JPH04355415A - Line monitor - Google Patents

Abstract

PURPOSE:To provide a small size/easy-to-assemble/inexpensive line monitor. CONSTITUTION:The edge surfaces of optical fibers 1 and 2 are butted directly against each other so as to be housed in a glass pipe 5. The butt surfaces are formed to be at an angle of 45, and a semi-transparent film 3 is deposited thereon. A part of light 23 being transmitted in the optical fiber 1 is reflected by means of the semi-transparent film 3, and the reflected light 24 is monitored by means of a photodiode 6.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line monitor that extracts and monitors a transmission signal in an optical communication transmission line as a branch signal.

0002

2. Description of the Related Art In optical communication systems, it is common practice to branch out a part of a transmission signal and monitor the branched signal for the purpose of investigating the cause of a failure or the like. The optical component that performs this function is called a line monitor. A conventional line monitor 18 will be explained based on FIG. 2. In the figure, optical fibers 11 and 12 having lenses 13 and 14 at their tips are attached to a case 17 via pipes 15 and 16 on the same straight line so that the lenses 13 and 14 face each other. There are two optical fibers 11 and 12 between them.
A semi-transparent film 3 is arranged at an inclination angle of 45 degrees with the optical axis. Further, a photodiode (PD) 6 is attached to the case 17 so that reflected light 26 of the light 25 from the optical fiber 11 reflected by the semi-transparent film 3 can be monitored. Reference numerals 71 and 72 are electrode terminals for extracting detection signals from the PD.

FIG. 3 shows another conventional line monitor 22. As shown in FIG. In this line monitor 22, a fusion type optical fiber coupler 19 is used for branching the optical signal, and the optical fiber on the branch side of the fusion type optical fiber coupler 19 is connected to the PD module via the fusion splicing part 21. 20 are fusion spliced.

0004

[Problem to be Solved by the Invention] However, in the former case, the light from the optical fiber is converted into parallel light through the lens, which requires a distance longer than the focal length of the lens in the direction of the optical axis, which makes it difficult to reduce the size of the optical fiber. In addition, there is a problem that the optical axis of the lens and the optical fiber must be adjusted, and assembly takes time. In the latter case, it is composed of two optical components: a fused fiber coupler and a PD module. Therefore, when mounting this line monitor, there is a problem in that it is necessary to create a device having a structure for mounting (fixing to the device) two components: the fused optical fiber coupler and the PD module. The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a line monitor that is small, easy to assemble, and inexpensive.

[0005]

[Means for Solving the Problems] In order to achieve this object, the present invention provides a line monitor that monitors branched light from adjacent parts of two adjacent optical fibers, the line monitor comprising: The end faces of the two optical fibers are butted together in a glass pipe having a slightly larger inner diameter, and the butted end faces of the two optical fibers are formed obliquely. A semi-transparent membrane is provided on the butted end faces.

[0006]

[Operation] In the present invention, the end faces of two optical fibers are directly abutted against each other, and almost no space in the optical axis direction is required for line monitoring. Furthermore, the two optical fibers are housed within a glass pipe, eliminating the need for adjustment in the optical axis direction.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view of the present invention. In the line monitor 10 shown in the figure, the two optical fibers 1 and 2 have their tips inclined at an angle of 45 degrees, and are butt-connected inside a glass pipe 5. Here, the optical fibers 1 and 2 have a core diameter of 50 μm and a cladding diameter of 125 μm. A dielectric semi-transparent film 3 is deposited 4 on the end face of the optical fiber 1 in advance. The semi-transparent film 3 is selected to have a transmittance of 90% and a reflectance of 10% when light of 0.85 μm is incident at an angle of 45 degrees. The glass pipe 5 is made of hard glass and has an inner diameter of 130 μm, an outer diameter of 1 mm, and a total length of 8 mm. two optical fibers 1,
The glass pipe 5 housing the glass pipe 2 is housed and fixed in a metal pipe 8 with a slit for reinforcement, and is further fixed to a case 9. Light 23 transmitted through optical fiber 1
A silicon photodiode (Si-PD) 6 was attached at a position where reflected light 24 from the semi-transparent film 3 was monitored.

In the conventional example shown in FIG. 2, since it is necessary to place a lens at the tip of the optical fiber, the size of the case becomes larger than twice the length of the lens and the focal length of the lens.
It is extremely difficult to reduce the total length to 25 mm or less. On the other hand, in this embodiment described above, the total length of the case is 1
It can be kept within 0 mm, making it possible to achieve miniaturization. Furthermore, since the present invention does not require optical axis adjustment during the manufacturing process, compared to the conventional example shown in FIG.
It can be assembled in less than 1/2 the time. In this example, the reflected light from the semi-transparent film was monitored, but instead of using a semi-transparent film, a gap was created between the two optical fibers and the Fresnel reflected light was monitored. is also possible. Further, in this embodiment, the monitoring PD is placed away from the optical fiber, but it goes without saying that it may be placed on the side or inside the glass pipe. Further, in this embodiment, the semi-transparent film is vapor-deposited on one of the fibers and sandwiched therebetween, but the assembly can also be performed by simply sandwiching the semi-transparent film between two fibers without requiring vapor deposition.

[0009]

[Effects of the Invention] As explained above, according to the present invention,
Two optical fibers with oblique tips are connected in a glass pipe with a semi-transparent film in between, and the branched light reflected by the semi-transparent film is monitored, so the light can be easily removed during assembly. This has the advantage of eliminating the need for axis adjustment and realizing a compact line monitor.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of the present invention.

FIG. 2 is a side sectional view of a conventional device.

FIG. 3 is another conventional schematic diagram.

[Explanation of symbols]

1 Optical fiber 2 Optical fiber 3 Semi-transparent membrane 5 Glass pipe 6 Photodiode

Claims (2)

[Claims] 1. In a line monitor that monitors branched light from adjacent parts of two adjacent optical fibers, the two optical fibers are connected in a glass pipe having an inner diameter slightly larger than the outer diameter of the optical fibers. A line monitor characterized in that the end faces of the two optical fibers are butted together, and the butted end faces of the two optical fibers are formed obliquely. 2. The line monitor according to claim 1, further comprising a semi-transparent film provided on the abutting end surfaces of the two optical fibers.