Fiber-Delay-Based Fluorescence-Raman Multifunctional Combined Detection System

To address the low detection accuracy of fluorescence and Raman spectra in spectral measurements, this study proposes a multifunctional detection system based on fiber delay. By utilizing dual-channel synchronized picosecond pulsed lasers to generate time-gated signals, combined with an optical switch group and fiber delay line to construct an adjustable detection window, high-precision synchronous detection of fluorescence lifetime and Raman spectra is achieved using a single-photon avalanche diode (SPAD) detector. Compared with conventional systems, this design integrates structural simplicity with electromagnetic interference resistance, significantly improving fluorescence lifetime precision and Raman signal-to-noise ratio (SNR). Experimental validation with ethanol and Rhodamine B solutions demonstrated the following: when the detection window was adjusted from 1150 ps to 350 ps, the SNR increased by 37.4 %; under a 350 ps window, the Raman SNR was 7-fold higher than that of commercial spectrometers. The measured fluorescence lifetime of Rhodamine B solution was 1.75 ns, within the theoretical range (1.69 ± 0.2 ns), with a spectral centroid shift of 1 nm and a full width at half maximum (FWHM) relative error of 3.57 %, which collectively demonstrates the system’s reliability and practicality.