KR100283098B1 - Optical wavelength filtering using the multi-mode interferometer and multi-grating - Google Patents

Abstract

The present invention relates to a wavelength detector using a multi-mode interferometer and a diffraction grating, and more particularly, to a wavelength detector capable of ensuring control of wavelength-sensitive optical switching elements and optical logic elements by extracting narrow wavelengths.

The multi / demultiplex method, which is widely used in the wavelength division transmission, uses an optical waveguide grating and very few uses a phasar (phased array) using a multi-mode interferometer. However, in the case of using the optical waveguide grating, there is a disadvantage that the intensity of the input light is very weakly attenuated for detecting a single wavelength at multiple wavelengths, and the manufacturing is not easy due to the complexity of the structure.

According to the present invention, after a single wavelength is detected among multiple wavelengths by using a multi-diffraction grating, the light evenly divided by a multi-mode interferometer is used to make the wavelengths different from each other. We present a wavelength detector that can be input to.

Description

Optical wavelength filtering using the multi-mode interferometer and multi-grating}

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a wavelength filtering device using a multi mode interferometer and a diffraction grating, and particularly to control wavelength-sensitive optical switching devices and optical logic devices by extracting narrow wavelengths. It relates to a wavelength detector that can be sure.

In order to satisfy the increasing amount of information communication day by day, a large amount of high-speed information communication system is required. Therefore, the transmission system using the optical fiber is becoming common, but the exchange system linking it still uses the function of the electronic. That is, it must satisfy the complete optical communication in which the light is exchanged as it is.

The optical exchange device invented and used in the related art has a characteristic that responds very sensitively to the wavelength of incident light, and is a vertical resonance incident structure using an electro-optic effect property generated in most semiconductors. cavity stack layer).

In the case of multiple wavelengths incident, the multiple / demultiplex method, which is widely used in wavelength division transmission, uses an arrayed waveguide graing, and very few uses a phasar (phased array) using a multi-mode interferometer. There is a situation. However, when the optical waveguide grating is used, a large number of waveguides are required to obtain the desired efficiency, and it is very difficult to overcome polarization dependence and realize a flattened output result. Therefore, there is a disadvantage in that the intensity of light input to detect a single wavelength at multiple wavelengths is very weakly attenuated and the manufacturing is not easy due to the complexity of the structure.

Accordingly, an object of the present invention is to provide a wavelength detector capable of solving the above-mentioned disadvantages by enabling the detection of a single wavelength having a narrow wavelength width among multiple wavelengths using a multi-mode interferometer and a multi-diffraction grating.

A wavelength detector using a multi-mode interferometer and a diffraction grating according to the present invention for achieving the above object is a wavelength detector for detecting an optical signal of a single wavelength incident on an optical switching element or an optical logic element, A 1 × N multimode interferometer for equally dividing the optical signal into N and an optical signal divided evenly through the 1 × N multimode interferometer, and outputting each optical signal to have a phase difference due to a path difference However, each phase difference is achieved through an optical waveguide configured with a multi-diffraction grating filter and an optical waveguide configured with the multi-diffraction grating filter so that the equally divided multi-wavelength optical signals are detected and output as single wavelength optical signals, respectively. An N × N multimode interferometer for selectively outputting the N single wavelength optical signals output with The generated features.

Figure 1 (a) is a wavelength detector using a multi-mode interferometer and diffraction grating according to the present invention.

1 (b) is a detailed configuration diagram of the optical waveguide shown in (a).

Figure 1 (c) is a detailed configuration diagram of the diffraction grating (A) portion of Figure 1 (a).

<Description of Signs of Major Parts of Drawings>

11 multi-wavelength input 12 1 x N multi-mode interferometer

13 ₁ to 13 _N : first optical waveguide 15 ₁ to 15 _N : second optical waveguide

14 N × N multi-mode interferometer 16 optical logic element or optical switching element

17: n-type electrode 18: n-type material

19: Core of the optical waveguide 20: p-type material

21 ₁ to 21 _N : N multiple diffraction gratings 22 ₁ to 22 _N : N p-type electrodes

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

1 (a) is a wavelength detector using a multi-mode interferometer and a diffraction grating according to the present invention.

Referring to FIG. 1 (a), the 1 × N multimode interferometer 12 divides a beam of light incident from the multi-wavelength input unit 11 into N light beams having the same intensity. Play a role. The 1xN multi-mode interferometer 12 opposite the multi-wavelength input is connected with as many optical waveguides 13 ₁ to 13 _N as the number of equally divided lights. The N optical waveguides 13 ₁ to 13 _{N are} provided with a diffraction grating A on or under, so as to extract only necessary wavelengths.

FIG. 1B is a diagram showing details between the 1xN multimode interferometer 12 and the NxN multimode interferometer 14 of FIG. 1A.

Referring to FIG. 1 (b), each of the N first optical waveguides 13 _{1 to} 13 _N is divided into an A portion and a B portion as a path through which light passes. A portion of the first optical waveguide is a diffraction grating portion and has a function of selecting a specific wavelength. The portion B is designed to have a light path difference between the light passing through the diffraction grating and a structure in which the light passing through the portion B has a constant phase difference. Having a constant phase difference induces constructive or destructive interference in the desired portion. The optical path difference refers to the difference in optical path length (OPD; optical path length difference = nΔL, n: refractive index, and ΔL: actual length difference). For example, different lengths of the same material result in different lengths of light passing, and different materials have optical path differences due to differences in refractive indices of light.

As shown in FIG. 1B, the first optical waveguides 13 ₁ to 13 _N have a constant length difference, and the light passing through each optical waveguide has a constant phase difference due to the optical path difference.

A first optical waveguide ((13 ₁ ~ 13 _N) each of a constant length difference (ΔL) is generally L Δ, 2Δ L, 3ΔL, ... is set to be nΔL. The first optical waveguide (13 ₁ ~ 13 _N) The light passing through is passed through the optical coupler of the NxN multimode interferometer 14 after the required wavelength is selected in the A portion of the diffraction grating and has a phase difference in the B portion having a constant length difference. In the second optical waveguide 15 ₁ to 15 _N of FIG. 1 (a) connected to 14), constructive or destructive interference occurs for each wavelength, and when combined as a whole, a routing function for transmitting a wavelength to a desired port is provided. Done.

ΔL in the present invention is defined as the difference in length between the two shortest waveguides. The difference in length of each of the first optical waveguides 13 ₁ to 13 _{N of} FIG. 1B may be represented by an integer multiple difference of ΔL. That is, the actual length difference between the shortest optical waveguide and other optical waveguides may be represented by ΔL, 2ΔL, 3ΔL, ... nΔL, respectively, in order of length. The difference in length of each optical waveguide must be an integer multiple of ΔL so that the lights can have a constant phase difference. That is, in Fig. 1 (b), the absolute length of each of the first optical waveguides 13 ₁ to 13 _N is not important, and it is important to determine how fine the difference in length between the optical waveguides can be resolved.

At the output terminal of the N × N multi-mode interferometer 14, as shown in FIG. 1 (a), an optical waveguide 15 ₁ to 15 _N is connected to an optical logic element or an optical switching element that is sensitive to a wavelength. 16) is incident on light. This structure can simultaneously control the optical logic element or the light exchange element 16 and the diffraction grating A, so that the light exchange can be performed using the maximum of a single wavelength among the incident wavelengths.

FIG. 1 (c) is a detailed configuration diagram of the diffraction grating portion A of FIG. 1 (a).

An n-type electrode 17 is formed below the n-type material 18 under the core portion 19 of the optical waveguide, and a p-type material above the core portion 19 of the optical waveguide ( 20) N p-type electrodes 22 ₁ to 22 _N are formed on the top. In addition, the p-type material 20 is composed of _N multi grating filters 21 ₁ to 21 _N.

In detail, the operation of the above structure is activated or deactivated by the multiple diffraction grating filters 21 ₁ to 21 _N through current control of the p-type electrodes 22 ₁ to 22 _N. That is, when the current is applied to the first p-type electrode 22 ₁ , the effective refractive index around the first multiple diffraction grating filter 21 ₁ is changed, and thus the first multiple diffraction grating filter 21 ₁ is inactivated and thus corresponds to λ ₁ . The light is passed through. The same applies to other wavelengths. If a suitable phase difference is provided between the light passing through the multiple diffraction grating filters 21 ₁ to 21 _N , output to an N × N multimode interferometer 14 port corresponding to each wavelength is possible. The N × N multi-mode interferometer 14 may output N outputs by copying the light coming through the N paths as it is, or may adjust the phase of the light entering the N paths to the desired output unit.

Therefore, since a single wavelength filtered by current control can be output to a predetermined output unit, a predetermined wavelength can always be sent to a predetermined output unit. This means that a certain wavelength can be sent to a predetermined place, thereby having a routing function, and since a single wavelength has a small line width, it can be used for an optical switching device and an optical logic device that are sensitive to the wavelength.

Conventionally, the light incident on the light exchange element is assumed as a single characteristic wavelength, and attention has been paid only to the improvement of the property of the light exchange element. However, the trend of transmission is evolving into a multi-wavelength division scheme that carries multiple wavelengths at once, and it is necessary to find a way to use them directly in order to access full optical communication.

As described above, however, according to the present invention, when multiple wavelengths are incident, elements unnecessary for performing address detection and logic operations thereof can be greatly reduced. In addition, it is possible to perform an operation without attenuation of the wavelength intensity, and the efficiency of wavelength detection is very high, so that there is an excellent effect that can be used again as an optical signal without amplifying the wavelength intensity.

Claims (4)

A wavelength detector for detecting an optical signal of a single wavelength incident on an optical switching element or an optical logic element, A 1 × N multimode interferometer for equally dividing an optical signal of multiple wavelengths into N, The 1 × N multimode interferometer is configured to correspond to the equally divided optical signal, and outputs each optical signal to have a phase difference due to a path difference, wherein each of the equally divided multi-wavelength optical signals is a single wavelength optical signal. N optical waveguides each configured with multiple diffraction grating filters to be detected and outputted to A multi-mode interferometer comprising an N × N multimode interferometer for selectively outputting the N single wavelength optical signals output with respective phase differences through the optical waveguide in which the multi-diffraction grating filter is configured; and Wavelength detector using a diffraction grating. The method of claim 1, The multiple diffraction grating filter includes an n-type electrode electrically connected to the n-type material in an optical waveguide made of an n-type material, an optical waveguide core, and a p-type material; N p-type electrodes electrically connected to the p-type material, N diffraction gratings are formed inside the p-type material, and each current is applied to the electrodes to control the effective refractive index of each of the diffraction gratings so that the multi-wavelength optical signal is detected as a single wavelength optical signal. A wavelength detector using a multimode interferometer and a diffraction grating. The method of claim 1, The N optical waveguide has a different length difference, but the wavelength detector using a multi-mode interferometer and a diffraction grating, characterized in that the difference. The method of claim 1, The multi-diffraction grating filter is a wavelength detector using a multi-mode interferometer and a diffraction grating, characterized in that simultaneously controlled when controlling the optical switching element or the optical logic element.

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