Connet Single Frequency Diode Laser Source is based on single longitudinal mode,ultra-narrow linewidth such as kHz, single frequency semiconductor lasers, such as external cavity laser (ECL) or narrow linewidth DFB semiconductor lasers. The output spectrum of these lasers is pure and the linewidth is in the order of tens of kHz even down to <5kHz. Connet developed external cavity injection narrowing linewidth technology and frequency stabilization to reduce frequency noise narrowing linewidth technology for single-frequency semiconductor lasers. The output fiber is generally a polarization-maintaining fiber. Non-PM fiber can be for selection. Connet uses high-precision current control circuits and temperature control circuits to ensure these light sources have a high degree of output power stability and wavelength stability.