JP2012203221A - Delay interferometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a one-bit delay interferometer which is small-sized and is capable of changing a bit rate and an optical phase.SOLUTION: The delay interferometer includes: rough adjustment means which is disposed in a first optical path and/or a second optical path of light branched by branching means and is configured to include a driving part and wedge-type optical elements having the same apex angle and roughly adjusts an optical path length of light traveling in the first optical path and/or the second optical path by translation of one wedge-type optical driven by the driving part toward the other opposite wedge-type optical element; fine adjustment means which is disposed in the first optical path and/or the second optical path of light branched by branching means and is configured to include a driving part and wedge-type optical elements having the same apex angle and finely adjusts the optical path length of light traveling in the first optical path and/or the second optical path by translation of one wedge-type optical driven by the driving part toward the other opposite wedge-type optical element; and branching and re-coupling means which branches first light traveling in the first optical path and second light traveling in the second optical path, which have been finely adjusted by the fine adjustment means and roughly adjusted by the rough adjustment means, and performs re-coupling based on respective branched light of the first light and the second light and outputs the result.

Description

  The present invention relates to a delay interferometer, and can be applied to, for example, a 1-bit delay interferometer used in an optical transmission system.

  For example, as a method for controlling the optical path length of a Michelson interferometer, a technique as in Patent Document 1 is known. FIG. 2 is an explanatory diagram for explaining a method for controlling the optical path length of a conventional Michelson interferometer. In FIG. 2, the light input from the input port collimator 21 is branched into two by a half mirror 23, one light travels toward the total reflection mirror 24, and the other light is a total reflection mirror 26 driven by an actuator 25. Proceed to the side. Then, the two reflected lights returning to the half mirror 23 are combined to generate interference light (interference signal), and the interference light is output to the output port collimator 22.

  As shown in FIG. 2, in the conventional method, an actuator 25 is attached to the total reflection mirror 26 in the other optical path, and the optical path length is adjusted by moving the position of the total reflection mirror 26 by driving the actuator 25. Is.

  For example, when a Michelson interferometer is used in a high-speed optical communication system, as in the technique described in Non-Patent Document 1, the optical path length of the Michelson interferometer is changed to control the phase of the interfering light (fine movement). (Adjustment (fine adjustment)) and a method of using a relatively large optical path length corresponding to the bit period (coarse adjustment (coarse adjustment)) are assumed to be performed simultaneously. At this time, in order to perform fine adjustment and coarse adjustment by the methods of Patent Document 1 and Non-Patent Document 1, for example, a large stepping motor or actuator is required.

  In general, an actuator using a piezoelectric element, called a PZT actuator, is known as one of small actuators. The PZT actuator uses a “stacked type” that uses expansion and contraction that occurs when an electric field is applied to stacked piezoelectric elements, and a warp that is generated when an electric field is applied, by bonding elements that have different magnitudes and signs of expansion and contraction when applying an electric field. There are “bimorph type” and “monomorph type”.

Japanese Patent Laid-Open No. 09-243461

Yoshihiro Kanda.Hitoshi Murai.Masatoshi Kagawa.Kozo Fujii, ”Highly Stable 160-Gb / s Field Transmission Employing Adaptive PMD Compensator with Ultra High Time-Resolution Variable DGD Generator”, ECOC 2008, September 2008, Bryssels, Belguim, We.3 .E.6, Vol.3-p.207-p.208

  However, the multilayer actuator is very accurate, but has a relatively narrow dynamic range and is suitable for fine adjustment, but is not suitable for coarse adjustment.

  On the other hand, when the expansion / contraction operation of a bimorph type or monomorph type actuator is used, the stage is driven by vibration generated by applying a pulsed electric field by placing the stage on a jig attached to the piezoelectric element. To get a linear motion. However, in this case, there is a problem that the phase of light cannot be controlled because the operation cannot be performed in fine steps.

  Accordingly, an object of the present invention is to provide a 1-bit delay interferometer that is small in size and can change both the bit rate and the optical phase.

  In order to solve this problem, the delay interferometer according to the first aspect of the present invention includes (1) a branching unit that splits an input light beam into two, (2) a first optical path of the light beam branched by the branching unit, and Alternatively, it is disposed in the second optical path, and is configured to include the first drive unit, and the first wedge-type optical element and the second wedge-type optical element having the same apex angle. The second wedge-shaped optical element driven by the first drive unit moves in parallel with the opposing first wedge-shaped optical element, so that the first optical path and / or the second optical element Coarse motion adjustment means for performing coarse motion adjustment of the optical path length of the light traveling in the optical path, and (3) arranged in the first optical path and / or the second optical path of the light beam branched by the branching means, A third wedge-shaped optical element having the same apex angle as that of the second drive unit; A wedge-shaped optical element, and the fourth wedge-shaped optical element driven by the second drive unit moves in parallel to the opposing third wedge-shaped optical element. Thus, fine movement adjusting means for finely adjusting the optical path length of the light traveling in the first optical path and / or the second optical path, and (4) fine movement adjustment by the fine movement adjusting means and coarse movement adjustment by the coarse movement adjusting means are performed. The first light beam traveling in the first light path and the second light beam traveling in the second light path are branched and recombined based on the branched light beams of the first light beam and the second light beam. And a branch recombination means for outputting.

  The delay interferometer according to the second aspect of the present invention includes: (1) a branching unit that splits an input light beam into two; and (2) one of the first branching units branched by the branching unit by giving a tilt to the reflective liquid crystal element. An optical phase control means for reflecting the light beam traveling in the optical path by a reflective liquid crystal element and controlling the optical phase of the light beam; (3) interposed between the branching means and the optical phase control means; The first wedge-type optical element and the second wedge-type optical element each having the same apex angle, the second wedge-type optical element driven by the drive unit. Coarse motion adjusting means for performing coarse motion adjustment of the optical path length of the light beam reflected by the optical phase device and the light beam from the branching device and the light beam reflected by the optical phase device by moving the element in parallel with the first wedge-shaped optical element facing each other. (4) Proceed along the other second optical path branched by the branching means (5) a first light beam reflected by the reflection unit and a second light beam output from the coarse motion adjustment unit are branched, and each of the first light beam and the second light beam is reflected. And branch recombination means for recombining and outputting based on the branched light.

  According to the present invention, it is possible to provide a 1-bit delay interferometer that is small and can change both the bit rate and the optical phase.

It is a block diagram which shows the structure of the delay interferometer of 1st Embodiment. It is explanatory drawing explaining the method to control the optical path length of the conventional Michelson interferometer. It is explanatory drawing explaining the arrangement | positioning relationship between the wedge-shaped optical element driven by an actuator, and the fixed wedge-shaped optical element. It is explanatory drawing explaining the mode of the interference of the light in the half mirror of 1st Embodiment. It is a figure which shows the wedge angle and resolution | decomposability of the delay element for fine adjustment of 1st Embodiment. It is a figure which shows the relationship between the movement amount of the actuator of 1st Embodiment, and optical delay amount. It is a block diagram which shows the structure of the delay interferometer of 2nd Embodiment. It is a block diagram which shows the structure of the delay interferometer of 3rd Embodiment. It is a block diagram which shows the structure of the delay interferometer of 4th Embodiment. FIG. 6 is a schematic diagram illustrating a configuration example when light rays are incident on a wedge-shaped optical element vertically. It is a block diagram which shows the structural example at the time of selecting an incident angle so that light may advance perpendicularly | vertically to the surface which bisects the vertex angle of a wedge-shaped optical element. It is a block diagram which shows the structural example at the time of selecting an incident angle so that light may advance perpendicularly | vertically to the surface which bisects the vertex angle of a wedge type optical element within a wedge type optical element. It is a block diagram which shows the structure of the two wedge type optical elements of 5th Embodiment, and the structure of the periphery. It is explanatory drawing explaining operation | movement of 5th Embodiment.

(A) First Embodiment Hereinafter, a first embodiment of a delay interferometer according to the present invention will be described with reference to the drawings.

  In the first embodiment, for example, a case where the present invention is applied to a 1-bit delay interferometer in an optical communication system adopting DPSK (Differential Phase Shift Keying) as a modulation method will be described as an example.

(A) Configuration of First Embodiment FIG. 1 is a configuration diagram showing a configuration of a delay interferometer 1A of the first embodiment. In FIG. 1, a delay interferometer 1A according to the first embodiment includes an input port collimator 101, two output port collimators 102 and 103, two half mirrors 104 and 105, two prisms 106 and 107, and two. Actuators 108 and 109, two wedge-type optical elements 110 and 111 driven by the actuators 108 and 109, and fixed wedge-type optical elements 112 and 113.

  The actuators 108 and 109 are small actuators (microactuators). The actuators 108 and 109 have movable arms, and the wedge-shaped optical elements 110 and 111 are fixed to the arms, and the wedge-shaped optical elements 110 and 111 are pushed out or retracted by operating the arms. It functions as a drive unit. Thereby, the wedge-shaped optical elements 110 and 111 fixed to the actuators 108 and 109 can be moved.

  The wedge-shaped optical elements 110 and 111 are wedge-shaped optical elements fixed to the actuators 110 and 1111. The wedge-shaped optical elements 110 and 111 can be moved in position by driving the actuators 108 and 109.

  The wedge-shaped optical elements 112 and 113 are wedge-shaped optical elements fixed at predetermined positions.

  Here, in this embodiment, the wedge type optical element 110 and the wedge type optical element 113 fixed to the actuator 108 function as fine movement adjusting means for finely adjusting the optical path length. On the other hand, the wedge-shaped optical element 111 and the wedge-shaped optical element 112 fixed to the actuator 109 function as coarse motion adjusting means for performing coarse motion adjustment of the optical path length.

  The wedge-shaped optical elements 110 and 113 functioning for fine adjustment are installed so that the oblique sides facing each other are parallel to each other. Moreover, the wedge angles of the wedge-shaped optical elements 110 and 113 are both equal, and the wedge-shaped optical elements 111 and 112 that function for coarse adjustment are small.

  The wedge-shaped optical elements 111 and 112 functioning for coarse adjustment are installed so that the oblique sides facing each other are parallel to each other. The wedge angles of the wedge-shaped optical elements 111 and 112 are both equal, and the wedge-shaped optical elements 110 and 113 functioning for fine adjustment are large.

  Note that the fine movement adjusting means including the wedge-shaped optical elements 110 and 113 as one set and the coarse movement adjusting means including the wedge-shaped optical elements 111 and 112 as one set each include two optical paths branched by the half mirror 104. You may make it arrange | position to either or both of these.

  For example, FIG. 1 illustrates the case where the fine movement adjusting means and the coarse movement adjusting means are arranged side by side. However, any of the two optical paths from the half mirror 104 to the half mirror 105 is fine movement adjusting means and The arrangement position of the coarse adjustment means is not particularly limited. For example, either one of the fine movement adjustment unit and the coarse movement adjustment unit may be disposed between the half mirror 104 and the prism 106, and the other may be disposed between the half mirror 104 and the prism 107.

  For example, as will be described later, since the change in the optical path length depends on the apex angle of the wedge-shaped optical element, the fine adjustment means and the coarse adjustment means are arranged in both of the two optical paths branched by the half mirror 104. It may be.

  The prism 106 and the prism 107 are total reflection portions that totally reflect incident light. In this embodiment, a case where a prism is applied as the total reflection portion in order to make the incident position of the incident light beam different from the reflection position of the reflected light beam is exemplified, but the present invention is not limited thereto. It is not a thing. For example, you may make it comprise the total reflection part which combined several mirrors.

  The input port collimator 101 converts the input light input from the input port of the delay interferometer 1A into parallel rays.

  The output port collimators 102 and 103 are configured to output the outgoing light emitted from the half mirror 105 to the output port of the delay interferometer 1A.

  The half mirror 104 divides the light beam from the input port collimator 101 into two, emits one light beam to the prism 106 side (upper side in FIG. 1), and emits the other light beam to the prism 107 side (right side in FIG. 1). It is something to make progress.

  The half mirror 105 receives the light beam reflected from the prism 106 and the light beam delayed by the reflected light beam of the prism 107 passing through the wedge-shaped optical elements 110 to 113, and branches the reflected light beam and the delayed light beam. Combined to generate interference light.

(A-2) Operation of the First Embodiment Next, the operation of the delay interferometer 1A of the first embodiment will be described with reference to FIG. 1, FIG. 3, and FIG.

  First, in FIG. 1, the light input to the delay interferometer 1 </ b> A from an input port (not shown) is converted into parallel rays by passing through the input port collimator 101 and is input to the first half mirror 104.

  The light beam input to the first half mirror 104 is branched into two. One system proceeds to the prism 106 side, and the other system proceeds to the right side in the drawing.

  One line of light is input to the prism 106 and is totally reflected twice by the prism 106. As a result, the light beam is output from a position slightly different from the input position input to the prism 106. The outgoing light beam output from the prism 106 is input to the second half mirror 105.

  The other beam of light passes through a fixed wedge-shaped optical element (first wedge-shaped optical element) 113 and is further fixed to the actuator 108 by a wedge-shaped optical element (second wedge-shaped optical element) 110. Pass through.

  Here, FIG. 3 is an explanatory diagram for explaining the positional relationship between the wedge-shaped optical elements 113 and 110. The positional relationship between the wedge-shaped optical elements 113 and 110 will be described with reference to FIG. In the example of FIG. 3, the wedge-shaped optical elements 110 and 113 are arranged so that the oblique sides of the wedge-shaped optical elements 110 and 113 are perpendicular to the traveling direction of the input light beam.

  As shown in FIG. 3, the wedge-shaped optical element 110 that is movable by being driven by the actuator 108 is set so that the hypotenuse moves in parallel.

  For example, FIG. 3A shows an arrangement relationship when the actuator 108 pushes the wedge-shaped optical element 110 far away, and FIG. 3B shows a case where the actuator 108 pulls the wedge-shaped optical element 110 close. The arrangement relationship of is shown.

  The actuator 108 is moved so that the oblique sides of the wedge-shaped optical element 110 are parallel to each other. Therefore, when the actuator 108 is moved from the state shown in FIG. 3A to the state shown in FIG. The optical element 113 moves in parallel with the hypotenuse.

  Further, as shown in FIG. 3A, when the actuator 108 pushes in the wedge-shaped optical element 110, the actuator 108 slightly retracts the wedge-shaped optical element 110 as shown in FIG. 3B. Sometimes, the time required for the light beam to travel through the wedge-shaped optical element 110 is short, and the optical path length of the light beam is shortened.

For example, in FIGS. 3A and 3B, the movement distance by which the actuator 108 moves the wedge-shaped optical element 110 is “L”. Further, the optical path length of light traveling through the wedge-shaped optical element 110 in FIG. 3A is “l ₁ ”, and the optical path length of light traveling through the wedge-shaped optical element 110 in FIG. 3B is “l ₂ ”. And

In this case, with respect to the moving distance L, the optical path length difference (l ₁ −l ₂ ) is represented by L sin θ / (n−1). Here, n is a refractive index. θ is the wedge angle of the wedge-shaped optical element 110 and the wedge-shaped optical element 113. In the first embodiment, for example, the case where the wedge angle θ = 1 ° is exemplified.

  In FIG. 1, the light beam that has passed through the wedge-shaped optical element 110 passes through the wedge-shaped optical element (third wedge-shaped optical element) 111 and further passes through the wedge-shaped optical element (fourth wedge-shaped optical element) 112. To do. The arrangement relationship of the wedge-shaped optical elements 111 and 112 is also the same as that of the wedge-shaped optical elements 113 and 110 illustrated in FIG.

  However, the wedge angle is different. In the case of the wedge-shaped optical elements 113 and 110 that function for fine adjustment, the wedge angle of the wedge-shaped optical elements 111 and 112 that function for coarse adjustment is, for example, θ = 30 °, while the wedge angle is set to 1 °, for example. Shall be set.

  The light beam that has passed through the fourth wedge-shaped optical element 112 is input to the second prism 107. The light beam is totally reflected twice by the prism 107 and is output from a position slightly different from the position input to the prism 107.

  The light beam emitted from the prism 107 further passes through the fourth wedge-shaped optical element 112, the third wedge-shaped optical element 111, the second wedge-shaped optical element 110, and the first wedge-shaped optical element 113. Then, the light beam that has passed through the first wedge-shaped optical element 113 is input to the second half mirror 105.

  The half mirror 105 receives the light beam emitted from the prism 106 and the light beam emitted from the first wedge-shaped optical element 113.

  FIG. 4 is an explanatory diagram for explaining the state of light interference in the half mirror 105. In FIG. 4, the light beam (1) from the prism 106 and the light beam (2) from the first wedge-shaped optical element 113 are input to the half mirror 105. Light rays (3) to (6) are output from the half mirror 105.

  When the light beam (1) from the first wedge-shaped optical element is input to the half mirror 105, it is branched into the light beam (3) and the light beam (4). In addition, when the light beam (2) from the prism 106 is input to the half mirror 105, it is branched into the light beam (5) and the light beam (6).

  Therefore, the light beam (3) and the light beam (6) interfere with each other and travel to the output port collimator 103 side. Further, the light beam (4) and the light beam (5) interfere with each other and travel to the output port collimator 102 side.

  At this time, the phase of the light beam (3) is in phase with the phase of the light beam (1), but the phase of the light beam (4) has a phase shift of π / 2 with respect to the phase of the light beam (1). The phase of the light beam (5) is in phase with the phase of the light beam (2), but the phase of the light beam (6) has a phase shift of π / 2 with respect to the phase of the light beam (2).

  In FIG. 4, it is assumed that the phase of the light beam (1) is “0” and the phase of the light beam (2) is “π / 2”. It is assumed that the phase difference between the light beam (1) and the light beam (2) is π / 2 and is coupled to the half mirror 105.

  In this case, the phase “0” of the light beam (3) and the phase “0” of the light beam (6) are recombined with a phase difference of “0”. In addition, since the phase of the light beam (4) is “π / 2” and the phase of the light (5) is “−π / 2”, the phase difference is “π” to recombine.

  Therefore, the output from the output port collimator 102 side corresponds to the Constructive Port. Further, the output from the output port collimator 103 side corresponds to Destructive Port.

(A-3) Example Next, effects of the delay interferometer 1A according to the first embodiment will be described with reference to the drawings.

  If the resolution of one step for expanding and contracting the wedge-shaped optical elements 110 and 111 of the actuators 108 and 109 is known, the optical length that can be changed in one step of the actuators 108 and 109 is determined by the wedge angle of the wedge-shaped optical elements 110 and 111.

  FIG. 5 is a diagram showing the wedge angle and resolution of the fine adjustment delay element. In FIG. 5, the wedge angle (Angle) of the wedge-shaped optical element is shown on the horizontal axis, and the minimum optical length that can be varied is shown on the vertical axis.

  In FIG. 5, the optical length resolution when the light beam travels in one direction is indicated by a dotted line, and the resolution when the light reciprocates is indicated by a solid line. Since the first embodiment is reciprocated, the optical length can be changed with the resolution indicated by the solid line.

  Since the angle (wedge angle) of the first wedge-shaped optical element 113 and the second wedge-shaped optical element 110 is 1 °, the optical length that can be changed in one step of the actuator 108 is 0.017 μm. Therefore, 90 steps are required to reach a length corresponding to one wavelength. This means that the phase can be controlled with a resolution of 1/90 of the wavelength.

  Further, how much the distance can be changed when the maximum movement amount of the actuators 108 and 109 is 4 mm will be described.

  FIG. 6 shows the relationship between the movement amounts (horizontal axis) of the actuators 108 and 109 and the optical delay amount (vertical axis). In FIG. 6, the wedge-type optical elements 110 and 111 have a wedge angle of 30 °. A solid line is an example in which one set of wedge-shaped optical elements is used, and two sets of dotted lines and three sets of broken lines are used.

  In FIG. 6, when the movement amount is 0, the delay amount is assumed to be 5 ps. This corresponds to a bit rate of 200 Gb / s. When the movement amount of the actuators 108 and 109 is 4 mm, the delay amount varies from 1 Gps / second to 12.5 ps in one set. Therefore, the variable amount can be changed from 200 Gb / s to 80 Gb / s. .

  Since two sets are 20 ps, the bit rate is variable and a 1-bit delay interferometer capable of handling 200 Gb / s to 50 Gb / s. Further, when three sets are used, the delay amount can be increased to about 30 ps, so that a 1-bit delay interferometer that can cope with 40 Gb / s is obtained.

(A-4) Effects of First Embodiment As described above, according to the first embodiment, a Michelson type 1-bit delay interferometer having a smaller structure and a variable bit rate and phase can be used. Can be configured.

(B) Second Embodiment Next, a second embodiment of the delay interferometer of the present invention will be described with reference to the drawings.

  In 1st Embodiment, the structure at the time of using 2 sets of actuators was illustrated. In the second embodiment, the size is further reduced as compared with the configuration of the first embodiment.

(B-1) Configuration of Second Embodiment FIG. 7 is a configuration diagram showing a configuration of a delay interferometer 1B of the second embodiment. In FIG. 7, the delay interferometer 1B of the second embodiment is driven by an input port collimator 201, two output port collimators 202 and 203, two half mirrors 204 and 205, a prism 206, an actuator 207, and an actuator 207. The wedge-shaped optical element 208, the fixed wedge-shaped optical element 209, the reflective liquid crystal element 210, and the wedge-shaped optical element 211 are configured.

  The actuator 207 is the same drive unit as in the first embodiment. In the first embodiment, the case where two sets of actuators are provided is illustrated, but in the second embodiment, one set of actuators is provided. Thereby, the delay interferometer can be further downsized.

  The wedge-type optical element 208 and the wedge-type optical element 209 have the same wedge angle, and are arranged so that their hypotenuses are parallel to each other.

  The reflective liquid crystal element 210 is a reflective liquid crystal element such as LCOS (Liquid Crystal On Silicon). In the reflective liquid crystal element 210, the orientation of the liquid crystal changes depending on the electric field applied. That is, an electric field is applied to change the liquid crystal so that it has a predetermined angle with respect to incident light. Thereby, the input light is reflected by the liquid crystal of the reflective liquid crystal element 210, so that the phase state of the input light is controlled.

  The wedge-shaped optical element 211 adjusts the reflected light beam from the reflective liquid crystal element 210 so as to be parallel to the light beam input to the reflective liquid crystal element 210.

(B-2) Operation of Second Embodiment Next, the operation of the delay interferometer 1B of the second embodiment will be described with reference to FIGS.

  Light having an electric field that oscillates parallel to the paper surface of FIG. 7 is input to the delay interferometer 1 </ b> B, and the input light is converted into parallel rays by the input port collimator 201. Further, the parallel rays from the input port collimator 201 are input to the half mirror 204.

  The half mirror 204 splits the light beam into two. One system proceeds to the prism 206 side, and the other system proceeds to the wedge-shaped optical element 209 side.

  The light beam traveling to the prism 206 side is totally reflected twice by the prism 206, and is output from a position slightly different from the position input to the prism 206. Light emitted from the prism 206 is input to the half mirror 205.

  The light beam traveling toward the wedge-shaped optical element 209 side passes through the wedge-shaped optical element 209 that is fixed, and further passes through the wedge-shaped optical element 208 that is fixed to the actuator 207. The wedge-shaped optical elements 209 and 208 function as coarse delay elements, and for example, those having a wedge angle of 30 ° can be applied.

  As for the positional relationship between the wedge-shaped optical elements 209 and 208, as shown in FIG. 3, it is assumed that the wedge-shaped optical elements 208 are installed such that their oblique sides move in parallel. This operation is the same as in the first embodiment.

  The light beam emitted from the wedge-shaped optical element 208 enters the reflective liquid crystal element 210. In the reflective liquid crystal element 210, the orientation of the liquid crystal changes according to the applied electric field, and the phase state of the output light is controlled according to this state.

  Here, the reflective liquid crystal element 210 is installed so as to have a slight angle with respect to the incidence of light. In the reflective liquid crystal element 210, the input light is reflected by the liquid crystal having a slight angle. The phase of the light changes as light is reflected by the liquid crystal. That is, the phase of light can be finely adjusted. The reflected light is emitted from the reflective liquid crystal element 210.

  The reflected light whose phase is adjusted by the reflective liquid crystal element 210 is given to the wedge-shaped optical element 211. The wedge-shaped optical element 211 is configured so that the light beam output from the reflective liquid crystal element 210 is parallel to the input light beam of the reflective liquid crystal element 210. Therefore, when the light beam reflected by the reflective liquid crystal element 210 passes through the wedge-shaped optical element 211, the light beam travels parallel to the input light beam.

  Then, the light beam again passes through the wedge-shaped optical element 208 and the wedge-shaped optical element 209 and is input to the half mirror 205.

  In the half mirror 205, the light beam from the prism 206 and the light beam from the wedge-shaped optical element 209 are input, and these light beams are branched and further interfere with each other. The branching and interference of light at the half mirror 205 is the same as in the first embodiment.

(B-3) Effects of the Second Embodiment As described above, according to the second embodiment, as in the first embodiment, two outputs (Constructive and Destructive) are output by the half mirror. Can do. Further, according to the second embodiment, since it is possible to finely adjust the phase of light using a reflective liquid crystal element, one set of actuators that perform coarse adjustment of the phase of light can be provided, and the configuration scale Can be reduced. Furthermore, in order to branch and interfere the light at the half mirror, it can be realized by slightly changing the traveling direction of the parallel rays by the wedge-shaped optical element.

(C) Third Embodiment Next, a third embodiment of the delay interferometer of the present invention will be described with reference to the drawings.

  In the second embodiment, the embodiment using the reflective liquid crystal element has been described. However, since the liquid crystal element is an element using the polarization of light, it is difficult to use the liquid crystal element in an apparatus in which light may be input in any polarization state, such as reception of an optical signal. Therefore, in the third embodiment, a configuration corresponding to all input polarization planes by performing polarization plane diversity will be described.

(C-1) Configuration of the Third Embodiment FIG. 8 is a configuration diagram showing the configuration of the delay interferometer of the third embodiment. In FIG. 8, the delay interferometer 1C of the third embodiment includes an input port collimator 301, two output port collimators 302 and 303, a polarization polarization beam splitter (PBS) 304, and two half mirrors 305 and 306. , Prism 307, actuator 308, wedge-shaped optical element 309 driven by actuator 308, fixed wedge-shaped optical element 310, two half-wave plates 311 and 312, reflective liquid crystal element 313, wedge-shaped optical element 314, an optical path adjusting element 315, and two condensing polarization plane beam splitters (PBS) 316 and 317.

  The wedge-shaped optical elements 310 and 311 facing each other have the same wedge angle.

(C-2) Operation of the Third Embodiment Next, the operation of the delay interferometer 1C of the third embodiment will be described with reference to FIGS.

  The light input from the input port to the delay interferometer 1 </ b> C is converted into parallel rays by the input port collimator 301. Parallel rays from the input port collimator 301 are input to the polarization plane beam splitter 304.

  In the polarization plane beam splitter 304 for spectroscopy, light travels on two axes perpendicular to each other (in FIG. 8, an axis perpendicular to the light traveling direction on a surface parallel to the paper surface and a surface perpendicular to the paper surface). The electric field is separated into two light beams that oscillate in the direction perpendicular to the direction.

  Here, the two light beams whose polarization planes are orthogonal are referred to as light beam (1) and light beam (2). The light beam (1) and the light beam (2) are separated by the polarization polarization beam splitter 304 and output with a slight positional deviation. The distance of this positional deviation is not particularly limited and can be obtained experimentally.

  The two light beams (1) and (2) output from the spectral polarization plane beam splitter 304 are input to the half mirror 305.

  The light beam (1) is branched into two by the half mirror 305. Here, one system is referred to as a light beam (1-1), and the other system is referred to as a light beam (1-2). The light beam (1-1) travels to the prism 307 side, and the light beam (1-2) travels to the wedge-shaped optical element 310 side.

  Similarly, the light beam (2) is also bifurcated by the half mirror 305. Here, one light beam (2-1) of one system travels to the prism 307 side, and the other light beam (2-2) of the other system travels to the wedge-shaped optical element 310 side.

  The light beam (1-1) and the light beam (2-1) input to the prism 307 are each totally reflected twice by the prism 307, and output from a position slightly different from the input position input to the prism 307. The light beam (1-1) and the light beam (2-1) emitted from the prism 307 are input to the half mirror 306.

  On the other hand, the light beam (1-2) and the light beam (2-2) pass through the fixed wedge-shaped optical element 310 and further pass through the wedge-shaped optical element 309 fixed to the actuator 308.

  The wedge-shaped optical element 309 fixed to the actuator 308 and the wedge-shaped optical element 310 are arranged so that the oblique sides of the wedge-shaped optical elements 309 and 310 move in parallel as illustrated in FIG. Has been. The wedge-shaped optical elements 309 and 310 function as optical elements for coarse adjustment.

  Of the light beams emitted from the wedge-shaped optical element 309, a light beam (2-2) having a polarization that vibrates perpendicular to the paper surface of FIG. 8 is input to the half-wave plate 311. By passing through the half-wave plate 311, it becomes a light beam (2-2) ′ having a polarization parallel to the paper surface of FIG. Then, the light beam (2-2) ′ is input to the reflective liquid crystal element 313.

  On the other hand, the light beam (1-2) emitted from the wedge-shaped optical element 309 is input to the reflective liquid crystal element 313 as it is.

  In the reflective liquid crystal element 313, as in the second embodiment, the orientation of the liquid crystal changes according to the applied electric field, and the phase state of the output light is controlled according to this state. Further, the reflective liquid crystal element 313 can change only the phase of a light beam having a polarization that vibrates parallel to the paper surface of FIG. That is, the light beam (1-2) and the light beam (2-2) ′ incident on the reflective liquid crystal element 313 are reflected by the liquid crystal element having a predetermined angle with respect to the incident light, and the reflective liquid crystal element 313 is obtained. It is emitted from.

  The light beam (1-2) and the light beam (2-2) ′ whose phases are adjusted by the reflective liquid crystal element 313 pass through the wedge-shaped optical element 314 and travel in parallel with the light beam input to the reflective liquid crystal element 313. It becomes a ray of light.

  Here, the light beam (2-2) ′ output from the wedge-shaped optical element 314 is input to the half-wave plate 312. The half-wave plate 312 is again a light beam having a polarization that vibrates perpendicularly to the paper surface of FIG. Accordingly, when the light beam (2-2) 'passes through the half-wave plate 312, the output light beam becomes a light beam that vibrates perpendicularly to the paper surface. This output light beam is called a light beam (2-2) ".

  The light beam (1-2) and the light beam (2-2) "pass through the wedge-shaped optical elements 309 and 310 and then enter the half mirror 306. During this time, the light beam (1-2) 2-2) ”is passed through the optical path length adjusting element 315 for adjusting the optical path length.

  In the half mirror 306, the light beam (1-1) and the light beam (1-2) having the same polarization plane interfere with each other, and the light beam (2-1) and the light beam (2-2) '' interfere with each other. As shown in the half mirror 306 in FIG. 8, light interference occurs in two places in the half mirror 306.

  The two light beams output from the left side of the half mirror 306 are condensed by the condensing polarization plane beam splitter 316, combined by the output port collimator 302, and output. Further, the two light beams output from below the half mirror 306 are condensed by the condensing polarization plane beam splitter 317, combined by the output port collimator 303, and output.

(C-3) Effects of the Third Embodiment As described above, according to the third embodiment, a small delay interferometer using a reflective liquid crystal element is used regardless of the polarization plane of the input signal to be input. Operation can be realized.

(D) Fourth Embodiment Next, a fourth embodiment of the delay interferometer of the present invention will be described with reference to the drawings.

  In the first embodiment, the delay interferometer applied to the optical communication system adopting DPSK as the modulation method has been described.

  On the other hand, in a high-speed optical communication system employing DQPSK (Differential Quadrature Phase Shift Keying), which is being studied, a system using two 1-bit delay interferometers is applied. In this case, two 1-bit delay interferometers described in the first embodiment are used. From the viewpoint of space saving, it is desirable to realize with one 1-bit delay interferometer.

  Therefore, in the fourth embodiment, a single 1-bit delay interferometer that can cope with a DQPSK modulation signal will be described.

(D-1) Configuration of the Fourth Embodiment FIG. 9 is a configuration diagram showing the configuration of the delay interferometer of the fourth embodiment. In FIG. 9, the delay interferometer 1D of the fourth embodiment includes two input port collimators 401 and 402, four output port collimators 403, 404, 405 and 406, two half mirrors 407 and 408, 2 Optical phase adjusting elements 409 and 410, two prisms 411 and 412, two actuators 413 and 414, wedge-shaped optical elements 415 and 416 driven by each actuator 413 and 414, two fixed wedges Mold optical elements 417 and 418.

  The wedge-shaped optical elements 415 and 418 are arranged such that their hypotenuses face each other, and their wedge angles are equal. Similarly, the wedge-shaped optical elements 416 and 417 are arranged so that the inclined surfaces face each other, and the wedge angles are equal.

(D-2) Operation of the Fourth Embodiment Next, the operation of the delay interferometer 1D of the fourth embodiment will be described with reference to FIG. 9 and FIG.

  The delay interferometer 1D includes two input port collimators 401 and 402 and has a two-input configuration. Therefore, the two lights input to the delay interferometer 1D from each input port are converted into parallel rays by the input port collimators 401 and 402, respectively. The parallel rays from the input port collimators 401 and 402 are input to the half mirror 407.

  The light beam from the input port collimator 401 is branched into two by the half mirror 407, one of the systems proceeds to the prism 411 side, and the other system travels to the wedge-shaped optical element 418 side.

  Further, an optical phase adjusting element 410 is disposed between the half mirror 407 and the prism 411, and the light beam traveling from the half mirror 407 to the prism 411 side is input to the optical phase adjusting element 410. The optical phase adjusting element 410 adjusts the phase of light by −π / 4, and the light beam input to the optical phase adjusting element 410 is input to the prism 411 with the light phase shifted by −π / 4. The

  On the other hand, the light beam from the input port collimator 402 is also bifurcated by the half mirror 407 into the prism 411 side and the wedge-shaped optical element 418 side.

  An optical phase adjustment element 409 is disposed between the half mirror 407 and the prism 411, and light traveling from the half mirror 407 to the prism 411 side is input to the optical phase adjustment element 409. The optical phase adjusting element 409 adjusts the phase of light by π / 4. The light beam input to the optical phase adjusting element 409 is input to the prism 411 with the light phase shifted by π / 4.

  Each light beam input to the prism 411 is reflected twice by the prism 411, output from a position slightly shifted from the input position of each light beam, and proceeds to the half mirror 408.

  On the other hand, the two light beams traveling from the half mirror 407 to the wedge-shaped optical element 418 pass through the wedge-shaped optical element 418 and further pass through the wedge-shaped optical element 415 fixed to the actuator 413. Further, the two light beams that have passed through the wedge-shaped optical element 415 pass through the wedge-shaped optical element 417 fixed to the actuator 414, pass through the wedge-shaped optical element 416, and are input to the prism 412.

  Each light beam input to the prism 412 is reflected twice by the prism 412 and output from a position slightly shifted from the input position of each light beam. Each light beam output from the prism 412 passes through the wedge-shaped optical elements 416, 417, 415, and 418 and is input to the half mirror 408.

  In the half mirror 408, the two light beams emitted from the prism 411 and the two light beams that have passed through the wedge-shaped optical element 418 are input, and in the same manner as in the first embodiment, the light of each light beam is transmitted. Bifurcation and interference occurs.

  Here, in the half mirror 408, four light interference signals are obtained. One is an interference signal between an input optical signal from the input port collimator 401 and a signal whose phase is shifted by −π / 4 by the optical phase adjustment element 410, and two is an input optical signal and light from the input port collimator 401. An interference signal with a signal whose phase is shifted by π / 4 by the phase adjustment element 409, and three signals that are an input optical signal from the input port collimator 402 and a signal whose phase is shifted by −π / 4 by the optical phase adjustment element 410 The four interference signals are interference signals between an input optical signal from the input port collimator 402 and a signal whose phase is shifted by π / 4 at the optical phase adjusting element 409.

  The four interference signals output from the half mirror 408 are respectively provided to the output port collimators 403 to 406 and output as parallel rays.

  Thus, conventionally, in the demodulation of a DQPSK signal, it was necessary to cause the first interferometer to interfere with a phase difference of π / 4 and the other interferometer to cause interference with a phase difference of −π / 4. However, according to the fourth embodiment, the optical phase adjusting elements 409 and 410 are provided, and the same operation can be realized by causing interference with two input signals.

(D-3) Effects of the Fourth Embodiment As described above, according to the fourth embodiment, a modulator that performs DQPSK demodulation can be realized by a single interferometer.

(E) Fifth Embodiment Next, a fifth embodiment of the delay interferometer of the present invention will be described with reference to the drawings.

  The fifth embodiment relates to the installation mode of the wedge-shaped optical element described in the first to fourth embodiments.

  In general, the accuracy of the delay interferometer is better when the interference light is brighter. Since the wedge-shaped optical element is usually coated with an antireflection film (AR film), it is designed so that the incident light is not reflected. Therefore, an interference signal can be obtained while maintaining brightness.

  However, the optical characteristics of the wedge-shaped optical element can change when the incident angle of light changes. In particular, when the incident angle exceeds 30 ° and light is incident, the reflectivity of TE waves and TM waves, which are polarized waves, greatly changes.

  For this reason, depending on the polarization state of the light incident on the wedge-shaped optical element for coarse adjustment, the reflectivity may change, loss may occur in the emitted light, and the accuracy of the delay interferometer may deteriorate.

  In order to avoid the above problems, (1) a method of forming an antireflection film according to the incident angle, (2) a method of forming a multilayer film and reducing the incident angle dependency, and the like can be considered. . However, the method (1) has a problem that the dependency on the incident angle increases and the tolerance corresponding to the error at the time of mounting decreases. Further, the method (2) may cause a problem that the cost of film formation becomes high. It is desired to solve the problem of reflection and transmission characteristics without applying a special treatment to the antireflection film of the wedge-shaped optical element.

  Therefore, the fifth embodiment exemplifies an embodiment in which the incident angle of light to the wedge-shaped optical element is made as small as possible to minimize loss.

(E-1) Configuration of Fifth Embodiment The fifth embodiment is characterized by an installation configuration of a wedge-shaped optical element fixed and a wedge-shaped optical element fixed to an actuator. For this reason, the installation configuration with two wedge-shaped optical elements will be mainly described. Other configurations are the same as the configurations described in the first to fourth embodiments. That is, the installation configuration of the two wedge-shaped optical elements described in the fifth embodiment can be applied to the first to fourth embodiments.

  FIG. 10 is a configuration diagram showing a configuration example when perpendicularly entering the wedge-shaped optical element. In FIG. 10, a wedge-shaped optical element 601 moves by driving an actuator (not shown). In FIG. 10, the alternate long and short dash line indicates the position of the wedge-shaped optical element 601 before movement, and the solid line indicates the position after movement.

  Note that the opposing surfaces of the wedge-shaped optical element 601 and the wedge-shaped optical element 602 are parallel, the wedge angles are both equal, and the refractive index n of each surface is 1.5.

  Light incident on the first surface of the wedge-shaped optical element 601 enters perpendicularly. When the light beam is emitted from the wedge-shaped optical element 601, the angle in the wedge-shaped optical element 601 at which the light beam is incident on the second surface is 30 °. At this time, in the air between the wedge-shaped optical element 601 and the wedge-shaped optical element 602, the angle is 48.6 °, which is approximately 49 °, so that the angle is very large. Note that the angle in the air is an angle incident on the first surface of the wedge-shaped optical element 602. As described above, since the incident angle to each surface of the wedge-shaped optical elements 601 and 602 is increased, loss due to reflection / transmission characteristics can be increased.

  Therefore, in the fifth embodiment, as illustrated in FIG. 11, the incident angle is selected so that light travels perpendicular to the plane that divides the apex angle of the wedge-shaped optical elements 611 and 612.

  FIG. 11 is a configuration diagram showing a configuration example when the incident angle is selected so that light travels perpendicularly to a plane that bisects the apex angle of the wedge-shaped optical element. In FIG. 11, a broken line indicates a plane that divides the apex angle into two.

  In FIG. 11, the incident angle of the light beam incident on the first surface of the wedge-shaped optical element 611 is 15 °, and the outgoing angle from the first surface is 10 °. Further, the angle at which the light beam is incident on the second surface of the wedge-shaped optical element 611 is 25 °, and the angle at which the light beam is emitted from the second surface into the air is 39 °. In the case of the example in FIG. 11, the incident angle to the wedge-shaped optical element can be reduced as compared with the example in FIG. 10.

  FIG. 12 is a configuration diagram showing a configuration example in the case where the incident angle is selected so that light travels perpendicularly to the plane that divides the apex angle of the wedge optical element into two in the wedge optical element.

  In FIG. 12, the incident angle of the light incident on the first surface of the wedge-shaped optical element 621 is 23 °, and is emitted at an angle of 15 °. Within the element of the wedge-shaped optical element 621, the light beam travels perpendicular to a plane that bisects the apex angle of the wedge-shaped optical element 621. The incident angle of the light beam on the second surface of the wedge-shaped optical element 621 is 15 °, and the emission angle into the air is 23 °.

  In the example of FIG. 11, the maximum incident angle is 39 °, whereas in the example of FIG. 12, the maximum incident angle is 23 °, which is smaller than in the example of FIG. In the case of FIG. 11, the loss of the emitted light is effectively suppressed, but it is understood that the loss of the emitted light is more effectively suppressed in the case of FIG.

  However, in the case of FIGS. 11 and 12, when the light beam is reflected by the prisms 613 and 623, returns to the wedge-shaped optical element again, and exits from the wedge-shaped optical element, the beam axis of the light beam is wedge-shaped. As the optical elements 611 and 612 move, they move in parallel (see “A” in FIGS. 11 and 12).

  In consideration of recombination with the optical fiber, such a movement of the light axis may cause problems such as failure to recombine with the optical fiber and increased loss. Further, as shown in FIGS. 11 and 12, when the prisms 613 and 623 are used, there is a problem that the light beam is inverted.

  FIG. 13 is a configuration diagram illustrating a structure of two wedge-shaped optical elements according to the fifth embodiment and a configuration example in the vicinity thereof. The configuration example shown in FIG. 13 includes at least a wedge-shaped optical element 501 driven by an actuator (not shown), a fixed wedge-shaped optical element 502, and reflecting portions 503 to 505.

  The wedge-shaped optical element 501 and the wedge-shaped optical element 502 have an arrangement configuration in which the incident angle is selected so that the light beam travels perpendicular to the plane that divides the apex angle into two in the optical element. The apex angles of the wedge-shaped optical element 501 and the wedge-shaped optical element 502 are equal, and the hypotenuses facing each other are parallel.

  The reflecting portions 503 to 505 are configured to fold back the light emitted from the second surface of the wedge-shaped optical element 502 to the wedge-shaped optical element 502 with a plurality of reflecting portions as a set. Although FIG. 13 illustrates a case where the three reflecting portions 503 to 505 are set as one set, the number of the reflecting portions is not particularly limited.

(E-2) Operation of Fifth Embodiment Next, the operation of the fifth embodiment will be described with reference to the drawings. FIG. 14 is an explanatory diagram for explaining the operation of the fifth embodiment. FIG. 14 illustrates a case where the wedge-shaped optical element 501 at the position represented by the alternate long and short dash line moves and the wedge-shaped optical element 501 moves to the position represented by the solid line.

  The light beam (1) is incident on the first surface of the wedge-shaped optical element 501. When the wedge-shaped optical element 501 is located at the position of the alternate long and short dash line before the movement, the light beam (1) enters the first surface, and the light beam (2) travels through the optical element. The light beam (2) enters the second surface of the wedge-shaped optical element 501, exits into the air, follows the optical path of the light beam (4), and exits the second surface of the wedge-shaped optical element 502.

  On the other hand, when the wedge-shaped optical element 501 is positioned at the position of the solid line after movement, the light beam (1) is incident on the first surface, and the light beam (3) travels through the optical element. The light beam (3) enters the second surface of the wedge-shaped optical element 501, exits into the air, follows the optical path of the light beam (5), and exits the second surface of the wedge-shaped optical element 502.

  At this time, in the light beam (4) and the light beam (5), the position of the traveling optical path changes with the movement of the position of the wedge-shaped optical element 501.

  Next, the light beam (4) and the light beam (5) travel toward the reflecting portion 503, are reflected by the reflecting portion 503, and travel toward the reflecting portion 504. Furthermore, the light beam (4) and the light beam (5) are reflected by the reflecting portion 504 and travel toward the reflecting portion 505. The light beam (6) and the light beam (7) reflected by the reflection unit 505 travel toward the wedge-shaped optical element 502.

  As described above, the traveling directions of the light beam (4) and the light beam (5) are reversed using the three reflecting portions 503 to 505. This reflection ensures that the positional relationship and distance between the two rays (4) and (5) remains unchanged.

  That is, the light beam (4) and the light beam (5) emitted from the second surface of the wedge-shaped light element 502 are parallel to the light beam (6) and the light beam (7) reflected by the reflection unit 505. Further, the distance between the light rays (4) and (5) emitted from the second surface of the wedge-shaped optical element 502 and the second surface of the wedge-shaped optical element 502 reflected by the reflecting portion 505 are incident on the second surface. The distance between ray (6) and ray (7) is the same.

  Therefore, the angles at which the light rays (4) and (5) are emitted from the second surface of the wedge-shaped optical element 502, and the angles at which the light beams (6) and (7) are incident on the second surface of the wedge-shaped optical element 502. And become equal.

  Accordingly, the light beams (6) and (7) follow the optical path shown in FIG. 14, and the angles at which the light beams (2) and (3) are emitted from the first surface of the wedge-shaped optical element 501 and the wedge-shaped optical element 501 are obtained. The angle of incidence on the first surface is equal. As a result, the beam axis before the movement of the wedge-shaped optical element 501 is the same as the beam axis after the movement.

  Here, the reflection parts 503 to 505 require that the light beam (4) and the light beam (5) are parallel to the light beam (6) and the light beam (7). The installation angles of the reflecting portions 503 to 505 can be widely applied if the light beam (4) and the light beam (5) can be parallel to the light beam (6) and the light beam (7).

  For example, in FIG. 14, the installation angle of the reflection unit 503 is α, the installation angle of the reflection unit 504 is β, and the installation angle of the reflection unit 505 is γ. In addition, the reflection parts 503 to 505 are assumed to be in a plane that bisects the apex angle of the wedge-shaped optical element 501. In this case, the reflectors 503 to 505 are installed so as to satisfy the relationship of β + γ = α + 8 °.

(E-3) Effect of Fifth Embodiment As described above, according to the fifth embodiment, the light beam (6) and the light beam (7) shown in FIG. It can be avoided. Further, the distance between the optical paths is determined by “x” shown in FIG. 14 if the incident angles are the same. In FIG. 14, since the incident positions of the light beam (1), the light beam (6), and the light beam (7) are different, the thickness of the wedge-shaped optical element through which the light beam travels is different.

  However, since x does not depend on the incident position or the difference in the thickness of the wedge-shaped optical element before and after the movement, the optical paths of the light beam (6) and the light beam (7) come close to each other after passing through the optical element. Therefore, it can couple | bond with the collimator lens mounted in the optical fiber end surface by installation of the reflection parts 503-505.

(F) Other Embodiments The configuration of the delay interferometer shown in the first to fifth embodiments described above is an example, and if the delayed interference of light described in the first to fifth embodiments can be performed. The configuration can be widely applied.

  For example, in the first to fifth embodiments, a plurality of wedge-shaped optical elements are illustrated as an example in which a wedge-shaped optical element fixed to the actuator and a fixed wedge-shaped optical element are arranged facing each other. The wedge-shaped optical elements may be moved by being fixed to each other.

  Also, for example, in the second embodiment, two wedge-shaped optical elements are included in one of the two optical paths branched by the half mirror 204 shown in FIG. 7 (the optical path traveling rightward in FIG. 7). A case where a set of coarse motion adjusting means and a reflective liquid crystal element are provided is illustrated. However, as described above, since the optical path length can be adjusted according to the apex angle of the wedge-shaped optical element, the device scale of the delay interferometer becomes large, but the coarse adjustment means and the reflection are provided in both of the two optical paths. It is good also as a structure provided with a type | mold liquid crystal element.

  In the first to fifth embodiments described above, the case where the present invention is applied to a Michelson interferometer is illustrated, but the present invention is not limited to the Michelson interferometer. For example, a delay unit including a set of a plurality of wedge-shaped optical elements may be applied to a Mach-Zehnder interferometer.

  The first to fifth embodiments have been described assuming an interferometer used in an optical communication system. However, the present invention is not limited to an interferometer used in an optical communication system, and is widely applied to an interferometer. Can do.

DESCRIPTION OF SYMBOLS 101 ... Input port collimator, 102 and 103 ... Output port collimator, 104 and 105 half mirror, 106 and 107 ... Prism, 108 and 109 ... Actuator, 110 and 111 ... Wedge type optical element, 112 and 113 ... Wedge type optical element,
DESCRIPTION OF SYMBOLS 201 ... Input port collimator, 202 and 203 ... Output port collimator, 204 and 205 ... Half mirror, 206 ... Prism, 207 ... Actuator, 208 ... Wedge type optical element, 209 ... Wedge type optical element, 210 ... Reflective type liquid crystal element, 211 ... Wedge type optical element 211,
DESCRIPTION OF SYMBOLS 301 ... Input port collimator, 302 and 303 ... Output port collimator, 304 ... Polarization plane beam splitter (PBS), 305 and 306 ... Half mirror, 307 ... Prism, 308 ... Actuator, 309 ... Wedge type optical element, 310 ... Wedge type Optical elements, 311 and 312... Half-wave plate, 313... Reflective liquid crystal element, 314... Wedge-shaped optical element, 315... Optical path adjusting element, 316 and 317.
401 and 402 ... input port collimator, 403 to 406 ... output port collimator, 407 and 408 ... half mirror, 409 and 410 ... optical phase adjusting element, 411 and 412 ... prism, 413 and 414 ... actuator, 415 and 416 ... wedge type Optical elements 417 and 418 ... wedge-shaped optical elements, 501 ... wedge-shaped optical elements, 502 ... wedge-shaped optical elements,
1A to 1D: Delay interferometer.

Claims (6)

Branching means for branching the input light beam into two;
A first wedge-shaped optical element arranged in the first optical path and / or the second optical path of the light beam branched by the branching means, and having the same apex angle with the first drive unit; A second wedge-shaped optical element, wherein the second wedge-shaped optical element driven by the first drive unit is opposed to the first wedge-shaped optical element. Coarse motion adjusting means for performing coarse motion adjustment of the optical path length of the light traveling in the first optical path and / or the second optical path by moving in parallel with the element;
A third wedge-shaped optical element which is arranged in the first optical path and / or the second optical path of the light beam branched by the branching means, and has the same apex angle as the second driving unit; And a fourth wedge-shaped optical element, wherein the fourth wedge-shaped optical element driven by the second drive unit is opposed to the third wedge-shaped optical element. Fine movement adjustment means for performing fine movement adjustment of the optical path length of the light traveling in the first optical path and / or the second optical path by moving in parallel with the element;
The first light beam traveling in the first optical path and the second light beam traveling in the second optical path, which have been subjected to the fine movement adjustment by the fine movement adjustment means and the coarse movement adjustment by the coarse movement adjustment means, are branched. And a branch recombination means for recombining and outputting based on the respective branched lights of the first light beam and the second light beam. The branching means receives two light beams and splits each light beam into two.
First phase shift adjusting means, which is arranged between the branching means and the branch recombining means, and adjusts the optical phase of the first light beam for one of the two light beams by π / 4. When,
A first phase shift adjustment that is arranged between the branching means and the branch recombination means and adjusts the optical phase of the first light beam with respect to the other of the two light beams by −π / 4. Further comprising means and
The branch recombination means performs the first phase shift with respect to each second light beam for each light beam that has undergone the fine movement adjustment by the fine movement adjustment means and the coarse movement adjustment by the coarse movement adjustment means. 2. The delay interferometer according to claim 1, wherein each of the light beams from the adjusting unit and the second phase adjusting unit is caused to interfere with a phase difference of π / 4 and −π / 4. Branching means for branching the input light beam into two;
An optical phase control for controlling the optical phase of the light beam by causing the reflective liquid crystal element to be inclined and causing the light beam traveling on the first optical path branched by the branching means to be reflected by the reflective liquid crystal element. Means,
It is interposed between the branching means and the optical phase control means, and comprises a drive unit, and a first wedge-type optical element and a second wedge-type optical element having the same apex angle. The second wedge-shaped optical element driven by the drive unit moves in parallel to the opposed first wedge-shaped optical element, so that the light beam from the branching unit and the above-mentioned Coarse motion adjusting means for performing coarse motion adjustment of the optical path length of the light beam reflected and returned by the optical phase means;
Reflecting means for totally reflecting the light beam traveling in the other second optical path branched by the branching means;
The first light beam reflected by the reflecting means and the second light beam output from the coarse motion adjusting means are branched and recombined based on the branched lights of the first light beam and the second light beam. And a branch recombination means for outputting the delayed interferometer. Provided in front of the branching means is a polarized light beam separating means for separating the input light beam into two parallel light beams perpendicular to the plane of polarization,
The branching means bifurcates each parallel light from the polarized light separating means;
The branching / recombining means causes the parallel rays to interfere separately using the first ray for each parallel ray and the second ray for each parallel ray. The delay interferometer according to claim 3.   The first wedge-shaped optical element and the second wedge-shaped optical element are incident on a plane perpendicular to a plane that bisects the apex angle of the first wedge-shaped optical element and the second wedge-shaped optical element. And the first wedge-shaped optical element and the second wedge-shaped optical element are arranged so that an incident angle of a light beam is minimized. The delay interferometer described in 1.   6. An optical path correction unit that corrects a deviation of an optical path of light beams emitted from the first wedge-type optical element and the second wedge-type optical element using a plurality of reflection units. The delay interferometer described in 1.

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