JP2003121689A - Optical module and method for assembling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module having superior characteristics through a small number of aligning operations. SOLUTION: A first and a second lens 21, 22 are aligned in the optical axis and fixed with a prescribed space apart. A first and a third optical fiber 11, 13 are parallellized in the optical axis, with a second optical fiber 12 also made parallel to them in the optical axis. In addition, a distance is set 1 mm or less between the center of the light emitting area of the first lens and the center of the light incident area of the oppositely facing second lens.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module mainly used in the field of optical communication, and more particularly to an optical module including a collimator composed of an optical fiber and a lens.

[0002]

2. Description of the Related Art In the field of optical communication, an optical functional element is inserted in an optical path when it is necessary to exert some action on light propagating through an optical fiber. Since the light emitted from the optical fiber diverges, a collimator that converts the divergent light into parallel light is often required in order to efficiently enter the light into these optical functional elements. Practically, it is advantageous to construct the system etc. by modularizing the collimator and the optical function element and using them as an optical module. As an example, FIG. 8 shows a typical example of a filter module that demultiplexes the lights of the wavelengths multiplexed in the wavelength division multiplexing optical communication.

For example, light in which two wavelengths λ1 and λ2 are multiplexed enters the lens 121 from the optical fiber 111. In this example, the lens 121 is a gradient index rod lens, and the refractive index is distributed in the radial direction of the circular cross section perpendicular to the optical axis. This lens can convert the divergent light emitted from the optical fiber into parallel light by appropriately designing the lens length. A demultiplexing filter 150 is arranged as an optical functional element in contact with the end surface of the lens 121 opposite to the light incident surface (the end surface facing the optical fiber 111). This filter 1
Reference numeral 50 reflects light of wavelength λ1 and transmits light of wavelength λ2. The light reflected by the filter 150 is again reflected by the lens 121.
The light is condensed by and is incident on the optical fiber 113.

On the other hand, the light (wavelength λ2) that has passed through the filter 150 is made incident on the lens 122 and is made incident on the optical fiber 112 in a condensed manner. Generally, the lens 121 and the lens 12
2 has the same characteristics. The filter module 200 is configured by integrating this optical system in one housing 170.

The basic optical system of the collimator used in such a module will be described with reference to FIG. Consider a case where point light sources 211 and 213 are placed on the focal plane 281 of the convex lens 221 on the optical axis 201 and at positions apart from the optical axis as shown in FIG. 9A. From the geometrical optics point of view, the light from the light source on the focal plane is convex lens 22.
It is converted into parallel light by 1. However, if the position of the light source is not on the optical axis, the direction of the parallel light is inclined with respect to the optical axis according to the position Δ of the light source. These collimated rays are transmitted to the second convex lens 222 having the same focal length as the first convex lens 221.
It goes without saying that the images 212 and 214 are formed at positions symmetrical with respect to the light source with respect to both lenses when the light enters.

The above-mentioned state of light rays is the same even when the lens is a gradient index rod lens as shown in FIG. 9 (b). This lens has a cylindrical shape, and the refractive index is distributed in the radial direction from the center of the cross section. This refractive index distribution n
(R) is ideally expressed by the following equation. n (r) = n ₀ (1- (A / 2) r ² ), where r is the distance from the center axis of the lens, n ₀ is the refractive index on the center axis of the lens, and A ^1/2 is It is a refractive index distribution constant. The meandering period (pitch) P of light rays in this lens is
It is represented by P = 2π / A ^1/2 . Here for simplicity,
A gradient index rod lens having a lens length of 0.25P will be exemplified. In the 0.25P lens, the light emitted from the point light source on the end face is emitted as parallel light. Consider a case where point light sources 311 and 313 are placed on one end surface of the first lens 321 on the optical axis 301 and at positions apart from the optical axis, respectively. When the position of the light source is not on the optical axis, the direction of the parallel light is inclined with respect to the optical axis according to the position Δ of the light source, as in the case of the convex lens. When these parallel rays are incident on the second lens 322 having the same pitch as that of the first lens 321, the image 312, at a position symmetrical to the light source with respect to both lenses,
Tie 314.

The same applies to the case of a convex lens, but when a lens having a finite effective diameter is placed on the same optical axis, the optical axis inclines when the inter-lens distance L becomes large, and in some cases part of it Ray cannot enter the second lens.

In the case of the filter module shown in FIG. 8, two optical fibers 111 and 11 are provided on one end surface of the lens 121.
3 are connected. Since each optical fiber has a finite diameter, at least one optical fiber will be placed away from the central axis of the lens. The light entering and exiting the optical fiber placed away from the central axis of the lens has an angle with respect to the central axis at the other end surface of the lens.

However, for example, if the optical axis of the optical fiber 111 coincides with the central axis of the lens 121, the light at the other end of the lens can be emitted parallel to the central axis of the lens 121, that is, in the direction perpendicular to the lens end surface. You can However, in this case, a part of the light reflected by the end face of the lens is
Returning to 11, this is not desirable in optical communication. Even when the problem of such reflected return light is not taken into consideration, it is necessary to constantly adjust the position of the incident light so that the light is emitted vertically from the lens end surface in terms of manufacturing the optical module.
Not always easy.

In order to prevent the reflected return light, the end surface of the optical fiber and the surface of the lens facing the optical fiber are processed into an oblique surface with respect to the optical axis as shown in FIG. That is usually done. The light emitted from the lens also tilts with respect to the optical axis even when entering and exiting from the surface tilted with respect to the optical axis.

In order to collect the light having a certain angle with respect to the central axis of the lens 121 as described above on the end face of the optical fiber 112 and make it enter with low loss, the central axis of the lens 122 is set to the optical fiber 111. A means for inclining the lens 121 in accordance with the angle of the light ray from the optical axis can be considered. This is the reason why the central axes of the lenses 121 and 122 are arranged at an angle in the filter module of FIG.

In order to arrange such a lens,
The inner diameter of the sleeve 160 must be made sufficiently larger than the diameter of the glass holder 144 in order to secure a space so that the angle can be adjusted.

A method of assembling the filter module 200 will be described. First, two optical fibers 111 and 11
The collimator 201 including the lens 3, the lens 121, and the filter 150 is assembled. The tips of the two optical fibers are inserted into, for example, a two-hole capillary 131, fixed with an adhesive, and then the end faces are polished. This capillary 131 with an optical fiber is inserted into a glass holder 140 covered with a cylindrical metal tube and fixed with an adhesive.

The filter 150 is adhered to the end surface of the lens 121, and the lens 121 is also inserted into the glass holder 142 and fixed with an adhesive. Light of wavelength λ1 is incident from the optical fiber 111, and reflected light from the filter 150 is reflected by the optical fiber 113.
The positions of the capillary 131 and the lens 121 are aligned in three directions of x ₁ , y ₁ and z ₁ so as to maximize the amount of light incident on. Here, the x ₁ and y ₁ axes are two directions perpendicular to the central axis of the lens 121 and perpendicular to each other, and the z ₁ axis is the lens 1
21 along the optical axis.

Next, the collimator 202 including the lens 122 and the optical fiber 112 is assembled. Lens 122
And the optical fiber 1 similarly fixed to the capillary 132.
12 is inserted into a common metal holder 144, and is aligned and fixed in the z ₂ axis direction. The z ₂ axis is taken in the optical axis direction of the lens 122.

Next, the two sets of collimators 201 and 202 assembled as described above are combined to assemble the filter module 200. As mentioned above, it is necessary to set the z ₁ axis and the z ₂ axis to be tilted. Light of wavelength λ2 is incident from the optical fiber 111, and the four axes of X, Y, θ _X , and θ _Y are adjusted so that the amount of light coupled to the optical fiber 112 is maximized. Here, the X and Y axes are two directions perpendicular to each other and perpendicular to the central axis of the housing 170, and the θ _X and θ _Y axes are rotation angles around the X axis and the Y axis, respectively. Although the centering of the housing 170 in the central axis direction (Z axis) may be performed, it may be omitted because the work becomes complicated.

On the other hand, since such an optical communication module uses a light beam having a small diameter, it is sensitive to positional deviation and angular deviation, and the angular deviation between the two collimators 201 and 202 exceeds 0.02 °. And the loss becomes large and it cannot be used. Such mechanical stability must be maintained, for example, in the operating temperature range, -20 to 70 ° C. For this reason, solder is generally used to fill a relatively large space and to reliably fix lenses and optical fibers. Resin is easy to handle,
It is not suitable because it shrinks during curing and has a large coefficient of thermal expansion.

In the filter module 200, the solder 1 is fixed to the slanted sleeve 160 and the glass holders 140, 142 and 144 covered with metal tubes.
80 is used. The solder is poured from a solder injection hole 182 provided in the sleeve 160. The housing 170 and the sleeve 160 are fixed by the resin 190, which also serves to protect the optical fiber.

[0019]

As described above, the conventional optical module assembly requires a number of alignment steps including the angle alignment, which is problematic in that it takes a long time.

Further, since the solder is fixed, the centered position is likely to vary between the high temperature state where the solder is melted and the temperature after cooling. Therefore, there are problems that the yield is low and the productivity is low. Furthermore, since resin must be used to fix the optical fiber and capillary, and the capillary and lens,
This resin is easily deteriorated by the heat when the solder melts. This may cause a problem in long-term reliability of the optical module. In addition, in order to fix the solder, it is necessary to perform special treatment such as covering the capillary holder with a metal tube and gold-plating the outer surface, the lens, the inner surface of the sleeve, etc.In addition, hole processing for pouring the solder into the sleeve And so on.

Further, since the two collimators have to be inclined and fixed to each other, there is a problem that the entire size becomes large and a large space is required inside.

An object of the present invention is to solve such problems and provide an optical module which is easy to assemble, has high productivity, and is small in size.

[0023]

In the optical module of the present invention, the light emitted from the first optical fiber is converted into parallel light by the first lens, and the parallel light is made incident on the optical functional element to perform the optical function. It has an optical system in which the light transmitted through the element is condensed by the second lens and is incident on the second optical fiber, and the optical axes of the first lens and the second lens substantially coincide with each other,
The optical axis of the first optical fiber tip facing the first lens and the optical axis of the second optical fiber tip facing the second lens are substantially parallel to each other, and substantially parallel to the optical axis of the lens. It is a feature.

Further, in the above optical module, the light reflected from the optical functional element is condensed by the first lens and is incident on the third optical fiber having an optical axis parallel to the first optical fiber and separated by a predetermined distance. The configuration may be included. With the above features, the optical module can be easily assembled and the module can be downsized.

In these optical modules, the distance between the center of the light emitting surface of the first lens and the center of the light incident surface of the second lens facing the center is 1 mm or less, preferably 0.5 mm.
Is preferred. Under this condition, the characteristics of the optical module having the above-described configuration of the present invention are most exerted.

Here, it is desirable that the two lenses have a lens length longer than the lens diameter and that the outer peripheral surface is cylindrical, and that the central axis of the cylindrical outer peripheral surface and the optical axis of the lens are parallel to each other. Is. As such a lens, it is preferable to use a gradient index rod lens in which the refractive index is distributed in the radial direction of the circular cross section perpendicular to the optical axis.

The means for fixing the first lens and the second lens by making their optical axes substantially coincide with each other is preferably a cylindrical tubular member or a groove member having a V-shaped cross section. Since the outer peripheral surface of the lens is cylindrical, the lens can be easily fixed at a predetermined position with a member having a simple structure such as a cylindrical tube or a V groove.

The first and third optical fibers are 2
It is desirable that the tip ends of the two optical fibers be fixed and supported substantially parallel to each other by a cylindrical capillary into which the optical fiber can be inserted. As a result, the relative positional relationship between the first and third optical fibers is fixed, and the alignment work can be facilitated.

In the above optical module, the optical axes of the first lens and the second lens are substantially aligned with each other, and the optical functional element is fixed at a predetermined position between the two lenses. The distance between the center of the light exit surface and the center of the light entrance surface of the second lens facing the light exit surface is fixed to a predetermined value.

Thereafter, light of a predetermined wavelength that passes through the optical functional element is made incident from the first optical fiber arranged parallel to the optical axis of the lens, and the first optical fiber and the first lens or the second light is made incident. At least one of the relative positions of the fiber and the second lens is adjusted so that the amount of light incident on the second optical fiber becomes larger than a predetermined value. However, this adjustment is performed by moving the relative position between each lens and the optical fiber only in the optical axis direction of the lens and in two directions perpendicular thereto. After the above adjustment is completed, it is possible to assemble by fixing the entire optical system while maintaining that state.

The light reflected by the optical functional element is condensed by the first lens and is incident on the third optical fiber having an optical axis parallel to the optical axis of the first optical fiber and separated by a predetermined distance. Also in the case of an optical module having an optical system for making it possible, first, the first lens, the second lens, and the optical function element are fixed in the same manner as above.

After that, from the first optical fiber arranged in parallel with the optical axis of the lens, light of a predetermined wavelength reflected by the optical functional element and light of a predetermined wavelength to be transmitted are respectively incident or superposed. Then, the relative position of the first optical fiber and the first lens is adjusted so that the amount of light incident on the third optical fiber becomes larger than a predetermined value.
Similar to the above, this adjustment is performed by moving the relative position of the lens and the optical fiber only in the optical axis direction of the lens and two directions perpendicular thereto.

Next, the relative positions of the second optical fiber and the second lens are adjusted so that the amount of light incident on the second optical fiber becomes larger than a predetermined value. The adjustment method is movement in the above three directions. After the above adjustment is completed, it is possible to assemble by fixing the entire optical system while maintaining that state.

In both of the above two cases, the centering performed by actually injecting light is only in the above three directions, and the angle centering of each element which has been conventionally required can be eliminated. Therefore, the number of times of centering is reduced as compared with the conventional method, and the others can be positioned by mechanical abutting, etc., so that the assembly is facilitated and the process can be performed in a short time. In addition, it is possible to fix with a resin, and there is an effect that the solder fixing step can be eliminated.

In any of the above assembling methods, the first,
It is desirable that the predetermined value of the second inter-lens distance is 1 mm or less.

[0036]

FIG. 1 shows an optical system which is the basis of an embodiment of the present invention. Light of wavelengths λ1 and λ2 is optical fiber 1
It exits from 5 and enters the first convex lens 25. At this time, the optical axis of the optical fiber 15 is made parallel to the optical axis of the lens, and its light emitting end face is placed on the focal plane of the lens 25 (the distance between the light emitting end face of the optical fiber 15 and the main surface of the lens 25 Equal to the focal length f. As a result, the light emitted from the optical fiber 15 is converted into parallel light by the lens 25.

The parallel light emitted from the lens 25 enters the demultiplexing filter 50 arranged on the focal plane on the side opposite to the optical fiber 15 (position at a distance f from the main surface of the lens 25). This filter 50 reflects light of wavelength λ1 and
It is designed to transmit two lights. The light of λ1 reflected by the filter 50 is condensed again by the lens 25 and enters the optical fiber 17. The optical axis of the optical fiber 17 is also made parallel to the optical axis of the lens, and the light incident end face thereof is placed on the focal plane of the lens 25.

On the other hand, the light transmitted through the filter 50 is condensed by the second convex lens 26 arranged so that its optical axis coincides with that of the lens 25, and is incident on the optical fiber 16. Second
The lens 26 has the same characteristics as the first lens 25, and is arranged so that the filter 50 is located on the focal plane of the lens 26. The optical fiber 16 is also arranged so that its optical axis is parallel to the optical axis of the lens, and its light incident end face is placed on the focal plane of the lens 26.

In the case of such an optical system, the cross section of the optical fiber has a finite diameter as described above (125 μm in the case of a normal single mode optical fiber), so at least one of the optical fibers 15 and 17 is It is placed away from the optical axis of the lens. FIG. 1 shows a case where the optical fibers 15 and 17 are placed symmetrically with respect to the optical axis C of the lens at a position of a distance Δ. In such a case, the first lens 25
The parallel light emitted from the lens is inclined with respect to the optical axis of the lens. For this reason, the shorter focal length of the lens is, of course, desirable for downsizing the optical system.

Although FIG. 1 shows geometrical optics, when a single mode optical fiber is used, it must be handled with a Gaussian beam. However, even in that case, the arrangement of the optical elements in FIG. 1 is basically unchanged.
The beam waist is formed at the position of the demultiplexing filter which is separated from the end faces of each optical fiber and both lenses by the focal length f.

FIG. 2 shows an optical system in which the lenses 25 and 26 of FIG. 1 are replaced with gradient index rod lenses 21 and 22. Light having wavelengths λ1 and λ2 is emitted from the optical fiber 11 and is incident on the gradient index rod lens 21.
The parallel light emitted from the lens 21 enters the demultiplexing filter 50. The filter 50 is designed to reflect light of wavelength λ1 and transmit light of wavelength λ2. Filter 50
The light of wavelength λ1 reflected by is condensed by the lens 21 and enters the optical fiber 13. On the other hand, the light of wavelength λ2 that has passed through the filter 50 is transmitted to the second gradient index rod lens 22.
The light is condensed by and is incident on the optical fiber 12.

Even when such a gradient index rod lens is used, the arrangement of each optical element is basically the same as in the case of FIG. However, the focal length of the gradient index rod lens is determined by the lens length Z. As described above, the meandering period (pitch) P of light rays in the lens is determined by the refractive index distribution, but the distance between the lens end surface and the focal position changes as the period of P when the lens length is changed. For example, Z = 0.
At 25P, the focal plane coincides with the position of the end surface of the lens.
If Z <0.25P, the focal plane is located outside the end surface of the lens.

If a lens having a lens length Z = 0.25P is used and the same arrangement as in FIG. 1 is taken, the optical fiber 1
The end faces of Nos. 1 and 13 are in contact with the end face of the first lens 21, and the end faces of the optical fiber 12 and the second lens 22 are also in contact with each other. Both lenses 21 and 22 are also arranged so that their end faces are in contact with each other. When an optical functional element having a finite size is inserted between the lenses, the ideal arrangement in which the lens end faces are in contact cannot be realized. In order to easily align the position of the optical fiber, the lens length is often set to be slightly shorter than 0.25P.

FIG. 3 is a schematic sectional view showing a first embodiment of a filter module by an optical system using the above gradient index rod lens. The same reference numerals are given to the optical elements corresponding to those in FIG. Here, the optical fiber has a cladding diameter of 1
A normal single mode optical fiber of 25 μm was used, and the lens used had an outer diameter of 1.8 mm, A ^1/2 = 0.323 mm ⁻¹ and a lens length = 0.23P.

The two-core capillary 31 is made of glass,
An optical fiber insertion hole having a rectangular cross section is provided so that the optical fibers of the book can be inserted close to each other. Therefore, the center-to-center distance of the core of the optical fiber is approximately 125 μm. When these two optical fibers are arranged so as to be substantially symmetrical with respect to the center of the lens and light is incident on the lens from one optical fiber, the light emitted from the lens is about 1.8 from the optical axis.
° tilt.

The filter 50 is formed directly on the lens 21 by SiO 2.
It was formed by alternately depositing a dielectric multilayer film made of a mixture containing ₂ and Ta ₂ O ₅ as main components. Membrane composition is λ
It was designed by setting 1 = 1480 nm and λ2 = 1550 nm.

A method of assembling this filter module will be described below. Assembling is performed in the following procedure. 1. The lens 21 is inserted so that the surface of the sleeve 60, which is made of a glass tube having an inner diameter larger than the outer diameter of the lens by about 10 μm, is the inner side, and the lens 22 is inserted from the other end. The distance between the filter surface and the end surface of the lens 22 is adjusted to a predetermined value, and the lenses 21 and 22 and the sleeve 60 are fixed with an adhesive.

2. 2 core glass capillary 3 in advance
The ends of the optical fibers 11 and 13 are inserted into the optical fiber 1, fixed with an adhesive, and the end faces are ground. 3. The position of the capillary 31 is set to x, y, z so that the light having the wavelength λ1 = 1480 nm is coupled to the optical fiber 11 and the reflected light from the filter 50 is sufficiently coupled to the optical fiber 13.
(Where the z direction is the optical axis direction of the lens, and the x and y directions are directions perpendicular to the optical axis and perpendicular to each other), and the end faces of the capillary 31 and the lens 21 are fixed by an adhesive material 92. However, here, the capillary 31 being aligned
Maintains its orientation parallel to the optical axis of the lens within a certain tolerance.

4.1 After inserting and fixing the tip of the optical fiber 12 into the capillary 32 made of glass, the end face is polished. 5. Wavelength λ transmitted from the optical fiber 11 through the filter 50
The light of 2 = 1550 nm is made incident, and the position of the capillary 32 is aligned in the x, y, and z directions so that the amount of light coupled to the optical fiber 12 becomes larger than a predetermined value, and fixed to the lens 22 with an adhesive 92. To do. Here again, the capillary 32 in alignment keeps its direction parallel to the optical axis of the lens within a certain tolerance.

6. The sleeve 60 is inserted into the cylindrical metal housing 70. 7. Resin 90 is filled in the housing 70 including the bonding portions of the capillaries 31, 32 and the lenses 21, 22 to fix the sleeve 60 and the housing 70.

Further, in the above-mentioned alignment method, a predetermined value is set and the amount of light to be combined is adjusted so as to be more than that. However, the method for adjusting the amount of light to the maximum is also available. Good.

The important points of this assembling method are summarized as follows. (1) The two lenses are previously fixed using a sleeve.
This allows the two lenses to be fixed such that their optical axes coincide with each other within a certain dimensional tolerance. (2) The first and third optical fibers 11 and 13 are fixed by a two-core capillary. As a result, the optical axes of the two optical fibers are kept parallel within a certain tolerance and the distance between the optical axes is also kept constant. Since the alignment is performed while maintaining this state, the two optical fibers are aligned not collectively but collectively. (3) The optical axes of the optical fibers 11, 12, and 13 are aligned in parallel with the optical axis of the lens within a certain tolerance.
In reality, the capillaries 31 and 32 are kept parallel to each other.

According to the above (1) to (3), the lens 21 and the capillary 31, and the lens 22 and the capillary 32 may be aligned only in the x, y and z directions. The angle alignment around each axis such as the inclination of both lenses with respect to the optical axis and the inclination of the optical axis of the lens and the optical fiber, which is conventionally required, becomes unnecessary. This makes it possible to significantly reduce the alignment work time.

The adhesive 92 has a refractive index of 1.46, and the lenses 21 and 22 are provided with a refractive index distribution coating on the optical fiber side so that reflection of light of wavelengths 1480 nm and 1550 nm is -40 dB or less. I went in advance. This eliminates the need for oblique processing of the lens and the end face of the optical fiber. However, as is conventional, a method of performing diagonal processing can also be applied to the embodiment of the present invention.

The characteristics of the filter module assembled as described above are shown below. The distance between the filter surface and the end surface of the lens 22 (hereinafter, referred to as interlens distance) was changed, and the loss of light incident on the optical fiber 12 was measured. The results are shown in Fig. 4. From the figure, it can be seen that the loss sharply increases when the inter-lens distance exceeds 1 mm, but when the distance between the lenses is 1 mm or less, the loss is sufficiently small as less than 1 dB.

The above results show that even if the light emitted from the lens 21 is emitted obliquely with respect to the central axis, it is taken in from the end face of the lens 22 which is close to the distance of 1 mm or less,
It is shown that light substantially parallel to the central axis can be extracted from a position near the center of the opposite end surface of the lens 22. From the above results, it is desirable that the distance between the end faces of the lenses 21 and 22 be 1 mm or less. This distance is preferably as short as possible, and more preferably 0.5 mm or less.

When the dielectric multilayer film is directly deposited on the end surface of the lens, the film thickness is generally several μm or less, and if the other lens is brought into close contact with the surface of the multilayer film, the inter-lens distance can be regarded as almost zero. And the loss can be made extremely small. However, the filter may not be provided directly on the end surface of the lens, but a dielectric multilayer film may be formed on another glass substrate or the like and inserted between the lenses. However, since the refractive index of glass and the like is larger than that of air, it is necessary to consider that amount.

In the first embodiment (FIG. 3), a demultiplexing filter is used as an optical functional element, and an optical module utilizing reflected light and transmitted light from this filter is illustrated. However, the present invention is not limited to this configuration and can be applied to an optical module in which various thin-layer optical function elements are inserted between collimators. For example, a certain wavelength or more as in the above embodiment, or a cut filter that transmits only light of the following wavelengths, a bandpass filter that transmits only a wavelength range of a certain range, or a constant transmittance over a wide wavelength range. A neutral density (ND) filter or the like may be used.

FIG. 5 shows an optical module using only transmitted light as a second embodiment. In this case, the capillary 33 on the incident side may also be a single core. In this case, the position of the optical fiber 11 for incident light is adjusted so as to be on the central axis of the lens 21, and the positional deviation is within ± 10 μm. The other assembly process is the same as that of the first embodiment. Thin-layer optical functional element 5
2 can use various filters and other elements having a function for transmitted light. As described above, in the thin-layer optical function element 52, it is desirable to form a thin film portion having a function directly on the lens end surface.

The third embodiment shown in FIG. 6 is functionally similar to the first and second embodiments, but it is easier to assemble. In this optical module, the optical fiber for incident light 1
The outer diameter of the capillary 34 supporting 1 is the same as the outer diameter of the lens 21. Although not specifically mentioned in the above embodiment, when adjusting the positional relationship between the lens and the optical fiber,
The outer diameter of the capillary is usually set to be smaller than the outer diameter of the lens, because it is not preferable for the adhesion to occur if the outer circumference of the capillary is outside the outer circumference of the lens.

However, on the side of the optical fiber 11 for incident light where the positioning is performed only by mechanical adjustment, the lens 21 and the capillary 34 having the same diameter can be positioned by inserting and fixing the lens 21 and the capillary 34 into the sleeve 60. Therefore, the position adjustment becomes easy in the three steps of the assembling steps described in the first embodiment. That is, it is possible to keep the optical axes of the capillaries and the lenses parallel to each other without using a special jig or the like. However, it is not necessary to set the positional accuracy of the optical fiber insertion hole of the capillary 34 to about ± 10 μm.

Although the gradient index rod lens is used as the lens in the above embodiments, a spherical lens or an aspherical lens as shown in FIG. 1 may be used as long as it is a converging lens. You can However, since the fixing is easy and highly accurate, the lens length is longer than the lens diameter,
It is desirable to have a cylindrically processed surface on the outer peripheral portion of the lens. In this case, the central axis of the outer peripheral cylinder and the optical axis of the lens need to be parallel.

As such a lens, for example, Casi
There is a C lens manufactured by x company. FIG. 7 shows a schematic sectional view of a filter module using this lens. Basically, it is a configuration in which only the lenses of the above embodiments of the filter module using the gradient index rod lens are replaced. The cylindrical convex lenses 27 and 28 are made of cylindrical homogeneous glass, and one end surface of which is spherically processed. The other end surface is a flat surface, but is usually obliquely processed to prevent reflection.

A glass tube was used as the sleeve. This is because it is desirable to be able to see through from the outside in order to adjust the distance between the end faces of the lens, and the coefficient of thermal expansion is close to that of the material of the lens. However, when both lenses and the optical functional element are used in contact with each other, they may be opaque and may be a metal or ceramic tube as long as there is no problem of difference in thermal expansion coefficient.

The means for fixing the axes of both lenses in alignment with each other is not limited to the sleeve (cylindrical) described above. Cross section is V
The objective can be achieved by arranging and fixing both lenses in a U-shaped, U-shaped or semicircular groove.

According to the above assembling procedure, when the two lenses are fixed, the optical axis shift between the two lenses due to the variation of the outer diameters of the lenses is not particularly corrected, and only the mechanical fixing is performed. . Further, since the number of times of alignment performed by using light is small, there is an effect that the assembly can be completed in a shorter time than the conventional method.

[0067]

Since the optical module of the present invention has few alignment points, the assembling time can be shortened. Further, since the optical axes of the two lenses can be made to coincide with each other, the optical module can be downsized.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic optical system of an optical module of the present invention.

FIG. 2 is an explanatory diagram of a basic optical system when a gradient index lens is used.

FIG. 3 is a cross-sectional view of the optical module according to the first embodiment of the present invention.

FIG. 4 is a diagram showing characteristics of the first embodiment.

FIG. 5 is a sectional view of an optical module according to a second embodiment of the present invention.

FIG. 6 is a sectional view of an optical module according to a third embodiment of the present invention.

FIG. 7 is a cross-sectional view of an optical module of the present invention using a cylindrical convex lens.

FIG. 8 is a cross-sectional view of a conventional filter module.

FIG. 9 is an explanatory diagram of an optical system of a collimator.

[Explanation of symbols]

11, 12, 13, 15, 16, 17, 111, 11
2,113 Optical fiber 21,22,121,122 Gradient index type rod lens 25,26,221,222 Convex lens 27,28 31,32,33,34,131,132 Capillary 50,150 Demultiplexing filter 52 Thin layer Optical functional element 60, 160 Sleeve 70, 170 Housing 90, 190 Resin 92 Adhesive 140, 142, 144 Holder 180 Solder 211, 213 Light source 212, 214 Image

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Minoru Taniyama             4-7 28 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture             Within Nippon Sheet Glass Co., Ltd. (72) Inventor Ikuto Oyama             4-7 28 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture             Within Nippon Sheet Glass Co., Ltd. F-term (reference) 2H037 AA01 BA32 CA10 CA16 DA04                       DA05 DA06 DA12 DA15 DA17                       DA36

Claims (11)

[Claims] 1. A light emitted from a first optical fiber is converted into parallel light by a first lens, the parallel light is made incident on an optical functional element, and the light transmitted through the optical functional element is converted into a second lens. In an optical module having an optical system for condensing light to be incident on a second optical fiber, a first light that has optical axes of the first lens and the second lens substantially coincide with each other and faces the first lens. An optical module in which the optical axis of the fiber and the optical axis of the second optical fiber facing the second lens are substantially parallel to each other and also to the optical axis of the lens. 2. The light reflected from the optical function element is converted into the first light.
2. The optical module according to claim 1, wherein the optical module collects the light by the lens of 1. and makes it incident on a third optical fiber having an optical axis parallel to the first optical fiber and separated by a predetermined distance. 3. The optical module according to claim 1, wherein the distance between the center of the light exit surface of the first lens and the center of the light entrance surface of the second lens facing the center is 1 mm or less. 4. The first and second lenses have a lens length longer than a lens diameter and an outer peripheral surface having a cylindrical shape, and a central axis of the cylindrical outer peripheral surface and an optical axis of the lens are parallel to each other. The optical module according to claim 1, 2, or 3. 5. The refractive index distribution type rod lens in which the first and second lenses have a refractive index distributed in a radial direction of a circular cross section perpendicular to the optical axis. 3. The optical module according to item 3. 6. The optical module according to claim 1, 2 or 3, wherein the means for fixing the optical axes of the first lens and the second lens by making them substantially coincide with each other is a cylindrical tubular member. . 7. A groove member having a V-shaped cross section as a means for fixing the optical axes of the first lens and the second lens so that they are substantially aligned with each other. Optical module described in. 8. An outer diameter of a capillary supporting at least one tip of the first or second optical fiber is substantially equal to an outer diameter of a lens.
Optical module described in. 9. The light emitted from the first optical fiber is converted into parallel light by the first lens, the parallel light is made incident on the optical functional element, and the light transmitted through the optical functional element is converted into the second lens. In the method for assembling an optical module having an optical system that collects light by using the optical system and makes it enter the second optical fiber,
The optical axes of the lenses are substantially aligned with each other, the optical functional element is fixed at a predetermined position between the first and second lenses, and the second optical element faces the center of the light emitting surface of the first lens. After the step of fixing the distance from the center of the light incident surface of the lens to a predetermined value, a predetermined optical fiber that is transmitted through the optical functional element from the first optical fiber arranged parallel to the optical axis of the lens is The first optical fiber and the first optical fiber
Or at least one of the relative positions of the second optical fiber and the second lens is arranged parallel to the optical axis of the lens in the optical axis direction of the lens and two directions perpendicular to the optical axis. A method of assembling an optical module, comprising: a step of adjusting an amount of light incident on an optical fiber to be larger than a predetermined value; and a step of fixing the entire optical system while maintaining the adjusted state. 10. The light emitted from the first optical fiber is first
Lens converts the parallel light into an optical functional element, and the light reflected by the optical functional element is condensed by the first lens to be parallel to the optical axis of the first optical fiber. Has an optical system for making the light incident on a third optical fiber having an optical axis separated by a predetermined distance, and for collecting the light transmitted through the optical functional element by a second lens and making the light incident on the second optical fiber. In the method of assembling an optical module, the optical axes of the first lens and the second lens are substantially aligned with each other, the optical functional element is fixed at a predetermined position between the first and second lenses, and After the step of fixing the distance between the center of the light exit surface of the first lens and the center of the light entrance surface of the second lens to a predetermined value, the first lens is placed parallel to the optical axis of the lens. A predetermined optical fiber which is reflected by the optical functional element from one optical fiber Long light and light having a predetermined wavelength that passes through the optical functional element are made incident respectively or in a superimposed manner, and the relative position of the first optical fiber and the first lens is set to the optical axis direction of the lens and the light. Adjusting the amount of light incident on the third optical fiber to be larger than a predetermined value in two directions perpendicular to the axis, and the second optical fiber and the second lens arranged parallel to the optical axis of the lens. The relative position of the lens in the optical axis direction of the lens and two directions perpendicular to the optical axis so that the amount of light incident on the second optical fiber becomes larger than a predetermined value; and And a step of fixing the entire system. 11. The predetermined value of the distance between the center of the light exit surface of the first lens and the center of the light entrance surface of the second lens facing the center is 1 mm or less. 10. The method for assembling the optical module according to item 10.