JP2000321468A - Light power detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light power detecting device which can securely detect the projection light from an optical waveguide even if there is an obstacle, etc., such as a protruding substrate below the light projection port of the optical waveguide or if it is difficult to install a thick optical fiber since structures are densely installed nearby the optical waveguide. SOLUTION: A PD element 2 detects light propagating in the waveguide and on the photodetection surface of the PD element 2, a short optical fiber 1 whose crosssectional area is smaller than the photodetection surface is arranged, and the light entered into the core of the optical fiber 1 propagates in the core part and the light entered into the clad of the optical fiber 1 is also made incident on the PD element 2 without being attenuated during propagation so that the light is detected by the PD element 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical power detection device, and more particularly to an optical power detection device suitable for use in an optical propagation device in which structures are densely arranged near an optical waveguide.

[0002]

2. Description of the Related Art Conventionally, as a method of detecting light propagating in an optical waveguide, a light receiving element such as a PD (Photo Diode) is arranged close to an end face of the waveguide, and light emitted from the optical waveguide is detected. Measure the intensity of the detection light with an optical power meter by directly entering the light-receiving surface of the light-receiving element, or place the end face of an optical fiber with a large core cross section such as a multimode fiber close to the optical waveguide, A method has been used in which light emitted from a wave path is guided to an optical fiber, and the propagating light is made incident on a light receiving surface of a light receiving element, and the intensity of detected light is measured by an optical power meter.

[0003]

However, there is a problem that these methods can be used only when the emitted light is emitted from the flat end face of the optical waveguide. In other words, when there is no obstacle near the optical waveguide and there is room for space, the light receiving element is installed close to the optical waveguide, or an optical fiber with a large cross-sectional area is installed to guide the detection light to the core. For example, the core of the optical fiber cannot be aligned with the light exit port of the waveguide because the substrate protrudes from the lower surface of the end face of the waveguide from which light is emitted. If the surface is not aligned with the exit of the waveguide, light detection becomes impossible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a main object in a case where there is an obstacle such as a substrate protruding below a light exit port of an optical waveguide.
It is an object of the present invention to provide an optical power detection device capable of reliably detecting light emitted from an optical waveguide even when it is difficult to install a thick optical fiber due to dense structures near the optical waveguide.

[0005]

In order to achieve the above object, according to a first aspect of the present invention, there is provided an optical power detection apparatus provided with a photodetector for detecting light propagating through a waveguide. An optical fiber having a smaller cross-sectional area than the light-receiving surface and a predetermined length is disposed on a light-receiving surface of the detection element, and light incident on any part of the core and the clad of the optical fiber is also subjected to the light detection. It is detected by the element.

In the present invention, the length of the optical fiber can be detected by the photodetector even when the light incident on the clad of the optical fiber is attenuated while propagating in the clad. Is preferably set.

[0007] In the present invention, it is preferable that the length of the optical fiber is set to approximately 3 mm.

According to a second aspect of the present invention, in a second aspect, in a light power detecting device provided with a light detecting element for detecting light propagating in a waveguide, a light receiving surface of the light detecting element has a sectional area larger than the light receiving surface. And a rod-shaped member made of a material that transmits detection light is provided, and the rod-shaped member is preferably formed of glass or plastic.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In one preferred embodiment of the optical power detecting apparatus according to the present invention, a PD element (2 in FIG. 1) for detecting light propagating in a waveguide and a light receiving surface of the PD element are provided. A short optical fiber (1 in FIG. 1) having a smaller cross-sectional area than the light-receiving surface is provided, and light incident on the core (6 in FIG. 2) of the optical fiber propagates through the core portion. The light incident on the fiber cladding (5 in FIG. 2) is also detected by being incident on the PD element without being attenuated too much during propagation.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; FIG. FIG. 1 is a perspective view schematically illustrating a structure of an optical power detection device according to an embodiment of the present invention, and FIG. 2 schematically illustrates a state in which light incident on an optical fiber propagates in the optical fiber. It is sectional drawing.

First, with reference to FIG. 1, the structure of the optical power detection device of the present embodiment will be described. The optical power detection device according to the present embodiment includes an optical fiber 1, a PD element 2, and a chip carrier 4 holding the PD element 2 as main components. In this embodiment, a single mode optical fiber is used as the optical fiber 1, the jacket of the single mode optical fiber is removed to expose the glass, and the end face is cleaved or cut to a length of about 3 mm with a dicing saw. Is used. The optical fiber 1 is set upright so that the center of the light receiving surface 3 of the PD element coincides with the axial center of the optical fiber 1, and is bonded using an adhesive. As the adhesive, an adhesive whose refractive index is almost the same as that of the optical fiber 1 is used.

The outer diameter of the light receiving surface 3 of the PD element 2 is set to about 2
The optical fiber 1 has an outer diameter of 125 μm. This embodiment is characterized in that not only the core 6 but also the light incident on the clad 5 is detected, so that the cross section of the optical fiber 1 does not need to be large, and the structure of the light propagation device in which the optical power detection device is installed. , The size can be determined according to the light detection ability and the like.

With such dimensions, the end face of the optical fiber 1 can be completely accommodated in the light receiving surface 3 of the PD element. Further, the length of the optical fiber 1 is shortened in consideration of the fact that the light incident on the clad 5 is attenuated. Therefore, the length is determined by the intensity of the incident light and the sensitivity of the light receiving element. The length can be set to an optimum length as appropriate.

Next, the operation of the optical power detection device according to the present embodiment will be described with reference to FIG. The optical fiber 1 is
It is formed by a core 6 having a high refractive index and a clad 5 having a low refractive index. By providing such a difference in the refractive index, the light incident on the core 6 propagates through the optical fiber 1 with almost no attenuation. In an ordinary optical power detection device, since only the detection light incident on the core 6 is used, the cross-sectional area of the core 6 of the optical fiber 1 to be used must be large, and therefore the optical fiber 1 itself is also thin. Things can not be used.

However, in the optical power detection apparatus of the present embodiment, not only the core 6 but also the light incident on the clad 5 is used for light detection. That is, since the refractive index of air is about 1, and the refractive index of glass or plastic is larger than 1, the cladding 5
Also propagates while totally reflecting the boundary between the cladding 5 and the air. All the light propagating through this clad 5 is also P
The light enters the light receiving surface 3 of the D element.

As described above, the optical power detection apparatus of the present embodiment uses not only the core 6 but also the clad 5 of the optical fiber 1, so that the optical fiber 1 having a small sectional area can be used. Since the area of the light receiving surface 3 of the PD element is larger than the cross-sectional area of the optical fiber 1, of the light incident on one end of the optical fiber 1, the light incident on the core 6 The light propagating while totally reflecting at the boundary, and entering the clad 5 can also be propagated while totally reflecting at the boundary between the clad 5 and the air, and both can be incident on the light receiving surface of the PD element.

Therefore, even when the substrate protrudes below the light emission port of the optical waveguide or there is an obstacle near the light emission port of the optical waveguide, the optical fiber 1 having a small cross-sectional area is installed near the optical waveguide. The light emitted from the optical waveguide can be reliably guided to the PD element. And P
The optical power can be determined by measuring the photocurrent of the light received by the D element 2.

In the present invention, the type of the optical fiber 1 is not particularly limited. For example, a multi-mode optical fiber can be used, and the material of the optical fiber 1 is not limited to glass. It is also possible to use plastic and the like. Further, the light receiving surface 3 other than the portion where the optical fiber 1 and the PD element 2 are bonded is made to prevent the adhesive from adhering, or even if bonded, the refractive index is smaller than the refractive index of the optical fiber 1. It is preferable to use a member or an adhesive.

Further, in the above embodiment, an example in which the optical fiber 1 is used as a means for introducing light has been described. However, the present invention is not limited to the above embodiment, and the present invention is not limited to the wavelength of light to be detected. Any material may be used as long as it is made of a transparent material and has a small thickness that can be installed near the optical waveguide. For example, a column made of glass or the like can be used instead of the optical fiber 1. The cross-sectional shape of the columnar object is not limited to a circle, but may be a polygon.

[0020]

As described above, according to the optical power detection device of the present invention, when there is an obstacle near the optical waveguide,
Even when the structure is dense and it is not possible to install an optical fiber with a large cross section, light can be detected, and the tolerance for displacement between the optical fiber and the light receiving element can be increased. There is.

The reason is that an optical fiber whose cross-sectional area is smaller than that of the light receiving surface is bonded to the light receiving surface of the PD element of the optical power detection device of the present invention, and the light incident on either the core or the clad of the optical fiber. This is because light can be surely incident on the PD element, and a thin optical fiber can be used.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing the structure of an optical power detection device according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically illustrating a state in which light incident on an optical fiber is incident on a PD element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber 2 PD element 3 PD element light receiving surface 4 Chip carrier 5 Optical fiber clad 6 Optical fiber core 7 Incident light 8 Propagation light

Claims (5)

[Claims] 1. An optical power detection device comprising a photodetector for detecting light propagating through a waveguide, wherein a light-receiving surface of the photodetector has a smaller cross-sectional area than the light-receiving surface and a predetermined length. An optical power detection device, wherein an optical fiber is disposed, and light incident on both the core and the clad of the optical fiber is detected by the photodetector. 2. The length of the optical fiber is set so that even if the light incident on the clad portion of the optical fiber is attenuated while propagating in the clad portion, the light can be detected by the photodetector. The optical power detection device according to claim 1, wherein: 3. The optical power detecting device according to claim 1, wherein the length of said optical fiber is set to approximately 3 mm. 4. An optical power detection device comprising a photodetector for detecting light propagating through a waveguide, wherein a light-receiving surface of the photodetector has a smaller cross-sectional area than the light-receiving surface, and detects light. An optical power detection device, wherein a rod-shaped member made of a transparent material is provided. 5. The optical power detection device according to claim 4, wherein said rod-shaped member is formed of one of glass and plastic.