JP2002006182A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost optical module for a subscriber communication system in which the reliability of the life is assured. SOLUTION: An electric contact and an optical coupling system are coated and protected with a translucent resin, and an optical fiber is fixed with a resin having elasticity 1 GPa or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical communication system, and more particularly to an optical communication module.

[0002]

2. Description of the Related Art Conventionally, an optical module including an optical fiber and a light emitting / receiving element is housed in a package sealed by a hermetic seal. That is, the portion where the fiber protrudes outside the package is hermetically sealed by melting and fixing the package and the fiber by YAG welding or the like, and the package and lid are hermetically sealed by soldering or the like. The package itself is also made of metal or ceramics in which a metal is laminated on a portion bonded to a lid or a fiber.

Here, the hermetic seal is used to secure air-tightness because the optical element is sensitive to humidity, and a long-term reliability of module operation is ensured by adopting a structure in which moisture does not enter inside.

[0004]

SUMMARY OF THE INVENTION The optical module of the present invention is particularly intended for application to a subscriber communication system. Therefore, it must be low-cost and mass-produced for installation in each home. In addition, it is necessary to guarantee the life reliability of the communication device.

[0005] However, the conventional optical module has the following problems.

In order to hermetically seal the module, it is necessary to ensure airtightness with the package even at a terminal portion for making electrical connection with internal components. Similarly, an expensive optical fiber is used, which is metal-plated in order to seal the package from the package. In addition, the operation of hermetically sealing the inside of the module package is complicated and time-consuming, and the operation of confirming the air-tightness is also complicated and time-consuming. In particular, the part where the fiber sticks out of the package is YAG
Because the module is melted and fixed by welding or the like, the fiber may be broken at the projecting portion of the fiber when carrying the module. In order to prevent this fiber breakage, a protective material is separately required. Further, when the fiber fixing portion is fixed with a resin having a high elastic modulus, the temperature characteristics of the optical module fluctuate.

[0007]

An object of the present invention is to provide an electric contact and an optical coupling system which are covered and protected by a light-transmitting resin and the optical fiber is fixed by a resin having an elastic modulus of 1 GPa or less. The optical module is characterized in that:

That is, according to the present invention, particularly, an optical element which is sensitive to humidity is coated with a light-transmitting resin, so that ionic impurities which promote an electrocatalytic reaction enter the element interface or water stays at the interface. To prevent you from doing so.
Further, by covering the electric contacts with the resin, it is possible to prevent electric contact and reduce mechanical shock of the parts. As a result, even if the optical communication module package is simply hermetically sealed with a resin instead of hermetically sealed with a hermetic seal, the life reliability of the communication device can be guaranteed. Further, it is possible to use not only metals and ceramics but also plastics such as epoxy resins and liquid crystal polymers as the package members. In addition, by fixing the optical fiber with a resin with an elastic modulus of 1 GPa or less, especially at the part protruding out of the module, it is possible to prevent fiber breakage which is a problem in modules fused and fixed by conventional YAG welding etc. Can be. Further, the fixing with the resin having the above-mentioned elastic modulus can be easily performed during the module manufacturing process, and there is no need to separately prepare a protective material for preventing fiber breakage, and the temperature characteristics of the module are stabilized.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sample diagram used for studying the reliability of a laser diode (LD) as a light emitting element. FIG. 2 is a sample diagram used for studying the reliability of a photodiode (PD) as a light receiving element. FIG. 3 shows a sample diagram for examining the strength of the protruding portion of the fiber and the examination results.

FIGS. 4 and 5 are diagrams of an optical communication module manufactured based on the results of the study shown in FIGS.

Embodiment 1 Study of Reliability of Laser Diode (LD) FIG. 1 shows a laser diode (LD) element for optical communication. Reference numeral 2 denotes a light-transmitting resin for LD protection. Reference numeral 3 denotes a light receiving module (PD module) that receives the light output from 1 and converts the light into an electric signal, and is a commercially available PD with a hermetic seal so as not to be affected by humidity.
The module was used for testing. Reference numerals 4 and 5 denote substrates for electrically connecting the LD and PD modules, respectively, on a substrate 6 for supplying power from an external power supply, a distance of 1 to 3 due to the influence of temperature and humidity. Was fixed by soldering so as not to change.

In the LD reliability test, the sample shown in FIG.
It was put into an environmental test tank at 85 ° C. and a relative humidity of 85%, and the current supplied to 1 was controlled externally so that the output received at 3 became a constant value. Similarly, the battery was charged into a test tank under a thermal cycle condition of -40 ° C to 85 ° C, and the current supplied to 1 was controlled from the outside so that the output received at 3 became a constant value. The criterion for determining the degree of reliability was that the fluctuation of the current flowing through 1 was within 10%, and 5000 hours or 5000 cycles.

An acrylic resin, an epoxy resin, a silicone resin, and a urethane resin were used as the light-transmitting resin of No. 2, respectively, and a test was conducted with a sample not using No. 2. The number of samples was 10 for each resin. Although no particular problem occurred in the heat cycle test, 85
In the environmental test at 85 ° C. and a relative humidity of 85%, the judgment standard was exceeded in a test of several tens to several hundred hours using any of the resins, although the degree was different depending on the resin. As a result of analysis, no deterioration was observed in the LD filled with the resin. The deteriorated portion was found in the portion where 3 itself and 3 and 5 were electrically joined and the portion where 4 and 6 were joined.

FIG. 1 shows a portion covered with the transparent resin.
The reliability test at 85 ° C. and 85% relative humidity was performed by modifying the sample so as to cover all the components mounted on the substrate 6 without being limited to the peripheral portion of the LD as described above. As a result, the output fluctuation was able to be suppressed within the criteria for all the samples.

Example 2 Study on Reliability of Photodiode (PD) FIG. 2 shows a light-transmitting resin as in Example 1. Reference numeral 7 denotes a photodiode (PD) as a light receiving element. 8 is PD
A mounting substrate, which was fixed to the stem 9 with an adhesive. P
The D p-electrode and the n-electrode were respectively bonded to the pins of the stem 9 with gold wires.

In the reliability test of the PD, the sample of FIG.
The sample was put into an environmental test tank at 85 ° C. and a relative humidity of 85%, and a reverse bias of 10 volts was applied to PD. Similarly from -40 ° C to 85
The sample was put into a test tank under a thermal cycle condition of ° C., and a reverse bias of 10 V was applied to PD. The test sample was returned to room temperature every 100 hours or 100 cycles and the PD dark current was measured. The criterion for the reliability was that the measured dark current at −5 volts was less than 5 times the initial value, and was 5000 hours or 5000 cycles.

An acrylic resin, an epoxy resin, a silicone resin, and a urethane resin were used as the light-transmitting resin of No. 2, respectively, and a test was performed with a sample not using No. 2. The number of samples was 10 for each resin. No particular problem occurred in the heat cycle test. 85 ℃
In an environmental test at a relative humidity of 85%, the dark current exceeded the reference value in 10 to several hundred hours for all samples not using 2. All the samples using the transparent resin satisfied the standard.

(Example 3) Investigation of the strength of the protruding portion of the fiber FIG. 3 is a sample diagram for examining the strength of the protruding portion of the fiber. The lower left part of FIG. 3 is a view of the upper part viewed from the direction b. Reference numeral 10 denotes an aluminum substrate, 11 denotes a resin for fixing and protecting an optical fiber, and 12 denotes an optical fiber. An acrylic resin, an epoxy resin, a silicone resin, a urethane resin, a polyamide, a polyimide, a liquid crystal polymer, a thermoplastic polyolefin, an ABS resin, and a rubber were used as the resin No. 11. The aluminum substrate 10 has cuts from both sides at the position where the fiber is mounted, and changes the depth h and width w in various ways to change the shape in which the resin accumulates, and measures the peel strength in the a direction and the pull strength in the b direction, respectively. did. Although there is an absolute difference in strength depending on the resin, a correlation as shown on the right side of FIG. 3 was observed between the fiber peeling strength and the pulling strength and h of the aluminum substrate. It should be noted that any of the above-mentioned resins satisfies both the initial peeling strength and the initial pulling strength.

Although the peeling strength and the pulling out strength satisfy the standards, when the elastic modulus of the resin 11 is 1 GPa or more, the fiber is easily broken when the fiber is peeled, and when the elastic modulus of the resin 11 is 1 GPa or less, There is a problem in that the resin stretches greatly when the fiber is pulled out, and a direct force is applied to the portion where the fiber is fixed inside the substrate.

Example 4 Fabrication of Optical Module FIG. 4 is an external view of a module fabricated based on the results of examination up to Example 3. FIG. 5 is a cross-sectional view taken along the line AA 'of the module shown in FIG.

In FIG. 4, 12 is an optical fiber as in the third embodiment, 13 is a case, 14 is a lid, 15 is a lead pin, and 16 is a connector.

Hereinafter, the optical module of FIG. 5 will be described.

Reference numeral 1 denotes the same LD as in the above embodiment, and reference numeral 7 denotes the PD described in the above embodiment. Reference numeral 16 denotes the depth of the V-groove so that the fiber comes to a position where the optical coupling becomes maximum when the fiber is pressed into the V-groove, based on the diameter of the fiber 12-1 and the height of the light receiving portion of the active layer PD of the LD. This is a silicon substrate in which the thickness of the LD / PD solder is adjusted. Case 13
The lead frame 15 for grounding lead pins for exchanging electrical signals between the outside and the optical element is resin-molded, and when the silicon substrate 17 is mounted on the case, the optical fiber 12 is horizontally A U-shaped groove is formed slightly deeper than the depth protruding from the case. First, the silicon substrate 16 on which the LD 1 and the PD 7 were mounted was bonded and fixed to the case 13 with a conductive adhesive so as not to short-circuit the wiring. Next, the optical fiber 12-1 is pressed into the V groove of the silicon substrate and fixed with an adhesive, and the resin 11 for fixing and protecting the optical fiber is inserted into the U-shaped groove of the case.
Was injected and fixed. Then, the light-transmissive resin 2 was injected into the inside of the case, and then the lid 14 was adhered and fixed to the case 13.

(Example 5) Examination of reliability of optical module The operation reliability test of the module was performed under the environment of 85 ° C. and 85% relative humidity with respect to the module of FIG.
Operation reliability test under thermal cycle conditions of −40 ° C to 85 ° C,
A continuous operation test at −40 ° C. and a continuous operation test at 85 ° C. were performed. Under these circumstances, the module was exposed, and the current supplied to LD1 was externally controlled so that the optical output from the fiber became a constant value. Also, a bias was applied to PD2 so as to be always in a light receiving state. The reliability criterion is that the fluctuation of the current flowing through LD1 is within 10%,
LD1 threshold current fluctuation within 10%, PD2 dark current measurement at -5 volts less than 5 times initial, 5000 hours or 50 hours
00 cycles.

As a result of the reliability test, the elastic modulus of the resin 11 protecting the portion where the optical fiber protrudes outside the module is 1
In the case of GPa or more, it was found that the fluctuation of the current flowing through the LD1 and the fluctuation of the fiber output exceeded 10% in several hundred hours in any of the reliability tests of the module. Any module manufactured using a resin 11 having an elastic modulus of 1 GPa or less satisfied the reliability test.

[0027]

The light receiving module of the present invention can supply a large amount of communication systems at low cost by simply sealing the package with an adhesive instead of hermetically sealing the package with a hermetic seal. In particular, by covering the light receiving / emitting element with the light transmitting resin, the life reliability of the communication device is guaranteed. Further, by fixing the optical fiber with a resin at a portion protruding out of the module, fiber breakage can be prevented and the module manufacturing process can be simplified.

[Brief description of the drawings]

FIG. 1 is an LD reliability sample diagram according to an embodiment of the present invention.

FIG. 2 is a PD reliability sample diagram according to an embodiment of the present invention.

FIG. 3 is an optical fiber adhesive strength test sample diagram according to an example of the present invention.

FIG. 4 is an external view of an optical module according to an embodiment of the present invention.

FIG. 5 is a sectional view taken along line A-A 'of FIG.

[Explanation of symbols]

1. Laser diode (LD) 2: Light transmissive resin
3: light receiving module, 4: LD wiring board, 5: PD wiring socket, 6: board, 7: photodiode (P
D), 8: PD wiring board, 9: Stem, 10: Aluminum substrate, 11: Optical fiber fixing / protecting resin, 12: Optical fiber, 12-1: Optical fiber (core part), 13: Case, 14
... lid, 15 ... lead pin / lead frame, 16 ... connector, 17 ... V-groove board.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H037 AA01 BA02 BA11 DA03 DA04 DA17 DA36 5F073 EA29 FA02 FA07 FA22 HA05 HA12 5F088 AA01 BA11 BB01 JA06 JA10 JA14 JA20

Claims (4)

[Claims] 1. An optical module comprising a light receiving and emitting element and an optical fiber optically coupled to the light receiving and emitting element, wherein electrical contacts and an optical coupling system are covered and protected by a light transmitting resin, and the optical fiber is An optical module comprising a portion fixed by a resin having an elastic modulus of 1 GPa or less. 2. An optical module comprising a light emitting / receiving element and an optical fiber optically coupled to the light emitting / receiving element, wherein the optical fiber is provided with a portion fixed by a resin having an elastic modulus of 1 GPa or less. Optical module. 3. The optical module according to claim 1, wherein a resin having an elastic modulus of 1 GPa or less is accumulated around the fiber at a portion where the optical fiber protrudes outside from a substrate or a container on which the light emitting / receiving element and the optical fiber are mounted. An optical module characterized in that a container is formed in various shapes. 4. An optical component having at least one optical fiber, wherein each fiber is fixed at two points, and the distance between the two points is 5 cm or less, wherein An optical component, wherein a fixing portion closer to the fiber end of the optical component is fixed with a material having an elastic modulus of 1 GPa or more, and a fixing portion farther from the fiber end inside the optical component is fixed with a material having an elastic modulus of 1 GPa or less. .