Multi-Wavelength Tunable Fiber Laser using SOA: Application to Fiber Bragg Grating Vibration Sensor Array

A novel multi-wavelength fiber ring laser is proposed in order to construct a thermally stabilized fiber Bragg grating (FBG) vibration sensor array in which detection of multipoint vibrations and temperature compensation of the detection can be achieved. The laser employs a semiconductor optical amplifier (SOA) as a gain medium and FBGs as wavelength selection components. Since the SOA is an inhomogeneous broadening gain medium, stable multi-wavelength oscillation can be realized at the Bragg wavelengths of the FBGs used. The oscillation output from the laser is used for an optical source of wavelength division multiplexed (WDM) FBG vibration sensor array, in which each wavelength component of the output provides one of the optical sources for arrayed FBG vibration sensors. In addition, the wavelength of the laser source can be tuned by applying strain to the FBGs of the laser. The detection scheme of the FBG sensors is based on intensity modulation technique and the thermal stabilization is realized by the wavelength tuning of the laser. In the experiment, a dual-wavelength tunable fiber laser has been fabricated and fundamental characteristics of the laser have been investigated. By applying the laser to the FBG sensor array, simultaneous two-point vibration detection and temperature compensation of the detection have been also demonstrated.

I. Introduction

In recent years, multi-wavelength fiber lasers using semiconductor optical amplifiers (SOAs) have attracted considerable attention in the practical application to fiber optic sensors and optical communication systems [1]–[3]. Since an SOA is an inhomogeneous broadening gain medium, mode competition in multi-wavelength oscillation can be effectively suppressed and stable multi-wavelength lasing output can be provided. Although erbium-doped fiber amplifiers (EDFAs) are widely used for constructing fiber lasers, an EDFA is a homogeneous broadening gain medium generally at room temperature so that some special techniques have to be introduced to suppress the strong mode competition or to enhance the inhomogeneity of the gain medium [4]–[6]. The SOA, therefore, becomes key device to construct multi-wavelength fiber lasers. In this paper, we have developed a novel multi-wavelength tunable fiber laser using an SOA to implement a fiber optic vibration sensor array.