A Phase Adaptive Stabilization System Based on Ultra-High Stability Multi-Channel Optical Fiber Transmission Technology

Abstract

The present invention discloses a phase adaptive stabilization system (PASS) based on an ultra-high stability multi-channel optical fiber transmission technology, which includes a transmitting source system, a receiving system, a reference system, and a phase measurement system; the transmitting source system includes a signal source, an ultra-high stability multi-channel optical fiber transmission system, and a transmitting antenna; the receiving system includes a receiving antenna, an amplifier, a mixer, an attenuator, etc.; the reference system includes a signal source, a frequency multiplier, a mixer, etc.; the phase measurement system includes a band-pass filter, an analog-to-digital converter, a digital correlator, a computer, etc. The ultra-high stability multi-channel optical fiber transmission system adopted by the present invention has the advantages of low loss, high stability, and anti-electromagnetic interference when transmitting optical signals over a long distance for a long time; through the remote reflection signal, the change in the signal phase caused by the disturbance of the transmission optical fiber can be detected in real time, and then the real-time phase compensation is carried out by feedback controlling the variable optical delay line, thereby realizing the ultra-high stability of the transmission signal phase.

Description

Technical Field

[0001] The present invention belongs to the field of submillimeter astronomical telescopes, and particularly relates to a phase adaptive stabilization system based on ultra-high stability multi-channel optical fiber transmission technology. Background Art

[0002] Currently, the apertures of large optical telescopes under construction or to be built in the world (such as E-ELT and TMT) have far exceeded the apertures of some currently operating submillimeter telescopes (such as JCMT, etc.), and even exceeded the aperture of the next-generation submillimeter telescope CCAT. The development of large-aperture high-precision submillimeter telescopes in the world has been slow for decades. An important reason is that the antennas of large-aperture high-precision submillimeter telescopes have been unable to break through due to technical problems for a long time. Submillimeter phase adaptive stabilization technology is considered an effective way to break through this problem.

[0003] At present, a practical submillimeter phase adaptive stabilization system has not been realized internationally, which is "zero". In view of this, the present invention proposes a phase adaptive stabilization system based on ultra-high stability multi-channel optical fiber transmission technology. Among them, one of the difficulties of point-frequency PASS is the transmission of point-frequency millimeter wave signals to each transmitter on the reflector. The traditional coaxial cable transmission has a very large attenuation for millimeter wave / submillimeter wave signals, and it is difficult to maintain high-precision phase, which cannot meet the requirements. Ultra-high stability multi-channel optical fiber transmission technology is an important means to solve this difficulty and break through the limitation of PASS application by the telescope aperture, and it is a key step for the practical application of PASS. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a phase adaptive stabilization system based on ultra-high stability multi-channel optical fiber transmission technology, and the technical solution adopted is as follows:

[0005] A phase adaptive stabilization system based on ultra-high stability multi-channel optical fiber transmission technology includes a transmitter system, a receiver system, a reference system, and a phase measurement system;

[0006] The transmitter system includes a signal source, an ultra-high stability multi-channel optical fiber transmission system, a transmitting antenna, etc. The millimeter wave generated by the signal source is divided into two paths of signals through a directional coupler after frequency doubling. One path of signal directly enters the reference system as a reference signal, and the other path of signal is first transmitted to the ultra-high stability multi-channel optical fiber transmission system for laser modulation, and then is divided into multiple paths of signals by an optical power distributor and an optical switch and sent to the far end through the transmitting antenna respectively. The photodetector at the far end demodulates the signal carried on the laser;

[0007] The receiver system includes a receiving antenna, an amplifier, a mixer, an attenuator, etc. The receiving antenna sequentially receives the signals transmitted by the transmitting antennas at each measurement point, and after power amplification, mixes with the local oscillator signal from the reference system to obtain an intermediate frequency signal;

[0008] The reference system includes a signal source, a frequency multiplier, a mixer, etc. The millimeter wave generated by the signal source is divided into two paths through a power divider after frequency multiplication. One path of the signal is mixed with the reference signal from the transmitting source system to form an intermediate frequency signal, and the other path is used as the local oscillator signal and transmitted to the receiving system;

[0009] The phase measurement system includes a band-pass filter, an analog-to-digital converter, a digital correlator, a computer, etc. The two intermediate frequency signals generated by the receiving system and the reference system are input into the digital correlator for correlation operation after passing through the analog-to-digital converter to measure the phase difference between the two; According to the time sequence of the signals transmitted by the transmitting antennas at each measurement point, the phase changes of the continuous wave of the path lengths from each measurement point on the main mirror reflecting surface to the receiving antenna are measured in sequence, so as to calculate and restore the wavefront on the main mirror reflecting surface from point to surface.

[0010] Further, in the transmitting source system, the laser-modulated signal is divided into multiple paths and sent to the remote end respectively. Each path has a delay stability control unit for real-time detecting the delay change of the link and controlling the variable optical delay line to compensate for the delay change of the link.

[0011] Further, the signal source of the transmitting source system generates a millimeter wave of 12 GHz and becomes a millimeter wave of 24 GHz after doubling the frequency; the signal source of the reference system generates a millimeter wave of 12.015 GHz and becomes a millimeter wave of 24.03 GHz after doubling the frequency; the intermediate frequency signals generated by mixing in the receiving system and the reference system are both 30 MHz.

[0012] Further, evaluating the stability of the signal amplitude and phase of each channel in the ultra-high stability multi-channel optical fiber transmission system includes the following steps:

[0013] S1. Control the optical switch in the ultra-high stability multi-channel optical fiber transmission system, open one of the channels, measure and record the phase data of the signal of this channel within a preset time through a vector network analyzer, and calculate the RMS error and Allan deviation of the signal of this channel according to the phase data;

[0014] S2. Control the optical switch in the ultra-high stability multi-channel optical fiber transmission system, open all channels, compare the transmitted signals of each channel within a preset time, and obtain the amplitude-normalized Allan variance and Allan deviation of the phase of each channel.

[0015] The beneficial effects of the present invention are:

[0016] The ultra-high stability multi-channel optical fiber transmission system adopted by the present invention has the advantages of low loss, high stability, and anti-electromagnetic interference when transmitting optical signals over long distances and for long periods of time; by means of the remote reflection signal, the change in the signal phase caused by the disturbance of the transmission optical fiber (such as environmental temperature, vibration, and cable movement, etc.) can be detected in real time, and then the real-time phase compensation is carried out by feedback controlling the variable optical delay line, thereby realizing the high stability of the transmission signal phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural framework diagram of the system of the present invention;

[0018] Figure 2 It is a schematic diagram of the emission source system in the present invention;

[0019] Figure 3 It is a schematic diagram of the receiving system in the present invention;

[0020] Figure 4 It is a schematic diagram of the reference system in the present invention;

[0021] Figure 5 It is a schematic diagram of the phase measurement system in the present invention;

[0022] Figure 6 It is the Allan deviation diagram of the single-channel transmission signal of the ultra-high stability multi-channel optical fiber transmission system in the embodiment;

[0023] Figure 7 It is the signal stability diagram of the 6-channel transmission signals of the ultra-high stability multi-channel optical fiber transmission system in the embodiment, where:

[0024] (a) is the amplitude stability diagram,

[0025] (b) is the phase stability diagram;

[0026] Figure 8 It is the phase-time change step diagram of the high-precision electric control displacement platform moving 20um in a single step;

[0027] Figure 9 It is the phase-time change step diagram of the high-precision electric control displacement platform with different single-step displacements, where:

[0028] (a) is the phase-time change step diagram of a single-step displacement of 30um,

[0029] (b) is the phase-time change step diagram of a single-step displacement of 40um,

[0030] (c) is the phase-time change step diagram of a single-step displacement of 50um;

[0031] Figure 10It is a relationship diagram between the displacement of a high-precision electronically controlled displacement platform and the phase change measured by a phase measurement system;

[0032] Figure 11 It is a PASS model diagram during the field test;

[0033] Figure 12 It is a diagram of the displacement step experiment results of each transmitting antenna under the field stability evaluation test, where:

[0034] (a) shows the displacement step experiment results of the No. 1 transmitting antenna,

[0035] (b) shows the displacement step experiment results of the No. 2 transmitting antenna,

[0036] (c) shows the displacement step experiment results of the No. 3 transmitting antenna,

[0037] (d) shows the displacement step experiment results of the No. 4 transmitting antenna,

[0038] (e) shows the displacement step experiment results of the No. 5 transmitting antenna,

[0039] (f) shows the displacement step experiment results of the No. 6 transmitting antenna. Detailed implementation manners

[0040] Now, the present invention will be further described in detail with reference to the accompanying drawings.

[0041] As Figure 1 shown, a phase adaptive stabilization system based on an ultra-high stability multi-channel optical fiber transmission technology proposed by the present invention mainly includes a transmitting source system, a receiving system, a reference system, and a phase measurement system.

[0042] As Figure 2 , the transmitting source system includes a signal source, an ultra-high stability multi-channel optical fiber transmission system, a transmitting antenna, etc. The signal source generates a 12 GHz millimeter wave, which is doubled to become a 24 GHz millimeter wave, and then two signals are separated through a directional coupler. One of them directly enters the reference system as a reference signal; through an electro-optical modulator, the other is transmitted to the ultra-high stability multi-channel optical fiber transmission system, which modulates the 24 GHz signal to be transmitted onto the laser; then, using an optical power distributor and an optical switch, the signal to be transmitted is divided into multiple channels and sent to the remote end; each channel has a delay stability control unit that real-time detects the delay change of the link and controls the variable optical delay line to compensate for the delay change of the link; the photodetector at the remote end demodulates the signal carried on the laser into a 24 GHz millimeter wave.

[0043] As Figure 3 and 4As shown in the figure, the receiving system includes a receiving antenna, an amplifier, a mixer, an attenuator, etc. According to the time sequence of the transmission of the transmitting antennas at each measurement point, the receiver "observes" (receives) the signals of N transmitting antennas in chronological order; the receiving antenna receives the 24 GHz microwave signal from free space, and after power amplification, it is mixed with the local oscillator signal transmitted from the reference system into an intermediate frequency. The reference system includes a signal source, a frequency multiplier, a mixer, etc. The signal source generates a millimeter wave of 12.015 G, which is doubled to a millimeter wave of 24.03 GHz. After passing through a power divider, it is divided into two paths. One path is mixed with the 24 GHz signal carried by the reference path transmitted from the transmitting source system to become an intermediate frequency signal of 30 MHz, and the other path is mixed with the 24 GHz signal of the signal path of the receiving system to become an intermediate frequency signal of 30 MHz.

[0044] As Figure 5 shown in the figure, the phase measurement system includes a band-pass filter, an analog-to-digital converter, a digital correlator, a computer, etc.; the two intermediate frequency signals are converted into digital signals and then input into the digital correlator for correlation operation to measure the phase difference between the two. According to the time sequence of the transmission of the transmitting antennas at each measurement point, it is easy to obtain the phase change of the continuous wave of the path length from each measurement point on the corresponding main reflector to the receiver, so as to calculate and restore the wavefront on the main mirror reflector from point to surface.

[0045] Measure and verify the stability of the phase of the signal transmitted over a long distance and for a long time by the ultra-high stability multi-channel optical fiber transmission system through experiments. The specific experimental steps are as follows:

[0046] Step 1: Control the optical switch in the ultra-high stability multi-channel optical fiber transmission system to only open Channel 1. Then, through a vector network analyzer, measure and record the phase data of the signal in this channel within 4 hours. Finally, calculate its RMS error and Allan deviation based on the data. The results are as Figure 6 ;

[0047] Step 2: Control the optical switch in the ultra-high stability multi-channel optical fiber transmission system to open all 6 channels. The measurement time and method are the same as in Step 1. Compare these 6 channels to obtain the amplitude-normalized Allan variance of the transmitted signals in each channel of the system and the Allan deviation of the phase, as Figure 7 .

[0048] Combined with specific experiments, use the phase adaptive stabilization system based on the ultra-high stability multi-channel optical fiber transmission technology to conduct experiments to evaluate the linearity and accuracy of real-time displacement measurement under different working environments, including the following steps:

[0049] Step 1: Under laboratory conditions, fix a high-precision electronically controlled displacement platform on an optical bench. Then, vertically place a microstrip transmitting antenna on this platform, and fix the receiving antenna completely at a distance of 1.85 m in the displaceable direction.

[0050] Step 2: Precisely control the transmitting antenna to move in the same direction 3 times through a high-precision electronically controlled displacement platform, with a relative movement of 20 μm each time. Record the data of PASS phase measurement, and a phase change step diagram can be obtained, as shown in Figure 8 , and the experimental results show that the point-frequency PASS achieves a real-time displacement measurement accuracy better than 20 μm under laboratory conditions;

[0051] Step 3: Similar to Step 2, except that the relative movement each time is changed to 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, and 100 μm respectively. Under each displacement condition, record the data of PASS phase measurement again to obtain their respective phase change step diagrams, as shown in Figure 9 ; Further fitting the above data, the linear relationship between the displacement generated by the high-precision electronically controlled displacement platform and the phase change measured by the phase measurement system can be obtained, as shown in Figure 10 ;

[0052] Step 4: Figure 11 This is the PASS model diagram for the field test. The experimental platform is part of the main mirror and sub-mirror of the Delingha 13.7 m millimeter-wave radio telescope. Fix 6 microstrip transmitting antennas at the preset positions on the main mirror surface, and then fix 1 microstrip receiving antenna at the focal plane of the sub-mirror;

[0053] Step 5: Use actuators to adjust the position of the main mirror panel to simulate the deformation of the main mirror. By adjusting the 6 displacement actuators under the main mirror surface, make each transmitting antenna generate a 20 μm displacement 3 times, detect the real-time measurement ability of PASS, and record the phase measurement data of each channel of PASS in sequence to obtain the real-time measurement change step diagram of the displacement (phase difference) under the deformation of 6 different positions on the main mirror surface, as shown in Figure 12 , and the experimental results show that the point-frequency PASS achieves a real-time displacement measurement accuracy better than 20 μm under field conditions.

[0054] The above is only the preferred implementation mode of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should be regarded as within the protection scope of the present invention.

Claims

1. A phase adaptive stabilization system based on ultra-high stable multi-channel optical fiber transmission technology, characterized in that, it includes a transmitting source system, a receiving system, a reference system and a phase measurement system; The transmitting source system includes a signal source, an ultra-high stable multi-channel optical fiber transmission system and a transmitting antenna. The millimeter wave generated by the signal source is divided into two paths of signals through a directional coupler after frequency doubling. One path of signal directly enters the reference system as a reference signal, and the other path of signal is first transmitted to the ultra-high stable multi-channel optical fiber transmission system for laser modulation, and then is divided into multiple paths of signals by an optical power splitter and an optical switch and sent to the far end through the transmitting antenna respectively. The photodetector at the far end demodulates the signal carried on the laser; in the transmitting source system, the laser-modulated signal is divided into multiple paths and sent to the far end respectively, and each path has a delay stability control unit for real-time detecting the delay change of the link and controlling the variable optical delay line to compensate for the delay change of the link; the signal source of the transmitting source system generates a 12 GHz millimeter wave, and after 2 times of frequency doubling, it becomes a 24 GHz millimeter wave; the signal source of the reference system generates a 12.015 GHz millimeter wave, and after 2 times of frequency doubling, it becomes a 24.03 GHz millimeter wave; the intermediate frequency signals generated by mixing in the receiving system and the reference system are both 30 MHz; The receiving system includes a receiving antenna, an amplifier, a mixer and an attenuator. The receiving antenna sequentially receives the signals transmitted by the transmitting antennas at each measurement point in time sequence, and after power amplification, it is mixed with the local oscillator signal from the reference system to obtain an intermediate frequency signal; The reference system includes a signal source, a frequency doubler and a mixer. The millimeter wave generated by the signal source is divided into two paths of signals through a power splitter after frequency doubling. One path of signal is mixed with the reference signal from the transmitting source system to obtain an intermediate frequency signal, and the other path is transmitted to the receiving system as a local oscillator signal; The phase measurement system includes a band-pass filter, an analog-to-digital converter, a digital correlator and a computer. The two intermediate frequency signals generated by the receiving system and the reference system are input into the digital correlator for correlation operation after passing through the analog-to-digital converter to measure the phase difference between the two; according to the time sequence of the signals transmitted by the transmitting antennas at each measurement point, the phase change of the continuous wave of the path length from each measurement point on the main mirror reflecting surface to the receiving antenna is measured in sequence, so as to calculate and restore the wavefront on the main mirror reflecting surface from point to surface.

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