Core selective switches (CSS) enable low-insertion-loss, low-crosstalk optical routing for multicore fiber networks, supporting scalable spatial channel connectivity.

Overview of Core Selective Switches

A core selective switch (CSS) is an optical spatial switch designed to route signals between individual cores of a multicore fiber (MCF) with minimal loss. Recent designs employ microlens-based MCF collimator arrays combined with MEMS mirror arrays, allowing precise alignment and polarization-independent high reflection across a wide wavelength range (1500–1630 nm) while maintaining compact form factors (~50 mm) (source: ).

Key Performance Metrics

• Insertion Loss: CSS prototypes demonstrate low insertion loss ranging from 1.2 to 2.7 dB, which is critical for maintaining high optical signal-to-noise ratio (OSNR) in long-haul or high-capacity networks (source: ).
• Polarization Dependent Loss (PDL): Less than 0.25 dB, ensuring consistent performance regardless of signal polarization (source: ).
• Crosstalk: Low crosstalk (<30 dB) between cores minimizes interference, which is essential for multicore fiber systems where multiple spatial channels operate simultaneously (source: ).
• Wavelength Range: Operates effectively over C-band, S-band, and L-band, supporting ultra-wideband optical communication without signal degradation (source: ).

Applications

CSS devices are particularly suitable for:

• Spatial Division Multiplexing (SDM) networks: Enhancing capacity beyond single-mode fiber limits by routing multiple cores independently (source: ).
• Submarine optical systems: Where low loss and low power consumption are critical, and fan-in/fan-out devices connect MCFs to standard single-mode fibers (source: ).
• High-capacity data centers and metro networks: Where scalable, low-loss switching is required for multicore fiber deployments.

Design Considerations

• Multicore Fiber Selection: Using uncoupled MCFs with low propagation loss (e.g., 0.155 dB/km) and low inter-core crosstalk (<–60 dB/100 km) is essential to maximize CSS performance (source: ).
• Alignment Precision: Microlens arrays ensure accurate coupling between MCF cores and collimators, reducing insertion loss.
• MEMS Mirrors: Provide high reflection efficiency and wide tilt angles, enabling flexible routing without introducing significant loss (source: ).
• Fan-in/Fan-out Devices: Required to interface MCFs with conventional single-mode fibers while maintaining low loss and minimal crosstalk (source: ).

Summary

Low-loss core switches like CSS are critical for next-generation optical networks, enabling high-capacity, low-latency, and low-power signal routing across multicore fibers. By combining precise optical alignment, MEMS technology, and optimized MCFs, these switches achieve low insertion loss, minimal crosstalk, and wideband operation, making them suitable for SDM, submarine, and data center applications.