Ultralow-crosstalk and high-resolution integrated Echelle grating as interrogator for FBG sensing

A silica-based planar echelle grating (PEG) with high resolution and ultra-low crosstalk is designed, fabricated, and characterized for an integrated spectrometer optimized for C-band operation. By leveraging mature silica waveguide fabrication technology and a large Rowland circle, the PEG exhibits both excellent robustness and superior optical performance. The experimental results demonstrate lowest on-chip loss of 0.9 dB across 14 output channels, with an average inter-channel crosstalk of -45 dB. The device further achieves a narrow 3-dB bandwidth of 0.24 nm, corresponding to a resolving power exceeding 6000, together with a highly accurate realization of the designed 1.5 nm channel spacing. These results highlight silica PEGs as robust, high-performance candidates for wavelength-division multiplexers in fiber-optic communication networks and as spectroscopy interrogators in fiber Bragg grating sensing systems for the precise determination of wavelength shifts.