JP2000323778A - Light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting device which can realize higher airtightness while the alignment between a semiconductor optical amplifier and an optical fiber is secured. SOLUTION: A light emitting device 1 is provided with a fiber grating 14 having first and second end sections 14a and 14b, a semiconductor optical amplifier 16 which has a light emitting surface 16a optically coupled with the first end section 14a of the grating 14 and a light reflecting surface 16b and emits light when carriers are injected into the amplifier 16, and a housing 12 which has a window 38a through which the light from the second end section 14b of the grating 14 can be transmitted and airtightly houses the grating 14 and amplifier 16. Since the amplifier 16 is airtightly sealed in the house 12, the service life of the amplifier 16 is prolonged and the characteristics of the laser light source of the device 1 are not deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device including an optical component having a diffraction grating and a semiconductor optical amplifier.

[0002]

2. Description of the Related Art An optical module includes a semiconductor optical amplifier, an optical fiber having one end optically coupled to the semiconductor optical amplifier and having a diffraction grating formed in a core portion thereof, and a butterfly type housing for accommodating them. The optical fiber is drawn from a butterfly type package. Light generated in the semiconductor optical amplifier is extracted through an optical fiber.

[0003]

The inventor has been studying to develop an optical module having a longer life.

In such an optical module, a butterfly type package is typically used. Therefore, we examined this package.

[0005] In the optical module, in order to further improve the reliability of semiconductor elements such as a semiconductor optical amplifier housed in a package, these semiconductor elements are assembled so as to be placed in an airtight space. In the above optical module, if the manufacturing process is carefully observed, achieving higher airtightness and ensuring alignment between the semiconductor optical amplifier and the optical fiber have incompatible surfaces. Was found. That is, it is not always easy to assemble so as to improve the alignment accuracy between the two in order to achieve higher airtightness than at present.

Accordingly, an object of the present invention is to provide a light emitting device capable of achieving higher airtightness while ensuring alignment between a semiconductor optical amplifier and an optical fiber.

[0007]

As a result of further study, it has been found that, in the structure of the above-mentioned optical module, the optical fiber is sufficiently fixed at a portion taken out of the package in order to achieve higher airtightness. It is anticipated that there is a possibility that alignment accuracy higher than the current one may not be achieved.

That is, in the structure of the above optical module,
There is a trade-off between airtightness and alignment accuracy. Then, the structure of the light emitting device in which the airtightness and the positioning accuracy can be independently adjusted was examined. Therefore, the present invention has the following configuration.

A light emitting device according to the present invention includes an optical component, a semiconductor optical amplifier, and a housing. The optical component has a diffraction grating provided on an optical waveguide having a first end and a second end. A semiconductor light amplifier, a light emitting surface optically coupled to the first end of the optical component;
A light reflecting surface, and generates light when carriers are injected. The housing has a window through which light from the second end of the optical component can be transmitted, and houses the optical component and the semiconductor optical amplifier in an airtight manner.

In the light emitting device according to the present invention, the first end of the optical component can face the light emitting surface. Also, the window of the housing can face the second end of the optical component. Further, the diffraction grating and the light reflecting surface can form an optical resonator. The optical components and the semiconductor optical amplifier are designed such that optical coupling is achieved.
Each can be supported by a support member.

The optical component and the semiconductor optical amplifier are both
It is stored in the housing. The light generated by the semiconductor optical amplifier is taken out of the housing through the window of the housing, so that the semiconductor optical amplifier does not directly contact the air outside the housing. For this reason, the semiconductor optical amplifier can be arranged in an airtightly maintained space while maintaining the optical coupling relationship between the optical component and the semiconductor optical amplifier, and the life thereof can be extended.

In the light emitting device according to the present invention, the optical component has a first end and a second end, and a diffraction grating provided between the first end and the second end. A fiber grating can be included.

[0013] The light emitting device according to the present invention may further comprise an optical fiber having a third end optically coupled to the second end of the optical component through a window of the housing. To achieve such an optical coupling, the second end of the optical component can face the third end of the optical fiber. Further, the light emitting device according to the present invention can further include an optical isolator provided between the optical fiber and the optical component. To achieve such an arrangement, the second end face of the optical component and the third end face of the optical fiber can each face the optical isolator.

[0014] The second end of the optical component and the third end of the optical fiber may each have a lensed end. Further, the window of the housing may include a lens capable of collecting light from the second end of the optical component to the third end of the optical fiber. With such a lens, the optical coupling between the optical fiber and the optical component can be enhanced.

If an optical isolator is provided, it is possible to reduce return light which causes deterioration of laser oscillation characteristics.
Further, since the optical isolator can be provided between the optical fiber and the optical component, a bulk type isolator can be adopted.

In the light emitting device according to the present invention, the optical component includes an optical waveguide such as an optical fiber having a polarization maintaining function, and a diffraction grating provided in the optical waveguide, and the optical isolator is a polarization dependent type isolator. There can be.

If the diffraction grating is provided on the polarization maintaining fiber,
The polarization of the laser oscillation mode can be defined in one direction. For this reason, the optical isolator does not need to use a polarization-independent isolator that can block light in all polarization directions, and a polarization-dependent optical isolator that is provided to correspond to the polarization direction of the mode in which the laser is oscillating. An isolator can be adopted.

[0018]

Embodiments of the present invention will be described with reference to the drawings. The same or similar parts are denoted by the same reference numerals, and redundant description will be omitted.

A light emitting module according to an embodiment of the present invention will be described with reference to FIGS. This light emitting device has a configuration of a laser module. FIG. 1 is a perspective view of the laser module, which is partially cut away so that the state inside the laser module becomes clear. FIG. 2 is a cross-sectional view taken along the line II of FIG. 1 showing a main part of the laser module.

Referring to FIG. 1, a laser module 1
Includes a laser module main part 10 and a housing 12. The housing 12 is a butterfly-type package in the embodiment shown in FIG. The laser module main part 10 is arranged on the bottom surface in the package 12. The laser module main part 10 is sealed in a package 12 in a state where an inert gas such as nitrogen gas is sealed. The housing 12 includes a main body 12a that houses the semiconductor laser module main part 10, a tubular part 12b that holds the optical fiber 48, and a plurality of lead pins 12c.

The main part 10 of the laser module includes an optical component 14, semiconductor optical elements 16 and 18, a mounting member 22,
24, 26 and a positioning mechanism 28.

The mounting members 22, 24, 26 mount the semiconductor optical elements 16, 18. The mounting member 22 mounts the semiconductor optical amplifier 16 of a semiconductor optical element, and the mounting member 28
Has a semiconductor light receiving element 18 as a semiconductor optical element. The mounting member 24 has mounting members 22 and 28 mounted thereon. The mounting member 24 is arranged on a thermoelectric cooler (thermoelectric cooler) 20. The thermoelectric cooler 20 is put to practical use, for example, as a temperature control element using the Peltier effect. Since the thermoelectric cooler 20 has the semiconductor optical amplifier 16 disposed on the mounting member 24,
The temperature of the semiconductor optical amplifier 16 can be controlled. For this reason, the material of the mounting member 24 is preferably a good thermal conductor such as aluminum nitride (AlN) used for a chip carrier.

The cylindrical portion 1 on the inner wall of the package body 12a
A window provided with a lens 38a is formed in a portion leading to 2b. The space between the lens 38a and the package 12 is hermetically sealed. For this reason, the airtightness in the package 12 is significantly improved as compared with the conventional case.

Referring to FIG. 2, the optical component 14 has two ends 14a, 14b and these ends 14a, 1a, 1b.
4b, a grating (diffraction grating) 14c provided in the optical waveguide. Such an optical component 14 can be an optical fiber, the optical fiber comprising germanium oxide and having a core having a predetermined refractive index;
There is a clad provided around the core and having a smaller refractive index than the core. The core portion of such an optical fiber is sensitive to ultraviolet light, and the core portion functions as a diffraction grating when a periodic change in refractive index is provided. The diffraction grating 14c has a reflection spectrum that reflects light in a predetermined wavelength band, and optically couples with a semiconductor optical amplifier 16 described later to form an optical resonator. In the present embodiment, the present invention will be described by exemplifying a fiber grating (an optical fiber having a diffraction grating in a core portion, hereinafter, also simply referred to as an optical fiber) as an optical component, but more generally, it is provided in an optical waveguide. The present invention can be applied to an optical component having a diffractive grating.

One end 14a of the optical fiber 14 has a lensed end. The lensed end has an outer shape formed so as to have a light collecting function, and is also referred to as a rounded end. The other end 14b has a surface facing the lens 38a, and this end surface is formed by polishing the end surface of the optical fiber 14, so that it is also called a polished surface.

The optical fiber 14 has a positioning mechanism 28
It is supported by such a support member. One end 14 a of the optical fiber 14 is aligned by an alignment mechanism 28 so as to be optically coupled to the semiconductor optical amplifier 16. The other end 14b of the optical fiber 14 is
It is positioned so as to face the lens 38a, and is held by the positioning mechanism 28. Therefore, the other end 14b of the optical fiber 14 is optically coupled to the lens 38a. With this arrangement, the light generated in the semiconductor optical amplifier 16 is extracted through the optical fiber 14 and the lens 38a to the outside of the package 12 that hermetically seals the light.

The cylindrical portion 12b of the package 12 has a through hole communicating with the main body 12a. In this through hole, the end of the optical fiber 48 from the semiconductor optical amplifier 16 (48 in FIG.
Light propagating towards a) passes. A lens holding member 40 for holding a lens (40a in FIG. 2) is provided at a tip portion of the cylindrical portion 12b. Lens holding member 40
An optical isolator 42 can be provided between and the cylindrical part 12b. The optical isolator 42 is an optical fiber 4
8 to block light in the opposite direction.

An optical fiber 48 is introduced into the tip of the cylindrical portion 12b. The optical fiber 48 is a ferrule 44
The tip is covered and protected by. The lens holding section 40 holds the sleeve 46. Optical fiber 4
8 faces the lens 40a.
Since 8a is formed by polishing the end face of the optical fiber 48, it is also called a polished surface.

When the ferrule 44 is inserted into the sleeve 46, it is optically positioned with respect to the package 12. That is, the optical fiber 48 is aligned with the semiconductor optical amplifier 16 via the lens 40a, the lens 38a, and the fiber grating 14. As a result, the semiconductor optical elements 16 and 18, the fiber grating 14, the lenses 38a and 40a, and the optical fiber 48 are arranged with predetermined accuracy in accordance with the optical axis 2.

Referring to FIG. 2, in the laser module main part 10, the mounting member 24 includes an element mounting part 24a and a fiber supporting part 24b. Fiber support 24b
Is provided so as to extend from one main surface of the element mounting portion 24a. The fiber support 24b has a guide hole for receiving the optical fiber 14. The end 14a of the optical fiber 14 supported by the alignment mechanism 28 is inserted into the guide hole. For this reason, the lensed end 14a
Faces the semiconductor optical amplifier 16, the light from the semiconductor optical amplifier 16 is introduced into the core of the optical fiber 14.
The position of the optical fiber 14 is adjusted by a positioning mechanism 28 so as to be optically coupled to the semiconductor optical amplifier 16.

The semiconductor optical amplifier 16 is mounted on the mounting member 22. The semiconductor optical amplifier 16 includes a light emitting surface 16.
a and a light reflecting surface 16b. The light reflectance of the light emitting surface 16a is lower than the light reflectance of the light reflecting surface 16b, and is low enough not to substantially reflect light. Therefore, the light emitting surface 16
Light extracted from a can reach the diffraction grating. Therefore, the light reflecting surface 16b and the diffraction grating can form an optical resonator. The light emitting surface 16a is a lensed end 1
Optically coupled to the optical fiber 14 through 4a.

Referring to FIG. 3, the semiconductor optical amplifier 16
Includes an active layer 50 in which light is generated and amplified by carrier injection. The active layer 50 has a light emitting surface 16a and a light reflecting surface 16b at each end. The light emitting surface 16a is connected to the first end surface 50 of the semiconductor optical amplifier 16.
a, and the light reflecting surface 16b is
Is provided on the second end face 50b. The active layer 50
It extends along a predetermined axis 64. On the first end face 50a,
It is preferable to provide an anti-reflection film to suppress light reflection. As a light reflection preventing film, for example, a dielectric film (SiN
Film). Further, if the angle formed between the predetermined axis 64 and the normal line of the first end face 50a is inclined to a predetermined value θ, the light reflectance can be further suppressed. On the other hand, it is preferable to provide a light reflecting film on the second end face 50b in order to increase the light reflectance. As the light reflection film, for example, there is a dielectric multilayer film.

The active layer 50 of the semiconductor optical amplifier 16 has, for example, a stacked structure of a double hetero structure of InGaAsP / InP. This structure is similar to the structure of a double heterostructure Fabry-Perot semiconductor laser chip except that it has a light-emitting surface with high transmittance. On one main surface of the n-type InP semiconductor substrate 51, an n-type InP clad portion 52,
An undoped InGaAsP active layer 42 and a p-type InP cladding 54 are provided. These parts 42, 5
Reference numerals 2 and 54 are formed in a band-like region extending along a predetermined axis 64. The mesa-shaped portions 42, 52, 54
It is sandwiched from both sides by the embedded portion 56. The buried portion 56 includes the mesa-shaped stripe portions 42, 52, 5
4 acts to confine the current. Stripe part 4
An insulating film 58 is formed on the second, 52, 54 and buried portions 56.
Is provided. An electrode 60 for a p-type semiconductor is provided on the insulating film 58, and an electrode 62 for an n-type semiconductor is provided on the back surface of the substrate 51. When a modulation signal is applied between the electrodes 60 and 62 of the semiconductor optical amplifier 16 via the lead pins 12c of the package 12, a modulated laser beam is emitted from the light emitting device of the present invention. To this end, the light emitting device can include a drive circuit for the semiconductor optical amplifier in the housing 12.

When such a structure is provided, the refractive index of the active layer 50 is controlled by the clad portions 53 and 54 and the buried portion 56.
Relatively larger than. This structure corresponds to the active layer 50.
Is optically confined in the active layer 50. The active layer 50 can have a laminated structure such as MQW employed in a semiconductor laser or the like according to the wavelength of the generated light, and can also separate the carrier confinement region and the light confinement region. it can.

Referring again to FIG. 2, the positioning mechanism 28 includes a ferrule 30, a first support member 32,
, And a third support member 36.

The first support member 32 is a washer having a contact surface in contact with the outer surface of the fiber support portion 24b of the mounting member 24, an opposing surface opposing this surface, and a hole penetrating from the contact surface to the opposing surface. is there. The ferrule 30 is inserted into the through hole. The optical fiber 14 is inserted into the ferrule 30 at one end thereof so as to appear at the end 14 a of the optical fiber 14. The ferrule 30 includes the first support member 3
It is fixed to 2. This fixing is performed by the first support member 32.
At the opening end of the through hole. In this state, the first support member 32 can be moved while the contact surface thereof is in contact with the outer surface of the fiber support portion 24b of the mounting member 24, so that the optical fiber 14 is aligned with the semiconductor optical amplifier 16. Can be. When this alignment is completed, the first
Is fixed to the mounting member 24. This fixing is performed on the outer peripheral portion of the first support member 32.

The second support member 34 includes the first support member 3
It is provided so as to be fixed to the ferrule 30 at a position separated by a predetermined length from 2. In order to secure a predetermined length, the third support member 36 is connected to the first support member 32.
And the second support member 34.

The third support member 36 has a tubular portion provided along the direction in which the ferrule 30 extends, and is arranged such that one end of the tubular portion contacts the first support member 32. The other end of the tubular portion is closed by a flat plate having a hole through which the ferrule 30 passes. The flat plate has a second support member 34 disposed on the outer surface thereof.
The third support member 36 is, for example, cup-shaped having a bottom surface having a hole into which the ferrule 30 can be inserted, and a cylindrical portion. The third support member 36 is fixed to the first support member 32 on the outer surface of the tubular portion.

The second support member 34 is a third support member 3
6 has a contact surface that contacts the outer surface, an opposing surface opposing the contact surface, and a hole penetrating from the contact surface to the opposing surface. The ferrule 30 is inserted into the through hole. Ferrule 30
Is fixed to the second support member 34. This fixing is performed at the opening end of the through hole of the second support member 34. In this state, the second support member 34 can move while the contact surface thereof is in contact with the outer surface of the bottom surface of the third support member 36, so that the optical fiber 14 is connected to the semiconductor optical amplifier 1.
The position can be adjusted while finely adjusting the position to 6. This fine adjustment is performed by utilizing the "lever principle" using the fixed position between the first support member 32 and the ferrule 30 as a fulcrum. When the fine adjustment is completed, the second support member 34 is fixed to the third support member 36. This fixing is performed at the outer peripheral portion of the second support member 34.

Ferrule 30, first to third support members 3
2, 34, 36 can be formed of stainless steel. Ferrule 30, first to third support members 3
The fixing of 2, 34, 36 can be performed at a plurality of positions using spot welding.

The first and second support members 32, 34
It can have a ring shape. Thus, when the outer shape of the member is circular, the symmetry as viewed from the center of the circle (the center of the optical fiber) can be increased. For this reason, if spot welding is performed at a plurality of positions having symmetry, distortion generated during fixing can be reduced. In addition, when spot welding is used, fixing at a plurality of positions can be performed at the same time, so that distortion generated during fixing can be further reduced.

As described above, the optical fiber 14 is supported only by the positioning mechanism 28 and does not come into contact with the package 12. Therefore, by using the positioning mechanism 28, the optical fiber 14 can be positioned with high accuracy to the semiconductor optical amplifier 16. That is, the optical coupling between the two is performed irrespective of the degree of achievement of the sealing of the package and the temporal change of the sealing. Therefore, the airtightness of the package is not affected by the optical alignment.

The semiconductor optical element 18 is a light receiving element such as a photodiode. The light receiving element 18 is mounted on the chip carrier 26. Chip carrier 2
Reference numeral 6 denotes a light receiving element 18 which is a light reflecting surface 1 of the semiconductor optical amplifier 16.
6b is arranged on the mounting member 24 so as to face 6b. The light receiving element 18 operates as a monitor element for monitoring the light emitting state of the semiconductor optical amplifier 16.

Referring to FIG. 4, a window is formed by using a hermetic glass 38b in place of the lens 38a to ensure the airtightness of the package. Hermetic glass 3
8 b is arranged so as to be inclined by a predetermined angle with respect to the optical axis of the light emitted from the second end 14 b of the optical fiber 14. Thereby, the hermetic glass 38
Light reflected on the surface b is prevented from returning to the optical fiber 14 again. The optical fiber 14 has a polished surface 1
The optical fiber 48 has a lensed end portion 48b instead of the polished surface 48a. The optical fibers 14, 48 are lensed ends 14d,
Since the lens 38b is provided, the lenses 38a and 40a become unnecessary. The other points are the same as those in FIG. 2, and the description thereof will be omitted. As described above, the present invention is based on the semiconductor optical amplifier 1 while ensuring airtightness by various methods.
A high-precision optical coupling is achieved between the waveguide 6 and the waveguide type diffraction grating.

Referring to FIG. 5, with respect to the laser module described with reference to FIGS. 1 and 2, a fiber grating 14, a semiconductor optical amplifier 16, a light receiving element 18, lenses 38a and 40a, an optical isolator 42, The optical coupling relationship of the fiber 48 is schematically shown. Along the optical axis 2, the light receiving element 18, the semiconductor optical amplifier 16, the fiber grating 14, the lens 38
a, optical isolator 42, lens 40a, optical fiber 4
8 are arranged in this order.

The semiconductor optical amplifier 16 has a light reflecting surface 16b facing the light receiving surface of the light receiving element 18 and a light emitting surface 16a.
Is disposed so as to face the lensed end portion 14a of the fiber grating 14. The polished surface 14b of the fiber grating 14 faces the lens 38a, and the polished surface 48a of the optical fiber 48 faces the lens 40a. The optical isolator 42 is disposed between the lens 38a and the lens 40a. The diffraction grating 14c and the light reflecting surface 16b of the semiconductor optical amplifier 16 constitute an optical resonator, and enable laser oscillation. The generated laser light is extracted through the optical fiber 48.

The operation of the light emitting device shown in FIG. 5 will be described. FIG. 5 shows propagating lights A to K. When carriers are injected into the semiconductor optical amplifier 16, light is generated. The light A is emitted from the light emitting surface 16a after being reflected by the light reflecting surface 16b or directly without being reflected by the light reflecting surface 16b. The light B transmitted through the light reflecting surface 16b reaches the light receiving surface of the light receiving element 18. Light A is
The light is introduced into the core of the fiber grating 14 from the lensed end 14a. The light propagating through the core is condensed at the lensed end 14a as light D reflected by the diffraction grating 14c having a predetermined reflection spectrum,
The light is again introduced into the semiconductor optical amplifier 16 via 6a. This is repeated to amplify the light. The diffraction grating 14c
The incident light is reflected and a part of the light E is transmitted. The light E transmitted through the diffraction grating 14c is
a. The light G passing through the lens 38a travels to the optical isolator 42. The light that has passed through the optical isolator 42 goes to the lens 40a. Also, the optical isolator 4
2 blocks the light K incident from the lens 40a side.
The light I transmitted through the lens 40a is introduced into the core from the polished surface 48a of the optical fiber 48 by the lens 40a. Light J propagating through the core of the optical fiber 48 is extracted out of the light emitting device 1.

The optical isolator 42 employed in the present invention is disposed between the lens 38a and the lens 40a. For this reason, a bulk-type optical isolator can be adopted, and it is not necessary to use an expensive fiber-type isolator unlike a conventional laser module using a fiber grating. For this reason, it is possible to provide a light-emitting device that is reduced in cost despite being a light-emitting device using the fiber grating 14.

If a fiber grating 14 having a diffraction grating formed on an optical fiber having a polarization maintaining function is used, the polarization direction of laser-oscillated light can be defined in one direction. Therefore, a polarization dependent type isolator can be used as the optical isolator 42. Therefore, the cost of the light emitting device can be further reduced.

[0050]

As described in detail above, the light emitting device according to the present invention comprises a housing having a window, a semiconductor optical amplifier, a first end optically coupled to the semiconductor optical amplifier, and a window. And a fiber grating having a second end coupled to the fiber grating.

Accordingly, there is provided a light emitting device capable of achieving higher airtightness while ensuring alignment between the semiconductor optical amplifier and the optical fiber.

[Brief description of the drawings]

FIG. 1 is a perspective view of a laser module, which is partially cut away so that the state inside the laser module becomes clear.

FIG. 2 is a cross-sectional view showing a main part of the laser module, taken along a line II in FIG. 1;

FIG. 3 is a perspective view of a semiconductor optical amplifier.

FIG. 4 is a cross-sectional view taken along line II of FIG. 1 showing another main part of the laser module;

FIG. 5 is a schematic diagram illustrating an optical coupling configuration of a light emitting device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Laser module, 10 ... Main part of laser module, 12 ... Housing, 14 ... Optical fiber, 16, 18
... Semiconductor optical elements, 22, 24, 26 ... Mounting members, 28
... Position alignment mechanism, 30 ... Ferrule, 32, 34,
36 ... first to third support members, 38a ... lens, 38b
... hermetic glass, 40 ... lens holding member, 40a
... Lens, 42 ... Optical isolator, 44 ... Ferrule,
46 ... Sleeve

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2H037 BA02 BA03 BA04 BA11 BA32 BA34 CA06 CA33 5F073 AB11 AB27 AB28 AB30 FA06 FA29 FA30

Claims (6)

[Claims] An optical component having a diffraction grating provided in an optical waveguide having a first end and a second end; and light optically coupled to the first end of the optical waveguide. A semiconductor optical amplifier having an emission surface and a light reflection surface and generating light when carriers are injected; and a window through which light from the second end of the optical waveguide can be transmitted; A light-emitting device comprising: a housing that hermetically accommodates components and the semiconductor optical amplifier. 2. The optical fiber of claim 2, further comprising: a third end optically coupled to the second end of the optical waveguide through a window of the housing. Light emitting device. 3. The light emitting device according to claim 3, further comprising an optical isolator provided between said optical fiber and said optical component. 4. The optical component includes an optical fiber having a core having a polarization maintaining function and a diffraction grating provided on the core, wherein the optical isolator is a polarization dependent isolator.
The light emitting device according to claim 3. 5. The window of the housing includes a lens capable of guiding light from the second end of the optical waveguide to the third end of the optical fiber.
Alternatively, the light emitting device according to claim 3. 6. The light emitting device according to claim 2, wherein the second end of the optical waveguide and the third end of the optical fiber each have a lensed end.