KR20020067704A - Wavelength Conversion System using XPM to RZ pattern data - Google Patents

Abstract

PURPOSE: A wavelength conversion system using XPM(Cross-Phase Modulation) for RZ(Return-to-Zero) pattern data is provided to simplify the structure of a system and remarkably reduce the manufacturing cost by executing wavelength conversion, based on XPM, in a single SOA(Semiconductor Optical Amplifier). CONSTITUTION: A wavelength conversion system using XPM for RZ pattern data is composed of a circulator(1), the first optical fiber coupler(2), the second optical fiber coupler(3), an SOA(4), a polarization controller(5), the first filter(6), the second filter(7), an isolator(8), and an optical fiber loop mirror(9). If a CW(Continuous Wave) signal is inputted to the circulator(1), the circulator(1) outputs the CW signal to the first optical fiber coupler(2) without reflection or attenuation. The first optical fiber coupler(2) splits the inputted CW signal into a clockwise CW signal and a counterclockwise CW signal. The clockwise CW signal is inputted to the polarization controller(5). The polarization controller(5) converts the polarization and phase of the inputted CW signal and outputs it to the second optical fiber coupler(3). The second optical fiber coupler(3) couples the clockwise CW signal with an inputted data signal through the isolator(8). If the coupled signal is inputted to the SOA(4), the phase of the clockwise CW signal is changed as a refractivity change is caused in the SOA(4). The first filter(6) removes ASE(Amplified Spontaneous Emission) noises and the data signal from the coupled signal and passes the CW signal only.

Description

Wavelength Conversion System using Cross-Phase Modulation for Zero Return Pattern Data {Wavelength Conversion System using XPM to RZ pattern data}

The present invention relates to a wavelength conversion system using Cross-Phase Modulation (hereinafter referred to as "XPM") for zero-return (return-to-zero) pattern data. More specifically, wavelength conversion using an XPM on the RZ pattern data is performed in a single semiconductor optical amplifier (hereinafter referred to as SOA) to convert the wavelength of the input data signal into an inverted / non-inverted pattern. A system is capable of outputting signals simultaneously and separately.

In general, all-optical wavelength conversion technology capable of improving the performance of an optical communication system by converting an optical signal pulse input at an arbitrary wavelength into an optical signal pulse of another desired wavelength is based on a high-speed information communication network based on a WDM method. It is an essential element technology in constructing an optical exchanger. In particular, XPM has a simple structure and excellent wavelength conversion performance for high-speed data.

1 is a view showing a wavelength conversion system using a conventional XPM.

FIG. 1A shows a wavelength conversion system using two SOAs and three optical fiber couplers having the same gain and input / output characteristics. A continuous wave (CW) signal with a constant power level is distributed by the fiber coupler into two SOAs at the top and bottom, and the top SOA carries the data from the opposite direction as well as the CW signal. The signal is input. As a result, a change in refractive index occurs in the upper SOA, causing a phase change in the CW signal passing therethrough. In the output coupler, the CW signals, which are divided into two paths, interfere with each other to output a wavelength conversion signal having an inversion pattern with respect to the input data signal.

FIG. 1 (b) is a wavelength conversion system using two SOAs, three optical fiber couplers, and one filter having the same gain and input / output characteristics, and operates on the same principle as the system of FIG. However, since the direction of the input data proceeds in the same direction as the CW signal, a filter must be added in front of the output terminal in order to output only the wavelength conversion signal, and the output pattern is also an inversion pattern for the input data signal.

Fig. 1 (c) shows a wavelength conversion system using two SOAs, one optical fiber coupler, one filter, and one circulator having the same gain and input / output characteristics, and one side of each SOA of the system is reflective coated. The CW signal input through the circulator is reflected by the two SOAs. At this time, as shown in FIGS. 1 (a) and 1 (b), a change in refractive index occurs in one SOA by data. In the coupler, interference between two CW signals occurs, and after passing through the circulator, it is sent to the output stage. This method also has a disadvantage in that an inversion pattern for the input data signal is obtained and a filter must be added before the output terminal in order to output only the wavelength conversion signal.

Therefore, in the conventional wavelength conversion system using XPM as shown in Figs. 1 (a), 1 (b) and 1 (c), in order to obtain a wavelength conversion signal having the same pattern as the data input from the output terminal, It requires an additional system to invert the pattern again and requires two SOAs, which are very expensive optical components, which complicates the system structure, increases the manufacturing cost, and requires very great attention in manufacturing due to the nature of the interference structure. have.

Accordingly, the present invention has been proposed to solve the problems of the prior art, and an object of the present invention is to significantly reduce the manufacturing cost with a simple system structure by performing the wavelength conversion by XPM in a single SOA, input data The present invention provides a wavelength conversion system using XPM for RZ pattern data, which can simultaneously and separately output a wavelength conversion signal having an inverted / non-inverted pattern for the signal.

Figure 1 (a) is a block diagram of a wavelength converter using a conventional Mach-Zehnometer interferometer, Figure 1 (b) is a block diagram of a wavelength converter using another conventional Mach-Zehnder interferometer, Figure 1 (c) is Michelson It is a block diagram of a wavelength converter using an interferometer.

2 is a view showing the overall configuration of a wavelength conversion system using XPM for the RZ pattern data according to the present invention.

3 is an overall flowchart of a wavelength conversion method using XPM for RZ pattern data according to the present invention.

Explanation of symbols on the main parts of the drawings

1: circulator 2: first optical fiber coupler

3: second optical fiber coupler 4: SOA

5: Polarization Controller

6: first filter 7: second filter

8: isolator 9: fiber loop mirror

In order to achieve the above object, the present invention, in the optical fiber loop mirror including SOA in the system that can improve the performance of the associated optical communication system by performing a wavelength conversion using the XPM on the RZ pattern data, the input signal A circulator 1 which cyclically outputs the light without reflection or attenuation; A first optical fiber coupler (2) for distributing the CW signal output from the circulator (1) in both directions of the optical fiber loop or for coupling the signals returned from the optical fiber loop; A second optical fiber coupler (3) for coupling the CW signal distributed in the clockwise direction of the optical fiber loop and the input data signal by the first optical fiber coupler (2) to output to the SOA (4); An SOA (4) disposed in the optical fiber loop with an optical distance difference Δx to the left or the right from the first optical fiber coupler (2) to change the phase of the bidirectional CW signal input simultaneously with the data signal; A polarization controller 5 disposed in the optical fiber loop for adjusting the polarization and phase of each CW signal traveling in both directions to remove the dual output signal; First and second tunable filters 6 and 7 capable of removing wavelengths or ASE noise and passing only CW signals; And an isolator 8 for preventing other signals from being directed towards the data signal input.

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

2 is a view showing the overall configuration of a wavelength conversion system using XPM for the RZ pattern data according to the present invention, Figure 3 is a general flow diagram of a wavelength conversion method using XPM for the RZ pattern data according to the present invention.

As shown in FIG. 2, the wavelength conversion system using XPM for RZ pattern data according to the present invention includes a circulator 1, a first optical fiber coupler 2, a second optical fiber coupler 3, and an SOA 4. , A polarization controller 5, a first filter 6, a second filter 7, an isolator 8 and an optical fiber loop mirror 9. Here, the circulator 1 may be replaced with an isolator in order to obtain only a signal having the same pattern as the input data signal.

First, the data signal of the original wavelength and the CW signal of the desired wavelength are inputted through the optical fiber (S10). When the CW signal is input to the circulator 1 through the optical fiber, the circulator 1 cyclically outputs the input CW signal without reflection or attenuation and outputs it to the first optical fiber coupler 2 (S20). The CW signal input to the first optical fiber coupler 2 is divided into a clockwise CW signal and a counterclockwise CW signal (S30).

As shown in FIG. 2, the SOA 4 is disposed in the optical fiber loop with an optical distance difference Δx to the left or the right from the first optical fiber coupler 2, and Δx is a half period of an input data signal having an RZ pattern ( T / 2) is the optical length (however, the duty ratio of the RZ pattern is 50% or less).

By such an arrangement of the SOA 4, the clockwise CW signal and the counterclockwise CW signal simultaneously distributed by the first optical fiber coupler 2 are not affected by the presence or absence of an input data signal in the SOA 4. As a result, different phase shifts occur, and in the following description, the SOA 4 is positioned from the middle of the optical fiber loop mirror to the left side as shown in FIG. 2. Only and are opposite directions, but the basic principle is the same).

First, the divided clockwise CW signal is inputted to the polarization controller 5 to change polarization and phase (S41), and then the data signal inputted through the optical fiber and isolator 8 by the second optical fiber coupler 3. It is coupled (S42). When the clockwise CW signal and the data signal are input to the SOA 4, a refractive index change is caused in the SOA, and the phase of the clockwise CW signal is changed (S43). Then, in the first filter 6, the ASE (Amplified Spontaneous Emission) noise and the data signal output clockwise from the SOA 4 are removed and only the CW signal is passed (S44). Here, the 1st filter 6 may be provided in the optical fiber loop mirror like FIG. 2, and may be provided in the position (1) which is an input / output side of the 1st optical fiber coupler 2. As shown in FIG.

While the clockwise CW signal goes through the above process, the counterclockwise CW signal simultaneously input to the optical fiber loop is input to the SOA 4 after the data signal passes through the SOA 4 due to the optical distance difference of Δx. Therefore, the phase change by the input data signal does not occur with respect to the CW signal in the counterclockwise direction simultaneously input to the optical fiber loop (S45).

The ASE noise from the SOA 4 and the CW signal in the counterclockwise direction can flow into the data input signal through the second optical fiber coupler 3, and to prevent this, an isolator 8 is provided on the data signal input side. It is possible to prevent the ASE noise and the counterclockwise CW signal outputted from the SOA 4 in the counterclockwise direction from being directed toward the data input signal through the second optical fiber coupler 3.

Then, in the second filter 7, the ASE noise output counterclockwise from the SOA 4 is removed and only the CW signal is passed (S46). Here, the 2nd filter 7 may be provided in the optical fiber loop mirror like FIG. 2, and may be provided in the position (2) which is an input / output side of the 1st optical fiber coupler 2. As shown in FIG.

Then, the CW signal in the counterclockwise direction is input to the polarization controller 5, and since the polarization controller 5 can change the phase of the signal differently according to the direction of the input signal, the CW signal in the counterclockwise direction The clock signal undergoes a phase change different from that of the CW signal (S47).

On the other hand, while the input data signal and the clockwise CW signal pass through the SOA 4, the counterclockwise CW signal that has been previously input (pre-input) into the optical fiber loop also passes through the SOA 4 at the same time. As a result, a phase change occurs in the CW signal in the line input counterclockwise direction, and the CW signal in the line input clockwise direction and the CW signal in the line input counterclockwise direction interfere with each other in the first optical fiber coupler 2 to output an unwanted dual data signal. Can be. However, this dual data output can be eliminated by adjusting the phase change caused by the pre-input counterclockwise CW signal by the adjustment of the polarization controller 5.

Then, the clockwise CW signal and the counterclockwise CW signal are interfered by the first optical fiber coupler 2 so that the wavelength conversion signal representing the inversion pattern with respect to the input data signal is connected to the terminal ① of the first optical fiber coupler. Thus, the wavelength conversion signal having the same (non-inverting) pattern as the input data signal is output to terminal ② of the first optical fiber coupler (S50).

The circulator 1 circulates the wavelength conversion signal of the inversion pattern with respect to the input data signal without reflection or attenuation (S61), and the wavelength conversion signal of the inversion pattern with respect to the input data signal is output to the output terminal of the circulator 1. (S62).

On the other hand, at the terminal ② of the first optical fiber coupler 2, the wavelength conversion signal of the non-inverting pattern (same pattern) with respect to the input data signal is obtained (S63).

Table 1 and Table 2 below show the phase change of the clockwise CW signal and the counterclockwise CW signal inputted to the optical fiber loop, respectively. According to the phase change is indicated. In the table Wow Is the total amount of phase change experienced by the CW and counterclockwise CW signals in the optical fiber, respectively.

However, I is when there is a data signal in the SOA 4, II is when there is no data signal in the SOA 4, to be.

However, III is when there is no data signal in the SOA 4, IV is when there is a data signal in the SOA 4, to be.

In addition, as described above, in order to remove the unwanted dual data output, the polarization controller 5 is adjusted to satisfy the following condition (1).

Equation 1 is the total phase change of condition II-total phase change of condition IV = , In other words, Can be obtained using the equation.

When the condition of Equation 1 is satisfied, only a single SOA 4 can be used to simultaneously obtain wavelength converted signals each having an inverted / non-inverted pattern for the input data signal.

In addition, by appropriate adjustment of the polarization controller 5, wavelength conversion is possible not only for the input data of the RZ pattern but also for the input data pattern of Non Return-to-Zero (NRZ).

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Therefore, according to the present invention, unlike the conventional wavelength conversion system, by performing the wavelength conversion by XPM in a single SOA, the manufacturing cost can be drastically reduced due to the simple system structure. It can be easily applied to all-optical wavelength converter of optical exchange system and WDM network. In addition, the wavelength conversion signal having an inverted / non-inverted pattern with respect to the input data signal can be output simultaneously and separately, and the polarization controller can improve the interference efficiency, thereby reducing the dependence on the refractive index change of the SOA. It can reduce the optical power.

Claims (4)

In the system that can improve the performance of the related optical communication system by performing wavelength conversion using XPM on the RZ pattern data in the optical fiber loop mirror including SOA, A circulator 1 which cyclically outputs an input signal without reflection or attenuation; A first optical fiber coupler (2) for distributing the CW signal output from the circulator (1) in both directions of the optical fiber loop or for coupling the signals returned from the optical fiber loop; A second optical fiber coupler (3) for coupling the CW signal distributed in the clockwise direction of the optical fiber loop and the input data signal by the first optical fiber coupler (2) to output to the SOA (4); An SOA (4) disposed in the optical fiber loop with an optical distance difference Δx to the left or the right from the first optical fiber coupler (2) to change the phase of the bidirectional CW signal input simultaneously with the data signal; A polarization controller 5 disposed in the optical fiber loop for adjusting the polarization and phase of each CW signal traveling in both directions to remove the dual output signal; First and second tunable filters 6 and 7 capable of removing wavelengths or ASE noise and passing only CW signals; And A wavelength conversion system using XPM for RZ pattern data, characterized in that it comprises an isolator (8) for preventing other signals from being directed towards the data signal input. The wavelength conversion system using XPM for RZ pattern data according to claim 1, wherein the circulator (1) can be replaced with an isolator when only the CW signal having the same pattern as the input data signal is obtained. The clock of claim 1, wherein the first optical fiber coupler 2 distributes the CW signal output from the circulator 1 into a clockwise CW signal and a counterclockwise CW signal or returns through the optical fiber loop. RZ pattern, characterized in that a component of the optical fiber loop mirror 9 for coupling the CW signal in the direction and the CW signal in the counterclockwise direction to output the wavelength conversion signal of the inverted / non-inverted pattern with respect to the input data signal, respectively. Wavelength conversion system using XPM for data. The method according to claim 1, wherein the polarization controller 5 changes the phase of the signal according to the direction of the input signal to improve the interference efficiency and removes the dual output signal. Wavelength conversion system used.