JP2963324B2 - Receiver / transmitter module for optical communication - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitting / receiving module for optical communication. More specifically, the present invention relates to a transmission / reception module in which coupling between a rod lens and a ferrule is improved and coupling efficiency of signal light is improved.

[0002]

2. Description of the Related Art In recent years, optical communication using an optical fiber has rapidly spread, and is being used for personal use such as telephone and facsimile and mass media such as television information. Also, in a company, terminals are arranged at each factory, each department, etc., connected by optical fibers, and an optical LAN (Local Area) capable of exchanging information in real time.
a Network) system is becoming widespread. In this case, it is necessary to further reduce the cost of the transmitter / receiver module consisting of a fiber coupler that connects the light-emitting element and light-receiving element of a terminal installed in each home with an optical fiber, etc. It has become.

As an optical coupling circuit, a method called a pigtail type as shown in FIG. 9 or a method of making a lens and a zirconia ferrule physically contact as shown in FIG. 10 have been considered.

A pigtail type transmitting / receiving module shown in FIG. 9 is mounted on a housing 25 such that a light emitting element 21 and a light receiving element 22 and a tip of a coupling optical fiber 23 are coupled via a half mirror 24, respectively. It is installed. The coupling optical fiber 23 attached to the housing 25 forms a loop 26 to prevent disconnection due to bending, and an adapter
27 is connected to an external transmission optical fiber line.

[0005] Further, a light emitting / receiving module of the type shown in FIG. 10 in which a lens and a ferrule are in physical contact with each other has a light emitting element 21 and a light receiving element 22 each of which is a half mirror.
These are attached to a housing 25 so as to be optically coupled to a lens 28 via 24, and a zirconia ferrule 29 is further physically contacted at the tip of the lens 28, and an external optical fiber is inserted into the ferrule 29. It is connected by inserting the tip of 30. This lens
The abutting surfaces of the ferrule 28 and the zirconia ferrule 29 are each polished into a convex spherical shape to obtain a physical contact.

[0006]

In the above-mentioned pigtail type, the coupling optical fiber 23 between the adapter 27 and the housing 25 is easily bent when bent in an S-shape. Therefore, the housing 25 and the adapter 27 need to be connected to each other, which requires a loop space, which causes a problem that the module becomes large.

Further, there is a problem that the number of components such as a coupling optical fiber and an adapter increases and the cost increases.

[0008] In addition, a lens in which a lens and a ferrule made of zirconia are physically contacted can be miniaturized and the number of parts is small. However, in the case of a commercially available ferrule, the center of the radius of curvature R of the polished surface is eccentric. Eccentricity of polished surface is 50μm
If there is a degree, a gap is created between the lens and the core of the optical fiber, the signal light is reflected at the end face of the optical fiber, the coupling efficiency is reduced, and the reflected light becomes return light, which causes noise in the semiconductor laser. There's a problem.

In addition, since the gap changes due to expansion or contraction of the lens and the ferrule due to a change in the ambient temperature, there is also a problem that the temperature characteristics of the transmission / reception module are deteriorated.

An object of the present invention is to solve such a problem and to provide an optical communication transmitting / receiving module that can be efficiently coupled even if the R center of the convex polished surface of the ferrule is slightly eccentric.

[0011]

The transmitting / receiving module for optical communication according to the present invention comprises at least a light emitting element, a light receiving element,
A light emitting element, a light receiving element, and an optical fiber by converging light from the light emitting element to the tip of the rod lens and making a ferrule of an optical fiber physically contact the tip face of the rod lens. Wherein the rod lens is held in a housing by a support supported by a spring member via a cover electrode, and an outer diameter of the rod lens is an outer diameter of the ferrule. An opening is provided in the housing so that the tip of the ferrule of the optical fiber is slipped on the other end side of the sleeve which is formed to have substantially the same diameter as that of the rod lens. Things.

Preferably, the light emitting element and the light receiving element are held by the support, and the relationship between the light emitting element and the light receiving element and the rod lens is always kept constant.

A part of the surface of the light receiving element is a reflecting surface, and reflects the light beam emitted from the light emitting element to converge it on the tip end surface of the rod lens. It is preferable to receive the received light from the optical fiber.

Preferably, the rod lens is formed of a glass material having a refractive index of 1.49 or less.

Preferably, the sleeve is a spring sleeve made of phosphor bronze.

It is preferable that the electrode terminals of the light emitting element and the light receiving element are led to the housing via the cover electrode.

Preferably, the package on which the light receiving element is mounted and the support are hermetically welded, and the rod lens and the support are hermetically sealed. In addition, the rod
The lens collects light from the light emitting element.
Is preferred.

[0018]

According to the present invention, the rod lens is held in the housing by the support member supported by the spring member via the cover electrode, and is coupled to the optical fiber via the sleeve which is fitted on the outer periphery of the rod lens. Therefore, even if there is an eccentricity in R of the physical contact surface of the ferrule, the central axes of the rod lens and the ferrule are maintained by the sleeve due to the pressing force from both sides, and the rod lens and the rod lens are controlled by the degree of freedom of the rod lens by the spring member. Physical contact at the center axis of the ferrule is obtained. As a result, the reflection loss at the contact surface is small, noise is not generated in the semiconductor laser, and stable coupling characteristics can be obtained even when the temperature changes at room temperature.

[0019]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory cross-sectional view of one embodiment of the transmission / reception module of the present invention.

In FIG. 1, a light emitting element 2 formed of, for example, a laser chip and a light receiving element 3 formed of, for example, a photodiode are mounted on a package 1, and the light receiving element 3 is held in a through hole provided in a support 4. While receiving the received signal light via the aspheric lens 5 and the rod lens 6, the light of the light emitting element 2 is reflected on the surface of the light receiving element 3 to guide the transmitted signal light into the through hole formed in the support 4. ing. An aspheric lens 5 and a rod lens 6 are provided in the through hole.
Are held, and the signal light emitted from the light emitting element 2 is focused on the optical fiber connection side end face of the rod lens 6 by these two lenses.

An electrode terminal 11 for inputting a drive signal for driving the light emitting element 2 and an electrode terminal 12 for outputting a light receiving signal from the light receiving element 3 are respectively drawn out to the housing 10 via the cover electrode 9. I have. The electrode terminal of each element is once connected to the base 9a of the cover electrode 9 by a lead wire 15 and pulled out toward the housing 10 through the cover electrode 9, whereby the support 4 has a degree of freedom in the direction perpendicular to the axis of the sleeve 7. Provided, and the rod lens can be pressed against the ferrule.

In this embodiment, a light beam is emitted from the light emitting element 2 in the horizontal direction, and the beam is reflected by the surface of the light receiving element 3 whose surface is inclined at about 30 ° with respect to the horizontal direction. The package 1 is condensed by the package 5 so as to be condensed on the end face of the rod lens 6 on the optical fiber 13 side.
An aspheric lens 5 and a rod lens 6 are fixed to the support 4. Since these are integrally fixed, a physical contact with the core of the optical fiber can be easily obtained as described later.

FIG. 2 shows the relationship in which the beam emitted from the light emitting element 2 is condensed at the tip of the rod lens 6. When a method of reflecting the transmission signal light emitted from the light emitting element 2 about half of the surface of the light receiving element 3 as in the present embodiment is used, the module can be reduced in size and the optical system can be made axial.
Physical contact can be easily made. Further, since the light receiving element 3 is on the optical axis of the transmission / reception light, there is no need to use another optical system such as a half mirror, and the element can be simplified. In this case, a reflection film made of a metal film such as Au or Al is provided on the surface serving as the reflection surface of the light receiving element 3, and a number of small holes are provided in the reflection film so that the antireflection film below the reflection film can be formed. It is preferable to adopt a structure in which a reflective film is provided so as to be exposed and about 50% of the surface area. In optical communication, the transmission and reception signal light is normally performed in a time-division manner using pulses. By adopting such a structure, transmission and reception are performed alternately on the light receiving element. Can be monitored, and the light receiving element for monitoring can also be used, so that the element can be further simplified. In the light receiving element 2, the light receiving element for monitoring the emitted light beam may be provided at a different place adjacent to the light receiving element portion of the received signal light.

The rod lens 6 has an outer diameter of an optical fiber.
The dimensions are substantially the same as the outer diameter of the 13 ferrules 8 (for example,
2.5 mm), and is fixed to the support 4 at one end so as to be coaxial with the beam from the light emitting element 2. The term “substantially the same size” refers to the extent to which the rod lens 6 and the ferrule 8 slide together with the inner diameter of the sleeve 7 containing the split 7a. The end surface of the rod lens 6 on the connection side with the optical fiber 13 is polished into a convex spherical shape having a radius of curvature of about 20 mm, and formed so as to make physical contact with the tip surface of the ferrule 8 of the optical fiber 13 also polished into the convex spherical shape. ing. A sleeve 7 made of phosphor bronze having a split 7a as shown in FIG. 3, for example, is fitted on the outer periphery of the rod lens 6 so that the center axis of the rod lens 6 and the ferrule 8 at the tip of the optical fiber 13 coincide. Act on.

As shown in FIG. 3, the sleeve 7 has, for example, a thickness of about 0.25 mm, a length of about 12 mm, and a split 7a, and is formed in a free state to have an inner diameter of 2.485 mm, for example. And the rod lens 6 and the ferrule 8
Are both formed to the same outer diameter of 2.5 mm, so that when the rod lens 6 and the tip of the optical fiber 13 are inserted from both ends, they are connected concentrically. The ends of the rod lens 6 and the ferrule 8 each have a radius of curvature of 20 mm as described above.
It is polished to a convex spherical surface, but the center of the spherical surface is 40 ~
A deviation of about 50 μm is likely to occur. In other words, ferrules are made of zirconia, etc., are mass-produced and marketed, and the concentricity of the ferrule and the core is accurately formed at 1.4 μm or less. Eccentricity is likely to occur. ADVANTAGE OF THE INVENTION According to the transmission / reception module of this invention, even if there exists eccentricity of the spherical surface of a ferrule, a favorable coupling characteristic with the physical contact of a rod lens and a ferrule in a center axis is obtained. The operation will be described with reference to FIGS.

As shown in FIGS. 4A and 4B, the center of the polished surface of the ferrule 8 and the rod lens 6 is the center axis C.
Are shifted in opposite directions with respect to
(A) indicates that physical contact is obtained substantially on the central axis, and when the center of the polished surface is coincident with the central axis of the ferrule (see FIG. 4 (b)), the physical contact is on the central axis. And the coupling characteristics are improved. However, as shown in FIG. 5 (a), when the eccentric direction of the center of the polished surface is the same direction between the ferrule 8 and the rod lens 6, the center axis of the rod lens 6 and the ferrule 8 through which light is transmitted. Respectively, a gap between h ₁ and h ₂ is generated. However, according to the present invention, the rod lens 6 is
And the rod lens 6 and the ferrule are slid into the sleeve 7 having spring properties so that about 1
As shown in FIG. 5B, the central axes of the rod lens 6 and the ferrule 8 are in physical contact with each other in such a manner that the sleeve 7 is slightly pushed and spread as shown in FIG. 5B. The coupling characteristics between the optical fiber and the light receiving / emitting element are improved, and the temperature characteristics are improved without changing the gap on the central axis even when the room temperature changes.

Next, the present invention will be described in more detail with reference to specific examples. FIG. 6 shows the relationship between the radius R, the eccentricity L, the gap h, and the eccentric angle θ of the convex spherical surface. The outer diameter of both the rod lens 6 and the ferrule 8 is 2.5 mm, the eccentricity L ₁ of the polished surface of the rod lens 6 is 50 μm, and the eccentricity L _{2 of the} ferrule 8 is
40 μm (see FIG. 6 for eccentricity L), the radius of curvature R of the polished surface is 20 mm each, and the sleeve 7 is made of phosphor bronze having a length of 14 mm, and has a free inner diameter of 2.485 mm and a plate thickness of 0.25 mm. When the pressing force of the ferrule is 1 kgf, the gap between the contact surface and the center axis of the rod lens 6 is h ₁ , and the gap between the contact surface and the center axis of the ferrule 8 is h ₂ (FIG. 5).
(See (a)), the contact surface and the rod lens 6
Gap h ₁ is _{h 1 = R-Rcos (sin} -1 (L 1 / R)) = 20-20cos (sin -1 (0.05 / 20)) = 0.0000625 mm = 0.0625μm , and the contact surface between the central axis of a gap h ₂ between the center axis of the ferrule _{8, h 2 = R-Rcos (} sin -1 (L 2 / R)) = 20-20cos (sin -1 (0.04 / 20)) = 0.00004 mm = 0.04μm Becomes

Therefore, assuming that a gap between the central axes of the rod lens 6 and the ferrule 8 is h, h = h ₁ + h ₂ = 0.1025 μm To make the gap h 0, the inclination of the rod lens must be θ ₁ ,
Assuming that the inclination of the ferrule is θ ₂ , θ ₁ = sin ⁻¹ (0.05 / 20) = 0.14 ° θ ₂ = sin ⁻¹ (0.04 / 20) = 0.11 °. h
Can be eliminated.

In this embodiment, since the sleeve 7 is made of phosphor bronze and has a spring property, the rod lens 6 and the ferrule 8 are inclined by applying a pressing force of about 1 kgf to the rod lens 6 and the ferrule 8, and the diameter of the sleeve is increased. The rod lens 6 and the core of the optical fiber in the ferrule 8 come into contact with each other, a physical contact with almost no gap h was obtained, and the reflection at the rod lens end face was reduced from 3% to 0.01%. In the case of the above example, since the length of the sleeve is 14 mm, if the rod lens is inclined by 0.14 °, the inner diameter of the sleeve is expanded by 17 μm.

Since the optical fiber core has a refractive index of 1.472 for the rod lens, it is preferable to use a glass material having a refractive index of 1.49 or less. This is because a glass having a refractive index of less than 1.472 cannot be obtained, and as the refractive index increases, the reflection increases. As such a glass, for example, SCHOTT (Germany) trade name BK10 (refractive index n = 1.485) can be used.

Further, the package 1 and the support are formed by welding a weld 17 as shown in FIG. 7 by resistance welding or by continuous YAG welding as shown in FIG. Is hermetically sealed (hermetic seal) by the seal portion 4a, so that the inside of the support is completely airtight, so that the aspheric lens 5, the light emitting element 2,
The environmental reliability of the light receiving element 3 can be improved.

The welding is not limited to resistance welding and YAG welding as long as airtight welding can be performed.

[0033]

According to the present invention, the rod lens is held by the support member supported by the spring member, and the ferrule of the rod lens and the optical fiber is held by the sleeve having the spring property. Even if there is an eccentricity of the spherical polishing surface formed on each of the contact surfaces, the rod lens and the core of the optical fiber make physical contact by the force pressed from both sides.
Therefore, a transmission / reception module for optical communication having excellent coupling efficiency can be obtained.

Further, since the physical contact is obtained in the core portion, the coupling characteristic does not fluctuate even if the ambient temperature changes, so that an optical communication transmitting / receiving module having excellent temperature characteristics can be obtained.

Further, the number of components can be reduced by reflecting light from the light emitting element and receiving and receiving light from the optical fiber while using a part of the surface of the light receiving element as a reflecting surface. Also, by fixing the light emitting element, light receiving element, aspherical lens, and rod lens to the support, and condensing the light from the light emitting element to a certain point, it is only necessary to center the optical fiber and the whole. High coupling efficiency can be obtained simply by pressing the optical fiber.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of an optical communication transceiver module of the present invention.

FIG. 2 is a diagram illustrating a state in which light from a light emitting element is condensed on a front end surface of a rod lens.

FIG. 3 is an explanatory diagram of an example of a sleeve.

4A and 4B are explanatory diagrams of a contact surface between a rod lens and a ferrule, wherein FIG. 4A is an example in which the eccentricity of the spherical surface of the rod lens and the ferrule is eccentric in a direction different from the center axis, and FIG. It is a diagram when they do not coincide and coincide with the central axis.

FIG. 5 is an explanatory view showing a physical contact state between a rod lens and a ferrule in a sleeve, and FIG.
FIG. 5B is a diagram showing an example in which the eccentricity of the spherical surface of the rod lens and the ferrule is eccentric in the same direction with respect to the center axis, and FIG. .

FIG. 6 is an explanatory diagram showing the relationship between the eccentricity of the convex spherical surface and the gap.

FIG. 7 is an explanatory sectional view showing a connection state between a package and a support of the optical communication transceiver module of the present invention.

FIG. 8 is an explanatory cross-sectional view showing a connection state between a package and a support of the optical communication transceiver module of the present invention.

FIG. 9 is an explanatory view showing a pigtail type as an example of a conventional transmitting / receiving module.

FIG. 10 is an explanatory diagram showing an example of a conventional receiving / transmitting module, in which a lens and a ferrule make physical contact.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Package 2 Light emitting element 3 Light receiving element 4 Support body 6 Rod lens 7 Sleeve 8 Ferrule 9 Cover electrode 10 Housing 13 Optical fiber 14 Spring member 16 Weld part 17 Weld part

──────────────────────────────────────────────────続 き Continuing on the front page (72) Naomi Aoki, 21st Mizozakicho, Nishinin-ku, Kyoto, Japan ROHM Co., Ltd. (72) Kenji Okada 1-1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-5-281441 (JP, A) JP-A-2-33113 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 6/42 H01L 33 / 00 H01L 31/0232

Claims (8)

(57) [Claims] At least a light emitting element, a light receiving element,
A light emitting element, a light receiving element and an optical fiber by converging light from the light emitting element to the tip of the rod lens and making a ferrule of an optical fiber physically contact the tip face of the rod lens. An optical communication receiving / transmitting module to be coupled, wherein the rod lens is held in a housing by a support member supported by a spring member via a cover electrode, and an outer diameter of the rod lens is equal to an outer diameter of the ferrule. A light having substantially the same diameter and provided with an opening in the housing so that the tip of the ferrule of the optical fiber is fitted to the other end of the sleeve which is fitted to the outer periphery of the rod lens. Receiving and transmitting module for communication. 2. The light-emitting element and the light-receiving element are held by the support, and the relationship between the light-emitting element and the light-receiving element and the rod lens is always kept constant.
The receiving and transmitting module described. 3. The light receiving element has a part of its surface as a reflection surface, reflects a light beam emitted from the light emitting element and condenses it on the tip end surface of the rod lens, and uses another part of its surface to reflect the light beam. The transmitting / receiving module according to claim 1, wherein the receiving / transmitting module receives light received from the optical fiber. 4. The transmission / reception module according to claim 1, wherein the rod lens is formed of a glass material having a refractive index of 1.49 or less. 5. The transmission / reception module according to claim 1, wherein the sleeve is a spring sleeve made of phosphor bronze. 6. The transmission / reception module according to claim 1, wherein electrode terminals of the light emitting element and the light receiving element are led out to the housing via a cover electrode. 7. The transmission / reception module according to claim 1, wherein the package on which the light emitting element and the light receiving element are mounted and the support are hermetically welded, and the rod lens and the support are hermetically sealed. 8. The light emitting device according to claim 8, wherein the rod lens is
The transmission / reception module according to claim 1, wherein the module collects light.
Le.