JPH03250674A - Light emitting device - Google Patents

Abstract

PURPOSE:To monitor intensity of a light signal to be coupled to an optical fiber and intensity of reflected light simultaneously and independently by detecting the intensity of the light signal to be coupled from a light emitting element to the optical fiber by a first light receiving element and detecting the intensity of the reflected light from a transmission path on the side of the optical fiber by a second light receiving element. CONSTITUTION:When there is reflected light which has been generated in the way of a transmission path on the optical fiber 14 side to be incident on a light emitting element 12, this reflected light enters one of light waveguide paths 16 in a light splitter 15 from the optical fiber 14 and a part of the light is coupled to the other light waveguide path 17. The reflected light coupled to the light waveguide path 17 is impinged on a light receiving element 19, from which current proportional to intensity of the reflected light is output. The reflected light is hardly incident on a light receiving element 18 due to a directionality of the light splitter 15. Therefore not only the intensity of a light signal output from the light emitting element 12 but also the intensity of the reflected light from the transmission path on the optical fiber 14 side can be monitored simultaneously. Thus a transmission state can be stabilized by using the information thereby permitting a device failure to be found in an early stage.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a light emitting device used for optical communication, and in particular, it relates to the intensity of an optical signal coupled from a light emitting element to an optical fiber, and the intensity of an optical signal coupled from a transmission line on the optical fiber side. The present invention relates to a light emitting device having a function of simultaneously monitoring reflected light and reflected light.

[Conventional technology]

Conventionally, this type of light emitting device has been configured as shown in FIG. 3, for example. In the figure, 1 is a housing, and a light emitting element 2 is disposed inside this housing 1, and a lens 3 for condensing light is provided in front of this light emitting element 2 (above in the figure).
Further, in front of this lens 3, one end portion of an optical fiber 4, the other end of which is led out, is arranged. The light emitting element 2 and the light receiving element 5 are connected to external equipment in the housing 1 via a wire 6 and a feed through bottle 7, respectively.

In this light-emitting device, an optical signal output from a light-emitting element 2 is focused by a lens 3, then coupled to an optical fiber 4, and transmitted through the optical fiber 4 to a light-receiving device. A part of the optical signal from the light emitting element 2 is also output to the rear of the light emitting element 2 and enters the light receiving element 5. Since the light emitting element 2 and the light receiving element 5 are each connected to the outside of the housing 1 through the feedthrough pin 7, the light emitting element 2 can be connected from the outside.
It is possible to control the current, and also monitor the light emission intensity of the light emitting element 2 through the light receiving element 5.

[Problem to be solved by the invention]

However, the conventional light emitting device described above has the following problems. First, when monitoring the light emission intensity of the light emitting element 2, information on the light intensity actually coupled to the optical fiber 4 cannot be obtained. That is, the amount of output current observed externally from the light receiving element 5 is the emission intensity of the light emitting element 2, and normally an output current proportional to the intensity of the optical signal coupled to the optical fiber 4 is obtained. However, even if the intensity of the optical signal coupled to the optical fiber 4 changes as a result of changes in the coupling efficiency between the light emitting element 2 and the optical fiber 4 due to temperature changes or changes over time, the light emitting element 2 and the light receiving element 5 may If the coupling efficiency between them is constant, information that the intensity of the optical signal coupled to the optical fiber 4 has changed will not appear in the output current of the light receiving element 5. As a result, the conventional light emitting device has a problem in that it is difficult to detect variations in the intensity of the optical signal coupled to the optical fiber 4 due to the light emitting device itself. Further, when a connector or the like is present on the transmission path on the optical fiber 4 side, if the connection is incomplete, reflected light from the connector may increase. The reflected light travels through the optical fiber 4 in the opposite direction and enters the light emitting element 2, making its operation unstable. However, in conventional light emitting devices, it has not been possible to monitor the intensity of reflected light from the transmission path.

The present invention has been made in view of such problems, and its purpose is to simultaneously and independently monitor the intensity of an optical signal coupled to an optical fiber and the intensity of reflected light from a transmission line on the optical fiber side. The object of the present invention is to provide a light-emitting device that is capable of stable light transmission.

[Means to solve the problem]

The light-emitting device of the present invention includes a light-emitting element, an optical fiber that guides an optical signal output from the light-emitting element to the outside, and a pair of optical waveguides whose intermediate portions are optically coupled to each other, one of which is optically coupled to the other optical waveguide. an optical splitter formed by optically coupling an optical fiber and a light emitting element, and a second optical branch for detecting the emission intensity of the light emitting element optically coupled to one end of the other optical waveguide of the optical splitter. A second light emitting element is provided for detecting the intensity of reflected light from the optical fiber side that is optically coupled to the other end of the other optical waveguide. Further, the light emitting device of the present invention further includes a third light receiving element for detecting the emission intensity of the light emitting element near the light emitting element.

With such a configuration, in the light emitting device according to the first aspect, the optical signal output from the light emitting element is coupled to one optical waveguide of the optical splitter. Most of the optical signal coupled to the optical waveguide is transmitted to the outside through the optical fiber, but a portion is coupled to the other optical waveguide and input to the first light receiving element, and the first light receiving element receives this input signal. Outputs current according to the current.

On the other hand, the reflected light that is generated in the middle of the transmission line on the optical fiber side and enters the light emitting element enters one optical waveguide of the optical splitter from the optical fiber/NJ, and a part of it enters the other optical waveguide. After being coupled, the light is incident on the second light receiving element, and the second light receiving element outputs a current proportional to the intensity of the reflected light. Therefore, with this light emitting device, it is possible to monitor the intensity of the optical signal coupled to the optical fiber, and at the same time, to monitor the intensity of the optical signal coupled to the optical fiber.
The intensity of reflected light entering from the side can be monitored. Further, in the light emitting device according to claim 2, since the optical signal output from the light emitting element is also directly inputted to the third light receiving element, fluctuations in the intensity of the light incident on the optical fiber will affect the light emitting element. It becomes possible to determine whether the problem is caused by the problem or the problem is caused by the coupling system such as a lens.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the inside of a light emitting device according to an embodiment of the present invention. In the figure, 11 is a housing, and this housing 11
A light emitting element 12 is disposed inside.

A lens 13 for condensing light is arranged in front of the light emitting element 12, and further in front of this lens 13, a 2-manpower x 2-output type optical splitter 15 is arranged.

The optical splitter 15 has a pair of optical waveguides 16.17, and these optical waveguides 16.17 are optically coupled to each other at the center. An input end of an optical fiber 14 whose output end is led out is arranged in front of the optical splitter 15. Input end of optical fiber 14 and front output end 12a of light emitting element 12
and are optically coupled by one optical waveguide 16 of the optical splitter 15. Light receiving elements 18 and 19 are arranged near both output ends of the other optical waveguide 17, respectively.

One light receiving element 18 is connected to the optical fiber 14 from the light emitting element 12.
It detects the intensity of the optical signal coupled to the The other light receiving element 19 detects the intensity of the reflected light from the transmission line on the optical fiber 14 side. The light-emitting element 12 and the light-receiving element 18 , 19 are each connected to a feed-through pin 20 via a wire 21 , thereby controlling the current from the outside to the light-emitting element 12 .
．． The output current from 19 is detected.

In such a configuration, in the light emitting device of this embodiment, the optical signal output from the front output Fii 12 a of the light emitting element 12 passes through the lens 13 and is coupled to one optical waveguide 16 of the optical splitter 15. Ru. The optical signal coupled to the optical waveguide 16 travels therein, and most of it is transmitted to the outside through the optical fiber 14 connected to the output end of the optical waveguide 16.
A portion is coupled to the optical waveguide 17 side. The optical signal coupled to the optical waveguide 17 enters the light receiving element 18, and the light receiving element 1
8 outputs a current according to this incident light. At this time, due to the directionality of the optical splitter 15, almost no optical signal from the light emitting element 12 enters the light receiving element 19 disposed on the opposite side of the light receiving element 18. Here, the intensity of the optical signal incident on the light-receiving element 18 also follows variations in light intensity due to optical axis misalignment between the light emitting element 12 and the lens 13 and between the lens 13 and the optical splitter 15. Therefore, the intensity of the optical signal coupled to the optical fiber 14 can be accurately monitored by detecting the current output from the light receiving element 18 via the feed-through pin 5 with an external device.

Next, when there is reflected light that is generated in the middle of the transmission path on the optical fiber 14 side and enters toward the light emitting element 12,
This reflected light enters one optical waveguide 16 in the optical splitter 15 from the optical fiber 14, and a part of it enters the other optical waveguide 17.
is combined with The reflected light coupled to the optical waveguide 17 is incident on the light receiving element 19, and a current proportional to the intensity of the reflected light is output from the light receiving element 19. In this case as well, the reflected light hardly enters the light receiving element 18 due to the directionality of the optical splitter 15. Therefore, in the light emitting device of this embodiment, it is possible to simultaneously monitor the intensity of the optical signal output from the light emitting element 12 and the intensity of the reflected light from the transmission line of the optical fiber 1411J. Therefore, by using this information, it is possible to further stabilize the transmission state, and it is also possible to detect abnormalities in the device at an early stage.

FIG. 2 shows another embodiment of the invention.

In this embodiment, a light receiving element 22 is also provided near the rear output end 12b of the light emitting element 12, and this light receiving element 22 is connected to the feedthrough pin 20. Light receiving element 22
The optical signal outputted from the rear output end 12b is also outputted to the light receiving element 22. In other words, light receiving element 2
The value of the current output from the light emitting element 12 is proportional to the light emission intensity of the light emitting element 12 itself. Therefore, by comparing the value of the output current of the light receiving element 18 and the value of the output current of the light receiving element 22,
Optical fiber 14 - It is possible to determine whether the fluctuation in the intensity of the incident optical signal is caused by the light emitting element 12 or the coupling system near the lens 13, making it possible to create a more accurate light emitting device. information can be obtained.

〔Effect of the invention〕

As explained above, according to the invention described in claim 1, an optical splitter having a pair of optical waveguides is disposed between the light emitting element and the optical fiber, and one optical waveguide connects the light emitting element and the optical fiber. along with combining.

A first light receiving element and a second light receiving element are respectively disposed at both output ends of the other optical waveguide, and the first light receiving element detects the intensity of the optical signal coupled from the light emitting element to the optical fiber; Since the second light receiving element detects the intensity of the reflected light from the transmission line on the optical fiber side, it is possible to simultaneously and independently monitor the intensity of the optical signal coupled to the optical fiber and the intensity of the reflected light. Thus, a light emitting device capable of stable optical transmission can be realized.

Further, according to the invention as claimed in claim 2, since the optical signal output from the light emitting element is directly inputted to the third light receiving element, fluctuations in the intensity of the optical signal coupled to the optical fiber are prevented. It becomes possible to determine whether the problem is caused by the light emitting element or the coupling system such as a lens.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the internal structure of a light-emitting device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the internal structure of a light-emitting device according to another embodiment of the present invention, and FIG. 3 is a conventional FIG. 2 is a cross-sectional view showing the internal configuration of the light emitting device. 11... Housing, 13... Lens, 14
......optical fiber, 15...optical splitter,
16.17... Optical waveguide, 18.19.22... Light receiving element.

Claims (1)

[Claims] 1. A light-emitting element, an optical fiber that guides an optical signal output from the light-emitting element to the outside, and a pair of optical waveguides whose intermediate portions are optically coupled to each other, one of which is optically coupled to the other. an optical splitter in which a wave path optically couples the optical fiber and the light emitting element; and a light emitting intensity of the light emitting element optically coupled to one end of the other optical waveguide of the optical splitter. A first light emitting element for detection; and a second light emitting element for detecting the intensity of reflected light from the optical fiber side optically coupled to the other end of the other optical waveguide. A light emitting device characterized by: 2. The light emitting device according to claim 1, further comprising a third light receiving element for detecting the intensity of light emitted from the light emitting element near the light emitting element.