KR100965842B1 - Optical add-drop multiplexer for multi-channel - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel optical add-drop multiplexer (OADM), and more particularly, a sample grating formed on an optical waveguide and a Bragg grating having a phase shifter attached thereto. The present invention relates to a multichannel optical splitter multiplexer having a wavelength variable using FBG).

The multi-channel optical branch coupling multiplexer of the present invention has an input terminal to which a multi-channel wavelength signal is input, a branch terminal to which a branched signal is output, a coupling terminal to which a signal having the same wavelength as the branched signal is input, and a wavelength not branched to the branch terminal. A multi-channel optical splitter multiplexer comprising an output terminal coupled to and output from a signal from the coupling stage, the multi-channel optical splitter multiplexer comprising: a first circulator for controlling a signal transmission direction between the input terminal and the branch terminal; A sample grating reflecting the multi-channel wavelength signal inputted through the first circulator; At least one Bragg grid for receiving the multi-channel wavelength signal reflected on the sample grid and reflecting a specific channel wavelength signal among the received multi-channel wavelength signals; And a second circulator for transmitting the signal passing through the Bragg grating and the signal input to the coupling end to the output end.

OADM, optical branch coupling multiplexer, waveguide, grating, FBG, Bragg grating, circulator

Description

Optical add-drop multiplexer for multi-channel

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel optical add-drop multiplexer (OADM), and more particularly, a sample grating formed on an optical waveguide and a Bragg grating having a phase shifter attached thereto. The present invention relates to a multichannel optical splitter multiplexer having a wavelength variable using FBG).

In general, a wavelength division multiplex (WDM) method is a method of simultaneously transmitting a plurality of channels using beams having different wavelengths in a communication using an optical fiber. In the single mode optical fiber, for example, two kinds of optical wavelengths of 1.3 mu m and 1.55 mu m with low attenuation are used.

The transmission equipment to which the wavelength division multiplexing method is applied is a device that divides one optical fiber channel by an optical wavelength using a single special coupler to be used as a plurality of communication paths. For example, by separating the 1.3 μm wavelength from the 1.55 μm wavelength, two separate signals are inputted into different wavelengths and transmitted through one optical fiber. The integrated signal is received and separated into two signals to be detected.

There are two mechanisms for the function of the wavelength division multiplexing device. One is the principle of diffraction / reflection depending on the wavelength, and the other is to separate and use a dichroic filter. In other words, one wavelength passes through the filter, but the other wavelength is reflected.

An example of a multiplexing device using a principle in which the refractive index varies depending on the wavelength is a combiner type optical branch-coupled multiplexer (OADM).

1 is a diagram illustrating a conventional multichannel optical branch coupling multiplexer. Referring to FIG. 1, a conventional optical branch coupling multiplexer is a wavelength-variable multichannel optical branch coupling multiplexer based on a Bragg grating (FBG), and has the same optical fiber in both paths of a Mach-Zehnder interferometer. This is a Mach-Zehnder interferometer type OADM that implements an optical branch coupling multiplexer by fabricating a grating.

This is done by constructing a Mahzander interferometer using a 3 kHz coupler, and forming a grating in the middle of an arm of the same length to perform an add / drop function. In other words, when the multi-channel signal is input to the input terminal, the lattice filter made in the Mahzender interferometer splits one wavelength, and the signal having the same wavelength as the branched wavelength tube is put through the coupling terminal to complete the transmission.

However, such a conventional optical branch coupling multiplexer has a difficulty in making the length and the grating generation position of the Mach-Zehnder interferometer the same, and thus is poor in reproducibility and poor in applicability because only a single wavelength can be extracted.

An object of the present invention is to provide a multi-channel optical splitter multiplexer capable of extracting only a desired specific channel signal among multi-channel signals.

In addition, another object of the present invention is to provide a multi-channel optical branch coupling multiplexer capable of varying wavelengths in various forms by the number of channels reflected by the sample grid and the number of Bragg grids.

The object of the present invention is to provide an input terminal for inputting a multi-channel wavelength signal, a branch terminal for outputting a branched signal, a coupling terminal for inputting a signal having the same wavelength as that of the branched signal, and a signal having a wavelength not branched to the branch terminal. A multi-channel optical branch coupling multiplexer comprising an output stage coupled to and output from a coupling stage, comprising: a first circulator for controlling a signal transmission direction between the input stage and the branch stage; A sample grating reflecting the multi-channel wavelength signal inputted through the first circulator; At least one Bragg grid for receiving the multi-channel wavelength signal reflected on the sample grid and reflecting a specific channel wavelength signal among the received multi-channel wavelength signals; And a second circulator for transmitting the signal passing through the Bragg grating and the signal input to the coupling stage to the output stage.

The present invention has the effect of extracting only a desired specific channel signal among the multichannel signals.

In addition, the present invention has the effect that the wavelength can be changed in various forms by the number of channels reflected on the sample grid and the number of Bragg grid (FBG).

In addition, the present invention has the effect of simultaneously extracting one or more channels from the N channel signals.

The terms or words used in this specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best describe their invention. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only one of the most preferred embodiments of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

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

2 is a block diagram showing an embodiment of a multi-channel optical branch coupling multiplexer according to the present invention. Referring to FIG. 2, a multi-channel optical add-drop multiplexer (OADM) according to an embodiment of the present invention includes two four-terminal circulators and light provided between the two circulators. The waveguide chip 220 is included.

The circulator includes a first circulator 211 and a coupling end (add, 203) of the optical branch coupling multiplexer for controlling the signal transmission between the input 201 and the drop 202 of the optical branch coupling multiplexer. It is divided into a second circulator 212 for controlling the signal transmission of the output (204).

Here, the input stage 201 is a stage into which the multi-channel wavelength signal is input in the optical branch coupling multiplexer, the branch stage 202 is a stage where the branched signal is output, and the coupling stage 203 has the same wavelength as the branched signal. Signal is input, and the output terminal 204 is a stage in which the signal input to the coupling end 203 is combined with the signal of the wavelength which is not branched to the branch end 202, and is output.

The first circulator 211 transmits the signal input to the input terminal 201 to the sampled grating 221 of the optical waveguide chip 220, and transmits the signal reflected from the sample grating 221 to the optical waveguide chip. It transmits to the Bragg grid (FBG, Fiber Bragg Grating, 222) of 220, and transmits the signal reflected from the Bragg grid 222 to the branch end (202).

The second circulator 212 combines the signal passed through the Bragg grating 222 and the signal input to the coupling end 203 and transmits the signal to the output end 204, and transmits the signal passing through the sample grid 221 to the output end ( 204).

The optical waveguide chip 220 is provided between the first circulator 211 and the second circulator 212. The optical waveguide chip 220, together with the first circulator 211 and the second circulator 212, combines a multi-channel optical branch. Form a multiplexer.

The optical waveguide chip 220 includes two optical waveguides provided in parallel.

A sample grid 221 is formed in the first optical waveguide, and at least one Bragg grid 222 is formed in the second optical waveguide.

The sample grid 221 reflects the multi-channel wavelength signal input through the first circulator 211, and the signal reflected by the sample grid 221 is the Bragg grid 222 through the first circulator 211. Is delivered to.

The Bragg grating 222 reflects a wavelength signal of a specific channel among the signals reflected on the sample grating 221. By providing the Bragg grating 222 for various wavelengths it is possible to selectively branch the signal of the desired wavelength.

The signal reflected by the Bragg grating 222 is output to the branch end 202 through the first circulator 211.

Meanwhile, the phase shifter 223 provided in the Bragg grating 222 shifts the phase of the center wavelength of the Bragg grating 222 by a predetermined interval, and the wavelength that can be reflected is changed by the Bragg grating 223. The grating 222 does not reflect a signal that has been previously reflected but passes through it as it is. Using this function, only the signal of a specific channel can be reflected and branched.

Here, the phase shifter 223 can be any means that can change the phase of the Bragg grid 222, in particular, implemented by a method such as increasing the Bragg grid 222 by the applied electricity. Can be.

3 is a diagram illustrating wavelengths of a sample grid and a Bragg grid according to the present invention. Referring to FIG. 3, it can be seen that the sample grid 221 reflects the input multi-channel wavelength signal, and the Bragg grid 222 has a form in which each reflects only a signal having a specific wavelength.

The operation of the multi-channel optical branch coupling multiplexer described above is as follows.

First, when the multi-channel wavelength signal is incident through the input terminal 201, the incident multi-channel wavelength signal is incident on the sample grid 221 through the first circulator 211 (S1 of FIG. 2), and the sample grid ( The multi-channel wavelength signal incident on the 221 is reflected by the sample grid 221 having the characteristic of simultaneously reflecting the multi-channel wavelength signal (S2 in FIG. 2). Here, the multi-channel wavelength signal may be, for example, an _N- channel signal having a center wavelength of λ ₁ , λ ₂ , ..., λ _N-1 , λ _N , and a channel spacing of Δλ _C , respectively.

The N-channel signal reflected by the sample grid 221 is incident on the N Bragg grids 222 through the first circulator 211 (S3 of FIG. 2). Here, the N Bragg gratings 222 may have a center wavelength of λ ₁ , λ ₂ ,..., Λ _N-1 , and λ _N , respectively. That is, the N-channel signal reflected on the sample grid 221 is reflected by each Bragg grid 222 reflecting a signal having the same center wavelength, and the reflected signal is branched through the first circulator 211. It branches to 202 (S4 of FIG. 2).

At this time, if one or more channel signals whose center wavelength is λ _I (I = 1, 2, ..., N-1, N) are desired to be reflected, the phase shifter attached to the Bragg grating 222 223 to the center wavelength λ is reflected only the _I channel signal of any particular desired by making the center of the Bragg grating (222) to move the center wavelength by Δλ is the wavelength λ _I -Δλ the Bragg grating (222) using a It can branch (S4 of FIG. 2). That is, the number of Bragg gratings 222 may be reduced, and one or more channels among N channels may be additionally extracted at the same time by only moving a small center wavelength.

The remaining wavelength signal other than the specific channel signal reflected by the Bragg grating 222 passes through the Bragg grating 222 (S5 of FIG. 2). In addition, the remaining channel signals other than the N-channel signals reflected by the sample grid 221 among the multi-channel wavelength signals incident on the initial input terminal 201 are output to the output terminal 204 through the second circulator 212. Is sent to the next node (S6 in FIG. 2).

Meanwhile, the signal reflected and branched by the Bragg grating 222 previously inputs the same signal as the branched signal to the coupling end 203 in order to be used by the next node (Add). The coupling operation (Add) is performed by the same operation principle as the operation of branching a part of the signal of the input terminal 201, the signal input to the coupling terminal 203 is not branched signal passing through the Bragg grid 222 Together with the second circulator 212 is output to the output terminal 204 and transmitted to the next node.

By using the above-described principle, a wavelength-variable multichannel optical splitter multiplexer capable of reconstructing various types of signals can be implemented by the number of channels reflected by the sample grid 221 and the number of Bragg grids 222 used.

4A is a perspective view illustrating an embodiment of an optical waveguide chip according to the present invention, and FIG. 4B is a plan view illustrating an embodiment of the optical waveguide chip according to the present invention. 5A to 5M are process diagrams illustrating a manufacturing process of an optical waveguide chip according to the present invention.

4A through 5M, a plurality of optical waveguide chips 220 may be formed on one wafer.

First, the silicon wafer is cleaned and then SiO ₂ is formed on the silicon wafer to form the bottom clad layer using Flame Hydrolysis Deposition (FHD) or Chemical Vapor Deposition (CVD). Layer 502 is deposited (FIG. 5A).

Next, a GeO ₂ layer 503 is deposited on the SiO ₂ layer 502 to form a core layer to which light is to be guided (FIG. 5B). The core layer is a layer in which an optical waveguide on which the sample grid 221 and the Bragg grid 222 are to be formed is formed.

After the GeO ₂ layer 503 is deposited, the SiO ₂ layer 502 and the GeO ₂ layer 503 are consolidated using a high temperature furnace to form a dense thick film (FIG. 5C).

Next, an Al layer 504 is deposited on the densified GeO ₂ 503 using a sputtering apparatus (FIG. 5D), and a photoresist layer 505 is formed on the deposited Al layer 504, followed by soft baking. (Fig. 5e). After the soft baking is performed, an optical waveguide pattern is formed on the photoresist layer 505 through ultraviolet exposure using a mask (FIGS. 5F and 5G).

Next, the Al layer 504 and the GeO ₂ layer 503 are sequentially etched by dry or wet etching using the photoresist layer 505 having the optical waveguide pattern as a mask (FIGS. 5H and 5I).

The remaining photoresist layer 505 and the Al layer 504 are sequentially removed to form an optical waveguide on which the sample grid 221 and the Bragg grid 222 are to be formed (FIGS. 5J and 5K).

Subsequently, the sample grid 221 and the Bragg grid 222 are formed in the optical waveguide by using the phase mask 506 for forming the sample grid 221 and the Bragg grid 222 (FIG. 5L). The grating formed thus extracts only the desired signal and passes the signal of the unwanted wavelength as it is.

Finally, the upper cladding layer 507 is formed to surround the optical waveguide on which the sample grid 221 and the Bragg grid 222 are formed to form the optical waveguide chip 220 (FIG. 5M).

Although the present invention has been shown and described with reference to the preferred embodiments as described above, it is not limited to the above embodiments and those skilled in the art without departing from the spirit of the present invention. Various modifications and variations are possible without departing from the spirit of the present invention and equivalents of the claims to be described below.

1 is a diagram illustrating a conventional multichannel optical branch coupling multiplexer;

2 is a block diagram showing an embodiment of a multi-channel optical branch coupling multiplexer according to the present invention;

3 is an embodiment illustrating wavelengths of a sample grid and a Bragg grid according to the present invention;

4A is a perspective view illustrating an embodiment of an optical waveguide chip according to the present invention;

4B is a plan view showing an embodiment of an optical waveguide chip according to the present invention;

5A to 5M are process charts illustrating a manufacturing process of an optical waveguide chip according to the present invention.

               <Explanation of symbols for the main parts of the drawings>

201: input stage 202: branch stage 203: coupling stage

204: output stage 211: first circulator 212: second circulator

220: optical waveguide chip 221: sample grid 222: Bragg grid

223: phase shifter 501: silicon substrate 502: SiO ₂

503: GeO ₂ 504: Al 505: photoresist

506: phase mask 507: upper clad layer

Claims (4)

The signal from the coupling end is applied to an input terminal to which a multi-channel wavelength signal is input, a branch terminal to which a branched signal is output, a coupling terminal to which a signal having the same wavelength as the branched signal is input, and a signal having a wavelength that is not branched to the branching terminal. In the multi-channel optical splitting multiplexer including an output coupled to the output, A first circulator for controlling a signal transmission direction between the input terminal and the branch terminal; A sample grating reflecting the multi-channel wavelength signal inputted through the first circulator; At least one Bragg grid for receiving the multi-channel wavelength signal reflected on the sample grid and reflecting a specific channel wavelength signal among the received multi-channel wavelength signals; And And a second circulator for transmitting the signal passing through the Bragg grating and the signal input to the coupling end to the output end, The sample grid and the Bragg grid are implemented by an optical waveguide chip provided on the optical waveguide, and the optical waveguide chip Depositing a SiO ₂ layer on the silicon wafer to form a bottom clad layer; Depositing a GeO ₂ layer for the optical waveguide formed to be formed with the sample gratings and Bragg grating in the SiO ₂ layer; Densifying the SiO ₂ layer and the GeO ₂ layer using a high temperature furnace; Depositing an Al layer on the densified GeO ₂ ; Forming a photoresist layer having an optical waveguide pattern formed on the Al layer; The Al layer and the GeO ₂ layer are sequentially etched using the photoresist layer having the optical waveguide pattern as a mask, and the sample lattice and Bragg lattice are formed by sequentially removing the remaining port resist layer and the Al layer. Forming an optical waveguide; Forming the sample grid and the Bragg grid in the optical waveguide by using a phase mask for forming the sample grid and the Bragg grid; And Forming an upper cladding layer surrounding the optical waveguide on which the sample grid and the Bragg grid are formed; The multi-channel optical branch coupling multiplexer is formed through. The method of claim 1, A phase shifter provided at each Bragg grating to shift the center wavelength of the Bragg grating. Multi-channel optical branch coupling multiplexer further comprising. delete delete

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