All-fiber broadband wavelength-division multiplexing using heterogeneous photonic lanterns

Abstract

This work presents an all-fiber broadband wavelength-division multiplexing architecture using 1×7 heterogeneous photonic lanterns (PLs), specifically PL−(6 + 1) and PL−(4 + 3). By combining mismatched single-mode cores, namely SM450 and SMF28, without rigid geometric constraints, these devices break system degeneracy and enable passive, wavelength-selective spatial routing. Experimental characterization reveals distinct dual-regime performance across a wide spectral range. In the visible band (350–740 nm), the devices function as multi-channel broadband collectors, effectively guiding light across all channels without spatial separation. Conversely, in the H-band (1520–1610 nm), core asymmetries lift mode degeneracy and maximize propagation constant (β −) matching conditions, thereby enabling passive spectral sorting. These results confirm that unconstrained, free-packaged heterogeneous fiber bundles can meet adiabatic transition criteria, showcasing their potential for next-generation astronomical facilities that require simultaneous multi-wavelength capabilities to feed separate, band-optimized spectrographs.