Dissertation Defense, Cyril Guintrand

Ph.D. defense

Date: Monday, Nov. 29th, 2010

Time: 12:10 PM

Room: 512 in Lewis Lab

Title: Raman-assisted optical parametric amplification in optical fibers.

Abstract:

Direct optical amplification in fibers has played a critical role in the development of optical communications. It does provide an efficient way to regenerate the signal power along the fiber propagation path which otherwise will be attenuated by intrinsic fiber loss. Also, fiber amplification medium offers the opportunity to design all fiber-based oscillators generating wavelengths not achievable otherwise.

Several amplification schemes relying on different phenomena have been demonstrated and some are now widely used. Among them are the rare-earth doped fiber amplifiers, which can amplify light in specific spectrum windows, depending on the ions used to dope the fiber. EDFA is one successful example of amplification in the C band (1530-1560nm). Also, fiber optical nonlinearity properties have been used to provide amplification. Raman amplifier (RA) based on stimulated Raman scattering (SRS) is a good illustration. More recently, due to available high power pumps, high nonlinear fibers and advantageous fiber dispersion characteristics, fiber optical parametric amplifier (FOPA) has become a serious candidate in the field. A significant advantage of the RA and FOPA is the possibility of obtaining gain at virtually any wavelength, provided the availability of pump wavelength and particular fiber dispersion profile are available. Another specific feature of the FOPA is the creation of a new wave, called the idler, during the amplification process. This characteristic provides a way to achieve wavelength conversion.

We investigate the combined effect of Raman and OPA amplifications in fibers, also mentioned as Raman-assisted optical parametric amplification (RA-OPA). We study the case where two pumps (the first one providing Raman amplification and the second one the parametric amplification) are simultaneously propagating in the fiber with a signal. We present numerical simulations to show evolutions of the waves in the fiber and gain spectrum. We discuss about the gain spectrum for several parameters (pump wavelengths, input power of the pumps).  We show that using a Raman pump in a FOPA can significantly increase the gain and tailor the spectrum shape. Finally, we present experimental results achieved in high nonlinear fiber (HNLF).

Committee Members:

J. Toulouse (advisor)
T. Koch
R. Decker
I. Veltchev