Scalable four-mode cyclic converter based on a semi-inverse design approach

Area of Science:

• Photonics and Optical Engineering
• Telecommunications Technology

Background:

• Mode-division multiplexing (MDM) systems face challenges with differential mode delay and mode-dependent loss.
• Efficient cyclic mode converters are crucial for overcoming these limitations in advanced optical transmission.

Purpose of the Study:

• To present an innovative, high-performance four-mode cyclic mode converter.
• To demonstrate its suitability for practical MDM transmission systems.

Main Methods:

• Utilized a semi-inverse design method to optimize three directional couplers.
• Conducted simulations to evaluate performance metrics like insertion loss and crosstalk.
• Performed experimental validation of the device's characteristics and transmission capabilities.

Main Results:

• Simulated insertion loss < 0.4 dB and crosstalk < -17 dB (1500-1600 nm).
• Experimental low loss (< 1.8 dB) and low crosstalk (<-15 dB) over 1520-1580 nm bandwidth.
• Demonstrated clear eye diagrams at 64 Gbps and 110 Gbps for NRZ-OOK and 4-PPM signals.

Conclusions:

• The developed cyclic mode converter offers excellent performance, scalability, and process tolerance.
• The design is adaptable for more modes and different material platforms.
• This technology promises to significantly reduce link impairments in MDM transmission systems.