阅读说明：本技术 一种谐波深度抑制的宽带移频装置 (Broadband frequency shift device with harmonic wave depth suppression function ) 是由 杨波 黄超群 池灏 杨淑娜 欧军 翟彦蓉 于 2020-12-31 设计创作，主要内容包括：本发明涉及一种谐波深度抑制的宽带移频装置,包括激光器、光分路器、上行双平行调制器、下行双平行调制器、光移相器、光合路器、微波耦合器和电源控制单元；其中,激光器输出的激光经光分路器分路输入上行双平行调制器和下行双平行调制器；射频信号通过微波耦合器分成4路并通过不同相移后加载在上行双平行调制器和下行双平行调制器的4个子调制器的射频输入口,通过调节直流偏置点电压和光移相器实现频率右移或左移,改变射频信号的频率可以改变移频量；本发明可实现谐波深度抑制的宽带移频信号,应用于光传感测量、光频梳产生等领域。(The invention relates to a broadband frequency shift device for harmonic depth suppression, which comprises a laser, an optical splitter, an uplink double-parallel modulator, a downlink double-parallel modulator, an optical phase shifter, an optical combiner, a microwave coupler and a power control unit, wherein the laser is connected with the optical splitter; laser output by the laser is split by the optical splitter and input into the uplink double-parallel modulator and the downlink double-parallel modulator; the radio frequency signal is divided into 4 paths by the microwave coupler, and loaded on the radio frequency input ports of 4 sub-modulators of the uplink dual-parallel modulator and the downlink dual-parallel modulator after different phase shifts, frequency right shift or left shift is realized by adjusting direct current bias point voltage and the optical phase shifter, and the frequency shift quantity can be changed by changing the frequency of the radio frequency signal; the invention can realize a broadband frequency shift signal for harmonic depth suppression, and is applied to the fields of optical sensing measurement, optical frequency comb generation and the like.)

1. A broadband frequency shift device with harmonic deep suppression is characterized in that: the device comprises a laser (1), an optical splitter (2), an uplink double-parallel modulator (3), a downlink double-parallel modulator (4), an optical phase shifter (5), an optical combiner (6), a microwave coupler (7) and a power control unit (11); laser output by the laser (1) is split and input into the uplink double-parallel modulator (3) and the downlink double-parallel modulator (4) through the optical splitter (2); the radio frequency signal is divided into 4 paths through a microwave coupler (7) and loaded on the radio frequency input ports of 4 sub-modulators of an uplink double-parallel modulator (3) and a downlink double-parallel modulator (4) after different phase shifts, the power supply control unit (11) controls 6 direct current bias points of the uplink double-parallel modulator (3) and the downlink double-parallel modulator (4) to enable the uplink double-parallel modulator and the downlink double-parallel modulator to work in a carrier suppression single-sideband modulation mode, adjusts an optical phase shifter (5) to enable high-order harmonic phases output by the uplink double-parallel modulator (3) and the downlink double-parallel modulator (4) to be opposite, and obtains a frequency shift signal with high-order harmonic depth suppression after being combined by an optical combiner (6); the frequency is shifted to the right or left by adjusting the DC bias point voltage and the optical phase shifter (5), and the frequency shift amount can be changed by changing the frequency of the radio frequency signal.

2. The harmonic deep suppressed broadband frequency shifting apparatus of claim 1, wherein: the 4 sub-modulators include a sub-modulator 1(3a), a sub-modulator 2(3b), a sub-modulator 3(4a), and a sub-modulator 4(4 b); the sub-modulators 1(3a) and 2(3b) are mounted on the upstream dual-parallel modulator (3), and the sub-modulators 3(4a) and 4(4b) are mounted on the downstream dual-parallel modulator (4).

3. The harmonic deep suppressed broadband frequency shifting apparatus of claim 1, wherein: the microwave coupler (7) is respectively and electrically connected with the first electric phase shifter (8), the second electric phase shifter (9) and the third electric phase shifter (10).

4. A harmonic depth suppression broadband frequency shifting apparatus according to claim 3, wherein: the phase shift of the first electric phase shifter (8) is 90 degrees, the phase shift of the second electric phase shifter (9) is 45 degrees, and the phase shift of the third electric phase shifter (10) is 135 degrees.

5. The harmonic deep suppressed broadband frequency shifting apparatus of claim 4, wherein: and 4 sub-modulators of the uplink double-parallel modulator (3) and the downlink double-parallel modulator (4) are in a push-pull working mode.

6. The harmonic deep suppressed broadband frequency shifting apparatus of claim 5, wherein: the uplink double-parallel modulator (3) and the downlink double-parallel modulator (4) have 6 direct current bias inputs, wherein the input voltages of the bias 1, the bias 2, the bias 4 and the bias 5 are equal to the half-wave voltage V of the modulators_πWherein the offset 3 and the offset 6 are 3V according to the frequency right shift or the frequency left shift respectively_π/2 or V_π/2。

7. The harmonic deep suppressed broadband frequency shifting apparatus of claim 1, wherein: the power supply control unit (11) controls 6 bias points of the uplink double-parallel modulator (3) and the downlink double-parallel modulator (4) and is any one of a stabilized voltage power supply and an automatic bias control circuit.

8. The harmonic deep suppressed broadband frequency shifting apparatus of claim 1, wherein: the phase shift caused by the optical phase shifter (5) is 7 pi/4 when the frequency is shifted to the right, and pi/4 when the frequency is shifted to the left.

9. The harmonic deep suppressed broadband frequency shifting apparatus of claim 8, wherein: the optical phase shifter (5) is an adjustable optical delay line and can also be other devices capable of realizing optical phase shifting.

Technical Field

The invention belongs to the technical field of microwave photonics, and particularly relates to a broadband frequency shift device for harmonic depth suppression.

Background

The frequency shift is an important means for signal processing, because the frequency shift is only the change of the center frequency of the signal, and has no influence on the important information such as the phase of the signal, and the frequency shift technology is widely applied in many fields, such as doppler vibrometer, optical gyroscope, microwave signal generation, and optical frequency comb signal generation. The frequency shift method mainly comprises two methods, namely, the first method utilizes an acousto-optic frequency shifter to shift frequency, and the second method utilizes a double-parallel modulator to achieve carrier suppression single sideband modulation to achieve the purpose of frequency shift. The frequency shift principle of the acousto-optic frequency shifter is that a piezoelectric transducer is used for converting a driving signal into an ultrasonic field, the ultrasonic field and the optical field interact to form a volume grating in an acousto-optic crystal, and then incident laser is diffracted. The frequency shift of the double parallel modulators is completed by a method of carrier suppression single sideband, two sub-modulators of the double parallel modulators respectively generate carrier suppression double sidebands with different phases, and then a combiner generates optical interference to eliminate the sidebands on one side. For the frequency shift of the acousto-optic frequency shifter, the frequency shift range is small, often within hundred megahertz, and the acousto-optic frequency shifter is not suitable for the scene needing broadband frequency shift (such as optical frequency comb generation). The frequency shift using the dual parallel modulator is affected by higher harmonics such as third harmonic, and it is difficult to generate a frequency shift signal with suppressed harmonic depth.

In view of the above problems, it is necessary to improve them.

Disclosure of Invention

Based on the above-mentioned shortcomings in the prior art, the present invention provides a broadband frequency shifting apparatus and method for harmonic depth suppression.

In order to achieve the above purposes, the technical scheme adopted by the invention is as follows: a broadband frequency shift device for harmonic depth suppression comprises a laser, an optical splitter, an uplink double-parallel modulator, a downlink double-parallel modulator, an optical phase shifter, an optical combiner, a microwave coupler and a power control unit; laser output by the laser is split by the optical splitter and input into the uplink double-parallel modulator and the downlink double-parallel modulator; the radio frequency signal is divided into 4 paths by a microwave coupler and loaded on the radio frequency input ports of 4 sub-modulators of an uplink double-parallel modulator and a downlink double-parallel modulator after different phase shifts, the power supply control unit controls 6 direct current bias points of the uplink double-parallel modulator and the downlink double-parallel modulator to enable the uplink double-parallel modulator and the downlink double-parallel modulator to work in a carrier suppression single-sideband modulation mode, the optical phase shifter is adjusted to enable high-order harmonic phases output by the uplink double-parallel modulator and the downlink double-parallel modulator to be opposite, and a frequency shift signal with high-order harmonic depth suppression is obtained after the optical combiner; the frequency is shifted to the right or left by adjusting the DC bias voltage and the optical phase shifter, and the frequency shift amount can be changed by changing the frequency of the radio frequency signal.

As a preferred aspect of the present invention, the 4 sub-modulators include a sub-modulator 1, a sub-modulator 2, a sub-modulator 3, and a sub-modulator 4; the sub-modulator 1 and the sub-modulator 2 are installed on the uplink dual-parallel modulator, and the sub-modulator 3 and the sub-modulator 4 are installed on the downlink dual-parallel modulator.

As a preferable aspect of the present invention, the microwave coupler is electrically connected to the first electric phase shifter, the second electric phase shifter, and the third electric phase shifter, respectively.

In a preferred embodiment of the present invention, the phase shift of the first electrical phase shifter is 90 °, the phase shift of the second electrical phase shifter is 45 °, and the phase shift of the third electrical phase shifter is 135 °.

As a preferred scheme of the present invention, the 4 sub-modulators of the uplink and downlink dual-parallel modulators are both in a push-pull mode.

As a preferable scheme of the invention, the uplink double-parallel modulator and the downlink double-parallel modulator have 6 direct current bias inputs, wherein the input voltage of the bias 1, the bias 2, the bias 4 and the bias 5 is equal to the half-wave voltage V of the modulator_πWherein the offset 3 and the offset 6 are 3V according to the frequency right shift or the frequency left shift respectively_π/2 or V_π/2。

As a preferred embodiment of the present invention, the power supply control unit controls 6 bias points of the upstream dual-parallel modulator and the downstream dual-parallel modulator, and is any one of a regulated power supply and an automatic bias control circuit.

In a preferred embodiment of the present invention, the phase shift of the optical phase shifter is 7 pi/4 when the frequency is shifted to the right and pi/4 when the frequency is shifted to the left.

As a preferred embodiment of the present invention, the optical phase shifter is an adjustable optical delay line, and may also be other devices capable of realizing optical phase shifting.

The invention has the beneficial effects that:

(1) the frequency shift quantity is changed by adjusting the frequency of the radio frequency signal, and the frequency shift frequency is adjustable in broadband.

(2) By suppressing the power of the high-order harmonic component, the side mode suppression ratio of the frequency shift signal is greatly improved.

Drawings

FIG. 1 is a schematic diagram of the basic structure of a harmonic deep-suppressing broadband frequency-shifting apparatus and method implemented in the present invention;

FIG. 2 is a frequency right-shifted spectrum of harmonic depth suppression in an ideal situation for an implementation of the present invention;

FIG. 3 is a frequency left shifted spectrum of harmonic depth suppression in an ideal situation for an implementation of the present invention;

reference numbers in the figures: 1. the optical fiber laser comprises a laser, 2 an optical splitter, 3 an uplink double-parallel modulator, 3(a) a sub-modulator 1, 3(b) a sub-modulator 2, 4a downlink double-parallel modulator, 4(a) a sub-modulator 3, 4(b) a sub-modulator 4, 5 an optical phase shifter, 6 an optical combiner, 7 a microwave coupler, 8 a first electric phase shifter, 9 a second electric phase shifter, 10 a third electric phase shifter and 11 a power supply control unit.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example (b):

as shown in fig. 1, the present invention provides a broadband frequency shift device with deep harmonic suppression. The unit comprises a laser 1, an optical splitter 2, an uplink double-parallel modulator 3, a downlink double-parallel modulator 4, an optical phase shifter 5, an optical combiner 6, a microwave coupler 7, a first electric phase shifter 8, a second electric phase shifter 9, a third electric phase shifter 10 and a power supply control unit 11; laser output by a laser 1 is input into an uplink double-parallel modulator 3 and a downlink double-parallel modulator 4 through a branch of an optical splitter 2, a radio frequency signal is divided into 4 paths through a microwave coupler 7 and loaded on radio frequency input ports of 4 sub-modulators of the two double-parallel modulators after different phase shifts, the sub-modulators 1, the sub-modulators 2, the sub-modulators 3 and the sub-modulators 4 all work in a push-pull working mode, the phase shift of a first electric phase shifter is 90 degrees, the phase shift of a second electric phase shifter is 45 degrees, and the phase shift of a third electric phase shifter is 135 degrees. By adjusting the output voltage of the power control unit 11, the sub-modulators 1, 2, 3 and 4 are operated at the minimum bias point, i.e. the phase shift caused by the bias 1, 2, 4, 5 is pi, if the frequency shift to the right (frequency increase) is to be completed, the phase shift caused by the bias 3, 6 is to be 3 pi/2, the phase shift caused by the optical phase shifter 9 is 7 pi/4, if the frequency shift to the left (frequency decrease) is to be completed, the phase shift caused by the bias 3, 6 is to be pi/2, and the phase shift caused by the optical phase shifter 9 is pi/4.

The specific principle is illustrated as follows: assuming that the optical field of the input optical signal isA is the laser signal amplitude, omega₁For the angular frequency of the laser signal, the RF signal is V ═ V_RFcos(ω₂t),V_RFFor the amplitude, omega, of the radio-frequency signal₂Considering the ideal splitting condition (the ratio of the upper and lower optical powers is 1:1) for the angular frequency of the rf signal, if the frequency is shifted to the right (the frequency is increased):

the sub-modulator 1 works at a minimum bias point, generates a double-sideband signal for inhibiting even harmonic, and outputs an optical field expression of the optical signal as follows:

the optical field expression of the output optical signal of the sub-modulator 2 is:

the phase shift caused by the bias 3 is 3 pi/2, and the optical field expression of the output optical signal of the uplink double-parallel modulator is as follows:

similarly, the optical field expression of the output optical signal of the downlink double-parallel modulator is as follows:

it can be seen that the output signal of the upstream double-parallel modulator 3 and the output signal of the downstream double-parallel modulator 4 differ only in phase and only 4n +1 order sidebands are present. After the optical signal of the downlink dual-parallel modulator 4 is subjected to 7 pi/4 phase shifting by the optical phase shifter 10, the optical field expression of the optical signal output by the optical combiner 6 is as follows:

we can obtain the expression of the optical field of the output optical signal as:

wherein m ═ pi × V_RF/V_πIs a modulation factor, J_n() Representing a first type of bessel function.

According to the formula, the output optical signal is mainly a positive-order right frequency shift signal, and the maximum side mode is a negative seven-order side band, so that the right frequency shift signal with harmonic depth suppression is obtained.

If a frequency shift left is to be achieved (frequency becomes smaller):

the sub-modulator 1 works at a minimum bias point, generates a double-sideband signal for inhibiting even harmonic, and outputs an optical signal optical field expression as follows:

the optical field expression of the output optical signal of the sub-modulator 2 is as follows:

the phase shift caused by the bias 3 is pi/2, and the optical signal optical field expression output by the uplink double-parallel modulator 3 is as follows:

similarly, the optical signal optical field expression output by the downlink dual-parallel modulator 4 is:

it can be seen that the output signal of the upstream double-parallel modulator 3 and the output signal of the downstream double-parallel modulator 4 differ only in phase and only 4n +3 order sidebands are present. After the optical signal of the downlink dual-parallel modulator 4 is subjected to pi/4 phase shift by the optical phase shifter 10, the optical field expression of the optical signal output by the optical combiner 6 is as follows:

we can obtain the expression of the optical field of the output optical signal as:

wherein m ═ pi × V_RF/V_πIs a modulation factor, J_n() Representing a first type of bessel function.

According to the formula, the output optical signal is mainly a left frequency shift signal of negative first order, and the maximum side mode is a side band of positive seventh order, so that the left frequency shift signal with harmonic wave depth suppression is obtained.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention; thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Although the reference numerals in the figures are used more here: 1. laser, 2 optical splitter, 3 uplink dual parallel modulator, 3(a) sub-modulator 1, 3(b) sub-modulator 2, 4 downlink dual parallel modulator, 4(a) sub-modulator 3, 4(b) sub-modulator 4, 5 optical phase shifter, 6 optical combiner, 7 microwave coupler, 8 first electrical phase shifter, 9 second electrical phase shifter, 10 third electrical phase shifter, 11 power control unit, etc., without excluding the possibility of using other terms. These terms are used merely to more conveniently describe and explain the nature of the present invention; they are to be construed as being without limitation to any additional limitations that may be imposed by the spirit of the present invention.