Optical waveguide modulator equipped with an output light monitor

An optical waveguide modulator equipped with an output light monitor comprising:

• an optical waveguide element comprising a dielectric substrate and an optical waveguide formed on a front surface of the dielectric substrate, the optical waveguide comprising a plurality of surface optical waveguide portions, an optical waveguide connecting portion on which the surface optical waveguide portions are converged and connected to each other and an output light-outputting optical waveguide portion connected to the optical waveguide-connecting portion;
• an optical fiber for output light, connected to an output end of the output light-outputting optical waveguide portion of the optical waveguide element;
• a reinforcing capillary for reinforcing a connection between the optical waveguide element and the output light-outputting optical fiber;
• and
• a means for receiving monitoring light, wherein
• (1) the reinforcing capillary is provided with a hole formed therein for containing and holding the optical fiber for output light, a connection surface thereof connected to an output end side surface of the dielectric substrate of the optical waveguide element, and a terminal surface thereof opposite to the connection surface;
• (2) the reinforcing capillary is formed from a light-transmittable glass, to thereby enable radiation mode light generated in the optical waveguide connecting portion of the optical waveguide element to pass through the dielectric substrate and to be received by the light-transmittable reinforcing capillary, and the radiation mode light outputted from the terminal surface of the reinforcing capillary to be received, as monitoring light, by the monitoring light-receiving means;
• (3) the monitoring light-receiving means is located in a position in which the monitoring light outputted from the reinforcing capillary to the outside of the capillary can be received, and is provided with a photoelectric conversion element;
• (4) the terminal surface of the reinforcing capillary formed from the light-transmittable glass is provided with a surface portion, in which the monitoring light is reflected, and a non-monitoring surface portion, whereby when the radiation mode light radiated from the optical waveguide connection portion of the optical waveguide element through both side portions of the output light-outputting optical waveguide portion passes through the dielectric substrate of the optical waveguide element and the reinforcing capillary connected to the output end surface of the dielectric substrate, only a portion of the radiation mode light radiated to one side portion of the output light-outputting optical waveguide portion is reflected on the monitoring light-reflecting surface portion of the reinforcing capillary toward the monitoring light-receiving means and received as a monitoring output light by the monitoring light-receiving means, and another portion of the radiation mode light which reaches the non-monitoring surface portion is not received, as a monitoring light, by the monitoring light-receiving means;
• and
• (5) the terminal reflecting surface portion of the reinforcing capillary intersects the direction of the longitudinal axis of the hole in which the output light-outputting optical fiber is received, at an oblique angle, to thereby enable the radiation mode light reflected on the terminal reflecting surface portion to be received, as monitoring light, by the monitoring light-receiving means.