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Optical device with a pig tail optical fiber and its production method
| Details |
Inventors: Imoto, Katsuyuki; Hoshino, Hiroyuki;
Assignee: Hitachi Cable, Ltd. (Tokyo, JP)
Primary Examiner: Lee; John D.
Assistant Examiner: Palmer; Phan T. H.
Attorney, Agent or Firm: Antonelli, Terry, Stout & Kraus
An optical waveguide with a specific refractive index difference .DELTA..sub.1 has a constitution in which a core with a high refractive index and having a rectangular section is built in a cladding layer with a low refractive index formed on a substrate. A pig tail optical fiber, formed by a first fiber serially connected to a second fiber, each having a different specific refractive index difference, is connected to an input terminal of the optical waveguide. The second fiber has a specific refractive index difference .DELTA..sub.2 (<.DELTA..sub.1) and is connected to a terminal of the first fiber which has a specific refractive index difference nearly equal to .DELTA..sub.1. A diffusion region in the neighborhood of the connection is formed by diffusing a dopant for refractive index control in the core of the second fiber by heat addition. Due to the diffusion region, the diameters of the first fiber and the second fiber are adjusted so as to be nearly equal. |
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DETAILED DESCRIPTION The present invention has been achieved in consideration of the above-described problems and aims at offering an optical device with a pig tail optical fiber having a low connection loss, a low reflection and low cross talk characteristics.
Further, it is an object of the invention to realize a super-small-size optical device having a lower cost, by connecting an optical waveguide having a high specific refractive index difference and an optical fiber of a low specific refractive index difference via an optical fiber for mode adjustment, which frees the optical waveguide from the burden of mode adjustment and solves the above-mentioned problems of the prior art.
Further, another object of the invention is to offer a production method for easily adjusting the optical mode at the connection parts of optical fibers and to cheaply produce the above-mentioned optical device with a pig tail optical fiber.
The first feature of the present invention is that, in an optical device with a pig tail optical fiber connected to a terminal of an optical waveguide, wherein a core with a high specific refractive index having a rectangular section shape is built in a cladding layer with a low refractive index formed on a substrate, a terminal of a first optical fiber having a specific refractive index difference nearly equal to that of the optical waveguide is connected to a terminal of the optical waveguide, a second optical fiber with a lower specific refractive index difference than that of the optical waveguide is connected to the other terminal of the first optical fiber, and the first optical fiber has nearly the same mode field diameter as that of the second optical fiber in a connection part of the first optical fiber and the second optical fiber.
The second feature of the present invention is that the optical waveguide having the first feature of the present invention has at least one terminal at each of an input terminal and an output terminal in terminal parts of the optical waveguide, and optical fibers comprising the first optical fiber serially connected to the second optical fiber are connected to each terminal of the input terminal and the output terminal
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