CN204615139U - Photoelectric oscillator - Google Patents

Abstract

The utility model discloses a kind of optical-electronic oscillator, comprise the laser for exporting light carrier, laser connects photoelectricity circulation circuit for forming photoelectricity hybrid resonant chamber, and optical-electronic oscillator also comprises the stability contorting module fluctuated with the time delay compensating photoelectricity circulation circuit to photoelectricity circulation circuit with the injection phase-locking module and controlling for pilot tone realizing Side mode suppressing for injection locking signal.The utility model is by arranging injection phase-locking module, injection locking signal realizes Side mode suppressing to photoelectricity circulation circuit, by arranging stability contorting module, fluctuate with the time delay of extracting each device of photoelectricity circulation circuit and carry out corresponding time delay oscillation compensation, to reach the object of stable oscillation stationary vibration frequency, thus the stable output of the Low phase noise single mode achieving optical-electronic oscillator, and to carry out at different frequency range because pilot tone controls to vibrate with the circulation of injection locking semaphore lock, avoid mutual interference, efficiently avoid the ghost effect of control circuit noise to oscillator signal.

Description

Photoelectric oscillator

technical field

The utility model relates to the field of oscillators, in particular to a photoelectric oscillator.

Background technique

Opto-electronic Oscillator (OEO) is a new type of oscillator combining microwave and photonic technology. It has received high attention because of its extremely low phase noise in the microwave and millimeter wave bands. Electronic warfare, precision measurement and other fields. Compared with the traditional microwave oscillator, OEO has the following advantages: 1. It has extremely low phase noise, and the phase noise does not increase significantly with the increase of the oscillation frequency. Important candidate; 2. It can provide electrical and optical input methods for information systems, and can be applied to various electronic systems, optical communications, and microwave photonics systems; 3. OEO can not only generate oscillation signals, but also achieve phase-locking, multiplication Frequency and other signal processing functions, as well as some sensing, measurement and other functions, are widely used. To sum up, OEO has some characteristics that cannot be compared with traditional oscillators, and is one of the important candidates for generating extremely low phase noise microwave and millimeter wave oscillators, and has high practical value.

The practical application of OEO is currently facing two major problems: First, to achieve low phase noise in OEO, long fiber coils must be used as delays, and as the length of the fiber increases, the mode interval will shrink (for 10GHz oscillation frequency For OEO, 1km optical fiber corresponds to a mode interval of 200kHz), and narrow-band filters cannot be used in the microwave frequency band; second, the electro-optic modulator, optical fiber coil, and microwave amplifier that make up OEO are all environmentally sensitive devices, and fluctuations in external environmental factors will cause Causes a drift in the oscillation frequency. Therefore, it is urgent to design a solution to achieve low phase noise while overcoming the problems of "multi-mode coexistence" and "environmental sensitivity", so as to ensure the stable output of single-mode low phase noise of the oscillation signal.

Utility model content

The utility model provides a photoelectric oscillator to solve the technical problems that the existing photoelectric oscillator has low phase noise single-mode output, which is difficult to realize and the oscillation frequency shifts due to environmental interference.

The technical scheme that the utility model adopts is as follows:

An optoelectronic oscillator, including a laser for outputting an optical carrier, the laser is connected to form an optoelectronic cycle loop of an optoelectronic hybrid resonator,

The photoelectric oscillator also includes an injection phase-locked module for injecting a locking signal into the photoelectric loop to suppress side modes, and a stability control module for pilot frequency control to compensate for delay fluctuations of the photoelectric loop.

Further, the injection phase-locked module includes a first signal source for generating the injection signal and an adjustable attenuator for adjusting the signal power of the injection signal, and the output terminal of the adjustable attenuator is coupled to the photoelectric loop.

Further, the photoelectric cycle loop includes: an electro-optic modulator, an optical fiber coil, a photodetector, a microwave amplifier, a voltage-controlled phase shifter, and a narrow-band filter connected in sequence, and the output end of the narrow-band filter is connected to the electrical input end of the electro-optic modulator;

The optical carrier sent by the laser is delayed by the optical fiber coil after passing through the electro-optical modulator. The delayed optical signal is restored to an electrical signal by a photodetector. The electrical signal is amplified by a microwave amplifier and then adjusted by a voltage-controlled phase shifter. The voltage-controlled phase shifter performs phase adjustment according to the output signal of the stability control module, and the phase-adjusted electrical signal is filtered by a narrow-band filter and then fed back to the electro-optical modulator to enter the next cycle;

The output terminal of the adjustable attenuator is coupled to the connection channel between the narrowband filter and the electrical input terminal of the electro-optic modulator.

Further, the stability control module includes a second signal source for generating a pilot reference source, a phase shifter, a mixer, a low-pass filter, and a baseband signal processing module,

The signal output by the second signal source is divided into two paths, one path is shifted by the phase shifter and then output to the mixer, and the other path enters the photoelectric circulation loop through the electro-optic modulator, and is output to the mixer through the microwave amplifier;

The output terminal of the mixer is connected to the low-pass filter, and the low-pass filter is connected to the baseband signal processing module. The baseband signal processing module generates a voltage-controlled signal to the voltage input terminal of the voltage-controlled phase shifter to compensate for the delay fluctuation of the photoelectric loop .

Further, the angle at which the phase shifter shifts the phase of the signal output by the second signal source is 90 degrees.

Further, the first signal source adopts a dielectric oscillator, and the second signal source adopts a crystal oscillator source.

The utility model has the following beneficial effects:

The photoelectric oscillator of the utility model combines the injection phase-locking and pilot frequency control technology, through setting the injection phase-locking module, injecting the locking signal to the photoelectric circulation loop to realize side mode suppression, ensuring the single-mode stable output of the photoelectric oscillator, and setting the stable control Module, to extract the delay fluctuation of each device in the photoelectric cycle loop and perform corresponding delay fluctuation compensation to achieve the purpose of stabilizing the oscillation frequency, thereby realizing the low phase noise single-mode stable output of the photoelectric oscillator, and due to the pilot frequency control The cyclic oscillation locked with the injection locking signal is carried out in different frequency bands, avoiding mutual interference, and effectively avoiding the parasitic effect of the control circuit noise on the oscillation signal. Not only that, the use of pilot technology to achieve OEO stability control can also overcome In the traditional phase-locked control, the reference source restricts the phase noise near the carrier frequency of the oscillation signal, which ensures the realization of low phase noise performance in the whole frequency band of OEO.

In addition to the purposes, features and advantages described above, the present invention has other purposes, features and advantages. Below with reference to figure, the utility model is described in further detail.

Description of drawings

The accompanying drawings constituting a part of this application are used to provide a further understanding of the utility model, and the schematic embodiments of the utility model and their descriptions are used to explain the utility model, and do not constitute an improper limitation of the utility model. In the attached picture:

Fig. 1 is the structural representation of the optoelectronic oscillator of preferred embodiment of the present utility model;

Fig. 2 is the schematic structural view of the photoelectric circulation loop of the preferred embodiment of the utility model;

Fig. 3 is a schematic structural view of the injection phase-locked module of the preferred embodiment of the utility model;

Fig. 4 is a schematic structural view of a stability control module of a preferred embodiment of the present invention;

Fig. 5 is another schematic structural view of the optoelectronic oscillator of the preferred embodiment of the utility model;

Fig. 6 is the schematic diagram of the frequency spectrum of the oscillating signal of the optoelectronic oscillator in the preferred embodiment of the utility model, wherein (a) is a schematic diagram of the frequency spectrum before injecting the locking signal, and (b) is a schematic diagram of the frequency spectrum after injecting the locking signal;

Fig. 7 is a schematic diagram of the output stability of the optoelectronic oscillator of the preferred embodiment of the utility model;

Fig. 8 is a schematic diagram of the phase noise index of the optoelectronic oscillator in the preferred embodiment of the present invention.

Explanation of reference signs:

10. Laser;

20. Photoelectric loop; 21. Electro-optic modulator; 22. Optical fiber coil; 23. Photodetector; 24. Microwave amplifier; 25. Voltage-controlled phase shifter; 26. Narrowband filter;

30. Injection phase lock module; 31. First signal source; 32. Adjustable attenuator;

40. Stability control module; 41. Second signal source; 42. Phase shifter; 43. Mixer; 44. Low-pass filter; 45. Baseband signal processing module.

Detailed ways

The embodiments of the utility model will be described in detail below in conjunction with the accompanying drawings, but the utility model can be implemented in various ways defined and covered by the claims.

The utility model aims to provide a photoelectric oscillator capable of realizing low-phase-noise single-mode stable output of microwave oscillating signals, which is realized by combining injection phase-locking and pilot frequency control technologies, specifically, side-mode suppression is realized by using injection phase-locking mode , to ensure single-mode output, using pilot frequency control technology to overcome the impact of the environment on the optoelectronic oscillator to achieve stable output.

With reference to Fig. 1, the preferred embodiment of the present utility model provides a kind of optoelectronic oscillator, comprises the laser device 10 that is used to output optical carrier, and laser device 10 is connected and is used to form the photoelectric circulation circuit 20 of photoelectric hybrid resonant cavity, photoelectric oscillator also includes An injection phase-locked module 30 for injecting a locking signal into the photoelectric loop 20 for side mode suppression, and a stabilization control module 40 for pilot control to compensate the delay fluctuation of the photoelectric loop 20 . The optoelectronic oscillator in this embodiment combines the injection phase-locking and pilot frequency control technology, by setting the injection phase-locking module, by injecting the locking signal to the photoelectric circulation loop to realize side mode suppression, ensuring the single-mode stable output of the photoelectric oscillator, and by setting the stability control module , to extract the delay fluctuation of each device in the photoelectric cycle loop and perform corresponding delay fluctuation compensation to achieve the purpose of stabilizing the oscillation frequency, thereby realizing the low phase noise single-mode stable output of the photoelectric oscillator, and due to the pilot frequency control and The cyclic oscillation locked by injection locking signal is carried out in different frequency bands, which avoids mutual interference and effectively avoids the parasitic effect of control circuit noise on the oscillation signal. Not only that, the use of pilot frequency technology to achieve OEO stability control can also overcome the traditional In the phase-locked control, the reference source restricts the phase noise near the carrier frequency of the oscillating signal to ensure the realization of low phase noise performance in the full frequency band of OEO. .

Referring to Fig. 2, in the present embodiment, the photoelectric loop 20 includes: an electro-optic modulator 21, an optical fiber coil 22, a photodetector 23, a microwave amplifier 24, a voltage-controlled phase shifter 25, a narrowband filter 26 connected in sequence, and a narrowband filter The output terminal of the device 26 is connected to the electrical input terminal of the electro-optic modulator 21; the laser device 10 provides the optical carrier wave to be modulated, and the optical carrier wave sent by the laser device 10 is delayed by the optical fiber coil 22 after the electro-optic modulator 21, and the optical signal after the delay The electrical signal is restored by the photodetector 23, the electric signal is amplified by the microwave amplifier 24, and then the phase is adjusted by the voltage-controlled phase shifter 25. The voltage-controlled phase shifter 25 performs phase adjustment according to the output signal of the stability control module 40. After the phase adjustment After the electrical signal is filtered by the narrowband filter 26, it is fed back to the electro-optical modulator 21 to enter the next cycle. For some specific frequency signal, if it satisfies the Barkhausen condition (open-loop gain is greater than 1, and the phase difference is an integer multiple of 2π), the signal at this frequency can achieve positive feedback oscillation. In order to realize the low phase noise output of the oscillating circuit, the optical fiber coil in the ring is required to be long enough, and the long fiber delay causes the mode interval to be very small, and it is impossible to suppress the spurious mode with a narrowband filter in the microwave frequency band, resulting in "multimode output" question.

In this embodiment, the problem of "multi-mode coexistence" of the OEO is solved by using the injection phase-locked module 30 through microwave source injection locking, and the spurious mode of the optoelectronic oscillator is suppressed. Specifically, referring to FIG. 3 , the injection phase-locked module 30 includes a first signal source 31 for generating an injection signal and an adjustable attenuator 32 for adjusting the signal power of the injection signal. In this embodiment, the first signal source 32 A dielectric oscillator is used, the frequency of the injection source is consistent with the oscillation signal, and the output end of the adjustable attenuator 32 is coupled to the photoelectric loop 20 . In this embodiment, referring to FIG. 5 , the output terminal of the adjustable attenuator 32 is coupled to the connection channel between the narrowband filter 26 and the electrical input terminal of the electro-optical modulator 21 . As a reference source, the injected signal is coupled into the photoelectric loop through the adjustable attenuator 32, aligned with a certain mode frequency of the oscillating signal, and the injection locking is completed to effectively suppress other modes, aiming at realizing the single-mode output of the oscillating signal The adjustable attenuator 32 is used to adjust the power of the injected signal coupled into the photoelectric loop 20, because proper injected power is an effective way to balance phase noise and spurs. Specifically, for 6km optical fiber OEO, its mode interval is about 34kHz. Such a small bandwidth cannot be suppressed by narrowband filters in the microwave frequency band. The utility model adopts the microwave source injection locking method, and the injection source frequency is set to A certain mode frequency point of the quasi-oscillating signal makes the seed signal corresponding to this frequency point larger than other mode signals. As the number of cycles increases, the mode signal will gain an advantage in "mode competition", and finally realize effective for other spurious modes. suppressed for single-mode output.

In this embodiment, optionally, referring to FIG. 4 , the stabilization control module 40 includes a second signal source 41 for generating a pilot reference source, a phase shifter 42, a mixer 43, a low-pass filter 44, and a baseband signal Processing module 45; wherein, the signal output by the second signal source 41 is divided into two paths, one path is output to the mixer 43 after a 90-degree phase shift through the phase shifter 42, and the other path enters the photoelectric circulation loop 20 through the electro-optic modulator 21 , the electro-optic modulator 21 performs intensity modulation on the pilot reference source, then delays through the optical fiber coil 22, restores it to an electrical signal through the photodetector 23, and then amplifies it through the microwave amplifier 24 and then outputs it to the mixer 43, so as to communicate with another A pilot reference source after a 90-degree phase shift is used for frequency mixing and phase discrimination; the signal after phase discrimination is output to the baseband signal processing module 45 for processing through the low-pass filter 44, and the baseband signal processing module 45 finally converts the microwave optical chain The delay fluctuation information of the loop is converted into the control voltage of the voltage-controlled phase shifter 25. By changing the control voltage and adjusting the loop phase shift, the strict alignment between the injection source and the frequency of a certain oscillation mode of the long-loop OEO is realized to compensate for the photoelectric The time delay of the loop 20 fluctuates. Refer to FIG. 5 for a schematic structural diagram of the entire photoelectric oscillator.

The utility model adopts the pilot frequency control technology to control the stable output of the oscillating signal below:

Let the two input signals of the mixer 43 be:

In formula (1), V ₁ and V ₂ are the branch signals after the phase shift of the feedback branch respectively; A ₁ and A ₂ are the amplitudes of the two signals respectively, and ω is the frequency of the pilot signal; and Respectively, the phases of the two branches reaching the front-end signal of the mixer; is the phase fluctuation of the OEO loop.

After mixing the two branch signals:

After suppressing high-frequency components through a low-pass filter

is the phase difference of the two branches, when its value is an odd multiple of π/2, the above formula can be simplified as

if The above formula continues to simplify to

is the phase discrimination factor, and its value is It can be seen from the above formula that the phase change caused by the delay fluctuation is finally converted into a voltage signal, which is fed back to the voltage-controlled phase shifter of the OEO, and the frequency of the oscillation signal is adjusted by changing the loop phase to realize the stability control of the OEO. Generally speaking, electro-optic modulators and photodetectors are broadband devices, and microwave amplifiers are also easy to achieve broadband. Based on the above conditions, low-frequency detection signals can be used to extract the overall delay fluctuation of microwave photonic links.

Furthermore, in order to better illustrate the actual effect of the implementation of the utility model, physical verification is carried out based on the structure shown in FIG. 5 . The electro-optic modulator adopts the intensity modulator model IM-1550-12-PM from Optilab Company, with a working bandwidth of 12GHz and an insertion loss of 4dB; The laser is 40GHz, the responsivity is 0.65A/W1550nm; the laser adopts the narrow linewidth laser of EM4 company model AA1401-080-P, the linewidth is 1MHz, the output power is 80mW, and the relative intensity noise is -150dBc/Hz; the fiber coil adopts Corning's single-mode communication optical fiber has a loss of 0.2dB/km and a length of 6km; other components are commercial and domestic series.

Combined with Fig. 6 to analyze the side mode suppression of the OEO involved in the present invention. Firstly, a closed loop of OEO is formed to ensure that the loop gain is greater than 1. At this time, the mode satisfying the Barkhausen condition in the narrowband filter will generate oscillation, and the frequency spectrum of the oscillation signal is shown in Fig. 6(a); then, adopt A commercial dielectric oscillator (oscillation frequency of 10 GHz) injects OEO, adjusts the control voltage of the voltage-controlled phase shifter in the loop, and aligns the frequency of a certain mode with the frequency of the injected signal until the "injection locking" is completed, and finally realizes Single-mode output, as shown in Figure 6(b); finally, the phase noise of the oscillation signal can be further optimized by adjusting the injection power, modulator bias voltage, etc. As shown in Fig. 6, after the microwave injection locking scheme involved in the utility model, the side mode of the oscillating signal is significantly suppressed, which solves the "multi-mode coexistence" problem faced by OEO and realizes single-mode output.

The long-term stability of the OEO involved in the present utility model is analyzed in conjunction with FIG. 7 . In this embodiment, the second signal source 41 uses a 400 MHz commercial crystal oscillator source, that is, the detection signal mentioned in FIG. 5 of the present invention, as a pilot reference source for OEO. The detection signal is divided into two paths, one path enters the OEO circuit through the electro-optic modulator, after the electro-optic modulator performs intensity modulation on the optical carrier, it is delayed by a 6km-long fiber coil, and then recovered at the output end of the photodetector, amplified by the amplifier, and The other detection signal realizes frequency mixing and phase discrimination; the other signal needs to be shifted by 90° through a phase shifter before mixing, in order to achieve the purpose of phase detection. After phase discrimination, the baseband signal passes through the low-pass filter for noise suppression, and then reaches the baseband signal processing module. After the module realizes amplification, adaptation and other processing, it is fed back to the voltage-controlled phase shifter in the loop. By adjusting the voltage-controlled phase shifter The control voltage to "indirectly supplement" the delay fluctuation in the loop. As shown in Figure 7, the Allan variance of the OEO involved in the embodiment of the present invention is about 2.7×10 ^-12 in 1s, 6.7×10 ^{-13 in 10s, 1.9×10 -13 in} 100s and 1000s as low as 8.0×10 ^-14 .

The phase noise of the OEO involved in the present invention is analyzed in combination with FIG. 7 . The problems of "multi-mode coexistence" and "environmental sensitivity" of the OEO are solved by means of injection locking and pilot frequency control. The OEO phase noise index involved in this embodiment is shown in FIG. 8 . The side mode suppression ratio is higher than 95dBc; the phase noise index is -125dBc/Hz1kHz, -140dBc/Hz10kHz, which realizes low phase noise single-mode stable output.

The above descriptions are only preferred embodiments of the utility model, and are not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present utility model shall be included in the protection scope of the present utility model.

Claims (6)

1. An optoelectronic oscillator, comprising a laser (10) for outputting an optical carrier, said laser (10) is connected to a photoelectric cycle (20) for forming an optoelectronic hybrid resonator, characterized in that, The photoelectric oscillator also includes an injection phase-locked module (30) for injecting a locking signal into the photoelectric loop (20) to suppress side modes, and a pilot frequency control to compensate the photoelectric loop (20) The stability control module (40) of the time-delay fluctuation. 2. The photoelectric oscillator according to claim 1, characterized in that, The injection phase-locked module (30) includes a first signal source (31) for generating an injection signal and an adjustable attenuator (32) for adjusting the signal power of the injection signal, and the adjustable attenuator ( 32) is coupled to the photoelectric loop (20) at its output. 3. The photoelectric oscillator according to claim 2, characterized in that, The photoelectric loop (20) includes: an electro-optic modulator (21), an optical fiber coil (22), a photodetector (23), a microwave amplifier (24), a voltage-controlled phase shifter (25), a narrow-band filter device (26), the output end of the narrowband filter (26) is connected to the electrical input end of the electro-optic modulator (21); The optical carrier wave sent by the laser (10) is delayed by the optical fiber coil (22) after passing through the electro-optical modulator (21), and the delayed optical signal is restored to an electrical signal by the photodetector (23). signal, the electrical signal is amplified by the microwave amplifier (24) and then phase adjusted by the voltage-controlled phase shifter (25), and the voltage-controlled phase shifter (25) is adjusted according to the stability control module (40 ) the output signal is phase-adjusted, and the phase-adjusted electrical signal is fed back to the electro-optic modulator (21) after being filtered by the narrow-band filter (26) to enter the next cycle; The output terminal of the adjustable attenuator (32) is coupled to the connection channel between the narrowband filter (26) and the electrical input terminal of the electro-optical modulator (21). 4. The photoelectric oscillator according to claim 3, characterized in that, The stability control module (40) includes a second signal source (41) for generating a pilot reference source, a phase shifter (42), a mixer (43), a low-pass filter (44) and baseband signal processing module(45), The signal output by the second signal source (41) is divided into two paths, one path is output to the mixer (43) after being phase-shifted by the phase shifter (42), and the other path is passed through the electro-optic modulator ( 21) enter the photoelectric loop (20), and output to the mixer (43) through the microwave amplifier (24); The output end of the mixer (43) is connected to the low-pass filter (44), and the low-pass filter (44) is connected to the baseband signal processing module (45), and the baseband signal processing module (45 ) to generate a voltage control signal to the voltage input terminal of the voltage control phase shifter (25), to compensate the time delay fluctuation of the photoelectric loop (20). 5. The photoelectric oscillator according to claim 4, characterized in that, The angle at which the phase shifter shifts the phase of the signal output by the second signal source (41) is 90 degrees. 6. The photoelectric oscillator according to claim 4, characterized in that, The first signal source (31) adopts a dielectric oscillator, and the second signal source (41) adopts a crystal oscillator source.