1. Field of the Invention
The present invention relates to an optical module that has a core fabricated using a light curable resin solution and light, and to a method of and an apparatus for manufacturing the optical module. The invention is applicable to an inexpensive and low-loss optical module for use in optical fiber communications, such as an optical transmitter and receiver, an optical interconnection device, and an optical branching filter or coupler.
2. Description of the Related Art
The inventors, together with their coinventors, have developed and applied for patent on an optical waveguide having a so-called self-forming type core. The self-forming type core forms the optical waveguide in the following manner. That is, for example, a liquid light curable resin uncured is irradiated with curing wavelength light in a beam form from an optical fiber. Thereby, only the resin in an optical path portion irradiated in the beam form is cured to form a shaftlike cured material (core). Thereafter, the core is surrounded by a lower refractive index resin for example, thus forming the optical waveguide (see JP-A-2002-365459). Besides, the following is shown by using two light curable resins different in refractive index and curing wavelength. That is, when only the resin on the high refractive index side is cured for a long time (see JP-A-2002-169038) and when only the resin on the low refractive index side is cured for a short time (see JP-A-2004-149579), the remaining resin solution uncured is thereafter cured, thereby making it possible to form two kinds of optical waveguides each having a specific refractive index distribution.
The technology related to the invention will be described using FIGS. 4A to 4E. FIGS. 4A to 4E are process diagrams showing a method of manufacturing an optical module having one light receiving device and one light emitting device.
As shown in FIG. 4A, an open-topped casing 91 made of transparent resin is prepared, and a core end face 921 of an optical fiber 92 is introduced into the inside of the casing 91 and then fixed by a fixing member 93. Next, a half mirror or dichroic mirror (wavelength selective mirror) 94 is fixed to the casing 91. The half mirror or dichroic mirror (wavelength selective mirror) 94 is fixed inclined at 45 degrees to the bottom surface of the casing 91. Thereafter, to form a core member, the inside of the casing 91 is filled with a high refractive index light curable resin solution 95 uncured.
Next, when the light curable resin solution 95 having filled the casing 91 from the end face 921 is irradiated with the curing wavelength light by the optical fiber 92, then a cured material 95c is formed as being shaftlike along the optical path of the light (FIG. 4B). Since the half mirror or dichroic mirror (wavelength selective mirror) 94 is used this time, the cured material 95c will have branches. Thereafter, the light curable resin solution 95 uncured is removed (FIG. 4C). Next, the inside of the casing 91 is filled with a low refractive index curable resin solution 96 uncured that is to provide a cladding. Light curing, heat curing, or any other method may be adopted to cure the curable resin solution 96. Thus, the curable resin solution 96 having filled the inside of the casing 91 is all cured into a cured material 96c, thereby forming optical waveguides, one of which has the high refractive index cured material 95c serving as the core and the other of which has the low refractive index cured material 96c serving as the cladding (FIG. 4D).
Thereafter, for example, a light emitting device 97 and a light receiving device 98 are attached to the vicinities of the junctions between the cured materials 95c serving as the cores and the casing 91 made of transparent resin. Thus, an optical module 900 capable of single-line two-way communication can be completed (FIG. 4E).
In the optical module 900 of FIG. 4E, the light emitting device 97 and the light receiving device 98 face the cured materials 95c serving as the cores via the casing 91 made of transparent resin. With such a structure, it turns out, the following problem arises when a life and a deterioration in characteristics as a module are evaluated based on a so-called acceleration test. That is, in the state where the load of normal humidity at 85° C. or 95% relative humidity at 75° C. is applied, it turns out, the bonding between the cured material 95c serving as the core and the optical device 97, 98 is deteriorated in several hours, so that a light transmission loss is lost on the order of 40%. This is caused mainly by separation of the cured resin from the casing.