KR20200032623A - Apparatus and method for optical modulating - Google Patents

Abstract

Disclosed are an optical modulation device and a method thereof. The optical modulation device includes: a bus-type optical waveguide through which an optical signal is transmitted and received; and a ring-type optical waveguide optically modulating the optical signal output through the bus-type optical waveguide in accordance with an electrical signal. The optical signal is input to the ring-type optical waveguide through an input end of the bus-type optical waveguide, and is primarily optical-modulated. After the optical signal is reflected through a reflector disposed at the output end of the bus-type optical waveguide, the optical signal is re-inputted into the ring-type optical waveguide, is secondarily optical-modulated, and then may be outputted through the bus-type optical waveguide.

Description

Light modulation device and method {APPARATUS AND METHOD FOR OPTICAL MODULATING}

The present invention relates to an optical modulation device and method, and more particularly, to a silicon-based optical modulation device and method including a reflector (Reflector).

Currently, as photonic transceivers rapidly increase in demand, silicon photonics technology is drawing attention. Silicon photonics is the core of a silicon-based optical modulation device that performs an electro-optic conversion function among a plurality of optical elements constituting an optical circuit.

The silicon-based optical modulation device is divided into a Mark-Zehnder Modulator (MZM), a Michelson Interferometric Modulator (MIM), and a Micro Ring Modulator (MRM). . In particular, the micro-ring type optical modulator of the resonance structure has the advantage of providing the lowest power consumption, the smallest size in micro units, and high modulation efficiency.

Therefore, in recent years, there is an increasing demand for a manufacturing method for improving the bandwidth and optical modulation efficiency of such a micro-ring type optical modulator.

The present invention primarily modulates the optical signal through the ring-shaped optical waveguide constituting the optical modulation device, and performs secondary optical modulation on the primary optically modulated optical signal reflected by the reflector disposed at the output terminal of the bus-type optical waveguide. Can provide a method.

An optical modulation device according to an embodiment of the present invention includes a bus-type optical waveguide through which optical signals are transmitted and received; And a ring-type optical waveguide for optically modulating the optical signal output through the bus-type optical waveguide according to an electrical signal, wherein the optical signal is input to the ring-type optical waveguide through an input terminal of the bus-type optical waveguide and primary optical modulation is performed. It may be reflected through a reflector disposed at the output end of the bus-type optical waveguide, re-entered into the ring-type optical waveguide, and secondary-modulated, and then output through the bus-type optical waveguide.

The distance between the ring-shaped optical waveguide and the reflector may be related to a time period for 1 bit of the electrical signal.

The upper reflector may be either a loop mirror or a Bragg grating.

An optical modulator according to an embodiment of the present invention is a power coupler for dividing an optical signal into a first optical signal and a second optical signal and transmitting them to input terminals of optical waveguides arranged along the first path and the second path ( Power coupler); And a phase shifter disposed on each of the optical waveguides disposed along the first path and the second path to modulate the phase of at least one of the first optical signal and the second optical signal through an electrical signal. Including, the optical signal is branched into a first optical signal and a second optical signal through the power coupler is primary phase modulated through a phase shifter disposed in the first path and the second path, the output terminal of the optical waveguides It is reflected through a reflector disposed in the re-input to the phase shifter may be secondary phase modulated and then output through the power coupler.

The phase shifter may be implemented as a ring-type optical waveguide.

The phase shifter disposed along the first path and the second path may modulate the phase of at least one of the first optical signal and the second optical signal through a differential electrical signal.

The distance between the phase shifter and the reflector may be related to a time period for 1 bit of the electrical signal.

The upper reflector may be either a loop mirror or a Bragg grating.

An optical modulation method according to an embodiment of the present invention includes receiving an optical signal through an input terminal of a bus-type optical waveguide; And optically modulating the optical signal received through the ring-shaped optical waveguide to the input terminal of the bus-type optical waveguide according to an electrical signal, wherein the optical-modulating step is primarily optically modulated through the ring-shaped optical waveguide to the bus. Secondary light modulation may be performed on the reflected light signal through a reflector disposed at an output terminal of the fluorescent waveguide.

The distance between the ring-shaped optical waveguide and the reflector may be related to a time period for 1 bit of the electrical signal.

The upper reflector may be either a loop mirror or a Bragg grating.

In the optical modulation method according to an embodiment of the present invention, an optical signal is split into a first optical signal and a second optical signal through a power coupler, and the divided first optical signal and the second optical signal are removed. Transmitting optical waveguides arranged along the first path and the second path to input terminals, respectively; And modulating a phase of at least one of the first optical signal and the second optical signal through a phase shifter disposed along the first path and the second path, and modulating the phase. The step may be primary phase modulated through the phase shifter to perform secondary phase modulation of the first optical signal and the second optical signal reflected through the reflector disposed at each output end of the optical waveguides.

The phase shifter may be implemented as a ring-type optical waveguide.

The phase shifter disposed along the first path and the second path may modulate the phase of at least one of the first optical signal and the second optical signal through a differential electrical signal.

The distance between the phase shifter and the reflector may be related to a time period for 1 bit of the electrical signal.

The upper reflector may be either a loop mirror or a Bragg grating.

According to an embodiment of the present invention, the optical signal is primarily optically modulated through the ring-shaped optical waveguide constituting the optical modulation device, and the primary optically modulated optical signal reflected by the reflector disposed at the output terminal of the bus-type optical waveguide By modulating the secondary light, the bandwidth and the optical modulation efficiency of the optical modulation device can be improved.

1 is a view showing the structure and characteristics of a ring-type optical modulator.
FIG. 2 is a diagram showing the structure and characteristics of an optical modulation device in which a ring-type optical modulator is connected in series.
3 is a view showing a first structure of an optical modulation device according to an embodiment of the present invention.
4 is a view showing a second structure of an optical modulation device according to an embodiment of the present invention.
5 is a diagram illustrating a third structure of an optical modulation device according to an embodiment of the present invention.
6 is a diagram illustrating a fourth structure of an optical modulation device according to an embodiment of the present invention.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, various changes may be made to the embodiments, and the scope of the patent application right is not limited or limited by these embodiments. It should be understood that all modifications, equivalents, or substitutes for the embodiments are included in the scope of rights.

The terms used in the examples are for illustrative purposes only and should not be construed as limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “include” or “have” are intended to indicate that a feature, number, step, operation, component, part, or combination thereof described on the specification exists, and that one or more other features are present. It should be understood that the existence or addition possibilities of fields or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person skilled in the art to which the embodiment belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having meanings consistent with meanings in the context of related technologies, and should not be interpreted as ideal or excessively formal meanings unless explicitly defined in the present application. Does not.

In addition, in the description with reference to the accompanying drawings, the same reference numerals are assigned to the same components regardless of reference numerals, and redundant descriptions thereof will be omitted. In describing the embodiments, when it is determined that detailed descriptions of related known technologies may unnecessarily obscure the subject matter of the embodiments, detailed descriptions thereof will be omitted.

1 is a view showing the structure and characteristics of a ring-type optical modulator.

Referring to (a) of FIG. 1, the ring-shaped optical modulator 100 having a resonance structure may include a bus-shaped optical waveguide 110 and a ring-shaped optical waveguide 120 made of silicon. At this time, the ring-shaped optical waveguide 120 may perform a phase shifter (PS) function. Specifically, when a voltage is applied to the ring-shaped optical waveguide 120 from the outside, the refractive index of the phase shifter may be changed and the pass spectrum of the ring-shaped optical modulator 100 may be changed.

As an example, FIG. 1 (b) is a graph schematically illustrating the pass spectrum of the ring-shaped optical modulator 100 when the first voltage is applied to the ring-shaped optical waveguide 120 from the outside and when the second voltage is applied. . That is, when a first voltage is applied to the ring-shaped optical waveguide 120 and an external optical signal is input to a specific frequency of the ring-shaped optical modulator 100, the external optical signal may be output after experiencing a large insertion loss. At this time, the ring-type optical modulator 100 may be in an OFF state.

Unlike this, when the second voltage is applied to the ring-shaped optical waveguide 120 from the outside, the refractive index of the ring-shaped optical modulator 100 may be changed to shift the pass spectrum. That is, when a second voltage is applied to the ring-shaped optical waveguide 120 and an external optical signal is input to a specific frequency of the ring-shaped optical modulator 100, the external optical signal may be output through a small insertion loss. At this time, the ring-type optical modulator 100 may be in an ON state.

As described above, the optical power of the optical signal output through the ring-shaped optical modulator 100 may vary according to the voltage applied to the ring-shaped optical waveguide 120. At this time, the optical power difference of the optical signal output through the ring-type optical modulator 100 may be defined as an extinction ratio (ER), and the larger the extinction ratio, the higher the optical modulation efficiency may be.

)은 하기의 식 1과 같이 정의될 수 있다.Meanwhile, in order for the ring-type optical modulator 100 to transmit an optical signal at a high speed, it must have a high 3-dB electro-optic conversion bandwidth. 3-dB all-optical conversion bandwidth of ring type optical modulator 100 (

) May be defined as in Equation 1 below.

<Equation 1>

)과 전기 신호를 인가하기 위한 전기적 대역폭(

)으로 결정될 수 있다. 여기서, 광학적 대역폭(

)은 도 1의 (b)에서 기준선(Reference 0 dB)으로부터 3-dB 만큼 떨어진 지점의 통과 스펙트럼 폭으로 정의될 수 있다.Referring to Equation 1, the 3-dB all-optical conversion bandwidth of the ring-shaped optical modulator 100 is the optical bandwidth of the ring-shaped optical modulator 100 (

) And electrical bandwidth for applying electrical signals (

). Where optical bandwidth (

) May be defined as a pass spectrum width at a point 3 dB away from the reference line (Reference 0 dB) in FIG.

)은 좁지만 같은 전압을 걸어 주었을 때, 더 높은 소광비를 확보할 수 있는 장점이 있다. 반대로 낮은 Q-factor를 갖는 링형 광 변조기(100)는 광학적 대역폭(

)이 넓어서 광 신호를 고속으로 전송 가능하지만 소광비가 낮아지는 문제점이 있다.When compared with FIG. 1 (c), FIG. 1 (b) shows that the pass spectrum of the ring-shaped optical modulator 100 having a high Q-factor has a steep pass spectrum. The ring type optical modulator 100 having such a high Q-factor has an optical bandwidth (

) Is narrow, but has the advantage of ensuring a higher extinction ratio when the same voltage is applied. Conversely, the ring-shaped optical modulator 100 having a low Q-factor has an optical bandwidth (

) Is wide, so it is possible to transmit optical signals at high speed, but there is a problem that the extinction ratio is lowered.

FIG. 2 is a diagram showing the structure and characteristics of an optical modulation device in which a ring-type optical modulator is connected in series.

)과 소광비의 트레이드 오프(Trade-off) 관계를 극복하기 위해 두 개의 낮은 Q-factor를 갖는 링형 광 변조기를 직렬 연결하는 구조의 광 변조 장치가 제안되었다. 하나의 낮은 Q-factor를 갖는 링형 광 변조기는 광학적 대역폭(

)이 넓고 소광비가 낮지만, 두 개의 낮은 Q-factor를 갖는 링형 광 변조기를 직렬 연결하면 넓은 광학적 대역폭(

)을 그대로 유지하면서 외부에서 입력된 광 신호가 직렬로 연결된 두 개의 링형 광 변조기를 통과하기 때문에 소광비를 증가시킬 수 있다.Referring to Figure 2, the optical bandwidth of the ring-shaped optical modulator (

) To overcome the trade-off relationship between extinction ratio and extinction ratio, an optical modulation device having a structure in which two low Q-factor ring type optical modulators are connected in series has been proposed. Ring-type optical modulator with one low Q-factor has an optical bandwidth (

) Is wide and the extinction ratio is low, but a series of two low Q-factor ring-type optical modulators in series provides a wide optical bandwidth (

), While the externally input optical signal passes through two ring-shaped optical modulators connected in series, the extinction ratio can be increased.

In general, silicon-based ring type optical modulators can be represented as capacitors in electrical circuit modeling. That is, in the structure as shown in FIG. 2, since the two ring-shaped optical modulators modeled as capacitors are connected in parallel at the input terminal of the electrical signal, the overall capacitance of the ring-shaped optical modulator increases.

)을 감소시켜 결국 링형 광 변조기의 전광 대역폭(

)이 감소되는 문제점이 발생될 수 있다. 즉, 두 개의 낮은 Q-factor를 갖는 링형 광 변조기를 직렬 연결하여 광학적 대역폭(

)을 증가 시켰으나, 전기적 대역폭(

)은 오히려 감소하게 되어 전체 광 변조 장치의 3-dB 전광 변환 대역폭(

)이 크게 증가하지 못하거나 오히려 줄어 들 수 있는 상황이 발생될 수 있다.This increases the time constant (T = RC) and the electrical bandwidth of the ring type optical modulator (

) To eventually reduce the total optical bandwidth of the ring-shaped optical modulator (

) May be reduced. In other words, by connecting two low Q-factor ring-type optical modulators in series, the optical bandwidth (

), But the electrical bandwidth (

) Rather decreases, resulting in a 3-dB all-optical conversion bandwidth (

) May not be significantly increased or may be reduced.

In addition, resonator elements such as ring type optical modulators are greatly affected by process error. Even if the same ring type optical modulator is manufactured, the pass spectrums of the two ring type optical modulators may not completely match due to the process error.

3 is a view showing a first structure of an optical modulation device according to an embodiment of the present invention.

)을 개선 시키기 위한 제1 구조의 광 변조 장치(300)를 제공한다. 구체적으로 제1 구조에 따른 광 변조 장치(300)는 낮은 Q-factor를 갖는 링형 광 변조기(310)와 리플렉터(Reflector)(320)가 연결한 구조를 가질 수 있다. 구체적으로 리플렉터(320)는 링형 광 변조기(310)를 구성하는 버스형 광 도파로(311)의 출력단에 배치될 있다.Referring to FIG. 3, the 3-dB all-optical conversion bandwidth of the ring type optical modulator 310 (

) To improve the optical modulation device 300 of the first structure. Specifically, the optical modulation device 300 according to the first structure may have a structure in which a ring-type optical modulator 310 having a low Q-factor and a reflector 320 are connected. Specifically, the reflector 320 may be disposed at an output terminal of the bus-type optical waveguide 311 constituting the ring-type optical modulator 310.

That is, the optical signal input to the optical modulation device 300 according to the first structure is input to the ring optical waveguide 312 through the input terminal of the bus optical waveguide 311 constituting the ring optical modulator 310 and is primary The light is modulated, reflected through the reflector 320 disposed at the output terminal of the bus-type optical waveguide 311, and re-entered into the ring-shaped optical waveguide 312 to be secondary light modulated.

Thus, since the optical signal is optically modulated twice through the ring-type optical modulator 310 having a low Q-factor, the optical modulation efficiency can be improved by increasing the extinction ratio like the ring-shaped optical modulator connected in series in FIG. 2. In addition, since the light modulating device 300 according to the first structure passes through the same ring-shaped light modulator 310 twice, the pass spectrum due to the process error coincides, thereby eliminating the need to adjust the pass wavelength.

)을 확보하면서 커패시턴스가 증가하지 않으므로 높은 전기적 대역폭(

)을 유지할 수 있다. 결과적으로 광 변조 장치(300)는 전광 변환 대역폭(

)이 증가하여 고속으로 광 신호를 변조하는 것이 가능할 수 있다.Since the optical modulation device 300 according to the first structure uses a ring-type optical modulator 310 having a low Q-factor, a high optical bandwidth (

) While ensuring high electrical bandwidth (

). As a result, the optical modulation device 300 is the total light conversion bandwidth (

) May be increased to modulate the optical signal at high speed.

In this case, the distance between the ring-type optical modulator 310 having a low Q-factor and the reflector 320 in the optical modulation device 300 may be very important. In other words, the round-trip time for the optical signal output from the ring-shaped optical modulator 310 to be reflected by the reflector 320 and input to the ring-shaped optical modulator 310 should be a sufficiently short time. Specifically, the round trip time may be much shorter than a 1-bit time period of the electrical signal applied to the ring-shaped optical waveguide 312. For example, assuming that 1 bit of the electrical signal is 100 ps, the optical signal that is primary light modulated through the ring type optical modulator 310 is reflected by the reflector 320 before 100 ps passes, and then through the ring type optical modulator 310 It can be secondary light modulated.

To this end, the reflector 320 may be implemented in the form of a loopback mirror using a multimode interference (MMI) coupler or a Y-branch coupler, or may be implemented in the form of a Bragg grating. However, the reflector 320 is not limited to this type, and a silicon optical device capable of reflecting an optical signal with a short length may be used.

4 is a view showing a second structure of an optical modulation device according to an embodiment of the present invention.

When an optical signal is modulated through an electrical signal using a ring-type optical modulator, a chirping phenomenon in which frequency and phase continuously change with time occurs, which causes deterioration of optical transmission performance.

In order to solve such a chirping phenomenon, the present invention may apply a differential electrical signal to each ring-type optical modulator by connecting two optical modulation devices including a reflector with a 1x2 power coupler.

That is, the optical modulation device 400 according to the second structure divides the optical signal into a first optical signal and a second optical signal, and transmits power to each input end of the optical waveguides arranged along the first path and the second path Ring coupler light disposed on each of the power couplers 410 and the optical waveguides disposed along the first path and the second path to modulate the phase of at least one of the first optical signal and the second optical signal through an electrical signal. Modulators 420 and 430.

At this time, the optical signal is primary phase modulated through the ring-shaped optical modulators 420 and 430 arranged in the first path and the second path by branching into the first optical signal and the second optical signal through the power coupler 410, It may be reflected through the reflectors 440 and 450 disposed at the output ends of the optical waveguides and re-entered into the ring-type optical modulators 420 and 430 to be secondary phase modulated.

5 is a diagram illustrating a third structure of an optical modulation device according to an embodiment of the present invention.

The optical modulation device 500 according to the third structure may have a structure similar to the optical modulation device 400 according to the second structure. However, the optical modulation device 500 may separate the input / output ports of the optical signal by connecting the two ring-type optical modulators 520 and 530 connected to the reflectors 540 and 550 with the 2x2 power coupler 510.

6 is a diagram illustrating a fourth structure of an optical modulation device according to an embodiment of the present invention.

)은 감소하지만 광 변조 효율은 증가 시킬 수 있다. 이러한 제4 구조에 따른 광 변조 장치(600)는 전기적 대역폭(

)은 충분히 여유가 있고, 링형 광 변조기의 구동 전압을 낮추고자 할 때 이용될 수 있다.The optical modulation device 600 according to the fourth structure provides a structure in which a ring-shaped optical modulator is connected in series. The optical modulation device 600 is an electrical bandwidth (

) Decreases but can increase the light modulation efficiency. The optical modulation device 600 according to the fourth structure has an electrical bandwidth (

) Has sufficient margin and can be used when the driving voltage of the ring-shaped optical modulator is to be lowered.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer readable medium. The computer-readable medium may include program instructions, data files, data structures, or the like alone or in combination. The program instructions recorded on the medium may be specially designed and constructed for the embodiments or may be known and usable by those skilled in computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs, DVDs, and magnetic media such as floptical disks. -Hardware devices specially configured to store and execute program instructions such as magneto-optical media, and ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language code that can be executed by a computer using an interpreter, etc., as well as machine language codes produced by a compiler. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

The software may include a computer program, code, instruction, or a combination of one or more of these, and configure the processing device to operate as desired, or process independently or collectively You can command the device. Software and / or data may be interpreted by a processing device, or to provide instructions or data to a processing device, of any type of machine, component, physical device, virtual equipment, computer storage medium or device. , Or may be permanently or temporarily embodied in the transmitted signal wave. The software may be distributed on networked computer systems, and stored or executed in a distributed manner. Software and data may be stored in one or more computer-readable recording media.

As described above, although the embodiments have been described by a limited drawing, a person skilled in the art can apply various technical modifications and variations based on the above. For example, the described techniques are performed in a different order than the described method, and / or the components of the described system, structure, device, circuit, etc. are combined or combined in a different form from the described method, or other components Alternatively, even if replaced or substituted by equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

100, 310, 420, 430, 520, 530: ring type optical modulator
110, 311: Bus-type optical waveguide
120, 312: ring type optical waveguide
320, 440, 450, 540, 550: Reflector

Claims (14)

In the optical modulation device,
A bus-type optical waveguide through which optical signals are transmitted and received; And
A ring-type optical waveguide that optically modulates an optical signal output through the bus-type optical waveguide according to an electrical signal
Including,
The optical signal,
It is input to the ring-type optical waveguide through the input end of the bus-type optical waveguide and is primary-optical modulated, reflected through a reflector disposed at the output end of the bus-type optical waveguide, and re-entered into the ring-type optical waveguide to re-enter the secondary optical waveguide An optical modulation device that is modulated and then output through the bus-type optical waveguide.
According to claim 1,
The distance between the ring-shaped optical waveguide and the reflector,
An optical modulation device associated with a time period for one bit of the electrical signal.
According to claim 1,
The upper reflector,
An optical modulation device that is either a loop mirror or a Bragg grating.
A power coupler for dividing the optical signal into the first optical signal and the second optical signal and transmitting the optical signal to each input terminal of the optical waveguides arranged along the first path and the second path; And
A phase shifter in the form of a ring-shaped optical waveguide disposed in each of the optical waveguides disposed along the first path and the second path to modulate the phase of at least one of the first optical signal and the second optical signal through an electrical signal ( Phase shifter)
Including,
The optical signal,
A first optical signal is branched to the first optical signal and the second optical signal through the power coupler, the first phase is modulated through a phase shifter disposed in the first path and the second path, and a reflector disposed in the output stage of the optical waveguides (Reflector) It is reflected through the re-input to the phase shifter, the second phase modulated and then the optical modulation device output through the power coupler.
According to claim 4,
The phase shifter disposed along the first path and the second path,
An optical modulation device that modulates a phase of at least one of the first optical signal and the second optical signal through a differential electrical signal.
According to claim 4,
The distance between the phase shifter and the reflector,
An optical modulation device associated with a time period for one bit of the electrical signal.
According to claim 4,
The upper reflector,
An optical modulation device that is either a loop mirror or a Bragg grating.
Receiving an optical signal through an input terminal of the bus-type optical waveguide; And
Optically modulating the optical signal received through the ring-type optical waveguide to the input terminal of the bus-type optical waveguide according to an electrical signal.
Including,
The step of modulating the light,
An optical modulation method of performing secondary light modulation on a light signal reflected through a reflector disposed at an output terminal of the bus-type optical waveguide by being primary-optical modulated through the ring-type optical waveguide.
The method of claim 8,
The distance between the ring-shaped optical waveguide and the reflector,
A light modulation method associated with a time period for one bit (Bit) of the electrical signal.
The method of claim 8,
The upper reflector,
A method of light modulation, either a loop mirror or a Bragg grating.
The optical waveguide is branched to the first optical signal and the second optical signal through a power coupler, and the branched first optical signal and the second optical signal are arranged along the first path and the second path. Transmitting to each of the input terminals; And
Modulating at least one phase of the first optical signal and the second optical signal through a phase shifter in the form of a ring-shaped optical waveguide disposed along the first and second paths
Including,
The step of modulating the phase,
An optical modulation method of performing secondary phase modulation of a first optical signal and a second optical signal reflected through a reflector disposed in an output terminal of each of the optical waveguides through primary phase modulation through the phase shifter.
The method of claim 11,
The phase shifter disposed along the first path and the second path,
Optical modulation method for modulating the phase of at least one of the first optical signal and the second optical signal through a differential electrical signal.
The method of claim 11,
The distance between the phase shifter and the reflector,
A light modulation method associated with a time period for one bit (Bit) of the electrical signal.
The method of claim 11,
The upper reflector,
A method of light modulation, either a loop mirror or a Bragg grating.

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