JPH11133274A - Optical transmission module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily attain equivalence of light source low excitation NA by forming a circular light passing window on an optical path up to a light emitting element and an optical fiber incident port and shielding an optical beam of which exit angle is large, to improve a code error ratio, and to maximize the reception allowable level of a receiver by displacing the coupling efficiency of a light emitting/receiving element with optical fibers having respectively different core diameters at the same level. SOLUTION: The optical transmission module is constituted of a receptacle housing consisting of a synthetic resin mold for storing a plastic package 6 for storing a light emitting element 5. A lens 8 is formed to maximize coupling efficiency among the element 5, a platic clad silica optical fiber(PCF) 2 and a plastic optical fiber(POF) 3. The housing is provided with a room for storing the package 6. Thus exit light from the element 5 is efficiently entered into the PCF 2 and the POF 3 through a light passing window having an optimum diameter and arranged on an optimum set position by shiel-ding an optical beam having a large exit angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber to be used in which a plug holding an optical fiber is fitted into a receptacle housing holding a light emitting element and a light receiving element to form a connection state with the light emitting element and the light receiving element. The present invention relates to an optical transmission module configured to maximize a transmission / reception level difference determined by characteristics and performances of a transmitter and a receiver.

[0002]

2. Description of the Related Art In a conventional optical transmission module, for example, as shown in FIG. 7, a plastic package 6 holding a light emitting element 5 is press-fitted and fixed in a receptacle housing 1, and optical fibers 2, 3 with ferrules 4 are formed in the receptacle housing 1. Into the fitting opening. The ferrule 4 enters the optimum coupling portion with the plastic package 6 and efficiently emits light from the light emitting element 5 to the optical fibers 2 and 3.
It is configured so that it can be taken in. Similarly, the light receiving element is optimized so that the light emitted from the optical fiber can be most efficiently taken in.

As known examples, Japanese Patent Publication No. 7-117628,
No. 61-179511.

[0004]

SUMMARY OF THE INVENTION In the conventional configuration,
High excitation NA of light emitting element and POF in optical fiber
If (plastic optical fiber) is used beyond a certain length, the bit error rate tends to deteriorate due to mode dispersion and the like.

[0005] In addition, when an optical transmission module is used, an optical fiber may be properly used depending on a transmission distance or the like.
Optical fiber having a core diameter different from that of the light emitting element, for example, a POF having a core diameter of 980 nm and a core diameter of 200 nm
The difference between the respective coupling efficiencies at the time of optical coupling with the PCF (plastic-clad silica optical fiber) having the above and the difference between the respective coupling efficiencies at the time of optical coupling between the light receiving element and the POF and the PCF are not the same. There is a drawback that the transmission / reception level difference is narrowed when such an optical fiber is fitted.

[0006]

In order to solve the problem, a light-transmitting window is provided in the light path between the light-emitting element and the optical fiber entrance, and the diameter and the setting position of the light-transmitting window are optimized. Accordingly, the light beam with a large emission angle emitted from the light emitting element is shielded, thereby realizing the equivalent characteristic of the low excitation NA of the light source. Further, by the means, the coupling efficiency difference between the light emitting element and the light receiving element with the optical fiber having different core diameters can be displaced at the same level.

The present invention optimizes the diameter of the light-transmitting window and the setting position of the light-transmitting window with the above-described configuration, thereby improving the optical characteristics and enabling stable production.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described. FIG. 1 shows the configuration of the optical transmission module of the present invention. FIG. 2 shows a coupling state between a ferrule 4 having optical fibers 2 and 3 in the receptacle housing 1 and a light emitting element 5.

The product of the present invention comprises a plastic package 6 for housing the light emitting element 5 and a receptacle housing 1 for housing the plastic package 6. The plastic package 6 is a package sealed with a synthetic resin having a light-transmitting property. The entire package is flat and rectangular, and the input / output terminals 7 protrude. Further, a lens 8 is formed on the plastic package 6 in order to optimize the coupling efficiency between the light emitting element 5 and the PCF2 and POF3. The receptacle housing 1 is made of a synthetic resin molded product, and has a chamber for accommodating the plastic package 6. Light emitted from the light emitting element 5 is efficiently taken into the optical fibers PCF2 and POF3 through the light transmission window 9. Similarly, the light receiving element is optimized so that light emitted from the optical fiber can be efficiently taken in.

[0010]

[Table 1]

Table 1 shows the transmission / reception coupling efficiency when the optical fiber and the light emitting / receiving element are coupled as shown in FIG. The difference in the fiber coupling power between the POF and the PCF using the same light source is about 11 dB. This is the difference in the amount of light taken in between the POF having a large core of 980 nm and the PCF having a core diameter of 200 nm. POF and P
The difference in fiber output power required to convert the light emitted from the CF into the same current by the light receiving element is 5 dB.
This is mainly caused by the difference in the coupling efficiency with the light receiving element due to the spread of the light beam emitted from each core diameter and the difference in the NA of the optical fiber. From this, it can be seen that the transmission / reception level difference of the optical transmission module when the POF is coupled to the light receiving element is 15 dB and that when the PCF is coupled is 9 dB, and the PCF is 6 dB narrower than the POF.
FIG. 2 shows the fiber coupling power fluctuation at the gap between the PCF and the lens. As the gap becomes larger, the coupling power is attenuated. Therefore, the optimal setting position of the light transmission window is important. As a result, up to 0.4 mm is acceptable.

FIG. 3 is a graph showing the dependence on the diameter of the light transmission window for setting the difference in the fiber coupling power between the POF and the PCF to about 5 dB. This attenuates the fiber coupling power by blocking the light beam having a large angle of incidence on the POF by the configuration of FIG. However, it is important to find a light transmission window diameter that does not change the light incident on the PCF. With this configuration, it is possible to reduce the difference in the fiber coupling power between the POF and the PCF when the same light source is used. As a result, an optimum diameter of Φ0.5 mm has been found.

FIG. 4 shows an embodiment of the present invention in which the same effects as in FIG. 1 can be obtained.

When the lens 8 for optimizing the coupling efficiency between the light emitting element 5 and the PCF 2 or POF 3 is formed so as to be recessed from the front surface of the plastic package 6, a shape similar to the recessed shape is formed. The washer 10 is fitted from the front of the plastic package 6.

FIG. 5 shows a fitting state of the washer 10 and the plastic package 6. When the washer 10 is in a fitted state with the plastic package 6, the light transmitting window 9 is provided at a position where the coupling efficiency between the light emitting element 5 and the PCF2 or POF3 is optimized as shown in FIG. This configuration is the same as the effect shown in FIG.

FIG. 6 shows the measurement results of the bit error rates of the present structure and the conventional structure. The characteristic of the present structure for realizing the equivalent of the low excitation NA was that the power penalty was 1 dB or less at the error rate of 10-9. The conventional structure has a large deterioration, and stable transmission has not been performed.

Naturally, the size of the light emitting and receiving element,
If the configuration of the plastic package, the optical fiber to be used, and the like are different, the optimum diameter and the set position of the light transmitting window are changed.

Further, the present invention naturally exerts an effect on the coupling between a generally used can package and an optical fiber.

[0019]

According to the present invention, by optimizing the light-transmitting window diameter and the set position, the light source is equivalent to a low excitation NA,
In addition, it is possible to easily realize a bidirectional optical transmission module capable of maximizing a light receiving level range provided by the receiver.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is an example of a characteristic showing a fiber coupling power attenuation required until reaching the present invention.

FIG. 3 is a characteristic example showing a fiber coupling power attenuation according to the present invention.

FIG. 4 is a configuration diagram showing one embodiment of the present invention.

FIG. 5 is a configuration diagram showing one embodiment of the present invention.

FIG. 6 is a characteristic example showing a bit error rate according to the present invention.

FIG. 7 is a configuration example showing a conventional technique.

[Explanation of symbols]

1. Receptacle housing 2. PCF (plastic clad silica optical fiber 3. POF
(Plastic optical fiber) 4 ... Ferrule 5 ... Light emitting element 6 ... Plastic package
7 Input / output terminal 8 Lens 9 Light transmission window 10 Washer

Claims (2)

[Claims] A light-emitting element and a light-receiving element are housed in a plastic package, respectively, and a plug holding an optical fiber with a ferrule is fitted into a receptacle housing for holding the plastic package to determine a connection state between the light-emitting element and the light-receiving element. In the optical transmission module to be formed, a circular light-transmitting window is provided on the optical path between the light-emitting element housed in the plastic package and the optical fiber entrance, and a light beam with a large exit angle is shielded, so An optical transmission module having the feature of limiting the incident NA and realizing the equivalent of the low excitation NA of the light source. 2. The coupling efficiency between an optical fiber having a different core diameter and a light emitting element, wherein an optical fiber with a ferrule having a different core diameter can be fitted to the same light source. Also, the coupling efficiency between an optical fiber having a different core diameter and a light receiving element is different. In addition, it is desirable that the coupling efficiency between the light emitting and receiving elements with optical fibers having different core diameters be displaced at the same level. A circular light-transmitting window is provided on the optical path between the light-emitting element and the optical fiber entrance, and the light beam with a large exit angle is shielded, so that the coupling efficiency between the light-emitting and light-receiving elements with optical fibers with different core diameters is at the same level. An optical transmission module having the feature of being displaced by.