Compact cyclic fiber three-mode converter based on mechanical fiber grating.

Area of Science:

• Optical communications
• Photonics
• Fiber optics

Background:

• Mode division multiplexing (MDM) systems face challenges with differential mode group delay (DMGD) and mode-dependent loss (MDL).
• These impairments limit the performance and scalability of high-capacity optical transmission systems.

Purpose of the Study:

• To propose and demonstrate a compact cyclic mode converter (CMC) for MDM systems.
• To eliminate DMGD and MDL using a single mechanical fiber grating.

Main Methods:

• Fabrication of a compact cyclic mode converter (CMC) utilizing a mechanical fiber grating.
• Cyclical interchange of optical modes (LP01, LP11a, LP11b) demonstrated.
• Evaluation of mode conversion through fiber output mode field patterns.
• Assessment of system performance with the CMC integrated into a photonic lantern back-to-back system.

Main Results:

• The CMC successfully achieved cyclical mode interchange among LP01, LP11a, and LP11b modes.
• Introduction of the CMC did not significantly degrade the transmission performance.
• Measured insertion loss was below 5 dB.
• Average crosstalk was lower than -11.3 dB.

Conclusions:

• The proposed CMC offers an effective solution for mitigating DMGD and MDL in MDM systems.
• This device provides a new method to reduce link damage in MDM transmission.
• The CMC is a promising component for advancing high-capacity optical communication networks.