JPH0588048A - Optical fiber fitting device - Google Patents

Abstract

PURPOSE:To enable the adjustment equivalent to the optimum adjustment of the intensity of light emission only by replacing a different-length optical fiber by arranging the tip surface of an optical fiber and the light emission surface of a light emitting element opposite each other across a specific gap. CONSTITUTION:A bare optical fiber 2 after its sheath 3 is removed is inserted into the small-diameter cavity at the tip part of a ferrule 1 and the following sheath 3 of the optical fiber 2 is inserted into the large-diameter cavity part at the rear end part of the ferrule 1 and fixed with an adhesive, etc. Further, the gap G is provided between the tip surface of the optical fiber 2 and the tip surface of the ferrule 1. The tip surface of the ferrule 1 is brought into contact with the light emission surface of a transmission-side light emitting element 4. Consequently, the light signal emitted by the light emitting element 4 reaches the tip surface of the optical fiber 2 through the gap G and is transmitted by the optical fiber 2 and sent to a reception side. Consequently, the optimum adjustment is made without varying the light emission level of the transmission-side light emitting element 4 only by replacing the different-length optical fiber 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber mounting device for coupling a plastic optical fiber to a light emitting element.

[0002]

2. Description of the Related Art Conventionally, an optical cable formed of a plastic optical fiber has a larger signal attenuation per unit length than a single mode optical cable such as a quartz fiber. For example, in a plastic fiber in which polymethylmethacrylate is used for the core and a fluororesin is used for the clad, a loss of 0.2 to 0.3 dB / m is lost for a standard signal light source with an emission wavelength of 660 nm. Therefore, when the long cable is used, the emission intensity of the light emitting element on the transmission side is increased, and when the short cable is used, the emission intensity of the light emitting element on the transmission side is adjusted to be weak. It was necessary to prevent the light receiving element on the receiving side from becoming saturated or causing an insufficient amount of light. In order to actually perform such adjustment, the current supplied to the light emitting element on the transmitting side is limited by a semi-fixed resistance, and the semi-fixed resistance is adjusted while monitoring the optical power meter to adjust the light emission. Strength adjustments are being made. Or as a simpler way,
The resistance optimized in advance according to the length of the cable is switched by a switch, and a current is supplied to the light emitting element through the resistance switched by the switch to adjust the light emission intensity of the light emitting element. It is generally done.

However, the method for adjusting the light emission intensity of the light emitting element as described above is effective for a fixedly provided optical communication path, but the arrangement between the transmitting and receiving devices is uncertain, and is sometimes used. It is not suitable for general use where the length of the optical cable changes, for the following reasons. That is, if an optical cable according to the distance is used, since the same connector is used, a general user mistakenly thinks that the optical cable works simply by exchanging the optical cable. This is because the read-out intensity of the light-emitting element on the side is not readjusted in many cases, which causes a problem such that the signal cannot be normally received.

[0004]

As described above, when the plastic optical cable is used and the length of the signal transmission path is changed by changing the length of the cable from time to time, the light emission of the light emitting element on the transmission side is caused. Although the intensity must be adjusted so that the level of the optical signal transmitted through the optical cable is within the dynamic range of the light receiving element, general users simply use optical cables of different lengths. It may be forgotten to readjust the light emission intensity of the light emitting element on the transmission side simply by exchanging the cable, and this may cause problems such as poor transmission of optical signals.

Therefore, the present invention eliminates the above-mentioned drawbacks, and optimizes the light emission intensity of the light emitting element by simply changing the optical fibers of different lengths without changing the light emitting level of the light emitting element on the transmitting side. It is an object of the present invention to provide an optical fiber mounting device capable of performing equalization adjustment when adjusted.

[0006]

The optical fiber attaching device of the present invention has a structure in which the tip end surface of the optical fiber and the light emitting surface of the light emitting element are arranged to face each other with a predetermined gap therebetween.

[0007]

In the optical fiber attaching apparatus of the present invention, the tip end surface of the optical fiber and the light emitting surface of the light emitting element are arranged to face each other with a predetermined gap. Therefore, the optical signal emitted from the light emitting element is attenuated by the gap, penetrates into the optical fiber from the tip surface of the optical fiber, and is transmitted.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of an optical fiber attaching device of the present invention. 1 is a brass ferrule that holds an optical fiber strand in a connector, 2 is a plastic optical fiber that transmits an optical signal, and 3 is a polyethylene φ
2.20 mm sheet (coating), 4 is a light emitting element that emits an optical signal. The core of the optical fiber 2 is 0.98
mm polymethyl methacrylate, the clad is made of a fluororesin of φ1.00 mm, and the transmission loss is 0.24 dB / m for parallel light with a wavelength of 660 nm. A cable composed of the optical fiber 2 and the sheath 3 covering the optical fiber 2 is called an optical cable.

A bare optical fiber 2 from which a sheath 3 has been removed is inserted into a small-diameter cavity at the tip of a ferrule 1.
A sheath 3 following the optical fiber 2 is inserted into a hollow portion having a large diameter at the rear end portion of the ferrule 1 and fixed with an adhesive or the like. A gap G is provided between the tip surface of the optical fiber 2 and the tip surface of the ferrule 1. The tip surface of the ferrule 1 is brought into close contact with the light emitting surface of the light emitting element 4 on the transmitting side. Therefore, the optical signal emitted from the light emitting element 4 enters the front end surface of the optical fiber 2 through the gap G, is transmitted through the optical fiber 2 and is sent to the receiving side (not shown).

Next, a method of attaching the optical cable of this embodiment to the light emitting element on the transmitting side will be described. First, the sheath 3 covering the optical fiber 2 is peeled off, the bare optical fiber 2 is inserted into the hollow portion of the ferrule 1, and the optical fiber portion protruding from the tip of the ferrule 1 to the outside. After cutting, the tip surface of the optical fiber 2 is polished as it is. At this time, the adhesive is not applied to the optical fiber 2 portion and the sheath 3 portion so that the optical cable is not fixed in the ferrule 1.

After that, when the polishing of the tip surface of the optical fiber 2 is completed, the optical fiber 2 is pulled out from the ferrule 1 together with the sheath 3. Next, the sheath 3 is sliced into a length equal to the gap G shown in FIG. 1 to form the adjustment covering portion 5 (see FIG. 2). The optical fiber 2 whose front end surface has been polished is passed through this covering portion 5 as shown in FIG.
The length of the exposed optical fiber 2 portion of the optical cable is adjusted, and this is inserted into the cavity of the ferrule 1.
At this time, the exposed optical fiber 2 portion and the adjustment coating portion 5
Then, an adhesive is attached to the portion of the sheath 3 to fix the optical cable in the ferrule 1. As a result, the optical cable 1 is positioned inside the ferrule 1 so that the tip surface of the optical fiber 2 is positioned from the tip of the ferrule 1 as shown in FIG.
Bull is fixed.

Here, an optical cable with a length of 10 m and a length of 3
A method of commonly using a 0 m optical cable as a transmission path of an optical signal emitted from the light emitting element 4 without adjusting the emission intensity of the light emitting element 4 will be described. However, the light emission output of the light emitting element 4 is assumed to be parallel light. When the optical fiber 2 shown in FIGS.
The difference in coupling loss when 0 m is about 5 dB, 30 m
Naturally, the optical fiber 2 has a larger loss. Therefore,
When a 10 m optical cable is coupled to the light emitting device 4, the structure shown in FIG.
As shown in, a gap G is provided between the tip end surface of the optical fiber 2 and the light emitting surface of the light emitting element 4. It can be seen from the relationship between the gap G and the coupling loss in FIG. 3 that the gap G should be about 2.0 mm. The difference in coupling loss varies by about ± 0.5 dB per surface depending on the degree of polishing finish (# 2000) of the tip surface of the optical fiber 2.
It can be treated as almost the same loss. However,
FIG. 3 shows values when the numerical aperture (numerical value corresponding to the incident refraction limit angle of light to the end face of the optical fiber) NA of the optical fiber 2 is 0.5. Also, the numerical aperture NA of the optical fiber
Has a characteristic that the larger the value of, the greater the attenuation of light per unit length in the optical fiber.

According to this embodiment, the optical cable is connected to the cable.
The optical cable is attached to the ferrule 1 such that a gap G is provided between the tip of the ferrule 1 and the tip surface of the optical fiber 2 when the optical cable 2 is attached to the ferrule 1. By making the appropriate gap G corresponding to the length of the optical cable attached to the ferrule 1,
The level of the light transmitted through the optical fiber 2 can be kept within the dynamic range of the light receiving element on the receiving side simply by exchanging optical cables of different lengths without adjusting the emission intensity of the light emitting element 4 on the transmitting side. It is possible to make adjustments, and it is possible to eliminate problems that occur when forming the optical communication path by changing the length of the optical cable.

In the above embodiment, the optical cable is 10
The case of exchanging m and 30 m has been described, but the present invention is not limited to this, and the optical cables a, b, cm ... Can be commonly used for the light emitting element 4 by appropriately changing the gap G. You can

[0015]

As described above, according to the optical fiber mounting apparatus of the present invention, the light emission of the light emitting element is changed by exchanging the optical fibers having different lengths without changing the light emitting level of the light emitting element on the transmitting side. When the strength is optimally adjusted, the equalization can be adjusted.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an optical fiber attaching device of the present invention.

FIG. 2 is a perspective view illustrating an attachment method for attaching an optical fiber to a felt.

FIG. 3 is a diagram showing a list of relationships between a gap G provided between a tip end surface of an optical fiber and a light emitting surface of a light emitting element and a coupling loss.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ferrule 2 ... Optical fiber 3 ... Case 4 ... Light emitting element

Claims (1)

[Claims] 1. An optical fiber mounting device, wherein a tip end surface of an optical fiber and a light emitting surface of a light emitting element are arranged to face each other with a predetermined gap therebetween.