JP6926534B2 - Optical 90 degree phaser, SSB modulator and optical heterodyne orthogonal detection laser radar - Google Patents

Description

The present invention relates to an optical 90 degree phaser, an SSB (Single Side Band) modulator and an optical heterodyne orthogonal detection laser radar.

Conventionally, various optical devices that utilize light having a phase difference of 90 degrees have been proposed.

For example, Patent Document 1 discloses an optical transmission device that combines light having a phase difference of 90 degrees.

Japanese Unexamined Patent Publication No. 2013-26758

FIG. 8 shows a functional block diagram showing the configuration of the optical transmission device 80 according to Patent Document 1. As shown in FIG. 8, the optical transmitter 80 includes an optical phase modulator 81 and a control loop 82.

The optical phase modulator 81 branches the light of the input light source 83, and inputs one to the first optical phase modulator 84 and the other to the second optical phase modulator 85. The output light of the second optical phase modulation unit 85 is further input to the optical phase shift unit 86. Then, the output light of the first optical phase modulation unit 84 and the output light of the optical phase shift unit 86 are combined to generate a transmission light signal output to the transmission line.

At this time, the control loop 82 monitors the transmitted optical signal and adds it to the micromodulation signal generator 93 in the adder 94 to obtain a control signal that causes the phase difference in the optical phase shift unit 86 to be 90 degrees. Generates a phase shift amount control signal to be controlled.

Therefore, the control loop 82 includes a photodiode 87, a peak detection unit 90, a synchronous detection unit 91, a control unit 92, a micromodulation signal generator 93, an adder 94, and a signal correction unit 95. Further, the signal correction unit 95 includes an LPF (Low Pass Filter) 88 and a correction adder 89.

The photodiode 87 monitors the transmitted optical signal. The signal correction unit 95 removes the average intensity fluctuation component from the frequency of the micromodulation signal output from the micromodulation signal generator 93 included in the transmission optical signal. The peak detection unit 90 detects the amplitude of the output signal of the signal correction unit 95 and outputs the detection signal to the synchronous detection unit 91. The synchronous detection unit 91 synchronously detects the detection signal with the micromodulation signal output from the micromodulation signal generator 93, and outputs the synchronous detection output to the control unit 92. The control unit 92 generates a phase shift amount control signal for controlling the phase shift amount of the optical phase shift unit 86 to 90 degrees based on the synchronous detection output.

As described above, in the conventional optical transmission device 80, in order to generate light having a phase difference of 90 degrees, it is necessary to have a complicated configuration having a plurality of functional parts as shown in, for example, the control loop 82.

The present invention has been made in view of the above-mentioned problems, and is an optical 90-degree phase device and an optical 90-degree phase device that generate light having a phase difference of 90 degrees with a simpler configuration than the conventional one. It is an object of the present invention to provide an SSB modulator and an optical heterodyne orthogonal detection laser radar using the above.

In order to achieve the above object, the 90-degree optical phase device according to claim 1 propagates the light output from the laser light source to a first waveguide and a second waveguide that propagate the light output from the laser light source in only one direction, respectively. A first branch that branches, a second branch that branches light propagating through the first waveguide into a third waveguide and a fourth waveguide, the first waveguide, and the first and supplies the same amount of heat to 4 of the waveguide, and a modulator for modulating the light propagating through the first waveguide and the fourth waveguide, modulated by the modulation unit, the fourth waveguide The light detection unit that detects the amount of interference light between the light propagating in the second waveguide and the light propagating in the second waveguide, and the light amount of the interference light detected by the light detection unit are reduced. A control unit for controlling the amount of heat supplied from the modulation unit to the first waveguide and the fourth waveguide is provided , and the waveguide branched from the second waveguide and the third waveguide are provided. Lights having a phase difference of 90 degrees from each other are output .

The optical 90-degree phase device according to claim 2 is a first heating in the modulation unit that supplies heat to the first waveguide and the fourth waveguide by supplying a voltage or a current. The shape of the region and the shape of the second heating region are the same, and the shape of the first waveguide passing through the first heating region and the shape of the fourth conduction path passing through the second heating region are the same. The shape of the waveguide is the same, so that the control unit reduces the amount of the interference light detected by the photodetector and supplies the same voltage or current to each of the heating regions. Controls the modulation unit.

The optical 90-degree phase device according to claim 3 connects the first heating region and the second heating region of the modulation unit in series, and the control unit connects the first heating region in series. The modulation unit is controlled so as to supply a voltage or a current to the heating region and the second heating region.

In the 90-degree optical phase device according to claim 4, the first heating region and the second heating region of the modulation unit are composed of a heater.

The 90-degree optical phase device according to claim 5 includes a first branch that propagates the light output from the laser light source in only one direction and a first branch that branches into the second waveguide. A second branch portion that branches light propagating through the first waveguide into a third waveguide and a fourth waveguide, and a PN formed in the first waveguide and the fourth waveguide. A modulation section that supplies light to a ridge portion having a junction, a PP junction, or an NN junction to modulate light propagating through the first waveguide and the fourth waveguide, and a modulation section modulated by the modulation section. The light detection unit that detects the amount of interference light between the light propagating through the fourth waveguide and the light propagating through the second waveguide, and the light amount of the interference light detected by the light detection unit. The second guide is provided with a control unit for controlling the current supplied from the modulation unit to the first waveguide and each ridge portion formed in the fourth waveguide. Light having a phase difference of 90 degrees from each other is output from the waveguide branched from the waveguide and the third waveguide.

The SSB modulator according to claim 6 is the light propagating through the optical 90-degree phaser according to any one of claims 1 to 5 and the second waveguide of the optical 90-degree phaser. A first equilibrium modulator that modulates light, a second equilibrium modulator that modulates light propagating through the third waveguide of the optical 90-degree phaser, the first equilibrium modulator and the second equilibrium modulator. The phase of the signal source that inputs the carrier signal to each of the balanced modulators and the phase of the carrier signal that is input to the second balanced modulator is 90 with respect to the phase of the carrier signal that is input to the first balanced modulator. It is equipped with a phaser that shifts the degree.

The optical heterodyne orthogonal detection laser radar according to claim 7 is an optical phased array antenna for radiation that adjusts the radiation angle of light by supplying heat to each of a plurality of waveguides and emits light to an object to be measured. The first method of adjusting the light receiving angle by supplying heat to each of the plurality of waveguides and receiving the light reflected by the measurement object among the light emitted from the radiation optical phased array antenna. The light receiving optical phased array antenna and the second light receiving optical phased array antenna, the optical 90 degree phase device according to any one of claims 1 to 5, and the said optical 90 degree phase device. A first optical detector that detects the amount of interference light between the light propagating in the waveguide 2 and the light received by the first light-receiving optical phased array antenna, and the first optical detector of the 90-degree optical phase device. A second optical detector that detects the amount of interference light between the light propagating in the waveguide 3 and the light received by the second light receiving optical phased array antenna, the first light detector, and the above. A computing device that performs complex Fourier transform on each detection result of the second optical detector and calculates the Doppler frequency for the measurement object is provided.

As described above, according to the optical 90-degree phaser according to the present invention, the SSB modulator using the optical 90-degree phaser, and the optical heterodyne orthogonal detection laser radar, the configuration is 90 degrees with a simpler configuration than before. It has the effect of being able to generate light with a phase difference.

It is a figure which shows the structural example of the optical 90 degree phase device. It is a figure which shows an example of the shape of a thin film heater. It is a figure which shows an example of the layer structure in the case where an optical 90 degree phase apparatus is composed of an optical integrated circuit. It is a figure which shows an example of the layer structure of an optical modulator. It is a figure which shows the structural example of the SSB modulator using the optical 90 degree phase apparatus. It is a figure which shows an example of the light propagation path in an optical heterodyne orthogonal detection laser radar using an optical 90 degree phaser. It is a functional block diagram which shows the structural example of the optical heterodyne orthogonal detection laser radar. It is a functional block diagram which shows the structural example of the conventional optical transmission device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration example of an optical 90-degree phase device 10 according to the present embodiment. _{Light output from a laser light source (hereinafter referred to as "input light P 1} "), which is not shown, such as a semiconductor optical amplifier (SOA), which is an example of a gain medium, is connected to the input end 11 of the 90-degree optical phase device 10. ) Is entered. _{The input light P 1} input to the input terminal 11 is input to a branch portion 12 configured by a branching device such as an optical coupler, and is divided into two branches: light propagating in the waveguide 13 and light propagating in the waveguide 14. Will be done. Here, the branch portion 12 is an example of the first branch portion, the waveguide 14 is an example of the first waveguide, and the waveguide 13 is an example of the second waveguide.

The light propagating in the waveguide 13 is further input to the branching portion 19, and is further branched into two, a light propagating in the waveguide 18 and a light propagating in the waveguide 20. Then, the light propagating in the waveguide 20 is output from the optical 90-degree phase controller 10 as the _{output light P 2.} That is, the output light P ₂ is light having the same phase as the input light P _1.

On the other hand, the light branched at the branch portion 12 and propagating in the waveguide 14 is further input to the branch portion 15 and is further branched into two, a light propagating in the waveguide 16 and a light propagating in the waveguide 21. Here, the branch portion 15 is an example of the second branch portion, the waveguide 21 is an example of the third waveguide, and the waveguide 16 is an example of the fourth waveguide.

Then, light propagating through the waveguide 21 is output from the optical 90-degree phase shifter 10 as output light P _3.

The light propagating in the waveguide 16 and the light propagating in the waveguide 18 are input to the combiner portion 17 configured by a combiner such as an optical coupler, and propagate the light propagating in the waveguide 16 and the light propagating in the waveguide 18. The interfering light obtained by the combined wave with the light is used in the photodetector 22 composed of, for example, a PN junction photodiode that detects the light and outputs a voltage value or a current value according to the amount of the detected light. Entered. Here, as an example, the photodetector 22 will be described as outputting a current value according to the amount of light, but a voltage value corresponding to the amount of light may be output instead of the current value. The photodetector 22 is an example of a photodetector.

Further, in the waveguide 14 and the waveguide 16, a thin film heater 26 is arranged in which a part thereof extends along the waveguide 14 and the waveguide 16 and covers the waveguide 14 and the waveguide 16. A voltage is supplied from the control unit 23 to both ends of the thin film heater 26 to heat the waveguide 14 and the waveguide 16.

The control unit 23 includes an AD conversion circuit 24 and a drive circuit 25, and the AD conversion circuit 24 uses a current value output from the photodetector 22 as a digital value of, for example, N bits (N is an integer). Convert to a value. The drive circuit 25 receives the current value output from the AD conversion circuit 24, and controls the voltage supplied to the thin film heater 26 according to the received current value, that is, the amount of light detected by the photodetector 22.

By heating the waveguide 14 and the waveguide 16 with the thin film heater 26, the refractive indexes of the waveguide 14 and the waveguide 16 change. Therefore, the waveguide 14 and the waveguide 16 are changed according to the amount of heat supplied from the thin film heater 26. The phase of the light propagating 16 changes. That is, the thin film heater 26 is an example of a modulator that modulates light.

FIG. 2 is a diagram showing in detail the shape of the thin film heater 26. As shown in FIG. 2, the thin film heater 26 includes a rectangular heating portion 26A extending along the waveguide 16, a rectangular heating portion 26B extending along the waveguide 14, and a heating portion 26A in the longitudinal direction. And has a rectangular heating portion 26C which is arranged so as to be orthogonal to each longitudinal direction of the heating portion 26B and connects one end of each of the heating portion 26A and the heating portion 26B. Further, the thin film heater 26 is connected to the other end of the heating portion 26A, it is connected to the control unit 23 at the connection point K _3, a heating unit 26D supplied with the voltage from the control unit 23, other heating unit 26B is connected to the end, it is connected to the control unit 23 at the connection point K _2, a heating unit 26E supplied with voltage from the control unit 23.

Here, the length of the heating portion 26A along the waveguide 16 (i.e., the width of the heating section 26A) the length of the L _A, heating unit 26B along the waveguide 14 (i.e., the width of the heating unit 26B) L _B is the same length, the length of the heating portion 26A in a direction orthogonal to the direction along the waveguide 16 (i.e., the depth of the heating portion 26A) W _a and the direction perpendicular to the direction along the waveguide 14 the length of the heating section 26B in (i.e., the depth of the heating unit 26B) and W _B are the same length.

The width L _A and the depth W _A respectively orthogonal directions (hereinafter, referred to as "thickness direction of the waveguide 16") length of the heating section 26A in (i.e., the thickness of the heating portion 26A) and H _A, width L _B and the depth W _B and respectively orthogonal directions (hereinafter, referred to as "waveguide thickness direction of the 14") length of the heating section 26B in (i.e., the thickness of the heating portion 26B) also H _B, the same length be.

That is, in the thin film heater 26, the heating unit 26A and the heating unit 26B have the same shape. Here, "the same shape" means that the width, depth, and thickness of the objects are the same, and the two objects overlap each other. Similarly, the heating unit 26D and the heating unit 26E have the same shape.

Further, each part of the thin film heater 26, that is, the heating parts 26A, 26B, 26C, 26D, and 26E are made of the same material. That is, the resistance values in the heating unit 26A and the heating unit 26B are the same.

Further, the shape and material of the waveguide 16 in the range covered by the heating portion 26A and the shape and material of the waveguide 14 in the range covered by the heating portion 26B are also configured in the same manner.

Since the heating unit 26A and the heating unit 26B are connected in series by the heating unit 26C, when a voltage is supplied from the control unit 23 to the thin film heater 26, a current corresponding to the supplied voltage value flows to the thin film heater 26. The same amount of heat is supplied to the waveguide 16 in the range covered by the heating section 26A and the waveguide 14 in the range covered by the heating section 26B, respectively. Then, the phase of the light propagating in the waveguide 14 and the waveguide 16 changes according to the amount of heat supplied from the thin film heater 26.

Since the light propagating in the waveguide 16 and the waveguide 18 is _{the branched light of the input light P 1} , the phase of the light propagating in the waveguide 16 is shifted by 180 degrees with respect to the phase of the light propagating in the waveguide 18. Then, the amount of interference light between the light propagating in the waveguide 16 and the light propagating in the waveguide 18 detected by the photodetector 22 is the smallest.

In this case, since the same amount of heat is supplied to the waveguide 14 and the waveguide 16 by the thin film heater 26, the refractive indexes of the light in the waveguide 14 and the waveguide 16 are the same. That is, the phase of the light at _{the branch point K 1} of the waveguide 14 and the waveguide 16 has a phase difference of half of 180 degrees, that is, 90 degrees with respect to _{the input light P 1.}

Therefore, the control unit 23 controls the voltage value supplied to the thin film heater 26 while monitoring the current value output from the photodetector 22 so that the amount of light detected by the photodetector 22 is minimized. The output light P _{3 of the} waveguide 21 branched from the branch point K ₁ becomes light having a phase difference of 90 degrees with respect to the output light P _2.

Regarding the arrangement of the waveguide 14, the waveguide 16 and the thin film heater 26, in the example of FIG. 1, the shape of the thin film heater 26 and the waveguide 14 and the waveguide 16 in the portion covered by the thin film heater 26 are respectively. The shape is axisymmetric with the line segment G along the longitudinal direction of the heating portion 26A as the axis of symmetry, passing through the center of the heating portion 26C, for example.

In this way, the waveguide 14 and the waveguide so that the shape of the thin film heater 26 and the shapes of the waveguide 14 and the waveguide 16 of the portion covered by the thin film heater 26 are line-symmetrical with respect to a specific line segment. By arranging the 16 and the thin film heater 26, the amount of heat supplied from the thin film heater 26 to the waveguide 14 and the waveguide 16 can be easily made the same.

However, it is not always necessary to arrange the waveguide 14, the waveguide 16 and the thin film heater 26 at positions that are line-symmetric with respect to a specific line segment, and the shapes of the heating unit 26A and the heating unit 26B are the same, and heating is performed. The shape of the waveguide 16 in the range covered by the portion 26A and the shape of the waveguide 14 in the range covered by the heating portion 26B may be the same.

FIG. 3 is a diagram showing an example of a layer structure when the optical 90-degree phase device 10 is configured as an optical integrated circuit 30. Note that FIG. 3 is not a diagram showing the physical positional relationship between the thin film heater 26 and the waveguide 14 and the waveguide 16 in FIG. 1, but is a diagram instead of a waveguide such as the waveguide 14 and the waveguide 16. It is a figure which showed the positional relationship between the thin film heater 26 and the waveguide 33 by using the waveguide 33 for convenience which is used only for the explanation of 3.

The optical integrated circuit 30 is configured to include, for example, a Si substrate 31, a SiO2 (silicon dioxide) layer 32 formed on the substrate 31, and a waveguide 33. In the optical integrated circuit 30, the thin film heater 26 is arranged on the surface opposite to the substrate 31, for example, and is configured to heat the waveguide 33.

Further, in the example of the optical 90-degree phase device 10 shown in FIG. 1, a thin film heater 26 was used as an example of the modulation unit, but as in the optical modulator 40 shown in FIG. 4, a ridge that functions as a light waveguide. A current may be injected from the N electrode 44a and the P electrode 44b connected to the portion 49 to control the refractive index of the light propagating in the ridge portion 49.

The light modulator 40 shown in FIG. 4 includes, for example, a Si substrate 41 and SiO2 layers 42 and 43 formed on the substrate 41. Then, the N-Si region 48a, which is an N-doping region in which N-type impurities are diffused (doped) in Si less than the specified amount so as to be sandwiched between the SiO2 layers 42 and 43, and the P-type impurities less than the specified amount in Si. A P-Si region 48b, which is a P-doped region doped with The N-Si region 48a and the P-Si region 48b each extend to the central portion of the ridge portion 49 to form a PN junction within the ridge portion 49.

The N + Si region 47a, which is an N + doped region in which Si is doped with more N-type impurities than the specified amount, is laminated on the N-Si region 48a, and the P-Si region 48b is laminated with more P-type impurities than the specified amount on Si. The P + Si region 47b, which is the doped P + doped region, is laminated. Then, the N + Si region 47a is connected to the N electrode 44a via the via 46a, and the P + Si region 47b is connected to the P electrode 44b via the via 46b.

In the light modulator 40 having the above configuration, when a current is injected between the N electrode 44a and the P electrode 44b, the N—Si region 48a and the P-Si region 48b are formed by the carrier plasma effect. The refractive index at the PN junction changes, and phase modulation of the light propagating through the ridge portion 49 is performed.

Therefore, one part of the waveguide 14 and one part of the waveguide 16 are configured by the same length as the ridge portion 49 of the light modulator 40 shown in FIG. 4, respectively, and the light is refracted in the waveguide 14 and the waveguide 16. The control unit 23 may control the currents injected into the N electrode 44a and the P electrode 44b of the respective light modulators 40 so that the rates are the same.

In the above example, the light modulator 40 having a PN junction was used, but the light modulator 40 having a PP junction in which both the region 48a and the region 48b were doped with P-type impurities, or the N-type impurities in both the region 48a and the region 48b were used. A light modulator 40 having a doped NN junction may be used.

Since the heat capacity has non-linearity, the heating characteristics of the waveguides 14 and 16 by the thin film heater 26 are also non-linear. Therefore, when the light modulator 40 is used, the refractive index of light can be controlled more accurately than when the thin film heater 26 is used.

<Application Example 1 of Optical 90 Degree Phaser 10>
FIG. 5 is a diagram showing a configuration example of the SSB modulator 50 using the optical 90-degree phase controller 10.

As shown in FIG. 5, the SSB modulator 50 includes an optical 90 degree phaser 10, a main Mach-Zehnder interferometer 34, a first sub-Mach-Zehnder interferometer 36, a second sub-Mach-Zehnder interferometer 38, a carrier signal source 35 and A 90-degree phase device 39 is provided. Here, the first sub-Mach-Zehnder interferometer 36 is an example of the first balanced modulator, and the second sub-Mach-Zehnder interferometer 38 is an example of the second balanced modulator.

_{The output light P 2} of the 90-degree light phase device 10 propagating in the waveguide 20 is input to the first sub-Mach-Zehnder interferometer 36 and branched into light propagating in the waveguide 36-1 and the waveguide 36-2. _{On the other hand, the output light P 3} of the light 90-degree phase device 10 propagating in the waveguide 21 is input to the second sub-Mach-Zehnder interferometer 38 and branched into light propagating in the waveguide 38-1 and the waveguide 38-2. NS.

In the waveguide 36-2, a modulation unit 36-3 that modulates the light with the carrier signal output from the carrier signal source 35 is arranged, and the light propagating through the waveguide 36-1 and the light propagating through the waveguide 36-2 are propagated. The combined light with the modulated light propagates through the waveguide 28.

On the waveguide 38-1, a modulator 38-3 that modulates light with a carrier signal output from a carrier signal source 35 that is 90 degrees out of phase with the 90-degree phase device 39 is arranged, and the waveguide 38-1 is provided. The combined light of the modulated light propagating in the waveguide and the light propagating in the waveguide 38-2 propagates in the waveguide 29.

The combined light propagating in the waveguide 28 and the combined light propagating in the waveguide 29 are further combined by the main Mach-Zehnder interferometer 34, and the output of the main Mach-Zehnder interferometer 34 is the SSB modulated light P ₄ and the SSB modulator 50. Is output from.

In the SSB modulator 50, since it is necessary to input light (signal wave) having a phase difference of 90 degrees to the first sub-Mach-Zehnder interferometer 36 and the second sub-Mach-Zehnder interferometer 38, the optical 90-degree phaser 10 The output light P ₂ and the output light P ₃ of the above may be input respectively.

Here, the first sub-Mach-Zehnder interferometer 36 and the second sub-Mach-Zehnder interferometer 38 are examples of balanced modulators that output a sideband from the input signal wave and carrier signal.

Instead of the first sub-Mach-Zehnder interferometer 36, the second sub-Mach-Zehnder interferometer 38, and the main Mach-Zehnder interferometer 34, LN modulators that utilize the change in the refractive index due to the Pockels effect of the LiNbO3 crystal may be used. good.

<Application Example 2 of Optical 90 Degree Phaser 10>
FIG. 6 is a diagram showing an example of a light propagation path in an optical heterodyne orthogonal detection laser radar 70 (hereinafter referred to as “laser radar 70”) using an optical 90-degree phase device 10.

As shown in FIG. 6, the laser radar 70 includes an optical 90-degree phased array 10, a transmitting optical phased array antenna 52 (hereinafter referred to as “optical phased array 52”), and a receiving first optical phased array antenna 62 (hereinafter, hereinafter referred to as “optical phased array 52”). It includes an "optical phased array 62"), a second optical phased array antenna 72 for reception (hereinafter referred to as "optical phased array 72"), an optical detector 56, and an optical detector 57. Here, the optical phased array 52 is an example of a radiation optical phased array antenna, the optical phased array 62 is an example of a first light receiving optical phased array antenna, and the optical phased array 72 is a second light receiving optical phased. This is an example of an array antenna.

In the laser radar 70, the input light P ₁ is branched into two, one input light P ₁ is input to the optical phased array 52, and the other input light P ₁ is input to the optical 90 degree phase device 10.

Here, the optical phased array 52 means that the input light P ₁ is branched into a plurality of waveguides (8 lines from 52-1 to 52-8 in the example of FIG. 6) by an optical coupler (not shown), and the waveguide 52- 1 is an example of an optical antenna that emits light from the end of the waveguide 52-8. Hereinafter, the waveguides 52-1 to 52-8 may be collectively referred to as “wavewave 52”.

A diffraction grating 53 is provided at the end of the waveguide 52 on the side that emits light, and the input light P ₁ propagating through the waveguide 52 is used as the output light P _1A from the diffraction grating 53 to the object to be measured Q. It is radiated toward.

Thin film heaters 54A and 54B for heating each of the waveguides 52 are attached to the optical phased array 52, and by heating the waveguides 52 with the thin film heaters 54A and 54B, the respective light propagating through the waveguides 52. The refractive index of the light can be changed to change the radiation angle of the light emitted from the diffraction grating 53.

The thin film heater 54A has a shape in which the area for heating the waveguide 52 increases as it progresses from the waveguide 52-1 to the waveguide 52-8 (as an example, it is represented by a triangular shape in FIG. 6). .. On the contrary, the thin film heater 54B has a shape in which the area for heating the waveguide 52 becomes smaller as it progresses from the waveguide 52-1 to the waveguide 52-8.

Since the refractive index of light changes according to the amount of heat supplied to the waveguide 52 (the amount of heat generated by the thin film heaters 54A and 54B), the phase of the light radiated from each of the waveguides 52 changes to output the light. The propagation direction of light P _{1A changes.} Therefore, the output light P _1A can be emitted toward the measurement object Q.

The optical phased arrays 62 and 72 receive the _{reflected light P 5} reflected by the measurement object Q among the _{output light P 1A emitted toward the measurement object Q.}

The optical phased arrays 62 and 72 have the same structure as the optical phased array 52 except that the light propagation directions are opposite to those of the optical phased array 52.

That is, the optical phased array 62 is equipped with thin film heaters 64A and 64B for heating each of the waveguides 62-1 to 62-8 (hereinafter referred to as “widden paths 62”), and the thin film heaters 64A. By heating the waveguide 62 with 64B, the refractive index of the waveguide 62 can be changed, and the light receiving angle of the light received by the diffraction grating 63 can be changed.

Further, the optical phased array 72 is equipped with thin film heaters 74A and 74B for heating each of the waveguides 72-1 to 72-8 (hereinafter referred to as “widden paths 72”), and the thin film heaters 74A. By heating the waveguide 72 with the 74B, the refractive index of the waveguide 72 can be changed, and the light receiving angle of the light received by the diffraction grating 73 can be changed.

_{The reflected light P 5} received by the optical phased array 62 _{is combined with the output light P 2} of the 90-degree light phase device 10, and the interference light due to the combined wave is input to the light detector 56. _{Further, the reflected light P 5} received by the optical phased array 72 _{is combined with the output light P 3} of the 90-degree light phase device 10, and the interference light due to the combined wave is input to the photodetector 57. Here, since the output light P ₂ and the output light P ₃ have a phase difference of 90 degrees due to the light 90 degree phase device 10, if a cosine wave is input as _{the input light P 1 of the laser radar 70, the output light P 2} Can be set as a cosine wave and the output light P ₃ can be set as a sine wave.

That is, the photodetector 56, a cosine wave to the reflected light P ₅ (output light P ₂₎ is light multiplied is inputted to the optical detector 57, a sine wave to the reflected light P ₅ (output light P ₃ The light multiplied by) is input. The photodetector 56 is an example of a first photodetector, and the photodetector 57 is an example of a second photodetector.

FIG. 7 is a diagram showing an example of a functional block of the laser radar 70.

Follow the instructions of the timing control circuit 106, drive circuit 110 drives the laser light source 100 to irradiate the input light P _1. At this time, the timing control circuit 106 controls the drive circuit 108 to drive the thin film heaters 54A and 54B of the optical phased array 52, the thin film heaters 64A and 64B of the optical phased array 62, and the thin film heaters 74A and 74B of the optical phased array 72. _{Then, the radiation angle of the output light P 1A} in the optical phased array 52 and the light _{receiving angle of the reflected light P 5} in the optical phased arrays 62 and 72 are adjusted.

_{Further, the input light P 1} emitted from the laser light source 100 is input to the light 90-degree phase device 10, the reflected light P ₅ received by the optical phased array 62, and the output light (cosine wave) P of the light 90-degree phase device 10. ₂ and 2 are combined by the combiner 102 and input to the detection circuit 112 including the light detector 56. _{Further, the reflected light P 5} received by the optical phased array 72 and the output light (sine wave) P _{3 of the} light 90 degree phase device 10 are combined by the combiner 104, and are combined with the detection circuit 114 including the photodetector 57. Entered.

The detection circuit 112 detects _{the amount of the first interference light due to the reflected light P 5} and the cosine wave P ₂ , removes the noise component included in the detection result by the BPF (Band Pass Filter) 116, and then the first interference light. The amount of light of is input to the ADC (Analog to Digital Converter) 120.

Similarly, the detection circuit 114 detects _{the amount of the second interference light due to the reflected light P 5} and the sine wave P ₃ , removes the noise component included in the detection result by the BPF 118, and then determines the amount of the second interference light. It is input to the ADC 122.

The amount of light of the first interference light represented as a digital value in the ADC 120 and the amount of light of the second interference light represented as a digital value in the ADC 122 are both input to the complex FFT124, which is an example of the arithmetic unit, and are complex in the complex FFT124. The Fourier transform is performed. The complex FFT124 calculates the Doppler frequency with respect to the measurement object Q from the calculation result of the complex Fourier transform.

Then, the laser radar 70 calculates the distance from the Doppler frequency to the measurement object Q, the relative speed, and the like by using a known method.

As described above, according to the light 90-degree phase device 10 according to the present embodiment, the interference between the modulation unit using the thin film heater 26, the unmodulated light which is the branch light from the same light source, and the light modulated by the modulation unit. The output light P having a phase difference of 90 degrees is used by the light detector 22 that detects the amount of light and the control unit 23 that controls the amount of light modulation in the modulation unit so that the amount of interference light is minimized. ₂ and output light P ₃ are generated. That is, the optical 90-degree phase device 10 can generate _{output lights P 2} and P ₃ having a phase difference of 90 degrees with a simpler configuration than the conventional one.

Therefore, the configuration of the SSB modulator 50 using the optical 90-degree phaser 10 and the laser radar 70 using the optical 90-degree phaser 10 can be made simpler than the conventional SSB modulator and laser radar, respectively. Therefore, the size of the device and the cost can be reduced.

The present invention is not limited to the above-described embodiment, and various modifications and applications can be made without departing from the gist of the present invention.

For example, the control unit 23 of the light 90-degree phase device 10 controls the voltage supplied to the thin film heater 26 to control the refractive index of the light propagating through the waveguides 14 and 16, but the current supplied to the thin film heater 26 is controlled. Needless to say, it may be controlled.

10 ... Optical 90 degree phasers 22, 56, 57 ... Optical detector 23 ... Control unit 26 ... Thin film heater 30 ... Optical integrated circuit 34 ... Main Mach-Zehnder interferometer 35.・ ・ Carrier signal 36 ・ ・ ・ 1st sub-Mach-Zehnder interferometer 38 ・ ・ ・ 2nd sub-Mach-Zehnder interferometer 39 ・ ・ ・ 90 degree phaser 40 ・ ・ ・ Optical modulator 50 ・ ・ ・ SSB modulator 52 ・ ・・ ・ Optical phased array antenna for transmission 62 ・ ・ ・ First optical phased array antenna for reception 70 ・ ・ ・ Optical heterodyne orthogonal detection laser radar (laser radar)
72 ... Second optical phased array antenna for reception 80 ... Optical transmitter Q ... Object to be measured

Claims (7)

A first branch that propagates the light output from the laser light source in only one direction and a first branch that branches into the second waveguide.
A second branch portion that branches the light propagating through the first waveguide into the third waveguide and the fourth waveguide, and
A modulation unit that supplies the same amount of heat to the first waveguide and the fourth waveguide to modulate light propagating through the first waveguide and the fourth waveguide .
A photodetector that detects the amount of interference light between the light propagating through the fourth waveguide and the light propagating through the second waveguide, which is modulated by the modulation unit.
A control unit that controls the amount of heat supplied from the modulation unit to the first waveguide and the fourth waveguide so that the amount of light of the interference light detected by the photodetector is reduced.
Equipped with a,
An optical 90-degree phase device that outputs light having a phase difference of 90 degrees from each other from the waveguide branched from the second waveguide and the third waveguide. The shape of the first heating region and the shape of the second heating region in the modulation unit that supplies heat to the first waveguide and the fourth waveguide by supplying a voltage or current are the same. And the shape of the first waveguide passing through the first heating region and the shape of the fourth waveguide passing through the second heating region are the same.
The control unit controls the modulation unit so that the amount of the interference light detected by the photodetector unit is reduced and the voltage or current supplied to each of the heating regions is the same. Item 1. The optical 90-degree phase device according to Item 1. The first heating region and the second heating region of the modulation unit are connected in series, and the first heating region and the second heating region are connected in series.
The optical 90-degree phase device according to claim 2, wherein the control unit controls the modulation unit so as to supply a voltage or a current to the first heating region and the second heating region connected in series. The optical 90-degree phase device according to claim 2 or 3, wherein the first heating region and the second heating region of the modulation unit are composed of a heater. A first branch that propagates the light output from the laser light source in only one direction and a first branch that branches into the second waveguide.
A second branch portion that branches the light propagating through the first waveguide into the third waveguide and the fourth waveguide, and
A current is supplied to the ridge portion having the PN junction, PP junction, or NN junction formed in the first waveguide and the fourth waveguide to supply the current to the first waveguide and the fourth waveguide. A modulator that modulates the light propagating in
A photodetector that detects the amount of interference light between the light propagating through the fourth waveguide and the light propagating through the second waveguide, which is modulated by the modulation unit.
The current supplied from the modulation unit to the first waveguide and each ridge formed in the fourth waveguide is controlled so that the amount of the interference light detected by the photodetector is reduced. Control unit and
With
Light having a phase difference of 90 degrees from each other is output from the waveguide branched from the second waveguide and the third waveguide.
Optical 90 degree phaser. The optical 90-degree phase device according to any one of claims 1 to 5.
A first equilibrium modulator that modulates the light propagating through the second waveguide of the optical 90 degree phaser, and
A second equilibrium modulator that modulates the light propagating through the third waveguide of the optical 90 degree phaser, and
A signal source for inputting a carrier signal to each of the first balanced modulator and the second balanced modulator,
A phaser that shifts the phase of the carrier signal input to the second balanced modulator by 90 degrees with respect to the phase of the carrier signal input to the first balanced modulator.
SSB modulator equipped with. An optical phased array antenna for radiation that adjusts the radiation angle of light by supplying heat to each of multiple waveguides and emits light to the object to be measured.
A first type of light emitted from the radiation optical phased array antenna that receives light reflected by the measurement object by adjusting the light reception angle by supplying heat to each of the plurality of waveguides. An optical phased array antenna for light reception, a second optical phased array antenna for light reception, and
The optical 90-degree phase device according to any one of claims 1 to 5.
A first photodetector that detects the amount of interference light between the light propagating in the second waveguide of the 90-degree optical phase device and the light received by the first light receiving optical phased array antenna.
A second photodetector that detects the amount of interference light between the light propagating in the third waveguide of the 90-degree optical phase device and the light received by the second light receiving optical phased array antenna.
An arithmetic unit that performs a complex Fourier transform on each of the detection results of the first photodetector and the second photodetector and calculates the Doppler frequency for the measurement object.
Optical heterodyne orthogonal detection laser radar equipped with.

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