Er-doped fiber distributed feedback lasers: properties, applications and design considerations

Fiber distributed feedback (F-DFB) lasers have proven to be attractive devices for interrogation of optical sensors with high frequency resolution, due to their very low frequency noise/narrow linewidth, low relative intensity noise (RIN), robust mode-hop free tunability, compact size, and flexible and accurate wavelength setting. It has also been demonstrated that F-DFB lasers can act as sensor elements for high resolution measurements of physical quantities causing strain, refractive index, or birefringence changes in the laser fiber. It has been demonstrated that F-DFB lasers can be used as fast tunable sources for high resolution and high accuracy spectral component characterization. They may also find applications in dense WDM transmission systems utilizing their potentials for accurate wavelength setting, easy wavelength tuning, semiconductor pump redundancy, or multiple wavelength operation. In this paper properties and applications of F-DFB lasers will be discussed, with emphasis on modeling, design and characterization of the devices. In particular, RIN and frequency noise properties, requirements on grating and gain medium quality, the design requirements for achieving singlemoded or (intentionally) multimoded laser operation, and the output characteristics of single- versus multimoded F-DFB laser devices will be treated.