JPH1152171A - Optical star coupler and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the fluctuation of losses of optical signals. SOLUTION: 16 lines of plastic fibers 101-116 are bundled correctively to be held in between two L-shaped deformation forcing jigs 121, 122 in a bundle part 120. Then, the end face of the bundle part 120 is welded to the incidence- emission end of a square pole-shaped plastic mixing rod 130 to be fixed. The internal part of the plastic mixing rod 130 is made of plastic whose refractive index is sufficiently higher than that of air and the mixing rod is made to be an optical waveguide which makes external air an air clad 140. A hologram diffusing unit 150 is vapor-deposited on the refraction end of the plastic mixing lode 130 to be fixed. The hologram diffusing unit 150 is a unit refracting optical signals 160 reaching the end part after propagating in the inside of the rod 130 while diffusing them and a projected-recessed hologram is formed by applying a press work on a reflection mirror formed by a vapor deposition from an upward direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical star coupler for splitting an optical signal from one optical fiber and distributing the optical signal evenly to a plurality of other optical fibers, and a method of manufacturing the optical star coupler. Further, the present invention relates to an optical star coupler using a prismatic rod as a mixing portion and a method for manufacturing such an optical star coupler.

[0002]

2. Description of the Related Art Generally, in order to construct an information communication network using an optical fiber or the like, one optical signal is split into a plurality of optical fibers, or an optical signal from a multi-layered optical fiber is combined into one optical fiber. An optical star coupler for collecting is required. This optical star coupler is provided with a mixing section.
An optical signal incident on one optical fiber is diffused at the time of incidence with a predetermined divergence angle of the optical fiber, and propagates by repeating total reflection in the mixing section. As a result, n output optical signals are emitted from the plurality of optical fibers on the output side. At this time, basically, the longer the mixing part,
The input optical signal can be made uniform. There are various forms of the mixing section, and one of them is a cylinder or a prismatic rod-shaped member (mixing rod) as the mixing section. An example of such an optical star coupler is disclosed in JP-A-9-184941.

FIG. 4 is a diagram showing an example of a conventional optical star coupler. In the bundle section 220 of the optical star coupler, 16 optical fibers 201 to 216 are bundled together and fixed inside a square tubular member with an adhesive. Then, the end face of the bundle portion 220 is bonded and fixed to the input / output end of the mixing rod 230 having a quadrangular prism shape with an adhesive 261.

The inside of the mixing rod 230 is made of glass whose refractive index is sufficiently higher than that of air.
At the input / output end of the mixing rod 230, a metal evaporation mirror 231 is provided. This vapor deposition mirror 231
Is for reflecting light propagating in the mixing rod 230, and is provided except for portions that match the cores of the optical fibers 201 to 216.

On the other end (reflection end) of the mixing rod 230, a hologram diffuser 250 is
It is bonded and fixed at 62. The hologram diffuser 250 is composed of minute irregularities (in the case of a volume hologram, a periodic change in the refractive index) for diffusing the incident optical signal larger than the spread angle, and a reflection mirror,
The light propagating in the mixing rod 230 is further diffused and reflected in the incident direction.

In the optical star coupler having such a configuration, for example, the optical fiber 201 is connected to the mixing rod 23.
When the optical signal 270 is incident on the mixing rod 230, the optical signal 270 spreads in the mixing rod 230, propagates while being totally reflected on the side surface of the mixing rod 230, and reaches the hologram diffuser 250. Then, the hologram diffuser 250
And diffusely propagated in the opposite direction. A part of the reflected light is reflected by the vapor deposition mirror 231, but other optical signals enter the cores of the optical fibers 201 to 216. The optical signal 270 reflected by the vapor deposition mirror 231 repeats reciprocation in the mixing rod 230 and finally the optical fiber 2
The light enters the cores 01 to 216.

[0007] In this manner, an optical signal propagating through one optical fiber can be equally branched into a plurality of optical fibers.

[0008]

However, in the conventional optical star coupler, the bundle section 220 and the mixing rod 23 are not provided.
0 and adhesives 261 and 26 at the joint between mixing rod 230 and hologram diffuser 250.
Because the application area of 2 is small, it is affected by vibration, heat, etc.
There has been a problem that the loss of the optical signal 270 to be branched fluctuates and reliability is lacking. That is, the adhesive 2
Since 61 and 262 are not applied directly to the joining surface but are applied around the joining portion, they cannot be adhered very strongly, and as a result, are susceptible to vibration and heat. I have.

The present invention has been made in view of the above points, and has as its object to provide a highly reliable optical star coupler with little variation in optical signal loss. It is another object of the present invention to provide a method for manufacturing an optical star coupler having a small variation in loss of an optical signal and high reliability.

[0010]

According to the present invention, there is provided an optical star coupler for splitting one optical signal into a plurality of optical signals, wherein a plurality of optical fibers made of plastic are bundled. Portion, an optical waveguide is formed from the input / output end to the reflection end, and the optical waveguide at the input / output end is fused to the bundle portion so as to cover the core at the end of the plurality of optical fibers. And a light diffuse reflection portion that is deposited on the reflection end of the mixing portion and diffuses and reflects light that has reached the reflection end of the mixing portion. Is done.

According to this optical star coupler, the bundle portion and the mixing portion are joined by fusion, and the mixing portion and the light diffusion / reflection portion are joined by vapor deposition. An optical signal incident from any one of the optical fibers is branched into a plurality of optical fibers without being affected by vibration or thermal stress.

Further, according to the method of manufacturing an optical star coupler of the present invention, in the method of manufacturing an optical star coupler for branching one optical signal into a plurality of optical signals, a plastic mixing in which an optical waveguide is formed from an input / output end to a reflection end. A reflection mirror is formed by vapor deposition on the reflection end of the portion, and a concave / convex hologram is formed by performing press working from above the reflection mirror, and the optical waveguide at the input / output end of the mixing rod is a bundle portion. And fusing the mixing rod and the bundle so as to cover the cores at the ends of the plurality of optical fibers made of plastic bundled by the method. .

When an optical star coupler is manufactured by this manufacturing method, the bundle portion and the mixing portion are firmly joined by fusion, and the mixing portion and the light diffusion / reflection portion are firmly joined by vapor deposition.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an optical star coupler of the present invention. In this optical star coupler, 16 plastic fibers 101 to 116 are bundled together and sandwiched between two L-shaped deformation forcing jigs 121 and 122 in a bundle portion 120. The ends of the plastic fibers 101 to 116 are heated and compressed by deformation forcing jigs 121 and 122 when forming the bundle portion 120, and have a square cross section. As a result, most of the end face of the bundle portion 120 is occupied by the cores of the plastic fibers 101 to 116. Then, it is fused and fixed to the input / output end of the square-column plastic mixing rod 130 so that the core area on the end face of the bundle part 120 formed in a plane is covered.

The inside of the plastic mixing rod 130 is made of plastic whose refractive index is sufficiently higher than that of air.

Further, the plastic mixing rod 13
A hologram diffuser 150 is vapor-deposited on the 0 reflection end,
Fixed. The hologram diffuser 150 diffuses and reflects the optical signal 160 that has propagated through the plastic mixing rod 130 and reached the end, as in the related art, and presses the reflective mirror formed by evaporation from above. Thus, a concavo-convex hologram is formed.

Next, a method for manufacturing the optical star coupler of the present invention will be described. The manufacturing process of the star coupler of the present invention is roughly divided into a process of forming the bundle portion 120 and a process of forming the hologram diffuser 15 on the plastic mixing rod 130.
0 and a fusion step thereof. The details are as follows.

FIG. 2 is a view showing a process of forming the bundle portion 120. This figure is an enlarged view of an end of the bundle unit 120. [S1] Sixteen plastic fibers 101 to 116 having a circular cross section are bundled and stored in two L-shaped deformation forcing jigs 121 and 122. [S2] The deformation forcing jigs 121 and 122 are heated to a temperature at which the plastic fibers 101 to 116 are deformed and melted. The approximate heating temperature is, for example, about 80 to 100 at the glass transition temperature from the deformation temperature in the case of an acrylic fiber.
° C, about 120-15 for PC (polycarbonate)
0 ° C.

After being heated to a predetermined temperature, pressure is applied obliquely from one deformation forcing jig 121. Thereby, the cross section of the plastic fibers 101 to 116 becomes rectangular, and the cross section of the bundle section 120 becomes equal to the cross section of the plastic mixing rod 130.

At the time of pressurization, in order to prevent excessive deformation, the L-shaped deformation forcing jig 121 on the pressing side comes into contact with the other deformation forcing jig 122 to apply pressure to the fiber. The dimensions of the deformation forcing jigs 121 and 122 are set so as to stop.

As a result, the dead area (the area other than the cores of the plastic fibers 101 to 116) at the joint between the bundle section 120 and the plastic mixing rod 130 is reduced, and the loss is reduced. That is, when the dead area is wide, it is necessary to provide a reflection mirror in the area and re-circulate the light applied to the area in the mixing rod. However, each time the mixing rod is reciprocated, an optical signal is lost. Therefore, a small dead area leads to a reduction in loss of an optical signal, and can increase a transmission distance.

FIG. 3 is a view showing a process of forming a hologram diffuser. [S11] A metal (eg, gold, aluminum, copper, or the like) or a dielectric is deposited on the end surface of the plastic mixing rod 130 to form a deposition mirror 151. [S12] The glass is etched by several tens of μm.
The male mold 170 is formed by forming periodic irregularities having a depth of 1 μm or less at the corners. [S13] The male mold 170 is heated to a temperature at which the plastic mixing rod 130 deforms and melts. The approximate heating temperature is, for example, about 80 to 100 ° C. in terms of glass transition temperature to deformation temperature in the case of an acrylic fiber, and about 120 to 150 ° C. in the case of a PC (polycarbonate). [S14] After being heated to a predetermined temperature, the male mold 170 is applied to the vapor deposition mirror 151 on the end face of the mixing rod 130 to transfer predetermined irregularities.

Thus, several tens of μm are formed on the surface of the reflection mirror.
Periodic uneven hologram 152 having an m-square and a depth of 1 μm or less
Is formed. That is, the hologram diffuser 15 in which the uneven hologram 152 is formed on the end face of the vapor deposition mirror 151
0 is formed.

This transfer operation is performed by applying a jig (not shown) for preventing excessive unevenness and deformation. After the steps shown in FIGS. 2 and 3 are completed, each side of the input / output end of the mixing rod 130 is heated by an ultrasonic heater or the like, and the bundle portion and the mixing portion are fused. Thus, an optical star coupler as shown in FIG. 1 is manufactured.

In the optical star coupler having such a configuration, for example, when the optical signal 160 is incident on the plastic mixing rod 130 from the plastic fiber 101, the optical signal 160 spreads in the plastic mixing rod 130 and the plastic mixing rod 1
The light propagates while being totally reflected on the side surface of the hologram diffuser 30 and reaches the hologram diffuser 150. Then, the light is diffusely reflected by the hologram diffuser 150 and propagates in the opposite direction. This reflected light enters the cores of the plastic fibers 101 to 116.

Here, in the optical star coupler of the present invention, the bundle portion 120 and the mixing rod 130 are joined by fusion, and the mixing rod 130 and the hologram diffuser 150 are joined by vapor deposition. As a result, the respective members are firmly joined without the adhesion by the adhesive, are hardly affected by vibration and thermal stress, and have high reliability.

In the above example, since the cross-sectional shape of the plastic fibers 101 to 116 is rectangular, the dead area is eliminated. However, when optical fibers having a circular cross-sectional shape are bundled, the end face of the bundle portion is not changed. Alternatively, it is necessary to form a reflection mirror at the input / output end of the mixing rod. For example, the plastic mixing rod 13
A metal deposition mirror is provided at the input / output end of 0. The vapor deposition mirror reflects light propagating in the plastic mixing rod 130, and is provided except for a portion corresponding to the core of each plastic fiber. Thereby, the optical signal reflected by the vapor deposition mirror repeats reciprocation in the plastic mixing rod 130, and finally enters the plastic fiber core.

[0028]

As described above, in the optical star coupler of the present invention, the bundle portion and the mixing portion are joined by fusion, and the mixing portion and the light diffuse reflection portion are joined by vapor deposition. Are strongly bonded, and an optical signal incident from any of the plurality of optical fibers is branched into a plurality of optical fibers without being affected by vibration or thermal stress. As a result, the loss of the optical signal does not fluctuate, and the reliability is improved.

In the method of manufacturing an optical star coupler according to the present invention, the bundle portion and the mixing portion are firmly joined by fusion, and the mixing portion and the light diffusion reflection portion are firmly joined by vapor deposition. Therefore, a highly reliable optical star coupler is obtained in which an incident optical signal is branched into a plurality of optical fibers without being affected by vibration or thermal stress.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical star coupler of the present invention.

FIG. 2 is a view illustrating a forming process of a bundle portion.

FIG. 3 is a diagram showing a step of forming a hologram diffuser.

FIG. 4 is a diagram illustrating an example of a conventional optical star coupler.

[Explanation of symbols]

 101 to 116 Plastic fiber 120 Bundle part 121, 122 Deformation forcing jig 130 Plastic mixing rod 140 Air clad 150 Hologram diffuser 160 Optical signal

Continuation of front page (72) Inventor Yasuichi Sano 1-1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fuji Electric Co., Ltd.

Claims (6)

[Claims] 1. An optical star coupler for branching one optical signal into a plurality of optical signals, comprising: a bundle section in which a plurality of plastic optical fibers are bundled; and an optical waveguide formed from an input / output end to a reflection end. A mixing section made of plastic, wherein the optical waveguide at the end covers the cores at the ends of the plurality of optical fibers, and the mixing section is made of plastic; and the mixing section is deposited on the reflection end of the mixing section, and A light diffuse reflection portion for diffusing and reflecting light reaching the reflection end of the portion. 2. The light diffusion / reflection unit includes a reflection mirror formed by vapor deposition on the reflection end of the mixing unit and a concave / convex hologram formed on an end surface of the reflection mirror. The optical star coupler according to claim 1. 3. The optical star coupler according to claim 2, wherein said reflection mirror is made of metal. 4. The optical star coupler according to claim 2, wherein said reflection mirror is made of a dielectric. 5. The optical star coupler according to claim 2, wherein the concavo-convex hologram is formed by pressing an end face of the reflection mirror. 6. A method for manufacturing an optical star coupler for branching one optical signal into a plurality of optical signals, wherein a reflection mirror is formed by vapor deposition on the reflection end of a plastic mixing portion having an optical waveguide formed from an input / output end to a reflection end. By performing press working from above the reflection mirror,
Forming a concavo-convex hologram, wherein the optical waveguide at the input / output end of the mixing rod covers cores at ends of a plurality of optical fibers made of plastic bundled in a bundle portion, and the mixing rod and the bundle A method for manufacturing an optical star coupler, comprising: