KR102267251B1 - Tunable laser apparatus and driving method thereof - Google Patents

Abstract

The present invention relates to a tunable laser device capable of improving laser characteristics.
A tunable laser device according to an embodiment of the present invention comprises: a gain unit for outputting an optical signal; a first diffraction grating reflector positioned at one side of the gain unit and reflecting the optical signal at a first wavelength interval; a second diffraction grating reflector positioned on the other side of the gain unit and reflecting the optical signal at a second wavelength interval; An optical filter is disposed between the gain unit and the second diffraction grating reflector and controls so that only an optical signal having a third wavelength interval is output.

Description

Tunable laser device and driving method thereof

An embodiment of the present invention relates to a tunable laser device and a driving method thereof, and in particular, to a tunable laser device and a driving method thereof to improve laser characteristics.

In general, when a laser light source that outputs a single wavelength is used, the number of laser light sources is required as much as the number of each channel, so that the wavelength resource cannot be efficiently used in the optical communication system. Accordingly, in an optical communication system such as Dense Wavelength Division Multiplexing (DWDM), a tunable laser device capable of changing a wavelength is required in order to efficiently use a wavelength resource.

Accordingly, the present invention is to provide a tunable laser device capable of outputting a laser having a narrow line width without a wavelength locker and a driving method thereof.

In addition, another object of the present invention is to provide a tunable laser device capable of long-distance transmission as well as short-distance transmission, which can be used in both amplitude modulation method and phase modulation method, and a driving method thereof.

A tunable laser device according to an embodiment of the present invention comprises: a gain unit for outputting an optical signal; a first diffraction grating reflector positioned at one side of the gain unit based on the movement path of the optical signal and reflecting the optical signal at a first wavelength interval; a second diffraction grating reflector positioned on the other side of the gain unit based on the movement path of the optical signal and reflecting the optical signal at a second wavelength interval; An optical filter is positioned between the gain unit and the second diffraction grating reflector and controls so that only an optical signal having a third wavelength interval is output.

According to an embodiment, the first wavelength interval, the second wavelength interval, and the third wavelength interval are set to be different.

According to an embodiment, the first diffraction grating reflector is located above one end of the tunable laser device, and the second diffraction grating reflector is located below the one end of the tunable laser device.

According to an embodiment, the optical filter is a ring resonator.

According to an embodiment, the optical filter includes a curved waveguide; a first optical coupler for coupling the linear waveguide connected to the gain unit and the curved waveguide; a second optical coupler for coupling the straight waveguide connected to the second diffraction grating reflector and the curved waveguide; and an optical filter phase part for changing a wavelength position of the optical filter.

According to an embodiment, it further includes an optical coupler for combining the first optical signal supplied from the first diffraction grating reflector and the second optical signal supplied from the second diffraction grating reflector.

According to an embodiment, it is positioned between the first diffraction grating reflector and the optical coupler, the first optical amplifier for amplifying the first optical signal; It is positioned between the second diffraction grating reflector and the optical coupler, and further includes a second optical amplifier for amplifying the second optical signal.

a first Mach-Zehnder optical modulator arm positioned between the first optical amplifier and the optical coupler and controlling a phase of the first optical signal; It further includes a second Mach-Zehnder optical modulator arm positioned between the second optical amplifier and the optical coupler, for controlling a phase of the second optical signal.

A method of driving a tunable laser device according to an embodiment of the present invention comprises the steps of outputting an optical signal, reflecting the optical signal at a first wavelength interval using a first diffraction grating reflector, and a second diffraction grating reflector Reflecting the optical signal at a second wavelength interval by using , and controlling so that only the optical signal of the third wavelength interval is output using a ring resonator positioned between the first and second diffraction grating reflectors including the steps of

According to an embodiment, the first wavelength interval, the second wavelength interval, and the third wavelength interval are set to be different.

According to an embodiment, the method further includes combining the first optical signal output from the first diffraction grating reflector and the second optical signal output from the second diffraction grating reflector using an optical coupler.

According to an embodiment, the method further includes amplifying the first optical signal and the second optical signal.

According to an embodiment, the method further includes controlling a phase of at least one of the first optical signal and the second optical signal.

According to the tunable laser device and its driving method according to an embodiment of the present invention, an optical filter (ie, a ring resonator) is installed between the first diffraction grating reflector and the second diffraction grating reflector to increase the resonance distance, and thus The line width of the laser can be minimized. In addition, in the present invention, the optical filter performs the role of a transmission filter having a fine wavelength width, and thus the wavelength locker can be removed.

1 is a view showing a tunable laser device according to a first embodiment of the present invention.
2 is a view showing an embodiment of a method of driving a tunable laser device according to an embodiment of the present invention.
3 is a view showing a tunable laser device according to a second embodiment of the present invention.
4 is a view showing a tunable laser device according to a third embodiment of the present invention.
5 is a view showing a tunable laser device according to a fourth embodiment of the present invention.

Hereinafter, embodiments of the present invention and other matters necessary for those skilled in the art to easily understand the contents of the present invention will be described in detail with reference to the accompanying drawings. However, since the present invention can be embodied in various different forms within the scope of the claims, the embodiments described below are merely exemplary regardless of whether they are expressed or not.

That is, the present invention is not limited to the embodiments disclosed below, but may be implemented in a variety of different forms, and in the following description, when a part is connected to another part, it is directly connected In addition, it includes a case in which another element is electrically connected therebetween. In addition, it should be noted that the same elements in the drawings are denoted by the same reference numbers and symbols as much as possible even though they are indicated in different drawings.

For long-distance optical transmission, optical signals must be modulated. In general, in an optical communication system such as DWDM, an amplitude modulation method for determining 1 or 0 using the presence or absence of an optical signal is used as a high-speed optical modulation method. In the amplitude modulation method, an optical signal output from a laser device is modulated using an external light absorption modulator (EAM) or an external Mach-Zhender modulator. However, in the amplitude modulation method, the width of the laser spectrum increases as the modulation rate increases. This increase in the width of the laser spectrum not only increases the noise power, but also limits the transmission distance due to the chromatic dispersion problem of the optical fiber.

A phase modulation method may be introduced to increase the transmission speed while overcoming the disadvantages of the amplitude modulation method. The most representative phase modulation method is differential phase shift keying (DPSK), which determines 0 degrees and 180 degrees to determine 1 or 0. However, since the phase modulation method is sensitive to phase noise, a laser having a very narrow line width is required.

On the other hand, the tunable laser device is configured to provide a gain by using two reflectors for laser resonance, and placing an optical gain part between the two reflectors. At this time, the distance between the two reflectors becomes a resonance distance (Cavity length). The optical communication system using the phase modulation method requires a laser light source with a very narrow line width, and the line width of the laser becomes narrower as the resonance distance for constituting the laser increases. Therefore, the optical communication system using the phase modulation method requires a tunable laser device with a long resonance distance.

Additionally, it is very important to keep the output wavelength of the laser constant in the tunable laser device. Currently, a wavelength locker is positioned at the output end of the tunable laser device to keep the output wavelength of the laser constant. The wavelength locker is a filter with a specific wavelength interval and controls the output wavelength. However, the wavelength locker has a complex structure and is bulky. Therefore, there is a need for a method capable of outputting a constant wavelength without a wavelength locker.

1 is a view showing a tunable laser device according to a first embodiment of the present invention.

1, a tunable laser device 100 according to a first embodiment of the present invention includes a first diffraction grating reflector 102, a second diffraction grating reflector 104, a phase unit 106, a gain unit ( 108) and an optical filter 110.

The gain unit 108 outputs an optical signal. For example, the gain unit 108 may output an optical signal in response to the electrical signal.

The first diffraction grating reflector 102 is located above one end of the tunable laser device 100 , and the second diffraction grating reflector 104 is located at the lower end of one end of the tunable laser device 100 . Here, the first diffraction grating reflector 102 may output a first optical signal, and the second diffraction grating reflector 104 may output a second optical signal. The first and second optical signals output from the first diffraction grating reflector 102 and the second diffraction grating reflector 104 are used as a laser of the tunable laser device 100 .

The first diffraction grating reflector 102 is positioned on one side of the gain unit 108 based on the movement path of light, and reflects the optical signal from the gain unit 108 at first wavelength intervals.

The second diffraction grating reflector 104 is located on the other side of the gain unit 108 with respect to the movement path of light, and reflects the optical signal from the gain unit 108 at a second wavelength interval different from the first wavelength interval. .

The first diffraction grating reflector 102 and the second diffraction grating reflector 104 oscillate the laser while resonating with each other. That is, the first diffraction grating reflector 102 and the second diffraction grating reflector 104 are used as reflection filters, and the first reflection wavelength of the first diffraction grating reflector 102 and the second diffraction grating reflector 104 are used. The laser may be output as a single wavelength at the matching wavelength among the two reflected wavelengths.

Additionally, when the first diffraction grating reflector 102 and the second diffraction grating reflector 104 are used as a reflection filter, the wavelength tunable range is widened by the Vernier effect. For example, the wavelength may be varied by varying the reflected wavelengths of the first diffraction grating reflector 102 and the second grating reflector 104 with power and/or a heater.

The phase unit 106 controls the phase of the laser.

The optical filter 110 controls so that only the wavelengths of the third wavelength interval are output. To this end, the optical filter 110 may be configured as a ring resonator.

The optical filter 110 includes optical couplers 112a and 112b , a curved waveguide 114 , and an optical filter phase unit 116 .

The first optical coupler 112a is positioned between the first straight waveguide 120a and the curved waveguide 114 . The first optical coupler 112a transmits light between the first straight waveguide 120a and the curved waveguide 114 . For example, the first optical coupler 112a transmits the light from the first straight waveguide 120a to the curved waveguide 114 or transmits the light from the curved waveguide 114 to the first straight waveguide 120a. . Additionally, the first straight waveguide 120a is used as a passage of light between the gain section 108 , the phase section 106 and the first diffraction grating reflector 102 and the curved waveguide 114 .

The second optical coupler 112b is positioned between the second straight waveguide 120b and the curved waveguide 114 . The second optical coupler 112b transmits light between the second straight waveguide 120b and the curved waveguide 114 . For example, the second optical coupler 112b transmits the light from the second straight waveguide 120b to the curved waveguide 114 or transmits the light from the curved waveguide 114 to the second straight waveguide 120b. . Additionally, the second straight waveguide 120b is used as a passage of light between the second diffraction grating reflector 104 and the curved waveguide 114 .

The curved waveguide 114 is formed in a ring shape and is used as a light path.

The optical filter phase unit 116 is used to change the wavelength position of the optical filter 110 while maintaining the third wavelength interval. For example, the desired third wavelength interval is set to 1550 nm, 1550.4 nm, 1550.8 nm, ..., and the third wavelength interval of the optical filter 110 is 1549.9 nm, 1550.3 nm, 1550.7 nm, ... can be set to In this case, the position of the wavelength may be varied by 0.1 nm while maintaining the third wavelength interval by applying electric power or heat by a heater to the optical filter phase unit 116 .

The above-described optical filter 110, that is, the third wavelength interval of the ring resonator is determined by the total length, that is, the total length of the ring resonator composed of the optical coupler 112, the curved waveguide 114, and the optical filter phase unit 116. do. In this case, the optical filter 110 functions as a transmission filter while resonating by the length of the ring.

Meanwhile, when the optical filter 110 is installed between the first diffraction grating reflector 102 and the second diffraction grating reflector 104 as in the present invention, the resonance distance is increased to minimize the line width of the laser. In addition, since the optical filter 110 serves as a transmission filter having a fine wavelength width, it is possible to remove the wavelength locker. In other words, in the present invention, the optical filter 110 performs the function of a wavelength locker.

2 is a view showing an embodiment of a method of driving a tunable laser device according to an embodiment of the present invention.

Referring to FIG. 2, the first diffraction grating reflector 102 is set to a first wavelength interval dλ1 as shown in (a) of FIG. 2, and the second diffraction grating reflector 104 is shown in FIG. As shown in b), the second wavelength interval dλ2 is set. Here, although FIG. 2 shows that the second wavelength interval dλ2 is longer than the first wavelength interval dλ1 for convenience of explanation, the present invention is not limited thereto. Actually, the first wavelength interval dλ1 and the second wavelength interval dλ2 may be variously set.

The optical filter 110 is set to a third wavelength interval dλ3 as shown in FIG. 2C. Here, the third wavelength interval dλ3 is set to be different from the first wavelength interval dλ1 and the second wavelength interval dλ2.

Additionally, (d) and (e) of Figure 2 shows the output wavelength of the laser output from the tunable laser device (100).

When the operation process is described in detail, the first diffraction grating reflector 102 reflects light at a first wavelength interval dλ1, and the second diffraction grating reflector 104 reflects light at a second wavelength interval dλ1. The first diffraction grating reflector 102 and the second diffraction grating reflector 104 oscillate the laser while resonating with each other. At this time, the first diffraction grating reflector 102 and the diffraction grating reflector 104 are used as a reflection filter, and thus the wavelength variable range is widened by the vernier effect. Additionally, when the reflected wavelengths of the first diffraction grating reflector 102 and the second diffraction grating reflector 104 are varied with power and/or a heater, the position of the wavelength may be moved from x to y.

On the other hand, when the first diffraction grating reflector 102 and the second diffraction grating reflector 104 are used as reflection filters, the reflected wavelength has a wide width of approximately 1 nm. On the other hand, in the case of the optical filter 110 composed of a ring resonator, the width of the wavelength is finely set in response to the ring resonance characteristic. Accordingly, in the present invention in which the optical filter 110 serves as a transmission filter, the laser is set to have a fine wavelength in response to the filter characteristics of the optical filter 110 .

In other words, when the wavelengths of the first diffraction grating reflector 102, the second diffraction grating reflector 104 and the optical filter 110 match as shown in FIG. The wavelength is output as an output wavelength, thereby improving the characteristics of the laser. Additionally, when the wavelengths of the first diffraction grating reflector 102 and the second diffraction grating reflector 104 are moved to the y position, the wavelength corresponding to the y position is output as an output wavelength. Here, the output wavelength may be output as a first optical signal via the first diffraction grating reflector 102 and a second optical signal via the second diffraction grating reflector 104 .

Additionally, in the present invention, the optical filter 110 may replace the wavelength locker by being integrated in the tunable laser device 100 . In addition, by designing and manufacturing the third wavelength interval (dλ3) of the optical filter 110 to match the ITU-grid, only the wavelength matching the ITU-grid may be oscillated.

3 is a view showing a tunable laser device according to a second embodiment of the present invention. When describing FIG. 3, the same reference numerals are assigned to the same components as those of FIG. 1, and detailed descriptions thereof will be omitted.

Referring to FIG. 3 , the tunable laser device 100 according to the second embodiment of the present invention includes a first diffraction grating reflector 102 , a second diffraction grating reflector 104 , a phase unit 106 , and a gain unit ( 108), an optical filter 110 and an optical coupler 130 are provided.

The optical coupler 130 is connected to the first diffraction grating reflector 102 and the second diffraction grating reflector 104 . The optical coupler 130 combines and outputs the first optical signal supplied from the first diffraction grating reflector 102 and the second optical signal supplied from the second diffraction grating reflector 104 . When the first optical signal and the second optical signal are combined by the optical coupler 130, the power of the light (ie, the power of the laser) is increased.

4 is a view showing a tunable laser device according to a third embodiment of the present invention. When explaining FIG. 4, the same reference numerals are assigned to the same components as those of FIG. 3, and detailed descriptions thereof will be omitted.

4, the tunable laser device 100 according to the third embodiment of the present invention is a first diffraction grating reflector 102, a second diffraction grating reflector 104, a phase unit 106, a gain unit ( 108 ), an optical filter 110 , a first optical amplifier 140 , a second optical amplifier 142 , and an optical coupler 130 .

The first optical amplifier 140 is positioned between the first diffraction grating reflector 102 and the optical coupler 130 . The first optical amplifier 140 amplifies the first optical signal from the first diffraction grating reflector 102 and supplies the amplified first optical signal to the optical coupler 130 .

The second optical amplifier 142 is positioned between the second diffraction grating reflector 104 and the optical coupler 130 . The second optical amplifier 142 amplifies the second optical signal from the second diffraction grating reflector 104 and supplies the amplified second optical signal to the optical coupler 130 .

The optical coupler 130 combines and outputs the amplified first optical signal supplied from the first optical amplifier 140 and the amplified second optical signal supplied from the second optical amplifier 142 . In this case, a high-power laser can be generated.

5 is a view showing a tunable laser device according to a fourth embodiment of the present invention. When describing FIG. 5, the same reference numerals are assigned to the same components as those of FIG. 4, and detailed descriptions thereof will be omitted.

5, the tunable laser device 100 according to the fourth embodiment of the present invention is a first diffraction grating reflector 102, a second diffraction grating reflector 104, a phase unit 106, a gain unit ( 108), optical filter 110, first optical amplifier 140, second optical amplifier 142, first Mach-Zehnder modulator arm (150), second Mach-Zehnder optical modulator arm ( 152) and an optical coupler 130.

The first Mach-Zehnder optical modulator arm 150 is positioned between the first optical amplifier 140 and the optical coupler 130 . The first Mach-Zehnder optical modulator arm 150 controls the phase of the first optical signal.

The second Mach-Zehnder optical modulator arm 152 is positioned between the second optical amplifier 142 and the optical coupler 130 . The second Mach-Zehnder optical modulator arm 152 controls the phase of the second optical signal.

That is, the first Mach-Zehnder optical modulator arm 150 and the second Mach-Zehnder optical modulator arm 152 control the phases of the first optical signal and the second optical signal. When the phases of the first optical signal and the second optical signal from the first Mach-Zehnder optical modulator arm 150 and the second Mach-Zehnder optical modulator arm 152 are not modulated, the first optical signal and the second optical signal having the same phase The optical signals are combined in the optical coupler 130 and output. On the other hand, when the phase difference between the first optical signal and the second optical signal is set to 180 degrees using at least one of the first Mach-Zehnder optical modulator arm 150 and the second Mach-Zehnder optical modulator arm 152, the destructive interference Accordingly, the optical signal is not output from the optical coupler 130 . That is, the first Mach-Zehnder optical modulator arm 150 and the second Mach-Zehnder optical modulator arm 152 serve as Mach-Zehnder optical modulators.

Although the technical spirit of the present invention has been specifically described according to the above preferred embodiments, it should be noted that the above-described embodiments are for explanation and not for limitation. In addition, those of ordinary skill in the art will understand that various modifications are possible within the scope of the technical spirit of the present invention.

The scope of the above-described invention is defined in the following claims, and is not limited by the description of the main text of the specification, and all modifications and changes within the scope of equivalents of the claims will belong to the scope of the present invention.

100: tunable laser device 102, 104: diffraction grating reflector
106: phase part 108: gain part
110: optical filter 112a, 112b, 130: optical coupler
114: curved waveguide 116: optical filter phase part
120a, 120b: straight waveguide 140, 142: optical amplifier
150,152 : Mach-Zehnder light modulator arm

Claims (13)

a gain unit for outputting an optical signal;
a first diffraction grating reflector positioned at one side of the gain unit based on the movement path of the optical signal and reflecting the optical signal at a first wavelength interval;
a second diffraction grating reflector positioned on the other side of the gain unit based on the movement path of the optical signal and reflecting the optical signal at a second wavelength interval;
an optical filter positioned between the gain unit and the second diffraction grating reflector and controlling so that only an optical signal of a third wavelength interval is output;
The tunable laser device, characterized in that the first wavelength interval, the second wavelength interval, and the third wavelength interval are set to be different.
delete The method of claim 1,
The first diffraction grating reflector is located above one end of the tunable laser device,
The second diffraction grating reflector is a tunable laser device, characterized in that located below one end. The method of claim 1,
The optical filter is a tunable laser device, characterized in that the ring resonator. The method of claim 1,
The optical filter is
with curved waveguides;
a first optical coupler for coupling the straight waveguide connected to the gain unit and the curved waveguide;
a second optical coupler for coupling the straight waveguide connected to the second diffraction grating reflector and the curved waveguide;
A tunable laser device comprising an optical filter phase part for varying the wavelength position of the optical filter. The method of claim 1,
The tunable laser device further comprising an optical coupler for combining the first optical signal supplied from the first diffraction grating reflector and the second optical signal supplied from the second diffraction grating reflector. 7. The method of claim 6,
a first optical amplifier positioned between the first diffraction grating reflector and the optical coupler and configured to amplify the first optical signal;
The tunable laser device, positioned between the second diffraction grating reflector and the optical coupler, further comprising a second optical amplifier for amplifying the second optical signal. 8. The method of claim 7,
a first Mach-Zehnder optical modulator arm positioned between the first optical amplifier and the optical coupler and configured to control a phase of the first optical signal;
and a second Mach-Zehnder optical modulator arm positioned between the second optical amplifier and the optical coupler to control a phase of the second optical signal. outputting an optical signal;
using a first diffraction grating reflector to reflect the optical signal at a first wavelength interval;
using a second diffraction grating reflector to reflect the optical signal at a second wavelength interval;
using a ring resonator positioned between the first diffraction grating reflector and the second diffraction grating reflector to control so that only the optical signal of the third wavelength interval is output,
The method of driving a tunable laser device, characterized in that the first wavelength interval, the second wavelength interval, and the third wavelength interval are set to be different.
delete 10. The method of claim 9,
Driving the tunable laser device, characterized in that it further comprises combining the first optical signal output from the first diffraction grating reflector and the second optical signal output from the second diffraction grating reflector using an optical coupler Way. 12. The method of claim 11,
The method of driving a tunable laser device, characterized in that it further comprises the step of amplifying the first optical signal and the second optical signal. 12. The method of claim 11,
The method of driving a tunable laser device, characterized in that it further comprises the step of controlling the phase of at least one of the first optical signal and the second optical signal.

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