Idealphotonics' narrow-linewidth single-frequency laser at 1550 nm operates near the 1550 nm wavelength (the core window of the optical fiber communication C-band) and features both single longitudinal mode operation and ultra-narrow spectral linewidth.It offers Hz- to kHz-level ultra-narrow linewidth, strictly single-longitudinal-mode output, and extremely low phase noise. It is fully compatible with the low-loss transmission window of fiber communications, and combines long coherence length (>30 km) with high frequency stability, making it an ideal light source for precision measurement, quantum technologies, and high-speed coherent communication.