Abstract: The device consists of a dual-mode waveguide 1 that has a longitudinal axis ?X!, a length ?L!, and a width ?W!, and two pairs of monomode waveguides 2, 3 and 4, 5, for entry and exit, respectively. In accordance with the invention, the length ?L! and the width ?W! of the dual-mode waveguide ?1! are selected in such a way as to establish, in this guide, light coupling that is greater in the window from 1260 to 1360 nm than in the window from 1480 to 1580 nm, so as to compensate for the significant contrary proximity coupling in these windows, as created between the monomode entry guides 2 and 3 on the one hand and the monomode exit guides 4 and 5 on the other hand.

Abstract: Disclosed is a single mode optical waveguide fiber which limits nonlinear effects at both the 1300 nm window and the 1550 nm window of operations. Examples of core region refractive index profiles which yield the required properties are a modified step index profile and profiles which have a maximum .DELTA.% which is spaced apart from the centerline of the waveguide fiber.

Abstract: A combination of dispersion flattened single mode optical waveguide fiber and soliton signal pulses yields an optimum telecommunication system capacity. The dispersion flattened fiber serves to relax tolerances on soliton center wavelength and intensity. In addition, the inventive combination facilitates the design and use of long haul systems using optical amplifiers.

Abstract: The present invention relates to a method of measuring spectral attenuation of an optical waveguide fiber using an OTDR. The spectral attenuation curve is generated by analyzing OTDR data taken at three or four wavelengths. There is particular interest in the wavelength range of 1200 nm to 1600 nm, which includes the operating windows about the wavelengths 1310 nm and 1550 nm. A particularly accurate spectral attenuation curve is obtained using OTDR measurements at 1310 nm, 1410 nm, and 1550 nm.