KR100892783B1 - Mode selection method and apparatus of opto-electronic oscillator - Google Patents

Abstract

The present invention relates to a method and apparatus for selecting a photoelectric oscillation mode, and more particularly, to a method and apparatus for selecting or filtering only one of several oscillation modes present in an opto-electronic oscillator (OEO). The photoelectric oscillation mode selection device of the present invention generates a multi-mode signal belonging to a predetermined frequency band through a cyclic loop structure in which photoelectric conversion is repeated, and at least a part of the multi-mode electrical signal transmitted through the path of the electrical signal. It includes a photoelectric oscillator for outputting to the outside, and an electrical oscillator for receiving a multi-mode electrical signal output from the photoelectric oscillator, and outputs a single mode electrical signal belonging to a predetermined frequency band by insertion-locking. According to the present invention, it is possible to implement a high-Q filter, which is difficult to implement in the prior art, and to generate a signal having very low phase noise in the millimeter wave band, thereby improving the performance of the millimeter wave wireless communication transceiver. It can be implemented through simplified components, reducing system cost.

Photoelectric Oscillator, OEO, Mode Selection

Description

Mode selection method and apparatus of opto-electronic oscillator

The present invention relates to a method and apparatus for selecting a photoelectric oscillation mode, and more particularly, to a method and apparatus for selecting or filtering only one mode among various oscillation modes existing in an opto-electronic oscillator (OEO). The present invention also relates to a mode selection method and apparatus that can be utilized in a wireless communication system and an optical wireless convergence system in the millimeter wave band.

Photoelectric oscillators, or OEOs, have been studied a lot because they can generate signals with very low phase noise in high frequency bands such as millimeter waves using long optical delay lines. However, OEO using a 1km optical delay line will oscillate several modes at intervals of about 200kHz, which degrades the performance of the system. Therefore, there is a need for a system for selecting only one mode among several modes in OEO.

In recent years, OEO systems using an external resonator having a high good quality (Q) have been actively studied because they have low phase-noise signal generation. In particular, dual loop OEO, consisting of short and long optical loops, has become a very important issue. This dual loop has low output phase noise in long optical loops and 60dB of parent suppression ratio (SMSR) even with short loops. However, there is a limit to the SMSR that can be secured by the dual loop oscillator. This is because the two optical loops are coupled to each other, and the parents suppressed by the shorter loop are still obtained in the longer loop.

Zhou and Blasche have disclosed dual OEO using insert-lock as the OEO for parental suppression. In the dual OEO system, an OEO with a long loop inserts-locks a single mode OEO with a short loop. In this case, since the two OEOs are not combined with each other like the dual loop OEO described above, they have a very high SMSR value. However, even if the short loop OEO has a long optical delay line, optical fibers such as patch cords for connecting optical components or Er-doped fibers to compensate for optical losses are quite large in the millimeter wave band. There is a problem in creating a Q resonator, which results in a narrow locking range.

Therefore, the oscillation frequency of the inserted OEO mode must be large so that the injection power can be tuned correctly or the frequency can be within the locked range of the locked OEO. However, there is a problem that none of the above is easy to realize in the millimeter wave band, and also in this structure, there is a problem of cost because high speed optical and electrical components must be used for both OEOs.

As a related document, US 5,723,856 discloses an Opto-electronic oscillator (OEO) with an electro-optic modulator comprising an input for receiving an electrical control signal, an optical output and a filter. In the case of the patent, it is possible to select a single mode signal by simply inserting a filter in the OEO, but there is a problem that it is difficult to apply to a high frequency band such as a millimeter wave band.

US 5,777,778 discloses a versatile optical RF oscillator that introduces a multi-pitback loop with different delay times as an oscillator for single mode signal selection. In the case of the patent, the selection performance is not excellent, and an expensive high-speed photo detector corresponding to the number of optical delay lines is required, and thus there is a problem of cost burden.

US 7,151,415 discloses a master oscillator for generating a high good quality (Q) RF output signal and an insertion locked photoelectric oscillator for inputting the RF output signal to select a single mode signal of a particular frequency band. However, in this case, since two OEOs are required, there is a problem of cost burden when implementing the actual system.

In view of the above-mentioned problems of the prior art, the present invention generates a signal having very low phase noise in the millimeter wave band by introducing an independent electric oscillator to select one mode among the multi modes generated in the photoelectric oscillator. An object of the present invention is to provide an apparatus and method for selecting a photoelectric oscillation mode for improving the performance of a transceiver for a millimeter-kitter radio communication.

The photoelectric oscillation mode selection device according to the present invention for solving the above technical problem has a multi-mode belonging to a predetermined frequency band through a cyclic loop structure in which the optical signal transmission path and the electrical signal transmission path, and the photoelectric conversion is repeated A photoelectric oscillator which generates a signal of and outputs at least a portion of a multi-mode electrical signal transmitted through a path of the electrical signal to the outside; And an electrical oscillator having a circulation path of an electrical signal and receiving a multi-mode electrical signal output from the photoelectric oscillator and outputting a single mode electrical signal belonging to a predetermined frequency band by insertion-locking.

The photoelectric oscillation mode selection device of the present invention includes two oscillators, namely a photoelectric oscillator (OEO) and an electrical oscillator. The photoelectric oscillation mode selection apparatus of the present invention is distinguished from the conventional one in that multiple OEO modes generated in the OEO are inserted into the electric oscillator. One of the inserted modes, that is, close to the mode frequency of the loop of the electrical oscillator, inserts and locks the electrical mode. However, other modes are thoroughly suppressed. This is because the phase matching condition oscillates in the electrical oscillator. For the stable insert-lock in the present invention, the power of the inserted OEO modes is limited so that the lock range is lower than the FSR / 2 value, which means the frequency interval between the OEO modes. If the proper injection power is maintained to satisfy this condition, only the mode in which the electrical mode is inserted-locked among the various injected OEO modes will be output to the electrical oscillator output terminal. At this time, other modes that do not insert-lock the electric mode are suppressed in the electric oscillator, so that a high SMSR can be obtained. In addition, the insert-locked mode on the output of the electrical oscillator follows the phase noise characteristics of the insert-locked OEO mode. Another OEO mode can be selected by tuning a phase regulator inserted into the electrical oscillator. Because it can change the oscillation frequency of the electrical mode.

According to another aspect of the present invention, there is provided an apparatus for selecting a photoelectric oscillation mode according to the present invention, an electro-optic modulator for outputting an optical signal as an input, a first amplifying unit for amplifying an optical signal from the electro-optic modulator, An optical fiber for receiving an optical signal from the first amplifier and generating an optical delayed optical signal, an optical detector for outputting an electrical signal as the optical delayed optical signal, and an electrical signal of a part of the electrical signal from the optical detector Is output to the outside, and the remaining electrical signal is input to the all-optical modulation again, a first coupler for filtering an electrical signal belonging to a predetermined frequency band from the remaining electrical signal, and a first amplifying the remaining electrical signal. It is provided with two amplification units, and a predetermined loop through a cyclic loop structure in which photoelectric conversion is repeated Optoelectronic oscillator for generating a signal of a multi-mode belonging to a frequency band; And a second coupler receiving a multi-mode electrical signal output from the photoelectric oscillator, a third amplifier amplifying the electrical signal from the second coupler, and a single mode belonging to a predetermined frequency band in the amplified electrical signal. A second filter unit for filtering an electrical signal of the second filter unit, the third unit outputting some of the electrical signals of the filtered single mode electrical signal and transmitting the remaining electrical signals to the second coupler, by insert-locking An electrical oscillator for outputting an electrical signal of a single mode belonging to a predetermined frequency band.

In accordance with another aspect of the present invention, there is provided a method of selecting a photoelectric oscillation mode according to the present invention. Generating a mode signal; b) outputting at least some of the multi-mode electrical signals transmitted through the path of the electrical signals; And c) receiving the output multi-mode electrical signal and outputting a single mode electrical signal belonging to a predetermined frequency band by insertion-locking.

In the present invention, step a) is performed by a photoelectric oscillator, in particular an all-optical modulation step of outputting an optical signal as an input of an electrical signal, amplifying the output optical signal, and delayed light receiving the amplified optical signal. Generating a signal, a photoelectric modulation step of outputting an electrical signal as an input of the optical delayed optical signal and amplifying the output electrical signal is preferred.

In the present invention, step b) is a step performed by the coupler. The coupler is a component of the photoelectric oscillator that transmits some of the oscillated electrical signal to the electrical oscillator through the circulation loop of the photoelectric oscillator.

In the present invention, step c) is performed by the electrical oscillator, and inputting and amplifying the multi-mode electrical signal output through the step b), the electrical signal of a single mode belonging to a predetermined frequency band in the amplified electrical signal Filtering; And outputting an electrical signal of some of the filtered single mode electrical signals.

According to the present invention, by introducing an independent electric oscillator to select one mode among the multi-modes generated in the photoelectric oscillator, it is possible to implement a high-Q filter that is difficult to implement in the conventional electrical method. In addition, according to the present invention, it is possible to generate a signal having a very low phase noise in the millimeter wave band, which improves the performance of the millimeter wave wireless communication transceiver, and can be implemented through simplified components, thereby reducing the system cost. .

Hereinafter, a method and apparatus for selecting a photoelectric oscillation mode according to the present invention will be described in detail with reference to the drawings and embodiments.

1 is a block diagram illustrating an apparatus for selecting a photoelectric oscillation mode according to an exemplary embodiment of the present invention. In the present embodiment, the photoelectric oscillation mode selection device largely includes the photoelectric oscillator 100 and the electrical oscillator 200. The photoelectric oscillator 100 includes a laser 110, an electro-optic modulator 120, a first amplifier 130, an optical fiber 140, an optical detector 150, a first coupler 160, and a first filter unit ( 170) and a second amplifier 180. The electrical oscillator 200 includes a second coupler 210, a phase adjuster 220, a third amplifier 230, a second filter 240, and a third coupler 250.

First, each component of the photoelectric oscillator 100 will be described in detail below.

The laser 110 is connected to an electro-optic modulator 120 and injects an optical signal generated by the laser 10 into the electro-optic modulator. The light generated from the laser 110 may be light in the visible region or the invisible region. The electro-optic modulator 120 has an optical input terminal for receiving light from a laser, an input terminal for receiving an RF signal as an electrical control signal, and an output terminal for outputting an optical signal. An electro-optic modulator 120 sends the output terminal an optical signal that is modulated at an oscillation frequency associated with an electrical control signal. There is no particular limitation on the type of the electro-optic modulator 120, for example, a Mach-Zehnder modulator, an electro-absorption modulator may be used. The frequency of the laser is higher than the frequency of the electrical control signal at the RF input terminal of the electro-optic modulator, and the output signal from the electro-optic modulator is a light modulated signal modulated at the frequency of the RF signal. Instead of using both a laser and an electro-optic modulator as in this embodiment, it is also possible to use an all-optical modulated laser.

The first amplifier 130 is an optical amplifying device for amplifying an optical signal from the electro-optic modulator 120. The optical signal amplified by the first amplifier 13 is transmitted to the optical detector 150 through the optical fiber 140. The optical fiber 140 serves as a means of cavity optical delay. The length of the optical fiber 140 is determined in consideration of the quality factor of the all-optical oscillator 100. The longer the fiber, the narrower the bandwidth of the optical signal locked through the cyclic loop of the photoelectric oscillator, but the smaller the frequency distance (FSR) between adjacent modes. The relationship between the length of the optical fiber and the FSR can be expressed according to Equation 1 below.

Equation 1

FSR = c / nL

Where c is the speed of light, n is the reflection coefficient of the optical fiber, and L is the length of the optical fiber.

The photodetector 150 converts an optical signal transmitted through the optical fiber into an electrical signal. The first coupler 160 transmits some electrical signals of the electrical signals from the photo detector 150 to an external device, that is, the second coupler 210 side of the electrical oscillator 200, and the remaining electrical signals are transmitted to the first filter. Transfer to section 170.

The first filter unit 170 passes an electrical signal having a frequency characteristic of a predetermined band from the electrical signal received from the first coupler 160. The narrowing of the passband frequency of the first filter unit 170 has a certain limit, and since it generally has a value larger than the FSR, the signal circulating the photoelectric oscillator is a multi-mode signal. There is no particular limitation on the window characteristics on the frequency domain of the first filter unit. However, considering that the final output signal is a single mode signal, a window having a good pass characteristic with respect to the center frequency and a pass characteristic suppressed as it moves away from the center frequency is preferable. The second amplifier 180 amplifies the electrical signal passing through the first filter unit 170 and transfers the amplified electrical signal to the electro-optic modulator 120.

Hereinafter, each component of the electric oscillator will be described in detail.

The second coupler 210 receives a multi-mode electrical signal output from the first coupler 150 of the photoelectric oscillator 100 and transmits the electrical signal to the phase adjuster 220. Some of the multi-mode signals oscillating through the optical signal transmission path and the electrical signal transmission path included in the photoelectric oscillator 100 are transmitted to the second coupler 210 through the first coupler 150. There is a certain limit to the power value of the signal delivered to the coupler. This is because when the excessive power is supplied to the second coupler, a stable insertion-locking characteristic cannot be obtained. The power P _in of the electrical signal inserted into the electrical oscillator 200 from the photoelectric oscillator 100 and the power P _out of the electrical signal finally output from the electrical oscillator 200 are adjusted to satisfy Equation 2 below. It is desirable to be.

Equation 2

는 전기적 발진기의 발진 주파수이다. 도면1에 도시되지는 않았지만, 감쇄기를 제 1 커플러(160)와 제 2 커플러(210) 사이에 위치시키고, 수학식2의 조건을 만족하도록 감쇄기를 제어하는 것이 바람직하다. 입력 신호의 전력이 상기 수학식을 만족하지 않을 경우, 전기적 발진기를 통해 출력되는 전기적 신호에 부 모드 신호의 전력도 커지기 때문에, 상기 수학식2를 만족시키는 범위에서 입력 신호의 전력을 조절함이 바람직하다.Here, P _in is the power of the electrical signal input to the electrical oscillator, P _out is the power of the electrical signal output from the electrical oscillator, c is the luminous flux, n is the refractive index of the optical fiber, L is the optical fiber Where Q is the quality factor of the second filter,

Is the oscillation frequency of the electrical oscillator. Although not shown in FIG. 1, it is preferable to position the attenuator between the first coupler 160 and the second coupler 210 and to control the attenuator to satisfy the condition of Equation 2. If the power of the input signal does not satisfy the above equation, since the power of the negative mode signal is also increased in the electrical signal output through the electrical oscillator, it is preferable to adjust the power of the input signal within the range satisfying the above equation (2). Do.

The phase adjuster 220 adjusts the phase of the electrical signal from the second coupler 210. When the band pass band of the second filter 240 is determined, the band pass band may be adjusted through phase adjustment of the circulating electrical signal.

The third amplifier 230 receives and amplifies the phase-controlled electrical signal through the phase adjuster 220. The second filter unit 240 may determine a predetermined band from the electrical signal received from the third coupler 230. Pass an electrical signal with frequency characteristics. The third coupler 250 outputs the single mode electrical signal filtered through the second filter unit 240 to the second coupler 210 and the external device.

In particular, in the present embodiment, the electrical oscillator 200 suppresses signals other than a specific mode, in particular a single mode of electrical signals, among the multi-mode signals of the electrical signals generated and inserted in the photoelectric oscillator 100. The locking range or locking frequency range of the single mode electrical signal inserted-locked through the electrical oscillator 200 is provided to follow Equation 3 below.

Equation 3

는 전기적 발진기의 발진 주파수이다.Here, f _LR is a locking range of the electrical oscillator 200, P _in is the power of the electrical signal input to the electrical oscillator, P _out is the power of the electrical signal output from the electrical oscillator Q is a quality factor of the second filter,

Is the oscillation frequency of the electrical oscillator.

The photoelectric oscillation mode selection device of this embodiment is a mode selection device in which the photoelectric oscillator 100 and the electrical oscillator 200 are combined. The optical signal generated by the electro-optic modulator 120 is oscillated through the transmission path of the optical signal and the transmission path of the electrical signal, thereby amplifying signal components belonging to a specific frequency band and suppressing signal components belonging to a stop band. Have However, since the FSR is generally smaller than the mode frequency of the filter, the circulated signal has a multi-mode characteristic (see FIG. 2A). The signal having the characteristic of the multi-mode is inserted into the electrical oscillator in the form of an electrical signal, and the inserted electrical signal is an electrical signal having a single frequency component, i.e., a single signal by repeating the insertion-locking process through a circulating path of the electrical signal. Generates an electrical signal in mode. The photoelectric oscillation mode selection device of this embodiment is distinguished from the conventional insert-locked oscillator, and the mode selection device proposed through this embodiment has a short loop instead of the conventional slave photoelectric oscillator, and is simple and cost effective. It is replaced by an electric oscillator with a setting. In this embodiment, the electrical oscillator has a high passivity (B) bandpass filter (BPF) to select a single mode among the injected OEO modes due to the relatively wide locked range compared to the OEO, due to the relatively wide locking range. Acts as.

In order to support the probability of the above-described structure and grasp the frequency selection characteristic, the following photoelectric oscillation mode selection apparatus can be configured as follows. First, the mode selection device of this embodiment is provided to extract an electrical signal of a single mode from multiple OEO modes having a 84 kHz frequency interval in the 30 GHz band. The SMSR that can be obtained at this time is larger than 113dB. Further, first, the optical fiber 140 of the photoelectric oscillator 100 is 2.4 km in length and is provided to oscillate at 30 GHz. In addition, the second amplifier 180 as an electrical amplifier and the first amplifier 130 as an optical amplifier are provided to compensate for a round trip loss, and the first filter unit 170 has an insertion loss of 6.8 dB. It is set to have a goodness 1500 at 30 GHz. 10% of the electrical signals input to the first coupler 160 are configured to transmit to the second coupler 210. Although not shown in FIG. 1, the power of the inserted signal may be adjusted through a separate attenuator. In the electric oscillator 200, the third amplifier 230, which is an electrical amplifier, has a gain of 18 dB, and the second filter 240, which is an RF filter, has an insertion loss of 3.16 dB and has good quality at 30 GHz. Has 1000. In addition, by using a 4-port 3dB coupler, the second coupler 210 and the third coupler 250 are implemented as one coupler.

2A to 2C are reference diagrams showing the frequency characteristics found under the above-described experimental conditions. In particular, FIG. 2A is a reference diagram illustrating a frequency characteristic of a signal circulating in the photoelectric oscillator 100 in FIG. 1, and FIG. 2B is a reference diagram illustrating a lock frequency characteristic of the electric oscillator 200 in FIG. 1. The locking range represents the band pass width of the electric oscillator having the characteristics of the filter system. In the case of the electric oscillator, a narrow locking range can be obtained even with low injection power, which is advantageous for selecting only a single mode signal. FIG. 2C is a reference diagram illustrating a frequency characteristic of a signal circulating in the electrical oscillator 200 in FIG. 1.

3A to 3C are reference diagrams illustrating a mode selection frequency characteristic according to an oscillation system. The mode select frequency characteristics shown in FIGS. 3A to 3C are attenuated by about 9 dB due to the display limits of the spectrum analyzer, and then measured using a spectrum analyzer (HP8563E) connected to an external device (HP119770A). will be. The spectral span and resolution bandwidth were set to 300 kHz and 300 Hz, respectively.

FIG. 3A illustrates a frequency characteristic of an output signal in an electric oscillation system, and FIG. 3B is a reference diagram illustrating frequency characteristic of an output signal in a photoelectric oscillation system. 3C is a reference diagram illustrating a frequency characteristic of an output signal in the oscillation system of FIG. 1. The power difference between the modes in FIG. 3B depends on the pass band shape of the band pass filter of the photoelectric oscillator.

As shown in FIG. 3C, in the oscillation system in which the photoelectric oscillator and the electrical oscillator of FIG. 1 are combined, even if a multi-mode electrical signal is input to the electrical oscillator, the other modes except the one mode signal are suppressed.

4 is a reference diagram illustrating a measurement result of single-sideband (SSB) phase noise in an electric oscillator and the insertion-locked electric oscillator of FIG. 1. Phase noise measured at 10kHz frequency offset was -97.00dBc / Hz and -112.00dBc / Hz, respectively. The reason for the peak of phase noise at 20 kHz is caused by using a mixer mixer, which is an external device, as one configuration of the measuring device, which is an external device. The phase characteristics of the locked mode around the center frequency are significantly improved by the insert-lock method. As can be seen in Figure 5, according to the system of Figure 1 SMSR value is lower than 113dB.

5 is a reference diagram illustrating a distribution characteristic of power and phase noise of selected modes measured at a 10 kHz frequency offset. In Figure 5 different modes were selected by tuning the phase adjuster. In FIG. 5, the mode having the oscillation frequency component of 30.754892 GHz is O _th Mode, the interval between modes is about 84 kHz, and over 150 selected modes have constant mode power and phase noise values.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will understand that the present invention can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown not in the above description but in the claims, and all differences within the scope should be construed as being included in the present invention.

The apparatus and method for selecting a photoelectric oscillation mode disclosed in the present invention introduces a high-Q filter independent and simple structure of an electric oscillator, which is difficult to implement with conventional electrical methods, in order to select one of several modes of the photoelectric oscillator. By implementing it. In addition, the apparatus and method of the present invention can be implemented through a simplified component compared to the existing technology can reduce the system cost, and because it has a very low phase noise characteristics, millimeter wave band wireless communication system, optical radio Suitable for use in fusion systems.

1 is a block diagram illustrating an apparatus for selecting a photoelectric oscillation mode according to an exemplary embodiment of the present invention.

FIG. 2A shows the frequency characteristic of the signal circulating in the photoelectric oscillator in FIG. 1, FIG. 2B shows the lock frequency characteristic of the electric oscillator, and FIG. 2C shows the frequency characteristic of the signal circulating in the electrical oscillator.

3A shows the frequency characteristic of the output signal in the electrical oscillation system, 3b shows the frequency characteristic of the output signal in the photoelectric oscillation system, and 3c is a reference diagram showing the frequency characteristic of the output signal in the embodiment of FIG.

4 is a reference diagram illustrating a measurement result of SSB phase noise in an electric oscillator and an electric oscillator of FIG. 1.

5 is a reference diagram illustrating power and phase noise distribution characteristics according to selected modes measured at a 10 kHz frequency offset.

Claims (18)

In the photoelectric oscillation mode selection device, A multi-mode signal having a transmission path of an optical signal and a transmission path of an electrical signal, and generating a multi-mode signal belonging to a predetermined frequency band through a cyclic loop structure in which photoelectric conversion is repeated, and being transmitted through the path of the electrical signal. Photoelectric oscillator for outputting at least a part of the electrical signal of the external and And an electrical oscillator having a circular path of an electrical signal and receiving a multi-mode electrical signal output from the photoelectric oscillator and outputting a single mode electrical signal belonging to a predetermined frequency band by insertion-locking. Photoelectric oscillation mode selector. The method of claim 1, wherein the photoelectric oscillator An electro-optical modulator for outputting an electrical signal to an input optical signal; An optical fiber for receiving an optical signal from the electro-optic modulator to generate an optical delayed optical signal; And And a photo detector for outputting an electrical signal to the optical delayed optical signal, wherein the electrical signal output from the photo detector is input back to the electro-optic modulator. The method of claim 2, wherein the photoelectric oscillator Some electrical signals of the electrical signals from the photo detector are output to the electrical oscillator, and the remaining electrical signals have a first coupler for inputting back to the all-optical modulation, and the photoelectric oscillator comprises the electro-optic modulator, the optical fiber. And generating a multi-mode signal through a cyclic loop structure comprising a photo detector and a first coupler. The method of claim 2, wherein the photoelectric oscillator A first amplifier for amplifying an optical signal from the electro-optic modulator; A first filter unit filtering an electric signal belonging to a predetermined frequency band from the remaining electric signals; And Further comprising a second amplifier for amplifying the remaining electrical signal, And the optical fiber receives an optical signal from the first amplifier and generates an optical delayed optical signal. The method of claim 2, The electrical oscillator further includes a second coupler for receiving a multi-mode electrical signal output from the photoelectric oscillator. 6. The oscillator of claim 5, wherein the electrical oscillator A third amplifier configured to amplify the electrical signal from the second coupler; A second filter unit filtering an electric signal of a single mode belonging to a predetermined frequency band from the amplified electric signal; And And a third coupler for outputting an electrical signal of a part of the filtered single mode electrical signal and transmitting the remaining electrical signal to the second coupler. The method of claim 6, The electrical oscillator further comprises a phase adjuster for adjusting the phase of the electrical signal from the second coupler. The method of claim 6, And a lock frequency range of the single mode electrical signal inserted-locked through the electrical oscillator according to the following equation. Equation

Here, f _LR is the lock frequency range of the electrical oscillator, P _in is the power of the electrical signal input to the electrical oscillator, P _out is the power of the electrical signal output from the electrical oscillator, Q is the The quality factor of the second filter,

Is the oscillation frequency of the electrical oscillator. The method of claim 8, The multi-mode electrical signal generated from the photoelectric oscillator is characterized in that the frequency distance (FSR) between the modes adjacent to each other is smaller than the lock frequency range (f _LR ). The method of claim 6, The power of the electrical signal input from the photoelectric oscillator to the electrical oscillator and the power of the electrical signal output from the electrical oscillator satisfy the condition of the following equation. [Equation]

Here, P _in is the power of the electrical signal input to the electrical oscillator, P _out is the power of the electrical signal output from the electrical oscillator, c is the luminous flux, n is the refractive index of the optical fiber, L is the optical fiber Where Q is the quality factor of the second filter,

Is the oscillation frequency of the electrical oscillator. An electro-optic modulator for outputting an optical signal as an optical signal, a first amplifier for amplifying an optical signal from the electro-optic modulator, and an optical signal for receiving an optical signal from the first amplifier and generating an optical delayed optical signal A fiber, an optical detector for outputting an electrical signal to the optical delayed optical signal, a first electrical signal of a part of the electrical signal from the optical detector is output to the outside, and the first electrical signal is input to the all-optical modulation again. A coupler, a first filter unit filtering an electric signal belonging to a predetermined frequency band from the remaining electric signals, and a second amplifier unit amplifying the remaining electric signals, and a predetermined frequency through a cyclic loop structure in which photoelectric conversion is repeated. A photoelectric oscillator for generating a multi-mode signal belonging to the band; And A second coupler receiving a multi-mode electrical signal output from the photoelectric oscillator, a third amplifier for amplifying the electrical signal from the second coupler, and a single mode belonging to a predetermined frequency band in the amplified electrical signal. A second filter unit for filtering an electrical signal, a third coupler configured to output an electrical signal of a portion of the filtered single mode electrical signal and to transmit the remaining electrical signal to the second coupler, the insertion-locking method And an electrical oscillator for outputting an electrical signal of a single mode belonging to a frequency band of the apparatus. In the photoelectric oscillation mode selection method, a) generating a multi-mode signal belonging to a predetermined frequency band through a cyclic loop structure in which an optical signal transmission path, an electrical signal transmission path, and a photoelectric conversion are repeated; b) outputting at least some of the multi-mode electrical signals transmitted through the path of the electrical signals; And and c) receiving the output multi-mode electrical signal and outputting a single mode electrical signal belonging to a predetermined frequency band by insertion-locking. The method of claim 12, Step a) a1) an all-optical modulation step of outputting an optical signal as an input of an electrical signal; a2) receiving the output optical signal and generating a delayed optical signal; a3) a photoelectric modulation step of outputting an electrical signal as an input of the optical delayed optical signal, wherein the steps a1) to a3) are repeated. The method of claim 13, Amplifying the optical signal output in step a1); And And amplifying the electrical signal output in step a3), wherein step a2) receives the amplified optical signal to generate a delayed optical signal. The method of claim 13, Step c) c1) receiving and amplifying the output multi-mode electrical signal; c2) filtering a single mode electrical signal belonging to a predetermined frequency band from the amplified electrical signal; And c3) outputting an electrical signal of a part of the filtered single mode electrical signal. The method of claim 14, The step c) is performed through an electrical oscillator, the step c2) is performed through an electrical filter, and the lock frequency range of the inserted-locked single mode electrical signal is characterized by the following equation. How to choose photoelectric oscillation mode. Equation

Here, f _LR is the lock frequency range of the electrical oscillator, the Pin is the power of the electrical signal input to the electrical oscillator, the P _out is the power of the electrical signal output from the electrical oscillator, the Q is the The quality factor of the filter,

Is the oscillation frequency of the electrical oscillator. The method of claim 16, Step a) is performed through a photoelectric oscillator, wherein the multi-mode electrical signal generated from the photoelectric oscillator has a frequency distance FSR between modes adjacent to each other, which is smaller than the lock frequency range f _LR . Photoelectric oscillation mode selection method. The method of claim 17, The power of the electrical signal input from the photoelectric oscillator to the electrical oscillator, and the power of the electrical signal output from the electrical oscillator satisfy the condition of the following equation. Equation

Here, P _in is the power of the electrical signal input to the electrical oscillator, P _out is the power of the electrical signal output from the electrical oscillator, c is the luminous flux, n is the refractive index of the optical fiber constituting the cyclic loop. Where L is the length of the optical fiber, Q is the quality factor of the filter,

Is the oscillation frequency of the electrical oscillator.

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