Laser Linewidth Measurements Using Self-Heterodyne Detection with Total-Reflected Delay Line

As an important parameter in the laser communication system, the narrow linewidth of tunable laser source (TLS) must be measured accurately. Therefore, the linewidth of a TLS was measured with the delayed self-heterodyne detection method in the present work. The total-reflected delay line was used in the measurement system for make full use of 25km single-mode fiber delay line. The measured linewidth of the 1550 TLS is of 127 kHz, in agreement with the nominal value.