High precision and fast frequency detection method for narrow linewidth laser

• 1、Beijing University of Posts and Telecommunications,State Key Laboratory of Information Photonics and Optical Communications,Beijing 100876

Abstract：Narrow linewidth laser is a key component in coherent optical communication and optical fiber sensing, whoes frequency stability is an important feature in such system. Distributed feedback semiconductor laser (DFB) is often used in optical fiber stimulated Brillouin sensing system. The stability of DFB is required to be within 3MHz, while the frequency drift of narrow linewidth laser with linewidth less than 1MHz can reach several hundred MHz. Based on the reflection spectrum characteristics of fiber Bragg grating, a laser detection method based on the rising edge of fiber Bragg grating is proposed for frequency stabilization feedback control. The high-precision and stable temperature control of FBG is realized by using TEC, high-precision temperature control chip and PID control algorithm with automatic parameter extraction. The experimental results show that the fluctuation range of the temperature control system is about 0.002 C at room temperature, which ensures the stability of the center wavelength of the fiber grating. Under the low-cost MCU built-in 12bit digital to analog conversion (ADC) conversion accuracy, the frequency detection accuracy of the laser can reach 3MHz, and can realize fast detection.

Keywords： optical engineering laser frequency stabilization fiber grating TEC PID temperature control