JP6045192B2 - Optical fiber microwave transmission device and composite optical fiber microwave transmission device - Google Patents

Description

  The present invention relates to an optical fiber microwave transmission device and a composite optical fiber microwave transmission device that compensate for a phase variation of a microwave signal due to a variation in the length of the optical fiber in a system for transmitting a microwave signal far away by an optical fiber. It is about.

In general, when a light wave propagates in an optical fiber, if there is a temperature change or vibration with respect to the optical fiber around the optical fiber, the optical path length changes because expansion or contraction of the optical fiber or a change in refractive index occurs. Therefore, in RoF (Radio On Fiber) transmission in which a microwave signal is superimposed on a light wave and transmitted through an optical fiber, the phase variation of the microwave signal demodulated after the optical fiber transmission is caused by the variation in the optical path length of the optical fiber. And delay time fluctuations occur.
For this reason, in order to improve the phase stability of the demodulated microwave signal, it is necessary to compensate for variations in the optical path length of the optical fiber that is the transmission path.

  Conventionally, in this type of optical fiber transmission system, a method has been proposed in which the amount of change in the optical path length of an optical fiber is measured and the amount of change is compensated based on the measurement result (see, for example, FIG. 1 of Non-Patent Document 1).

  In the conventional optical path length variation compensation method disclosed in Non-Patent Document 1, first, the laser light output from the laser (ECLD) is branched into two by the first optical coupler (10 dB coupler). Then, one of the branched laser beams includes a first optical circulator, an optical fiber stretcher that changes the length of the optical fiber (delay line), the optical fiber that is a transmission path, and a second optical circulator ( (optical circuit) in order. The laser beam output from the second optical circulator is branched by a second optical coupler (3 dB coupler). One of the branched laser beams is output as a reference beam, and the other laser beam is returned to the second optical circulator via an acousto-optic light modulator (AOM), and the optical fiber is transmitted from the second optical circulator. Go back and forth.

  The angular frequency of the reciprocating laser light is shifted by the AOM. The reciprocating laser light has its optical path switched by the first optical circulator, and is combined with the other laser light branched by the first optical coupler in a third optical coupler (3 dB coupler).

  The combined light output from the third optical coupler is converted into an electric signal by a photoelectric converter (PD). Here, the angular frequency of the converted electrical signal is the angular frequency of the microwave signal shifted by the AOM. In the case where the optical path length of the optical fiber is changed due to a temperature change or the like, the phase of the beat signal of the photoelectrically converted electric signal changes according to the change of the optical path length.

  Then, the phase of the reference signal from the reference signal source (synth. 55 MHz) and the beat signal from the PD is compared by a phase detector (PSD or DPFD) to match the phase of the beat signal with a desired phase. For example, a control signal such as a voltage is output. This control signal is input to the optical fiber stretcher via a loop filter, and the phase of the optical signal is shifted by an amount corresponding to the control signal.

Here, a feedback circuit is configured by repeating an operation in which a control signal obtained from a beat signal from the PD is input to the optical fiber stretcher. The feedback circuit performs control to compensate for fluctuations in the optical path length due to disturbance.
Therefore, one of the laser beams branched by the second optical coupler also has high phase stability.

Musha, et. al. "Robust and precision length correction of 25-km fiber for distribution", 2005 Digest of the LE4, Tope4. 123, 2005. , (Figure 1)

  However, in the conventional optical fiber microwave transmission device, fluctuations in the optical path length can be achieved by directly stretching the length of the optical fiber with an optical fiber stretcher in response to fluctuations in the optical path length (phase) of the optical fiber that is the transmission path. Was compensated. For this reason, the compensation range for the fluctuation amount of the optical path length is limited to the variable length range of the optical fiber stretcher. Usually, the variable range of the optical fiber stretcher is about several millimeters, which is at most on the order of cm.

  On the other hand, the temperature characteristic of the delay time of the optical fiber is about several tens of ps / km / ° C. For example, assuming that the temperature coefficient of delay is 10 ps / km / ° C., if a temperature variation of 10 ° C. occurs in a 1 km fiber, a delay time variation of 100 ps occurs. This corresponds to a fiber length of about 33 mm and exceeds the variable range of the optical fiber stretcher. Furthermore, when the temperature fluctuation range is expanded or the fiber length is increased, the optical fiber stretcher cannot cope.

Further, when the delay time is controlled by the optical fiber stretcher, the response speed is limited because the optical fiber is pulled by a piezoelectric element or the like.
Thus, in the conventional configuration, it is difficult to cope with large optical path length fluctuations (corresponding to delay time fluctuations), and there is a problem that high-speed control cannot be accommodated.

  The present invention has been made in order to solve the above-described problems. An optical fiber microwave that can compensate for variations in optical path length by compensating for phase variations even with large variations in optical path length. An object of the present invention is to provide a transmission device and a composite optical fiber microwave transmission device.

An optical fiber microwave transmission device according to the present invention is disposed at a subsequent stage of an electro-optic conversion unit that outputs modulated light intensity-modulated by an input modulation microwave signal, and selectively selects an optical path of the modulated light. An optical path switching means for switching to the optical path switching means, a part of the modulated light outputted from the electro-optic conversion means via the optical path switching means and the transmission optical fiber, the partial light reflection means for reflecting the transmission light to the transmission optical fiber and transmitting the rest, and an optical part The first photoelectric conversion means for converting the modulated light transmitted through the reflection means into a first microwave signal, and the modulated light output from the optical partial reflection means via the transmission optical fiber and the optical path switching means are converted to the second micro signal. Based on the second photoelectric conversion means for converting to a wave signal, the phase of the second microwave signal converted by the second photoelectric conversion means and the phase of the reference microwave signal And a phase synchronization means for generating a signal, the phase synchronization means comprises a second microwave signal converted by the second photoelectric conversion unit, a first differential micro which is the difference component between the modulating microwave signal First frequency converting means for generating a wave signal, second frequency converting means for converting the angular frequency of the first differential microwave signal generated by the first frequency converting means, and the phase of the reference microwave signal And a phase comparison unit that generates a phase difference signal based on the phase of the first differential microwave signal converted by the second frequency conversion unit, and a phase difference signal generated by the phase comparison unit And a modulation microwave generating means for generating a modulation microwave signal in which the angular frequency is controlled .

  According to the present invention, since it is configured as described above, even if there is a large variation in the optical path length, it is possible to compensate for the variation in the optical path length by compensating for the phase variation.

It is a block diagram which shows the structure of the optical fiber microwave transmission apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the flow of the optical and electric signal of the optical fiber microwave transmission apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the optical fiber microwave transmission apparatus which concerns on Embodiment 2 of this invention. It is a block diagram which shows the structure of the optical fiber microwave transmission apparatus which concerns on Embodiment 3 of this invention. It is a block diagram which shows the structure of the composite-type optical fiber microwave transmission apparatus which concerns on Embodiment 4 of this invention. It is a block diagram which shows the structure of the optical fiber microwave transmission apparatus which concerns on Embodiment 5 of this invention. It is a block diagram which shows the structure of the optical fiber microwave transmission apparatus which concerns on Embodiment 6 of this invention. It is a block diagram which shows the structure of the optical fiber microwave transmission apparatus which concerns on Embodiment 7 of this invention. It is a block diagram which shows the structure of the optical fiber microwave transmission apparatus which concerns on Embodiment 8 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
1 is a block diagram showing a configuration of an optical fiber microwave transmission device according to Embodiment 1 of the present invention. In the figure, the optical fiber is drawn with a solid line, and the electric wire is drawn with a broken line (the same applies hereinafter).
As shown in FIG. 1, the optical fiber microwave transmission apparatus includes an electro-optic conversion means 1, an optical circulator (optical path switching means) 2, a transmission optical fiber 3, an optical partial reflector (optical partial reflection means) 4, a first photoelectric converter. It comprises a conversion means 5, a second photoelectric conversion means 6, a reference signal source 7, and a phase synchronization circuit (PLL, phase synchronization means) 8.

  The electro-optic conversion means 1 generates modulated light that is intensity-modulated with a modulating microwave signal from the outside (second microwave distributor 88). The modulated light generated by the electro-optic conversion means 1 is output to the optical circulator 2.

The optical circulator 2 is connected to the electro-optic conversion means 1, the transmission optical fiber 3, and the second photoelectric conversion means 6, and outputs modulated light from the electro-optic conversion means 1 to the transmission optical fiber 3. The modulated light is output to the second photoelectric conversion means 6.
The transmission optical fiber 3 transmits the modulated light from the optical circulator 2 to the optical partial reflection mirror 4 and transmits the modulated light from the optical partial reflection mirror 4 to the optical circulator 2.

The optical partial reflection mirror 4 reflects a part of the modulated light from the transmission optical fiber 3 to the transmission optical fiber 3 and transmits the remaining part. The modulated light transmitted through the partial light reflecting mirror 4 is output to the first photoelectric conversion means 5.
The first photoelectric conversion means 5 photoelectrically converts the modulated light from the light partial reflection mirror 4 into an electric signal (first microwave signal).

The second photoelectric conversion means 6 photoelectrically converts the modulated light from the optical circulator 2 into an electric signal (second microwave signal). The second microwave signal photoelectrically converted by the second photoelectric conversion means 6 is output to the second frequency conversion means 83 of the phase synchronization circuit 8.
The reference signal source 7 generates a microwave reference signal (reference microwave signal). The reference microwave signal generated by the reference signal source 7 is output to the first microwave distributor 81 of the phase synchronization circuit 8.

  The phase synchronization circuit 8 is based on the phase of the second microwave signal from the second photoelectric conversion means 6 and the phase of the reference microwave signal from the reference signal source 7. A wave signal is generated. The phase synchronization circuit 8 includes a first microwave distributor (microwave distributor) 81, first to third frequency converters 82 to 84, a phase comparator 85, a loop filter (low-pass filter) 86, and a voltage control type. An oscillator (VCO: Voltage Controlled Oscillator, modulation microwave generation means) 87 and a second microwave distributor 88 are included.

The first microwave distributor 81 branches the reference microwave signal from the reference signal source 7 into two. One reference microwave signal branched by the first microwave distributor 81 is output to the first frequency converter 82, and the other reference microwave signal is output to the phase comparator 85.
The first frequency conversion means 82 converts the angular frequency of the reference microwave signal from the first microwave distributor 81 to three times. The reference microwave signal whose angular frequency has been converted by the first frequency conversion means 82 is output to the second frequency conversion means 83.

  Based on the second microwave signal from the second photoelectric conversion means 6 and the reference microwave signal from the first frequency conversion means 82, the second frequency conversion means 83 determines the difference and level of those frequencies. A first differential microwave signal having a phase difference is generated. The first differential microwave signal generated by the second frequency conversion unit 83 is output to the third frequency conversion unit 84.

  Based on the first differential microwave signal from the second frequency conversion unit 83 and the modulation microwave signal from the second microwave distributor 88, the third frequency conversion unit 84 determines the frequency of those frequencies. A second differential microwave signal having a difference and a phase difference is generated. The second differential microwave signal generated by the third frequency conversion unit 84 is output to the phase comparison unit 85.

  The phase comparison unit 85 compares the reference microwave signal from the first microwave distributor 81 with the second differential microwave signal from the third frequency conversion unit 84 and calculates the phase fluctuation amount (phase difference). Measurement is performed to generate a phase difference signal obtained by converting the phase difference into an electric signal. The phase difference signal generated by the phase comparison unit 85 is output to the loop filter 86.

The loop filter 86 suppresses short-term fluctuations with respect to the phase difference signal from the phase comparison unit 85. The phase difference signal whose fluctuation is suppressed by the loop filter 86 is output to the VCO 87.
Based on the phase difference signal from the loop filter 86, the VCO 87 generates a modulation microwave signal whose oscillation frequency is controlled so as to cancel the phase difference between the second difference microwave signal and the reference microwave signal. is there. The modulation microwave signal generated by the VCO 87 is output to the second microwave distributor 88.

  The second microwave distributor 88 branches the modulating microwave signal from the VCO 87 into two. One modulation microwave signal branched by the second microwave distributor 88 is output to the electro-optic conversion means 1, and the other modulation microwave signal is output to the third frequency conversion means 84.

Next, the operation of the optical fiber microwave transmission device configured as described above will be described. FIG. 2 is a diagram showing the flow of light and electric signals in the optical fiber microwave transmission device according to Embodiment 1 of the present invention.
In the operation of the optical fiber microwave transmission device, as shown in FIG. 2, first, the electro-optic conversion means 1 uses modulated light that has been intensity-modulated with a modulating microwave signal from the outside (second microwave distributor 88). Output (step ST1).

Next, the optical circulator 2 outputs the modulated light from the electro-optic conversion means 1 to the transmission optical fiber 3, and the transmission optical fiber 3 transmits this modulated light to the optical partial reflection mirror 4 (step ST2).
Next, the optical partial reflection mirror 4 reflects a part of the modulated light from the transmission optical fiber 3 to the transmission optical fiber 3 and transmits the remaining part (step ST3).
Next, the first photoelectric conversion means 5 photoelectrically converts the transmitted light (modulated light) from the light partial reflection mirror 4 into a first microwave signal (step ST4).

On the other hand, the transmission optical fiber 3 transmits the reflected light (modulated light) from the optical partial reflection mirror 4 to the optical circulator 2, and the optical circulator 2 outputs the modulated light to the second photoelectric conversion means 6 (step). ST5).
Next, the second photoelectric conversion means 6 photoelectrically converts the modulated light from the optical circulator 2 into a second microwave signal (step ST6).

  Here, when an environmental change such as a temperature change occurs in the transmission optical fiber 3, the phase of the modulated light propagated through the transmission optical fiber 3 changes. Therefore, the first microwave signal that has been transmitted through the light partial reflection mirror 4 and photoelectrically converted by the first photoelectric conversion means 5 and the light reflected by the light partial reflection mirror 4 are subjected to photoelectric conversion by the second photoelectric conversion means 6. In addition, phase fluctuation occurs in the second microwave signal.

On the other hand, it is known that there is a relationship of the formula (1) between the phase Φ of the microwave signal and its angular frequency ω.
ω = dΦ / dt (1)
Therefore, the phase variation ΔΦ is expressed by the equation (2).
ΔΦ = ∫ωdt (2)
Thus, it can be seen that the phase fluctuation ΔΦ of the first microwave signal output from the first photoelectric conversion means 5 can be controlled by controlling the angular frequency ω of the modulation microwave signal to the electro-optic conversion means 1. . Therefore, the angular frequency ω is controlled by the phase synchronization circuit 8 using the second microwave signal output from the second photoelectric conversion means 6 (step ST7).

Hereinafter, the angular frequency control by the phase synchronization circuit 8 will be described while showing the frequency and phase of the modulated light or the microwave signal in the main part of FIG.
First, when the angular frequency of the reference microwave signal from the reference signal source 7 is ωm and the angular frequency of the modulation microwave signal from the VCO 87 is ωm + ΔΦ0 / Δt, the modulated light output from the electro-optic conversion means 1 is angular frequency. Modulated by ωm + ΔΦ0 / Δt.

  The modulated light from the electro-optic conversion means 1 propagates through the transmission optical fiber 3 via the optical circulator 2. Here, assuming that the amount of change in the transmission phase when the optical path length varies due to the environmental variation of the transmission optical fiber 3 is ΔΦ1, the first photoelectric conversion means 5 transmits the first photoelectric conversion means 5 and performs photoelectric conversion. The angular frequency of 1 microwave signal is ωm + ΔΦ0 / Δt + ΔΦ1 / Δt.

  On the other hand, the angular frequency of the modulated light that reciprocates through the transmission optical fiber 3 by being reflected by the optical partial reflection mirror 4 is subjected to the phase fluctuation caused by the transmission optical fiber 2 twice. Therefore, the angular frequency of the second microwave signal photoelectrically converted by the second photoelectric conversion means 6 after reciprocating is ωm + ΔΦ0 / Δt + 2 · ΔΦ1 / Δ.

On the other hand, a part of the reference microwave signal (angular frequency ωm) from the reference signal source 7 is converted to a triple frequency by the first frequency conversion means 82, and the angular frequency becomes 3ωm.
Then, for example, a mixer or the like is used as the second frequency conversion unit 83, and a difference component between the second microwave signal from the second photoelectric conversion unit 6 and the reference microwave signal from the first frequency conversion unit 82 is calculated. When output, a first differential microwave signal having an angular frequency as shown in Expression (3) is output.
3ωm− (ωm + ΔΦ0 / Δt + 2 · ΔΦ1 / Δt) = 2ωm−ΔΦ0 / Δt−2 · ΔΦ1 / Δt (3)

Further, for example, a mixer or the like is used as the third frequency conversion means 84, and the first differential microwave signal from the second frequency conversion means 83 and the modulation microwave from the VCO 87 (second microwave distributor 88). When a difference component from the signal is output, a second differential microwave signal having an angular frequency as shown in Expression (4) is output.
(2ωm−ΔΦ0 / Δt−2 · ΔΦ1 / Δt) − (ωm + ΔΦ0 / Δt) = ωm−2ΔΦ0 / Δt−2 · ΔΦ1 / Δt (4)

Then, the phase of the second differential microwave signal and the phase of the reference microwave signal from the reference signal source 7 are compared by the phase comparison means 85, and the modulation frequency is controlled by the VCO 87 so as to cancel the difference. Generate a microwave signal.
Therefore, when both input signals to the phase comparison unit 85 are equal, Expression (5) is established, and therefore, a relation as in Expression (6) is established.
ωm = ωm−2ΔΦ0 / Δt−2 · ΔΦ1 / Δt (5)
ΔΦ0 / Δt = −ΔΦ1 / Δt (6)

  At this time, the angular frequency (ωm + ΔΦ0 / Δt + ΔΦ1 / Δt) of the first microwave signal transmitted through the light partial reflection mirror 4 and photoelectrically converted by the first photoelectric conversion means 5 is expressed by the above equation (6). Since it becomes ωm, the phase fluctuation component due to the transmission optical fiber 3 can be canceled out and becomes the same as the output signal of the reference signal source 7. In the above description, the initial offset of the fixed optical path length (phase) is omitted.

  As described above, according to the first embodiment, the configuration is such that the modulated light reciprocating near the transmission destination of the modulated light is monitored and the angular frequency of the modulated light is controlled. It is possible to compensate for phase fluctuation after transmission. In the conventional configuration, the length of the phase variation of the direct transmission path is compensated by an optical fiber stretcher, etc., so that the controllable length and response speed of an optical path length control device such as an optical fiber stretcher are limited. However, in the optical fiber microwave transmission device according to the first embodiment, the phase variation can be compensated by the frequency control of the modulation microwave signal, so that the length capable of phase compensation can be easily expanded.

Embodiment 2. FIG.
FIG. 3 is a block diagram showing a configuration of an optical fiber microwave transmission device according to Embodiment 2 of the present invention. The optical fiber microwave transmission device according to the second embodiment shown in FIG. 3 includes the microwave signal source 9, the third microwave distributor 10 and the optical fiber microwave transmission device according to the first embodiment shown in FIG. The fifth and sixth frequency conversion means 11 and 12 are added. Other configurations are the same, and the same reference numerals are given and description thereof is omitted. In FIG. 3, the description of the internal configuration of the phase synchronization circuit 8 is omitted (the same applies hereinafter).

  The microwave signal source 9 generates a third microwave signal having a predetermined angular frequency. The third microwave signal generated by the reference signal source 7 is output to the third microwave distributor 10.

  The third microwave distributor 10 branches the third microwave signal from the microwave signal source 9 into two. One third microwave signal branched by the third microwave distributor 10 is output to the fifth frequency converter 11, and the other third microwave signal is supplied to the sixth frequency converter 12. Is output.

The fifth frequency conversion means 11 is based on the modulation microwave signal from the second microwave distributor 88 of the phase synchronization circuit 8 and the third microwave signal from the third microwave distributor 10. A fourth differential microwave signal having a difference in frequency and a phase difference is generated. The fourth differential microwave signal generated by the fifth frequency converter 11 is output to the electro-optic converter 1.
The electro-optic conversion means 1 generates modulated light using the fourth differential microwave signal instead of the modulating microwave signal in the first embodiment.

Based on the second microwave signal from the second photoelectric conversion means 6 and the third microwave signal from the third microwave distributor 10, the sixth frequency conversion means 12 A fifth differential microwave signal having a difference and a phase difference is generated. The fifth differential microwave signal generated by the sixth frequency conversion unit 12 is output to the second frequency conversion unit 83 of the phase synchronization circuit 8.
Note that the second frequency conversion means 83 generates the first differential microwave signal using the fifth differential microwave signal instead of the second microwave signal in the first embodiment.

  As in the first embodiment, the angular frequency of the reference microwave signal from the reference signal source 7 is ωm, the angular frequency of the modulation microwave signal from the phase synchronization circuit 8 is ωm + ΔΦ0 / Δt, If the angular frequency of the third microwave signal from the wave signal source 9 is ωm2, the angular frequency of the fourth differential microwave signal output from the fifth frequency converting means 11 is ωm + ωm2 + ΔΦ0 / Δt.

  The modulated light intensity-modulated by the third differential microwave signal in the electro-optic conversion means 1 undergoes phase fluctuation (ΔΦ1 / Δt) in the transmission optical fiber 3 or the like. Therefore, the angular frequency of the first microwave signal transmitted through the light partial reflection mirror 4 and photoelectrically converted by the first photoelectric conversion means 5 is ωm + ωm2 + ΔΦ0 / Δt + ΔΦ1 / Δt.

  On the other hand, the modulated light reciprocated through the transmission optical fiber 3 by being reflected by the optical partial reflection mirror 4 is subjected to the phase fluctuation caused by the transmission optical fiber 3 twice. Therefore, the angular frequency of the second microwave signal photoelectrically converted by the second photoelectric conversion means 6 after reciprocating is ωm + ωm2 + ΔΦ0 / Δt + 2 · ΔΦ1 / Δ.

On the other hand, a part of the reference microwave signal (angular frequency ωm) from the reference signal source 7 is converted to a triple frequency by the first frequency conversion means 82, and the angular frequency becomes 3ωm.
Then, for example, a mixer or the like is used as the second frequency conversion unit 83, and a difference component between the second microwave signal from the second photoelectric conversion unit 6 and the reference microwave signal from the first frequency conversion unit 82 is calculated. When output, a first differential microwave signal having an angular frequency as shown in Expression (7) is output.
3ωm− (ωm + ΔΦ0 / Δt + 2 · ΔΦ1 / Δt) = 2ωm−ΔΦ0 / Δt−2 · ΔΦ1 / Δt (7)

Then, for example, a mixer or the like is used as the sixth frequency conversion means 12, and when the difference component between the second microwave signal and the third microwave signal (ωm2) from the microwave signal source 9 is output, the angle The frequency is ωm + ΔΦ0 / Δt + 2 · ΔΦ1 / Δ.
This fifth differential microwave signal is output to the phase synchronization circuit 8 and controlled to cancel the difference from the reference microwave signal from the reference signal source 7 as in the first embodiment.
Therefore, when both input signals to the phase comparison unit 85 are equal, Expression (8) is established, and therefore, a relation as in Expression (9) is established.
ωm = ωm−2ΔΦ0 / Δt−2 · ΔΦ1 / Δt (8)
ΔΦ0 / Δt = −ΔΦ1 / Δt (9)

  At this time, the angular frequency (ωm + ωm2 + ΔΦ0 / Δt + ΔΦ1 / Δt) of the first microwave signal transmitted through the light partial reflection mirror 4 and photoelectrically converted by the first photoelectric conversion means 5 is expressed by the above equation (6). Since ωm + ωm2, the phase fluctuation component due to the transmission optical fiber 3 can be canceled out. The angular frequency of the first microwave signal is the sum of the angular frequency of the output signal of the reference signal source 7 and the angular frequency of the output signal of the microwave signal source 9. In the above description, the initial offset of the fixed optical path length (phase) is omitted.

  As described above, according to the second embodiment, the input signal to the electro-optic conversion means 1 and the output signal from the second photoelectric conversion means 6 are frequency-converted by the output signal from the same microwave signal source 9. Therefore, regardless of the angular frequency of the output signal from the reference signal source 7, by controlling the angular frequency of the output signal from the microwave signal source 9, a microwave signal having an arbitrary angular frequency is transmitted. It becomes possible to do.

Embodiment 3 FIG.
4 is a block diagram showing a configuration of an optical fiber microwave transmission device according to Embodiment 3 of the present invention. The optical fiber microwave transmission device according to the third embodiment shown in FIG. 4 is an optical circulator 2 of the optical fiber microwave transmission device according to the first embodiment shown in FIG. The optical partial reflection mirror 4 is changed to an optical multiplexer / demultiplexer (optical multiplexing / demultiplexing means) 14 and a Faraday rotary mirror (polarization rotating means) 15. Other configurations are the same, and the same reference numerals are given and description thereof is omitted.

  The PBS 13 transmits or reflects the input modulated light according to the polarization direction. Here, when the modulated light from the electro-optic conversion means 1 is linearly modulated light, the PBS 13 transmits this modulated light and outputs it to the transmission optical fiber 3, and the polarization direction from the transmission optical fiber 3 is 90. The modulated light rotated by the angle is reflected and output to the optical multiplexer 7.

The optical multiplexer / demultiplexer 14 branches the modulated light from the transmission optical fiber 3 into two. One modulated light branched by the optical multiplexer / demultiplexer 14 is output to the Faraday rotary mirror 15, and the other modulated light is output to the first photoelectric conversion means 5. The optical multiplexer / demultiplexer 14 outputs the reflected light (modulated light) from the Faraday rotary mirror 15 to the transmission optical fiber 3.
The Faraday rotator 15 rotates the polarization direction of the modulated light from the optical multiplexer / demultiplexer 14 by 90 degrees and reflects it to the optical multiplexer / demultiplexer 14.

  In this case, the modulated light output from the electro-optic conversion means 1 passes through the PBS 13 (proceeds from left to right in FIG. 4), is branched by the optical multiplexer / demultiplexer 14 via the transmission optical fiber 3, and one modulation is performed. Light is output to the Faraday rotary mirror 15. The Faraday rotary mirror 15 rotates the polarization direction of the modulated light by 90 degrees and reflects it to the optical multiplexer / demultiplexer 14.

  Then, this reflected light (modulated light) is transmitted through the optical multiplexer / demultiplexer 14 through the transmission optical fiber 3 in the opposite direction (proceeding from right to left in FIG. 4) and output to the PBS 13. Here, since the polarization direction of the modulated light reaching the PBS 13 is inclined by 90 degrees with respect to the polarization direction when transmitted through the PBS 13, it is reflected by the PBS 13 and output to the second photoelectric conversion means 6. (Reflected downward in FIG. 4).

  As described above, according to the third embodiment, the polarization direction of the modulated light from the transmission optical fiber 3 is rotated by 90 degrees by the Faraday rotary mirror 15 and reflected to the transmission optical fiber 3. In addition to the effects of the first embodiment, even if the polarization direction of light fluctuates in the transmission optical fiber 3, the polarization direction can be orthogonalized in the reciprocating process. Wave fluctuations can be canceled out.

Embodiment 4 FIG.
FIG. 5 is a block diagram showing a configuration of a composite optical fiber microwave transmission device according to Embodiment 4 of the present invention. The composite optical fiber microwave transmission device according to the fourth embodiment shown in FIG. 5 includes a plurality of optical fiber microwave transmission devices according to the first embodiment shown in FIG. 1 (two sets in FIG. 5). In this case, “a” is added to the reference numerals of the functional units in the second set of optical fiber microwave transmission devices). The reference signal source 7 is shared by each optical fiber microwave transmission device.
Thereby, it becomes possible to transmit the modulated light output from each of the electro-optic conversion means 1 and 1a to a plurality of points with the phases synchronized.

Embodiment 5. FIG.
6 is a block diagram showing a configuration of an optical fiber microwave transmission device according to Embodiment 5 of the present invention. The optical fiber microwave transmission device according to the fifth embodiment shown in FIG. 6 includes the first microwave distributor 81 and the phase synchronization circuit 8 of the optical fiber microwave transmission device according to the first embodiment shown in FIG. The first to third frequency converters 82 to 84 are removed, the second microwave distributor 88 is changed to the first microwave distributor 81b, and the first and second frequency converters 82b and 83b are added. It is. Other configurations are the same, and the same reference numerals are given and description thereof is omitted.

  The first microwave distributor 81b branches the modulating microwave signal from the VCO 87 into two. One modulation microwave signal branched by the first microwave distributor 81b is output to the electro-optic conversion means 1, and the other modulation microwave signal is output to the first frequency conversion means 82b.

  Based on the second microwave signal from the second photoelectric conversion means 6 and the modulation microwave signal from the first microwave distributor 81b, the first frequency conversion means 82b is based on the difference between the frequencies. And a first differential microwave signal having a phase difference. The first differential microwave signal generated by the first frequency conversion unit 82b is output to the second frequency conversion unit 83b.

  The second frequency conversion means 83b converts the angular frequency of the first differential microwave signal from the first frequency conversion means 82b to 1/2. The first differential microwave signal whose angular frequency has been converted by the second frequency conversion unit 83 b is output to the phase comparison unit 85.

  The phase comparison unit 85 compares the reference microwave signal from the reference signal source 7 with the first differential microwave signal from the second frequency conversion unit 83b to measure the phase fluctuation amount (phase difference). Then, a phase difference signal is generated by converting the phase difference into an electric signal.

  Here, as in the first embodiment, the angular frequency of the reference microwave signal from the reference signal source 7 is ωm, and the angular frequency of the modulating microwave signal from the VCO 87 is ωm + ΔΦ0 / Δt.

  The modulated light from the electro-optic conversion means 1 propagates through the transmission optical fiber 3 via the optical circulator 2. Here, assuming that the amount of change in the transmission phase when the optical path length varies due to the environmental variation of the transmission optical fiber 3 is ΔΦ1, the first photoelectric conversion means 5 transmits the first photoelectric conversion means 5 and performs photoelectric conversion. The angular frequency of 1 microwave signal is ωm + ΔΦ0 / Δt + ΔΦ1 / Δt.

  On the other hand, the angular frequency of the modulated light that reciprocates through the transmission optical fiber 3 by being reflected by the optical partial reflection mirror 4 is subjected to the phase fluctuation caused by the transmission optical fiber 2 twice. Therefore, the angular frequency of the second microwave signal photoelectrically converted by the second photoelectric conversion means 6 after reciprocating is ωm + ΔΦ0 / Δt + 2 · ΔΦ1 / Δ.

For example, a mixer or the like is used as the first frequency conversion unit 82b, and a difference component between the second microwave signal from the second photoelectric conversion unit 6 and the modulation microwave signal from the first microwave distributor 81b is obtained. When output, a first differential microwave signal having an angular frequency as shown in Expression (10) is output.
2ωm + 2 · ΔΦ0 / Δt + 2 · ΔΦ1 / Δt (10)

Further, for example, when a frequency divider or the like is used as the second frequency converting unit 83b and the first differential microwave signal from the first frequency converting unit 82b is converted into an angular frequency that is ½ times, Expression (11) A first differential microwave signal having an angular frequency as shown in FIG.
ωm + ΔΦ0 / Δt + ΔΦ1 / Δt (11)

Then, the phase of the first differential microwave signal and the phase of the reference microwave signal from the reference signal source 7 are compared by the phase comparison means 85, and the modulation frequency is controlled by the VCO 87 so as to cancel the difference. Generate a microwave signal.
Therefore, when both input signals to the phase comparison unit 85 are equal, the equation (12) is established, and therefore the relationship as the equation (13) is established.
ωm = ωm + ΔΦ0 / Δt + ΔΦ1 / Δt (12)
ΔΦ0 / Δt = −ΔΦ1 / Δt (13)

  At this time, the angular frequency (ωm + ΔΦ0 / Δt + ΔΦ1 / Δt) of the first microwave signal transmitted through the light partial reflection mirror 4 and photoelectrically converted by the first photoelectric conversion means 5 is expressed by the above equation (13). Since ωm, the phase fluctuation component due to the transmission optical fiber 3 can be canceled out. In the above description, the initial offset of the fixed optical path length (phase) is omitted.

  As described above, according to the fifth embodiment, the configuration is such that the modulated light reciprocating in the vicinity of the transmission destination of the modulated light is monitored and the angular frequency of the modulated light is controlled. It is possible to compensate for phase fluctuation after transmission.

Embodiment 6 FIG.
FIG. 7 is a block diagram showing a configuration of an optical fiber microwave transmission device according to Embodiment 6 of the present invention. The optical fiber microwave transmission device according to the sixth embodiment shown in FIG. 7 includes first and second frequency conversion means 82b from the phase synchronization circuit 8 of the optical fiber microwave transmission device according to the fifth embodiment shown in FIG. 83b and a microwave signal source 89 and first to fourth frequency conversion means 82c to 84c, 90 are added. Other configurations are the same, and the same reference numerals are given and description thereof is omitted.

  The microwave signal source 89 generates a fourth microwave signal having a predetermined angular frequency. The fourth microwave signal generated by the microwave signal source 89 is output to the first frequency conversion unit 82c and the third frequency conversion unit 84c.

  Based on the second microwave signal from the second photoelectric conversion means 6 and the fourth microwave signal from the microwave signal source 89, the first frequency conversion means 82c has a difference in frequency and a phase difference between them. A first differential microwave signal having the following is generated. The first differential microwave signal generated by the first frequency conversion unit 82c is output to the second frequency conversion unit 83c.

  Based on the first differential microwave signal from the first frequency conversion means 82c and the modulation microwave signal from the first microwave distributor 81b, the second frequency conversion means 83c A second differential microwave signal having a difference and a phase difference is generated. The second differential microwave signal generated by the second frequency conversion unit 83c is output to the third frequency conversion unit 84c.

  Based on the second differential microwave signal from the second frequency conversion unit 83c and the fourth microwave signal from the microwave signal source 89, the third frequency conversion unit 84c determines the difference and level of those frequencies. A third differential microwave signal having a phase difference is generated. The third differential microwave signal generated by the third frequency conversion unit 84 c is output to the fourth frequency conversion unit 90.

  The fourth frequency converting means 90 converts the angular frequency of the third differential microwave signal from the third frequency converting means 84c to ½ times. The third differential microwave signal whose angular frequency has been converted by the fourth frequency converting means 90 is output to the phase comparing means 85.

  The phase comparison unit 85 compares the reference microwave signal from the reference signal source 7 with the third differential microwave signal from the fourth frequency conversion unit 90 to measure the phase fluctuation amount (phase difference). Then, a phase difference signal is generated by converting the phase difference into an electric signal.

  Here, as in the first embodiment, the angular frequency of the reference microwave signal from the reference signal source 7 is ωm, the angular frequency of the modulating microwave signal from the VCO 87 is ωm + ΔΦ0 / Δt, and the microwave signal source 89 The angular frequency of the fourth microwave signal is ωm3 + ΔΦ3 / Δt.

  The modulated light from the electro-optic conversion means 1 propagates through the transmission optical fiber 3 via the optical circulator 2. Here, assuming that the amount of change in the transmission phase when the optical path length varies due to the environmental variation of the transmission optical fiber 3 is ΔΦ1, the first photoelectric conversion means 5 transmits the first photoelectric conversion means 5 and performs photoelectric conversion. The angular frequency of 1 microwave signal is ωm + ΔΦ0 / Δt + ΔΦ1 / Δt.

  On the other hand, the angular frequency of the modulated light that reciprocates through the transmission optical fiber 3 by being reflected by the optical partial reflection mirror 4 is subjected to the phase fluctuation caused by the transmission optical fiber 2 twice. Therefore, the angular frequency of the second microwave signal photoelectrically converted by the second photoelectric conversion means 6 after reciprocating is ωm + ΔΦ0 / Δt + 2 · ΔΦ1 / Δ.

When, for example, a mixer or the like is used as the first frequency conversion unit 82c, a difference component between the second microwave signal from the second photoelectric conversion unit 6 and the fourth microwave signal from the microwave signal source 89 is output. , A first differential microwave signal having an angular frequency as shown in Expression (14) is output.
ωm−ωm3 + ΔΦ0 / Δt + 2 · ΔΦ1 / Δt−ΔΦ3 / Δt (14)

Further, for example, a mixer or the like is used as the second frequency conversion unit 83c, and the first difference microwave signal from the first frequency conversion unit 82c and the modulation microwave signal from the first microwave distributor 81b are used. When the difference component is output, a second differential microwave signal having an angular frequency as shown in Expression (15) is output.
2ωm−ωm3 + 2 · ΔΦ0 / Δt + 2 · ΔΦ1 / Δt−ΔΦ3 / Δt (15)

Further, for example, a mixer or the like is used as the third frequency conversion unit 84c, and the difference component between the second differential microwave signal from the second frequency conversion unit 83c and the fourth microwave signal from the microwave signal source 89 is used. Is output, a third differential microwave signal having an angular frequency as shown in Expression (16) is output.
2ωm + 2 · ΔΦ0 / Δt + 2 · ΔΦ1 / Δt (16)

Further, for example, when a frequency divider is used as the fourth frequency converting unit 90 and the third differential microwave signal from the third frequency converting unit 84c is converted into an angular frequency that is ½ times, Expression (17) A third differential microwave signal having an angular frequency as shown in FIG.
ωm + ΔΦ0 / Δt + ΔΦ1 / Δt (17)

Then, the phase of the third differential microwave signal and the phase of the reference microwave signal from the reference signal source 7 are compared by the phase comparison means 85, and the modulation frequency is controlled by the VCO 87 so as to cancel the difference. Generate a microwave signal.
Therefore, when both input signals to the phase comparison means 85 become equal, the equation (18) is established, and therefore the relationship as the equation (19) is established.
ωm = ωm + ΔΦ0 / Δt + ΔΦ1 / Δt (18)
ΔΦ0 / Δt = −ΔΦ1 / Δt (19)

  At this time, the angular frequency (ωm + ΔΦ0 / Δt + ΔΦ1 / Δt) of the first microwave signal transmitted through the light partial reflection mirror 4 and photoelectrically converted by the first photoelectric conversion means 5 is expressed by the above equation (19). Since ωm, the phase fluctuation component due to the transmission optical fiber 3 can be canceled out. In the above description, the initial offset of the fixed optical path length (phase) is omitted.

  As described above, according to the sixth embodiment, the configuration is such that the modulated light reciprocating near the transmission destination of the modulated light is monitored and the angular frequency of the modulated light is controlled. It is possible to compensate for phase fluctuation after transmission.

Embodiment 7 FIG.
FIG. 8 is a block diagram showing a configuration of an optical fiber microwave transmission device according to Embodiment 7 of the present invention. The optical fiber microwave transmission device according to the seventh embodiment shown in FIG. 8 includes first and second frequency conversion means 82b from the phase synchronization circuit 8 of the optical fiber microwave transmission device according to the fifth embodiment shown in FIG. 83b and first to third frequency conversion means 82d to 84d are added. Other configurations are the same, and the same reference numerals are given and description thereof is omitted.

  The first frequency converting means 82d converts the angular frequency of the second microwave signal from the second photoelectric converting means 6 to ½ times. The second microwave signal whose angular frequency has been converted by the first frequency converting means 82d is output to the third frequency converting means 84d.

  The second frequency converting means 83d converts the angular frequency of the modulating microwave signal from the first microwave distributor 81b to ½ times. The modulating microwave signal whose angular frequency has been converted by the second frequency converting unit 83d is output to the third frequency converting unit 84d.

  Based on the second microwave signal from the first frequency converting means 82d and the modulating microwave signal from the second frequency converting means 83d, the third frequency converting means 84d has a difference in frequency between them. A first differential microwave signal having a phase difference is generated.

  The phase comparison unit 85 compares the reference microwave signal from the reference signal source 7 with the first differential microwave signal from the third frequency conversion unit 84d, and measures the amount of phase fluctuation (phase difference). Then, a phase difference signal is generated by converting the phase difference into an electric signal.

  Here, as in the first embodiment, the angular frequency of the reference microwave signal from the reference signal source 7 is ωm, and the angular frequency of the modulation microwave signal from the VCO 87 is ωm + ΔΦ0 / Δt.

  The modulated light from the electro-optic conversion means 1 propagates through the transmission optical fiber 3 via the optical circulator 2. Here, assuming that the amount of change in the transmission phase when the optical path length varies due to the environmental variation of the transmission optical fiber 3 is ΔΦ1, the first photoelectric conversion means 5 transmits the first photoelectric conversion means 5 and performs photoelectric conversion. The angular frequency of 1 microwave signal is ωm + ΔΦ0 / Δt + ΔΦ1 / Δt.

  On the other hand, the angular frequency of the modulated light that reciprocates through the transmission optical fiber 3 by being reflected by the optical partial reflection mirror 4 is subjected to the phase fluctuation caused by the transmission optical fiber 2 twice. Therefore, the angular frequency of the second microwave signal photoelectrically converted by the second photoelectric conversion means 6 after reciprocating is ωm + ΔΦ0 / Δt + 2 · ΔΦ1 / Δ.

When, for example, a frequency divider is used as the first frequency conversion unit 82d and the second microwave signal from the second photoelectric conversion unit 6 is converted into an angular frequency that is ½ times, the equation (20) is obtained. A second microwave signal having a high angular frequency is output.
ωm / 2 + ΔΦ0 / Δt / 2 + ΔΦ1 / Δt (20)

Further, when, for example, a frequency divider is used as the second frequency conversion unit 83d and the modulation microwave signal from the first microwave distributor 81b is converted into an angular frequency that is ½ times, Equation (21) is obtained. A modulation microwave signal having an angular frequency as shown is output.
ωm / 2 + ΔΦ0 / Δt / 2 (21)

Further, for example, a mixer or the like is used as the third frequency converting unit 84d, and the difference component between the second microwave signal from the first frequency converting unit 82d and the modulating microwave signal from the second frequency converting unit 83d. Is output, a first differential microwave signal having an angular frequency as shown in Expression (22) is output.
ωm + ΔΦ0 / Δt + ΔΦ1 / Δt (22)

Then, the phase of the first differential microwave signal and the phase of the reference microwave signal from the reference signal source 7 are compared by the phase comparison means 85, and the modulation frequency is controlled by the VCO 87 so as to cancel the difference. Generate a microwave signal.
Therefore, when both input signals to the phase comparison means 85 become equal, the equation (23) is established, and thus the relationship as the equation (24) is established.
ωm = ωm + ΔΦ0 / Δt + ΔΦ1 / Δt (23)
ΔΦ0 / Δt = −ΔΦ1 / Δt (24)

  At this time, the angular frequency (ωm + ΔΦ0 / Δt + ΔΦ1 / Δt) of the first microwave signal transmitted through the light partial reflection mirror 4 and photoelectrically converted by the first photoelectric conversion means 5 is expressed by the above equation (24). Since ωm, the phase fluctuation component due to the transmission optical fiber 3 can be canceled out. In the above description, the initial offset of the fixed optical path length (phase) is omitted.

  As described above, according to the seventh embodiment, the configuration is such that the modulated light reciprocating near the transmission destination of the modulated light is monitored and the angular frequency of the modulated light is controlled. It is possible to compensate for phase fluctuation after transmission.

Embodiment 8 FIG.
FIG. 9 is a block diagram showing a configuration of an optical fiber microwave transmission device according to Embodiment 8 of the present invention. The optical fiber microwave transmission device according to the eighth embodiment shown in FIG. 9 includes first and second frequency conversion means 82b from the phase synchronization circuit 8 of the optical fiber microwave transmission device according to the fifth embodiment shown in FIG. 83b, the fourth to sixth microwave distributors 91, 93, 95, the frequency synthesizer 92, the microwave coupler 94, the first to fourth frequency conversion means 82e to 84e, 90e, and the first and second frequencies. Limiting means 96 and 97 are added. Other configurations are the same, and the same reference numerals are given and description thereof is omitted.

  The first microwave distributor 81 b outputs one of the branched modulation microwave signals to the fourth microwave distributor 91, and outputs the other modulation microwave signal to the frequency synthesizer 92.

  The fourth microwave distributor 91 branches the modulating microwave signal from the first microwave distributor 81b into two. One modulation microwave signal branched by the fourth microwave distributor 91 is output to the microwave coupler 94, and the other modulation microwave signal is output to the third frequency converter 84e.

  The frequency synthesizer 92 generates a second modulation microwave signal by multiplying the angular frequency of the modulation microwave signal from the first microwave distributor 81b by an arbitrary real number (N times). The second modulation microwave signal generated by the frequency synthesizer 92 is output to the fifth microwave distributor 93.

  The fifth microwave distributor 93 branches the second modulation microwave signal from the frequency synthesizer 92 into two. One second modulation microwave signal branched by the fifth microwave distributor 93 is output to the microwave coupler 94, and the other second modulation microwave signal is the third frequency conversion means. 84e.

  The microwave coupler 94 combines the modulation microwave signal from the fourth microwave distributor 91 and the second modulation microwave signal from the fifth microwave distributor 93 to obtain a final result. A microwave signal for modulation is generated. The modulation microwave signal generated by the microwave coupler 94 is output to the electro-optic conversion means 1.

  The third frequency converting means 84e is configured based on the modulation microwave signal from the fourth microwave distributor 91 and the second modulation microwave signal from the fifth microwave distributor 93. A second differential microwave signal having a frequency difference and a phase difference is generated. The second differential microwave signal generated by the third frequency conversion unit 84e is output to the first frequency conversion unit 82e.

  The sixth microwave distributor 95 branches the second microwave signal from the second photoelectric conversion means 6 into two. One second microwave signal branched by the sixth microwave distributor 95 is output to the first frequency limiting means 96, and the other second microwave signal is output to the second frequency limiting means 97. Is output.

  The first frequency limiting means 96 extracts a third microwave signal whose angular frequency matches the modulation microwave signal included in the second microwave signal from the sixth microwave distributor 95. is there. The third microwave signal extracted by the first frequency limiting means 96 is output to the fourth frequency converting means 90e.

  The second frequency limiting means 97 extracts a fourth microwave signal whose angular frequency matches that of the second modulation microwave signal included in the second microwave signal from the sixth microwave distributor 95. To do. The fourth microwave signal extracted by the second frequency limiting means 97 is output to the fourth frequency converting means 90e.

  The fourth frequency converting means 90e is based on the difference between the frequencies of the third microwave signal from the first frequency limiting means 96 and the fourth microwave signal from the second frequency limiting means 97. And a third differential microwave signal having a phase difference. The third differential microwave signal generated by the fourth frequency converting unit 90e is output to the first frequency converting unit 82e.

  The first frequency converting unit 82e is configured based on the second differential microwave signal from the third frequency converting unit 84e and the third differential microwave signal from the fourth frequency converting unit 90e. The first differential microwave signal having the difference and the phase difference is generated. The first differential microwave signal generated by the first frequency conversion unit 82e is output to the second frequency conversion unit 83e.

  The second frequency conversion unit 83e multiplies the angular frequency of the first differential microwave signal from the first frequency conversion unit 82e by ½ (N−1). The first differential microwave signal whose angular frequency and phase have been converted by the second frequency converting unit 83e is output to the phase comparing unit 85.

  The phase comparison unit 85 compares the reference microwave signal from the reference signal source 7 with the first differential microwave signal from the second frequency conversion unit 83e to measure the phase fluctuation amount (phase difference). Then, a phase difference signal is generated by converting the phase difference into an electric signal.

  Here, as in the first embodiment, the angular frequency of the reference microwave signal from the reference signal source 7 is ωm, and the angular frequency of the modulating microwave signal from the VCO 87 is ωm + ΔΦ0 / Δt.

  In this case, the angular frequency of the second modulation microwave signal from the frequency synthesizer 92 is N times the angular frequency of the modulation microwave signal, and becomes Nωm + NΔΦ0 / Δt.

  The modulated light from the electro-optic conversion means 1 propagates through the transmission optical fiber 3 via the optical circulator 2. Here, if the transmission phase fluctuation amount when the optical path length fluctuates due to the environmental fluctuation of the transmission optical fiber 3 is ΔΦ1, the modulation that has been transmitted through the optical partial reflection mirror 4 and photoelectrically converted by the first photoelectric conversion means 5 The angular frequency of the microwave signal for use is ωm + ΔΦ0 / Δt + ΔΦ1 / Δt. The angular frequency of the second modulation microwave signal is N times the angular frequency of the modulation microwave signal, and becomes Nωm + NΔΦ0 / Δt + NΔΦ1 / Δt.

  On the other hand, the angular frequency of the modulated light that reciprocates through the transmission optical fiber 3 by being reflected by the optical partial reflection mirror 4 is subjected to the phase fluctuation caused by the transmission optical fiber 2 twice. Therefore, after the reciprocation, the angular frequency of the modulated microwave signal included in the first microwave signal photoelectrically converted by the second photoelectric conversion means 6 is ωm + ΔΦ0 / Δt + 2 · ΔΦ1 / Δ. The angular frequency of the second modulation microwave signal included in the first microwave signal is Nωm + NΔΦ0 / Δt + 2N · ΔΦ1 / Δ.

  Here, when reflection occurs between the optical circulator 2 and the transmission optical fiber 3 or between the transmission optical fiber 3 and the optical partial reflection mirror 4, an interference microwave signal is generated in the second photoelectric conversion means 6. Since the interference microwave signal from the second photoelectric conversion means 6 is added to the photoelectrically converted first microwave signal, phase fluctuation occurs. Here, when the phase variation of the modulation microwave signal caused by the interference microwave signal is ΔΦ2, and the phase variation of the second modulation microwave signal caused by the interference microwave signal is ΔΦ3, the modulation microwave signal The angular frequency is ωm + ΔΦ0 / Δt + 2 · ΔΦ1 / Δt + ΔΦ2 / Δt. The angular frequency of the second modulation microwave signal included in the microwave signal is Nωm + NΔΦ0 / Δt + 2N · ΔΦ1 / Δt + ΔΦ3 / Δt.

  The first microwave signal is distributed by the sixth microwave distributor 95, the modulation microwave signal is separated by the first frequency limiting means 96, and the second modulation is performed by the second frequency limiting means 97. The microwave signal for use is separated.

For example, a mixer or the like is used as the fourth frequency converting unit 90e, and the difference component between the modulating microwave signal from the first frequency limiting unit 96 and the second modulating microwave signal from the second frequency limiting unit 97 is used. Is output, a third differential microwave signal having an angular frequency as shown in Expression (25) is output.
(N−1) ωm + (N−1) ΔΦ0 / Δt + 2 (N−1) ΔΦ1 / Δt + (ΔΦ3 / Δt−ΔΦ2 / Δt) (25)

Further, for example, a mixer or the like is used as the first frequency conversion unit 82e, and the second differential microwave signal from the third frequency conversion unit 84e and the third differential microwave signal from the fourth frequency conversion unit 90e Is output, a first differential microwave signal having an angular frequency as shown in Expression (26) is output.
2 (N−1) ωm + 2 (N−1) ΔΦ0 / Δt + 2 (N−1) ΔΦ1 / Δt + (ΔΦ3 / Δt−ΔΦ2 / Δt) (26)

Further, when a frequency divider or the like is used as the second frequency conversion unit 83e, for example, the first differential microwave signal from the first frequency conversion unit 82e is converted into an angular frequency of 1/2 (N-1) times. A comparative microwave signal having an angular frequency as shown in Expression (27) is output.
ωm + ΔΦ0 / Δt + ΔΦ1 / Δt + (ΔΦ3 / Δt−ΔΦ2 / Δt) / 2 (N−1) (27)

  Then, the phase of the first differential microwave signal and the phase of the reference microwave signal from the reference signal source 7 are compared by the phase comparison means 85, and the modulation frequency is controlled by the VCO 87 so as to cancel the difference. Generate a microwave signal.

Therefore, when both input signals to the phase comparison means 85 become equal, the equation (28) is established, and thus the relationship as the equation (29) is established.
ωm = ωm + ΔΦ0 / Δt + ΔΦ1 / Δt + (ΔΦ3 / Δt−ΔΦ2 / Δt) / 2 (N−1) (28)
ΔΦ0 / Δt = −ΔΦ1 / Δt− (ΔΦ3 / Δt−ΔΦ2 / Δt) / 2 (N−1) (29)

  At this time, the angular frequency (ωm + ΔΦ0 / Δt + ΔΦ1 / Δt) of the first microwave signal transmitted through the light partial reflection mirror 4 and photoelectrically converted by the first photoelectric conversion means 5 is expressed by the above equation (29). Since ωm− (ΔΦ3 / Δt−ΔΦ2 / Δt) / 2 (N−1), the phase variation component due to the transmission optical fiber 3 can be canceled out, but the phase variation due to reflection that occurs in the optical transmission path remains. However, by making the multiple N of the angular frequency of the frequency synthesizer 92 greater than 1, it is possible to expect an effect of reducing the phase fluctuation due to reflection occurring in the optical transmission line.

  As described above, according to the eighth embodiment, the frequency synthesizer 92 is configured so that the angular frequency and phase of the modulating microwave signal are multiplied by an arbitrary real number. Can be reduced.

  In the fifth to eighth embodiments, another configuration of the phase synchronization circuit 8 has been described based on the configuration of the optical fiber microwave transmission device shown in FIG. However, the present invention is not limited to this, and is similarly applicable to the optical fiber microwave transmission device shown in FIGS. The same applies.

  Further, within the scope of the present invention, the invention of the present application can be freely combined with each embodiment, modified with any component in each embodiment, or omitted with any component in each embodiment. .

  Reference Signs List 1 electro-optic conversion means, 2 optical circulator (optical path switching means), 3 transmission optical fiber, 4 optical partial reflection mirror (optical partial reflection means), 5, 6 first and second photoelectric conversion means, 7 reference signal source, 8 phase Synchronous circuit (phase synchronizing means), 9 microwave signal source, 10 3rd microwave distributor, 11, 12 5th and 6th frequency converting means, 13 PBS (optical path switching means), 14 optical multiplexer / demultiplexer (optical coupling) Demultiplexing means), 15 Faraday rotating mirror (polarization rotating means), 81, 81b First microwave distributor (microwave distributing means), 82-84, 82b, 83b, 82c-84c, 82d-84d, 82e ˜84e First to third frequency conversion means, 85 phase comparison means, 86 loop filter, 87 VCO (modulation microwave generation means), 88 second microwave distributor, 89 microwave Signal source, 90, 90e fourth frequency converting means, 91 fourth microwave distributor, 92 frequency synthesizer, 93 fifth microwave distributor, 94 microwave coupler, 95 sixth microwave distributor, 96, 97 First and second frequency limiting means.

Claims (10)

Electro-optic conversion means for outputting modulated light intensity-modulated by the input modulation microwave signal;
An optical path switching means that is arranged at a subsequent stage of the electro-optic conversion means, and selectively switches the optical path of the modulated light;
A part of the modulated light output from the electro-optic conversion means via the optical path switching means and the transmission optical fiber is reflected on the transmission optical fiber, and a light partial reflection means for transmitting the rest;
First photoelectric conversion means for converting the modulated light transmitted through the light partial reflection means into a first microwave signal;
Second photoelectric conversion means for converting the modulated light output from the partial light reflection means via the transmission optical fiber and the optical path switching means into a second microwave signal;
Phase synchronization means for generating the modulation microwave signal based on the phase of the second microwave signal converted by the second photoelectric conversion means and the phase of the reference microwave signal;
The phase synchronization means includes
First frequency conversion means for generating a first differential microwave signal that is a difference component between the second microwave signal converted by the second photoelectric conversion means and the modulation microwave signal;
Second frequency conversion means for converting the angular frequency of the first differential microwave signal generated by the first frequency conversion means;
Phase comparison means for generating a phase difference signal based on the phase of the reference microwave signal and the phase of the first differential microwave signal converted by the second frequency conversion means;
An optical fiber microwave transmission device comprising: a modulation microwave generation unit that generates the modulation microwave signal whose angular frequency is controlled based on the phase difference signal generated by the phase comparison unit. Electro-optic conversion means for outputting modulated light intensity-modulated by the input modulation microwave signal;
An optical path switching means that is arranged at a subsequent stage of the electro-optic conversion means, and selectively switches the optical path of the modulated light;
A part of the modulated light output from the electro-optic conversion means via the optical path switching means and the transmission optical fiber is reflected on the transmission optical fiber, and a light partial reflection means for transmitting the rest;
First photoelectric conversion means for converting the modulated light transmitted through the light partial reflection means into a first microwave signal;
Second photoelectric conversion means for converting the modulated light output from the partial light reflection means via the transmission optical fiber and the optical path switching means into a second microwave signal;
Phase synchronization means for generating the modulation microwave signal based on the phase of the second microwave signal converted by the second photoelectric conversion means and the phase of the reference microwave signal;
The phase synchronization means includes
First frequency conversion means for generating a first differential microwave signal that is a difference component between the second microwave signal converted by the second photoelectric conversion means and a predetermined microwave signal;
Second frequency conversion means for generating a second differential microwave signal that is a difference component between the first differential microwave signal generated by the first frequency conversion means and the modulation microwave signal;
Third frequency conversion means for generating a third differential microwave signal that is a difference component between the second differential microwave signal generated by the second frequency conversion means and the microwave signal;
Fourth frequency conversion means for converting the angular frequency of the third differential microwave signal generated by the third frequency conversion means;
Phase comparison means for generating a phase difference signal based on the phase of the reference microwave signal and the phase of the third differential microwave signal converted by the fourth frequency conversion means;
An optical fiber microwave transmission device comprising: a modulation microwave generation unit that generates the modulation microwave signal whose angular frequency is controlled based on the phase difference signal generated by the phase comparison unit. Electro-optic conversion means for outputting modulated light intensity-modulated by the input modulation microwave signal;
An optical path switching means that is arranged at a subsequent stage of the electro-optic conversion means, and selectively switches the optical path of the modulated light;
A part of the modulated light output from the electro-optic conversion means via the optical path switching means and the transmission optical fiber is reflected on the transmission optical fiber, and a light partial reflection means for transmitting the rest;
First photoelectric conversion means for converting the modulated light transmitted through the light partial reflection means into a first microwave signal;
Second photoelectric conversion means for converting the modulated light output from the partial light reflection means via the transmission optical fiber and the optical path switching means into a second microwave signal;
Phase synchronization means for generating the modulation microwave signal based on the phase of the second microwave signal converted by the second photoelectric conversion means and the phase of the reference microwave signal;
The phase synchronization means includes
First frequency conversion means for converting the angular frequency of the second microwave signal converted by the second photoelectric conversion means;
Second frequency converting means for converting the angular frequency of the modulating microwave signal;
Generating a first differential microwave signal that is a difference component between the second microwave signal converted by the first frequency conversion means and the modulation microwave signal converted by the second frequency conversion means Third frequency converting means for
Phase comparison means for generating a phase difference signal based on the phase of the reference microwave signal and the phase of the first differential microwave signal generated by the third frequency conversion means;
An optical fiber microwave transmission device comprising: a modulation microwave generation unit that generates the modulation microwave signal whose angular frequency is controlled based on the phase difference signal generated by the phase comparison unit. Electro-optic conversion means for outputting modulated light intensity-modulated by the input modulation microwave signal;
An optical path switching means that is arranged at a subsequent stage of the electro-optic conversion means, and selectively switches the optical path of the modulated light;
A part of the modulated light output from the electro-optic conversion means via the optical path switching means and the transmission optical fiber is reflected on the transmission optical fiber, and a light partial reflection means for transmitting the rest;
First photoelectric conversion means for converting the modulated light transmitted through the light partial reflection means into a first microwave signal;
Second photoelectric conversion means for converting the modulated light output from the partial light reflection means via the transmission optical fiber and the optical path switching means into a second microwave signal;
Phase synchronization means for generating the modulation microwave signal based on the phase of the second microwave signal converted by the second photoelectric conversion means and the phase of the reference microwave signal;
The phase synchronization means includes
Microwave distribution means for bifurcating the reference microwave signal;
First frequency conversion means for converting the angular frequency of one reference microwave signal branched by the microwave distribution means;
A first differential microwave signal that is a difference component between the second microwave signal converted by the second photoelectric conversion means and the reference microwave signal converted by the first frequency conversion means is generated. Second frequency conversion means;
Third frequency conversion means for generating a second differential microwave signal that is a difference component between the first differential microwave signal generated by the second frequency conversion means and the modulation microwave signal;
A phase difference signal is generated based on the phase of the other reference microwave signal branched by the microwave distributing means and the phase of the second differential microwave signal generated by the third frequency converting means. Phase comparison means;
An optical fiber microwave transmission device comprising: a modulation microwave generation unit that generates the modulation microwave signal whose angular frequency is controlled based on the phase difference signal generated by the phase comparison unit. A frequency synthesizer for generating a second modulation microwave signal by multiplying the angular frequency of the modulation microwave signal generated by the modulation microwave generation unit N times (N is a real number);
The final modulation microwave signal is generated by synthesizing the modulation microwave signal generated by the modulation microwave generation unit and the second modulation microwave signal generated by the frequency synthesizer. A microwave coupler,
A second differential microwave signal that is a difference component between the modulation microwave signal generated by the modulation microwave generation means and the second modulation microwave signal generated by the frequency synthesizer is generated. 3 frequency conversion means;
First frequency limiting means for extracting a modulation microwave signal from the second microwave signal converted by the second photoelectric conversion means;
Second frequency limiting means for extracting a second modulation microwave signal from the second microwave signal converted by the second photoelectric conversion means;
A third differential microwave signal, which is a difference component between the modulation microwave signal extracted by the first frequency limiting means and the second modulation microwave signal extracted by the second frequency limiting means, A fourth frequency converting means for outputting,
The first frequency conversion means replaces the generation of the first difference microwave signal with the second difference microwave signal generated by the third frequency conversion means and the fourth frequency conversion. Generating a first differential microwave signal that is a difference component from the third differential microwave signal generated by the means;
2. The second frequency conversion unit multiplies the angular frequency of the first differential microwave signal generated by the first frequency conversion unit by ½ (N−1). Optical fiber microwave transmission device. A microwave signal source for generating a third microwave signal of a predetermined angular frequency;
A fourth differential microwave signal, which is a difference component between the modulation microwave signal generated by the modulation microwave generation means and the third microwave signal generated by the microwave signal source, is generated. 5 frequency conversion means;
A fifth differential microwave signal that is a difference component between the second microwave signal converted by the second photoelectric conversion means and the third microwave signal generated by the microwave signal source is generated. Sixth frequency conversion means,
The electro-optic conversion means uses the fourth differential microwave signal instead of the modulating microwave signal,
The optical fiber micro of any one of claims 1 to 5, wherein the phase synchronization means uses the fifth differential microwave signal instead of the second microwave signal. Wave transmission equipment. The optical fiber microwave transmission device according to any one of claims 1 to 6 , wherein the optical path switching means is an optical circulator. The light partial reflection means is
Polarization rotation means for rotating and reflecting the polarization direction of the input modulated light by 90 degrees;
The modulated light transmitted by the transmission optical fiber is branched and output to the first photoelectric conversion means and the polarization rotation means, respectively, and the modulated light reflected by the polarization rotation means is output to the transmission optical fiber. Optical multiplexing / demultiplexing means
The optical fiber microwave transmission device according to any one of claims 1 to 7 , wherein the optical path switching means is a polarization beam splitter. The optical fiber microwave transmission device according to claim 4, wherein the first frequency converting means converts the angular frequency of one reference microwave signal branched by the microwave distributing means to three times. A composite comprising: a plurality of the optical fiber microwave transmission devices according to any one of claims 1 to 9 , wherein a reference microwave signal is shared between the respective optical fiber microwave transmission devices. Type optical fiber microwave transmission device.

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