KR20220044012A - Optical frequency comb generator and optical integrated circuit for generating optical frequency comb signal - Google Patents

Abstract

According to an embodiment of the present invention, an optical frequency comb generator comprises a light source, an intensity modulator, and a circuit in which a ring resonator is integrated. The light source generates an optical signal, and the intensity modulator modulates the intensity of an optical signal. The ring resonator includes an optical coupler, a phase modulator, an optical splitter, an optical amplifier, a saturable absorber, and a dispersion controller. The optical coupler combines the intensity-modulated optical signal with an optical signal received from a circular path. The phase modulator modulates a phase of the combined optical signal. Also, the optical splitter separates the phase-modulated optical signal into an output path and a circular path. The optical amplifier amplifies the optical signal received from the optical splitter through the circular path. The saturable absorber reduces a pulse width of the optical signal to allow the optical signal passing through the circular path to have microwaves. Also, the dispersion controller compensates for the dispersion of the optical signal passing through the circular path. Therefore, the quality of an optical frequency comb signal is improved.

Description

OPTICAL FREQUENCY COMB GENERATOR AND OPTICAL INTEGRATED CIRCUIT FOR GENERATING OPTICAL FREQUENCY COMB SIGNAL

The present invention relates to an optical frequency comb generator, and more particularly, to an optical frequency comb generator including a ring resonator, and an optical integrated circuit for generating an optical frequency comb signal.

Due to the spread of high-performance computers and smart devices, and the rapid increase in calculation amount and data capacity due to the use of various multimedia, high-speed data processing technology is required in the wired/wireless communication field. In addition, the demand for miniaturization (integration) and low-cost communication module development to which this technology is applied is rapidly increasing.

Optical communication is a communication method that transmits and receives information by loading data signals on light. Optical communication may be performed by converting an electrical signal including transmission information into an optical signal for transmission, and converting a received optical signal into an electrical signal. Optical communication has the advantage of having a wider bandwidth and high-speed communication compared to communication using radio waves.

A system for optical communication requires various components to improve communication quality. Among these components, the development of signal source (light source) technology is required together with the development of data processing technology. Among signal source technologies, multi-wavelength light source technology is an important technology for expanding data capacity. Accordingly, there is a demand for a stable multi-wavelength light source (optical frequency comb generator) with miniaturization and low cost implementation.

The present invention provides an optical frequency comb generator that simplifies, integrates, and miniaturizes components for generating an optical frequency comb signal, improves the quality of the optical frequency comb signal, and reduces power consumption, and an optical frequency comb signal for generating the optical frequency comb signal An integrated circuit may be provided.

An optical frequency comb generator according to an embodiment of the present invention includes a circuit integrated with a light source, an intensity modulator, and a ring resonator. The light source generates an optical signal, and the intensity modulator intensity modulates the optical signal. The ring resonator includes an optical coupler, a phase modulator, an optical splitter, an optical amplifier, a saturable absorber, and a dispersion controller. An optical coupler couples the intensity modulated optical signal to an optical signal received from the circular path. The phase modulator phase modulates the combined optical signal. The optical splitter separates the phase-modulated optical signal into an output path and a cyclic path. The optical amplifier amplifies the optical signal received from the optical splitter through the cyclic path. The saturable absorber reduces the pulse width of the optical signal so that the optical signal passing through the purification path has a microwave. The dispersion controller compensates for the dispersion of the optical signal passing through the circular path.

For example, the light source may output an optical signal having a single wavelength to the intensity modulator.

In one example, the optical frequency comb generator may further include a driving circuit that provides a first control signal to the intensity modulator and a second control signal to the phase modulator. The driving circuit includes a power source for generating an electrical signal, a first amplifier for generating a first control signal by amplifying the electrical signal, a phase shifter for adjusting a phase of the electrical signal, and a second control signal by amplifying the phase-adjusted electrical signal It may include a second amplifier for generating

In one example, the optical frequency comb generator provides a first control signal to the intensity modulator, a driving circuit that provides a second control signal to the phase modulator, and is connected between the intensity modulator and the ring resonator to determine the phase of the intensity modulated optical signal. It may further include a delay line for delaying. The driving circuit may include a power supply generating an electric signal, a first amplifier generating a first control signal by amplifying the electric signal, and a second amplifier generating a second control signal by amplifying the electric signal.

In one example, the optical frequency comb generator may further include a delay line for delaying the phase of the optical signal passing through the circular path. For example, the saturable absorber may include a saturable absorbing material that absorbs an optical signal having an intensity equal to or less than a reference value in an optical signal passing through a circulation path.

In one example, the distributed controller includes a plurality of ports for receiving or transmitting an optical signal passing through the circulation path, a directional coupler for separating a target mode signal from an optical signal received from at least one of the plurality of ports, a directional coupler It may include one or more polarization adjusters for rotating the polarization of the target mode signal separated through it, and one or more optical fiber gratings for reflecting the rotated target mode signal at different times depending on the wavelength.

In one example, the optical fiber grating reflects a first optical signal of a wavelength having a speed greater than or equal to a reference speed later than a second optical signal having a wavelength having a speed less than the reference speed, thereby controlling dispersion of the optical signal; and a second optical fiber grating configured to control dispersion of the optical signal by reflecting the first optical signal faster than the second optical signal.

For example, the phase modulator may be connected between the optical coupler and the optical splitter, and the number of phase modulators may be one.

An optical integrated circuit for generating an optical frequency comb signal according to an embodiment of the present invention includes a waveguide, an intensity modulator, an optical coupler, a phase modulator, an optical splitter, an optical amplifier, a saturable absorber, and a dispersion controller. The waveguide includes a first optical path for receiving an optical signal received from an external light source of the optical integrated circuit, a second optical path for generating an optical frequency comb signal by circulating the optical signal transmitted through the first optical path, and a second optical path and a third optical path for receiving the optical frequency comb signal from the path. The intensity modulator provides a first control signal to a portion of the first optical path to modulate the intensity of the received optical signal. The optical coupler connects the first optical path and the second optical path to combine the optical signal transmitted through the first optical path and the optical signal cycled by the second optical path. The phase modulator provides a second control signal to a portion of the second optical path to modulate the phase of the optical signal coupled by the optical coupler. The optical splitter connects the second optical path and the third optical path to separate the optical frequency comb signal circulating in the second optical path into a third optical path. The optical amplifier amplifies the optical signal circulating in the second optical path. The saturable absorber reduces the pulse width of the optical signal circulating in the second optical path such that the optical signal circulating in the second optical path has microwaves. The dispersion controller compensates for dispersion of the optical signal circulating in the second optical path.

As an example, the optical integrated circuit may further include a delay configured to provide a third control signal to a portion of the second optical path to delay a phase of an optical signal circulating in the second optical path. In one example, the optical integrated circuit may further include a delay configured to provide a third control signal to a portion of the first optical path to delay a phase of the optical signal modulated by the intensity modulator.

In one example, the distributed controller includes a plurality of ports for receiving or transmitting an optical signal circulating in the second optical path, a directional coupler for separating a target mode signal from an optical signal received from at least one of the plurality of ports, a directional It may include one or more polarization regulators for rotating the polarization of the target mode signal separated through the coupler, and one or more optical fiber gratings for reflecting the rotated target mode signal at different times according to wavelengths.

In one example, the optical fiber grating reflects a first optical signal of a wavelength having a speed greater than or equal to a reference speed later than a second optical signal having a wavelength having a speed less than the reference speed, thereby controlling dispersion of the optical signal; and a second optical fiber grating configured to control dispersion of the optical signal by reflecting the first optical signal faster than the second optical signal.

As an example, the optical integrated circuit may further include a driving circuit that generates a first control signal and a second control signal having a modulation frequency.

An optical frequency comb generator according to an embodiment of the present invention includes a light source, an optical integrated circuit, and an optical amplifier. The light source generates an optical signal. The optical integrated circuit receives an optical signal through the waveguide, intensity-modulates the received optical signal, and phase-modulates the intensity-modulated optical signal through a circulation path of the waveguide to generate an optical frequency comb signal. The optical amplifier is connected to the circulation path of the waveguide and amplifies the optical signal passing through the circulation path.

In one example, the optical integrated circuit includes an intensity modulator for intensity-modulating a received optical signal, an optical coupler for coupling the amplified optical signal and the intensity-modulated optical signal, a phase modulator for phase-modulating the combined optical signal, and a phase modulated optical signal. It may include an optical splitter that separates the optical signal into a circular path and an output path for outputting an optical frequency comb signal. As an example, the optical integrated circuit may further include a retarder for delaying the phase of the optical signal passing through the circulation path.

For example, the optical integrated circuit may be provided on a first semiconductor substrate, and the optical amplifier may be provided on a second semiconductor substrate different from the first substrate.

According to an embodiment of the present invention, it is possible to extend the bandwidth of a comb signal using a ring resonator and simplifying components for generating a flattened microwave optical frequency comb signal.

In addition, according to an embodiment of the present invention, by implementing an optical frequency comb generator that generates a flattened microwave signal with an optical integrated circuit integrated in the form of a waveguide, it can be miniaturized.

1 is an exemplary block diagram of an optical frequency comb generator according to an embodiment of the present invention.
2A to 2E are graphs for explaining the improvement effect of the optical frequency comb signal generated by the optical frequency comb generator of FIG. 1 .
3 is an exemplary diagram of the optical frequency comb generator described in FIG. 1 ;
FIG. 4 is an exemplary diagram of the optical frequency comb generator described in FIG. 1 ;
FIG. 5 is an exemplary diagram of the optical frequency comb generator described in FIG. 1 ;
FIG. 6 is an exemplary diagram of the optical frequency comb generator described in FIG. 1 ;
FIG. 7 is an exemplary diagram of the optical frequency comb generator described in FIG. 1 .
FIG. 8 is an exemplary diagram of the optical frequency comb generator described in FIG. 1 ;
9 and 10 are exemplary perspective views of the saturable absorber of FIG. 7 or FIG. 8 .
11-14 are exemplary diagrams of the distributed controller of FIG. 7 or FIG. 8 .

Hereinafter, embodiments of the present invention will be described clearly and in detail to the extent that those skilled in the art can easily practice the present invention.

1 is an exemplary block diagram of an optical frequency comb generator according to an embodiment of the present invention. Referring to FIG. 1 , the optical frequency comb generator 100 includes a light source 110 , an intensity modulator 120 , a ring resonator 130 , and a driving circuit 140 . The optical frequency comb generator 100 according to the embodiment of the present invention will be understood as a configuration for generating an optical frequency comb signal COMB, which is a multi-wavelength optical signal having a flattened spectrum.

The light source 110 outputs an optical signal. The light source 110 may output an optical signal having a single wavelength. The light source 110 may continuously output an optical signal having a predetermined size. For example, the light source 110 may be a continuous wave (CW) laser.

The intensity modulator 120 may modulate the intensity of the optical signal received from the light source 110 . For example, the intensity modulator 120 may modulate an optical signal having a constant output into a sine wave. The intensity modulator 120 may perform intensity modulation of the optical signal based on an electrical signal (eg, a first control signal) provided from the driving circuit 140 . For example, the intensity modulator 120 divides the optical signal into two different optical paths and interferes with the two optical signals modulated under an electric field formed by the first control signal, thereby performing intensity modulation of the optical signal. It may be a gender interferometer.

The ring resonator 130 may modulate the phase of the intensity-modulated optical signal. The ring resonator 130 may provide a cyclic path to repeatedly perform phase modulation. Accordingly, the optical frequency comb generator 100 can be miniaturized and simplified by reducing the number of components for phase modulation of an optical signal. The ring resonator 130 may include an optical coupler 131 , a phase modulator 132 , an optical splitter 133 , an optical amplifier 134 , and a delay line 135 .

The optical coupler 131 may combine the optical signal modulated through the intensity modulator 120 and the optical signal inputted through the circulation path. The optical coupler 131 receives optical signals from a first optical path that transmits an optical signal through the intensity modulator 120 and a second optical path that transmits an optical signal through the optical amplifier 134 and delay line 135 . can receive The optical signals input from the first optical path and the second optical path may be combined by the optical coupler 131 and output to the phase modulator 132 through the third optical path. For example, the optical coupler 131 may be implemented as a Y-branch structure having relatively low wavelength dependence in order to generate an optical frequency comb signal COMB having a broad bandwidth. However, the present invention is not limited thereto, and the optical coupler 131 may be implemented as a directional coupler or a multimode interference (MMI).

The phase modulator 132 may modulate the phase of the optical signal output from the optical coupler 131 through the third optical path. The phase modulator 132 may modulate the optical signal to have a flat-top spectrum through phase modulation. The phase modulator 132 may perform phase modulation of an optical signal based on an electrical signal (eg, a second control signal) provided from the driving circuit 140 . For example, the phase modulator 132 may expand the spectrum of the optical signal by duplicating the optical frequency by the modulation frequency interval of the second control signal by FWM (four wave mixing).

The phase modulator 132 may repeatedly perform phase modulation of the optical signal by using a cyclic path formed through the second optical path and the third optical path. As a result, an optical frequency comb signal COMB having a flattened spectrum by a desired wavelength band may be generated with one phase modulator 132 . Accordingly, the quality of the optical frequency comb signal COMB may be improved, and an additional phase modulator may not be required for the optical frequency comb generator 100 to have a spectrum corresponding to a desired wavelength band. In addition, the phase modulator 132 is connected between the optical coupler 131 and the optical splitter 133 through a third optical path, and the phase modulator 132 is relatively connected from the optical path outputting the optical frequency comb signal COMB. can be made close to

The optical splitter 133 may separate the optical signal modulated through the phase modulator 132 . The optical splitter 133 may be used to output an optical signal circulating in the ring resonator 130 to the outside. The optical splitter 133 may split the phase-modulated optical signal into two and output one as an optical frequency comb signal COMB to the fourth optical path and the other to the second optical path. The fourth optical path may be a path for outputting the optical frequency comb signal COMB to the outside of the optical frequency comb generator 100 for optical communication. For example, the optical splitter 133 may be implemented as a Y-branch, a directional coupler, or a multimode interference (MMI).

The optical amplifier 134 may amplify an optical signal circulated through the second optical path and the third optical path. The intensity of the optical signal may decrease as it travels through the optical path. In particular, when the optical signal is repeatedly cycled through the ring resonator 130 , the intensity of the optical signal may gradually weaken. The optical amplifier 134 may improve the quality of the optical frequency comb signal COMB by amplifying an optical signal having a decreasing intensity through a cyclic path. For example, the optical amplifier 134 may be implemented to amplify an optical signal using an Er+ doped optical fiber such as an Erbium Doped Fiber Amplifier (EDFA), but is not limited thereto, and may be implemented as an optical amplifier using a semiconductor device. there is.

The delay line 135 may delay the phase of the optical signal passing through the second optical path. The delay line 135 may be used to match the phase of the intensity-modulated optical signal through the first optical path and the optical signal circulated through the second optical path. As a result, the optical coupler 131 may couple optical signals having the same phase. For example, the delay line 135 may delay the phase of the optical signal by providing a control signal to a part of the second optical path. Such a control signal may be an electrical signal, and may be provided from the driving circuit 140 .

The driving circuit 140 may control the driving of the optical frequency comb generator 100 to generate the optical frequency comb signal COMB. The driving circuit 140 may generate an electrical signal for driving the optical frequency comb generator 100 . For example, the driving circuit 140 may generate the first control signal so that the intensity modulator 120 modulates the intensity of the optical signal. For example, the driving circuit 140 may generate the second control signal so that the phase modulator 132 modulates the phase of the optical signal. The first control signal and the second control signal may have modulation frequencies for intensity and phase modulation. Furthermore, the driving circuit 140 may further generate a control signal such that the delay line 135 delays the phase of the optical signal.

2A to 2E are graphs for explaining the improvement effect of the optical frequency comb signal generated by the optical frequency comb generator of FIG. 1 . 2A to 2E , the horizontal axis is defined as the wavelength of the optical signal, and the vertical axis is defined as the intensity of the optical signal. For convenience of description, FIGS. 2A to 2E will be described with reference to the reference numerals of FIG. 1 .

FIG. 2A shows a spectrum of an optical signal output when the intensity modulator 120 and the phase modulator 132 are omitted from the optical frequency comb generator 100 of FIG. 1 . Referring to FIG. 2A , as a result of providing only the optical amplifier 134 to the ring resonator 130 , the spectrum of the optical signal through the phase modulator 132 is not expanded. Accordingly, the output optical signal oscillates at a specific wavelength.

FIG. 2B shows a waveform of an optical signal output when the intensity modulator 120 is omitted from the optical frequency comb generator 100 of FIG. 1 . Referring to FIG. 2B , as a result of providing the optical amplifier 134 and the phase modulator 132 to the ring resonator 130 , the spectrum of the optical signal is expanded compared to the spectrum of FIG. 2A . The phase modulator 132 may expand the spectrum of the optical signal through phase modulation of the optical signal. However, the optical signal shown in FIG. 2B is a result of not performing intensity modulation of the optical signal through the intensity modulator 120 . Accordingly, the optical signal of FIG. 2B does not have a flat-top spectrum at regular frequency intervals, like the optical frequency comb signal COMB.

FIG. 2C shows an optical signal output when one intensity modulator 120 and one phase modulator 132 are used without circulation of the optical signal by the ring resonator 130 in the optical frequency comb generator 100 of FIG. 1 . represents the waveform of Referring to FIG. 2C , as a result of simply connecting the intensity modulator 120 and the phase modulator 132 in series, only one phase modulation of the optical signal can be performed. As a result, the spectrum of the optical signal may not be broadened by a sufficiently wide band.

FIG. 2D shows a waveform of an optical signal output when the optical amplifier 134 is omitted from the optical frequency comb generator 100 of FIG. 1 . Referring to FIG. 2D , as a result of providing the phase modulator 132 to the ring resonator 130 , the spectrum of the optical signal is expanded compared to the spectrum of FIG. 2C . As such, the optical signal shown in FIG. 2D is a result of not performing amplification of the optical signal through the optical amplifier 134 . Accordingly, the intensity of the optical signal of FIG. 2D is weakened according to the cycle of the ring resonator 130, and the optical signal having the weakened intensity is combined with the intensity-modulated optical signal, so that the spectrum may not be extended to a sufficiently wide band.

2E shows a waveform of an optical frequency comb signal COMB generated by the optical frequency comb generator 100 according to an embodiment of the present invention. Referring to FIG. 2E , an optical signal is modulated into a sine wave through the intensity modulator 120 , and the intensity-modulated optical signal is repeatedly phase-modulated through the phase modulator 132 of the ring resonator 130 , and a circulating optical signal The intensity of may be iteratively compensated through the optical amplifier 134 of the ring resonator 130 . Accordingly, the optical signal of FIG. 2E may have a spectrum that is extended to a wide band and flattened at regular frequency intervals.

3 is an exemplary diagram of the optical frequency comb generator described in FIG. 1 ; Referring to FIG. 3 , the optical frequency comb generator 200 includes a light source 210 , an intensity modulator 220 , a ring resonator 230 , and a driving circuit 240 , and each configuration is the light source 110 of FIG. 1 . ), the intensity modulator 120 , the ring resonator 130 , and the driving circuit 140 . The ring resonator 230 includes an optical coupler 231 , a phase modulator 232 , an optical splitter 233 , an optical amplifier 234 , and a delay line 235 , each of which includes the optical coupler 131 of FIG. 1 . ), the phase modulator 132 , the optical splitter 133 , the optical amplifier 134 , and the delay line 135 .

Referring to FIG. 3 , the driving circuit 240 includes a power supply 241 , a splitter 242 , a first amplifier 243 , a second amplifier 244 , and a phase shifter 245 . The power source 241 may generate an electrical signal having a modulation frequency of an RF frequency band. For example, the power source 241 may generate an electrical signal having a modulation frequency of 10 GHz or higher. The splitter 242 may distribute the electrical signal generated from the power source 241 to the first amplifier 243 and the second amplifier 244 .

The first amplifier 243 may amplify the electric signal distributed from the splitter 242 and output the amplified electric signal to the intensity modulator 220 . The electric signal amplified by the first amplifier 243 may be the above-described first control signal. The intensity modulator 220 may modulate the intensity of the optical signal based on the first control signal.

The second amplifier 244 may amplify the electric signal distributed from the splitter 242 and output the amplified electric signal to the phase modulator 232 . The electrical signal amplified by the second amplifier 244 may be the above-described second control signal. The phase modulator 232 may modulate the phase of the optical signal based on the second control signal.

The phase shifter 245 may adjust the phase of the electric signal distributed from the splitter 242 to the second amplifier 244 . The phase shifter 245 may be provided to match the phase of the optical signal modulated by the intensity modulator 220 with the phase of the optical signal modulated by the phase modulator 232 through the optical path. By the phase shifter 245 , a phase between the optical signal in the intensity modulator 220 and the first control signal may coincide with a phase between the optical signal in the phase modulator 232 and the second control signal.

FIG. 4 is an exemplary diagram of the optical frequency comb generator described in FIG. 1 ; Referring to FIG. 4 , the optical frequency comb generator 300 includes a light source 310 , an intensity modulator 320 , a ring resonator 330 , and a driving circuit 340 , and each configuration is the light source 110 of FIG. 1 . ), the intensity modulator 120 , the ring resonator 130 , and the driving circuit 140 . The ring resonator 330 includes an optical coupler 331 , a phase modulator 332 , an optical splitter 333 , an optical amplifier 334 , and a second delay line 335 , each of which includes the optical coupler of FIG. 1 . 131 , the phase modulator 132 , the optical splitter 133 , the optical amplifier 134 , and the delay line 135 .

Referring to FIG. 4 , the driving circuit 340 includes a power supply 341 , a splitter 342 , a first amplifier 343 , and a second amplifier 344 . The power supply 341, the splitter 342, the first amplifier 343, and the second amplifier 344 are the power supply 241, the splitter 242, the first amplifier 243, and the second amplifier ( 244). Unlike FIG. 3 , the driving circuit 340 may not include a separate phase shifter. Since an RF electronic component, such as a phase shifter, is not used, a simplified and miniaturized optical frequency comb generator 300 can be implemented.

The optical frequency comb generator 300 may further include a first delay line 325 . The first delay line 325 may be provided to the optical frequency comb generator 300 instead of the phase shifter 245 of FIG. 3 . The first delay line 325 may be provided between the intensity modulator 320 and the ring resonator 330 . The first delay line 325 may delay the phase of the intensity-modulated optical signal. The first delay line 325 is provided to match the phase of the optical signal modulated by the intensity modulator 320 and the phase of the optical signal modulated by the phase modulator 332 like the phase shifter 245 of FIG. 3 . can By the first delay line 325 , the phase between the optical signal at the intensity modulator 320 and the first control signal provided through the first amplifier 343 is determined between the optical signal at the phase modulator 332 and the second It may be the same phase between the second control signals provided through the amplifier 344 .

FIG. 5 is an exemplary diagram of the optical frequency comb generator described in FIG. 1 ; Referring to FIG. 5 , the optical frequency comb generator 400 includes a light source 410 , an intensity modulator 420 , a ring resonator 430 , and a driving circuit 440 , and each of the components corresponds to the components of FIG. 1 . corresponds to The ring resonator 430 includes an optical coupler 431 , a phase modulator 432 , an optical splitter 433 , an optical amplifier 434 , and a delay line 435 , each of which includes the ring resonator 130 of FIG. 1 . ) corresponds to the configurations of The driving circuit 440 includes a power supply 441 , a splitter 442 , a first amplifier 443 , a second amplifier 444 , and a phase shifter 445 , and each configuration is the driving circuit 240 of FIG. 2 . ) corresponds to the configurations of

Referring to FIG. 5 , the ring resonator 430 further includes a saturable absorber 436_1 , a first circulator 436_2 , a distributed controller 437_1 , a second circulator 437_2 , and a second distributed controller 438 . may include As such, the components added to the ring resonator 430 in FIG. 5 may be provided to reduce the pulse width of the optical signal traveling in the circular path (the second optical path in FIG. 1) to generate a femtosecond pulse, and , may be referred to as a pulse width controller.

The saturable absorber 436_1 may reduce a pulse width of an optical signal transmitted through the second optical path. For example, the saturable absorber 436_1 is a reflective saturable absorber and may absorb an optical signal having a relatively weak intensity. An optical signal having a strong intensity remaining after the absorption of the saturable absorber 436_1 is saturated may be reflected. The saturable absorber 436_1 reflects the optical signal having a strong intensity from the optical signal received through the first circulator 436_2, thereby outputting an optical signal with a reduced pulse width to the first circulator 436_2. there is. Through this, the ultra-short pulse may be generated by improving the flatness of the optical signal circulating through the ring resonator 430 . The first circulator 436_2 may output the optical signal received from the saturable absorber 436_1 to the second optical path. However, the present invention is not limited thereto, and the saturable absorber 436_1 may be implanted in the second optical path or disposed on the second optical path without the first circulator 436_2 .

The distributed controller 437_1 may further reduce the pulse width of the optical signal transmitted through the second optical path. The dispersion controller 437_1 may generate an ultrashort pulse by compensating for dispersion or spread of an optical signal circulating through the ring resonator 430 . As an example, the dispersion controller 437_1 may include an optical fiber grating such as chirped fiber bragg grating (CFBG) or a waveguide-type dispersion Bragg grating. The dispersion controller 437_1 may decrease a relatively high wavelength and increase a relatively low wavelength in the optical signal received through the second circulator 437_2 . Also, the distributed controller 437_1 may operate in the opposite direction. The second circulator 437_2 may output the optical signal received from the distributed controller 437_1 to the second optical path.

Like the distributed controller 437_1 , the second distributed controller 438 may also control the dispersion of the optical signal transmitted through the second optical path. For example, the second dispersion controller 438 may compensate for dispersion of an optical signal using a dispersion compensated fiber (DCF) or a single mode fiber (SMF).

FIG. 6 is an exemplary diagram of the optical frequency comb generator described in FIG. 1 ; Referring to FIG. 6 , the optical frequency comb generator 500 includes a light source 510 , an intensity modulator 520 , a ring resonator 530 , and a driving circuit 540 , and each of the components corresponds to the components of FIG. 1 . corresponds to The ring resonator 530 includes an optical coupler 531 , a phase modulator 532 , an optical splitter 533 , an optical amplifier 534 , and a delay line 535 , and each configuration is the ring resonator 130 of FIG. 1 . ) corresponds to the configurations of The driving circuit 540 includes a power supply 541 , a splitter 542 , a first amplifier 543 , a second amplifier 544 , and a phase shifter 545 , and each configuration is the driving circuit 240 of FIG. 2 . ) corresponds to the configurations of

6, the ring resonator 530 includes a saturable absorber 536_1, a first circulator 536_2, a first distributed controller 538_1, a second circulator 537_2, a second distributed controller 537_1, and a third circulator 538_2 may be further included. The ring resonator 530 is an optical signal transmitted to a second optical path through the first distributed controller 538_1 , the second circulator 537_2 , the second distributed controller 537_1 , and the third circulator 538_2 . can control the dispersion of, and these configurations can be referred to as a pulse width controller provided to reduce the pulse width of an optical signal traveling through a circular path (the second optical path in FIG. 1 ) to produce a femtosecond pulse. there is.

For example, the second dispersion controller 537_1 may operate in a direction to generate an anomalous dispersion, and the first dispersion controller 538_1 may operate in a manner to generate a normal dispersion. Alternatively, the second distributed controller 537_1 may operate in a manner that generates a negative chirp, and the first distributed controller 538_1 may operate in a manner that generates a positive chirp. Alternatively, the first and second distributed controllers 538_1 and 537_1 may operate opposite to the previous examples. In addition to FIGS. 5 and 6 , arrangements for distributed control may be provided in the circulation path in various ways.

FIG. 7 is an exemplary diagram of the optical frequency comb generator described in FIG. 1 . Referring to FIG. 7 , the optical frequency comb generator 600 includes a light source 610 , an optical integrated circuit 601 , and an output optical fiber 650 . The light source 610 may generate an optical signal having a single wavelength.

The optical integrated circuit 601 may be a circuit chip in which optical elements and electronic elements are integrated on a semiconductor substrate. The optical integrated circuit 601 may include a waveguide 602 , an intensity modulator 620 , a first retarder 625 , a ring resonator 630 , and a driving circuit 640 . The ring resonator 630 includes an optical coupler 631 , a phase modulator 632 , an optical splitter 633 , an optical amplifier 634 , a second retarder 635 , a saturable absorber 636 , and a dispersion controller 637 ). may include At least some of the first retarder 625 , the saturable absorber 636 , and the dispersion controller 637 may not be included in the optical integrated circuit 601 according to the embodiments described with reference to FIGS. 1 to 6 .

The waveguide 602 may be formed on a semiconductor substrate. The waveguide 602 may generate an optical frequency comb signal by modulating the optical signal received from the light source 610 , and transmit the optical frequency comb signal to the output optical fiber 650 . The waveguide 602 may totally reflect the optical signal and transmit the optical signal based on the total reflection. The waveguide 602 may include the first to fourth optical paths described with reference to FIG. 1 . The first optical path may transmit the optical signal received from the light source 610 to the optical coupler 631 through the intensity modulator 620 and the first delay 625 . The second optical path passes the optical signal received from the optical splitter 633 to the optical coupler 631 through the optical amplifier 634 , the second delay 635 , the saturable absorber 636 , and the dispersion controller 637 . can transmit The third optical path may transmit the optical signal received from the optical coupler 631 to the optical splitter 633 through the phase modulator 632 . The fourth optical path may transmit the optical frequency comb signal received from the optical splitter 633 to the output optical fiber 650 .

The intensity modulator 620 corresponds to the intensity modulator 120 of FIG. 1 . The intensity modulator 620 may be a Mach-Zehnder interferometer including first to third electrodes E11 , E12 , and E13 . For example, the first electrode E11 may receive a first control signal from the driving circuit 640 . The second electrode E12 and the third electrode E13 may be grounded. The phase of each of the two optical signals separated through the first optical path is the electric field between the first electrode E11 and the second electrode E12 and the phase between the first electrode E11 and the third electrode E13. It can be adjusted based on the electric field. In addition, two optical signals whose phases are adjusted according to the modulation frequency of the first control signal may be interfered with. As a result, intensity modulation of the optical signal can be performed.

The phase modulator 632 corresponds to the phase modulator 132 of FIG. 1 . For example, the phase modulator 632 may include first to third electrodes E21 , E22 , and E23 . The first electrode E21 may receive a second control signal from the driving circuit 640 . The second electrode E22 and the third electrode E23 may be grounded. The phase of the optical signal passing through the third optical path may be adjusted based on the electric field between the first electrode E21 and the second electrode E22 . Accordingly, the optical frequency may be duplicated by the modulation frequency interval of the second control signal by FWM (four wave mixing), and the spectrum of the optical signal may be expanded.

The first delay 625 corresponds to the first delay line 325 of FIG. 4 . For example, the first retarder 625 may include first and second electrodes E31 and E32 . Based on the electric field between the first electrode E31 and the second electrode E32 , the phase of the optical signal passing through the first optical path may be adjusted. A voltage for forming an electric field between the first electrode E31 and the second electrode E32 may be provided from the driving circuit 640 . The first delay 625 may be provided to match the phase of the optical signal modulated by the intensity modulator 620 with the phase of the optical signal modulated by the phase modulator 632 . In this case, as described with reference to FIG. 4 , the driving circuit 640 may not include a separate phase shifter.

The second delay 635 corresponds to the delay line 125 of FIG. 1 . For example, the second retarder 635 may include first and second electrodes E41 and E42 . A phase of an optical signal passing through the second optical path may be adjusted based on the electric field between the first electrode E41 and the second electrode E42 . A voltage for forming an electric field between the first electrode E41 and the second electrode E42 may be provided from the driving circuit 640 . The second retarder 635 may be provided to match the phase of the intensity-modulated optical signal through the first optical path and the phase of the optical signal circulated through the second optical path.

The optical amplifier 634 corresponds to the optical amplifier 134 of FIG. 1 . The saturable absorber 636 corresponds to the saturable absorbers 436_1 and 536_1 of FIGS. 5 and 6 . 5 and 6, the saturable absorber 636 may reduce the pulse width of the optical signal without using a separate circulator, and an exemplary structure of the saturable absorber 636 will be described later 9 and 10 may be the same. The distributed controller 637 corresponds to the distributed controllers 437_1, 438, 537_1, and 538_1 of FIGS. 5 and 6 . An exemplary structure of the distributed controller 637 may be as shown in FIGS. 11 to 13 to be described later.

FIG. 8 is an exemplary diagram of the optical frequency comb generator described in FIG. 1 ; Referring to FIG. 8 , the optical frequency comb generator 700 may include a light source 710 , an optical integrated circuit 701 , and an output optical fiber 750 , each configuration of which is the optical frequency comb generator of FIG. 7 ( 600). The optical integrated circuit 701 may include a waveguide 702 , an intensity modulator 720 , a first retarder 725 , a ring resonator 730 , and a driving circuit 740 , each of which is illustrated in FIG. 7 . It corresponds to the configurations of the optical integrated circuit 601 .

The ring resonator 730 includes an optical coupler 731 , a phase modulator 732 , an optical splitter 733 , an optical amplifier 734 , a second retarder 735 , a saturable absorber 736 , and a dispersion controller 737 . may include Unlike FIG. 7 , the optical amplifier 734 is not integrated in the optical integrated circuit 701 , but may be provided outside the optical integrated circuit 701 . For example, the semiconductor substrate on which the optical integrated circuit 701 is integrated and the semiconductor substrate on which the optical amplifier 734 is provided may be different from each other. In order to increase the optical amplification efficiency, a certain size may be required for the optical amplifier 734 , and accordingly, the optical amplifier 734 may be provided outside the optical integrated circuit 701 . For example, the optical amplifier 734 may be implemented using an Er+-doped optical fiber such as an Erbium Doped Fiber Amplifier (EDFA).

9 is an exemplary perspective view of the saturable absorber of FIG. 7 or FIG. 8 ; Referring to FIG. 9 , the saturable absorber 736_1 may be formed in the waveguide core 702 surrounded by the cladding CL. The saturable absorber 736_1 may include a saturable absorption material (IMP) implanted in a partial region of the waveguide core 702 , that is, a partial region of the second optical path. A saturable absorbing material (IMP) may be provided to the waveguide 702 by doping for free carrier absorption or forming defects for absorption and non-radiative recombination. An optical signal having a relatively weak intensity may be absorbed in the optical signal traveling through the saturable absorption material IMP in the second optical path. For example, the saturable absorbing material (IMP) may absorb an optical signal having an intensity equal to or less than a reference value. As a result, the pulse width of the optical signal is reduced, so that microwaves can be generated.

10 is an exemplary perspective view of the saturable absorber of FIG. 7 or FIG. 8 ; Referring to FIG. 10 , the saturable absorber 736_2 may be formed on the waveguide core 702 . The saturable absorber 736_2 may include a saturable absorber AM formed in a portion of the clad CL around the waveguide core 702 . A saturated absorbing material (AM) may be selectively grown on the waveguide core 702 . For example, the saturated absorbing material AM may include a group III-V compound semiconductor. In an optical signal traveling through the saturable absorption material AM, the optical signal having a relatively weak intensity may be absorbed. For example, the saturable absorption material AM may absorb an optical signal having an intensity equal to or less than a reference value. As a result, the pulse width of the optical signal is reduced, so that microwaves can be generated.

11 is an exemplary diagram of the distributed controller of FIG. 7 or FIG. 8 . Referring to FIG. 11 , the dispersion controller 737_1 may include a directional coupler (DC) using a waveguide 702, a polarization controller (PS), and a waveguide-type grating such as a chirped bragg grating (CBG). . The distributed controller 737_1 may receive or transmit an optical signal through the first to fourth ports P1 , P2 , P3 , and P4 .

The directional coupler DC may separate optical signals of different modes. For example, the directional coupler DC may be formed using a LiNbO3 X-cut waveguide. For example, the distributed controller 737_1 may transmit a TE (Transverse Electric) mode signal received through the first port P1 to the third port P3 through the directional coupler DC. The polarization controller PS may rotate the polarization of the TE mode signal traveling to the third port P3 by 45 degrees. To this end, the polarization controller PS may include electrodes that form an electric field, and an electric signal for forming an electric field may be provided from the driving circuits 640 and 740 of FIG. 7 or 8 .

The 45 degree-rotated optical signal may be reflected through the waveguide-type dispersion Bragg grating CBG connected to the third port P3 . A waveguide-type dispersed Bragg grating (CBG) may reflect an optical signal at different times for each wavelength. For example, the waveguide-type dispersion Bragg grating (CBG) may control dispersion of an optical signal by slowing an optical signal having a high speed and quickly reflecting an optical signal having a low speed. A pulse width of the optical signal reflected from the waveguide dispersion Bragg grating CBG may be smaller than a pulse width of the optical signal incident to the waveguide dispersion Bragg grating CBG.

The optical signal reflected from the waveguide dispersion Bragg grating CBG may be further rotated by 45 degrees through the polarization controller PS, and as a result, a TM (Transverse Magnetic) mode signal may be output. The TM mode signal may be transmitted to the second port P2 through the directional coupler DC. The optical signal transmitted to the second port P2 may travel through the second optical path.

12 is an exemplary diagram of the distributed controller of FIG. 7 or FIG. 8 . Referring to FIG. 12 , the dispersion controller 737_2 includes a directional coupler DC using a waveguide 702, a first polarization controller PS1, a second polarization controller PS2, and a waveguide-type dispersion Bragg grating CBG. may include The distributed controller 737_2 may receive or transmit an optical signal through the first to fourth ports P1, P2, P3, and P4.

For example, the distributed controller 737_2 may transmit the TE mode signal received through the first port P1 to the third port P3 through the directional coupler DC. The first polarization controller PS1 may rotate the polarization of the TE mode signal traveling to the third port P3 by 45 degrees. The 45 degree-rotated optical signal may be reflected through the waveguide-type dispersion Bragg grating CBG connected to the third port P3 . The waveguide-type dispersion Bragg grating CBG may control dispersion of an optical signal input through the third port P3 . The waveguide-type dispersion Bragg grating (CBG) may control dispersion of an optical signal by slowing an optical signal having a high speed and quickly reflecting an optical signal having a low speed. The optical signal reflected from the waveguide-type dispersion Bragg grating CBG may be further rotated by 45 degrees through the first polarization adjuster PS1, and as a result, a TM mode signal may be output. The TM mode signal may proceed to the second port P2 through the directional coupler DC.

The polarization of the TM mode signal traveling to the second port P2 may be rotated by 90 degrees through the second polarization controller PS2. As a result, the TM mode signal may be converted into a TE mode signal and transmitted to the second port P2. The optical signal transmitted to the second port P2 may travel through the second optical path.

13 is an exemplary diagram of the distributed controller of FIG. 7 or FIG. 8 . Referring to FIG. 13 , the dispersion controller 737_3 includes a directional coupler DC using the waveguide 702, a first polarization controller PS1, a second polarization controller PS2, and a waveguide-type dispersion Bragg grating CBG. may include The distributed controller 737_2 may receive or transmit an optical signal through the first to fourth ports P1, P2, P3, and P4.

For example, the distributed controller 737_3 may transmit the TE mode signal received through the first port P1 to the third port P3 through the directional coupler DC. The first polarization controller PS1 may rotate the polarization of the TE mode signal traveling to the third port P3 by 45 degrees. The 45 degree-rotated optical signal may be reflected through the waveguide-type dispersion Bragg grating CBG connected to the third port P3 . The waveguide-type dispersion Bragg grating CBG may control dispersion of an optical signal input through the third port P3 . Unlike FIG. 12 , the waveguide-type dispersion Bragg grating (CBG) may control dispersion of an optical signal by reflecting an optical signal of a slow wavelength slowly and rapidly reflecting an optical signal having a high speed. The optical signal reflected from the waveguide-type dispersion Bragg grating CBG may be further rotated by 45 degrees through the first polarization adjuster PS1, and as a result, a TM mode signal may be output. The TM mode signal may proceed to the second port P2 through the directional coupler DC.

The polarization of the TM mode signal traveling to the second port P2 may be rotated by 90 degrees through the second polarization controller PS2. As a result, the TM mode signal may be converted into a TE mode signal and transmitted to the second port P2. The optical signal transmitted to the second port P2 may travel through the second optical path.

Each of the integrated distributed controllers 737_2 and 737_3 shown in FIGS. 12 and 13 may correspond to the first distributed controller 538_1 and the second distributed controller 537_1 of FIG. 6 . For example, the second distributed controller 537_1 of FIG. 6 may be implemented as the distributed controller 727_3 of FIG. 13 and may intentionally extend the pulse width by generating dispersion in the input pulse. The optical signal with the extended pulse width may be amplified by the optical amplifier 534 of FIG. 6 . The first distributed controller 538_1 of FIG. 6 is implemented as the distributed controller 727_2 of FIG. 12 , and may reduce the pulse width by generating dispersion in the input pulse. Through this process, ultra-short pulses can be generated.

14 is an exemplary diagram of the distributed controller of FIG. 7 or FIG. 8 . Referring to FIG. 14 , the dispersion controller 737_4 includes a directional coupler DC using a waveguide 702, a first polarization controller PS1, a second polarization controller PS2, and a first waveguide-type dispersion Bragg grating CBG1. , and a second waveguide-type distributed Bragg grating CBG2 . The distributed controller 737_4 may receive or transmit an optical signal through the first to fourth ports P1, P2, P3, and P4.

For example, the distributed controller 737_4 may transmit the TE mode signal received through the first port P1 to the third port P3 through the directional coupler DC. The first polarization controller PS1 may rotate the polarization of the TE mode signal traveling to the third port P3 by 45 degrees. The 45 degree-rotated optical signal may be reflected through the first waveguide-type dispersion Bragg grating CBG1 connected to the third port P3 . The first waveguide-type dispersion Bragg grating CBG1 may control dispersion of an optical signal input through the third port P3 . The optical signal reflected from the first waveguide-type dispersion Bragg grating CBG1 may be further rotated by 45 degrees through the first polarization controller PS1, and as a result, a TM mode signal may be output.

The TM mode signal may travel to the second port P2 through the directional coupler DC. The polarization of the TM mode signal traveling to the second port P2 is rotated by 45 degrees through the second polarization controller PS2. can be The 45 degree-rotated optical signal may be reflected through the second waveguide-type dispersion Bragg grating CBG2 connected to the second port P2 . The second waveguide-type dispersion Bragg grating CBG2 may control dispersion of an optical signal input through the second port P2 . The optical signal reflected from the second waveguide-type dispersion Bragg grating CBG2 may be further rotated by 45 degrees through the second polarization controller PS2. As a result, the TE mode signal may be output to the directional coupler DC. The directional coupler DC may output the TE mode signal to the fourth port P4 . The optical signal transmitted to the fourth port P4 may travel through the second optical path.

The dispersion of the first waveguide-type dispersion Bragg grating CBG1 and the second waveguide-type dispersion Bragg grating CBG2 may be arranged to be opposite to each other. For example, when an arbitrary pulse generated by the optical frequency comb generating device passes through the first waveguide-type dispersion Bragg grating CBG1, dispersion further increases to increase the pulse width. Thereafter, the pulse width is reduced by using the second waveguide-type distributed Bragg grating CBG2 to cancel the dispersion generated by the first waveguide-type distributed Bragg grating CBG1. By repeating this process in the ring resonator, microwave pulses are generated to generate a flattened optical frequency comb signal.

The contents described above are specific examples for carrying out the present invention. The present invention will include not only the above-described embodiments, but also simple design changes or easily changeable embodiments. In addition, the present invention will include techniques that can be easily modified and implemented in the future using the above-described embodiments.

100, 200, 300, 400, 500, 600, 700: Optical Frequency Comb Generator
110, 210, 310, 410, 510, 610, 710: light source
120, 220, 320, 420, 520, 620, 720: intensity modulator
130, 230, 330, 430, 530, 630, 730: ring resonator
131, 231, 331, 431, 531, 631, 731: Optocouplers
132, 232, 332, 432, 532, 632, 732: Phase modulator
133, 233, 333, 433, 533, 633, 733: optical splitter
134, 234, 334, 434, 534, 634, 734: optical amplifier
135, 235, 325, 335, 435, 535, 625, 635, 725, 735: delay line (delayer)
140, 240, 340, 440, 540, 640, 740: driving circuit
436_1, 536_1, 636, 736, 736_1, 736_2: saturated absorber
437_1, 438, 537_1, 538_1. 637, 737, 737_1, 737_2, 737_3, 737_4: distributed controller
601, 701: optical integrated circuit
602, 702: waveguide

Claims (20)

a light source for generating an optical signal;
an intensity modulator for intensity-modulating the optical signal; and
and a circuit integrated with a ring resonator for generating an optical frequency comb signal by phase-modulating the intensity-modulated optical signal through a cyclic path and outputting the optical frequency comb signal to an output path;
The ring resonator is
an optical coupler coupling the intensity modulated optical signal to an optical signal received from the circular path;
a phase modulator for phase-modulating the combined optical signal;
an optical splitter dividing the phase-modulated optical signal into the output path and the circulation path;
an optical amplifier for amplifying an optical signal passing through the circulation path;
a saturable absorber for reducing a pulse width of the optical signal passing through the circulation path so that the optical signal passing through the circulation path has a microwave; and
and a dispersion controller for compensating for dispersion of the optical signal passing through the circular path. According to claim 1,
The light source is an optical frequency comb generator that outputs the optical signal having a single wavelength to the intensity modulator. According to claim 1,
a driving circuit that provides a first control signal to the intensity modulator and a second control signal to the phase modulator;
The driving circuit is
a power source that generates an electrical signal;
a first amplifier for amplifying the electrical signal to generate the first control signal;
a phase shifter for adjusting the phase of the electrical signal; and
and a second amplifier configured to amplify the phase-adjusted electrical signal to generate the second control signal. According to claim 1,
a driving circuit providing a first control signal to the intensity modulator and a second control signal to the phase modulator; and
Further comprising a delay line connected between the intensity modulator and the ring resonator to delay the phase of the intensity-modulated optical signal,
The driving circuit is
a power source that generates an electrical signal;
a first amplifier for amplifying the electrical signal to generate the first control signal; and
and a second amplifier configured to amplify the electrical signal to generate the second control signal. According to claim 1,
and a delay line for delaying the phase of the optical signal passing through the circular path. According to claim 1,
The saturated absorber is
and a saturable absorbing material for absorbing an optical signal having an intensity less than or equal to a reference value in the optical signal passing through the circulation path. According to claim 1,
The distributed controller is
a plurality of ports for receiving or transmitting the optical signal passing through the circular path;
a directional coupler for separating a target mode signal from the optical signal received from at least one of the plurality of ports;
one or more polarization controllers for rotating the polarization of the target mode signal separated through the directional coupler; and
and one or more optical fiber gratings for reflecting the rotated target mode signal at different times according to wavelength. 8. The method of claim 7,
The optical fiber grating is
a first optical fiber grating configured to control dispersion of the optical signal by reflecting a first optical signal of a wavelength having a speed greater than or equal to a reference speed later than a second optical signal having a wavelength having a speed less than the reference speed; and
and at least one of a second optical fiber grating configured to control dispersion of the optical signal by reflecting the first optical signal faster than the second optical signal. According to claim 1,
The phase modulator is connected between the optical coupler and the optical splitter, and the number of the phase modulators is one. An optical integrated circuit for generating an optical frequency comb signal, comprising:
a first optical path for receiving an optical signal received from an external light source of the optical integrated circuit, a second optical path for generating the optical frequency comb signal by circulating the optical signal transmitted through the first optical path, and the second optical path a waveguide having a third optical path for receiving the optical frequency comb signal from the second optical path;
an intensity modulator providing a first control signal to a portion of the first optical path to modulate an intensity of the received optical signal;
an optical coupler connecting the first optical path and the second optical path to combine the optical signal transmitted through the first optical path and the optical signal circulated by the second optical path;
a phase modulator providing a second control signal to a portion of the second optical path to modulate a phase of the optical signal coupled by the optical coupler;
an optical splitter connecting the second optical path and the third optical path to separate the optical frequency comb signal circulating in the second optical path into the third optical path;
an optical amplifier amplifying the optical signal circulating in the second optical path;
a saturable absorber for reducing a pulse width of the optical signal circulating in the second optical path so that the optical signal circulating in the second optical path has a microwave; and
and a dispersion controller for compensating for dispersion of the optical signal circulating in the second optical path. 11. The method of claim 10,
and a delayer providing a third control signal to a portion of the second optical path to delay a phase of the optical signal circulating in the second optical path. 11. The method of claim 10,
and a delayer providing a third control signal to a portion of the first optical path to delay a phase of the optical signal modulated by the intensity modulator. 11. The method of claim 10,
The saturated absorber is
an optical integrated circuit inserted into or disposed on a portion of the second optical path. 11. The method of claim 10,
The saturated absorber is
and a saturable absorbing material for absorbing an optical signal having an intensity less than or equal to a reference value in the optical signal passing through the second optical path. 11. The method of claim 10,
The distributed controller is
a plurality of ports for receiving or transmitting the optical signal circulating in the second optical path;
a directional coupler for separating a target mode signal from the optical signal received from at least one of the plurality of ports;
one or more polarization controllers for rotating the polarization of the target mode signal separated through the directional coupler; and
and one or more optical fiber gratings for reflecting the rotated target mode signal at different times depending on wavelength. 16. The method of claim 15,
The optical fiber grating is
a first optical fiber grating configured to control dispersion of the optical signal by reflecting a first optical signal of a wavelength having a speed greater than or equal to a reference speed later than a second optical signal having a wavelength having a speed less than the reference speed; and
and at least one of a second optical fiber grating configured to control dispersion of the optical signal by reflecting the first optical signal faster than the second optical signal. 11. The method of claim 10,
The optical integrated circuit further comprising a driving circuit that generates the first control signal and the second control signal having a modulation frequency. a light source for generating an optical signal;
an optical integrated circuit for receiving the optical signal through a waveguide, intensity-modulating the received optical signal, and phase-modulating the intensity-modulated optical signal through a circulation path of the waveguide to generate an optical frequency comb signal; and
and an optical amplifier coupled to the circular path of the waveguide and configured to amplify an optical signal passing through the circular path. 19. The method of claim 18,
The optical integrated circuit comprises:
an intensity modulator for intensity-modulating the received optical signal;
an optical coupler for coupling the amplified optical signal and the intensity-modulated optical signal;
a phase modulator for phase-modulating the combined optical signal; and
and an optical splitter dividing the phase-modulated optical signal into the cyclic path and an output path for outputting the optical frequency comb signal. 19. The method of claim 18,
wherein the optical integrated circuit is provided on a first semiconductor substrate, and the optical amplifier is provided on a second semiconductor substrate different from the first substrate.

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