Abstract
Using numerical simulations of thermally induced mode coupling we show how the instability threshold can be substantially reduced if the pump or injected signal is modulated in the kHz range. We also show how the mode coupling gain varies with the frequency offset of the parasitic mode. We model thresholds when the source of detuned light is quantum background, amplitude modulation of the pump power, and amplitude modulation of the signal seed. We suggest several key experimental and modeling tests of our model.
Highlights
In attempts to scale fiber amplifiers to high power, maximizing the modal area has been an effective way to suppress nonlinearities such as stimulated Brillouin and Raman scattering.Due to practical limitations on refractive index control, large mode area fibers typically support several transverse modes, and this makes them susceptible to a modal instability in which some of the light propagating in the desired LP01 mode is transferred into mode LP11
We constructed a numerical model of the amplifier and used it to first find an equilibrium solution which, in our case, is a set of signal and pump optical fields defined along the length of the fiber
We have explained how instability thresholds can be sensitive to the operating conditions, pump or signal modulations combined with slight initial population of LP11
Summary
In attempts to scale fiber amplifiers to high power, maximizing the modal area has been an effective way to suppress nonlinearities such as stimulated Brillouin and Raman scattering. We present a detailed discussion of this question, showing how our model can account for observed threshold powers as well as a sensitivity to operating conditions. We present details of our improved model along with some key modeling results showing dependence of the threshold on operating conditions - namely on modulation of the input signal seed, modulation of the pump, and accidental launch of signal seed light into mode LP11. These factors can act to initially populate LP′11, and our model can make quantitative predictions of the resulting threshold reductions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
