Step-index profile

About: Step-index profile is a research topic. Over the lifetime, 3104 publications have been published within this topic receiving 53199 citations.

Apparatus and method for mode control in a semi-guiding amplifier medium

Abstract: In various embodiments, a semi-guiding optical fiber includes a core having a first refractive index and a high aspect ratio elongated cross-section along a slow axis direction. First and second signal claddings having a second refractive index sandwich the core. A third cladding having a third refractive index substantially surrounds at least side edges of the core. The first refractive index of the core, the third refractive index of the third cladding, and/or the second refractive index of the first and second signal claddings, are selected so as to maximize a differential loss between a lowest order mode propagating in the optical fiber and next order modes so as to discriminate in favor of the lowest order mode and against the next order modes. In another embodiment, a method for mode control in a semi-guiding medium includes controlling either the first refractive index of the core, the second refractive index of the first and second signal claddings, and/or the third refractive index of the third cladding, to maximize a differential loss between a lowest order mode propagating in the optical fiber and next order modes so as to discriminate in favor of the lowest order mode and against the next order modes.

Fiber bandwidth-spectrum studies.

Abstract: This paper presents some thoughts on how to improve the bandwidth spectrum of multimode optical fibers. We consider the signal bandwidth of germanium- and phosphorus-doped fibers with ideal power law refractive index profiles and investigate how the bandwidth as a function of wavelength (bandwidth spectrum) is changed as the ideal index profile is distorted. We also study what happens if two fibers with different undistorted power law profiles are used in cascade. Examples are also given of bandwidth calculations of fibers made with a mixture of germanium and phosphorus dopants. It is shown that such fibers are capable of realizing a bandwidth which exceeds 5 GHz·km over a wavelength range from 0.8 μm to 1.45 μm. Finally, bandwidth vs wavelength curves are computed for several real fibers whose refractive index profiles were measured.

Optical fiber having large effective area and dispersion-compensated optical transmission system

Abstract: An optical fiber is fabricated provided with a refractive index profile having a central core (1); a middle part (2) provided around the outer periphery of the central core and having a lower refractive index than that of the central core; and a cladding (4) provided around the periphery of the middle part and having a higher refractive index than the middle part and a lower refractive index than the central core. This optical fiber has an effective core area of 120 µm 2 or more in an employed wavelength band selected from the range of 1.53∼1.63 µm, and has a cut-off wavelength that is capable of substantially single mode propagation in the aforementioned employed wavelength band. As a result, it is possible to construct an optical transmission system having excellent transmission characteristics in which nonlinearity are decreased.

Analysis of circular fibers with an arbitrary index profile by the Galerkin method.

Abstract: We propose a full-vectorial Galerkin method for the analysis of circular symmetric fibers with arbitrary index profiles. A set of orthogonal Laguerre-Gauss functions is used to calculate the dispersion relation and mode fields of TE and TM modes. Examples are given for both standard step-index fibers and Bragg fibers. For standard step-index fiber with low or high index contrast, the Galerkin method agrees well with the analytical results. In the case of the TE mode of a Bragg fiber it agrees well with the asymptotic results.