Equilibrium mode distribution

About: Equilibrium mode distribution is a research topic. Over the lifetime, 928 publications have been published within this topic receiving 14939 citations.

Wavelength selective fiber to fiber optical tap

Abstract: Light is coupled out of a first mono-mode optical waveguide such as an optical fiber an into another single mode waveguide through a substantially planar slab waveguide. The first mono-mode optical waveguide has a grating impressed within which has refractive index perturbations that reflect predetermined wavelengths of incident light out of a portion of a side of the optical waveguide adjacent the grating; The slab planar waveguide has an end optically coupled to the portion of the first mono-mode optical waveguide, for guiding light coupled out of the side of the waveguide, and for maintaining a uni-phase wavefront of said light by having a response that confines the light to a single mode in one dimension, and multi-mode in another dimension and allows at least a portion of the light to converge.

Wavelength dependent phase delay device

Abstract: Mach-Zehnder device (10) includes a delay element (17) in one arm (18) which delays propagation of light at a first wavelength relative to propagation of light at a second wavelength. The delay element (17) may be made up of a grating having a period which causes coupling of the first wavelength from a first mode into a second mode. In another aspect, the invention includes a second grating (30) positioned downstream from the first grating (29) and having a period which causes coupling of the portion of light from the second propagation mode back into the first propagation mode. Also disclosed is an optical waveguide in which light at a wavelength μ can propagate in at least a first and a second mode. The waveguide has an effective index of refraction n1 with respect to the first propagation mode of μ, and an effective index of refraction n2 with respect to the second propagation mode. A grating formed in said waveguide and having a period approximately equal to(μ/2)(n1 - n2).

Mode Beating Analysis by Sample Stretching and Wavelength Sweeping in a Few-Mode Fiber

Abstract: We analyze the beating of coherently copropagating modes in a few-mode optical fiber using two complementary techniques, which involve respectively stretching the sample under examination and sweeping the wavelength for different polarizations of the incoming light. We show that analyzing the spectral composition of the intensity fluctuations allows for a direct measurement of the difference between the mode propagation constants and between their group delays, and we observe the lifting of the mode degeneracy, most possibly induced by residual anisotropies and birefringence. The outlined methodology can be used for the modal characterization of few-mode fibers employed in sensing and in spatially-multiplexed communications.

Calculation of the coupling coefficient in step index glass optical fibers

Abstract: A method for calculating the coupling coefficient in step-index multimode optical fibers is verified for glass fibers by comparison to published data and to an analytical solution for the steady-state mode distribution. The coefficient that the method calculates is used to determine the state of mode coupling along the fiber, including the coupling length for achieving the equilibrium mode distribution when measurement of fiber characteristics (such as linear attenuation or bandwidth) becomes meaningful.

Mode matching for a passive resonant ring laser gyroscope

Abstract: An analytical method of matching the mode of an input laser to the lowest-order mode of a passive resonant ring laser gyro is described, as are the steps in determining the location and focal length of cylindrical mode matching lenses. Results were obtained with no mode matching, with a compromise spherical lens, with horizontal mode matching only, and with the proper cylindrical mode matching lenses. Compared with no mode matching, the latter case shows that the amplitude of the lowest-order mode is increased ∼2.5 times. In addition, the number and intensity of higher-order modes are reduced to near zero, and the relative intensity of the lowest-order mode to the higher-order mode increased from ∼5 to ∼60 times greater.