Light beam transmitter

Abstract

To enable increasing the intensity of an optical beam without the need for a beam reference plate. [Solution] The optical beam transmitting device 2 includes an optical distribution unit 11 that distributes the laser light output from the laser light source 1 to N (where N is an integer of 2 or more) + 1 transmission lines, a frequency shift unit 12 that shifts the frequency of the laser light that has passed through the N transmission lines, and a beam conversion unit 14 that converts the N laser beams into transmission beams parallel to each other and converts the laser light that has passed through the remaining 1 transmission line into a local beam parallel to the transmission beams, as well as an optical demultiplexing unit 15 that radiates a portion of the N transmission beams into space, reflects the remaining N transmission beams as a phase detection beam, and also reflects the local beam, and a control unit 16 that detects the frequency difference between the frequency of the phase detection beam after reflection by the optical demultiplexing unit and the frequency of the local beam after reflection by the optical demultiplexing unit, and controls the amount of frequency shift based on the frequency difference.

Description

Technical Field

[0001] The present disclosure relates to an optical beam transmission device.

Background Art

[0002] There is an optical beam transmission device that performs coherent beam combining (CBC) of a plurality of optical beams. CBC aligns the phases of a plurality of optical beams and then combines the plurality of optical beams in space. By performing CBC, the peak intensity of the optical beam is increased. As such an optical beam transmission device, for example, Patent Document 1 discloses an optical beam transmission device including a plurality of collimating lenses for array light, a collimating lens for reference light, a beam reference flat plate that combines the collimated beam array light and the reference light, and a condensing lens in order to align the phases between a plurality of optical beams arranged in an array. One surface of the beam reference flat plate is at an angle of 45 degrees with respect to the array light output from the plurality of collimating lenses for array light, and the other surface of the beam reference flat plate is at an angle of 45 degrees with respect to the reference light output from the collimating lens for reference light so that the plurality of array lights and the reference light are given to the condensing lens. The beam reference flat plate is installed.

Prior Art Documents

Patent Documents

[0003] <000e0106>

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the optical beam transmitting device disclosed in Patent Document 1, the beam reference plate must be positioned such that one surface of the beam reference plate is at a 45-degree angle to the array light, and the other surface of the beam reference plate is at a 45-degree angle to the reference light. Therefore, unless the installation position of the collimating lens for the array light, the collimating lens for the reference light, the installation position of the beam reference plate, and the installation angle of the beam reference plate are precisely adjusted, the phase error of each beam cannot be detected, resulting in the problem that coherent beam synthesis cannot be performed.

[0005] This disclosure was made to solve the above-mentioned problems and aims to provide an optical beam transmitting device that can increase the intensity of an optical beam without providing a beam reference plate in which one surface is positioned at a 45-degree angle to the array light and the other surface is positioned at a 45-degree angle to the reference light. [Means for solving the problem]

[0006] The optical beam transmitting device according to this disclosure includes an optical distribution unit that distributes laser light output from a laser light source to (N (where N is an integer of 2 or more) + 1) transmission paths, a frequency shifting unit that shifts the frequencies of the laser light that has passed through N of the (N+1) transmission paths, and a beam conversion unit that converts the N laser beams after frequency shifting by the frequency shifting unit into parallel transmission beams, and converts the laser light that has passed through the remaining 1 transmission path into a local beam parallel to the transmission beam. The optical beam transmitting device also includes an optical demultiplexing unit that radiates a portion of each of the N transmission beams into space, reflects the remainder of each of the N transmission beams as a phase detection beam, and reflects a local beam, and a control unit that detects the frequency difference between the frequency of each phase detection beam after reflection by the optical demultiplexing unit and the frequency of the local beam after reflection by the optical demultiplexing unit, and controls the respective frequency shift amount based on the respective frequency difference. [Effects of the Invention]

[0007] According to this disclosure, the intensity of the optical beam can be increased without providing a beam reference plate that is positioned such that one surface is at a 45-degree angle to the array light and the other surface is at a 45-degree angle to the reference light. [Brief explanation of the drawing]

[0008] [Figure 1] This is a configuration diagram showing the optical beam transmitting device 2 according to Embodiment 1. [Figure 2] This diagram shows the internal configuration of the frequency shifter 12-n (n=1,···,N) and the phase synchronization unit 19. [Figure 3] This is a configuration diagram showing the optical beam transmitting device 2 according to Embodiment 2. [Figure 4] This is an explanatory diagram showing the polarization direction after rotation by the polarization rotation unit 41. [Figure 5] Figure 5A is an explanatory diagram showing the transmission beam passing through the polarization beam splitter 42, and Figure 5B is an explanatory diagram showing the phase detection beam, which is the transmission beam after reflection by the polarization beam splitter 42, and the local beam after reflection by the polarization beam splitter 42. [Figure 6] This is a diagram showing the internal configuration of the frequency shifter 12-n (n=1,···,N) of the frequency shifting unit 12. [Figure 7] This is a diagram showing the internal configuration of the frequency shifter 12-n (n=1,···,N) of the frequency shifting unit 12. [Figure 8] This is a diagram showing the internal configuration of the frequency shifter 12-n (n=1,···,N) of the frequency shifting unit 12. [Figure 9] This is a diagram showing the internal configuration of the frequency shifter 12-n (n=1,···,N) of the frequency shifting unit 12. [Modes for carrying out the invention]

[0009] To provide a more detailed explanation of this disclosure, the forms for implementing this disclosure will be described below with reference to the attached drawings.

[0010] Embodiment 1. Figure 1 is a configuration diagram showing the optical beam transmitting device 2 according to Embodiment 1. In Figure 1, solid arrows indicate the flow of optical signals, and dashed arrows indicate the flow of electrical signals. The laser light source 1 emits a laser beam and outputs the laser beam to the light beam transmitter 2. In Figure 1, the laser light source 1 is located outside the optical beam transmitter 2. However, this is just one example, and the laser light source 1 may also be located inside the optical beam transmitter 2. The optical beam transmitter 2 distributes the laser light output from the laser light source 1 into multiple laser beams and radiates these multiple laser beams into space. The multiple laser beams radiated into space are then subjected to CBC (Continuous Convergence Blocking).

[0011] The optical beam transmitting device 2 includes an optical distribution unit 11, a frequency shift unit 12, an optical amplification unit 13, a beam conversion unit 14, an optical demultiplexing unit 15, and a control unit 16. The optical beam transmitter 2 is equipped with (N+1) transmission paths L-1 to L-(N+1), and frequency shifting units 12 and optical amplification units 13 are provided on N transmission paths L-1 to LN among the (N+1) transmission paths L-1 to L-(N+1). Furthermore, beam conversion units 14 are provided on (N+1) transmission lines L-1 to L-(N+1). N is an integer of 2 or more.

[0012] The input terminal of the optical distribution unit 11 is connected to the laser light source 1. Of the (N+1) output terminals of the optical distribution unit 11, each of the N output terminals is connected to the frequency shift unit 12 via a transmission line Ln (n=1,···,N). Of the (N+1) output terminals of the optical distribution unit 11, the remaining one output terminal is connected to the beam conversion unit 14 via the transmission line L-(N+1). The optical distribution unit 11 distributes the laser light output from the laser light source 1 to (N+1) transmission paths L-1 to L-(N+1).

[0013] The frequency shifting unit 12 is equipped with N frequency shifters 12-1 to 12-N. The frequency shift unit 12 acquires laser light from the optical distribution unit 11 via N transmission lines L-1 to LN. The frequency shifting unit 12 shifts the frequency of the laser light that has passed through N transmission lines L-1 to LN out of (N+1) transmission lines by the frequency of the high-frequency signal output from the phase-locking unit 19 (described later). Furthermore, N laser beams with different frequencies superimposed in the frequency shifters 12-1 to 12-N are output to the optical amplification unit 13. The frequency shifter 12-n (n=1,···,N) shifts the frequency f of the laser light that has passed through the transmission line Ln by a frequency shift amount FS. n f+FS shifted by only that much n The laser light and the f+FS superimposed with different high frequencies n +FD n The laser light is output to the optical amplifier 13-n. Unless otherwise specified, the frequency is f+FS. n The laser light and f+FS n +FD n The laser light and the frequency-shifted laser light are collectively referred to as the laser light after frequency shifting.

[0014] The optical amplification unit 13 is equipped with N optical amplifiers 13-1 to 13-N. The optical amplification unit 13 amplifies the N laser beams after frequency shifting by the frequency shifting unit 12. The optical amplification unit 13 outputs the N amplified laser beams to the beam conversion unit 14. The optical amplifier 13-n (n=1,···,N) amplifies the laser light after frequency shifting by the frequency shifter 12-n. The optical amplifier 13-n outputs the amplified laser light to the optical collimator 14-n, which will be described later.

[0015] The beam conversion unit 14 is equipped with (N+1) optical collimators 14-1 to 14-(N+1). The beam conversion unit 14 converts the N laser beams amplified by the optical amplification unit 13 into parallel transmission beams. The beam conversion unit 14 converts the laser beam that has passed through the remaining one transmission path L-(N+1) out of the (N+1) transmission paths L-1 to L-(N+1) into a local beam parallel to the transmission beam. The beam conversion unit 14 outputs N transmission beams and one local beam to the optical demultiplexing unit 15. The optical collimator 14-n (n = 1, ···, N) converts the laser beam amplified by the optical amplifier 13-n into a transmission beam. The optical collimator 14-n outputs the transmission beam to the optical demultiplexing unit 15. The optical collimator 14-(N+1) converts the laser beam that has passed through the transmission path L-(N+1) into a local beam parallel to the transmission beam. The optical collimator 14-(N+1) outputs the local beam to the optical demultiplexing unit 15.

[0016] The optical demultiplexing unit 15 radiates a part of each of the N transmission beams output from the beam conversion unit 14 into space, and reflects the remaining part of each of the N transmission beams as a phase detection beam. The N transmission beams radiated into space undergo CBC in space to become a transmission combined beam. The optical demultiplexing unit 15 reflects the local beam output from the beam conversion unit 14. The N phase detection beams after reflection by the optical demultiplexing unit 15 and the local beam after reflection by the optical demultiplexing unit 15 are output to the control unit 16.

[0017] The control unit 16 includes a beam condensing unit 17, a photoelectric conversion unit 18, and a phase synchronization unit 19. The control unit 16 detects the frequency · phase difference Δf n +FD n between the frequency (f + FS n = FS n +FD n ) of each phase detection beam after reflection by the optical demultiplexing unit 15 and the frequency (f) of the local beam after reflection by the optical demultiplexing unit 15 (n = 1, ···, N). The control unit 16, based on the frequency · phase difference Δf n , determines the frequency shift amount FS in the frequency shifter 12-nn Control.

[0018] The beam focusing unit 17 focuses the phase detection beams and the local beams, which are reflected by the optical demultiplexing unit 15, onto the photoelectric conversion unit 18. The photoelectric conversion unit 18 measures the frequency-phase difference Δf between the frequency of each phase detection beam and the frequency of the local beam. n =FS n +FD n Electrical signal ES representing (n=1,···,N) n The frequency-phase difference Δf is output to the phase-locking unit 19. n Electrical signal ES indicating n For example, electrical signals ES n The frequency is the frequency-phase difference Δf n It is a signal. The phase-locking unit 19 controls the electrical signal ES n The frequency-phase difference Δf shown by (n=1,···,N) n Based on this, the frequency shift amount FS in the frequency shifter 12-n n Control.

[0019] Figure 2 is a diagram showing the internal configuration of the frequency shifter 12-n (n=1,···,N) and the phase synchronization unit 19. Figure 2 shows one of the systems related to the N transmission lines L-1 to LN. The phase-locking unit 19 includes a frequency discrimination unit 21, a reference oscillator 22, a comparison unit 23, a loop filter 24, and a voltage-controlled oscillator (VCO) 25. The frequency discrimination unit 21 is implemented, for example, by a bandpass filter. The frequency discrimination unit 21 receives N electrical signals ES1 to ES from the photoelectric conversion unit 18. N Given N electrical signals ES1~ES N It discriminates by frequency. The frequency discrimination unit 21 processes the frequency-discriminated electrical signal ES n The comparison unit 23 outputs (n=1,···,N).

[0020] The reference oscillator 22 has a reference signal Ref having a frequency related to the transmission line Ln (n=1,···,N). n The comparison unit 23 outputs N reference signals Ref1 to Ref N The frequencies are different from each other. The comparison unit 23 receives the electrical signal ES output from the frequency discrimination unit 21. n The phase frequencies of (n=1,···,N) and the reference signal Ref output from the reference oscillator 22 n Compare this with the phase frequency. The comparison unit 23 outputs an error signal E that indicates the phase frequency error between the two. n This is output to loop filter 24.

[0021] The loop filter 24 is implemented, for example, by a low-pass filter. The loop filter 24 processes the error signal E output from the comparison unit 23. n By suppressing superimposed high-frequency noise and other interferences, the oscillation of the loop is suppressed. The loop filter 24 suppresses the error signal E after high-frequency noise and other factors. n This is output to the voltage-controlled oscillator 25. The voltage-controlled oscillator 25 receives the error signal E output from the loop filter 24. n Based on this, the optical frequency converter 31, which will be described later, is controlled.

[0022] The frequency shifter 12-n (n=1,···,N) comprises an optical frequency converter 31, a high-frequency signal generator 32, and an optical phase modulator 33. The optical frequency converter 31 is implemented, for example, by an acousto-optical modulator (AOM) or a modulator using lithium niobate (LiNbO3). The optical frequency converter 31 converts the frequency f of the laser light that has passed through the transmission line Ln to the error signal E output from the voltage-controlled oscillator 25. n The corresponding frequency shift amount FS n Shift only that. The laser light output from the optical frequency converter 31 is supplied to the optical phase modulator 33.

[0023] The high-frequency signal generator 32 generates a high-frequency signal and outputs the high-frequency signal to the optical phase modulator 33. The optical phase modulator 33 superimposes the frequency modulation component of the high-frequency signal output from the high-frequency signal generator 32 as a dither signal onto the laser light output from the optical frequency converter 31. The reason for superimposing the dither signal onto the laser light is that the control unit 16 generates N electrical signals ES1 to ES N This is to allow for the identification of which transmission path each of these relates to the transmitted beam.

[0024] Next, we will explain the operation of the optical beam transmitter 2 shown in Figure 1. The laser light source 1 emits a laser beam and outputs the laser beam to the light beam transmitter 2. The optical distribution unit 11 of the optical beam transmitter 2 distributes the laser light output from the laser light source 1 to (N+1) transmission paths L-1 to L-(N+1). As a result, the laser light that passes through transmission line L-1 is supplied to frequency shifter 12-1, the laser light that passes through transmission line L-2 is supplied to frequency shifter 12-2, and the laser light that passes through transmission line LN is supplied to frequency shifter 12-N. The laser light that has passed through the transmission path L-(N+1) is supplied to the optical collimator 14-(N+1).

[0025] The frequency shift unit 12 acquires laser light from the optical distribution unit 11 via N transmission lines L-1 to LN. The frequency shifting unit 12 first shifts the frequency of the laser light that has passed through the N transmission lines L-1 to LN. Specifically, the optical frequency converter 31 of the frequency shifter 12-n (n=1,···,N) converts the frequency f of the laser light that has passed through the transmission line Ln to the error signal E output from the voltage-controlled oscillator 25, which will be described later. n The corresponding frequency shift amount FS n Shift only that. The optical frequency converter 31 shifts the frequency f of the laser light by a frequency shift amount FS.n By shifting the phase error, for example, even if the phase of the laser light passing through the transmission line Ln fluctuates due to environmental changes such as temperature, it becomes possible to amplify the peak intensity of the composite beam by CBC. The optical frequency converter 31 outputs the phase-modulated laser light to the optical phase modulator 33.

[0026] The high-frequency signal generator 32 of the frequency shifter 12-n (n=1,···,N) generates a high-frequency signal and outputs the high-frequency signal to the optical phase modulator 33. The optical phase modulator 33 of the frequency shifter 12-n superimposes the frequency modulation component of the high-frequency signal output from the high-frequency signal generator 32 as a dither signal onto the laser light output from the optical frequency converter 31. The optical phase modulator 33 outputs the laser light, after the dither signal has been superimposed, to the optical amplifier 13-n.

[0027] The optical amplifier 13-n (n=1,···,N) of the optical amplification unit 13 amplifies the laser light after the dither signal is superimposed when it is supplied from the frequency shifter 12-n. The optical amplifier 13-n outputs the amplified laser light to the optical collimator 14-n. The local beam, described later, does not need to be transmitted over long distances like the N transmission beams described later, so there is little need to amplify the laser light that has passed through the transmission path L-(N+1) using an optical amplifier. For this reason, the optical beam transmitter 2 shown in Figure 1 does not have an optical amplifier for amplifying the laser light that has passed through the transmission path L-(N+1). However, this is just one example, and the optical beam transmitter 2 may also be equipped with an optical amplifier for amplifying the laser light that has passed through the transmission path L-(N+1).

[0028] The beam conversion unit 14 converts the N laser beams amplified by the optical amplification unit 13 into parallel transmission beams. In other words, the optical collimator 14-n (n=1,···,N) converts the laser light amplified by the optical amplifier 13-n into a transmission beam. The optical collimator 14-n outputs the transmission beam to the optical demultiplexer 15. Furthermore, the beam conversion unit 14 converts the laser light that has passed through the transmission path L-(N+1) into a local beam parallel to the transmitted beam. In other words, the optical collimator 14-(N+1) converts the laser light that has passed through the transmission path L-(N+1) into a local beam parallel to the transmitted beam. The optical collimator 14-(N+1) outputs the local beam to the optical demultiplexer 15. The beam diameter of the local beam may be narrower than the beam diameter of the transmitting beam. Therefore, the size of the optical collimator 14-(N+1) can be smaller than the size of the optical collimator 14-n (n=1,···,N). This increases the flexibility in the installation location of the optical collimator 14-(N+1).

[0029] When the optical demultiplexer 15 receives N transmission beams from the beam conversion unit 14, it radiates a portion of each of the N transmission beams into space. The N transmission beams radiated into space are then combined by CBC in space to form a combined transmission beam. The optical demultiplexer 15 uses the remaining phases of each of the N transmission beams as phase detection beams BP1~BP N The beam is then reflected towards the beam focusing unit 17. The optical demultiplexer 15 reflects the local beam from the beam conversion unit 14 towards the beam focusing unit 17.

[0030] The beam focusing unit 17 of the control unit 16 receives the phase detection beam BP from the optical demultiplexing unit 15. n Given (n=1,···,N) and a local beam, a phase detection beam BP is used. n The local beam and the photoelectric conversion unit 18 are focused into the photoelectric conversion unit. The photoelectric conversion unit 18 of the control unit 16 generates a phase detection beam BP n The frequency-phase difference Δf between the frequency of the beam and the frequency of the local beam. n Electrical signal ES indicating n The frequency-phase difference Δf is output to the phase-locking unit 19. n Electrical signal ES indicating n For example, electrical signals ESn The frequency is the frequency-phase difference Δf n It is a signal.

[0031] The phase-locking unit 19 controls the electrical signal ES n The frequency-phase difference Δf shown by (n=1,···,N) n Based on this, the frequency shift amount FS in the frequency shifter 12-n n Control. Specifically, the frequency discrimination unit 21 of the phase-locking unit 19 receives N electrical signals ES1~ES from the photoelectric conversion unit 18. N Given N electrical signals ES1~ES N It discriminates by frequency. Electrical signals ES1~ES N Frequency discrimination is performed based on the frequency of the dither signal superimposed by the optical phase modulator 33. The frequency discrimination unit 21 processes the frequency-discriminated electrical signal ES n The comparison unit 23 outputs (n=1,···,N).

[0032] The reference oscillator 22 of the phase-locking unit 19 has a reference signal Ref having a frequency related to the transmission line Ln (n=1,···,N). n The comparison unit 23 outputs N reference signals Ref1 to Ref N The frequencies are different from each other. The comparison unit 23 of the phase-locking unit 19 receives an electrical signal ES from the frequency discrimination unit 21. n When (n=1,···,N) is received, an electrical signal ES is received. n The phase frequency and reference signal Ref n The phase frequency of the electrical signal ES is compared with that of the other element. n The phase frequency and reference signal Ref n It outputs an error signal with respect to the phase frequency. The comparison unit 23 receives an error signal E indicating the phase frequency error. n This is output to loop filter 24.

[0033] The loop filter 24 of the phase-locking unit 19 receives the error signal E output from the comparison unit 23. nIt suppresses superimposed high-frequency noise and other unwanted sounds. The loop filter 24 suppresses the error signal E after high-frequency noise and other factors. n This is output to the voltage-controlled oscillator 25. The voltage-controlled oscillator 25 of the phase-locked unit 19 receives the error signal E from the loop filter 24. n When it receives the error signal E n The optical frequency converter 31 is controlled based on this.

[0034] In the above embodiment 1, the optical beam transmitting device 2 is configured to include an optical distribution unit 11 that distributes the laser light output from the laser light source 1 to (N (where N is an integer of 2 or more) + 1) transmission paths, a frequency shifting unit 12 that shifts the frequencies of the laser light that has passed through N of the (N+1) transmission paths and superimposes dither signals of different frequencies on them, and a beam conversion unit 14 that converts the N laser beams after frequency shifting by the frequency shifting unit 12 into parallel transmission beams and converts the laser light that has passed through the remaining 1 of the (N+1) transmission paths into a local beam parallel to the transmission beams. Furthermore, the optical beam transmitter 2 includes an optical demultiplexer 15 that radiates a portion of each of the N transmitting beams into space, reflects the remainder of each of the N transmitting beams as a phase detection beam, and also reflects the local beam, and a control unit 16 that detects the frequency difference between the frequency of each phase detection beam after reflection by the optical demultiplexer 15 and the frequency of the local beam after reflection by the optical demultiplexer 15, and controls the respective frequency shift amount based on the respective frequency difference. Therefore, the optical beam transmitter 2 can increase the intensity of the optical beam without providing a beam reference plate that is positioned so that one side is at a 45-degree angle to the array light and the other side is at a 45-degree angle to the reference light.

[0035] Furthermore, in Embodiment 1, the optical beam transmitter 2 is configured such that the control unit 16 detects the phase difference between the phase of each phase detection beam after reflection by the optical demultiplexer 15 and the phase of the local beam after reflection by the optical demultiplexer 15, and controls the phase of the laser light that has passed through each of the N transmission lines based on these phase differences. Therefore, even if the phase of the laser light that has passed through the transmission line Ln fluctuates due to environmental changes such as temperature, the optical beam transmitter 2 can still amplify the beam intensity using CBC.

[0036] In Embodiment 1, N transmitting beams and one local beam are emitted parallel to each other from the same plane. This makes it possible to make the optical beam transmitting device 2 smaller and lighter, and eliminates the need to adjust the optical axes of the mutually orthogonal beams, thereby simplifying the assembly and adjustment of the device.

[0037] Embodiment 2. Embodiment 2 describes an optical beam transmitting device 2 that includes a polarization rotation unit 41 and a polarization beam splitter 42.

[0038] Figure 3 is a configuration diagram showing the optical beam transmitting device 2 according to Embodiment 2. In Figure 3, the same reference numerals as in Figure 1 indicate the same or corresponding parts, so a detailed explanation is omitted. The polarization rotation unit 41 is equipped with (N+1) polarization rotators 41-1 to 41-(N+1). The polarization rotation unit 41 rotates the polarization direction of each of the N laser beams amplified by the optical amplification unit 13, and outputs the laser beams with rotated polarization directions to the beam conversion unit 14. The polarization rotation unit 41 rotates the polarization direction of the laser light that has passed through the transmission path L-(N+1), and outputs the laser light with the rotated polarization direction to the beam conversion unit 14.

[0039] The polarization rotator 41-n (n=1,···,N) rotates the polarization direction of the laser light amplified by the optical amplifier 13-n, and outputs the laser light with the rotated polarization direction to the optical collimator 14-n. The polarization rotator 41-(N+1) rotates the polarization direction of the laser light that has passed through the transmission path L-(N+1), and outputs the laser light with the rotated polarization direction to the optical collimator 14-(N+1).

[0040] The polarizing beam splitter 42 realizes the optical demultiplexing section 15 shown in Figure 1. The polarization beam splitter 42 performs radiation and reflection of each transmitted beam according to the polarization direction of each transmitted beam output from the beam conversion unit 14. Furthermore, the polarizing beam splitter 42 reflects the local beam output from the beam conversion unit 14.

[0041] Next, the operation of the optical beam transmitter 2 shown in Figure 3 will be described. However, it is the same as the optical beam transmitter 2 shown in Figure 1, except for the polarization rotation unit 41 and the polarization beam splitter 42. Therefore, the operation of the polarization rotation unit 41 and the polarization beam splitter 42 will be mainly described here.

[0042] Figure 4 is an explanatory diagram showing the polarization direction after rotation by the polarization rotation unit 41. Figure 4 shows the polarization direction of the laser light converted into a transmission beam by the optical collimator 14-n (n=1,···,N) and the polarization direction of the laser light converted into a local beam by the optical collimator 14-(N+1). When the polarization rotator 41-n (n=1,···,N) receives amplified laser light from the optical amplifier 13-n, it rotates the polarization direction of the laser light so that, as shown in Figure 4, the polarization direction of the laser light is tilted slightly vertically rather than horizontally in the figure. In other words, the polarization rotator 41-n rotates the polarization direction of the laser light so that the polarization direction of the laser light after rotation has both a horizontal component and a vertical component in the figure. The polarization rotator 41-n outputs the laser light, after rotation in the polarization direction, to the optical collimator 14-n.

[0043] When the polarization direction of the laser light that has passed through the transmission path L-(N+1) is given, the polarization rotator 41-(N+1) rotates the polarization direction of the laser light so that the polarization direction of the laser light becomes perpendicular in the figure, as shown in Figure 4. The polarization rotator 41-(N+1) outputs the laser light, after rotation in the polarization direction, to the optical collimator 14-(N+1).

[0044] The optical collimator 14-n (n=1,···,N) converts the laser light, after polarization direction rotation by the polarization rotator 41-n, into a transmission beam. The optical collimator 14-n outputs the transmission beam to the polarization beam splitter 42. The optical collimator 14-(N+1) converts the laser light, after polarization direction rotation by the polarization rotator 41-(N+1), into a local beam parallel to the transmitted beam. The optical collimator 14-(N+1) outputs the local beam to the polarized beam splitter 42.

[0045] The polarization beam splitter 42 radiates and reflects each transmitted beam into space according to the polarization direction of each transmitted beam output from the beam conversion unit 14. Specifically, as shown in Figure 5A, the polarizing beam splitter 42 transmits the horizontal component of the transmission beam and radiates the horizontal component into space as the transmission beam. Figure 5A is an explanatory diagram showing the transmitted beam passing through the polarizing beam splitter 42.

[0046] As shown in Figure 5B, the polarization beam splitter 42 uses the vertical component in the transmission beam to detect the phase detection beam BP1~BP N The beam is then reflected towards the beam focusing unit 17. Furthermore, as shown in Figure 5B, the polarizing beam splitter 42 reflects the vertical component of the local beam towards the beam focusing unit 17. Figure 5B is an explanatory diagram showing the phase detection beam, which is the transmission beam after reflection by the polarization beam splitter 42, and the local beam after reflection by the polarization beam splitter 42.

[0047] In the above embodiment 2, the optical beam transmitting device 2 shown in Figure 3 is configured to include a polarization rotation unit 41 that rotates the polarization direction of each of the N laser beams after frequency shifting by the frequency shift unit 12, and also rotates the polarization direction of the laser beam that has passed through the transmission path L-(N+1), and outputs the laser beam after polarization direction rotation to the beam conversion unit 14. Therefore, the optical beam transmitting device 2 shown in Figure 3, like the optical beam transmitting device 2 shown in Figure 1, can increase the intensity of the optical beam without providing a beam reference plate in which one surface is positioned at a 45-degree angle to the array light and the other surface is positioned at a 45-degree angle to the reference light, and can also easily adjust the ratio of the transmitted beam radiated into space to the transmitted beam reflected.

[0048] In the optical beam transmitter 2 shown in Figure 3, the polarization rotation unit 41 rotates the polarization direction of the laser light before emitting N transmission beams into space. However, this is just one example; the polarization direction of each transmission beam and local beam may be rotated after the N transmission beams and one local beam have been emitted into space. One means of rotating the polarization direction in this way is, for example, a half-wave plate. When a half-wave plate is rotated, the polarization direction of each beam can be rotated according to the rotation angle of the half-wave plate.

[0049] In the optical beam transmitter 2 shown in Figure 3, the polarization rotation unit 41 is equipped with (N+1) polarization rotators 41-1 to 41-(N+1), and the polarization rotators 41-n (n=1, ..., N+1) rotate the polarization direction of the laser light. However, this is just one example, and the polarization rotation unit 41 may also rotate the polarization direction of the laser light by rotating the optical fibers that realize each of the (N+1) transmission lines L-1 to L-(N+1). Furthermore, if the transmission line Ln and the optical collimator 14-n are an integrated structure, the polarization direction of the laser light may be rotated by rotating the transmission line Ln and the optical collimator 14-n together.

[0050] Embodiment 3. Embodiment 3 describes an optical beam transmitting device 2 in which the frequency shifting unit 12 comprises N optical frequency converters 51, N optical splitters 52, N 90-degree rotators 53, N phase modulators 54, and N photosynthesizers 55.

[0051] Figure 6 is a diagram showing the internal configuration of the frequency shifter 12-n (n=1,···,N) of the frequency shifting unit 12. In the example shown in Figure 6, the optical demultiplexing unit 15 is realized by a polarization beam splitter 42. The frequency shifter 12-n (n=1,···,N) comprises an optical frequency converter 51, an optical splitter 52, a 90-degree rotator 53, a phase modulator 54, and a photosynthesizer 55.

[0052] The optical frequency converter 51 is implemented, for example, by a modulator using an AOM or lithium niobate. The optical frequency converter 51 converts the frequency f of the laser light that has passed through the transmission line Ln to the error signal E output from the voltage-controlled oscillator 25. n The corresponding frequency shift amount FS n This shifts the phase frequency by only that much. The optical frequency converter 51 outputs the frequency-shifted laser light to the optical splitter 52.

[0053] The optical splitter 52 splits the laser light, which has been frequency-shifted by the optical frequency converter 51, into two. The optical splitter 52 outputs one of the laser beams after splitting to the 90-degree rotator 53, and outputs the other laser beam after splitting to the photosynthesizer 55. The 90-degree rotator 53 rotates the polarization direction of one of the laser beams after it has been split into two by the optical splitter 52 by 90 degrees. The 90-degree rotator 53 outputs the laser beam, after being rotated 90 degrees, to the phase modulator 54.

[0054] The phase modulator 54 modulates the laser beam, which has been rotated 90 degrees by the 90-degree rotator 53, with a high-frequency signal output from the high-frequency generator 32 (see Figure 2, omitted from Figure 6 onwards), and superimposes the modulated component as dither. The phase modulator 54 outputs the phase-modulated laser light to the photosynthesizer 55. The photosynthesizer 55 combines the other laser beam after it has been split into two by the optical splitter 52 with the laser beam after it has been phase-modulated by the phase modulator 54. The photosynthesizer 55 outputs the resulting laser light to the optical amplifier 13-n.

[0055] Next, the operation of the frequency shifter 12-n (n=1,···,N), the optical amplifier 13-n, the optical collimator 14-n, and the polarization beam splitter 42 will be described. In the example shown in Figure 6, the polarization direction of the laser light that has passed through the transmission line Ln is horizontal in the figure, and laser light with a horizontal polarization direction is supplied to the optical frequency converter 51. The optical frequency converter 51 converts the frequency f of the laser light that has passed through the transmission line Ln to the error signal E output from the voltage-controlled oscillator 25. n The corresponding frequency shift amount FS n Shift only that. The optical frequency converter 51 outputs the frequency-shifted laser light to the optical splitter 52.

[0056] When the optical splitter 52 receives the frequency-shifted laser light from the optical frequency converter 51, it splits the laser light into two. The optical splitter 52 outputs one of the split laser beams to the 90-degree rotator 53 and the other split laser beam to the photosynthesizer 55. The polarization direction of the other split laser beam is horizontal, as shown in Figure 6. When the polarization direction of the laser beam is horizontal, this laser beam corresponds to the transmitted light.

[0057] When the 90-degree rotator 53 receives one of the laser beams after the optical splitter 52 has split into two, it rotates the polarization direction of the laser beam by 90 degrees. The 90-degree rotator 53 outputs the laser beam, after being rotated 90 degrees, to the phase modulator 54. In the example shown in Figure 6, the polarization direction of the laser light supplied to the optical frequency converter 51 is horizontal in the figure. Therefore, the 90-degree rotator 53 rotates the polarization direction of the laser light by 90 degrees, causing the polarization direction of the laser light to change to the vertical in the figure. When the polarization direction of the laser light is vertical, the laser light corresponds to the dither component.

[0058] When the phase modulator 54 receives the laser beam rotated by 90 degrees from the 90-degree rotator 53, it modulates it with the high-frequency signal output from the high-frequency generator 32 (see Figure 2, omitted from Figure 6 onwards), and outputs the laser beam rotated by 90 degrees, with the modulation component superimposed as dither, to the photosynthesizer 55. The photosynthesizer 55 combines the other laser beam after it has been split into two by the optical splitter 52 with the laser beam after it has been phase-modulated by the phase modulator 54. The photosynthesizer 55 outputs the resulting laser light to the optical amplifier 13-n.

[0059] The optical amplifier 13-n (n=1,···,N) amplifies the synthesized laser light when it is supplied from the photosynthesizer 55. The optical amplifier 13-n outputs the amplified laser light to the optical collimator 14-n. The optical collimator 14-n (n=1,···,N) converts the laser light amplified by the optical amplifier 13-n into a transmission beam. The optical collimator 14-n outputs the transmission beam to the polarization beam splitter 42. The optical collimator 14-(N+1) converts the laser light that has passed through the transmission path L-(N+1) into a local beam parallel to the transmitted beam. The optical collimator 14-(N+1) outputs the local beam to the polarized beam splitter 42.

[0060] As shown in Figure 6, the polarizing beam splitter 42 transmits the horizontal component of the transmission beam and radiates the horizontal component into space as the transmission beam. As shown in Figure 6, the polarization beam splitter 42 uses the vertical component in the transmission beam to detect the phase detection beam BP1~BPN The beam is then reflected towards the beam focusing unit 17. The vertical component is the dither component. The polarizing beam splitter 42 also reflects the local beam towards the beam focusing unit 17.

[0061] In the above embodiment 3, the optical beam transmitting device 2 is configured such that the frequency shift unit 12 comprises N optical frequency converters 51 that shift the frequency of each laser beam that has passed through N transmission paths out of (N+1) transmission paths by a frequency shift amount, N optical splitters 52 that split the laser beam after frequency shift by each optical frequency converter 51 into two, N 90-degree rotators 53 that rotate the polarization direction of one of the laser beams after splitting by each optical splitter 52 by 90 degrees, N phase modulators 54 that modulate the phase of the laser beam after rotation by each 90-degree rotator 53, and N photocombiners 55 that combine the other laser beam after splitting by each optical splitter 52 and the phase-modulated laser beam by each phase modulator 54, and output the combined laser beam to the beam conversion unit 14. Therefore, the optical beam transmitting device 2 does not radiate a transmission beam superimposed with a dither signal into space, but instead has phase detection beams BP1~BP having a dither component. N The dither signal can be reflected back towards the beam focusing unit 17. As a result, the transmitted beam, which does not have a dither signal superimposed on it, is CBC'd, thus suppressing the degradation of the transmitted combined beam quality. Additionally, phase detection beams BP1~BP, which do not have dither signals superimposed on them, are used. N Since this is supplied to the photoelectric conversion unit 18, the phase detection accuracy can be improved.

[0062] Embodiment 4. Embodiment 4 describes an optical beam transmitting device 2 in which the frequency shifting unit 12 comprises N optical frequency converters 61, N polarization rotators 62, N polarization demultiplexers 63, N phase modulators 64, and N photosynthesizers 65.

[0063] Figure 7 is a diagram showing the internal configuration of the frequency shifter 12-n (n=1,···,N) of the frequency shifting unit 12. In the example shown in Figure 7, the optical demultiplexing unit 15 is realized by a polarization beam splitter 42. The frequency shifter 12-n (n=1,···,N) comprises an optical frequency converter 61, a polarization rotator 62, a polarization demultiplexer 63, a phase modulator 64, and a photosynthesizer 65.

[0064] The optical frequency converter 61 is implemented, for example, by an AOM or a modulator using lithium niobate. The optical frequency converter 61 converts the frequency f of the laser light that has passed through the transmission line Ln to the error signal E output from the voltage-controlled oscillator 25. n The corresponding frequency shift amount FS n Shift only that. Next, the optical frequency converter 61 converts the phase of the laser light that has passed through the transmission path Ln to the error signal E n Only the phase error indicated by this will be modulated. The optical frequency converter 61 outputs the phase-modulated laser light to the polarization rotator 62.

[0065] The polarization rotator 62 rotates the polarization direction of the laser light after phase modulation by the optical frequency converter 61. The polarization demultiplexer 63 demultiplexes the laser light after polarization direction rotation by the polarization rotator 62 into two waves, according to the polarization component of the laser light after polarization direction rotation. The polarization demultiplexer 63 outputs one of the two resulting laser beams to the phase modulator 64 and outputs the other resulting laser beam to the photosynthesizer 65.

[0066] The phase modulator 64 modulates the phase of one of the laser beams after it has been split into two by the polarization demultiplexer 63. The phase modulator 64 outputs the phase-modulated laser light to the photosynthesizer 65. The photosynthesizer 65 combines the other laser beam, which has been split into two by the polarization demultiplexer 63, with the laser beam, which has been phase-modulated by the phase modulator 64. The photosynthesizer 65 outputs the resulting laser light to the optical amplifier 13-n.

[0067] Next, the operation of the frequency shifter 12-n (n=1,···,N), the optical amplifier 13-n, the optical collimator 14-n, and the polarization beam splitter 42 will be described. In the example shown in Figure 7, the polarization direction of the laser light that has passed through the transmission path Ln is horizontal in the figure, and laser light with a horizontal polarization direction is supplied to the optical frequency converter. The optical frequency converter 61 converts the frequency f of the laser light that has passed through the transmission line Ln to the error signal E output from the voltage-controlled oscillator 25. n The corresponding frequency shift amount FS n Shift only that. The optical frequency converter 61 outputs the frequency-shifted laser light to the polarization rotator 62.

[0068] When the frequency-shifted laser light is supplied to the optical frequency converter 61, the polarization rotator 62 rotates the polarization direction of the laser light so that, as shown in Figure 7, the polarization direction of the laser light is tilted slightly vertically rather than horizontally in the figure. In other words, the polarization rotator 62 rotates the polarization direction of the laser light so that the polarization direction of the laser light after rotation has both a horizontal component and a vertical component in the figure. The polarization rotator 62 outputs the laser light, after rotation in the polarization direction, to the polarization demultiplexer 63.

[0069] When the polarization demultiplexer 63 receives laser light from the polarization rotator 62 after rotation in the polarization direction, it demultiplexes the laser light into two waves according to the polarization component of the laser light. Specifically, the polarization demultiplexer 63 demultiplexes the laser light into a horizontal component and a vertical component. The polarization demultiplexer 63 outputs the vertical component, which is one of the laser beams after two demultiplexing, to the phase modulator 64, and outputs the horizontal component, which is the other laser beam after two demultiplexing, to the photosynthesizer 65.

[0070] When the phase modulator 64 receives a vertical component as one of the laser beams from the polarization demultiplexer 63, it modulates it with a high-frequency signal output from the high-frequency generator 32 (see Figure 2, omitted from Figure 6 onwards), and outputs the laser beam rotated by 90 degrees with the modulated component superimposed as dither to the photosynthesizer 65. The photosynthesizer 65 combines the other laser beam, which has been split into two by the polarization demultiplexer 63, with the laser beam, which has been phase-modulated by the phase modulator 64. The photosynthesizer 65 outputs the resulting laser light to the optical amplifier 13-n.

[0071] The optical amplifier 13-n (n=1,···,N) amplifies the synthesized laser light when it is supplied from the photosynthesizer 65. The optical amplifier 13-n outputs the amplified laser light to the optical collimator 14-n. The optical collimator 14-n (n=1,···,N) converts the laser light amplified by the optical amplifier 13-n into a transmission beam. The optical collimator 14-n outputs the transmission beam to the polarization beam splitter 42. The optical collimator 14-(N+1) converts the laser light that has passed through the transmission path L-(N+1) into a local beam parallel to the transmitted beam. The optical collimator 14-(N+1) outputs the local beam to the polarized beam splitter 42.

[0072] As shown in Figure 7, the polarizing beam splitter 42 transmits the horizontal component of the transmission beam and radiates the horizontal component into space as the transmission beam. As shown in Figure 7, the polarizing beam splitter 42 uses the vertical component in the transmitted beam to detect the phase detection beam BP1~BP N The beam is then reflected towards the beam focusing unit 17. The vertical component is the dither component. The polarizing beam splitter 42 also reflects the local beam towards the beam focusing unit 17.

[0073] In the above embodiment 4, the optical beam transmitting device 2 is configured such that the frequency shift unit 12 comprises N optical frequency converters 61 that shift the frequency of each laser beam that has passed through N transmission paths out of (N+1) transmission paths by a frequency shift amount, N polarization rotators 62 that rotate the polarization direction of the laser beam after the frequency shift by each optical frequency converter 61, N polarization demultiplexers 63 that demultiplex the laser beam after the polarization direction rotation by each polarization rotator 62 according to the polarization component of the laser beam, N phase modulators 64 that modulate the phase of one of the laser beams after the demultiplexing by each polarization demultiplexer 63, and N photosynthesizers 65 that combine the other laser beam after the demultiplexing by each polarization demultiplexer 63 and the phase-modulated laser beam by each phase modulator 64, and output the combined laser beam to the beam conversion unit 14. Therefore, the optical beam transmitter 2 does not emit a transmission beam superimposed with a dither signal into space, but rather phase detection beams BP1~BP having a dither component. N The dither signal can be reflected back towards the beam focusing unit 17. As a result, the transmitted beam, which does not have a dither signal superimposed on it, is CBC'd, thus suppressing the degradation of the transmitted combined beam quality. Additionally, phase detection beams BP1~BP, which do not have dither signals superimposed on them, are used. N Since this is supplied to the photoelectric conversion unit 18, the phase detection accuracy can be improved.

[0074] Embodiment 5. Embodiment 5 describes an optical beam transmitting device 2 in which the frequency shifting unit 12 includes N modulation signal superposition units 56.

[0075] Figure 8 is a diagram showing the internal configuration of the frequency shifter 12-n (n=1,···,N) of the frequency shifting unit 12. In Figure 8, the same reference numerals as in Figure 6 indicate the same or equivalent parts, so a detailed explanation is omitted. In the example in Figure 8, the optical demultiplexing unit 15 is realized by a polarization beam splitter 42. The frequency shifter 12-n (n=1,···,N) comprises an optical frequency converter 51, an optical splitter 52, a 90-degree rotator 53, a phase modulator 54, a modulated signal superposition unit 56, and a photosynthesizer 57.

[0076] The modulated signal superposition unit 56 superimposes the modulated signal onto the other laser beam after it has been split into two by the optical splitter 52. The modulated signal superposition unit 56 outputs the laser light after the modulated signal superposition to the photosynthesizer 57. The photosynthesizer 57 combines the laser light after modulation signal superimposition by the modulation signal superimposition unit 56 and the laser light after dither signal superimposition by the phase modulator 54. The photosynthesizer 57 outputs the synthesized laser light to the beam conversion unit 14 via the light amplification unit 13.

[0077] Next, the operation of the frequency shifter 12-n (n=1,···,N) shown in Figure 8 will be explained. However, it is the same as the frequency shifter 12-n shown in Figure 6, except for the modulation signal superposition section 56 and the photosynthesizer 57. Therefore, only the operation of the modulation signal superposition section 56 and the photosynthesizer 57 will be explained here.

[0078] The output power of the transmitted combined beam output from the polarized beam splitter 42 is generally limited by nonlinearities such as stimulated Brilluin scattering (SBS) in the fiber. SBS (Single Beam Synchronization) is more likely to occur when the line width of the incident light is narrower, and less likely to occur when the line width is wider. The modulation signal superposition unit 56 modulates the laser light with a broadband signal, thereby widening the line width of the transmitted beam.

[0079] When the other laser beam after the two-way split is supplied from the optical splitter 52, the modulation signal superposition unit 56 modulates the laser beam by superimposing, for example, an externally supplied broadband signal as a modulation signal onto the other laser beam after the two-way split. The modulated signal superposition unit 56 outputs the laser light after the modulated signal superposition to the photosynthesizer 57. The photosynthesizer 57 combines the laser light after modulation signal superimposition by the modulation signal superimposition unit 56 and the laser light after dither signal superimposition by the phase modulator 54. The photosynthesizer 57 outputs the resulting laser light to the optical amplifier 13-n.

[0080] In the above embodiment 5, the frequency shift unit 12 further includes N modulation signal superposition units 56 that superimpose a modulation signal onto the other laser beam after the two-way split by each optical splitter 52, and each photosynthesizer 57 combines the laser beam after modulation signal superimposition by each modulation signal superposition unit 56 with the laser beam after phase modulation by each phase modulator 54, and outputs the combined laser beam to the beam conversion unit 14. Thus, the optical beam transmitting device 2 can alleviate the limitation on the output power of the transmitted combined beam due to nonlinearities such as SBS.

[0081] Embodiment 6. Embodiment 6 describes an optical beam transmitting device 2 in which the frequency shifting unit 12 includes N modulation signal superposition units 66.

[0082] Figure 9 is a diagram showing the internal configuration of the frequency shifter 12-n (n=1,···,N) of the frequency shifting unit 12. In Figure 9, the same reference numerals as in Figure 7 indicate the same or equivalent parts, so a detailed explanation is omitted. In the example in Figure 9, the optical demultiplexing unit 15 is realized by a polarization beam splitter 42. The frequency shifter 12-n (n=1,···,N) comprises an optical frequency converter 61, a polarization rotator 62, a polarization demultiplexer 63, a phase modulator 64, a modulation signal superposition unit 66, and a photosynthesizer 67.

[0083] The modulation signal superposition unit 66 superimposes the modulation signal onto the other laser beam that has been split into two by the polarization demultiplexer 63. The modulated signal superposition unit 66 outputs the laser light after the modulated signal superposition to the photosynthesizer 67. The photosynthesizer 67 combines the laser light after modulation by the modulation signal superimposition unit 66 with the laser light after phase modulation by the phase modulator 64. The photosynthesizer 67 outputs the synthesized laser light to the beam conversion unit 14 via the light amplification unit 13.

[0084] Next, the operation of the frequency shifter 12-n (n=1,···,N) shown in Figure 9 will be explained. However, it is the same as the frequency shifter 12-n shown in Figure 7, except for the modulation signal superposition section 66 and the photosynthesizer 67. Therefore, only the operation of the modulation signal superposition section 66 and the photosynthesizer 67 will be explained here.

[0085] The output power of the transmitted combined beam output from the polarized beam splitter 42 is generally limited by the nonlinearity of the fiber, such as SBS. SBS (Single Beam Synchronization) is more likely to occur when the line width of the incident light is narrower, and less likely to occur when the line width is wider. The modulation signal superposition unit 66 modulates the laser light with a broadband signal, thereby widening the line width of the transmitted beam.

[0086] When the modulation signal superimposition unit 66 receives the other laser beam after two-way demultiplication from the polarization demultiplication unit 63, it modulates the laser beam by superimposing, for example, an externally supplied broadband signal as a modulation signal onto the other laser beam after two-way demultiplication. The modulated signal superposition unit 66 outputs the laser light after the modulated signal superposition to the photosynthesizer 67. The photosynthesizer 67 combines the laser light after modulation by the modulation signal superimposition unit 66 with the laser light after phase modulation by the phase modulator 64. The photosynthesizer 67 outputs the resulting laser light to the optical amplifier 13-n.

[0087] In the above embodiment 6, the frequency shift unit 12 further includes N modulation signal superposition units 66 that superimpose a modulation signal onto the other laser beam after each polarization demultiplexer 63 has demultiplexed, and each photosynthesizer 67 combines the laser beam after modulation signal superimposition by each modulation signal superposition unit 66 with the laser beam after phase modulation by each phase modulator 64, and outputs the combined laser beam to the beam conversion unit 14. Thus, the optical beam transmitting device 2 can alleviate the limitations on the output power of the transmitted combined beam due to nonlinearities such as SBS.

[0088] Furthermore, this disclosure allows for free combination of each embodiment, modification of any component in each embodiment, or omission of any component in each embodiment. [Explanation of Symbols]

[0089] 1 Laser light source, 2 Optical beam transmitter, 11 Optical distribution unit, 12 Frequency shift unit, 12-1~12-N frequency shifter, 13 Optical amplification unit, 13-1~13-N optical amplifier, 14 Beam conversion unit, 14-1~14-(N+1) optical collimator, 15 Optical demultiplexer, 16 Control unit, 17 Beam focusing unit, 18 Photoelectric conversion unit, 19 Phase locking unit, 21 Frequency discrimination unit, 22 Reference oscillator, 23 Comparison unit, 24 Loop filter, 25 Voltage controlled oscillator, 31 Optical frequency converter, 32 High-frequency signal generator, 33 Optical phase modulator, 41 Polarization rotation unit, 41-1~41-(N+1) polarization rotator, 42 Polarized beam splitter, 51 Optical frequency converter, 52 Optical brancher, 53 90-degree rotator, 54 Phase modulator, 55 Photosynthesizer, 56 Modulated signal superposition section, 57 Photosynthesizer, 61 Optical frequency converter, 62 Polarization rotator, 63 Polarization demultiplexer, 64 Phase modulator, 65 Photosynthesizer, 66 Modulated signal superposition section, 67 Photosynthesizer, L-1~L-(N+1) Transmission line.

Claims

1. An optical distribution unit that distributes the laser light output from a laser light source to (N (where N is an integer greater than or equal to 2) + 1) transmission lines, A frequency shifting unit that shifts the frequency of laser light that has passed through N transmission paths out of the (N+1) transmission paths, A beam conversion unit converts the N laser beams after frequency shifting by the frequency shift unit into parallel transmission beams, and converts the laser beam that has passed through the remaining one transmission path among the (N+1) transmission paths into a local beam parallel to the transmission beam. A part of each of the N transmission beams is radiated into space, the remainder of each of the N transmission beams is reflected as a phase detection beam, and an optical demultiplexer reflects the local beam, A control unit detects the frequency difference between the frequency of each phase detection beam after reflection by the optical demultiplexer and the frequency of the local beam after reflection by the optical demultiplexer, and controls the respective frequency shift amount based on the respective frequency difference. A light beam transmitting device equipped with the following features.

2. The control unit, In addition to controlling the amount of each frequency shift based on the respective frequency difference, The phase difference between the phase of each phase detection beam after reflection by the optical demultiplexer and the phase of the local beam after reflection by the optical demultiplexer is detected, and the phase of the laser light that has passed through each of the N transmission paths is controlled based on these phase differences. The optical beam transmitting device according to claim 1, characterized by the features described above.

3. An optical amplification unit amplifies the N laser beams after frequency shifting by the frequency shifting unit and outputs the amplified N laser beams to the beam conversion unit. The optical beam transmitting device according to claim 1 or 2, characterized by comprising the above.

4. The aforementioned optical wave demultiplexer is, This is a polarization beam splitter that performs radiation and reflection of each transmitted beam according to the polarization direction of each transmitted beam, and reflects the local beam. The optical beam transmitting device according to claim 1, characterized by the features described above.

5. A polarization rotation unit rotates the polarization direction of each of the N laser beams after the frequency shift by the frequency shift unit, and also rotates the polarization direction of the laser beam that has passed through the remaining transmission path, and outputs the laser beam with the rotated polarization direction to the beam conversion unit. The optical beam transmitting device according to claim 4, characterized by comprising the above.

6. The frequency shifting unit is N optical frequency converters, which shift the frequency of each laser beam that has passed through N transmission paths by a frequency shift amount, among the (N+1) transmission paths, N optical splitters that split the laser light after frequency shifting by each optical frequency converter into two, N 90-degree rotators rotate the polarization direction of one of the laser beams after it has been split into two by each optical splitter by 90 degrees, N phase modulators that modulate the phase of the laser beam after it has been rotated 90 degrees by each of the 90-degree rotators, N photosynthesizers that combine the other laser beam after splitting by each optical splitter and the phase-modulated laser beam after phase modulation by each phase modulator, and output the combined laser beam to the beam conversion unit. The optical beam transmitting device according to claim 4, characterized by comprising the above.

7. The frequency shifting unit is N optical frequency converters, which shift the frequency of each laser beam that has passed through N transmission paths by a frequency shift amount, among the (N+1) transmission paths, N polarization rotators rotate the polarization direction of the laser light after frequency shifting by each optical frequency converter, N polarization demultiplexers that demultiplex the laser light after polarization direction rotation by each polarization rotator according to the polarization component of the laser light, N phase modulators that modulate the phase of one of the laser beams after each polarization demultiplexer has demultiplexed it, N photosynthesizers that combine the other laser beam after being split into two by each polarization demultiplexer and the laser beam after being phase-modulated by each phase modulator, and output the combined laser beam to the beam conversion unit. The optical beam transmitting device according to claim 4, characterized by comprising the above.

8. The frequency shifting unit is The system further comprises N modulation signal superposition units that superimpose a modulation signal onto the other laser beam after each optical splitter has produced two separate beams. Each photosynthetic organ, The laser light after modulation by each modulation signal superimposition unit and the laser light after phase modulation by each phase modulator are combined, and the combined laser light is output to the beam conversion unit. The optical beam transmitting device according to claim 6.

9. The frequency shifting unit is It further comprises N modulation signal superposition units that superimpose a modulation signal onto the other laser beam after each polarization demultiplexer has demultiplied it, Each photosynthetic organ, The laser light after modulation by each modulation signal superimposition unit and the laser light after phase modulation by each phase modulator are combined, and the combined laser light is output to the beam conversion unit. The optical beam transmitting device according to claim 7, characterized in that it is as described in the present invention.

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