JP3133833B2 - Light star coupler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal input from an arbitrary one of a plurality of optical signal input ports and being equal to all of the plurality of optical signal output ports independently of the polarization state. The present invention relates to an optical star coupler having a function of distributing by light intensity.

[0002]

2. Description of the Related Art Conventionally, this type of optical star tapler has been manufactured using a planar waveguide. FIG. 1A shows the structure of an optical star coupler constituted by a planar waveguide. FIG.
In (a), 1 is a quartz substrate, 2 is an optical signal input port,
3 is an input side optical waveguide, 4 is an optical coupling part, 5 is an output side optical waveguide, and 6 is an optical signal output port.

An optical signal coupled to the coupler from an optical signal input port 2 via an optical fiber propagates through an input optical waveguide 3 and is guided to an optical coupling section 4. The optical coupling unit 4 is shown in FIG.
(b), the optical signal from each input side optical waveguide 3 is diffused in the wide optical waveguide, so that all of the output side optical waveguides 5 are diffused. Is combined with The optical signal guided to the output side optical waveguide 5 and reaching the optical signal output port 6 is again coupled to the optical fiber and transmitted again by this optical fiber.

[0004]

However, in such an optical star coupler, it is essentially impossible to couple all the input and output optical waveguides with the same light intensity. Coupling variations already exist at the design stage of the coupling. In addition, the optical star coupler of this type has a structure in which the optical waveguides on the input and output sides are arranged in one plane. Therefore, as the number of waveguides increases, the above-described variation in coupling becomes particularly large. However, it becomes very difficult to design an optical coupling portion for suppressing such variations to be below an allowable amount. Furthermore, in such an optical star coupler, the polarization stress occurs in the coupling characteristics between the waveguides due to the strain stress generated at the time of manufacturing the waveguide.
As a result, there is a problem that the branching ratio fluctuates due to the fluctuation of the polarization state of the input light, and the function as an optical star coupler is impaired.

FIG. 2 shows a configuration of a large-scale optical star coupler capable of avoiding the above-described variation in coupling. In FIG. 2, reference numeral 11 denotes a 2 made of a planar waveguide.
× 2 light star coupler, 12 is 2 × 2 light star coupler 11
An optical waveguide or an optical fiber for connecting between them. In the configuration shown in FIG. 2, all the optical signals input using the 2 × 2 optical star coupler 11 are combined, and then distributed to the output side using the 2 × 2 optical star coupler 11 again. In the case of the 2 × 2 optical star coupler, the branching ratio can be accurately designed to be 1: 1. Therefore, it is possible in principle to make all the optical outputs have the same intensity. However, as the size of the coupler increases, a large number of 2 ×
To pass through the two-light star coupler 11 and the connection part 12,
An increase in excess loss due to passage is inevitable. Also, with the increase in scale, it becomes difficult to dispose all of the 2 × 2 optical star coupler 11 and the connection waveguide 12 on one substrate. Therefore, it is inevitable to adopt a method in which the entire coupler is divided and manufactured on a plurality of substrates, and these substrates are coupled with an optical fiber. For this reason, an increase in excess loss due to coupling loss between the waveguide on the new substrate and the optical fiber poses a problem. In addition, the above-described method does not solve the problem of the polarization dependence of the waveguide due to the strain stress generated at the time of manufacturing the waveguide.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a spatial three-dimensional connection technology of an optical star coupler that branches input light of an arbitrary polarization state to all output terminals without changing the branching ratio with equal intensity. One of the objectives is to achieve a fundamental solution to the problems inherent in the planar waveguide optical star coupler as described above, by separating the input light into orthogonal polarized light and resynthesizing it. It is another object of the present invention to suppress the signal jitter caused by the difference in the propagation time of the polarized light generated in the process, and to realize an optical coupler applicable to a high-speed optical signal.

According to the present invention, there is provided a means for converting a plurality of optical fiber propagating lights into collimated light beams arranged at an equal interval from each other and injecting the collimated light beams into a star coupler main body, Means for individually coupling each of the collimated light beams arranged on the optical fiber to a plurality of optical fibers. Is separated into two orthogonal linearly polarized light components, the optical path of one of the linearly polarized light components is converted, and this is combined with the linearly polarized light component of the other light beam that is not subjected to the optical path conversion, and propagates on the same optical path. An optical path-changing element having: and two orthogonal collimated light beams for all of the plurality of incident collimated light beams. Each of the linearly polarized light components is separated into the linearly polarized light component and the linearly polarized light component orthogonal thereto, and polarization splitting elements having a function of equalizing the intensities of the separated light beams are alternately arranged. The first stage and the last stage on the incident side of the star coupler body are the optical path conversion elements, which are separated by the first stage optical path conversion element on the incident side of the star coupler body, and The total time required for one of the optical signals synthesized by the optical path conversion element at the last stage of the coupler body to pass through the optical path conversion elements from the first stage to the last stage on the incident side of the star coupler body; The sum of the time required for the other signal to pass through the optical path conversion elements from the first stage to the last stage on the incident side of the star coupler body always becomes equal to each other. Characterized in that it is constituted by an optical path conversion element with Do propagation time equalization function.

According to the present invention, an optical path changing element for equalizing the propagation time transmits one of two linearly polarized beams orthogonal to each other and reflects the other in a direction perpendicular to the direction of its entrance. A first polarizing beam splitter array in which a plurality of polarizing beam splitters having the same shape are stacked in the direction of travel of the reflected linearly polarized light; and a linear polarizing beam having the same shape as the polarizing beam splitter array. A second polarization beam splitter array arranged so that the reflection directions of the two linearly polarized light beams are opposite to each other, and a polarization plane having a function of exchanging the polarization planes of the two linearly polarized light beams that are sandwiched between the two beam splitter arrays and pass therethrough. An optical path changing element configured by a rotating element, which equalizes the propagation time for separating the light beam, and the propagation time for synthesizing the light beam, etc. An optical path conversion element is characterized in that the direction of reflection of polarized light component reflected by the polarizing beam splitter disposed on the light incident side of these elements are configured so as to be opposite to each other.

According to the present invention, the optical path changing element for equalizing the propagation time transmits one of the two linearly polarized beams orthogonal to each other as it is and reflects the other in a direction perpendicular to the direction of entry. A first polarizing beam splitter array in which a plurality of polarizing beam splitters having the same shape are stacked in the traveling direction of the reflected linearly polarized light, and a linear polarizing beam having the same shape as the polarizing beam splitter. A second polarizing beam splitter array, which is transparent and has the same shape as the polarizing beam splitter, and is stacked via a spacer having the same refractive index; 1 A polarizing beam splitter array having the same shape as the polarizing beam splitter array, and a polarizing beam splitter array having the same shape as the polarizing beam splitter array. And a polarizing beam splitter array arranged so that the reflection direction of the linearly polarized light beam is reversed, and the whole is perpendicular to the first or second polarizing beam splitter array with the light entering direction as an axis. An optical path conversion element configured to equalize the propagation time for separating the light beam and an optical path conversion element for equalizing the propagation time for synthesizing the light beam. The device is characterized in that the polarization directions of the polarization components reflected by the respective polarization beam splitters constituting the first polarization beam splitter array of the element are the same.

An object of the present invention is to realize an optical star coupler to which a spatial three-dimensional optical connection technology is applied, and to realize an optical star coupler having a configuration using no planar waveguide at all. Is fundamentally different.

[0011]

FIG. 3 is a wiring diagram schematically showing a path of an optical signal in an optical star coupler in which all input optical signals are equally distributed to all outputs. In FIG. 3, 31 is 2 × 2
Optical splitting element, which divides each of two incident optical signals into two equal parts with an intensity of 1: 1 and combines one of the equally divided optical signals into two identical optical signals. It has the function of emitting light. 32-1 to 32-5 are connection portions for connecting the optical branching elements 31. The connection having the function of the star coupler is realized by alternately arranging the branch element stages in which the optical branch elements 31 are arranged in parallel and the connection parts 32-1 to 32-5.

Each of the optical branching elements shown in this connection diagram
Each light input represents two linearly polarized lights that propagate in the same optical path and whose polarization planes are orthogonal to each other. Further, two adjacent inputs or outputs correspond to mutually orthogonal polarization components of one optical signal. Therefore,
Each of the 32 inputs or outputs shown in FIG.
One set indicates the input or output of one optical signal. Therefore, FIG. 3 shows an example of an optical star coupler for an optical signal having 16 inputs and 16 outputs. In FIG. 3, by realizing the functions of the optical branching element and the connection unit using a polarization distribution element and an optical path conversion element described later, an optical star coupler can be directly realized.

In general, if one optical signal is separated into mutually orthogonal linearly polarized light components, these components will have a phase correlation with each other at the optical frequency level unless the original signal is completely white polarized light. . Therefore, if they are converted to the same polarization component again and combined, interference occurs between both components, and the splitting ratio deviates from the original design value of the coupler, or the splitting ratio changes with the change in the polarization state of the input light. And the operation as a coupler cannot be guaranteed. Therefore, in order to eliminate the influence of such interference, an incident optical signal is first separated into orthogonal polarization components, each of which is individually branched, and finally, these are combined as light having polarization components orthogonal to each other. It is necessary to have such a connection form.

To realize such a connection form, FIG.
Are provided with connection portions 32-1 and 32-5 having the same functions on the input side and the output side, and an intermediate connection portion having a completely similar structure (dotted line in FIG. (Enclosed part) are arranged in parallel.
As is apparent from the figure, the optical signal input from any one input terminal of the intermediate connection section is divided into two equal parts at each branching element stage, and finally has the same intensity as all the output terminals of the intermediate connection section. Be distributed.

Here, all the input optical signals input to the connection network shown in FIG. 3 are separated into orthogonal polarization components by a first connection unit 32-1 and these are guided to another intermediate connection unit. I will Therefore, 16 optical signals each having no phase correlation with each other are input to the two intermediate connection portions.
As is apparent from the figure, the optical signal input from any one input terminal of the intermediate connection section is sequentially divided into two equal parts at each branch element stage, and finally, all of the 16 output terminals of the intermediate connection section Equally distributed. The two intermediate connections are the final connection
Synthesized by 32-5. At this time, mutually orthogonal polarization components of the same input optical signal are combined. However, since the combined optical signals are orthogonal to each other, the components of the same input optical signal are also orthogonal to each other when they are combined. Component. Therefore, interference does not occur between these components, and an equal distribution optical star coupler is realized.

In the connection diagram shown in FIG. 3, the intermediate connection portion is 2 ^N
It can be easily expanded to input ^2N output. This extension is connected to terminal 2
Two ( ^N-1 ) intermediate connection portions are arranged in parallel, and branch element stages are provided before and after the intermediate connection portions, and two outputs of each branch element are distributed one by one to each of the two connection lines. This is realized by connecting the newly provided branch element stage by a connection network. For example, the two outputs of the i-th optical branching element 31 in the preceding stage are connected to the i-th optical branching element 31 in the next stage and the (i + 2 ^N−1) th (when i ≦ 2 ^N−1 ) or i−2 ^{N −. The} above condition is satisfied if the newly provided optical branching element is connected by a connection portion connected to the first optical branching element 31 (when i> 2 ^{N -1} ). As described above, since the intermediate connection portion in FIG. 3 can be easily expanded to 2 ^N inputs and 2 ^N outputs, components orthogonal to each other in one optical signal are guided to different intermediate connection portions in the first and last optical connection portions. Thus, the entire connection diagram of FIG. 3 can be easily extended to 2 ^N inputs and 2 ^N outputs.

FIG. 4 shows a connection equivalent to FIG. In FIG. 4, reference numeral 41 denotes a 2 × 2 optical branching element. 42-1
Reference numeral 42-5 denotes a connection portion connecting the optical branching elements 41. FIG.
In this case, it is necessary to largely shift the optical path at the connection portions at both ends, but in the connection as shown in FIG. 4, a similar function can be achieved by shifting to the adjacent optical path. This has the effect of reducing the number of optical path conversion elements that realize a large optical path shift when actually manufacturing the optical star coupler according to the present invention. Therefore,
By using the configuration of FIG. 4, the optical path length of the light passing through the coupler can be shortened, and the spread of the passing light beam due to the diffraction of the light and the increase in the passing loss due to inadequate adjustment of the optical system can be reduced. it can.

FIG. 5 shows an embodiment of a 64-input / 64-output optical coupler according to the present invention. In FIG. 5, reference numeral 51 denotes 64 optical fibers for guiding input light to an optical coupler, and 52 denotes collimators in which the output lights of the respective optical fibers 51 are arranged at equal intervals in 8 rows and 8 columns, and whose optical axes are parallel to each other. It is a collimated array for converting into a light beam. 53-1 to 53-6 are polarization distributing elements, which are provided for all of a plurality of incident collimated light beams.
It has a function of separating each of the two orthogonal linearly polarized light components into the original linearly polarized light component at a branching ratio of 1: 1 and the linearly polarized light component orthogonal thereto. Reference numerals 54-1 to 54-5 denote optical path conversion elements, which separate all incident collimated light beams into two orthogonal linearly polarized light components, and convert the optical path of one linearly polarized light component of each of the two light beams. These have a function of synthesizing them with a linearly polarized light component of the other light beam, the light path of which is not changed, to propagate on the same optical path. 55−
1, 55-2 is a propagation time equalization type optical path conversion element, which has the same function as the optical path conversion element 54, and the horizontal polarization component and the vertical polarization component incident from the same optical path pass through these two elements. It is configured so that the propagation times required at this time are equal to each other. Reference numeral 56 denotes a collimator array for collecting collimated light in 8 rows and 8 columns that has passed through the polarization distribution elements 53-1 to 53-6 and the optical path conversion elements 54-1 to 54-7, and couples the collimated light to the fiber again. Also, 57 is a collimator array
There are 64 optical fibers for taking out the signal light condensed by 56 from the optical coupler and transmitting it.

The propagation time equalizing type optical path conversion element 55-1 shown in FIG.
Corresponds to the first connection network in FIG. 3, and the propagation time equalization type optical path conversion element 55-2 corresponds to the last connection network in FIG.
In addition, a polarization distribution element 53-1 to 53-6 and an optical path conversion element
54-1 to 54-5 correspond to the two intermediate connection portions arranged in parallel in FIG.

In general, the function of the polarization distribution elements 53-1 to 53-6 is to function such that the principal axis direction is rotated by ± 45 ° with respect to the polarization plane of the incident polarized light, or the optical rotation angle becomes 45 °. It can be realized by an optical rotator whose thickness has been adjusted. The functions of the optical path conversion elements 54-1 to 54-5 are, for example, respectively shown in FIG.
(a) to (e) can be realized by an element in which polarizing beam splitters are stacked in the shapes shown in (a) to (e).

Here, FIGS. 6 (a), (b), (c), (d) and (e)
Are respectively the optical path conversion elements 54-5, 54-4, 54- of FIG.
3, 54-2 and 54-1. In general, a polarizing beam splitter has a function of transmitting one linearly polarized light component of incident light as it is and reflecting a polarized light component orthogonal to the linearly polarized light component in a direction perpendicular to the incident light. The transmitted component is called a P-wave, and the reflected component is called an S-wave. The P wave has a vibration direction of an electric field perpendicular to a plane including the incident light and the reflected S wave, and the S wave has a vibration direction of the electric field included in this plane. Accordingly, in the polarization beam splitters arranged as shown in FIGS. 6A to 6C, the polarization component (horizontal polarization component) in which the electric field oscillates in the depth direction of the paper becomes a P wave, and the electric field is generated in the vertical direction of the paper. The oscillating polarization component (vertical polarization component) becomes an S-wave. On the other hand, in the polarization beam splitters arranged as shown in FIGS. 6D and 6E, the vertical polarization component becomes a P wave and the horizontal polarization component becomes an S wave. Fig. 6 (a)
Has a function of exchanging S light waves of light beams adjacent in the depth direction of the paper surface. FIGS. 6B and 6C show that the size of the polarizing beam splitter in FIG. 6A is doubled and quadrupled, respectively, so that the light beam interval in the depth direction of the paper is 2 times.
It has a function of exchanging S waves of light beams that are twice or four times apart. FIGS. 6 (d) and 6 (e) are views obtained by rotating (a) and (b) by 90 ° about the incident direction of light, respectively, and FIG. 6 (d) shows the S waves of vertically adjacent light beams. (E) exchanges light beams S waves vertically separated from each other by twice the light beam interval. If the light beams in FIG. 5 are numbered sequentially from the top in the depth direction of the paper, the light path exchanges in FIGS. 6 (d) and (e) exchange light beams separated by the numbers 8 and 16 respectively. It is equivalent to Therefore, the function of the intermediate connection network of FIG. 3 can be realized by these optical path conversion elements.

In this case, the polarization distribution elements 53-1 to 53-1 in FIG.
The upper half region and the lower half region of 53-6 and the optical path conversion elements 54-1 to 54-5 respectively correspond to individual intermediate connection portions arranged in parallel. This intermediate connection is
It is a form in which two identical types are arranged in parallel. Therefore, the optical signal components that enter from the same incident position of each intermediate connection portion and exit from the same emission position pass through the intermediate connection portion at the same time irrespective of the incident position and the emission position.

On the other hand, the propagation time equalizing type optical path conversion element 55-
If an optical path conversion element corresponding to the first or last stage connection network in FIG. 3 is simply applied to a portion corresponding to 1, 55-2, the connection in the coupler becomes equivalent to that in FIG. In general, the propagation times until the optical signals separated by 55-1 are combined by the optical path conversion element 55-2 in the final stage are not equal. For this reason, as the speed of the optical signal passing through the coupler increases, the propagation time difference acts as signal jitter, affecting the performance of the coupler. Therefore, in order to apply the present optical coupler to a high-speed optical signal, it is necessary to use the propagation time equalization type optical optical path conversion elements 55-1 and 55-2 as shown in FIG.

FIG. 7 shows a first example of the structure of an optical signal propagation time equalizing type optical path conversion element. FIG. 7A shows the configuration.
(b) shows the optical path. In FIG. 7A, reference numeral 71 denotes a collimated optical signal input terminal, and reference numeral 72 denotes a polarization beam splitter. Numeral 73 denotes a polarization plane conversion element array, an element having a function of exchanging horizontal polarization and vertical polarization such as a half-wave plate and an optical rotator (hatched portion in the figure), and a polarization plane exchange function of a normal glass plate or the like. And the elements having no (the white portions in the figure) are alternately arranged. 74 is a collimated optical signal receiving terminal. In this configuration, the optical path conversion element on the input side shifts the S wave upward by a distance equal to the length of one side of the polarizing beam splitter 72, and the length of one side of the polarizing beam splitter 72 for the S wave. Has a structure in which a polarization plane conversion element array is inserted between a polarization beam splitter array that shifts downward by a distance equal to, and a structure in which an output side optical path conversion element is inverted upside down of an input side optical path conversion element. Have.

As is clear from FIG. 7 (b), when this configuration is used, in the light path conversion element on the incident side, the light beam incident from the same position is the same as the light beam emitted upward regardless of the incident position. Always passes through the optical path longer by d than the light beam emitted downward, and in the optical path conversion element on the emission side,
Regarding the light beam emitted from the same position, the light beam incident from the upper side always passes through the optical path shorter by d than the light beam incident from the lower side regardless of the emission position, so that the light beam in both optical path conversion elements The optical path length difference is canceled, and as a result, the propagation times of the two separated optical signals become equal. Here, d represents the length of one side of the polarizing beam splitter 72.

Although the configuration shown in FIG. 7 corresponds to the wiring network shown in FIG. 3, an optical signal propagation time equalizing type optical path conversion element can also be configured for the wiring network shown in FIG.
FIG. 8 shows a first configuration example of an optical signal conversion device of the optical signal propagation time equalization type corresponding to the wiring network of FIG. In FIG. 8, 81
Is a collimated light signal input terminal, 82 is a polarization beam splitter, and 83 is a polarization plane conversion element array. Reference numeral 84 denotes a collimated optical signal receiving terminal. FIG.
In the case of the above configuration, in the light path conversion element on the incident side, the light beams incident from the same position are emitted at the odd-numbered row height of the collimated optical signal input terminal regardless of the incident position, and the even-numbered light beams are emitted. In the optical path conversion element on the emission side, the light beam emitted from the same position always passes through the optical path longer by d than the light beam emitted at the height of the row, and the collimated light signal receiving terminal is always independent of the emission position. Since the light beam incident from the height of the odd-numbered row passes through an optical path shorter by d than the light beam incident from the height of the even-numbered row, the optical path length difference in both optical path conversion elements Are offset,
As a result, the propagation times of the two separated optical signals become equal. Here, d is the length of one side of the polarizing beam splitter 82.

In the configuration examples shown in FIGS. 7 and 8, even when the optical path conversion elements on the incident side and the exit side of the optical signal are exchanged, the propagation times until the separated optical signals are combined again are equal. Is obvious. Therefore, FIGS. 7 and 8
The present invention also includes a configuration in which the optical path conversion elements on the incident side and the output side are replaced with each other in the above configuration example.

FIG. 9 shows a second example of the configuration of the optical signal transit time equalizing type optical path conversion element. FIG. 9A shows the configuration,
(b) shows the optical path. In FIG. 9A, reference numeral 91 denotes a collimated optical signal input terminal, and reference numeral 92 denotes a polarization beam splitter. 93 is a transparent rod made of a material having the same refractive index as the constituent material of the polarization beam splitter 92 and having the same shape as the polarization beam splitter 92. Also, 94
Is a collimated optical signal receiving terminal.

The optical path conversion device shown in FIG. 9 comprises a first polarizing beam splitter array in which polarizing beam splitters 92 are stacked, and a second polarizing beam splitter array in which polarizing beam splitters 92 and glass rods 93 are alternately stacked. A polarization beam splitter array composed of only the polarization beam splitter 92, which is rotated at a right angle about the light incident direction, is added to the subsequent stage of the optical path conversion element having the joined structure. The polarization beam splitter array added at the subsequent stage shifts only the S wave for the array by d on one side of the beam splitter twice in the opposite direction. Therefore, the light beam passing through this array does not undergo any positional shift, but its S-wave component passes through the optical path by 2d compared to the P-wave component. That is, the polarization beam splitter array has a function of correcting an optical path difference between the P wave and the S wave due to the optical path conversion element at the preceding stage.

As is apparent from FIG. 9B, when this configuration is used, the light beam incident from the same position in the light path changing element on the incident side is a light beam emitted downward regardless of the incident position. Always passes through an optical path longer by d than the light beam emitted upward, and in the optical path conversion element on the emission side,
Regarding the light beam emitted from the same position, the light beam incident from the lower side always passes through the optical path shorter by d than the light beam incident from the upper side regardless of the emission position, so that the light beam in both optical path conversion elements The optical path length difference is canceled, and as a result, the propagation times of the two separated optical signals become equal. Here, d represents the length of one side of the polarization beam splitter 92.

FIG. 10 shows a second example of the configuration of an optical path conversion element of the optical signal propagation time equalization type different from that of FIG. FIG. 10A shows the configuration, and FIG. 10B shows the optical path. In FIG. 10A, reference numeral 101 denotes a collimated optical signal input terminal, and reference numeral 102 denotes a polarization beam splitter. Reference numeral 103 denotes a transparent rod made of a material having the same refractive index as the constituent material of the polarization beam splitter 102 and having the same shape as the polarization beam splitter 102. Reference numeral 104 denotes a collimated optical signal receiving terminal.

The configuration shown in FIG. 10 is such that the front part of the optical signal propagation time equalization type polarization routing element on the output side in FIG. 9 is rotated by 180 ° about an axis perpendicular to the paper. FIG.
As is clear from the optical path diagram of (b), even with such a configuration, in the routing element on the emission side, the light beam emitted from the same position always reflects the light beam incident from below regardless of the emission position. The light passes through an optical path shorter by d than the light beam incident from above. Therefore, even in the configuration of FIG. 10, the propagation times of the two separated optical signals can be made equal as in the case of FIG.

FIGS. 9 and 10 show a configuration in which a polarizing beam splitter array for correcting the optical path length is added after the polarizing beam splitter array having the routing function. Since the element for rotating the optical path length is not used, the optical path length correcting polarizing beam splitter array is installed at a stage before the polarizing beam splitter array having a routing function or in the middle thereof as shown in FIGS. 11 (a) and 11 (b). It is also possible to adopt a configuration in which: In FIG. 11, reference numeral 112 denotes a polarizing beam splitter, and reference numeral 113 denotes a transparent rod.

Further, as a configuration corresponding to the connection network of FIG. 4, a configuration of a routing element as shown in FIG. 12 is also possible. In FIG. 12, reference numeral 121 denotes a collimated optical signal input terminal,
122 is a polarizing beam splitter, 123 is a transparent rod, 124
Is a collimated optical signal receiving terminal. This configuration is shown in FIG.
Are sequentially numbered in the vertical direction from the back side of the paper surface, and the elements corresponding to the optical path conversion elements 54-1, 2, 3, and 5 are sequentially denoted by (c), (b), and (a) in FIG. ) and (e), and FIG.
This is realized by using a polarization beam splitter array rotated so that FIG. 6C is oriented in the same direction as FIG. 6E as an element corresponding to the optical path conversion element 54-4 in the middle stage. In the case of this configuration, in the routing element on the incident side, the light beam incident from the same position has the odd-numbered light beam emitted at the height of the even-numbered row of the collimated optical signal input terminal regardless of the incident position. In a routing element on the emission side, which always passes through an optical path longer by d than the light beam emitted at the row height, the light beam emitted from the same position is always an even number of collimated optical signal receiving terminals regardless of the emission position. Since the light beam incident from the height of the second row passes through an optical path shorter by d than the light beam incident from the height of the odd-numbered row, the optical path length difference in both routing elements is canceled. As a result, the propagation times of the two separated optical signals become equal. Therefore, the configurations of FIGS. 11 and 12 are also included in the present invention.

[0035]

As described above, in the optical star coupler according to the present invention, the propagation time difference until the optical signal separated into two by the coupler input section is recombined is removed, so that the high-speed optical signal Therefore, an optical star coupler that operates stably without being affected by jitter can be realized.

[Brief description of the drawings]

FIG. 1 shows an optical star coupler constituted by a planar waveguide, and FIG. 1 (a) is a view showing the entire structure thereof;
(b) is an enlarged view of the optical coupling part.

FIG. 2 is a diagram illustrating an example of a configuration method of a large-scale optical star coupler.

FIG. 3 is a connection diagram illustrating a path of an optical signal in an optical star coupler.

FIG. 4 is a connection diagram showing a connection equivalent to FIG. 3;

FIG. 5 is an embodiment of a 64-input, 64-output optical coupler according to the present invention.

FIGS. 6A to 6E are diagrams for explaining the configuration of a normal optical path conversion element.

7 is a first configuration example of an optical signal propagation time equalizing type optical path conversion element corresponding to the wiring network of FIG. 3, (a) shows the configuration, and (b) shows the optical path. Is shown.

8 is a first configuration example of an optical signal propagation time equalization type optical path conversion element corresponding to the wiring network of FIG. 4;

FIGS. 9A and 9B show a second configuration example of the optical signal transit time equalization type optical path conversion element. FIG. 9A shows the configuration, and FIG. 9B shows the optical path.

10A and 10B show a second configuration example of the optical signal transit time equalizing type optical path conversion element different from that of FIG. 9; FIG. 10A shows the configuration; and FIG. 10B shows the optical path. .

FIGS. 11 (a) and 11 (b) show a second configuration example of an optical signal propagation time equalizing type optical path conversion element in which the arrangement of a polarization beam splitter array is changed.

FIG. 12 is a second configuration example of an optical signal propagation time equalizing type optical path conversion element corresponding to the connection network of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quartz substrate 2 Optical signal input port 3 Input optical waveguide 4 Optical coupling part 5 Output optical waveguide 6 Optical signal output port 11 Planar waveguide type 2 × 2 optical star coupler 12 Optical waveguide or optical fiber for connection 31 Optical branching element 32-1 to 32-5 Connection part 41 Optical branching element 42-1 to 42-5 Connection branching 51 Incident optical fiber 52 Incident collimator array 53-1 to 53-6 Polarization distribution element 54-1 to 54-5 Optical path Conversion element 55-1, 55-2 Propagation time equalization type optical path conversion element 56 Outgoing collimator array 57 Outgoing optical fiber 71 Collimated optical signal input terminal 72 Polarizing beam splitter 73 Polarizing plane converting element array 74 Collimated optical signal receiving terminal 81 Collimated light signal input terminal 82 Polarized beam splitter 83 Polarization plane conversion element array 84 Collimated light signal receiving terminal 91 Collimated light signal input terminal 92 Polarized beam splitter 93 Transparent rod 94 Collimated light signal reception Terminal 101 Collimated optical signal input terminal 102 Polarizing beam splitter 103 Transparent rod 104 Collimated optical signal receiving terminal 112 Polarizing beam splitter 113 Transparent rod 121 Collimated optical signal input terminal 122 Polarizing beam splitter 123 Transparent rod 124 Collimated optical signal receiving terminal

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 6/28-6/293 G02B 27/28

Claims (3)

(57) [Claims] 1. A means for converting a plurality of optical fiber propagating lights into collimated light beams arranged at equal intervals from each other and entering the star coupler body, and arranged at equal intervals emitted from the star coupler body. Means for individually coupling each of the collimated light beams to a plurality of optical fibers, wherein the optical star coupler main body converts the light beam with respect to all of a plurality of incident collimated light beams. A function of separating the light into two orthogonal linearly polarized light components, converting the optical path of one of the linearly polarized light components, synthesizing this with the linearly polarized light component of the other light beam that is not subjected to the optical path conversion, and propagating on the same optical path. An optical path-changing element having two linearly polarized light beams orthogonal to the collimated light beam with respect to all of the plurality of incident collimated light beams. Each of the light components is separated into the linearly polarized light component and the linearly polarized light component orthogonal thereto, and polarization splitting elements having a function of equalizing the intensities of the separated light beams are alternately arranged. The first stage and the last stage on the incident side of the star coupler main body are the optical path conversion elements, which are separated by the first stage optical path conversion element on the incident side of the star coupler main body, and are separated by the star coupler. The total amount of time required for one of the optical signals synthesized by the optical path conversion element at the last stage of the main body to pass through the optical path conversion elements from the first stage to the last stage on the incident side of the star coupler main body; Of the time required for the other to pass through the optical path conversion elements from the first stage to the last stage on the incident side of the star coupler body. An optical star coupler comprising an optical path conversion element having a transit time equalizing function. 2. An optical path changing element for equalizing the propagation time, wherein one of the two linearly polarized beams orthogonal to each other is transmitted, and the other is reflected in a direction perpendicular to the entering direction. A first polarizing beam splitter array in which polarizing beam splitters having the same shape are stacked in the traveling direction of the reflected linearly polarized light, and a first polarizing beam splitter array having the same shape as the polarizing beam splitter array and reflecting the linearly polarized light beam. A second polarization beam splitter array arranged so that the directions are opposite to each other, and a polarization plane rotation having a function of exchanging the polarization planes of the two linearly polarized lights that are sandwiched between the two beam splitter arrays and pass therethrough. An optical path conversion element configured to equalize the propagation time for separating a light beam, and the propagation time equalizing optical path for combining the light beam 2. The conversion element according to claim 1, wherein the reflection directions of the polarization components reflected by the respective polarization beam splitters disposed on the light incident side of these elements are opposite to each other. Light star coupler as described. 3. An optical path changing element for equalizing the propagation time, which transmits one of two linearly polarized beams orthogonal to each other as it is and reflects the other in a direction perpendicular to the entering direction. A first polarizing beam splitter array in which a plurality of polarizing beam splitters having the same shape are stacked in the traveling direction of the reflected linearly polarized light; and a first polarizing beam splitter array having the same shape as the polarizing beam splitter array. A second polarizing beam splitter array, which is transparent and has the same shape as the polarizing beam splitter, and is stacked via a spacer having the same refractive index; A polarizing beam splitter array having the same shape as the one polarizing beam splitter array, and a same shape as the polarizing beam splitter array; And a polarization beam splitter array arranged so that the reflection direction of the linearly polarized light beam is reversed, and the whole is made to have the light entering direction with respect to the first or second polarization beam splitter array. An optical path conversion element configured to equalize the propagation time for separating the light beams, and an optical path conversion element for equalizing the propagation time for combining the light beams. 3. The apparatus according to claim 1, wherein the polarization directions of the polarization components reflected by the respective polarization beam splitters constituting the first polarization beam splitter array of these elements are the same.
The light star coupler according to 1.