JP2000269597A - Manufacture method of fiber grating optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an optical resonator by optically coupling an optical fiber which has a fiber grating FG with an optical amplifier. SOLUTION: An optical fiber 14 with a fiber grating 14a at the core is aligned relatively with a semiconductor optical amplifier 16 and a light transmitting plane 16a of the optical amplifier 16 with one end of the optical fiber 14, thus constituting a fiber grating optical module. For manufacturing this module, the optical amplifier 16 and the optical fiber 14 are disposed so that one end of the optical fiber 14 faces the transmitting plane 16a. A light of a prescribed wavelength is applied to the light transmitting plane 16a through one end 14b of the optical fiber 14, and a light at a prescribed wavelength reflected on a light reflection plane 16b of the amplifier 16 is extracted from the other end 14c of the fiber 14 to adjust the relative position of the fiber 14 to the amplifier 16, based on the intensity of this light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for manufacturing a fiber grating optical module.

[0002]

2. Description of the Related Art The prior art is disclosed in US Pat.
There is a light-emitting module described in Japanese Patent Application Publication No. 0-203. This publication relates to an optical module including an optical resonator including a light emitting element and an optical fiber on which a fiber grating is formed.

This light emitting module includes an optical resonator comprising a semiconductor optical amplifier that generates light when a current is applied, and an optical fiber having a fiber grating. To form the optical resonator, a semiconductor optical amplifier is fixed on a pedestal provided in a housing, and then a ferrule provided at a tip portion of an optical fiber is inserted into a washer and fixed, and then the washer is fixed. Is fixed to the housing to determine the position of the optical fiber with respect to the semiconductor optical amplifier. This positioning is performed under the condition that a current is applied to the semiconductor optical amplifier to cause laser oscillation in the above-described optical resonator in order to reliably perform optical coupling between the semiconductor optical amplifier and the tip of the optical fiber. Have been done.

[0004]

In producing a fiber grating optical module by applying such a method, the inventor has noticed the following facts. In order to cause laser oscillation in an optical resonator composed of a semiconductor optical amplifier and a fiber grating, it is necessary that at least one longitudinal mode exists in the reflection band of the fiber grating.

However, in a fiber grating semiconductor laser (hereinafter, referred to as FGL) module, an external resonance mirror (FG) is moved to find an optimum position when aligning a semiconductor optical amplifier with an optical fiber. Since the longitudinal mode wavelength changes according to the cavity length, in an external cavity laser such as FLG, the longitudinal mode wavelength changes depending on the position of the external cavity in the optical axis direction. That is, the longitudinal mode wavelength changes during alignment.

On the other hand, since the reflection wavelength of the FG does not change,
Due to the movement of the FG in the optical axis direction due to this alignment, the longitudinal mode may move within the reflection band of the FG or may deviate from the reflection band. For this reason, when the longitudinal mode interval of the fiber grating semiconductor laser is substantially equal to the reflection bandwidth of the fiber grating, the oscillation state of the FGL becomes unstable.

Therefore, when aligning an optical fiber having a fiber grating with respect to a semiconductor optical amplifier, a sufficient adjustment has been made to stabilize laser oscillation.
For example, for this adjustment, it is necessary to perform alignment while performing adjustments on items such as changing the temperature of the semiconductor optical amplifier and changing the value of the applied current. For this reason, a temperature adjusting device for assembly is required, and a time for stabilizing the temperature of the semiconductor optical amplifier is required.

An object of the present invention is to provide a manufacturing method for optically coupling an optical fiber having a fiber grating to a semiconductor optical amplifier to form an optical resonator in a fiber grating optical module.

[0009]

According to the present invention, there is provided a semiconductor optical amplifier having a light transmitting surface and a light reflecting surface, and an optical fiber having one end and a fiber grating provided at a predetermined distance from the one end. The invention relates to a method of manufacturing a fiber grating optical module which is aligned in a specific manner. This alignment makes it possible to optically couple the light transmitting surface of the semiconductor optical amplifier and one end of the optical fiber.
This method comprises the steps of: (a) arranging a semiconductor optical amplifier and an optical fiber such that one end of the optical fiber faces a light transmitting surface of the semiconductor optical amplifier; and (b) transmitting light of a predetermined wavelength to the semiconductor optical amplifier. (C) entering an optical fiber through one end of the optical fiber to the light transmitting surface of the optical fiber, and (c) detecting the semiconductor light based on the intensity of light of a predetermined wavelength reflected by the light reflecting surface of the semiconductor optical amplifier and extracted through the optical fiber. Aligning the amplifier and the optical fiber relative to each other.

As described above, after the semiconductor optical amplifier and the optical fiber are arranged such that one end of the optical fiber faces the light transmitting surface of the semiconductor optical amplifier, the light transmitting surface is transmitted from the one end surface of the optical fiber to the semiconductor optical amplifier. The light of a predetermined wavelength is introduced through the. The introduced light is reflected by the light reflecting surface of the semiconductor optical amplifier and is emitted from the light transmitting surface of the semiconductor optical amplifier. If this emitted light is extracted from the optical fiber through one end of the optical fiber, the intensity of the light extracted through the optical fiber changes according to the relative position between the semiconductor optical amplifier and the optical fiber. .

In the method for manufacturing a fiber grating optical module according to the present invention, the aligning step includes: (c1) a moving step of relatively moving the position of the optical fiber and the position of the semiconductor optical amplifier; and (c2) moving the optical fiber. Measuring the intensity of the light extracted therethrough.

As described above, since the optical fiber and the semiconductor optical amplifier are relatively moved and the light intensity extracted through the optical fiber is measured, the optical fiber and the semiconductor optical amplifier are connected stepwise. Can be aligned.

In the method for manufacturing a fiber grating optical module according to the present invention, the aligning step comprises: (c3) moving the optical fiber and the semiconductor optical amplifier relative to each other;
Measuring the light intensity extracted through the optical fiber can be included.

As described above, when the light intensity is measured while moving the relative position between the optical fiber and the semiconductor optical amplifier, the relative position and the optical coupling state are continuously monitored, and the optical fiber and the semiconductor optical amplifier are continuously monitored. It becomes possible to align the amplifier.

In the method for manufacturing a fiber grating optical module according to the present invention, the incident step may include (b1) a modulation step of modulating light of a predetermined wavelength applied to the light transmitting surface of the semiconductor optical amplifier. Also,
In the alignment step, (c4) the relative positions of the semiconductor optical amplifier and the optical fiber can be adjusted based on the modulation component of the light of a predetermined wavelength extracted through the optical fiber. The modulation component can be related to the modulation performed in the modulation step.

As described above, by modulating an optical signal of a predetermined wavelength applied to the light transmitting surface, the light of a predetermined wavelength reflected from the light reflecting surface of the semiconductor optical amplifier and extracted from the optical fiber through one end of the optical fiber is modulated. Light is also modulated. If the relative position between the semiconductor optical amplifier and the optical fiber is adjusted based on this modulation component, the SN ratio of the measured value is improved, and the accuracy of the alignment is improved.

In the method for manufacturing a fiber grating optical module according to the present invention, prior to the alignment step,
(d) The method may further include a light emitting step of causing the semiconductor optical amplifier to emit light.

As described above, if a current is applied to the semiconductor optical amplifier before the alignment step, the alignment step is performed while the semiconductor optical amplifier is emitting light. Therefore, the near-field image and the far-field image of the light emitted from the light transmitting surface are close to the actual operation state. Therefore, the semiconductor optical amplifier and the optical fiber which are placed in a state close to the actual operation are aligned.

According to the present invention, there is provided a fiber for relatively positioning a semiconductor optical amplifier having a light transmitting surface and a light reflecting surface, and an optical fiber having one end and a fiber grating provided at a predetermined distance from the one end. The present invention relates to a method for manufacturing a grating optical module. This manufacturing method includes: (e) arranging the semiconductor optical amplifier and the optical fiber such that one end of the optical fiber faces the light transmitting surface of the semiconductor optical amplifier; and (f) a predetermined step introduced into the optical fiber. (G) an incident step of applying light of a wavelength to the light transmitting surface of the semiconductor optical amplifier through one end of the optical fiber; and (g) a semiconductor optical amplifier based on a value of a photoinduced current generated by the light of a predetermined wavelength in the semiconductor optical amplifier. Aligning the amplifier and the optical fiber relative to each other.

After arranging the semiconductor optical amplifier and the optical fiber such that one end of the optical fiber faces the light transmitting surface of the semiconductor optical amplifier, light of a predetermined wavelength is applied from one end of the optical fiber to the semiconductor optical amplifier. Through the light transmitting surface. The introduced light generates a photo-induced current in the semiconductor optical amplifier. The value of the photo-induced current changes according to the relative position between the semiconductor optical amplifier and the optical fiber.

In the method for manufacturing a fiber grating optical module according to the present invention, the aligning step includes: (g1) a moving step of relatively moving the position of the optical fiber and the position of the semiconductor optical amplifier; and (g2) a photoinduced current. And a measuring step of measuring the intensity of

As described above, since the optical fiber and the semiconductor optical amplifier are relatively moved and the intensity of the photo-induced current extracted through the optical fiber is measured, the optical fiber and the semiconductor optical amplifier are connected to each other. It becomes possible to align them step by step.

In the method of manufacturing a fiber grating optical module according to the present invention, the aligning step includes the step of (g3) measuring a value of a photo-induced current while relatively moving the optical fiber and the semiconductor optical amplifier. be able to.

As described above, when the relative position of the optical fiber and the semiconductor optical amplifier is moved and the intensity of the photo-induced current is measured at the same time, the relative position and the optically coupled state are continuously monitored. The optical fiber and the semiconductor optical amplifier can be aligned.

In the method for manufacturing a fiber grating optical module according to the present invention, the incident step may include (f1) a modulation step of modulating light of a predetermined wavelength applied to the light transmitting surface of the semiconductor optical amplifier. In the aligning step, the relative position of the optical fiber with respect to the position of the semiconductor optical amplifier can be adjusted based on the modulation component of the photo-induced current. The modulation component can be related to the modulation in the modulation step.

As described above, when a modulated optical signal of a predetermined wavelength is applied to the light transmitting surface, the optical signal generates a photo-induced current in the semiconductor optical amplifier. If the relative position of the optical fiber with respect to the semiconductor optical amplifier is adjusted based on the modulated component of the value of the photo-induced current, the SN ratio of the measured value is improved, and the accuracy of the alignment is improved.

According to the above-described method for manufacturing a fiber grating optical module according to the present invention, in the incident step, a series of light including the first polarized light and the second polarized light is added to the light transmitting surface of the semiconductor optical amplifier. Can be. The use of light containing at least two polarizations reduces the possible dependence of the measured values on the polarization of the light. Further, according to the method of manufacturing a fiber grating optical module according to the present invention, in the incident step, a series of lights whose polarization planes are scrambled can be added to the light transmission plane of the semiconductor optical amplifier. This scrambling reduces the possible dependence of the measurement on the polarization of the light.

In the method for manufacturing a fiber grating optical module according to the present invention, the aligning step includes: (c5) a moving step of relatively moving a position of the optical fiber and a position of the semiconductor optical amplifier; and (c6) an optical fiber. Measuring the intensity of the light extracted via the time period over which the sequence of light is introduced.
The use of light containing at least two polarizations can reduce the dependence of the measured values on the polarization of light that can occur.

In the method for manufacturing a fiber grating optical module according to the present invention, the aligning step may be performed by (g
4) the position of the optical fiber, the movement step of relatively moving the position of the semiconductor optical amplifier, and (g5) a measurement step of measuring the photoinduced current over a period during which a series of light is introduced, it can.

If the light intensity is measured using at least one of a series of lights including at least two polarizations and a series of lights whose polarization planes are scrambled, the dependence of the light on the polarization which may occur during the measurement is reduced. You.

In the method for manufacturing the fiber grating optical module according to the present invention described above, (h) the fiber grating can reflect the longitudinal mode of the optical resonator formed by the light reflecting surface of the semiconductor optical amplifier and the fiber grating. The method may further comprise the step of tuning the light within the wavelength band of light.

By performing such an optical alignment, the laser is oscillated after the optical resonator is constituted by the fiber grating of the optical fiber and the light reflecting surface of the semiconductor optical amplifier. The vertical mode can be adjusted.

[0033]

Embodiments of the present invention will be described with reference to the drawings. When possible, the same parts are denoted by the same reference numerals, and description thereof will be omitted.

The configuration of a fiber grating optical module to which the present invention can be applied will be described with reference to FIGS. FIG. 1 is a perspective view of a fiber grating optical module, which is partially cut away so as to clarify the inside thereof. FIG. 2 is a sectional view showing a main part 10 of the fiber grating laser, taken along a line II in FIG.

Fiber grating optical module 1
Comprises a housing 12 and a main part 10 of the fiber grating optical module.

The housing 12 is a butterfly-type package in the embodiment shown in FIG. Package 12
The main part 10 of the fiber grating optical module is arranged on the bottom surface inside. The butterfly type package electrically connects a main body part 12a accommodating the main part 10 of the fiber grating laser module, a cylindrical part 12b for guiding the optical fiber 14 to the main part 10, and electrodes of the main part 10 outside the package 12. It is provided with a plurality of lead pins 12c that enable it to be taken out. An optical fiber 14 is introduced from the tip of the cylindrical portion 12b, and the optical fiber 14 passes through the inside of the cylindrical portion 12b and reaches the main portion 10 of the fiber grating laser module. The plurality of lead pins 12c are provided on both side surfaces of the package 12, and are electrically connected to the semiconductor optical amplifier 16 and the like by bonding using a conductive wire (not shown). Each lead pin 12c is connected to the semiconductor optical amplifier 16
It is used to supply a drive current to the light-receiving element 18, take out a current from the light receiving element 18 (for example, a photodiode), and supply a current to the thermoelectric cooler 28.

The main part 10 of the fiber grating optical module includes mounting members 22, 24, 26 for mounting the semiconductor optical elements 16, 18, and a positioning mechanism for optically coupling the optical fiber 14 to the semiconductor optical amplifier 16. And a unit 30. The positioning mechanism 30 includes a ferrule 32, a first support member 34, a second support member 36, and a third support member 38.

The mounting member 24 is an L-shaped member having a base portion 24a and a wall portion 24b. The wall portion 24b is provided on a mounting surface 24c of the base portion 24a. The chip carriers 22 and 26 are mounted on the mounting surface 24c of the base portion 24b.
Mounted on top. The mounting member 24 holds the Peltier device 2 with the installation surface 24d facing the Peltier device 28.
8 is installed. The wall portion 24b includes an optical fiber receiving surface 24e, an opposing surface 24f facing the receiving surface 24e,
24g of through holes penetrating from the receiving surface 24e to the facing surface 24f
And The lensed end 14b of the optical fiber 14 is inserted into the through hole 24g. In addition, 24g of through holes
Is that the end 14 b is the first end face 16 of the semiconductor optical amplifier 16.
Provide space for optically coupling with a. In the mounting member 24, the mounting surface 24c, the installation surface 24d, the receiving surface 2
4e and the opposing surface 24f are flat surfaces. Mounting surface 24c
And the installation surface 24d are substantially parallel, and the receiving surface 24e
And the opposing surface 24f are substantially parallel to each other.
Is substantially perpendicular to the facing surface 24f.

The first support member 34 includes a contact plane 34a that contacts the receiving surface 24e of the mounting member 24,
This is a washer having an opposing surface 34b opposing a. The first support member 34 moves from the contact plane 34a to the facing surface 34b.
Has a hole 34c penetrating toward. The first support member 34 used in the present embodiment has a shape in which a disk-shaped flat plate having a larger diameter and a disk-shaped flat plate having a smaller diameter are coaxially stacked. The first support member 34 supports the ferrule 32 inserted into the hole 34c provided at the center. The first support member 34 is provided with a hole 3 in the facing surface 34b.
The opening 4c is fixed to the ferrule 32, and the outer periphery of the first support member 34 is fixed to the mounting member 24.

The second support member 36 is a first support member 3
4 and is fixed to the ferrule 32 at a position separated by a predetermined length. To ensure a predetermined length, a third support member 38 is sandwiched between the first support member 34 and the second support member 36. The second support member 36 is a washer having a contact surface 36a that contacts the third support member 38 and an opposing surface 36b that opposes the contact surface 36a. The second support member 36 has a hole 36c penetrating from the contact plane 36a toward the facing surface 36b, and the ferrule 32 passes through the hole 36c. The second support member 34 used in the present embodiment is a flat plate and has a disk shape.

The third support member 38 has a tubular portion 38 a extending a predetermined length in the direction in which the ferrule 32 faces, and one end of the tubular portion 38 a is placed on the facing surface 34 b of the first support member 34. In contact. The other end of the tubular portion 38a has a flat plate portion 38b having a hole 38c through which the ferrule 32 passes.
Is closed by. The flat plate portion 38b has an outer surface,
It has a contact surface 38d with which the second support member 36 contacts.
The third support member used in the present embodiment has a bottom surface 38.
b has a cup shape having a cylindrical portion 38a having a through hole 38c at the center.

The second support member 36 is a third support member 3
The contact surface 38d of No. 8 is brought into contact with the plane 36a, and is fixed to the third support member 38 on the outer periphery of the second support member 36. Further, the second support member 36 is provided with a facing surface 36b.
Is fixed to the ferrule 32 at the outer periphery of the opening of the through hole 36c.

Ferrule 32, first to third support members 3
4, 36, 38 can be formed, for example, of stainless steel. Also, ferrule 32, first to third
The fixing of the supporting members 34, 36, 38 is preferably performed at a plurality of positions using, for example, spot welding.

The first pointing member 34 and the second pointing member 36 preferably have a ring shape. As described above, when the outer shape is circular, symmetry is increased in a planar shape viewed from the center axis direction of the circle. For this reason, when fixing is performed by spot welding at a plurality of symmetrical positions, for example, at two opposing points where the axis of symmetry and the outer periphery of the circle intersect, distortion caused by fixing is reduced. In addition, it is preferable that the fixing by spot welding be performed simultaneously with respect to the above-described facing position. By doing so, distortion generated at the time of fixing can be reduced.

The semiconductor optical amplifier 16 includes the chip carrier 2
2 mounted. The chip carrier 16 is formed using a material such as aluminum nitride (AlN) and alumina (Al ₂ O ₃ ). Therefore, heat generated during operation of the semiconductor optical amplifier 22 reaches the Peltier element 28 through the chip carrier 22. The Peltier element 28 operates as an electronic cooling element when a current flows. The semiconductor optical amplifier 16 is arranged with its first end face 16a facing the optical fiber insertion surface of the package 12. Although not particularly shown in the drawings, the electrodes formed on the semiconductor optical amplifier 16 are connected to the wiring layer on the chip carrier 22 via conductive wires. This wiring layer is connected to the internal lead of the package 12 by a conductive wire.

The semiconductor optical amplifier 16 is, for example, InGa
An active layer composed of AsP and this active layer
This is a light emitting element that has a cladding layer made of InP sandwiched on its surface on a semiconductor substrate, and injects carriers into the active layer from the cladding layers on both sides to form population inversion, thereby generating and amplifying stimulated emission light. One of the cladding layers is formed of a P-type semiconductor, and the other of the cladding layers is formed of an N-type semiconductor. Therefore, these cladding layers constitute a PN diode with the active layer sandwiched from both sides. The energy difference between the conduction band and the valence band of the active layer is Eg (band gap). When a carrier is injected, electrons and holes recombine to generate light having a wavelength related to Eg.

The active layer has a first end face 16a and a second end face 16b. At the oscillation wavelength of the light of the fiber grating optical module, the light reflectance of the first end face 16a is smaller than the light reflectance of the second end face. In order to realize this, a low reflection film is formed on the first end face 16a to achieve a reflectance of about 1 to 0.1%. On the other hand, a highly reflective film is formed on the second end face 16b,
A reflectance of 5% or more is achieved. Therefore, the first end surface 16a becomes a light transmitting surface, and the second end surface 16b becomes a light reflecting surface.

The active layer is an optical waveguide having a first end face 16a and a second end face 16b at both ends, and this optical waveguide is formed at a predetermined angle with each of the first end face 16a and the second end face 16b. It extends along intersecting waveguide axes.

Although not shown in the drawings, the electrodes provided on the semiconductor optical amplifier 16 are connected to the wiring layer on the chip carrier 22 by conductive wires. This wiring layer is connected to the internal lead of the package 12.

The optical fiber 14 has a fiber grating 14a and two ends 14b and 14c.
One of these ends faces the first end face 16a of the semiconductor optical amplifier 16, and the optical fiber 14 is disposed at a position where the end 14b and the first end face 16a can be optically coupled. I have. The end 14 b optically coupled to the first end face 16 a is connected to the first end face 16 of the semiconductor optical amplifier 16.
It has a lens shape that is processed to be spherical so that light emitted from a can be collected. Therefore, the semiconductor optical amplifier 1
Since there is no need to provide a separate lens between the optical fiber 6 and the optical fiber 14, the optical coupling can be performed directly. As a result, the resonator length can be shortened, so that the high-frequency characteristics of the fiber grating laser are improved.

The optical fiber 14 is provided with a diffraction grating (fiber grating) 14a at a position within a core portion separated from the one end portion 14b having a lens shape by a predetermined distance. An optical fiber suitable for forming such a diffraction grating 14a includes a core portion containing germanium oxide and having a predetermined refractive index, and a cladding provided around the core portion and having a smaller refractive index than the core portion. Unit. By irradiating the optical fiber with ultraviolet rays, regions having different refractive indexes are formed at a plurality of portions of the core portion. Such regions are preferably provided periodically. Such a diffraction grating 14a is characterized by characteristic values such as reflectance, period, diffraction grating length, and the like. The diffraction grating 14a can be designed to combine these characteristic values to have a reflection spectrum in a wavelength region different from the wavelength region used for alignment in the present application. The reflection spectrum of the diffraction grating 14a has a wavelength λ
A predetermined half value width is centered on g.

The optical fiber 14 is inserted from one end into a through hole extending from one end of the ferrule 32 to the other end thereof.
The tip 14b of the optical fiber projects from the other end of the ferrule 32 by a predetermined length. The ferrule 32 is fixed to the first support member 34 at a position separated by a predetermined distance from the end from which the tip end 14b of the optical fiber projects. The ferrule 32 is fixed to the second support member 36 at a position separated by a predetermined distance from one end into which the optical fiber 14 is inserted. The first support member 34 and the second support member 36 are arranged at positions spatially separated by the third support member 38. Third support member 38
Is a member that enables the second support member 36 to be arranged at a position separated from the first support member 34.

With reference to FIG. 3, the positioning mechanism 30 for optically coupling the optical fiber 14 to the semiconductor optical amplifier 16 will be described. FIG. 3 is a schematic diagram showing a state in which the mounting member 24 is fixed to a jig 40 used when assembling while aligning the alignment mechanism unit 30.

The mounting member 24 is fixed to an assembly jig 40. The mounting member 24 has a chip carrier 22 on which the semiconductor optical amplifier 12 is mounted on a mounting surface, and is already assembled up to a state where electrical connection is completed. In addition, the light receiving element 28 and the chip carrier 26 are omitted below, unless otherwise specified, in order to make the drawing easy to see. The assembling jig 40 is positioned in the three-dimensional space by the positioning mechanism 30.
Is provided with a moving mechanism 42 required to relatively position the mounting member 24 with respect to the mounting member 24. The translation mechanism 42 includes a translation mechanism 42a in the X-axis direction of the coordinate axes shown in FIG. 3, a translation mechanism 42b in the Y-direction toward the paper surface, a translation mechanism 42c in the Z-axis direction, and a Z-axis. And a rotation mechanism 42d for performing φ rotation around. In particular, although not shown,
Ferrule 32, first to third indicating members 34, 36, 3
A welding device is also provided as fixing means for fixing the mounting member 24 and the mounting member 24, respectively. This welding device is preferably, for example, a laser welding device using a YAG laser.

The positioning mechanism 30 is positioned on the receiving surface 24 e of the mounting member 24 fixed to the jig 40 while being roughly aligned with the optical axis 44 of the semiconductor optical amplifier 12.
The ferrule 32, the first support member 34, the third support member 38, and the second support member 36 are arranged in this order from below. First support member 34, second support member 3
In the sixth and third support members 38, the ferrules 32 with the optical fibers 14 are arranged so as to pass through holes provided in the central portions thereof.

Next, an optical coupling relationship used for alignment for aligning the optical fiber with respect to the semiconductor optical amplifier 16 will be described with reference to FIG. FIG. 3 is a schematic view showing a state where the mounting member is fixed to an assembly jig. The first end 14 b of the optical fiber 14 is arranged so as to face the light transmitting surface 16 a of the semiconductor optical amplifier 16. The second end 14c of the optical fiber 14 is optically coupled to a light generator (light source) 46. The light generator 46 supplies light of a predetermined wavelength from the second end 14c to the optical fiber 14 as monitor light.
The light having the predetermined wavelength can pass through the fiber grating 14a, and the light transmission surface 16a of the semiconductor optical amplifier 16
From the light transmitting surface 16a to the light reflecting surface 16b.
And can be reflected on the light reflecting surface 16b. Light of a predetermined wavelength is not substantially absorbed by the active layer. The light of such a predetermined wavelength is the optical transition energy of the active layer,
That is, the light has a wavelength longer than the wavelength of the light corresponding to the band gap energy.

The optical fiber 14 comprises an optical coupling means 52 between the fiber grating 14a and the second end 14c.
For example, it has an optical coupler (fused silica coupler, directional coupler). The optical coupling means 52 achieves an optical coupling with the optical fiber 14, preferably a relatively loose coupling, so that the optical fiber shunt 52a and the optical fiber main path (from the first end 14b to the second end 14b). 14c). A measuring device 54 capable of measuring light intensity (light power), for example, a power meter, is optically coupled to the third end 52b of the shunt 52a. Using this measuring device 54, the intensity of light that has traveled along the optical fiber 14 and has reached the end 52b can be measured. The power meter 54 can detect the intensity of light having a predetermined wavelength.

The light generator 46 can modulate the intensity of light, and the measuring device 54 can detect the modulated component of the optical signal modulated by the light generator 46. Such modulation may be performed such that the light intensity is changed at a predetermined frequency, and may be performed such that the light intensity is a predetermined binary code. As described above, if a modulated optical signal is input and a modulated signal associated with the modulation is detected, the SN ratio can be improved in the measurement of the optical signal in the present method. Therefore, the average power of the optical signal to be generated in the light generator 46 can be reduced. When the average power is reduced, heat generation on the light reflecting surface of the semiconductor optical amplifier 16 during measurement can be reduced. Further, it is possible to increase the light power at the time of light emission while reducing the average power, which contributes to the improvement of the SN ratio.

The second end 14c of the optical fiber 14
The present invention is similarly applicable if the power meter 54 is optically coupled to the optical fiber shunt 52a and the light generator 46 is optically coupled to the third end 52b of the optical fiber shunt 52a. Optical connection using an optical connector between at least one of the first end 14b and the second end 14c and at least one of the first end 14b and the third end 52b. ,
Optical coupling by fusion, optical merging and branching by an optical coupler, and the like can be included.

After assembling such an optical coupling, light of a predetermined wavelength generated in the light generator 46 can pass through the fiber grating 14a.
The light propagates through the optical fiber 14 and enters the active layer of the semiconductor optical amplifier 16 from the first end 14b via the light transmitting surface. This incident light propagates through the active layer, is reflected on the light reflecting surface, and is emitted from the light transmitting surface. The emitted light is introduced into the optical fiber 14 from the first end 14b and
Is propagated. When this light reaches the optical coupling means 52, a part thereof is branched to the optical fiber shunt 52a. The power meter 54 detects the intensity of the split light. The intensity of the split light reflects the strength of the optical coupling between the first end 14 b of the optical fiber 14 and the semiconductor optical amplifier 16. In other words, in such an optical connection mode, as the optical coupling between the semiconductor optical amplifier 16 and the optical fiber 14 becomes closer, a larger light intensity is gradually observed at the other end 52b of the optical fiber. Will be done. Therefore,
Based on the observed value, the degree of achievement of alignment between the optical fiber 14 and the semiconductor optical amplifier 16 can be determined.

The intensity of the light introduced from the light generator 46 is such that the light reflecting surface and the light transmitting surface of the semiconductor optical amplifier 16 are not destroyed.
The intensity is such that noise light and signal light are distinguished. Since the light generator 46 can modulate the emitted light,
If the modulated light is measured using the power meter 54, the measurement can be performed using a smaller optical power than the measurement using the DC light.

The wavelength of the light generated by the light generator 46 needs to be considered in the following two respects.

First, the light used for alignment needs to have a sufficiently small reflection on the light transmitting surface 16a of the semiconductor optical amplifier 16. That is, the intensity of light reflected by the light transmitting surface 16a and detected by the power meter 54 needs to be sufficiently smaller than the intensity of light reflected by the light reflecting surface 16b and detected by the power meter 54. Therefore, light having a wavelength such that the intensity of light reflected on the light transmitting surface 16a cannot be ignored compared with the intensity of transmitted light is not suitable for the method in the present embodiment.

Next, the wavelength of the light generated in the light generator 46 is longer than the wavelength of the oscillating light in the fiber grating optical module. There is a particular interest in practical use for an optical module having a wavelength band of 1.55 μm of oscillation light. At this time, the wavelength of light to be generated by the light generation device (light source) 46 is longer than 1.55 μm. . Some semiconductor lasers in such a wavelength range have already been put to practical use. The light supplied from the light generator 46 is preferably a laser light as a light source having a high optical power.

The axis (waveguide axis) direction in which the active layer of the semiconductor optical amplifier 16 extends does not necessarily need to intersect the light transmission surface 16a and the light reflection surface 16b substantially perpendicularly. The light reflected by the light reflecting surface 16b is applied to the first end 1
4b is introduced into the optical fiber 14, and the power meter 54
It is important to be observed at To this end, the present method can be applied if it is observed that about several percent of the light intensity generated by the light generating device 46 and applied to the optical fiber 14 is observed.

The method described with reference to FIG.
A further preferable alignment method is provided by partially modifying the configuration shown in FIG. FIG. 7 is a schematic view showing a state in which the mounting member is fixed to an assembly jig. Referring to FIG. 7, an optical isolator 58, an optical bandpass filter 56, and a power supply 60 are added to the configuration shown in FIG. The optical isolator 58 is disposed between the light source 46 and the optical coupler 52, and
Only the light directed to 2 is passed. The optical bandpass filter 56 is disposed between the power meter 54 and the optical coupler 52, and has a transmission spectrum that transmits the wavelength of light generated by the light source 46. Therefore, in the power meter 54, light emitted from the light source 46, reflected on the light reflection surface 16b of the semiconductor optical amplifier 16, and further wavelength-selected by the optical bandpass filter 56 is selectively detected. The power supply 60 is connected to the semiconductor optical amplifier 16 via a wiring 62.

Prior to the alignment, a current is applied from the power supply 60 to the semiconductor optical amplifier 16. This current value is a predicted threshold current at which the optical module can perform laser oscillation, for example, 15 mA.
Preferably, the current is about 20 mA. Since the active layer to which such a current value is applied achieves a carrier density close to that actually used as an optical module, the refractive index of the active layer is also affected by the carriers, and the actual use is It is considered to be close to the state. For this reason, a light emission pattern (a so-called near-field image) near the light transmission surface 16a and a light emission pattern (a so-called far-field image) at a position further away from the light transmission surface 16a, for example, at a position of the distal end portion 14b of the optical fiber 14. Image) is closer to the actual operating state than when there is no current. Therefore, the optical fiber 14 and the semiconductor optical amplifier 16 are aligned under a state closer to the actual operation state.

When a current is applied to the semiconductor optical amplifier 16, the semiconductor optical amplifier 16 emits spontaneous emission light or fiber grating laser oscillation light. With these lights,
In order to distinguish the monitor light necessary for alignment, between the power meter 54 for detecting the monitor light and the optical coupler, the monitor light is transmitted but most of the spontaneous emission light and the fiber grating laser oscillation light are removed. An optical bandpass filter is required.

Subsequently, referring to FIGS. 4A, 4B, 5A and 5B, the positioning mechanism 30 is formed on the mounting member 24. The procedure will be described. FIGS. 4A to 5B are assembly cross-sectional views each taken along a line II in FIG. 1.

In FIGS. 4A to 5B, similarly to FIG. 3, the light receiving element 18 and the chip carrier 2 are provided.
6 is omitted. Although the assembly jig 40 and the moving mechanism 42 are not shown in FIGS. 4A to 5B, the mounting member 24 is required to be relatively positioned with the positioning mechanism 30 in the three-dimensional space. Used as needed. 4A to 5B, the semiconductor optical amplifier 16 is assembled to a state where it can operate when a voltage is applied to a predetermined electrode on the mounting member 24.

FIG. 4A shows a step of fixing the ferrule 32 into which the optical fiber 14 has been inserted and fixed to the first support member 34. The contact surface 34a of the first support member 34 is in contact with the receiving surface 24e of the mounting member 24 with the ferrule 32 inserted in the hole 34c.
The tip 14b of the optical fiber is connected to the first
Of the mounting member 24 so as to come to a predetermined position from the end surface 16a of the mounting member.
The optical fiber 14 is aligned with the light transmitting surface 16a of the semiconductor optical amplifier 16 in the Z-axis direction, that is, aligned in the Z direction. The alignment in the Z direction can be performed, for example, by setting the semiconductor optical amplifier 16 in a state where the semiconductor optical amplifier 16 emits light as in the conventional case,
The optical fiber 14 is moved in the Z direction based on the light emitted from the optical fiber 14, and the one end 14b of the optical fiber 14 and the semiconductor optical amplifier 16 are roughly aligned. Thereafter, the alignment can be performed more precisely by using the method described in the embodiment, that is, by causing the light generator 46 to emit light. After the Z alignment is completed, the ferrule 32 is fixed to the first support member 34 at a plurality of locations S1 on the outer peripheral portion of the hole 34c by spot welding using a YAG laser.

FIG. 4B shows an alignment step of aligning the optical fiber 14 with the semiconductor optical amplifier 16. The alignment means that the light emitted from the light transmitting surface 16a of the semiconductor optical amplifier 16 is converted into the spherically shaped end portion 14 of the optical fiber 14.
b so that the light transmission surface 16a is sufficiently guided to the core portion.
And the end 14b achieve an optically coupled alignment. This state corresponds to, for example, the semiconductor optical amplifier 1
6 is realized by arranging the distal end portion 14b of the optical fiber 14 in the main traveling direction of the light emitted from the light transmitting surface 16a and optically adjusting it within a predetermined error range.

Specifically, the first support member 34 to which the ferrule 32 is fixed is moved while maintaining the contact of the mounting member 24 with the receiving surface 24 e of the mounting member 24, and the other end of the optical fiber 14 is moved. The light intensity obtained from the end 52b is measured. The movement and the measurement can be repeated until the measured value of the light intensity becomes equal to or more than a predetermined value. As described above, since the optical fiber 14 is relatively moved with respect to the semiconductor optical amplifier 16 and the light intensity extracted from the optical fiber 14 is measured, the optical fiber 14 is moved relative to the semiconductor optical amplifier 16. When the alignment and the movement and measurement are repeated until the light intensity reaches a predetermined value, preferably a maximum value, a desired coupling state is achieved. The light intensity can be measured while moving the first support member 34. When the light intensity is measured while moving the relative position between the optical fiber and the semiconductor optical amplifier 16 in this manner, the alignment can be performed while continuously monitoring the relative position and the optical coupling state. The position where the desired light intensity is obtained in this manner is the position where the first support member 34 should be fixed to the mounting member 24. After the alignment is completed, a plurality of spots S on the outer peripheral portion of the first support member 34 are formed by spot welding using a YAG laser.
In 2, the first support member 34 is fixed to the mounting member 24. When this step is completed, the tip 1 of the optical fiber 14 is
4b was aligned with the light transmitting surface 16a of the semiconductor optical amplifier 16.

Referring to FIG. 5A, the ferrule 32
Represents a step of being fixed to the second support member 36.
The first support member 34 already has the receiving surface 2 of the mounting member 24.
4e. Subsequently, the third support member 38
Are disposed on the facing surface 34b of the first support member 34.
The optical fiber 1 is inserted into the through hole 38 c of the third support member 38.
The ferrule 32 to which 4 is fixed is passed. Also,
On the contact surface 38d of the third support member 38, the second mounting member 36 is disposed in a state where the second mounting member 36 contacts the flat surface 36a. Second, the ferrule 32 is inserted into the through hole 36c of the mounting member 36. After the placement is complete,
By spot welding using a YAG laser, the ferrule 32 moves the second support member 36 at a plurality of locations S3 on the outer peripheral portion of the opening of the through hole 36c on the facing surface 36b.
Fixed to

Referring to FIG. 5B, the second support member 36 is fixed to the third support member 38. As a result, the positioning of the tip 14b of the optical fiber 14 with respect to the semiconductor optical amplifier 16 is completed. The state is shown.

After the assembling step shown in FIG. 5A, the ferrule 32 is connected to the spot welds S1 and S2.
, And is fixed to the second support member 36 by a spot welded portion S3. However, since the through hole 38c is larger than the outer shape of the ferrule 32, the second support member 36
8 while being in contact with the contact surface 38d. Therefore, when the second support member 36 is moved on the contact surface 38d, the spot welded portion S1 becomes a fulcrum, and the distal end 1 of the optical fiber 14 is moved.
4b moves according to the movement of the second support member 36. According to the principle of leverage, the distance traveled by the tip 14b is limited to the reduced distance determined by the ratio of the distance between the spot weld S3 and the spot weld S1 and the distance between the spot weld S1 and the tip 14b. Not moved. Therefore,
The alignment can be performed again while finely adjusting the tip portion 14b. This adjustment gives the opportunity to readjust the misalignment resulting from the fixation in spot welding S2. The extent to which fine adjustment or readjustment is possible by utilizing the leverage principle depends on the length of the tubular portion 38a of the third support member 38.

After fixing the relative position between the first end 14a of the optical fiber 14 and the light emitting slope 16a of the semiconductor optical amplifier 16, the optical connection between the optical fiber 14 and the semiconductor optical amplifier 16 is made. Since the proper coupling state is adjusted, the final position can be optically finely adjusted. Even in such an adjustment, as described above, the desired optical coupling is achieved by repeating the movement and the measurement, or by performing the measurement while moving.

After the positioning is completed, the third support member 38 is formed at a plurality of locations S4 on the outer peripheral portion of the second support member 36 by spot welding using a YAG laser.
Fixed to. When this step is completed, the tip portion 14b of the optical fiber 14 is connected to the light transmitting surface 16a of the semiconductor optical amplifier 16.
And finally fixed with optical coupling achieved.

Next, referring to FIG. 6, an optical coupling relationship used for adjusting the relative position of the optical fiber with respect to the semiconductor optical amplifier 16 will be described.
The first end 14 b of the optical fiber 14 is arranged so as to face the light transmitting surface 16 a of the semiconductor optical amplifier 16. A light generating device 47 is optically coupled to the second end face 14c of the optical fiber 14.

A measuring device 48 is connected to the semiconductor optical amplifier 16 via a pair of conductive wires 50 between terminals for applying a voltage for generating light in the semiconductor optical amplifier 16. The measuring device 48 can include an ammeter for measuring the current flowing between the terminals. In this case, when light having a wavelength equal to or more than the energy corresponding to the band gap is incident on the active layer of the semiconductor optical amplifier 16, photoconduction (ph
Since the device operates as an oto conductive) mode device, a photo-induced current corresponding to the light intensity is generated. Further, the measuring device 48 can include a power supply for applying a voltage in the opposite direction to the polarity between the terminals of the semiconductor optical amplifier 16 and an ammeter capable of measuring a current flowing through the power supply. In this case, a reverse bias is applied to the active layer of the semiconductor amplifying device 16. For this reason, since the device operates as a photodiode mode device, a photo-induced current corresponding to the light intensity is generated. In the photodiode mode, unlike the photoconductive mode, carriers excited by light are collected not only by concentration diffusion but also by drift due to an electric field.

The optical power applied from the light generator 47 to the optical fiber 14 is sufficient if it is about 0.1 mW to several mW, as in the method described with reference to FIG.
In the case of this method as well, the light reflecting surface 16b of the semiconductor optical amplifier 16 is used.
Further, it is necessary that the light transmitting surface 16a has such a strength that the light transmitting surface 16a is not destroyed by light. Although the photocurrent induced by such optical power depends on the semiconductor optical amplifier and the presence / absence and magnitude of the applied voltage, the photocurrent has a value of several tens μA to several mA.

If the light generator 47 can output modulated light, the modulated input light can be used for alignment. The measuring device 48 can detect the modulated component modulated by the light generating device (light source) 47. If the modulation signal component of the induced photocurrent is detected, the detection sensitivity can be increased. Therefore, the present method can be applied even if the value is smaller than the above-mentioned light input. Regarding these points, it is the same as the above-described method of performing positioning based on the intensity of reflected light.

After assembling such an optical coupling, when the light from the light generator 47 is supplied to the optical fiber 14, a current is generated in the active layer of the semiconductor optical amplifier 16. The value of the generated photo-induced current changes according to the relative position of the optical fiber with respect to the semiconductor optical amplifier.

Even in the present method, it is important to introduce light of sufficient intensity into the active layer of the semiconductor optical amplifier 16. That is, a wavelength of light whose reflectance at the light transmitting surface 16a of the semiconductor optical amplifier 16 is sufficiently small should be adopted. Since the optical characteristics of the light transmitting surface 16a are determined based on the oscillation wavelength of the optical module described above, within a range of about ± 200 nm around the wavelength of light originally generated by the optical module, Applied with sufficient practicality. The light transmitting surface 16a having such characteristics is provided with an antireflection film called a dielectric multilayer film (for example, a SiN film). The optical power to be supplied and the like are applied in the same manner as the method described with reference to FIG.

In this method, in order to generate a photo-induced current in the active layer, it is necessary to use light having a wavelength shorter than the wavelength corresponding to the band gap of the active layer. For a 1.5 μm band optical module of particular interest in practical use, a 1.3 μm band semiconductor laser can be used as a light source. In practice, a semiconductor laser in the 0.94 μm band can also be used. In the case of this method, when the reflection at the light transmitting surface 16a becomes remarkable, the ratio of light effectively used to generate a photo-induced current in the active layer decreases, but a method such as modulating incident light is used. Thereby, the detection sensitivity can be improved. Therefore, it is important to select a wavelength of light that can generate a photo-induced current in the active layer.

In such an optical connection form,
As the optical coupling between the semiconductor optical amplifier 16 and the optical fiber 14 becomes closer, a larger current value is gradually observed in the measuring device 48. Therefore, the degree of achievement of the alignment between the optical fiber 14 and the semiconductor optical amplifier 16 can be determined based on this observation value.

Note that the axial direction in which the active layer of the semiconductor optical amplifier 16 extends does not necessarily need to intersect the light transmitting surface 16a and the light reflecting surface 16b substantially perpendicularly. Observing the photo-induced current generated by the light from the light generating device 47 is what is required to apply the method.

The two methods described above are applicable even if the half-width of the grating formed in the optical fiber 14 is 0.1 nm or less.
It can also be used to manufacture a fiber grating optical module suitable for (wavelength division multiplexing system). More specifically, in the WDM system, 0.6 nm is determined as a standard value of the adjacent wavelength interval. The half-width of the light spectrum of the light source that satisfies this standard must have a value of 0.1 nm or less, that is, a grating having this half-width is required. Even with a fiber grating having such a narrow reflection spectrum characteristic, in the method of the present application,
The wavelength of light used for aligning the optical fiber 14 and the semiconductor optical amplifier 16 is in a wavelength region different from the reflection spectrum band of the grating, and light having such a wavelength is supplied from the light generators 46 and 47. Therefore, when the optical fiber 14 and the semiconductor optical amplifier 16 are aligned, there is no need to adjust the longitudinal mode in which laser oscillation has occurred, so that such alignment can be performed quickly.

As a result of the above steps, the alignment mechanism 30 is completed, and the light reflecting surface 1 of the semiconductor optical amplifier 16 is
An optical resonator formed from the optical fiber 6b and the fiber grating 14a formed on the optical fiber 14 was assembled. Thereby, the first end 14b of the optical fiber 14 is
A suitable arrangement was realized so that the optical fiber could be optically coupled to the first end face 16a of the semiconductor optical amplifier 16. However, as is clear from the above description, laser oscillation based on this optical resonator has not been performed yet. Therefore, it is not adjusted so that at least one longitudinal mode of the optical resonator including the semiconductor optical amplifier 16 and the fiber grating is included in the reflection band of the fiber grating.
Therefore, the longitudinal mode of the above-mentioned optical resonator substantially coincides with the maximum reflection wavelength of the fiber grating 14a, and does not always coincide substantially with the maximum gain wavelength of the semiconductor optical amplifier 16. Therefore, a process for achieving this coincidence state within a practical range is required.

In the above-described method for manufacturing the fiber grating optical module, the longitudinal mode is subsequently adjusted. The matching of the longitudinal mode is defined as the light reflection surface 16 b of the semiconductor optical amplifier 16 and the fiber grating 14.
This refers to moving the longitudinal mode of the optical resonator formed from the wavelength a to the wavelength band of light that can be reflected by the fiber grating.

As described above, after the optical coupling is achieved through the steps described with reference to FIGS. 4A to 5B, the optical fiber 14 and the semiconductor optical amplifier 16 are formed. Since the laser oscillation based on the optical resonator is performed, the longitudinal mode can be adjusted in a stable state.
This is performed according to the following procedure.

Since the alignment of the optical fiber 14 and the semiconductor optical amplifier 16 has been completed, the fiber grating 14a of the optical fiber 14 and the light reflecting surface 1 of the semiconductor optical amplifier 16 have been completed.
6b can be oscillated. A current sufficient for the laser to oscillate is applied to the semiconductor optical amplifier 16. The adjustment of the longitudinal mode is performed by changing the temperature of the semiconductor optical amplifier 16 by applying a current to a thermoelectric cooler (thermoelectric cooler) 28 on which the semiconductor optical amplifier 16 is mounted, for example, a Peltier element.

The reason why the vertical mode can be adjusted by changing the temperature in this manner will be described below. The active layer and the cladding layer of the semiconductor optical amplifier 16
It is formed using a semiconductor material. When the temperature of such a semiconductor material is changed, the refractive index changes. Increasing the temperature increases the free carriers, so that the refractive index decreases. As the refractive index decreases, the speed of light propagating in the medium increases, so that the effective optical resonance length decreases. For this reason, the longitudinal mode moves to the shorter wavelength side. For example, the oscillation wavelength is λ0, and the effective optical resonance length L × n is 10 m.
When m, the longitudinal mode interval (△ lambda) is △ λ = λ ₀ ^2/2
/ N / L, Δλ is several tens of nm at most.
Becomes With such an interval, the vertical mode can be adjusted by changing the temperature.

The fiber grating optical module described in the present application has an optical resonator composed of the light reflecting surface 16b of the semiconductor optical amplifier 16 and the fiber grating 14a.
The laser oscillates at a wavelength at which the product of the reflection characteristic 4a, the longitudinal mode of the resonator, and the gain characteristic of the semiconductor optical amplifier is maximized.

In the case where alignment is performed using a longitudinal mode generated by applying a current to a semiconductor optical amplifier to form a population inversion distribution in the active layer as in the prior art, the longitudinal mode is a fiber mode. Since there is at most about one line in the light reflection band of the grating, when the wavelength of the longitudinal mode does not substantially coincide with the maximum reflection wavelength of the fiber grating, it cannot be stably determined whether or not the fibers are aligned. There was a case. In general, in many cases, this agreement will not be achieved. In particular, when the wavelength dependence of the reflection characteristics of the fiber grating is large,
In other words, in the wavelength region where the slope of the reflection spectrum is large,
Even if the change in the optical output is monitored, whether the coupling efficiency between the optical fiber and the semiconductor optical amplifier is improved as a result of achieving the desired alignment, or as a result of the shift of the longitudinal mode, for example, due to a temperature change, etc. In some cases, it was not possible to distinguish whether the output changed.

However, as already described in detail, in the method of manufacturing the fiber grating semiconductor laser according to the embodiment of the present invention, the end portion 14b of the optical fiber 14 faces the light transmitting surface 16a of the semiconductor optical amplifier 16. After the semiconductor optical amplifier 16 and the optical fiber 14 are arranged, light of a predetermined wavelength is applied from the first end face 14a of the optical fiber 14 to the light transmitting surface 16a of the semiconductor optical amplifier 16. The light introduced into the active layer of the semiconductor optical amplifier 16 is reflected by the light reflecting surface 16b of the semiconductor optical amplifier 16, and is reflected by the light transmitting surface 16b of the semiconductor optical amplifier 16.
It is emitted from a. The emitted light enters the core of the optical fiber 14 from the lensed first end 14 b of the optical fiber 14. The light propagates through the optical fiber 14 without being reflected by the diffraction grating 14 a and reaches the other end of the optical fiber 14. If this reaching light is taken out and detected by the measuring device 54, the optical fiber 1
The intensity of the light extracted from the second end of the optical fiber 14 changes according to the relative position of the optical fiber 4. Measuring device 54
The relative position of the optical fiber 14 with respect to the semiconductor optical amplifier 16 can be adjusted based on the light intensity detected in.

Further, according to a method of manufacturing a fiber grating optical module according to another embodiment of the present invention,
The optical fiber 14 is provided on the light transmitting surface 16a of the semiconductor optical amplifier 16.
After arranging the semiconductor optical amplifier 16 and the optical fiber 14 so that the first end 14b faces the first end 14b, light of a predetermined wavelength is transmitted from the first end 14b of the optical fiber 14 to the light transmitting surface 16b of the semiconductor optical amplifier 16. Was added. Light introduced into the active layer of the semiconductor optical amplifier generates a photo-induced current when absorbed in the active layer. The value of the generated photo-induced current depends on the optical fiber 14 with respect to the semiconductor optical amplifier 16.
Changes according to the optical coupling state of the two, that is, the relative positions of the two. Therefore, the relative position of the optical fiber 14 with respect to the semiconductor optical amplifier 16 can be adjusted based on the current value detected by the measuring device 48.

According to the manufacturing method of the present invention, since laser oscillation is not used as monitor light during alignment, the alignment is not affected by fluctuations in the optical resonator due to movement of the optical fiber, temperature changes, and the like. Therefore, during alignment, the semiconductor optical amplifier 16 is not disturbed by unstable measurement values.
, The optical fiber 14 having the fiber grating 14a can be positioned.

When manufacturing a fiber grating optical module by applying such a method, the inventor
I noticed more things to note when aligning.

The light generators 46 and 47 generally generate light having a specific polarization. When this light propagates to the semiconductor optical amplifier 16, its polarization state may change. The state of polarization may be affected by vibrations of the optical fiber or changes in temperature.

The measurement light incident on the semiconductor optical amplifier is called incident light from the light transmitting surface, propagation on the active layer, reflection on the light reflecting surface, propagation on the active layer, and emission from the light transmitting surface. Follow the route. The propagation of light in the semiconductor optical amplifier 16 generally has polarization dependence. FIG. 8 (a) and
According to (b), the light of different linearly polarized light is
When incident on 6, the outgoing light has a specific plane of polarization and has a different light intensity depending on the polarization of the incident light. According to FIG. 8A, the incident light 64a to the semiconductor optical amplifier 16 is
Has one polarization, the outgoing light 64b from the semiconductor optical amplifier 16 also has this polarization. According to FIG. 8B, when the incident light 66a to the semiconductor optical amplifier 16 has another polarized light orthogonal to the one polarized light, the emitted light 66b from the semiconductor optical amplifier 16 changes the one polarized light. Have. The former has a higher light intensity than the latter.

Therefore, even if the change in the light intensity is monitored by the power meter 54, the alignment between the optical fiber 14 and the semiconductor optical amplifier 16 cannot be reliably performed. This is because the change in the light intensity may indicate a change in the optical coupling between the optical fiber 14 and the semiconductor optical amplifier 16 or may indicate a change based on incident light having a different polarization. is there.

In order to perform alignment regardless of the presence or absence of a change in polarization due to disturbance, there is a need for a method of reducing the influence of the change in polarization. The inventor has found that it is effective to change the polarization of the light used for alignment to meet this requirement.

FIGS. 9 and 11 show a preferred embodiment for realizing this. In these embodiments, a polarization changing unit 62 such as an optical scrambler is disposed between an optical coupling unit 52 such as an optical coupler and the light generator 46. FIG. 10 shows another preferred embodiment. In this embodiment, a polarization changing means 62 such as, but not limited to, an optical scrambler is disposed between the fiber grating 14a and the light generator 46.

The polarization changing means 62 receives light from the light generators 46 and 47 via an optical waveguide such as an optical fiber, and can generate a series of lights having different polarization planes from the light. As an example of an optical scrambler,
There is a PS-155 polarization scrambler manufactured by Fiber Pro. By such a polarization changing means 62, the loss is about 1 dB,
The polarization plane can be scrambled in a range from several tens of kHz, for example, 10 kHz to several MHz, for example, 1 MHz.

In the embodiment shown in FIGS. 9 and 11, the polarization changing means 62 uses a series of light including light of one polarization plane and light of another polarization to adjust a certain arrangement. Since the light intensity is evaluated, the influence of a change in the polarization plane that can occur during the propagation of the optical fiber can be averaged. For example, from the linearly polarized light received from the light generators 46 and 47, the polarization changing means 62 generates a series of light having light of several polarization planes. The light intensity of the light is measured using the measuring device 54. Such a measurement may take a predetermined time period associated with the scrambling frequency, for example, 1
This can be performed in a time of about μs to 1 ms.

In the embodiment shown in FIG. 10, the polarization changing means 6
According to No. 2, a series of light including light having one polarization plane and light having another polarization plane is used to evaluate the photo-induced current for a certain arrangement. For this reason, FIG. 9 and FIG.
As in the first embodiment, the effects of changes in the plane of polarization that can occur during optical fiber propagation are averaged. Therefore, the change in the photo-induced current reflects the relative position between the optical fiber and the semiconductor optical amplifier.

In the embodiments shown in FIGS. 9 to 11, it is preferable that a series of lights having random polarization or a series of lights having pseudo-random polarization is generated by the polarization changing means 62. Even if such a series of light is disturbed in the optical fiber to change the polarization plane, the influence on the measured value for alignment is small.

The embodiments of the present invention have been described with reference to various examples. Each of the features described can be combined with other features.

[0110]

According to the method for manufacturing a fiber grating semiconductor laser according to the present invention, after the semiconductor optical amplifier and the optical fiber are arranged so that the end of the optical fiber faces the light transmitting surface of the semiconductor optical amplifier, the optical fiber is removed. Light of a predetermined wavelength is applied to the active layer from one end through the light transmitting surface of the semiconductor optical amplifier. The amount of light introduced changes according to the relative position of the semiconductor optical amplifier and the optical fiber. Light in the active layer is reflected on the light reflecting surface of the semiconductor optical amplifier and is emitted from the light transmitting surface of the semiconductor optical amplifier. This emitted light is introduced into the optical fiber via one end of the optical fiber. The amount of light changes according to the relative position between the semiconductor optical amplifier and the optical fiber. For this reason, if the light introduced through the optical fiber is extracted and its intensity is measured, the intensity of the light extracted through the optical fiber changes according to the optical coupling state between the semiconductor optical amplifier and the optical fiber. .

According to another method for manufacturing a fiber grating optical module according to the present invention, after arranging the semiconductor optical amplifier and the optical fiber such that one end of the optical fiber faces the light transmitting surface of the semiconductor optical amplifier. Light of a predetermined wavelength is applied to the active layer from one end of the optical fiber through the light transmitting surface of the semiconductor optical amplifier. The introduced light generates a photo-induced current when absorbed in the active layer. Since the amount of light introduced into the active layer changes according to the relative position of the semiconductor optical amplifier and the optical fiber, the value of the photo-induced current generated by this light also changes according to the relative position of the two. Change.

Therefore, the positions of the semiconductor optical amplifier and the optical fiber can be adjusted based on the intensity or current value of the extracted light.

Accordingly, there has been provided a method of manufacturing a fiber grating optical module for forming an optical resonator by optically coupling an optical fiber including a fiber grating to a semiconductor optical amplifier.

[Brief description of the drawings]

FIG. 1 is a perspective view of a fiber grating laser module.

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

FIG. 3 is a schematic diagram showing a state in which a mounting member is fixed to an assembling jig.

FIGS. 4 (a) and 4 (b) are each an assembled cross-sectional view taken along the line II of FIG. 1;

5 (a) and 5 (b) are each an assembled cross-sectional view shown in the II section of FIG. 1. FIG.

FIG. 6 is a schematic diagram showing a state in which a mounting member is fixed to an assembling jig.

FIG. 7 is a schematic diagram showing a state in which the mounting member is fixed to an assembly jig.

8 (a) and 8 (b) show polarization of incident light,
5 is a drawing showing the relationship between the intensity of emitted light and polarization.

FIG. 9 is a schematic diagram showing a state in which the mounting member is fixed to an assembly jig.

FIG. 10 is a schematic diagram showing a state in which a mounting member is fixed to an assembly jig.

FIG. 11 is a schematic diagram showing a state in which a mounting member is fixed to an assembly jig.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fiber grating optical module, 10 ... Main part of fiber grating laser module, 12 ...
Housing, 12a: body part, 12b: tubular part, 12c
... Lead pins, 16 ... Semiconductor optical amplifiers, 18 ... Light receiving elements, 22, 24, 26 ... Mounting members, 28 ... Cooling elements, 3
0: Positioning mechanism, 32: Ferrule, 34: First
, A second support member, 38 a third support member, 42 a moving mechanism, 42a a translation mechanism in the X-axis direction, 42b a translation mechanism in the Y direction, 42c a Z-axis Translational movement mechanism in the direction, 42d rotation mechanism for rotating φ around the Z axis, 46, 47 light generation device, 48 measurement device, 50 conductive wire, 52 optical coupling means, 54 power meter 56 ... bandpass optical filter, 58 ... optical isolator,
60 power supply 62 polarization changing means

Claims (16)

[Claims] 1. A fiber grating in which a semiconductor optical amplifier having a light transmitting surface and a light reflecting surface and an optical fiber having one end and a fiber grating provided at a predetermined distance from the one end are relatively aligned. An optical module manufacturing method, comprising: arranging the semiconductor optical amplifier and the optical fiber such that the one end of the optical fiber faces the light transmitting surface of the semiconductor optical amplifier; An incident step of applying light to the light transmitting surface of the semiconductor optical amplifier through the one end of the optical fiber; and the predetermined light reflected by the light reflecting surface of the semiconductor optical amplifier and extracted through the optical fiber. An alignment step of adjusting the relative positions of the semiconductor optical amplifier and the optical fiber based on the intensity of light having a wavelength; A method for manufacturing a fiber grating optical module comprising: 2. The aligning step includes: a moving step of relatively moving a position of the optical fiber and a position of the semiconductor optical amplifier; and a measuring step of measuring intensity of light extracted through the optical fiber. The method for manufacturing a fiber grating optical module according to claim 1, comprising: 3. The method according to claim 2, wherein the aligning step includes a step of measuring an intensity of light extracted through the optical fiber while relatively moving the optical fiber and the semiconductor optical amplifier. Item 2. A method for manufacturing a fiber grating optical module according to Item 1. 4. The method according to claim 1, wherein the incident step includes a modulating step of modulating the light of the predetermined wavelength applied to the light transmitting surface of the semiconductor optical amplifier, and the aligning step is performed through the optical fiber. Adjusting the relative position of the semiconductor optical amplifier and the optical fiber based on the modulation component of the light of the predetermined wavelength,
4. The modulation component according to claim 1, wherein the modulation component is related to a modulation performed in the modulation step.
The method for manufacturing a fiber grating optical module according to any one of the above. 5. The method for manufacturing a fiber grating optical module according to claim 1, further comprising a light emitting step of causing said semiconductor optical amplifier to emit light prior to said aligning step. 6. The incident step, wherein a series of light including a first polarized light and a second polarized light is added to the light transmitting surface.
A method for manufacturing the fiber grating optical module according to claim 1. 7. The method for manufacturing a fiber grating optical module according to claim 1, wherein in the incident step, a series of light having a polarization plane scrambled is added to the light transmission plane. 8. The aligning step includes: a moving step of relatively moving a position of the optical fiber and a position of the semiconductor optical amplifier; and The method for manufacturing a fiber grating optical module according to claim 6, further comprising: a measuring step of measuring over a period during which light is introduced. 9. A fiber grating in which a semiconductor optical amplifier having a light transmitting surface and a light reflecting surface and an optical fiber having one end and a fiber grating provided at a predetermined distance from the one end are relatively aligned. An optical module manufacturing method, comprising: arranging the semiconductor optical amplifier and the optical fiber such that the one end of the optical fiber faces the light transmitting surface of the semiconductor optical amplifier; An incident step of applying light to the light transmitting surface of the semiconductor optical amplifier through the one end of the optical fiber; andthe light-induced current generated by the light of the predetermined wavelength in the semiconductor optical amplifier. Aligning the semiconductor optical amplifier and the optical fiber relative to each other. Manufacturing method of optical module. 10. The aligning step includes: a moving step of relatively moving a position of the optical fiber and a position of the semiconductor optical amplifier; and a measuring step of measuring the intensity of the photo-induced current. The method for manufacturing a fiber grating optical module according to claim 9, wherein: 11. The step of aligning, while relatively moving the optical fiber and the semiconductor optical amplifier,
The method for manufacturing a fiber grating optical module according to claim 9, further comprising a step of measuring a value of the photoinduced current. 12. The incident step includes a modulation step of modulating light of the predetermined wavelength applied to the light transmitting surface of the semiconductor optical amplifier, and the aligning step includes a step of applying a modulation component of the photoinduced current to the light component. 12. The relative position of the semiconductor optical amplifier and the optical fiber is adjusted based on the above, and the modulation component is related to the modulation in the modulation step. Of manufacturing a fiber grating optical module. 13. The method of manufacturing a fiber grating optical module according to claim 9, wherein in the incident step, a series of light including a first polarized light and a second polarized light is added to the light transmitting surface. 14. The method according to claim 9, wherein in the inputting step, a series of light having a polarization plane scrambled is added to the light transmission plane. 15. The aligning step includes: a moving step of relatively moving a position of the optical fiber and a position of the semiconductor optical amplifier; and measuring the photo-induced current over a period during which the series of light is introduced. The method for producing a fiber grating optical module according to claim 13, further comprising: 16. The semiconductor optical amplifier further comprises a step of adjusting a longitudinal mode of an optical resonator formed by the light reflecting surface of the semiconductor optical amplifier and the fiber grating to fall within a wavelength band of light that can be reflected by the fiber grating. The method for manufacturing a fiber grating optical module according to claim 1, wherein: