JP2001215447A - Fiber stub type optical device and optical module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent fiber stub type optical device which is compact and easy to align, does not deteriorate the characteristics of an isolator under the influence of an external magnetic field, and an optical module using the same. SOLUTION: Two through holes 3a, 3a divided by a groove 7 formed in a ferrule 3 made of a diamagnetic material are provided with optical fibers 5, 5, respectively, and one end of each optical fiber is placed in the groove 7. At the same time, one end of the optical fiber was optically connected to the other end of the optical fiber via the optical isolator 2 provided in the groove 7 to obtain a fiber stub type optical device S1 in which the groove 7 was covered with a diamagnetic material. A fiber stub type optical device S and an optical element 15 for receiving or emitting light for optical connection to the fiber stub type optical device S are provided on the substrate 14.
Were provided as optical modules M.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module suitably used for optical communication equipment, sensors and the like. In addition, this optical module has a built-in optical isolator that blocks reflected return light from outside the optical module.
The present invention relates to a fiber stub type optical device and an optical module using the same.

[0002]

2. Description of the Related Art A laser diode (hereinafter, also referred to as an LD) used as a light source for optical communication reflects an emitted light at a certain place, and when returning to an active layer of the LD again, the oscillation state is disturbed and the emission power varies. And a wavelength shift, etc., which deteriorates the signal.

In order to prevent such a problem of reflected return light, the LD is usually mounted in the same package as an optical isolator that transmits light only in one direction, and constitutes an LD module which is a kind of optical module. ing.

In particular, analog signals are liable to be degraded by the reflected return light, and the higher the density of the signal, the more likely the signal is to be affected by the reflected return light. Accordingly, optical isolators have become an essential component.

Hereinafter, a general operation of the optical isolator will be briefly described. As shown in FIG. 5, the optical isolator 2 is configured such that the Faraday rotator 20 is sandwiched between two polarizers 19A and 19B. In such a configuration, the forward light 22 is transmitted as it is, and the backward light 25 is blocked. The Faraday rotator 20 has a Faraday effect by applying a magnetic field from the outside, and a Faraday rotator 20 having a Faraday effect without an external magnetic field due to spontaneous magnetization. Shall not. Hereinafter, a magnetic field generated in a surrounding electronic device or the like and present in the environment is referred to as an unnecessary external magnetic field, and a magnetic field applied to obtain Faraday rotation is particularly referred to as a bias magnetic field.

Next, an example of a conventional LD module will be described. As shown in FIG. 11, the LD module J1
In the package 18, at least the LD 15, the lenses 6A and 6B, the optical isolator 2, and one end of the single mode optical fiber 4 are housed. In the drawing, reference numeral 16 denotes a photodiode (hereinafter, also referred to as PD) as a light receiving element, reference numeral 17 denotes a peltier cooler, and reference numeral 32 denotes a rubber boot for protecting the extra length of the optical fiber.

The light emitted from the LD 15 is transmitted to the lens 6A
Is collimated by the optical isolator 2 and passes through the lens 6
The light is condensed by B and is incident on the single mode fiber 4.
The whole is housed in a package 18 for shielding from an external environment. As the lenses 6A and 6B, a ball lens, a biconvex lens, an aspheric lens, a graded index lens (hereinafter referred to as a GRIN lens), or the like is used.

In such an optical module J1, since the optical isolator 2, the lenses 6A, 6B, etc. are aligned as independent components after being fixed separately to the holder, the number of components is large and adjustment is complicated. There was a problem that it became large.

As shown in FIG. 12, an optical device J2 in which an optical isolator is mounted on a fiber stub using a core-expanded fiber without using a lens has also been proposed in order to reduce the size of the entire optical module and facilitate alignment. (See Japanese Patent Application Laid-Open No. 10-68909).

Here, a core-expanded fiber 5 having an enlarged optical fiber core is used to improve the coupling of light, and the optical isolator 2 is inserted obliquely with respect to the optical axis to prevent reflection.

In the optical device J 2, an optical isolator 2 and a cylindrical magnet 26 surrounding the optical isolator 2 are arranged on a ferrule 3 held around a front sphere 9, and the whole is fixed in a sleeve 13. ing. Optical device J2
Then, since the ferrule 3 has high coaxial accuracy, no axial deviation occurs. Further, the module with the optical isolator can be assembled with the same man-hour as the module without the optical isolator, which is very simple. However, in this conventional example, it is unclear how the ferrule 3 is processed and how the optical isolator 2 and the magnet 26 are assembled and fixed.

The core enlarged fiber used in the optical device J2 is made by locally heating a general single mode optical fiber. The single-mode optical fiber is heated to diffuse the dopant such as Ge doped in the core, thereby widening the diffusion region of the dopant and reducing the relative refractive index difference.

If the core diameter is increased without changing the relative refractive index difference between the core and the clad of the optical fiber, the single mode condition is broken and a multimode is excited. In the case of a core-expanded fiber, due to diffusion of the dopant due to heat,
The enlargement of the core and the decrease in the relative refractive index difference occur simultaneously, and r × (D) ^1/2 is automatically kept constant. Here, r is the radius of the core of the optical fiber, D is the relative refractive index difference between the core and the cladding, r × (D) ^1/2 is an amount proportional to the normalized frequency, and if this is constant, the single mode condition is Will be kept.

FIG. 6 shows the characteristics of optical coupling using a core-expanded fiber. The horizontal axis shows the distance between the fibers (= the width of the groove formed in the enlarged core portion), and the vertical axis shows the coupling loss of light. w indicates each mode field diameter and corresponds to each curve. The wavelength of light is 1.31 generally used in optical communication.
μm, and the grooves (between the fibers) were filled with air (refractive index n = 1).

When the core having a mode field diameter of 10 μm is not enlarged, the distance between fibers is 50 μm and 3d.
B, but the mode field diameter is 4
In the case of 0 μm, even if the distance between the fibers is 800 μm, the loss is 1
It can be seen that it is less than dB, and that the coupling characteristics are clearly improved.

An ordinary ferromagnetic Faraday rotator requiring a bias magnetic field (a typical Bi-substituted garnet as a Faraday rotator in the infrared region) exhibits characteristics as shown in FIG. The horizontal axis represents the bias magnetic field intensity, and the vertical axis represents the Faraday rotation angle. In the case of a magnetic material, the Faraday rotation θ is proportional to the magnetization M and is expressed by θ = VML. Here, V is a material-specific numerical value called Verde constant, and L is the thickness of the material in the magnetization direction. The optical isolator is adjusted so that θ = 45 degrees. The ferromagnetic material has an area A in which the Faraday rotation is proportional to the bias magnetic field and an area B in which the saturation is constant regardless of the bias magnetic field. The proportional region A is used by applying a sufficient bias magnetic field to the saturation region B because the Faraday rotation changes due to a slight change in the bias magnetic field and the characteristics of the isolator deteriorate. For example, in FIG. 7, the applied magnetic field is 79,000 to 118,500 A / m for a saturation magnetic field strength of 63,200 A / m. Further, when the bias magnetic field becomes zero, the magnetization disappears, so that it is necessary to constantly apply the bias magnetic field, and it is always used together with the magnet.

On the other hand, a Faraday rotator having spontaneous magnetization exhibits characteristics as shown in FIG. Similar to FIG. 7, the horizontal axis represents the bias magnetic field intensity, and the vertical axis represents the Faraday rotation angle. As can be seen from FIG. 8, a magnet having spontaneous magnetization like a magnet exhibits hysteresis. Once magnetized, demagnetization does not occur unless a large reverse bias is applied in the reverse direction. Therefore, even if an unnecessary external magnetic field exists up to Hc, the characteristics do not deteriorate, and a magnet is not required.

Actually, in a form such as the optical device J2,
The outer diameter of the ferrule 3 is standardized to be 1.25 mm to 2.5 mm, and the whole must be formed minutely. Therefore, an optical isolator including a Faraday rotator having spontaneous magnetization does not require a magnet and is small. This is preferable.

[0019]

Generally, a Faraday rotator requiring a magnet applies a magnetic field larger than the saturation magnetic field strength as described above. The Faraday rotator itself does not have a coercive force (spontaneous magnetization), so the magnetic field decreases due to bias due to the presence of other unnecessary external magnetic fields, for example, a device that uses a large current, or the magnet deteriorates due to thermal history and saturates. This is because there is a possibility that the Faraday rotation becomes smaller due to a lower magnetic field intensity. It is known that the internal magnetic charge of a magnet decreases due to thermal history even at a temperature below the Curie point. This addresses degradation of the magnet itself and the effects of unnecessary external magnetic fields. On the other hand, a Faraday rotator having spontaneous magnetization has no problem even if an external magnetic field is applied within the range of the coercive force.

Since a magnetic field is always generated at a place where an electric current is present, the optical module is always placed in the magnetic field. By the way, in recent years, as the cost and size have been reduced, the use of resin packages has become more frequent and the magnetic shielding structure has become insufficient, and the distance between the optical isolator and other devices in the system has been reduced due to the overall size reduction. The influence of an unnecessary external magnetic field on the optical isolator tends to increase.

In order to eliminate the influence of the unnecessary external magnetic field as described above, those having a bias magnet need only be made larger in size. It becomes difficult.

A Faraday rotator having spontaneous magnetization has no problem if an external magnetic field is applied within the range of the coercive force. However, the Faraday rotator generally has a coercive force smaller than that of the bias magnetic field, and
It is only about 31600 A / m. For example, the material shown in FIG. 8 is magnetized at 316000 A / m. From FIG. 7, the coercive force is 9
Although it is about 4800 A / m, the coercive force also depends on the shape and dimensions at the time of magnetization, so that the coercive force that can be actually guaranteed is half to one of the coercive force required from the material characteristics.
/ 3 or less, and the material shown in FIG.
It is about 0 A / m. Accordingly, there is a risk that the characteristics may be degraded by a process of incorporating the optical isolator into the optical module or by an unnecessary external magnetic field during use as the optical module.

In particular, it is important to consider unnecessary external magnetic fields in a device in which minute members are combined, but there has been almost no mention of a magnetic circuit of an optical isolator for external magnetic fields.

In view of the above, the present invention provides a fiber stub type optical device having a built-in optical isolator which suppresses the influence of an unnecessary external magnetic field during a component assembling process and during operation, and an optical module using the same. Aim.

[0025]

In order to achieve the above object, a fiber stub type optical device according to the present invention comprises a ferrule having a through hole and a groove crossing the through hole, and the two through holes divided by the groove. An optical fiber is disposed in each of the holes, and a fiber stub type optical device in which one end of each optical fiber is optically connected to each other through an optical isolator disposed in the groove. At least the surface is formed of a diamagnetic material, and the polarization plane rotating part of the optical isolator is formed of a spontaneous magnetization type Faraday rotator.

Further, a through hole and a groove crossing the through hole are formed in the ferrule, and optical fibers are disposed in each of the two through holes divided by the groove, and one end of each optical fiber is connected to each other. A fiber stub type optical device that is optically connected via an optical isolator arranged in the groove,
The polarization plane rotator of the optical isolator is composed of a spontaneous magnetization type Faraday rotator, and the Faraday rotator is surrounded by a magnet. In particular, it is characterized in that the surface of the magnet is covered with a diamagnetic material.

In the optical module of the present invention, the above-mentioned fiber stub type optical device and an optical element for receiving or emitting light for optically connecting to the fiber stub type optical device are provided on a substrate. Shall consist of

The fiber stub type optical device of the present invention may be provided with a magnet in the groove and then covered with a member having a magnetic susceptibility χ <0.

This makes it possible to provide a compact configuration in which optical elements such as optical isolators are mounted in a fiber stub almost free of alignment, and an optical module that operates stably even in the presence of an unnecessary external magnetic field can be easily manufactured. Can be configured.

It is well known that a housing surrounding the periphery is formed of a material having a high magnetic permeability in order to reduce the influence of an external magnetic field, and the magnetic flux that enters the inside of the housing from the outside is reduced. However, if the optical isolator is surrounded by a housing having a high magnetic permeability, the magnetic circuit of the optical isolator itself may be affected and the characteristics may be degraded. Therefore, the above-described method generally known is inappropriate. Further, since the housing comes into contact with an external member, it must be made of a material that does not form a new magnetic circuit due to the contact. A material having a negative magnetic susceptibility has an effect of reducing the influence of an external magnetic field since the magnetic flux itself does not easily enter. Ferrules include those using stainless steel or the like and those using resin, but alumina (χ = −
An oxide such as 0.34) is suitable for eliminating the influence of unnecessary external magnetic fields.

In order to safely assure against the influence of unnecessary external magnetic fields, it is effective to provide a magnet for applying a compensation magnetic field. Since the spontaneous magnetization type Faraday rotator is used, the magnet only needs to cope with an assumed unnecessary external magnetic field. Therefore, it may be much smaller than the bias magnetic field for a normal Faraday rotator. That is, the coercive force 31600A
If the external magnetic field is guaranteed up to 63200 A / m for a garnet of / m, a guaranteed magnetic field of 31600 A / m is sufficient and a magnet much smaller than the conventional one is sufficient, so that there is no problem in downsizing.

[0032]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the drawings, the same members are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 1, a fiber stub type optical device S1 comprises a core expanded fiber (optical fiber) 5 having a mode field diameter of, for example, 20 μm or more in an diamagnetic alumina ferrule 3 at normal temperature. In order to optically connect to a transmission single mode fiber (not shown) having a smaller mode field diameter (for example, about 10 μm), a GI (graded index) fiber 8 for converting a mode field is housed at one end. Consisting of

Here, the core expanded fibers 5 and 5 are respectively inserted into the two through holes (through paths) 3 a divided by the grooves 7.
, And one end of each core enlarged fiber is projected into the groove 7. An optical isolator in which the side face of one end of each of the core-enlarged fibers is covered with a protective member 11 having a higher refractive index than the cladding part constituting each of the core-enlarged fibers, and one end of each of the core-enlarged fibers is disposed in the groove 7. 2 for optical connection. The reason why the mode field diameter is increased to 20 μm or more as described above is that, assuming the thinnest optical isolator as an optical element to be inserted between optical fibers (grooves), the groove width should be at least 150 to 150 μm.
This is because 200 μm is required, and a mode field diameter of 20 μm is required for joining with a loss of 1 dB or less.

In addition, at least one of the core expanded fibers accommodated in the through hole 3a is a transmission single mode fiber and a GI for converting the mode field diameter.
It is assumed that the fibers 8 are connected in tandem.

Before inserting the core-enlarged fiber 5 into the ferrule 3, a groove 7 which crosses the through-hole 3a is formed in advance, and then inserted and fixed in the through-hole 3a. The exposed portion (fiber side surface) in the groove 7 of the core-enlarged fiber 5 is protected by a protective member 11 having a higher refractive index than the clad portion of the core-enlarged fiber.
After covering with the protective member 11 at one end at the groove 7
The optical fiber isolator 2 is disposed in the groove 10 formed in the groove 7 by dividing the core enlarged fiber 5 provided with the optical fiber.

More specifically, for example, at a central portion of a ferrule 3 having a diameter of about 1.25 mm and a length of about 12 mm, a width of 1.degree. A groove 7 of about 5 mm is formed.

Next, the mode field diameter is, for example, 40 μm.
At m, the core enlarged fiber 5 whose mode field diameter does not change and the GI fiber 8 having a lens effect are fusion-spliced by electric discharge, and polished and adjusted so that the length of the GI fiber becomes 260 μm. The GI fiber has a length of 260
Expand a 10 μm beam to approximately 40 μm in μm.

Next, the fusion of the core enlarged fiber 5 and the GI fiber 8 is inserted through the through hole 3a, and fixed so that the end face of the GI fiber 8 and the rear end face 3c of the ferrule 3 coincide. Further, after cutting a portion of the core enlarged fiber 5 protruding from the distal end face 3b of the ferrule 3, the tip spherical portion 9 is formed by discharging or polishing. First, ferrule 3
In parallel with the groove 7 (at an angle of 2 degrees),
A groove 10 having a width of 800 μm and dividing the expanded core fiber 5 is formed.

Then, the polarizers 19A,
19B and the spontaneous magnetization type Faraday rotator 20 serving as a polarization plane rotating unit are integrally formed, and then the optical isolator 2 manufactured by cutting is installed.
A translucent adhesive 21 is provided between the light entrance / exit surfaces of A and 19B and one end of the core enlarged fiber 5. Finally, an alumina shielding plate 28 is joined.

The light that has entered from the front spherical portion 9 of the core-enlarged fiber 5A passes through the optical isolator 2 through the groove 10, propagates again in the core-enlarged fiber 5B, and is converged by the GI fiber 8 to a beam diameter of 10 μm. Emit. The fiber stub type optical device S1 is connected to a connector (not shown) having the same shape as the ferrule 3 on the rear end face 3c and having a ferrule holding a single mode optical fiber for transmission at the center.

As described above, at least the surface of which is formed of a diamagnetic material can provide a structure in which the lines of magnetic force do not easily enter. However, when the diamagnetic material is coated, the thickness is about 300 μm to 500 μm. I just need.

In this embodiment, a fiber stub type optical device and a light emitting element (LD) for optically connecting the same are used.
Although the description has been given of the optical module provided with the light emitting element, a light receiving element may be provided instead of the light emitting element, or the light emitting element, the light receiving element, and the fiber stub type optical device are arranged on the same substrate. Of course, it can also be applied to modules.

[0044]

EXAMPLES Specific examples will be described below.

Example 1 This will be described with reference to FIGS. 2 (a) to 2 (f). As shown in FIGS. 2A and 2B, the diameter is 1.25.
mm, the center of the alumina ferrule 3 having a length of 12 mm, at an angle of 2 degrees with respect to the end face of the alumina ferrule 3,
A groove 7 having a width of 1.5 mm was formed so as to cross the through hole 3a. In this process, a DISCO dicer blade SDC320R10MB01 was used.

Next, as shown in FIG. 2C, the expanded core fiber 5 having a mode field diameter of 40 μm and a straight core (no taper portion) and a GI fiber 8 having a lens effect are fusion-spliced by discharge. The GI fiber was polished and adjusted to have a length of 260 μm. GI
The fiber is 260 μm long and expands a 10 μm beam to approximately 40 μm.

Next, as shown in FIG. 2D, the core expanded fiber 5 and the GI fiber 8 are fused and
a, and fixed so that the end surface of the GI fiber 8 and the rear end surface 3c of the ferrule 3 coincide with each other. Further, after cutting the portion of the core enlarged fiber 5 protruding from the front end surface 3b of the ferrule 3, discharge or polishing is performed. The forward ball portion 9 was formed.

Further, as shown in FIG. 2 (e), the exposed portion (the exposed side surface of the optical fiber) in the groove 7 of the core enlarged fiber 5 is protected by an adhesive such as an epoxy-based UV-curable optical adhesive. The core-enlarged fiber 5 having a width of 800 μm and being covered with the member 11 and being parallel to the groove 7 (at an angle of 2 degrees) at the groove 7.
Was formed. Here, a dicer blade NBC-Z2050 made by DISCO was used.

Then, as shown in FIG. 2F, the optical isolator 2 formed by integrally molding the polarizers 19A and 19B and the spontaneous magnetization type Faraday rotator 20 in the groove 10 and then cutting the optical isolator 2 is installed. . Here, the core-enlarged fiber 5 was fixed with an ultraviolet-curing adhesive or a thermosetting adhesive 21 whose refractive index was matched. Furthermore, the shield plate 2 made of alumina
8 with an epoxy thermosetting adhesive, and ferrule 3
Was configured so that the outer circumference became smooth.

The optical isolator 2 comprises polarizers 19A, 19
B (thickness: 200 μm, refractive index: 1.51), spontaneous magnetization type Faraday rotator 20 (Magnetic Garnet XL22, Lucent, USA, thickness: 380 μm, refractive index: 2.356), and each light transmitting surface is anti-reflective. After forming the film, it is joined with an epoxy-based translucent adhesive. The optical isolator 2 is cut into a 300 μm square after collectively aligning and bonding large devices of 10 mm square or more. The thickness becomes 780 μm. Further, since a spontaneously magnetized garnet is used, no magnet is required.

In the fiber stub type optical device of the present invention, when the optical fiber is mounted on an LD module, the end face of the core-enlarged fiber on the LD side is formed as a front spherical portion 9 in order to prevent reflection and improve coupling efficiency at the same time. .

FIG. 9 shows the results of measuring the deterioration of characteristics when a reverse bias magnetic field is applied to the optical isolator. A magnetic field was applied for 5 to 10 seconds in parallel with the magnetization direction of the Faraday rotator, and the insertion loss was measured. Sample A1
A1 to A4 have the same structure as that of the first embodiment in which the optical isolator alone is used, and B1 to B4 have the same structure as the first embodiment in which the alumina ferrule is covered with the alumina shielding plate. Insertion loss from 0.15dB to 0.2d
B. Samples A1 to A4 have almost 31600A /
m, the insertion loss was increased to 40 dB or more. This indicates that the Faraday rotation was reversed by the reverse bias. On the other hand, an alumina ferrule,
Up to 3 out of 4 using alumina shield plate 474
There was no change up to 00 A / m or more. 1 for external magnetic field
An improvement in resistance of 5800 to 23700 A / m was observed.

Example 2 In the fiber stub type optical device of Example 1, after the optical isolator was provided, the magnet 26 for applying the compensation magnetic field was provided. A square recess of about 350 μm is formed so as to surround a 300 μm square isolator made of samarium cobalt. The thickness was 1 mm. Since a spontaneously magnetized Faraday rotator is used, the magnet only needs to have a magnetic field strength that cancels unnecessary external magnetic fields, and can be much smaller than a Faraday rotator that requires a normal bias magnetic field. Therefore, the ferrule can be built in the ferrule as in the present invention.

As in the first embodiment, the core-expanded fiber 5 and G
The I-fiber 8 is inserted into the through-hole 3 of the ferrule 3 in which the groove 7 having a width of 1.5 mm is formed at an angle of 2 degrees with respect to the end face of the ferrule 3 and the end face of the GI fiber 8 and the ferrule 3 Are fixed so that the rear end surfaces 3c thereof coincide with each other, and a groove 10 for dividing the core-enlarged fiber 5 is formed to have a width of 800 μm in the same manner as in Example 1 above.
A, 19B, and an optical isolator 2 in which the Faraday rotator 20 is integrated is installed and fixed in the groove 10 in the same manner as in Example 1, and then a samarium-cobalt square isolator of about 350 μm is formed so as to surround the 300 μm square isolator. A concave portion was formed, and a magnet 26 having a thickness of 1 mm was provided to configure a fiber stub type optical device S2. As in Example 1, to increase the coupling efficiency with the LD, the end of the expanded core fiber 5 was formed on the tip sphere 9 by discharging or polishing.

This fiber stub type optical device S2 has:
The rear end face 3c is connected to a connector (not shown) having the same shape as the ferrule 3 and having a ferrule holding a single-mode optical fiber for transmission at the center.

FIG. 10 shows the results obtained by measuring the deterioration of the characteristics when a reverse bias magnetic field is applied to the optical isolator as in the first embodiment. A magnetic field was applied for 5 to 10 seconds in parallel with the magnetization direction of the Faraday rotator, and the insertion loss was measured. Samples A1 to A4 are optical isolators alone, C1
C4 to C4 have the same structure as the second embodiment in which the compensating magnetic field magnet 26 made of samarium cobalt is provided on the alumina ferrule. The insertion loss was between 0.15 dB and 0.2 dB. Samples A1 to A4 all deteriorated at approximately 31600 A / m, and the insertion loss became 40 dB or more. This indicates that the Faraday rotation was reversed by the reverse bias. On the other hand, those using an alumina ferrule and a samarium-cobalt magnet are 71100A / m to 7900A.
There was no change up to 0 A / m or more. An improvement in the resistance to the external magnetic field was observed as compared with Example 1. Example 3 FIG. 7 shows an example in which an LD module M is configured using the fiber stub type optical device formed in Examples 1 and 2 above. A fiber stub type optical device S having an LD-side end face made into a spherical fiber was fixed to a V-shaped groove of a Si platform 14 as a substrate. By mounting the Si platform 14 on the Peltier cooler 17, the LD 1
5 was operated at a constant temperature and in a stable state. P
D16 monitors the light of the LD 15 to stabilize the light intensity. The sleeve 13 is externally fitted with a connector (not shown) for optical coupling. The whole is hermetically sealed in a package 18.

With the above configuration, the optical adjustment of the LD module is all completed only by aligning the LD 15 and the spherical fiber. Further, since all of the optical system is in the ferrule 3, the size can be reduced, and an LD module which is extremely stable against changes in the surrounding electromagnetic field can be provided.

[0058]

As described above, according to the fiber stub type optical device and the optical module of the present invention, the following remarkable effects can be obtained.

The fabrication of the fiber stub type optical device itself only requires adjustment of the connection between the GI fiber and the core-enlarged fiber, and the subsequent insertion of the optical isolator can be performed almost alignment-free. Furthermore, it is possible to assemble only the optical coupling system before inserting the optical isolator, and it is possible to greatly reduce the number of steps.

It is possible to prevent deterioration of characteristics due to unnecessary external magnetic field during assembly and operation as a device.

It is possible to provide an optical module that is small, easy to manufacture, inexpensive, has little change over time, and has high reliability.

Optical adjustment of the LD module is possible only by adjusting the position of the LD and the fiber stub type optical device.
An LD module that can be easily assembled can be provided.

[0063]

[Brief description of the drawings]

FIG. 1 is a sectional view schematically illustrating a fiber stub type optical device according to the present invention.

FIGS. 2A to 2F are cross-sectional views schematically illustrating a process for producing a fiber stub optical device according to the present invention.

FIG. 3 is a sectional view showing an embodiment of a fiber stub type optical device according to the present invention.

FIG. 4 is a cross-sectional view schematically illustrating an optical module according to the present invention.

FIG. 5 is a perspective view schematically illustrating the operation of the optical isolator.

FIG. 6 is a graph showing the relationship between the facing distance of the core-enlarged fiber and the diffraction loss.

FIG. 7 is a magnetic characteristic diagram of a ferromagnetic Faraday rotator requiring a bias magnetic field.

FIG. 8 is a magnetic characteristic diagram of a spontaneously magnetized Faraday rotator.

FIG. 9 is a diagram for explaining characteristic deterioration when a reverse bias magnetic field is applied to an optical isolator.

FIG. 10 is a diagram for explaining characteristic deterioration when a reverse bias magnetic field is applied to an optical isolator.

FIG. 11 is a partial cross-sectional view illustrating a conventional optical module.

FIG. 12 is a cross-sectional view illustrating a device in which an optical isolator is mounted on a conventional core-enlarged fiber.

[Explanation of symbols]

2: Optical isolator 3: Ferrule 3a: Through hole 4: Single mode fiber 5: Core expanded fiber (optical fiber) 6A, 6B, 6C: Lens 7, 10: Groove 8: GI (graded index) fiber 9: Top sphere 11: Protective member 13: Sleeve 14: Si platform (substrate) 15: LD (light emitting element) 16: PD (light receiving element) 17: Peltier cooler 18: Package 19A, 19B: Polarizer 20: Faraday rotator 21: Adhesive material 22: forward incident light 23: core 24: clad 25: reverse incident light 26: magnet 27: light absorbing member 28: shielding plate 32: rubber boot M: LD module (optical module) S1, S2, S3, S4 , S5, S6: Fiber stub type optical device

Claims (3)

[Claims] 1. A ferrule having a through hole and a groove crossing the through hole, an optical fiber disposed in each of the two through holes divided by the groove, and one end of each optical fiber being connected to each other. Is a fiber stub type optical device that is optically connected via an optical isolator disposed in the groove, wherein at least a surface of the groove is formed of a diamagnetic material, and a polarization plane of the optical isolator. A fiber stub type optical device, wherein the rotating unit is constituted by a spontaneous magnetization type Faraday rotator. 2. A through-hole and a groove crossing the through-hole are formed in the ferrule, and optical fibers are disposed in each of the two through-holes separated by the groove. Is a fiber stub type optical device that is optically connected via an optical isolator disposed in the groove, wherein the polarization plane rotation unit of the optical isolator is configured by a spontaneous magnetization type Faraday rotator. A fiber stub type optical device, wherein the Faraday rotator is surrounded by a magnet. 3. A fiber stub optical device according to claim 1, and an optical element for receiving or emitting light for optically connecting to the fiber stub optical device are provided on a substrate. Optical module.