KR100388356B1 - Method and Apparatus of Dispersion Compensation using Grating - Google Patents

Abstract

Disclosed are a dispersion compensation method and a dispersion compensator using an optical waveguide grating. The dispersion compensating method and the dispersion compensator using the optical waveguide grating of the present invention include a beam splitter / coupling unit for dividing or combining a beam path, a dispersion compensator comprising an optical waveguide for forming an optical waveguide grating, and the beam splitter / The beam is connected between the coupler and the dispersion compensator, and at least two optical waveguides are formed on an extension line of the dispersion compensator. Dispersion compensation of the beams through the optical waveguide grating, and then recombination through the beam splitter / combining unit is characterized in that the time delay characteristics of the respective distributed compensation beams are averaged according to the wavelength to remove noise and ripple. According to the present invention, it is possible to implement a distributed compensator having a time delay characteristic in which ripple is removed, and there is an advantage in that the implementation is simple and simple. In addition, there is no need to manufacture a specially apodized grating has the advantage that the price is low. And, it can be easily applied to the optical communication industry and optical system development.

Description

Dispersion Compensation Method Using Optical Waveguide Grating and Dispersion Compensation {Method and Apparatus of Dispersion Compensation using Grating}

The present invention relates to a dispersion compensation method and a dispersion compensator using an optical waveguide grating, and in particular, after the dispersion compensation of the beams through the optical waveguide gratings respectively present in both optical paths through which the beams travel in the two optical waveguides, recombination is performed again. The present invention relates to a dispersion compensation method and a dispersion compensator using an optical waveguide grating which removes noise and ripple by averaging the time delay characteristics of each distributed compensated beam according to a wavelength.

Recently, a distributed compensator using an optical waveguide grating has been in the spotlight as a distributed compensator for a high-speed communication system because it is cheaper and less affected by the nonlinearity of the optical fiber waveguide than the dispersion compensating optical fiber. .

However, a problem to be overcome in a dispersion compensator using an optical waveguide grating is to remove a ripple component present in a time delay characteristic. As a method of overcoming this problem, a method of constructing a dispersion compensator using an apodized optical waveguide grating has been studied and reported. However, since the apodized optical waveguide grating is considerably more expensive and difficult to fabricate than a general optical waveguide grating, a dispersion compensator using an apodized optical waveguide grating is difficult and expensive.

Accordingly, an object of the present invention is to provide dispersion compensation by reflecting or transmitting beams individually by using a dispersion compensator composed of optical waveguide gratings respectively existing in both paths of two optical waveguides so as to realize a distributed compensator that is easy to manufacture and inexpensive to manufacture. The present invention provides a dispersion compensation method and a dispersion compensator using an optical waveguide grating having a time delay characteristic in which ripple is eliminated by averaging the time delay characteristics of each distributed compensated beam by recombination.

1 is a basic conceptual diagram showing a dispersion compensation method having a time delay characteristic in which ripple is eliminated using an optical waveguide grating according to the present invention;

FIG. 2A is a graph of a time delay characteristic of an optical waveguide grating for implementing an ideal dispersion compensation method having a time delay characteristic without ripple using the optical waveguide grating of FIG. 1;

Figure 2b is a graph of the time delay characteristics appearing in the output unit by the ideal dispersion compensation method according to the present invention,

3 is a view showing a first embodiment of implementing a dispersion compensation method by reflecting a beam through an optical waveguide grating of a dispersion compensation unit;

4 is a view showing a second embodiment of implementing a dispersion compensation method by transmitting a beam through an optical waveguide grating of a dispersion compensation unit;

5A and 5B illustrate two examples of a dispersion compensator using optical waveguide gratings respectively present in both optical paths of an optical fiber waveguide consisting of two cores or an optical fiber waveguide consisting of two D-shaped optical waveguides;

6 is a view showing another example of a dispersion compensator using an optical waveguide grating of two tapered planar waveguides or optical fiber waveguides;

7A and 7B are diagrams illustrating third and fourth embodiments of a dispersion compensation method in which distributed compensation is performed by reflecting a beam by continuously connecting the same or different dispersion compensators in series or in parallel with each other;

8A and 8B are diagrams illustrating fifth and sixth embodiments of a dispersion compensation method in which dispersion compensation is performed through a beam by connecting the same or different dispersion compensators in series or in parallel to each other.

Explanation of symbols on the main parts of the drawings

1 input unit 2 beam splitter / combiner unit

4: optical waveguide 6a, 6b: optical waveguide grating

8: output section 10, 10a, 10b,... 10n: distributed compensation unit

14: optical fiber waveguide consisting of two cores

24: optical fiber waveguide consisting of two D-shaped optical waveguides

34 tapered optical waveguide

S1, S2: Time delay curve of the optical waveguide grating of the dispersion compensation part

The dispersion compensation method and the dispersion compensator using the optical waveguide grating for achieving the above object of the present invention, the dispersion compensation consisting of a beam splitting / coupling portion for dividing or combining the path of the beam, and the optical waveguide forming the optical waveguide grating And at least two optical waveguides connected between the beam splitter / combiner and the dispersion compensator to extend the beam and extend along the extension line of the dispersion compensator. Compensating the beams through the optical waveguide gratings of the dispersion compensator for each beam and then recombining the beams through the beam splitter / combiner to average the time delay characteristics of each distributed compensating beam according to the wavelength to remove noise and ripple. It features.

The basic configuration of the present invention consists of a beam splitter / combiner and a dispersion compensator. At this time, the dispersion compensator is formed again two optical waveguides, each of which is formed with an optical waveguide grating. The optical waveguide grating of the dispersion compensator may be various types of optical waveguide gratings such as a short period grating, a long period grating, and an inclined grating, and the period of the grating may be changed periodically or aperiodically. In addition, the period of the optical waveguide grating has a value in the range of 0.1 μm to 1 mm. The reflectances of the optical waveguide gratings respectively present in both optical paths of the two optical waveguides of the dispersion compensator may be different or the same, and in the case of the same, ideal dispersion compensation can be achieved. Even if they are different from each other, an ideal dispersion compensator can be realized in which noise and ripple are completely eliminated by adjusting the phase or reflectance of the grating existing on one or both sides of the waveguide.

Basic operation principle is as follows. A beam composed of multi-wavelength components is incident on the beam splitter / combining unit, and the beam is divided into two optical waveguides, an optical fiber waveguide composed of two cores, or an optical fiber waveguide composed of D-shaped optical waveguides. The beams traveling in both paths of the optical waveguide are dispersed or compensated by being reflected or transmitted by the optical waveguide gratings respectively present in both paths of the optical waveguide, and then distributedly compensated by recombining the distributed compensation beams in the beam splitter / combiner. The time delay characteristics of the beams can be summed over the wavelength and averaged to eliminate noise and ripple.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

Here, in the description of the present invention, the same reference numerals will be given to the same components that perform the same function.

1 is a basic conceptual diagram illustrating a dispersion compensation method having a time delay characteristic in which ripples using an optical waveguide grating according to the present invention are removed. Referring to FIG. 1, the basic principle of dispersion compensation proposed in the present invention is that, as described above, when a beam composed of a multi-wavelength component is incident through the input unit 1 of the beam splitter / combiner 2, the beam splitter / The beam splits at the coupler 2 and proceeds to the two optical waveguides 4. The beams traveling to the two optical waveguides 4 are reflected or transmitted by the optical waveguide gratings respectively present in both optical paths in the optical waveguides of the dispersion compensator 10 to be distributedly compensated by experiencing a time delay depending on the wavelength. . The time delay characteristic experienced by the beam reflecting or transmitting by each of the optical waveguide gratings constituting the dispersion compensator 10 is expressed by Equation 1 below.

----------------------------------- [Equation 1]

here, Denotes time delay characteristics due to the optical waveguide gratings respectively present in the dispersion compensation unit 10, Denotes the phase component of the optical waveguide grating respectively present in the dispersion compensator 10.

Each beam of the dispersion compensation unit 10 is reflected or transmitted by the optical waveguide grating, and the beams that are compensated for dispersion are recombined by the beam splitter / combiner 2 and come out to the output unit 8. The time-delay characteristics experienced by dispersion-compensated beams that experience a time delay by reflecting or transmitting through an optical waveguide grating having the same or nearly similar characteristics in both paths of the optical waveguide and then being distributed compensated are as follows. It is expressed by [Equation 2].

---------------- [Equation 2]

Here, tau represents a time delay characteristic at the output of the dispersion compensator according to the dispersion compensation method of the present invention, Wow Denotes the time delay characteristics of each optical waveguide grating. As can be seen from Equation 2, it can be seen that the time delay characteristics of the dispersion compensator according to the dispersion compensation method of the present invention average the time delay characteristics experienced by the beam through the optical waveguide gratings of the dispersion compensator. Therefore, a dispersion compensator having a time delay characteristic in which noise and ripple are eliminated by averaging the time delay characteristics of the optical waveguide gratings existing in both optical paths of the optical waveguides according to the wavelengths together can be implemented.

In order to minimize ripple due to the time delay characteristics of the dispersion compensator according to the present invention, the phase or reflectance of the grating in any one path or all of the paths of the optical waveguide 4 of the dispersion compensator 10 is reduced. I can regulate it.

FIG. 2A is a graph of a time delay characteristic of an optical waveguide grating for implementing an ideal dispersion compensation method having a time delay characteristic in which ripple is removed using the optical waveguide grating of FIG. 1. Referring to FIG. 2A, examples of graphs S1 and S2 illustrating time delay characteristics according to wavelengths of optical waveguide gratings respectively present in two optical waveguides in the dispersion compensator.

The optical waveguide gratings respectively present in both paths of the optical waveguide 4 constituting the dispersion compensator 10 may have one or more identical or different optical waveguide gratings in each optical path, and the dispersion compensation average gradient and dispersion The compensation bandwidth can also have any value.

Figure 2b is a graph of the time delay characteristics appearing in the output unit by the ideal dispersion compensation method according to the present invention. As shown in FIG. 2B, when the optical waveguide gratings having the time delay characteristics S1 and S2 as shown in FIG. 2A are respectively present in both paths of the optical waveguide, the time delay characteristics according to the wavelength of the dispersion compensator according to the present invention. Indicates.

FIG. 3 is a diagram illustrating a first embodiment in which a dispersion compensation method is implemented by reflecting a beam through an optical waveguide grating of a dispersion compensator. Referring to FIG. 3, the dispersion compensator proposed in the first embodiment includes two parallel planar waveguides or optical waveguides 4, beam splitter / coupler 2, and optical waveguides 4 in each of the two paths. The dispersion compensator 10 includes the optical waveguide gratings 6a and 6b.

The beam configured as described above and incident on the input unit 1 is divided by the beam splitter / combiner 2. Thereafter, the divided beams are respectively reflected through the optical waveguide gratings 6a and 6b respectively present in both optical paths of the two parallel optical waveguides 4 constituting the dispersion compensator 10 and are time-delayed according to the wavelength. After the dispersion compensation is performed and distributed compensation is performed, the dispersion compensation is performed with the time delay property of which the ripple is removed by averaging each time delay property of the reflected beam by recombining through the beam splitter / combiner 2.

At this time, in order to match the phase or reflectance of each optical waveguide grating of the dispersion compensator 10 to each other, it is possible to adjust the phase or reflectance by using a UV trimming method. The optical waveguide to which UV is exposed by UV trimming changes the effective refractive index of the optical waveguide, thereby changing the phase or reflectance of the grating. In addition to the method of adjusting the phase or reflectance of the grating, a method of providing a diameter change of the optical waveguide may be used by applying a strain while attaching a piezoelectric material such as piezoelectric material (PZT) in the longitudinal direction of the grating.

4 is a diagram illustrating a second embodiment of implementing a dispersion compensation method by transmitting a beam through an optical waveguide grating of a dispersion compensation unit. Referring to FIG. 4, the dispersion compensator proposed in the second embodiment is configured by further combining the beam splitter / combiner 2 with the dispersion compensator presented in the first embodiment. That is, two parallel planar waveguides or optical fiber waveguides 4, the beam splitter / combiner 2 including the input unit 1, and the optical waveguide gratings 6a and 6b respectively present in both paths of the optical waveguide 4, respectively. And a beam splitter / combiner 2 including an output unit 8 and a dispersion compensator 10 including a < RTI ID = 0.0 >

The beam configured as described above and incident on the input unit 1 is divided by the beam splitter / combiner 2. Then, the beam split in the beam splitter / combiner 2 separates the optical waveguide gratings 6a and 6b respectively present in both optical paths of the two parallel optical waveguides 4 constituting the dispersion compensator 10. After each transmission is experienced through the time delay according to the wavelength and distributed compensation, and then recombined through the beam splitter / combiner (2) connected to the output terminal (8) by averaging the respective time delay characteristics of the transmitted beam noise and Dispersion compensation with time delay with ripple removed is made.

5A and 5B illustrate two examples of a dispersion compensator using optical waveguide gratings existing in both optical paths of an optical fiber waveguide consisting of two cores or an optical fiber waveguide consisting of two D-shaped optical waveguides. As shown in FIG. 5A, the dispersion compensator 10 includes an optical fiber waveguide 14 composed of two cores, and optical waveguide gratings 6a and 6b respectively present in both paths of the optical fiber waveguide.

As shown in FIG. 5B, the dispersion compensator 24 includes an optical waveguide 24 composed of two D-shaped optical waveguides, and optical waveguide gratings 6a and 6b respectively present in both paths of the optical fiber waveguide. . Optical waveguide gratings may be of various types such as short-period gratings, long-period gratings, and inclined gratings, and the period may also be changed periodically aperiodically. In addition, one or more identical or different optical waveguide gratings may exist in both optical paths of the optical waveguide.

FIG. 6 is a diagram illustrating another example of the dispersion compensator of FIG. 1 using two tapered planar waveguides or an optical waveguide grating of an optical fiber waveguide. Referring to FIG. 6, the dispersion compensator 10 presented here includes two planar waveguides or optical fiber waveguides 34 having constant tapered regions, and optical waveguide gratings 6a and 6b respectively present in the tapered optical waveguides. It includes. The length and the tapered degree of the tapered region of the optical waveguide may have any value in consideration of the dispersion compensation bandwidth and the dispersion compensation slope of the dispersion compensator. Optical waveguide gratings may be of various types such as short-period gratings, long-period gratings, and inclined gratings, and the period may also be changed periodically aperiodically. In addition, one or more identical or different optical waveguide gratings may exist in both optical paths of the tapered optical waveguide.

7A and 7B are diagrams illustrating third and fourth embodiments of a dispersion compensation method in which distributed compensation is performed by reflecting beams by successively connecting the same or different dispersion compensators in series or in parallel with each other. As shown in FIG. 7A, in the third embodiment, a distributed compensator is configured by connecting a plurality of distributed compensators in series. In other words, the dispersion compensator is connected to the two optical waveguides 4 and the beam splitter / combination section 2 in series, and is composed of the dispersion compensators 10a, 10b, ... 10n connected in series.

On the other hand, as shown in Figure 7b, the distributed compensator is configured by connecting a plurality of distributed compensators in the fourth embodiment in parallel. That is, the dispersion compensator is connected in parallel with the two optical waveguides 4 and the beam splitter / combination section 2, and is composed of a plurality of distributed compensation sections 10a, 10b, ... 10n.

Here, the dispersion compensators continuously connected in series or in parallel in the two parallel optical waveguides of FIGS. 7A and 7B may be the same or different from each other, and may be a series-parallel mixed type.

8A and 8B are diagrams illustrating fifth and sixth embodiments of a dispersion compensation method in which dispersion compensation is performed through a beam by connecting the same or different dispersion compensators in series or in parallel to each other. 8A and 8B, the dispersion compensator shown in the fifth and sixth embodiments includes the beam splitter / combiner 2 in the dispersion compensators described in the third and fourth embodiments. It is made up of more combinations. That is, the two parallel planar waveguides or the optical fiber waveguide 4, the beam splitting / combining unit 2 including the input unit 1, and the optical waveguide grating respectively existing in both paths of the optical waveguide 4 respectively. The beam splitter / combiner 2 includes a plurality of distributed compensation units 10 and an output unit 8 connected in parallel.

As shown in FIG. 8A, two optical waveguides 4 and two beam splitter / combination units 2 are connected in series and include a plurality of continuous dispersion compensators 10a, 10b, ... 10n. do. As shown in FIG. 8B, two optical waveguides 4 and dispersion beams 10a, 10b, ... 10n connected in parallel with two beam splitters / couplers 2 and connected in parallel are included.

Here, the dispersion compensators continuously connected in series or in parallel in the two optical waveguides of FIGS. 8A and 8B may be the same or different from each other, and may be a serial-parallel mixed type.

As described above, the dispersion compensating method and the dispersion compensator using the optical waveguide grating according to the present invention are respectively present in both parallel planar waveguides or in optical fiber waveguides composed of two cores or in two paths through which beams travel. The optical waveguide grating reflects or transmits optical pulses, respectively, and recombines the reflected or transmitted beams, and the time delay characteristics of the reflected or transmitted beams are summed and averaged according to the wavelengths, thereby eliminating the noise and ripple. By performing the distributed compensation, the device does not need a device such as a shuffler, and the price is low because there is no need to manufacture a simple, simple and apodized grating in implementing a distributed compensator with a ripple-free time delay. There is this. In addition, this easy implementation of a distributed compensator with a wide range of applications is expected to be a big accelerator for developing the optical communication industry and optical system development.

The present invention is not limited to the above-described embodiment, and it will be apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Claims (27)

A beam splitter / combiner for splitting or combining a beam path, a dispersion compensator including an optical waveguide forming an optical waveguide grating, and a beam compensator are connected between the beam splitter / combiner and a dispersion compensator. In the dispersion compensation method using the optical waveguide of the phase compensation compensator consisting of at least two optical waveguides on the extension line of the dispersion compensation portion, The time-delay characteristics of the respective distributed compensation beams are distributed by compensating the beams through the optical waveguide grating of the dispersion compensator for the divided beams inputted to the beam splitter / combiner and then recombining them through the beam splitter / combiner. The dispersion compensation method using the optical waveguide grating, characterized in that the averaged by the noise and ripple is removed. The dispersion compensation method using the optical waveguide grating according to claim 1, wherein the dispersion compensation is performed by reflecting a beam through the optical waveguide grating of the dispersion compensating unit. The dispersion compensation method using an optical waveguide grating according to claim 2, wherein the same or different dispersion compensators are connected in series to each other in series to reflect the beams to thereby perform dispersion compensation. The dispersion compensation method using an optical waveguide grating according to claim 2, wherein the same or different dispersion compensators are continuously connected in parallel with each other to reflect the beams. The dispersion compensation method using the optical waveguide grating according to claim 2, wherein the same or different dispersion compensating units are connected in series or in parallel to each other and connected in series to reflect the beam. The dispersion compensation method using the optical waveguide grating according to claim 1, wherein the dispersion compensation is performed by transmitting a beam through the optical waveguide grating of the dispersion compensating unit. The dispersion compensation method using the optical waveguide grating according to claim 6, wherein the same or different dispersion compensators are continuously connected in series with each other in series to transmit dispersion beams. The dispersion compensation method using an optical waveguide grating according to claim 6, wherein two or more of the same or different dispersion compensators are continuously connected in parallel to each other to perform phase compensation by transmitting a beam. 7. The dispersion compensation method according to claim 6, wherein two or more of the same or different dispersion compensation units are connected in series and in parallel to each other and continuously connected to each other to transmit and compensate the dispersion beam. The time delay characteristics of each distributed compensated beam are averaged according to the wavelength so that noise and ripple can be eliminated. A beam splitter / combiner for splitting or combining a path of the beam; A dispersion compensator comprising an optical waveguide formed by forming an optical waveguide grating for performing dispersion compensation on the divided beams input to the beam splitter / combiner, and At least two optical waveguides connected between the beam splitter / combiner and the dispersion compensator to advance the beam and extend on an extension line of the dispersion compensator; Dispersion compensator using an optical waveguide grating, characterized in that consisting of. The dispersion compensator using the optical waveguide grating of claim 10, wherein the dispersion compensator is formed of an optical waveguide grating reflecting and beam-compensating the beam. The dispersion compensator using the optical waveguide grating of claim 11, wherein the dispersion compensator is formed by successively connecting two or more identical or different dispersion compensators in series with each other. The dispersion compensator using an optical waveguide grating according to claim 11, wherein the dispersion compensator is formed by successively connecting two or more identical or different dispersion compensators in parallel with each other. The dispersion compensator using an optical waveguide grating according to claim 11, wherein the dispersion compensator is formed by connecting two or more identical or different dispersion compensators in series and in parallel to each other. The dispersion compensator using the optical waveguide grating of claim 10, wherein the dispersion compensator is formed of an optical waveguide grating through which beams are distributed and compensated for. The dispersion compensator using the optical waveguide grating of claim 15, wherein the dispersion compensator is formed by successively connecting two or more identical or different dispersion compensators in series with each other. The dispersion compensator using the optical waveguide grating of claim 15, wherein the dispersion compensator is formed by connecting two or more identical or different dispersion compensators to each other in parallel. The dispersion compensator using the optical waveguide grating according to claim 15, wherein the dispersion compensator is formed by connecting two or more identical or different dispersion compensators in series and in parallel to each other. The dispersion compensator using the optical waveguide grating of claim 10, wherein a period of the optical waveguide grating of the dispersion compensator is periodic or aperiodic. The dispersion compensator using an optical waveguide grating according to claim 10, wherein a period of the optical waveguide grating of the dispersion compensator has a value ranging from 0.1 μm to 1 mm. The dispersion compensator using the optical waveguide grating of claim 10, wherein the dispersion compensator comprises two or more identical or different optical waveguide gratings in each of two planar waveguides or both paths in the optical fiber waveguide. The dispersion compensator using an optical waveguide grating of claim 10, wherein the dispersion compensator comprises an optical waveguide grating respectively existing in two planar waveguides or optical fiber waveguides having a constant tapered region. The dispersion compensator using an optical waveguide grating according to claim 10, wherein the dispersion compensator comprises an optical waveguide grating respectively existing in an optical fiber waveguide consisting of two cores or an optical fiber waveguide consisting of two D-shaped optical fiber waveguides. The optical waveguide grating according to claim 10, wherein the dispersion compensator comprises at least two identical or different optical waveguide gratings respectively in an optical fiber waveguide consisting of two cores or an optical waveguide consisting of two D-shaped optical waveguides. Distributed compensator used. The optical waveguide grating according to claim 10, wherein the phase or reflectance control is used to match the phase or reflectance of the optical waveguide gratings respectively present in both optical paths of the two optical waveguides of the dispersion compensator. Distributed compensator. The dispersion compensator using an optical waveguide grating according to claim 25, wherein UV trimming is used for at least one optical path to adjust phase or reflectance. 26. The dispersion compensator of claim 25, wherein a strain is applied to the at least one optical path by attaching a piezoelectric material such as PZT in the longitudinal direction of the optical waveguide grating to control phase or reflectance.