Design of PANDA-type elliptical-core multimode fiber supporting 24 fully lifted eigenmodes

Area of Science:

• Optical Fiber Technology
• Photonics
• Telecommunications

Background:

• Multimode fibers are crucial for increasing optical communication capacity.
• Existing multimode fiber designs often require complex digital signal processing to separate modes.
• Developing fibers that support a large number of easily distinguishable modes is essential.

Purpose of the Study:

• To design and characterize a novel PANDA-type elliptical-core multimode fiber.
• To investigate the fiber's ability to support a high number of separated eigenmodes.
• To assess the fiber's suitability for practical fabrication and broadband applications.

Main Methods:

• Utilizing a PANDA-type structure with an elliptical core and symmetrical stress-applying parts (SAPs).
• Characterizing eigenmode separation using effective index differences (Δn_eff) across the C band.
• Analyzing fiber bending effects via conformal mapping.
• Evaluating ultra-broadband performance across the C+L bands (1530–1625 nm).

Main Results:

• The designed fiber supports 24 fully separated eigenmodes.
• The minimum effective index difference between adjacent modes exceeds 1.35×10^-4 over the C band.
• Fiber geometric dimensions and doping concentrations are deviation tolerant and compatible with existing manufacturing capabilities.
• Ultra-broadband performance is confirmed over the C+L bands.

Conclusions:

• The novel PANDA-type elliptical-core fiber offers a promising solution for high-capacity optical communication.
• The fiber design facilitates direct fiber vector eigenmode-division multiplexing (EDM) combined with wavelength-division multiplexing (WDM).
• This approach eliminates the need for complex multiple-input multiple-output (MIMO) digital signal processing, simplifying system implementation.