JPH09230169A - 2-core fiber collimator structure, optical circuit module and optical amplifier - Google Patents

Abstract

(57) Abstract: A two-core fiber collimator structure, an optical circuit module and an optical amplifier, which are small in size, low in cost and have high reliability, an optical circuit module and an optical amplifier. I will provide a. SOLUTION: Two fibers are pressed into the same hole,
At the exit of the hole, a two-core ferrule that makes the optical axes of the emitted lights of the two fibers parallel to its own center line, and the optical paths of the two emitted lights of the two fibers are at points on the own center line. An optical element in which a lens for refracting so as to intersect and an intersection of the optical paths of two outgoing lights on the center line of the lens are formed on the optical film, and the optical film is preferably arranged perpendicular to the center line of the lens. And is configured.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a two-core fiber collimator structure, an optical circuit module and an optical amplifier,
Especially small size, low cost and high reliability 2
The present invention relates to a core fiber collimator structure, an optical circuit module and an optical amplifier.

Optical amplification technology using an amplification fiber doped with a rare earth element has reached the stage of practical application. In the optical amplifier, it is necessary to combine the pumping light that pumps the rare earth element added to the amplifying fiber with the signal light. The optical circuit module for multiplexing the signal light and the pumping light is required to be small in size, low in cost, and highly reliable, and the two-core fiber collimator structure, which is a main component of the optical circuit module, is also small in size and low in reliability. Cost and high reliability are required.

[0003]

2. Description of the Related Art FIG. 11 shows the configuration of an optical circuit of a conventional optical fiber amplifier. In FIG. 11, reference numeral 1-1 is a first demultiplexer that branches a part of the input signal light, and 2-1 is an electrical converter for converting the branched signal light into an input signal light monitor circuit (not shown). Supplying first photo diode, 3-1
Is a first isolator for preventing the pumping light for exciting the rare earth element added to the amplification fiber from leaking out to the optical transmission line on the input side, and the above-mentioned elements constitute the pre-stage module. Reference numeral 4 is an amplifying fiber doped with a rare earth element, 5 is an optical filter that couples pumping light output from a pumping laser diode described later to the amplifying fiber and transmits signal light, and 6 generates pumping light Pump laser diode, 7-1 is a first total reflection element for guiding the output light of the pump laser diode to the optical filter, and 3-2 is signal light reflected from the optical transmission line on the output side. Is a second isolator for inputting light into the amplification fiber, and 1-2 is a second branch for branching the signal light output from the isolator and a part of the signal light reflected from the optical transmission line on the output side. 2-2, a second photo diode 2-2, which electrically converts the output signal light branched by the second de-multiplexer and supplies it to a monitor circuit for the output signal light (not shown), 2- Reference numeral 3 designates the reflected signal light split by the second demultiplexer. A third photo diode, 7-2, which converts and supplies it to a reflected light monitor circuit (not shown), guides the reflected signal light branched by the second demultiplexer to the third photo diode. The second total reflection element constitutes the latter stage module by the above elements.

In FIG. 11, a portion where light propagates through an optical fiber is a thick solid line, and a portion where light propagates through an optical element such as a space or a lens is a thick broken line.
The portion where the electric signal is propagated is indicated by a thin solid line.

A part of the signal light received from the optical transmission line on the input side is branched by the first demultiplexer, and
It is electrically converted by the diode and supplied to the monitor circuit of the input signal light. The output of the monitor circuit for the input signal light is used for automatic level control of the pump laser diode and warning of the input signal light interruption.

The signal light that has passed through the first demultiplexer is guided to an amplification fiber doped with a rare earth element. The pumping light output from the pumping laser diode is also guided to the amplifying fiber through the optical filter. Then, the rare earth element added to the amplification fiber is once excited to a high energy level by the excitation light, and when it returns to the original energy level, the signal light is amplified by stimulated emission. The amplified signal light is electrically converted by the second demultiplexer and the second photodiode and supplied to the output signal light monitor circuit.
The output of the output signal light monitor circuit is used for automatic level control of the pump laser diode and warning of output signal light interruption.

The output signal light that has passed through the second demultiplexer is sent to the optical transmission line on the output side. On the output side, when the connector between the optical transmission line and the optical fiber amplifier is disconnected or the optical transmission line is broken, the output signal light is reflected and returns. The second demultiplexer electrically converts this and monitors it by the third photodiode.

The above is the structure and operation of the optical circuit of the conventional optical fiber amplifier shown in FIG. 11. Next, the structure of the optical circuit module forming the optical circuit of FIG. 11 will be described. FIG.
2 is a rear stage module of the conventional optical circuit module.

In FIG. 12, the same reference numerals as those in FIG. 11 represent the same constituent elements, but all constituent elements will be described here as well. 21-1 is a first port for connecting an amplification fiber doped with a rare earth element and a post-stage module, 2
Reference numeral 1-2 is a second port for supplying pumping light to the subsequent module, 21-3 is a third port for coupling the output signal light to the optical transmission line, and these have the same structure. For details of only the first port, see 21-1-1.
Is a ferrule, 21-1-2 is a capillary 21-1-3
Is a lens, 21-1-4 is a lens holder, 21-1-5
Is a pipe, 21-1-6 is a block, and 21-1-7 is a rubber bush. Reference numeral 5 is an optical filter that couples pumping light output from a pumping laser diode (not shown) to the amplification fiber and transmits signal light. Reference numeral 7-1 is a first filter for guiding the pumping light to the optical filter. Total reflection element, 3-2 is a second isolator for preventing the signal light reflected from the output side optical transmission line from being input to the amplification fiber, 1-2 is a signal output from the isolator A second demultiplexer for branching the light and a part of the signal light reflected from the optical transmission line on the output side, 2-2 electrically converts the output signal light branched by the second demultiplexer. The second photo diode 2-3 supplied to the monitor circuit of the output signal light (not shown) electrically converts the reflected signal light branched by the second demultiplexer into reflected light (not shown). Third photo supplied to the monitor circuit of
A diode, 7-2 is a second total reflection element for guiding the reflected signal light branched by the second demultiplexer to the third photodiode, and 22 is a housing. 2-2-1 and 2-3
-1 is a second photo diode holder and a third photo diode holder for attaching the second photo diode and the third photo diode to the housing, respectively.
It is a holder.

Here, mechanically, the pipe and the lens holder and the lens holder and the ferrule are welded in advance, and the pipe and the block are welded after adjusting the optical path.
In addition, the block and the housing, and the photodiode holder and the housing are also welded. Furthermore, the total reflection element, the optical filter, and the demultiplexer are bonded to the housing with an epoxy adhesive.

Optically, the signal light transmission line and the pumping light transmission line are constituted by independent fiber collimators, and moreover, the signal light transmission line and the pumping light transmission line are arranged in parallel. Then, the light guided from the first port and the second port through the lens into the rear stage module is made to be parallel rays. In addition, the optical films formed on the total reflection element, the demultiplexer, and the optical filter are arranged so as to form an angle of 45 degrees with respect to the optical path so that the optical path configuration is the simplest. Therefore, in order to prevent the light reflected by the end face of one photodiode from entering the other photo diode, use an inclined photo diode holder so that the optical axis of the photodiode stands on the end face of the housing. I'm trying not to match the normal.

FIG. 13 shows a configuration in which the pumping light and the signal light are combined by using a conventional SELFOC lens. FIG.
In the above, 8-1-1 is an amplification fiber doped with a rare earth element, and 8-1-2 is a fiber for transmitting the pumping light output from the pumping laser diode. Reference numeral 25 is a 1/4 pitch SELFOC lens, and 5 is an optical filter for coupling pumping light output from a pumping laser diode (not shown) to the amplification fiber and transmitting signal light.

The two fibers 8-1-1 and 8-1-2 are bonded to the SELFOC lens at positions symmetrical with respect to the center of the SELFOC lens, and the SELFOC lens is bonded to the two fibers. The surface opposite to the surface on which it is bonded is bonded to the optical filter. The filter film of the optical filter is formed on the surface that is bonded to the SELFOC lens, and the excitation light that has entered the SELFOC lens from the fiber 8-1-2 is reflected by the filter film to the amplification fiber. Be guided. Then, the signal light amplified by the amplification fiber passes through the fiber 8-1-1, the SELFOC lens and the optical filter, and is emitted to the right side in FIG.

[0014]

In the configuration of FIG. 12, the signal light transmission line and the pumping light transmission line are optically constituted by independent fiber collimators, and the mounting space is made as small as possible. The signal light transmission line and the pumping light transmission line are arranged in parallel. Therefore, the total reflection element 7-1 is required to couple the pumping light to the signal light transmission line, and the post-stage module is enlarged by the space between the total reflection element 7-1 and the optical filter 5. Become.

In order to make the optical path structure simplest, the optical films formed on the total reflection element, the demultiplexer, and the optical filter are arranged at an angle of 45 degrees with respect to the optical path. There is. Therefore, in order to prevent the light reflected by the end face of one photo diode from entering the other photo diode, the photo diode is adjusted so that the optical axis of the photo diode does not coincide with the normal line set up on the end face of the housing. diode·
Holders 2-2-1 and 2-3-1 must be used.

Further, since the optical axis and the optical films formed on the total reflection element, the demultiplexer and the optical filter are arranged so as to form an angle of 45 degrees with respect to the optical path, the polarization dependence is exhibited. It is undesirably large.

In the structure shown in FIG. 13, the two-core fiber and the SELFOC lens are bonded with an adhesive, and
The SELFOC lens and optical filter are also glued together. The beam diameter of the light at the exit point from the fiber is 1
The optical power is on the order of 0 micron, and the optical power confined in the narrow beam is large on the order of 20 to 200 milliwatts. Therefore, carbon and impurities in the adhesive absorb light energy and generate heat, resulting in deterioration of the adhesive. May progress.

As described above, the technique shown in FIG. 12 requires a large number of elements and is difficult to reduce in size.
There is a problem with reliability in the technique shown in. It is an object of the present invention to provide a two-core fiber collimator structure and an optical circuit module structure which can solve such a problem, which are small in size, low in cost, and have high reliability.

[0019]

[Means for Solving the Problems] FIG.
1 is a configuration (1) of an optical circuit of an optical fiber amplifier using a collimator.

In FIG. 1, 1-1 is a first branching device for branching a part of the input signal light, and 2-1 is a monitor of the input signal light which is not shown by electrically converting the branched signal light. The first photodiode 3-1 supplied to the circuit is a first isolator for preventing the pumping light for exciting the rare earth element added to the amplification fiber from leaking out to the optical transmission line on the input side, A pre-stage module is constituted by the above elements. Reference numeral 4 is an amplifying fiber doped with a rare earth element, 5 is an optical filter for coupling pumping light output from a pumping laser diode described later to the amplifying fiber and transmitting signal light,
6 is a pump laser diode for generating pump light, 3-2
Is a second isolator for preventing the signal light reflected from the output side optical transmission line from being input to the amplification fiber, 1-2 is the signal light output from the isolator and the output side optical transmission line A second branching device for branching a part of the signal light reflected from the optical fiber, and 2-2 for electrically converting the output signal light branched by the second branching device to monitor the output signal light (not shown). Second photo diode feeding the circuit, 2
Reference numeral -3 is a third photo diode for electrically converting the reflected signal light branched by the second branching device and supplying it to a reflected light monitor circuit (not shown). It

In FIG. 1, a portion where light propagates through an optical fiber is a thick solid line, a portion where light propagates through an optical element such as a space or a lens is a thick broken line, and a portion where an electric signal propagates is thin. It is shown by a solid line. here,
The two-core fiber collimator is applied to a portion where an amplification fiber and a fiber for transmitting pumping light are combined with an optical filter in a post-stage module.

FIG. 2 shows the configuration of a post-stage module using a two-core fiber collimator. In FIG. 2, 8-1
Is two fibers on the input side to the post-stage module, one is a fiber on the signal light transmission line side including a rare earth element-doped fiber that amplifies the signal light, and the other is a fiber on the pumping light transmission line side. 10-1 is a two-core ferrule, 11 is a sleeve for fixing the two-core ferrule to a lens holder to be described later, 12-1 is a first lens, 13-1 is a lens including the first lens 12-1 -Assembly, 5 is an optical filter, 14 is a first lens holder, and 15 is a convex block, and a two-core fiber collimator is constituted by the above components. 20 is a housing.

Further, 3-2 is an isolator for preventing the signal light reflected on the output side from leaking to the input side, and 1-2 is a part of the signal light which is the output light of the isolator,
A second branching device 2-2 for branching a part of the signal light reflected from the output side, 2-2 electrically converts a part of the output signal light and supplies it to a monitor circuit for the output light (not shown). The second photo diode 2-3 is a third photo diode 2-32 that electrically converts a part of the reflected signal light and supplies it to a reflected light monitor circuit (not shown). The second photo diode holder for fixing the photo diode of 1) to the housing is a third photo diode holder for fixing the third photo diode to the housing.

Further, 17 is a second lens for coupling the collimator beam to the optical fiber on the output side, 18 is a second lens holder for fixing the second lens, 19 is a common guide, and 16 is 1 The core ferrule, 9 is a signal output fiber.

The feature of the configuration of FIG. 2 is that the signal light transmission line and the pumping light transmission line are constituted by a two-core fiber collimator, and the first lens and the fiber, and the first lens and the optical filter. Is fixed without adhering, the optical filter is arranged perpendicular to the optical axis of the two-core fiber collimator to reflect the pumping light and couple it to the signal light transmission line, and the optical of the second branching device. The incident angle of light to the surface of the film is 4
The polarization dependence is improved by making it smaller than 5 degrees, and even if the optical axes of the second and third photo diodes are made perpendicular to the end face of the housing, the reflected light at the end face of one photo diode is -The point is that it is not incident on the diode.

That is, by using a two-core fiber collimator, the number of optical elements can be reduced, at the same time, the post-stage module can be downsized, and the polarization dependence of the post-stage module can be improved.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the configuration of FIG. 2, a two-core ferrule and a sleeve are welded, a first lens holder and a sleeve, and a first lens holder and a convex block are welded after optical axis adjustment. The convex block and the housing are also welded.
Similarly, the one-core ferrule and the second lens holder, the second lens holder and the common guide, and the common guide and the housing are also welded. The second and third photodiode holders and the housing are also welded. That is, the member made of metal is fixed by welding.

On the other hand, it is adhesion that fixes the optical filter to the lens holder. However, since the adhesive is applied and adhered only around the optical filter, there is no adhesive in the optical path. FIG. 3 is an enlarged view of the two-core fiber collimator section.

In FIG. 3, reference numeral 8-1 denotes two fibers on the input side, one of which is a fiber on the signal light transmission path side including a rare earth element-doped fiber for amplifying the signal light, and the other is a fiber on the pump light transmission path side. Is. 10-1 is a two-core ferrule, 11 is a sleeve, 12-1 is the first lens, 13-
Reference numeral 1 is a lens assembly, 14 is a first lens holder, and 5 is an optical filter.

Here, the optical filter is typically made of glass and has a T-shaped surface on which the light from the two fibers directly impinges.
A plurality of thin films of iO ₂ and SiO ₂ are formed by vapor deposition. When the glass is so-called BK-7, when about 20 layers of TiO ₂ and SiO ₂ thin films are vapor-deposited, the signal light of 1.55 μm is almost transmitted and the excitation light of 1.48 μm is almost reflected.

FIG. 4 shows details of the two-core ferrule. In FIG. 4, 8-1 is two fibers on the input side, one is a fiber on the signal light transmission line side including a rare earth element-doped fiber that amplifies the signal light, and the other is a fiber on the pumping light transmission line side. 10-1 is a two-core ferrule, 10-1-
1 is a capillary. The portion 10-1-2 is filled with an adhesive for fixing the two fibers on the input side to the two-core ferrule and the capillary.

That is, after filling the cavity of the two-core ferrule and the capillary with the adhesive, the two-core fiber is press-fitted into the cavity and heated to cure the adhesive to form the structure of FIG. The portions of the two fibers that are press-fitted into the capillaries are stripped of the coating to expose the fiber strands.
The cavity at the inlet of the capillary is made large in diameter so that it can be smoothly press-fitted, and the cavity at the outlet of the capillary has a diameter equal to twice the diameter of the fiber strand. Therefore, at the exit of the capillary, the center of the two fiber strands and the center of the capillary form a straight line.
Further, if the portion where the diameter of the capillary is twice the diameter of the fiber strand is made sufficiently longer than the diameter of the fiber strand, the two fiber strands can be made parallel at the exit of the capillary. .

Therefore, the excitation light emitted from one of the fiber strands is collimated by the first lens and emitted.
The adjustment for reflecting at the center of the optical film of the optical filter and coupling with the other fiber strand becomes easy.

FIG. 5 shows the adjustment principle (1) for coupling the pumping light to the signal light transmission line. First, in FIG. 5, 8-1-1 is a fiber which is a signal light transmission path, and 8-1
Reference numeral -2 is a fiber which is a pumping light transmission path, 12-1 is a first lens, 13-1 is a lens assembly, and 5 is an optical filter. This figure shows a method set up on the end face of the optical filter. It shows the case where the line is parallel to the optical axis of the two-core fiber collimator.

Let x be the distance between the center line of the first lens and the center line of the fiber, and let the incident angle and the reflection angle of the excitation light with respect to the end face of the optical filter be θ, and let the center point of the first lens be The distance between the optical filter and the optical filter is d, and when the thickness of the light beam can be ignored, it is designed so that x = d · tan θ holds, and if assembled, the pumping light is coupled to the signal light transmission line. be able to.

However, since the optical filter is fixed to the lens holder by adhesion, the normal line standing on the end face of the optical filter is not always parallel to the optical axis of the two-core fiber collimator.
FIG. 6 illustrates this state.

FIG. 6 is a principle of adjustment (2) for coupling the pumping light to the signal light transmission line, and shows a state in which the end face of the optical filter is fixed at an angle φ with respect to the original angle. Illustrated. In this case, the incident angle and the reflection angle of the excitation light with respect to the end face of the optical filter are θ ′, the distance between the center point of the first lens and the optical filter is d, and the thickness of the light beam is When negligible, the center line of the two-core fiber collimator is shifted from the center line of the first lens, and the distance between the center line of one fiber and the center line of the first lens is given by the following formula x ' By so doing, the pumping light can be coupled to the signal light transmission line.

X ′ = d · tan (θ′−φ) That is, if the thickness of the light beam can be neglected, as shown in FIG. 3, the direction of the contact surface between the sleeve and the lens holder (this is x , And y-axis direction) sleeve and lens
The pumping light can be coupled to the signal light transmission line by adjusting the relative position of the holder. Moreover, it is not necessary to actually measure the amounts of θ'and φ, etc., and the sleeve and lens holder are displaced parallel to each other along the joint surface of them (double-core fiber
It is only necessary to find the position where the light incident from one of the two fibers is maximally emitted from the other) by translating the centerline of the collimator with respect to the centerline of the first lens.

However, in practice, the thickness of the light beam cannot be ignored, and error factors such as the aberration of the first lens may exist, so the axial direction of the two-core fiber collimator shown in FIG. It also becomes necessary to perform adjustment in the z-axis direction.

Therefore, the procedure for adjusting the coupling of the excitation light and welding and fixing the two-core fiber collimator section is as follows. Combine the two-core ferrule and sleeve, and attach the lens assembly and optical filter to the lens holder.

A combination of a two-core ferrule and a sleeve is combined with a lens holder having a lens assembly and an optical filter. The position of the two-core ferrule with respect to the sleeve is adjusted in the z-axis direction, and the position of the sleeve with respect to the lens holder is adjusted in the x- and y-axis directions to find the maximum point of coupling between the two-core fibers.

The two-core ferrule is welded and fixed to the sleeve. At this time, when the thickness of the sleeve is small,
The points symmetrical about the center of the sleeve are simultaneously welded through. Again the sleeve position relative to the lens holder is x,
Adjust in the y-axis direction to find the maximum point of coupling between the two core fibers.

The sleeve and the lens holder are welded on the line where they are joined. At this time, points symmetrical with respect to the center of the sleeve are simultaneously welded. After that, the two-core fiber collimator structure assembled as described above is fixed to the housing side. At this time, the joint surface between the lens holder and the convex block, which have the spherically ground structure, is rotated, Of the two-core fiber, the lens holder and the convex block are welded and fixed at an angle at which the coupling between the fiber, which is the signal light transmission path, and the one-core fiber becomes maximum. Also in this case, points symmetrical about the center of the lens holder are simultaneously welded.

After the description of the assembly of the configuration of FIG. 2 is finished, the incident angle of light with respect to the second branching device will be described next. FIG. 7: is a figure for considering the incident angle of the light with respect to a 2nd branch device.

In FIG. 7, reference numeral 23 is a surface of the optical film of the second branching device, and 24 is a surface parallel to the incident surface of the photodiode (hereinafter referred to simply as "incident surface").
When the incident angle with respect to the optical film is 45 degrees as in the conventional case, the light reflected by the optical film is vertically and vertically incident on the incident surface of the photodiode. In this case, there is no polarization dependence on the incident surface of the photodiode, but the polarization dependence on the optical film is poor.

Therefore, when the angle of the optical film is inclined from α by 45 ° to α to make the incident angle to the optical film (45 ° -α), the incident angle of the reflected light on the optical film to the incident surface of the photodiode. Is 2α.

Conventionally, the incident angle with respect to the optical film is 45 degrees, which is not preferable but is considered to be a practical limit.
Assuming that the polarization characteristics of the optical film and the polarization characteristics of the incident surface of the photodiode are similar, it is desirable that the incident angle 2α on the photodiode is less than 45 degrees. That is, α is an angle larger than 0 degrees and smaller than 22.5 degrees. Therefore, it is desirable that the angle of incidence on the optical film is larger than 22.5 degrees and smaller than 45 degrees.

The configuration of FIG. 2 is an example in which a partial two-core fiber collimator in which an amplifying fiber and a fiber for transmitting pumping light and an optical filter are coupled is applied in the optical circuit in the latter stage of FIG. The two-core fiber collimator can be applied to other parts.

FIG. 8 shows the configuration (part 2) of the post-stage module using the two-core fiber collimator. In FIG. 8, reference numeral 8-1 denotes two fibers on the input side to the post-stage module, one fiber on the signal light transmission line side including a rare earth element-doped fiber that amplifies the signal light, and the other fiber on the pumping light transmission line side. Fiber. 10-1 is a first two-core ferrule, 11-1 is a first sleeve for fixing the first two-core ferrule to a first lens holder described later, 1
2-1 is the first lens, 13-1 is the first lens 12
A first lens assembly including -1, 5 is an optical filter,
Reference numeral 14-1 is a first lens holder, 15-1 is a first convex block, and the above-mentioned components constitute a first two-core fiber collimator.

Reference numeral 20 is a housing. Further, 3-2 is an isolator for preventing the signal light reflected on the output side from leaking to the input side, and 1-2 is a second branching device for branching a part of the signal light which is the output light of the isolator. 2-2 is a second photo diode for electrically converting a part of the output signal light and supplying it to an output light monitor circuit (not shown). 2-2-1 is the second photo diode It is a second photodiode holder that is fixed to the housing.

Further, 8-2 is two fibers on the output side of the latter stage module, one is an output fiber for signal light, and the other is a fiber for guiding reflected light to a photo diode (not shown) for monitoring reflected light. Is. 10-2 is a second two-core ferrule, 11-2 is a second sleeve for fixing the second two-core ferrule to a second lens holder described later, 12-2 is a second lens, 13 -2 is a second lens assembly including the second lens 12-2, 1-
3 is a third branch device, 14-2 is a second lens holder,
Reference numeral 15-2 is a second convex block, and a second two-core fiber collimator is constituted by the above components.

In the configuration of FIG. 8, a third branching device is provided at a portion of the second two-core fiber collimator where the first two-core fiber collimator is provided with the optical filter. Is the only difference between the second two-core fiber collimator and the first two-core fiber collimator.

That is, one of the two fibers on the output side is the optical transmission line on the output side, and the other fiber receives a part of the signal light reflected from the output side from the third branching device, It is a fiber that guides the reflected light (not shown) to a photodiode for electrical conversion. By adopting this structure, the crosstalk of the output signal light to the photo diode for the reflected light monitor is completely eliminated, and the number of the photo diodes fixed to the housing is reduced, so that the mounting restrictions are relaxed.

Further, the third branching device is composed of a glass substrate, and the surface of the glass substrate on the fiber side is the glass surface,
On the surface of the glass substrate opposite to that, TiO ₂ and SiO
_Since a non-reflective film consisting of _two films is vapor-deposited and the light is branched by Fresnel reflection on the glass surface, a very low-cost branching device can be realized. When the glass material is so-called BK-7, if the number of layers of the non-reflective film is 4, the branching ratio is 24: 1.
Becomes In this case, it is necessary to consider the polarization dependence of the reflected light, but 0.1 dB when the incident angle of light to the branching device in the two-core fiber collimator structure is about 3 to 5 degrees.
The following does not matter. It is also possible to use a transparent member such as sapphire or quartz, in which case the branching ratio will be different from the above.

FIG. 9 shows the configuration (No. 2) of the optical circuit of the optical fiber amplifier using the two-core fiber collimator.
In FIG. 9, reference numeral 1-1 is a first branching device that branches a part of the input signal light, and 2-1 is an electrical conversion of the branched signal light and supplies it to an input signal light monitor circuit (not shown). The first photo diode 3-1 is a first isolator for preventing the pumping light for exciting the rare earth element added to the amplification fiber from leaking out to the optical transmission line on the input side.
Reference numeral 1 is a first optical filter that couples pumping light output from a first pumping laser diode described later to the amplification fiber and transmits signal light, and 6-1 is a first pumping pump that generates pumping light. The laser diode constitutes the preceding module by the above elements. Reference numeral 4 is an amplification fiber doped with a rare earth element, and 5-2 is a second optical filter for coupling pumping light output from a second pumping laser diode described later to the amplification fiber and transmitting signal light. , 6-2 is a second pumping laser diode that generates pumping light, and 3-2 is a second pumping laser diode that blocks the signal light reflected from the optical transmission line on the output side from being input to the amplification fiber. Isolator 1-2 is a second branching device for branching the signal light output from the isolator and a part of the signal light reflected from the optical transmission line on the output side, and 2-2 is the second branching device. The second photo diode 2-3 which electrically converts the output signal light branched by the above and supplies it to the monitor circuit of the output signal light not shown in the drawing, 2-3 is the reflected signal light branched by the second branching device. Electrically converted and supplied to a monitor circuit for reflected light (not shown) In third photodiode, it is formed subsequent modules by more elements. This configuration is for supplying pumping light to the amplification fiber from both directions to increase the gain of the amplification fiber.

Also in FIG. 9, a portion where light propagates through an optical fiber is a thick solid line, a portion where light propagates through an optical element such as a space or a lens is a thick broken line, and a portion where an electric signal propagates is thin. It is shown by a solid line. here,
The two-core fiber collimator is a part where the amplification fiber and the fiber for transmitting the pumping light are coupled to the optical filter in the front stage module, and the part where the fiber for transmitting the amplification fiber and the pumping light is coupled to the optical filter in the rear stage module. Applied to the part that

Since the two-core fiber collimator structure and its mounting structure to the housing are the same as those in FIG. 2, the illustration of the front stage module and the rear stage module is omitted.

FIG. 10 shows the configuration (part 3) of the optical circuit of the optical fiber amplifier using the two-core fiber collimator. In FIG. 10, 1-1 is a first branching device for branching a part of the input signal light, 2-1 is an electrical conversion of the branched signal light, and supplies it to an input signal light monitor circuit (not shown). The first photo diode 3-1 is a first isolator for preventing the pumping light for exciting the rare earth element added to the amplification fiber from leaking out to the optical transmission line on the input side. The former module is configured by.

4-1 is a first amplification fiber doped with a rare earth element. Reference numeral 5-1 is a first optical filter that couples pumping light output from a first pumping laser diode described later to the amplification fiber and transmits signal light. 6-1 is a first optical filter that generates pumping light. Pumping laser diode 5-2 is a second optical filter that couples pumping light output from a second pumping laser diode described below to the second amplification fiber described below and transmits signal light. Reference numeral 6-1 is a second pumping laser diode that generates pumping light, and the above-described elements form a middle module.

In the middle module, an isolator may be provided between the first optical filter and the second optical filter or immediately after the second optical filter. 4-2 is a second amplifying fiber doped with a rare earth element.

Reference numeral 3-2 is a second isolator for preventing the signal light reflected from the output side optical transmission line from being input to the amplification fiber, and 1-2 is the signal light output from the isolator. A second branching device 2-2 for branching a part of the signal light reflected from the optical transmission line on the output side is shown by electrically converting the output signal light branched by the second branching device 2-2. The second photo diode 2-3 supplied to the monitor circuit for the non-output signal light electrically converts the reflected signal light branched by the second branching device and supplies it to the monitor circuit for the reflected light not shown. The third photo diode is used to form a post-stage module by the above elements. This configuration,
This is to increase the gain as an optical fiber amplifier by providing two stages of amplification fibers and providing a pump laser diode unique to each amplification fiber.

Also in FIG. 10, a portion where light propagates through the optical fiber is a thick solid line, a portion where light propagates through an optical element such as a space or a lens is a thick broken line, and a portion where an electric signal propagates is thin. It is shown by a solid line. Here, the two-core fiber collimator is applied to two places where the amplification fiber, the fiber for transmitting the pumping light, and the optical filter are coupled in the middle module.

Since the two-core fiber collimator structure and its mounting structure to the housing are the same as those shown in FIG. 2, the illustration of the front stage module and the rear stage module is omitted.

That is, the configuration of the optical circuit module using the two-core fiber collimator is not limited to the type in which the two-core fiber collimator is applied to the input side of the optical circuit module as in the optical circuit module of FIG. There is also a form applied to the output side of the optical circuit module and a form applied to both the input side and the output side of the optical circuit module.

[0065]

As described in detail above, according to the present invention, it is possible to realize a small-sized, low-cost, high-reliability two-core fiber collimator, an optical circuit module and an optical amplifier.

[Brief description of drawings]

FIG. 1 shows the configuration of an optical circuit of an optical fiber amplifier using a two-core fiber collimator (No. 1).

FIG. 2 shows a configuration of a post-stage module using a two-core fiber collimator (No. 1).

FIG. 3 is an enlarged view of a two-core fiber collimator section.

FIG. 4 shows details of a two-core ferrule.

FIG. 5 is a principle of adjustment (1) for coupling pumping light to a signal light transmission line.

FIG. 6 is a principle of adjustment (part 2) for coupling pumping light into a signal light transmission line.

FIG. 7 is a diagram for examining an incident angle of light with respect to a second branching device.

FIG. 8 shows a second-stage module configuration using a two-core fiber collimator (No. 2).

FIG. 9 is a configuration (No. 2) of an optical circuit of an optical fiber amplifier using a two-core fiber collimator.

FIG. 10 is a diagram (part 3) of the optical circuit of the optical fiber amplifier using the two-core fiber collimator.

FIG. 11 shows a configuration of an optical circuit of a conventional optical fiber amplifier.

FIG. 12 is a rear stage module of the conventional optical circuit module.

FIG. 13 shows a configuration in which excitation light and signal light are combined using a conventional SELFOC lens.

[Explanation of symbols]

 1-2 Second branching device 2-2 Second photo diode 2-2-1 Second photo diode holder 2-3 Third photo diode 2-3-1 Third photo diode -Holder 3-2 Second isolator 5 Optical filter 8-1 Two fibers on input side 9 Fiber on output side 10-1 Two-core ferrule 11 Sleeve 12-1 First lens 13-1 Lens assembly 14 First Lens Holder 15 Convex Block 16 1-Core Ferrule 17 Second Lens 18 Second Lens Holder 19 Common Guide 20 Housing

Front page continuation (72) Yukiko Tsuji, 2-chome, Kitaichijo Nishi, Chuo-ku, Sapporo-shi, Hokkaido Within Fujitsu Hokkaido Digital Technology Co., Ltd. (72) Inorihisa Naganuma 2-chome, Kitaichijo Nishi, Chuo-ku, Sapporo, Hokkaido Address Fujitsu Hokkaido Digital Technology Co., Ltd. (72) Inventor Nobuhiro Fukushima 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Kenji Abe (72) Inventor Kenichi Abe 1015, Uedotaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Stock In the company

Claims (8)

[Claims] 1. Two fibers are pressed into the same hole,
At the exit of the hole, a two-core ferrule that makes the optical axes of the emitted lights of the two fibers parallel to its own center line, and the optical paths of the two emitted lights of the two fibers are at points on the own center line. An optical element in which a lens for refracting so as to intersect and an intersection of the optical paths of two outgoing lights on the center line of the lens are formed on the optical film, and the optical film is preferably arranged perpendicular to the center line of the lens. And a two-core fiber collimator structure. 2. The double-core fiber collimator structure according to claim 1, wherein the optical element uses a glass substrate, and a surface of the glass substrate on the optical fiber path is a surface on the side of the two fibers. A two-core fiber collimator structure, which is an optical filter in which a multilayer film of TiO ₂ and SiO ₂ is formed. 3. The two-core fiber collimator structure according to claim 1, wherein the optical element is made of a transparent material, and a surface of the transparent material on the side of the two fibers among surfaces entering the optical path. A two-core fiber collimator structure, which is a branching device in which a multilayer film of TiO ₂ and SiO ₂ is formed. 4. The two-core fiber collimator structure according to claim 1, wherein one of the two fibers is emitted by moving a center line of the two-core ferrule in parallel with a center line of the lens. A two-core fiber collimator structure comprising an adjusting mechanism for allowing the generated light to enter the other of the two-core fibers. 5. The two-core fiber collimator structure according to claim 2, further comprising a mechanism for adjusting a distance between the two-core ferrule and the lens. 6. An optical circuit module, wherein the two-core fiber collimator structure according to any one of claims 1 to 5 is used for at least one of an input side port and an output side port. 7. The optical circuit module according to claim 2, wherein an incident angle of the emitted light with respect to an optical film of a branching device that receives the light emitted from the two-core fiber collimator structure and branches a part thereof. Is set to be larger than 22.5 degrees and smaller than 45 degrees. 8. An optical amplifier to which the optical circuit module according to claim 6 or 7 is applied.