Effect of temperature and external optical feedback on intensity and phase noise characteristics in single-mode fiber grating Fabry-Perot laser

The combined effect of temperature variation and external optical feedback (OFB) on the relative intensity noise (RIN) and phase noise (FN) characteristics of fiber grating Fabry-Perot (FGFP) laser for the first time, is investigated numerically by modifying the well-known laser rate equations. The temperature dependence (TD) of RIN and FN characteristics is calculated according to TD of laser cavity parameters; not by using the well-known Pankove equation. The effect of external OFB on RIN and FN characteristics is calculated according to its effect on laser threshold carrier density. The simulation of the frequency spectra of RIN and FN are performed by fast Fourier transform (FFT). We show that FBG can be use to control the external OFB level, thereby; controlling noise level of the laser. Results show that the optimum range of working temperature for FGFP laser for low noise characteristic is within ±2 °C from the FBG reference temperature

Improving the characteristics of the modulation response for fiber Bragg grating Fabry-Perot lasers by optimizing model parameters

A unified and comprehensive study on the small-signal intensity and frequency modulation characteristics of a fiber Bragg grating Fabry-Perot (FBG-FP) laser are numerically investigated. The effect of injection current, temperature, external optical feedback (OFB), nonlinear gain compression factor, fiber grating (FG) parameters and spontaneous emission factor on modulation response characteristics are presented. The rate equations of the laser model are presented in the form that the effect of temperature (T) and external optical feedback (OFB) are included. The temperature dependence (TD) of laser response is calculated according to the TD of laser cavity parameters instead of directly using the well-known Parkove equation. It is shown that the optimum external fiber length (L-ext) is 3.1 cm and the optimum range of working temperature for FGFP laser is within +/- 2 degrees C from the FBG reference temperature (T-o). Also, the antireflection (AR) coating reflectivity and the linewidth enhancement factor have no significant effect on the modulation spectra. It is also show that modulation response is extremely sensitive to the OFB level, high injection current and gain compression factor. The study indicates clearly that good dynamic characteristic can be obtained by system parameters optimization

Comment on: “Theoretical calculation of turn-on delay time of VCSEL and effect of carriers recombination” [Opt. Laser Technol. 39 (2007) 997–1001]

Zhang et al. [Opt.Laser Technol.39 (2007) 997–1001], through theoretical calculation,have shown that the turn-on time delay can be reduced by increasing any of the non-radiative (Anr), radiative (B), and/or Auger recombination (C) coefficients at a constant injection current over threshold current.Here,we explain that the results presented by that paper are incorrect and the turn-on time delay increases by increasing any of the carrier recombination rate coefficients