Temperature Insensitivity Polarization-Controlled Orbital Angular Momentum Mode Converter Based on an LPFG Induced in Four-Mode Fiber

• Main Authors: Shen Liu, Yan Zhang, Cailing Fu, Zhiyong Bai, Ziliang Li, Changrui Liao, Ying Wang, Jun He, Yu Liu, Yiping Wang
• Format: Article
• Language: English
• Published: MDPI AG 2018-06-01
• Series: Sensors
• Subjects: fiber sensor; long period fiber grating; CO2 laser micromachining; temperature sensitivity; few-mode fiber
• Online Access: http://www.mdpi.com/1424-8220/18/6/1766
• ISSN: 1424-8220

We propose a novel method for generating ±1-order orbital angular momentum (OAM) in long-period fiber gratings (LPFGs) by adjusting a polarization controller (PC). An LPFG, inscribed in a four-mode fiber (4MF) using a CO2 laser, was used to generate OAM±1 across a broad range of wavelengths from 1530 nm to 1630 nm. Additionally, the OAM vortex phase remained stable while the temperature increased from 23 °C to 50 °C. The LPFG, as a temperature sensor, and its temperature sensitivity was measured to be 38.6 ± 0.37 pm/°C at the resonant wavelength of 1625 nm. This design offers simple fabrication and several properties which are highly beneficial for all-fiber optical communications based on the OAM mode-division multiplexing technique.