OPTICAL POWER MONITOR

Abstract

An optical power monitor having a reduced number of component parts, easy to assemble, capable of facilitating positioning for achieving improved optical coupling, and having a reduced size and a reduced manufacturing cost. A pigtail fiber in which the center axis of an optical fiber is shifted from the center axis of the columnar capillary by 0.020 to 0.150 mm is used. The pigtail fiber and a photo diode are provided in a cylindrical tube with the pigtail fiber center axis and the photo diode center axis aligned with each other. The pigtail fiber and the photo diode can be adjusted to the optimum position in the cylindrical tube by adjustment in the longitudinal direction, thus advantageously simplifying the adjustment process in comparison with that in the conventional optical power monitor in which adjustments by movement in the radial direction, movement in the longitudinal direction and rotation about the center axis are made.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an optical power monitor according to the first embodiment of the present invention;

FIG. 2 is a perspective view of a pigtail fiber used in the optical power monitor of the present invention;

FIGS. 3A to 3C are diagrams for explaining the process of assembling the optical power monitor of the present invention;

FIG. 4 is a sectional view of another optical power monitor of the present invention;

FIGS. 5A to 5C are sectional views of conventional optical power monitors;

FIG. 6 is a sectional view of a conventional pigtail-type optical module; and

FIG. 7 is a sectional view of a conventional bidirectional optical power monitor.

Claims

1. An optical power monitor comprising: a pig tail fiber composed ofa columnar capillary having a light emission side end surface at a certain angle to a center axis of the capillary at an end of the capillary; andan optical fiber inserted and fixed in a through-hole, which is parallel to the center axis and extends from the other end of the capillary to the light emission side end surface, andhaving an open end surface forming a plane with the light emission side end surface on the light emission side end surface; anda photo diode with a lens which lens is disposed coaxially with the capillary and with a space of a predetermined length between a tip of the lens and the optical fiber open end surface,wherein the optical fiber open end surface is shifted from the center axis in the direction that a distance from the optical fiber open end surface to the lens tip is becoming more than a distance from a center of the light emission side end surface to the lens tip on a line of a plane, which plane has a line perpendicular to the light emission side end surface and the center axis on the plane, crossing the light emission side end surface, so that an optical signal emitted from the optical fiber open end surface into the space between the optical fiber open end surface and the lens tip irradiates the lens tip.

2. An optical power monitor as set forth in claim 1, wherein the line perpendicular to the light emission side end surface of the capillary is at an angle of about 4° to 10° to the center axis.

3. An optical power monitor as set forth in claim 2, wherein the optical fiber open end surface is shifted by 0.020 mm to 0.150 mm from the center axis in the direction that a distance from the optical fiber open end surface to the lens tip is becoming more than a distance from a center of the light emission side end surface to the lens tip on the line of the plane, which plane has the line perpendicular to the light emission side end surface and the center axis on the plane, crossing the light emission side end surface.