A fiber-coupled single-photon detection system using superconducting nanowire single-photon detectors (SNSPDs) based on amorphous tungsten silicide (WSi) achieved a system detection efficiency (SDE) of over 93% in the wavelength range 1520–1610 nm. The system also demonstrated a device dark count rate of ~1 kcps, timing jitter of ~150 ps FWHM, and a reset time of 40 ns. The SNSPDs were fabricated with WSi nanowires, which are more robust and compatible with various substrates compared to traditional NbN nanowires. This compatibility allows for higher SDE and better performance in terms of dark count rate and timing resolution. The SDE was measured as the ratio of the photoresponse count rate to the number of photons in the SNSPD fiber. The system was characterized over a temperature range of 120 mK to 2 K, showing stable performance with SDE remaining saturated at ~93% at 1550 nm. The system also exhibited low jitter and high detection efficiency, making it suitable for applications requiring high system detection efficiency and low dark count rates. The results demonstrate that WSi SNSPDs can achieve high performance in single-photon detection, with potential for future advancements in mid-infrared detection and large-scale SNSPD arrays.A fiber-coupled single-photon detection system using superconducting nanowire single-photon detectors (SNSPDs) based on amorphous tungsten silicide (WSi) achieved a system detection efficiency (SDE) of over 93% in the wavelength range 1520–1610 nm. The system also demonstrated a device dark count rate of ~1 kcps, timing jitter of ~150 ps FWHM, and a reset time of 40 ns. The SNSPDs were fabricated with WSi nanowires, which are more robust and compatible with various substrates compared to traditional NbN nanowires. This compatibility allows for higher SDE and better performance in terms of dark count rate and timing resolution. The SDE was measured as the ratio of the photoresponse count rate to the number of photons in the SNSPD fiber. The system was characterized over a temperature range of 120 mK to 2 K, showing stable performance with SDE remaining saturated at ~93% at 1550 nm. The system also exhibited low jitter and high detection efficiency, making it suitable for applications requiring high system detection efficiency and low dark count rates. The results demonstrate that WSi SNSPDs can achieve high performance in single-photon detection, with potential for future advancements in mid-infrared detection and large-scale SNSPD arrays.