A Dual-Wavelength Fiber Ring Laser Incorporating an Injection-Coupled Optoelectronic Oscillator and Its Application to Transverse Load Sensing

A novel configuration for a dual-wavelength fiber ring laser with improved lasing stability realized through the use of an injection-coupled optoelectronic oscillator (OEO) is proposed and demonstrated, and its application to transverse load sensing is studied. The OEO-coupled dual-wavelength laser has two mutually coupled loops: the fiber ring loop and the OEO loop. In the fiber ring loop, a polarization-maintaining phase-shifted fiber Bragg grating is incorporated to generate two optical wavelengths with the wavelength spacing determined by the birefringence of the polarization-maintaining (PM) fiber. In the OEO loop, a microwave signal with its frequency also determined by the birefringence of the PM fiber is generated, which is fed into the fiber ring loop to injection lock the dual wavelengths. Due to the injection locking, a very stable dual-wavelength operation is established. The use of the dual wavelengths for high-resolution and high-speed transverse load sensing is then implemented. The sensitivity of the transverse load sensor is measured as high as +9.7573 and -9.7350 GHz/(N/mm), along the fast and slow axes, respectively. The high frequency purity and stability of the generated microwave signal permits very reliable and high accuracy measurement and the microwave frequency interrogation allows the system to operate at an ultra-high speed.