-Core Bi/Er Co-Doped Fiber

We designed and fabricated a ring-core Bi/Er co-doped fiber (RC-BEDF), and thus investigated the broad-spectrum amplification of orbital angular momentum (OAM) modes. The deviation from the average gain of the OAM(1) and OAM(2) modes enabled gains of < 1.8 dB and < 1.9 dB respectively, and the differential mode gain (DMG) between the two modes was < 1.0 dB over 100 nm bandwidth (1525-1626 nm). In particular, the 3 dB bandwidth of the gain spectra exhibited 74 nm (1552-1626 nm) and 69 nm (1557-1626 nm), respectively. Furthermore, four beams of different wavelengths, i.e., 1525, 1560, 1590, and 1626 nm, were separately extracted from the broad spectra to detect the amplified modes, by which the interferograms of first- and second-order OAM modes were obtained. The amplified OAM mode purities of the wavelengths were all above 95%. Moreover, dual-channel combination of the OAM(1) mode at 1550 nm and OAM(2) mode at 1600 nm was amplified, which indicated realization of different-OAM-modes amplification with wavelength-division multiplexing (WDM). Herein, for the first time, we extended the C+L band OAM modes amplification to 1626 nm and achieved OAM multiplexed amplification of WDM signals. This ultra-broad-spectrum and ultra-low-DMG OAM amplification has been widely considered as a promising technology for long-haul mode division multiplexing and WDM fiber-optics communication systems and networks.

Automated summary

In this study, a ring-core Bi/Er co-doped fiber was designed and fabricated for broad-spectrum amplification of OAM modes. The gains of OAM(1) and OAM(2) modes deviated from the average gain, with gains being less than 1.8 dB and 1.9 dB respectively. The differential mode gain (DMG) between the two modes was less than 1.0 dB over a 100 nm bandwidth. The amplification of OAM modes was achieved at wavelengths up to 1626 nm, allowing for OAM multiplexed amplification of WDM signals.