Mode add-drop technology based on few-mode fiber Bragg gratings

Area of Science:

• Optical Communications
• Photonics
• Fiber Optics

Background:

• Mode-division multiplexing (MDM) enhances optical fiber transmission capacity by utilizing multiple transmission modes.
• Mode add-drop technology is crucial for flexible networking within MDM systems.

Purpose of the Study:

• To report a novel mode add-drop technology based on few-mode fiber Bragg gratings (FM-FBG) for MDM systems.
• To improve the performance and implementation of mode add-drop functionality in MDM.

Main Methods:

• Fabrication of FM-FBGs by writing gratings in parallel, matching optical field distribution of different modes.
• Utilizing Bragg grating reflection characteristics for add-drop functionality.
• Experimental verification in a 3x3 MDM system with quadrature phase shift keying (QPSK) modulation and coherence detection.

Main Results:

• Demonstrated excellent transmission, add, and drop of 3x8 Gbit/s QPSK signals over 8 km of few-mode fiber.
• Achieved high self-coupling reflectivity for high-order modes by adjusting grating spacing.
• Verified the effectiveness of the FM-FBG based mode add-drop technology.

Conclusions:

• The developed FM-FBG mode add-drop technology offers a high-performance, simple, low-cost, and easily implementable solution for MDM systems.
• This technology enables flexible networking and capacity enhancement in optical communication systems.
• The technology requires only basic components like Bragg gratings, fiber circulators, and optical couplers.