KR20150033274A - Optical carrier control device and method for double sideband-suppressed carrier type optical fiber - Google Patents

Abstract

A method for controlling an optical carrier in a DSB-SC-type optical oscillator is disclosed. The method comprises the steps of: distributing an optical carrier output from an optical signal source having a single wavelength to generate a first separate carrier and a second separate carrier; generating an optically modulated carrier by optical intensity modulation of the first separate carrier; generating a reverse phase carrier having a 180-degree phase difference from the second separate carrier by optical phase modulation of the second separate carrier; generating an optical carrier suppression signal having the same size as the optically modulated carrier by adjusting the magnitude of the reverse phase carrier; and combining the optically modulated carrier with the optical carrier suppression signal.

Description

TECHNICAL FIELD [0001] The present invention relates to an optical carrier control apparatus and method for an optical oscillator of a DSB-SC type optical oscillator,

TECHNICAL FIELD The present invention relates to a technology for improving optical broadcast wave control efficiency in a double sideband-suppressed carrier (DSB-SC) generation mode in which optical carriers using a single wavelength optical signal, which is a generation method of millimeter wave and terahertz wave, are suppressed will be.

A millimeter wave and a terahertz wave generator using an optical signal are basically composed of an optical oscillator and a photomixier. The optical oscillator is composed of a single optical signal generator having a single wavelength or two optical signal generators having two different wavelengths, although the optical oscillator may differ depending on the construction method. Generally, since the output of the optical oscillator is composed of two or more optical signals of different wavelengths, only two optical signals having different wavelengths by the wavelength difference of the millimeter wave and the terahertz wave to be generated are selected It should be transferred to the light mixer. To do this, a notch filter (AWG) or an arrayed waveguide grating (AWG) using a fiber Bragg grating (FBG) is generally mounted between an optical oscillator and a light mixer. The two optical signals having different wavelengths, which are output from the optical oscillator, are beamed in the optical mixer to generate a millimeter wave or a terahertz wave signal having a frequency corresponding to the wavelength difference of the two optical signals. This method is defined as a photomixing method or an optical heterodyne method.

In the case of an optical oscillator using two optical signal sources having different wavelengths, a device for generating and maintaining a correlation between two different optical signal sources is indispensably required. The frequency drift and phase noise characteristics of the millimeter and terahertz wave signals generated according to the degree of correlation are determined. However, when two optical signals having different wavelengths are generated by using a single optical signal source having a single wavelength, two optical signals having different wavelengths are generated in the same signal source, . Therefore, there is an advantage that a separate correlation generating and maintaining device is not necessary.

An optical oscillator having an optical signal source of a single wavelength can be realized by a mode locking laser method, a dual mode laser method or an injection locking method and a double sideband- Suppressed Carrier, DSB-SC) generation method and frequency comb technique. In the case of the mode locking laser method and the dual mode laser method, it is difficult to fabricate an optical element and its competitiveness in terms of development cost and price is inadequate. Thus, the efficiency of commercialization is a problem. In order to obtain the desired signal frequency, And there is a disadvantage in that there is a limitation on the efficiency because the operating conditions are difficult. The frequency comb scheme is composed of a light source, an optical intensity modulator, an optical phase modulator, an AWG (Arrayed Waveguide Grating), and a light mixer. The frequency of the generated signal is determined by the performance of the optical phase modulator and AWG There is a disadvantage that an AWG is required which is variable, expensive, and has instability in design and temperature. The DSB-SC method is a kind of optical heterodyne scheme, and its construction is simple, and much research has been conducted since it is easy to obtain a signal of a desired frequency as compared with other techniques described above. However, this DSB-SC method also includes optical carrier signals in both sideband optical signals, which deteriorates the phase noise characteristics of millimeter wave and terahertz wave signals generated through the optical mixing process. To reduce the influence of such optical carriers, the operating point of the optical intensity modulator is maintained at a null point, and a notch filter is mounted between the optical intensity modulator and the optical mixer. However, since the notch filter generates a separate insertion loss, the optical carrier can not be completely removed because the optical carrier suppressing effect and the size of the both-side optical signal can be reduced simultaneously. In addition, since the notch filter changes its characteristics with respect to temperature, there is a limit in manufacturing a reliable optical oscillator.

Related Prior Art Japanese Patent Laid-Open No. 2007-047230 discloses an optical carrier suppression double-sideband modulation system capable of modulating a high extinction ratio.

An object of the present invention is to provide an optical carrier suppression and removal method of a DSB-SC type optical oscillator which is excellent in operation reliability according to temperature and does not affect the size of both sideband optical signals.

According to an aspect of the present invention, there is provided a method of controlling an optical carrier of a DSB-SC type optical oscillator, including dividing an optical carrier output from an optical signal source of a single wavelength to generate a first separated carrier and a second separated carrier step; Modulating the first separated carrier wave to generate a light-modulated carrier wave; Phase-modulating the second separated carrier wave to generate an inverted phase carrier wave having a phase difference of 180 degrees with the second separated carrier wave; Modulating the magnitude of the inverted phase carrier to generate a carrier suppression signal equal to the magnitude of the optical modulated carrier; And combining the optical modulated carrier and the optical carrier suppression signal.

At this time, the step of generating the first separated carrier wave and the second separated carrier wave can be selected and distributed according to the size of the optical carrier and the minimum input power of the optical phase modulator.

At this time, the combining step can be combined at a ratio of 50:50.

At this time, the step of generating the inverted phase carrier and the step of generating the optical carrier suppressing signal generate the inverted phase carrier and the optical carrier suppressing signal using the voltage supplied to the optical intensity modulator and the optical phase modulator in the voltage control device And control.

At this time, the voltage supplied from the voltage control device may be a bias voltage.

The optical carrier control device of the DSB-SC type optical oscillator according to an embodiment of the present invention may also include a first optical carrier control device for distributing the optical carrier output from the optical signal source of a single wavelength to generate a first separated carrier and a second separated carrier, Optocouplers; An optical intensity modulator for modulating the intensity of the first separated carrier wave to generate a light-modulated carrier wave; An optical phase modulator for performing optical phase modulation of the second separated carrier wave to generate an inverted phase carrier wave having a phase difference of 180 degrees with the second separated carrier wave; A light intensity controller for adjusting the intensity of the inverted phase carrier to generate an optical carrier suppression signal equal to that of the optical modulated carrier; And a second optical coupler for coupling the optical modulated carrier and the optical carrier suppression signal.

In this case, the first optical coupler can select a distribution ratio of optical carriers output from the single wavelength optical signal source according to the size of the optical carrier and the minimum input power of the optical phase modulator.

At this time, the second optical coupler may be a 50:50 optical coupler.

At this time, the apparatus may further include a voltage control device for supplying a voltage to the optical phase modulator and the light intensity controller.

At this time, the voltage control device may be a bias voltage.

According to the present invention, it is possible to provide an optical carrier suppression and removal method of a DSB-SC type optical oscillator which is excellent in operation reliability according to temperature and does not affect the size of both sideband optical signals.

1 is a flowchart illustrating a method of controlling an optical carrier of a DSB-SC type optical oscillator according to the present invention.
2 is a diagram showing the structure of a general DSB-SC type optical oscillator.
3 is a diagram illustrating a DSB-SC type optical oscillator including an optical carrier control apparatus according to an embodiment of the present invention.
4 is a diagram illustrating a DSB-SC type optical oscillator including an optical carrier controller using a light retarder according to an embodiment of the present invention.
5 is a diagram showing a bias characteristic of a balanced Mach-Zender modulator.

The present invention will now be described in detail with reference to the accompanying drawings. Hereinafter, a repeated description, a known function that may obscure the gist of the present invention, and a detailed description of the configuration will be omitted. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art. Accordingly, the shapes and sizes of the elements in the drawings and the like can be exaggerated for clarity.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart illustrating a method of controlling an optical carrier of a DSB-SC type optical oscillator according to the present invention.

Referring to FIG. 1, the optical carrier control method of a DSB-SC type optical oscillator according to the present invention generates a first separated carrier and a second separated carrier by distributing optical carriers output from a single wavelength optical signal source (S110 ). The output of a single wavelength optical signal source can be split into two paths through a 90:10 optocoupler, a 50:50 optocoupler, or a 99: 1 optocoupler. One path is a general DSB-SC path input to the optical intensity modulator, and can generate a both-side optical signal including an optical carrier, and the other path can be input to an optical phase modulator. When 90:10 optocouplers are used, 90% of the optical carriers output from the single wavelength optical signal source are divided and input to the optical intensity modulator, 10% of the optical carriers output from the single wavelength optical signal source are distributed, Can be input to the modulator. The reason for this distribution is to maximize the size of the both-side optical signal generated by distributing the output of the single-wavelength optical signal source. A 99: 1 optocoupler can also be used if the output signal of a single wavelength optical signal source is so large that 1% of the optical carrier is greater than or equal to the minimum input power of the optical phase modulator. Therefore, the optocoupler for distributing the output of the single wavelength optical signal source can select the ratio by considering the size of the optical carrier outputted from the single wavelength signal source and the minimum input power of the optical phase modulator.

The first separated carrier wave generated in step S110 is subjected to optical intensity modulation to generate a light-modulated carrier wave (S120). The first separated carrier wave generates both sideband optical signals and optical modulated carrier waves in accordance with the output frequency (f _LO ) and power of the local oscillator applied to the optical intensity modulator.

In addition, the second separated carrier wave generated in step S110 is subjected to optical phase modulation to generate an inverted phase carrier wave (S130).

The optical carrier suppression signal having the same magnitude as the optical modulation carrier is generated through the optical intensity control of the inverse phase carrier generated in step S130 (S140).

The optical carrier suppression signal generated in step S140 is combined with the optical modulated carrier wave through the second optical coupler (S150). At this time, the second optical coupler may be a 50:50 optical coupler.

By combining the optical modulated carrier and the optical carrier suppression signal in this way, both sideband optical signals in which the optical carrier is suppressed can be obtained. Such suppression of the optical carrier can be determined by the magnitude of the optical carrier suppression signal, the difference in size of the optical carrier and the accuracy of the phase modulation performance of the optical phase modulator. In general, since the optical phase modulator operated by the voltage is excellent in the operation reliability according to the temperature and the operation time, the present invention can achieve high operation reliability compared with the case of using a notch filter having a large temperature dependency in operation , It is possible to obtain both sideband optical signals whose size is not reduced. Therefore, excellent phase noise characteristics of millimeter wave and terahertz wave signals generated through the optical mixer can be expected. At this time, the optical phase modulator and the light intensity controller are generally determined by the bias voltage and the operating point is controlled by an electrical signal such as a voltage. Therefore, in addition to the configuration of the optical oscillator using the optical carrier control device according to the present invention, a voltage control device may be further included. Also, in order to compensate for the insertion loss of the second separated carrier wave generated in the optical phase modulation, the light intensity adjusting step may be performed after the optical phase modulation step.

2 is a diagram showing the structure of a general DSB-SC type optical oscillator.

2, a typical DSB-SC optical oscillator 200 includes a single wavelength optical signal source 210 for generating optical carriers, an optical intensity modulator 220 for generating both sideband optical signals, an optical intensity modulator 220 A local oscillator 230 for applying an RF signal having a modulation frequency and a power to the notch filter 240, and a notch filter 240 for reducing the influence of the optical carrier.

)를 출력하고 광 반송파는 광 강도 변조기(220)에 입력된다. 광 반송파는 광 강도 변조기(220)에 인가되는 국부 발진기(230)의 출력 주파수와 파워(f_LO)에 따라서 양측대역 광 신호(

)를 생성한다. 생성된 양측대역 광 신호는 광 반송파 신호를 포함하고 있다. 양측대역 신호에 포함되는 관 반송파 신호는 광 혼합 과정을 거쳐서 생성되는 밀리미터파 및 테라헤르츠파 신호의 위상잡음 특성을 악화시킨다. 광 반송파의 영향을 감소시키기 위하여 광 강도 변조기(220)의 동작점을 null point로 유지하며, 광 강도 변조기(220)와 광 혼합기 사이에 노치 필터(240)를 장착한다. 노치 필터(240)는 별도의 삽입손실을 발생시키므로 광 반송파 억압 효과와 동시에 양측대역 광 신호의 크기 또한 감소시킬 수 있다. 따라서 노치 필터(240)를 사용해서 광 반송파를 완전히 제거할 수는 없다. 또한 노치 필터(240)는 온도에 대한 특성 변화가 있으므로 신뢰성 높은 광 발진기 제작에는 한계가 있을 수 있다.
The optical signal source 210 of a single wavelength is an optical carrier

And the optical carrier is input to the optical intensity modulator 220. [ The optical carrier is modulated by the optical signal of the both-sideband optical signal ( _.lambda. ) According to the output frequency and power f.sub.LO of the local oscillator 230 applied to the optical intensity modulator 220

). The generated two-band optical signal includes an optical carrier signal. The tube carrier signal included in both sideband signals deteriorates the phase noise characteristics of the millimeter wave and terahertz wave signals generated through the optical mixing process. The operating point of the optical intensity modulator 220 is maintained at a null point and the notch filter 240 is mounted between the optical intensity modulator 220 and the optical mixer to reduce the influence of the optical carrier. Since the notch filter 240 generates a separate insertion loss, the optical carrier suppressing effect and the size of the both-side optical signal can be reduced at the same time. Therefore, the optical carrier can not be completely removed using the notch filter 240. Further, since the notch filter 240 changes its characteristics with respect to temperature, there is a limit to the fabrication of a reliable optical oscillator.

3 is a diagram illustrating a DSB-SC type optical oscillator including an optical carrier control apparatus according to an embodiment of the present invention.

3, a DSB-SC type optical oscillator 300 including an optical carrier control apparatus according to an exemplary embodiment of the present invention includes an optical signal source 310 of a single wavelength for outputting an optical carrier, A first optical coupler 315 for splitting the optical carrier outputted from the circle 310 to generate a first separated carrier wave and a second separated carrier wave, an optical intensity modulator 315 for generating an optical modulated carrier wave by modulating the intensity of the first separated carrier wave A local oscillator 330 for applying an RF signal having a modulation frequency and power to the optical intensity modulator 320, an optical phase modulator 330 for performing optical phase modulation on the second separated carrier, An optical phase modulator 340 for generating a carrier wave, a light intensity controller 350 for adjusting the magnitude of the inverted phase carrier to generate an optical carrier suppression signal equal in magnitude to that of the optical modulated carrier wave, an optical modulator carrier and an optical carrier suppression It consists of a second optical coupler (355) coupled to the call.

The first optical coupler 315 may select a ratio in consideration of the size of the optical carrier outputted from the single wavelength optical signal source 310 and the minimum input power magnitude of the optical phase modulator 340. The first optical coupler 315 may be a 90:10 optical coupler, a 50:50 optical coupler, or a 99: 1 optical coupler. When a 90:10 optical coupler or a 99: 1 optical coupler is used, 90% or 99% of the optical carrier is input to the optical intensity modulator 320 and 10% or 1% of the optical carrier is input to the optical phase modulator 340 Can be input. The reason for this input is to maximize the size of the double-band optical signal generated by distributing the output of the single-wavelength optical signal source 310. [

The optical intensity modulator 320 may generate optical modulated carrier wave by modulating optical intensity of the first separated carrier wave. The first separated carrier, which is divided in the optical carrier and inputted to the optical intensity modulator 320, is modulated into the both-side optical signal and the optical modulated carrier according to the output frequency and power of the local oscillator 330 in the optical intensity modulator 320.

The optical phase modulator 340 may perform optical phase modulation of the second separated carrier wave to generate an inverted phase carrier wave having a phase difference of 180 degrees with the second separated carrier wave. At this time, the optical phase modulator 340 determines an operating point by a bias voltage and can be controlled by an electrical signal such as a voltage.

The light intensity controller 350 can generate the optical carrier suppression signal equal to the size of the optical modulated carrier by adjusting the optical intensity of the magnitude of the inverted phase carrier. At this time, the light intensity controller 350 determines the operating point by the bias voltage and can be controlled by an electrical signal such as a voltage.

The second optical coupler 355 can combine the optical modulated carrier and the optical carrier suppression signal, thereby effectively suppressing the optical modulated carrier. Such an optical coupler 355 may be a 50:50 optical coupler.

The optical carrier control method according to the present invention can suppress the optical modulated carrier wave generated in this way and control the optical modulated carrier wave without affecting the size of the both side optical signal when suppressing the optical modulated carrier wave.

The above-described optical carrier control device of the DSB-SC type optical oscillator can generate millimeter wave and terahertz wave having excellent phase noise characteristics compared with the conventional DSB-SC type optical oscillator. In a typical DSB-SC optical oscillator, a notch filter or an AWG is mounted between an optical oscillator and a light mixer to suppress an optical carrier. However, this method has a problem in that a separate insertion loss is generated, In the case of the notch filter, there is a limit to the fabrication of a highly reliable optical oscillator due to the characteristic change with respect to temperature. However, the optical carrier control method according to the present invention can solve such a problem, and thus it can help manufacture a highly reliable optical oscillator.

4 is a diagram illustrating a DSB-SC type optical oscillator including an optical carrier controller using a light retarder according to an embodiment of the present invention.

Referring to FIG. 4, a DSB-SC type optical oscillator 400 including an optical carrier controller using a light retarder according to an embodiment of the present invention includes a single wavelength optical signal source 410 for outputting an optical carrier, A first optical coupler 415 for splitting the optical carrier outputted from the optical signal source of the wavelength to generate the first separated carrier and the second separated carrier wave, A local oscillator 430 for applying an output frequency and power to the modulator 420 and the optical intensity modulator 420 and an inverted phase carrier having a phase difference of 180 degrees from the second separated carrier wave by delaying the phase of the second separated carrier wave A light intensity modulator 450 for modulating the magnitude of the inverted phase carrier to generate an optical carrier suppression signal that is unified with the size of the optical modulated carrier by adjusting the intensity of the inverted phase carrier, And a second optical coupler 455 for coupling.

The first optical coupler 415 can select a ratio in consideration of the size of the optical carrier output from the single wavelength optical signal source 410 and the minimum input power magnitude of the optical retarder 440. The first optical coupler 415 may be a 90:10 optical coupler, a 50:50 optical coupler, or a 99: 1 optical coupler. When 90:10 optical coupler or 99: 1 optical coupler is used, 90% or 99% of the optical carrier is input to the optical intensity modulator 420 and 10% or 1% of the optical carrier is input to the optical retarder 440 Can be input. The reason for this input is to maximize the size of the both-side optical signal generated by distributing the output of the single-wavelength optical signal source 410.

The optical intensity modulator 420 may generate optical modulated carrier wave by modulating the intensity of the first separated carrier wave. The first separated carrier, which is divided by the optical carrier and input to the optical intensity modulator 420, is modulated by the optical intensity modulator 420 into the both-side optical signal and the optical modulated carrier according to the output frequency and power of the local oscillator 430. The optical carrier control method according to the present invention can suppress the optical modulated carrier wave generated in this way and control the optical modulated carrier wave without affecting the size of the both side optical signal when suppressing the optical modulated carrier wave.

The optical delay 440 may generate an inverted phase carrier having a phase difference of 180 degrees from the second separated carrier by delaying the phase of the second separated carrier. At this time, the optical retarder 440 is determined by the bias voltage and can be controlled by an electrical signal such as a voltage. The delay resolution and the delay range of the optical retarder 440 vary depending on the wavelength of the optical signal to be used. However, when using the wavelength of 1550 nm, the delay resolution of 0.1 fs or less, May be preferred.

The optical intensity controller 450 can adjust the magnitude of the inverted phase carrier to generate the optical carrier suppression signal equal to that of the optical modulated carrier. At this time, the light intensity controller 450 determines the operating point by the bias voltage and can be controlled by an electrical signal such as a voltage.

The second optical coupler 455 can combine the optical modulated carrier and the optical carrier suppression signal, thereby effectively suppressing the optical modulated carrier. Such an optical coupler 455 may be a 50:50 optical coupler.

The above-described optical carrier control device of the DSB-SC type optical oscillator can generate millimeter wave and terahertz wave having excellent phase noise characteristics compared with the conventional DSB-SC type optical oscillator. In a typical DSB-SC optical oscillator, a notch filter or an AWG is mounted between an optical oscillator and a light mixer to suppress an optical carrier. However, this method has a problem in that a separate insertion loss is generated, In the case of the notch filter, there is a limit to the fabrication of a highly reliable optical oscillator due to the characteristic change with respect to temperature. However, the optical carrier control method according to the present invention can solve such a problem, and thus it can help manufacture a highly reliable optical oscillator.

5 is a diagram showing a bias characteristic of a balanced Mach-Zender modulator.

Referring to FIG. 5, when the bias voltage of the balanced Mach-Zehnder modulator is adjusted to be 2? As shown in FIG. 5, an inverted phase carrier having a phase difference of 180 degrees with the second separated carrier wave can be generated using an optical phase modulator have. Therefore, the present invention can be constructed by using a balanced Mach-Zender modulator.

As described above, the optical carrier control apparatus and method of the DSB-SC type optical oscillator according to the present invention are not limited to the configuration and method of the embodiments described above, All or some of the embodiments may be selectively combined.

200: DSB-SC type optical oscillator
210, 310, 410: a single wavelength optical signal source
220, 320, 420: optical intensity modulator
230, 330, 430: local oscillator
240: Notch filter
300: Optical carrier control device of DSB-SC type optical oscillator
315, 415: a first optical coupler
340: optical phase modulator
350, 450: Light intensity controller
355, 455: a second optical coupler
440: optical retarder

Claims (1)

Generating a first separated carrier wave and a second separated carrier wave by distributing the optical carrier outputted from the optical signal source of a single wavelength;
Modulating the first separated carrier wave to generate a light-modulated carrier wave;
Phase-modulating the second separated carrier wave to generate an inverted phase carrier wave having a phase difference of 180 degrees with the second separated carrier wave;
Modulating the magnitude of the inverted phase carrier to generate a carrier suppression signal equal to the magnitude of the optical modulated carrier; And
And combining the optical modulated carrier with the optical carrier suppression signal. The optical carrier control method of a DSB-SC type optical oscillator according to claim 1,

Images