WO2023128261A1 - Wavelength-selective laser system using mems mirror array - Google Patents

Abstract

A wavelength-selective laser system according to the present invention comprises a wavelength-selective switch which generates and outputs laser oscillation by dispersing a broadband wavelength emitted from an optical fiber amplifier by means of a diffraction grating and selectively feeding back only a specific wavelength. The wavelength-selective switch comprises the diffraction grating and a MEMS mirror array. The diffraction grating nonlinearly disperses the broadband wavelength emitted from the optical fiber amplifier into multiple wavelength channels. The MEMS mirror array comprises multiple MEMS mirrors nonlinearly arranged to correspond to the multiple wavelength channels nonlinearly dispersed by a diffraction grating. The MEMS mirror array generates laser resonance by selectively reflecting only a specific wavelength channel among the multiple wavelength channels that are input to the multiple MEMS mirrors.

Description

Wavelength selective laser system using MEMS mirror array

The present invention relates to a wavelength selective laser system, and more particularly, to a wavelength selective laser system using a micro electro mechanical system (MEMS) mirror array having a nonlinear arrangement structure.

For broadband optical communication, WDM (Wavelength Division Multiplexing) technology for simultaneously transmitting and receiving optical signals of various wavelengths through one optical cable is used. Recently, with the advancement of WDM technology, Dense Wavelength Division Multiplexing (DWDM) technology is being used for a wider bandwidth.

A wavelength channel for optical communication using DWDM technology is recommended in the ITU-T DWDM Grid standard and enables high-speed communication through this. For example, the wavelength band according to the ITU-T DWDM Grid standard includes wavelength bands used in broadband optical communication, such as C-band (1530-1565 nm), L-band (1565-1625 nm), and O-band (1260-1360 nm).

For high-performance implementation of DWDM technology for such broadband optical communication, a wavelength selective laser system equipped with a wavelength selective switch (WSS) conforming to the Grid standard is required.

Here, the wavelength selection switch refers to a device capable of quickly selecting and outputting a laser having a desired wavelength freely from a multi-wavelength channel laser light source. With the introduction of such a wavelength selection switch, the user can provide a laser light source of a desired wavelength as needed, such as diagnosing a mesh network and providing an emergency light source.

The wavelength selection switch operates by dividing an input signal of a multi-wavelength channel by wavelength and then operating a switch for selecting a wavelength to determine an output wavelength. A bulk optical system is used for wavelength branching and combining in a wavelength selection switch, and MEMS (Micro Electro Mechanical System), LC (Liquid Crystal), LCoS (Liquid Crystal on Silicon), etc. are mainly used as switching engines.

Among switching engines, a MEMS mirror array or scanning mirror array (SMA) manufactured by a MEMS process is fabricated from silicon using a wafer-scale lithography process used in the semiconductor industry. In the MEMS mirror array, each mirror angle can be tilted by an electrical method, that is, an electrostatic attraction, so that a light path reflected from each mirror can be controlled.

Ordinary wavelength selective laser disperses the incident wavelength signal in a wide band using a diffraction grating, and selectively reflects the wavelength by the MEMS mirror at the position where it is dispersed according to each wavelength and returns to the laser gain material to form a laser resonator. Formation, causing laser oscillation of the desired wavelength. However, the dispersion by the diffraction grating is distributed at non-linear intervals because the angle is not constant according to the wavelength. However, if the MEMS mirrors that select the wavelength are arranged at regular intervals as in the past, a laser with a wavelength that does not exactly meet the international standard for DWDM optical communication systems (ITU ITU-T DWDM Grid standard) is selected and output, which falls short of the standard. or cause noise in optical communication.

[Prior art literature]

[Patent Literature]

Registered Patent Publication No. 10-1646289 (2016.08.05. Notice)

Accordingly, an object of the present invention is to provide a wavelength selective laser system using a MEMS mirror array having a nonlinear arrangement structure in consideration of the characteristics of a wavelength band in which a wideband optical signal is nonlinearly dispersed.

In order to achieve the above object, the present invention is an optical fiber amplifier having a broadband gain distribution; A diffraction grating for dispersing into a plurality of wavelength channels spatially arranged according to wavelengths; and a plurality of MEMS mirrors nonlinearly arranged to correspond to the plurality of wavelength channels nonlinearly dispersed by the diffraction grating, wherein only a specific wavelength channel among the plurality of wavelength channels input to the plurality of MEMS mirrors. Provides a wavelength selection switch for a wavelength-selective laser system comprising a; MEMS mirror array that selectively reflects and causes laser resonance.

The wavelength selection switch according to the present invention collects broadband spectrum emitted from an optical fiber amplifier, which is a feedback structure component of a laser resonator, into parallel light and transmits it to the diffraction grating, or transmits light of a specific wavelength selected from the MEMS mirror array. an input/output optical collimator that collects and transmits the light to an optical fiber amplifier; and an optical system for transmitting lasers of a plurality of wavelength channels nonlinearly dispersed by the diffraction grating to the MEMS mirror array in parallel.

The optical fiber amplifier may have at least one wavelength band among C-band (1530 to 1565 nm), L-band (1565 to 1625 nm) and O-band (1260 to 1360 nm), and an optical fiber gain medium and optical fiber of any other wavelength band. Instead of a shape, an optical gain medium in a bulk form such as SOA (Semiconductor Optical Amplifier) can also be used.

The central wavelength of the outputted laser is determined by calculating an optical path that is dispersed in the diffraction grating and incident on the MEMS mirror array, and an array of the plurality of MEMS mirrors may be designed according to the determined optical path.

The diffraction grating disperses the laser such that a wavelength interval between wavelength channels becomes nonlinearly longer as the wavelength of the laser becomes longer.

The plurality of MEMS mirrors may be disposed so that the intervals between the MEMS mirrors are nonlinearly increased to correspond to the wavelength intervals of the wavelength channels that are nonlinearly lengthened.

The MEMS mirror array may further include a plurality of electrostatic actuators for independently oscillating the plurality of MEMS mirrors in a uniaxial direction.

In the MEMS mirror arrangement, the plurality of MEMS mirrors may be arranged in a line, and the plurality of electrostatic actuators may be alternately connected up and down to the plurality of MEMS mirrors in the uniaxial direction, respectively.

The MEMS mirror may be formed in a rectangular shape, the electrostatic driver may be connected to one side of a short side in the 1-axis direction, and a line width of a laser selected by a width of the short side may be determined.

The line width of the output laser may be determined by calculating an optical path that is dispersed in the diffraction grating and incident on the MEMS mirror array, and the widths of the plurality of MEMS mirrors may be designed according to the determined optical path.

And the present invention provides a wavelength selective laser system including; the wavelength selection switch for selectively outputting the laser of a specific wavelength channel that meets laser resonance conditions using a broadband optical gain medium.

According to the present invention, since the MEMS mirror array has a nonlinear arrangement structure in consideration of the characteristics of a wavelength band in which a broadband optical signal (laser) is nonlinearly dispersed, it is possible to accurately select and output a desired channel wavelength. That is, by calculating an optical path where the broadband laser is dispersed in the diffraction grating and incident on the MEMS mirror array, and arranging the MEMS mirrors on the calculated optical path, the MEMS mirror array accurately selects the wavelength of the desired channel from the incident broadband laser. You can choose to print.

In addition, the MEMS mirror array according to the present invention can easily adjust the line width of the laser output by adjusting the width of the MEMS mirror. That is, the MEMS mirror can output a laser with a wide line width if the width of the MEMS mirror is wide, and can output a laser with a narrow line width if the width of the MEMS mirror is narrow.

1 is a block diagram showing a wavelength selective laser system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a wavelength selection switch of FIG. 1 .

FIG. 3 is an exemplary diagram illustrating a process of selecting and outputting a specific wavelength from the wavelength selection switch of FIG. 2 .

FIG. 4 is a plan view showing the MEMS mirror array of FIG. 2 .

FIG. 5 is an enlarged view of the MEMS mirror of FIG. 4 .

FIG. 6 is an exemplary view showing a change in the line width of an output laser according to the line width of the MEMS mirror of FIG. 5 .

7 is a graph showing an array of MEMS mirrors according to wavelengths dispersed in a specific band according to an experimental example.

It should be noted that in the following description, only parts necessary for understanding the embodiments of the present invention are described, and descriptions of other parts will be omitted without departing from the gist of the present invention.

The terms or words used in this specification and claims described below should not be construed as being limited to ordinary or dictionary meanings, and the inventors have appropriately used the concept of terms to describe their inventions in the best way. It should be interpreted as a meaning and concept consistent with the technical spirit of the present invention based on the principle that it can be defined in the following way. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent all of the technical spirit of the present invention, so various equivalents that can replace them at the time of the present application. It should be understood that there may be variations and variations.

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

1 is a block diagram showing a wavelength selective laser system according to an embodiment of the present invention.

Referring to FIG. 1 , the wavelength-selective laser system 100 according to the present embodiment includes a wavelength-selective switch 30 that receives broadband laser and selectively outputs laser of a specific wavelength channel. The wavelength selective laser system 100 according to this embodiment includes an optical fiber amplifier 10, an optical coupler 20, a wavelength selection switch 30, and a controller 90.

The optical fiber amplifier 10 provides sufficient optical gain for laser oscillation over a wide wavelength band, configures a feedback resonator to oscillate only the wavelength selected by the wavelength selection switch 30, and oscillates the laser. Here, the optical fiber amplifier 10 may have a wavelength band of C-band (1530 to 1565 nm), L-band (1565 to 1625 nm), and O-band (1260 to 1360 nm) depending on the material added to the optical fiber gain medium. It may have different wavelength bands depending on an optical fiber additive material such as ytterbium (Yb) or neodium (Nd) and an optical amplification medium such as SOA (Semiconductor Optical Amplifier).

The optical coupler 20 outputs some of the laser amplified by the optical fiber amplifier 10 and returns the remainder to the wavelength selection switch 30 to form a laser resonator so that laser oscillation of the selected wavelength is maintained.

The wavelength selection switch 30 receives the broadband laser from the optical coupler 20, selects a laser of a specific wavelength channel using the MEMS mirror array 70, and outputs the laser to the optical fiber amplifier 10. In detail, the wavelength selection switch 30 disperses light of a broadband wavelength input through the optical fiber amplifier 10 through a wavelength splitter such as a diffraction grating 50, and selects only specific wavelengths by the MEMS mirror array 70. By configuring the laser resonator so that it is reflective, it provides a laser capable of selecting a wavelength over a wide band. At this time, since the dispersion according to the wavelength is generally nonlinear in the wavelength splitter, the MEMS mirror array 70 is arranged nonlinearly to correspond to each of the plurality of nonlinearly dispersed wavelength channels, and the wavelength channel spacing is corrected to accurately meet the DWDM optical communication standard. can do.

Further, the controller 90 controls driving of the optical fiber amplifier 10 and the wavelength selection switch 30 to select and output the laser of a specific wavelength channel from the input wideband laser. That is, the controller 90 controls the optical gain by driving the optical fiber amplifier 10 and selectively drives the MEMS mirror 71 of the wavelength selection switch 30 to output the laser of a specific wavelength channel among the input broadband lasers. Control.

The wavelength selection switch 30 according to this embodiment will be described with reference to FIGS. 2 to 7 as follows.

FIG. 2 is a block diagram showing the wavelength selection switch 30 of FIG. 1 . And FIG. 3 is an exemplary view showing a process of selecting and outputting a specific wavelength in the wavelength selection switch 30 of FIG. 2 .

The wavelength selection switch 30 according to this embodiment includes a diffraction grating 50 and an MEMS mirror array 70. The diffraction grating 50 receives broadband parallel light and spatially disperses it according to the wavelength. In addition, the MEMS mirror array 70 includes a plurality of MEMS mirrors 71 non-linearly arranged to correspond to a plurality of wavelength channels non-linearly dispersed by the diffraction grating 50, respectively, and a plurality of MEMS mirrors 71 ) Selectively reflects the light of a specific wavelength channel among a plurality of wavelength channels input to the optical fiber amplifier 10 to cause laser oscillation.

In addition, the wavelength selection switch 30 according to the present embodiment may further include an input/output optical collimator 40 and an optical system 60 .

The input/output optical collimator 40 includes an input optical collimator and an output optical collimator. The input light collimator 40 collects the input broadband laser into parallel light and transmits it to the diffraction grating 50 . The collimated light reaching the MEMS mirror array 70 through the optical system 60 returns only a specific wavelength reflected from the specific MEMS mirror 71 to the optical fiber amplifier 10 and oscillates as a laser to output the laser beam. The input optical collimator and the output optical collimator can be simultaneously used as one component, that is, the input/output collimator 40 . That is, one optical collimator may be simultaneously used as an input optical collimator and an output optical collimator.

Lasers input and output to the input/output optical collimator 40 are input and output through an optical fiber.

A reflection type or transmission type diffraction grating may be used as the diffraction grating 50 . A blaze grating capable of reducing light loss may be used as the diffraction grating 50 . The angle between the diffraction grating 50 and the incident angle of the broadband laser is only slightly shifted by 5 degrees or less from the blaze angle, because the laser This is to avoid excessive complexity of the optical system 60 by returning to the incident path.

The optical system 60 vertically enters the MEMS mirror array 70 through the optical system 60 with lasers of a plurality of wavelength channels that are nonlinearly dispersed by the diffraction grating 50 . The optical system 60 may include a mirror or a lens. The mirror reflects lasers of a plurality of wavelength channels nonlinearly dispersed by the diffraction grating 70 to the MEMS mirror array 70 in parallel. The mirror may be replaced with a lens, and the lens should be positioned so that the output light scattered by the diffraction grating reaches the MEMS mirror array 70 in parallel.

Also, the MEMS mirror array 70 is disposed to be perpendicular to the laser light incident by the optical system 60. The MEMS mirror array 70 includes a plurality of MEMS mirrors 71 corresponding to wavelength channels for wavelength selection. Each of the plurality of MEMS mirrors 71 is disposed at a position corresponding to a wavelength channel so as to oscillate a laser having an exact wavelength corresponding to a wavelength channel that meets a standard.

As shown in FIGS. 4 and 5, the MEMS mirror array 70 according to this embodiment includes a plurality of MEMS mirrors 71 that reflect light, and a plurality of MEMS mirrors ( 71) each independently swinging in one axis direction. In the drawing, axis 1 may be the Y axis. Here, FIG. 4 is a plan view showing the MEMS mirror array 70 of FIG. 2 . And FIG. 5 is an enlarged view of the MEMS mirror 71 of FIG. 4 .

At this time, the plurality of MEMS mirrors 71 are arranged 70 in a line. Also, the plurality of electrostatic actuators 73 are alternately connected up and down to the plurality of MEMS mirrors 71 in one axis direction. Here, when the 1-axis direction is the Y-axis, up and down indicate the Y-axis direction.

Because of this, since the area on the other side of the MEMS mirror 71 to which the electrostatic driver 73 is not connected is an empty space, the empty space is the electrostatic driver 73 connected to the adjacent MEMS mirror 71 in the opposite direction. By using it as a space where is installed, the MEMS mirror array 70 can be designed compactly. Here, when the electrostatic actuator 73 is connected in the -Y axis direction of the MEMS mirror 71, a portion of the MEMS mirror 71 in the +Y axis direction corresponds to an empty space.

Of course, the plurality of MEMS mirrors 71 may each connect the electrostatic actuators 73 in only one direction, but in this case, the size of the MEMS mirror array 70 increases due to the space required for installing the electrostatic actuators 73. problems can arise

The MEMS mirror 71 is formed in a rectangular shape, and an electrostatic driver 73 is connected to one side of a short side.

As shown in FIG. 6 , the MEMS mirror 71 can adjust the line widths A and B of the laser selected by the widths a and b of the short sides. Here, FIG. 6 is an exemplary view showing changes in the line widths A and B of the output laser according to the line widths a and b of the MEMS mirror 71 of FIG. 5 .

The MEMS mirror array 70 can easily adjust the line widths A and B of the output laser by adjusting the widths a and b of the MEMS mirror 71 . That is, the MEMS mirror 71 outputs a laser having a wide line width A when the width (a) of the MEMS mirror 71 is wide (FIG. 6(a)), and conversely, when the width (b) of the MEMS mirror 71 is If it is narrow, a laser with a narrow line width B can be output (FIG. 6(b)).

The line widths A and B of the laser output here are determined by calculating an optical path that is dispersed in the diffraction grating 50 and incident on the MEMS mirror array 70. Widths a and b of the plurality of MEMS mirrors 71 may be designed according to the determined optical path.

In addition, the plurality of MEMS mirrors 71 are nonlinearly arranged to correspond to the plurality of wavelength channels nonlinearly dispersed by the diffraction grating 50 . That is, the central wavelength of the outputted laser is determined by calculating an optical path that is dispersed in the diffraction grating 50 and incident on the MEMS mirror array 70. A plurality of MEMS mirrors 70 may be designed to be arranged according to a determined optical path.

The reason for nonlinearly arranging the plurality of MEMS mirrors 71 in the MEMS mirror array 70 is as follows.

The ITU-T DWDM Grid standard defines the interval between channels as 25 GHz, 50 GHz or 100 GHz based on the frequency of the optical signal.

When a broadband laser is dispersed using the diffraction grating 50, the direction in which it travels is determined according to each wavelength, and the laser is dispersed at non-regular, non-linear intervals. However, when elements such as MEMS mirrors that select wavelengths are arranged at regular intervals, lasers with wavelengths that do not exactly meet the ITU-T DWDM Grid standard are output, which does not meet the system standard or causes noise between communication channels.

Therefore, in this embodiment, the plurality of MEMS mirrors 71 are disposed at positions corresponding to specific wavelength channels so as to output lasers of precise wavelengths corresponding to the respective wavelength channels. That is, the diffraction grating 50 disperses the laser so that the wavelength interval between the wavelength channels becomes nonlinearly longer as the wavelength of the laser increases. In addition, the MEMS mirror array 70 is designed so that the distance between the MEMS mirrors 71 is nonlinearly long to correspond to the wavelength distance of the wavelength channel that is nonlinearly long, so that the laser of a specific desired wavelength channel can be accurately selected and output. there is.

Table 1 below shows positions of MEMS mirror arrays according to wavelengths dispersed in a specific band. Table 1 is graphed as shown in FIG. 7 . 7 is a graph showing a MEMS mirror array according to wavelengths dispersed in a specific band according to an experimental example. Here, the specific band includes 1525.66 nm (196.5 GHz) to 1567.95 nm (191.2 GHz). The interval for each wavelength channel is 0.1 GHz.

channel number	frequency (THz)	wavelength (nm)	wavelength spacing (nm)	MEMS mirror position (μm)	MEMS mirror spacing (μm)
One	196.5	1525.66	-	0.0	-
2	196.4	1526.44	776.81	271.3	271.3
3	196.3	1527.22	777.60	543.9	272.6
4	196.2	1527.99	778.40	817.5	273.6
...
51	191.5	1565.50	817.06	15,300.5	348.6
52	191.4	1566.31	817.92	15,651.3	350.8
53	191.3	1567.13	818.77	16,004.2	352.9
54	191.2	1567.95	819.63	16,359.5	355.3

Referring to Table 1 and FIG. 7, it can be seen that the diffraction grating disperses the laser such that the wavelength interval between the wavelength channels becomes nonlinearly longer as the wavelength of the laser becomes longer.

Therefore, in the MEMS mirror array, the spacing between the MEMS mirrors is also nonlinear to correspond to the wavelength spacing of the wavelength channel in which the plurality of MEMS mirrors are nonlinearly long so that the laser that is nonlinearly dispersed by the diffraction grating can be accurately selected and output. It is arranged to be lengthened by

On the other hand, the embodiments disclosed in this specification and drawings are only presented as specific examples to aid understanding, and are not intended to limit the scope of the present invention. In addition to the embodiments disclosed herein, it is obvious to those skilled in the art that other modifications based on the technical idea of the present invention can be implemented.

[Description of code]

10: fiber optic amplifier

20: optical coupler

30: wavelength selection switch

40: input/output optical collimator

50: diffraction grating

60: optical system

61 : Mirror

63: focusing lens

70: MEMS mirror array

71: MEMS mirror

73: electrostatic driver

90: controller

100: wavelength selective laser system

Claims (12)

1. a diffraction grating that uses a broadband optical gain medium and nonlinearly disperses a plurality of wavelength channels; and

   It includes a plurality of MEMS mirrors non-linearly disposed to correspond to a plurality of wavelength channels non-linearly dispersed by the diffraction grating, and selects only a specific wavelength channel among the plurality of wavelength channels input to the plurality of MEMS mirrors. a MEMS mirror array that reflects into and causes resonance;

   A wavelength selection switch for a wavelength selective laser system comprising a.
2. According to claim 1,

   an input/output optical collimator that collects the broadband light emitted from the optical fiber amplifier in parallel and transfers the light to the diffraction grating, or collects the light of a specific wavelength selected from the MEMS mirror array and returns it to the optical fiber amplifier; and

   an optical system that transmits lasers of a plurality of wavelength channels nonlinearly dispersed by the diffraction grating to the MEMS mirror array in parallel;

   A wavelength selection switch for a wavelength selective laser system, characterized in that it further comprises.
3. According to claim 2,

   The broadband laser is at least one gain medium among semiconductor gain media including all optical fiber amplifiers and SOA including C-band (1530~1565nm), L-band (1565~1625nm) and O-band (1260~1360nm) A wavelength selection switch for a wavelength selective laser system, characterized in that it has a.
4. According to claim 3,

   The central wavelength of the output laser is determined by calculating an optical path that is dispersed in the diffraction grating and incident on the MEMS mirror array, and the arrangement of the plurality of MEMS mirrors is designed according to the determined optical path. Wavelength selection switch for laser systems.
5. According to claim 3,

   The diffraction grating is a wavelength selection switch for a wavelength selective laser system, characterized in that as the wavelength of the laser becomes longer, the wavelength distance between the wavelength channels becomes longer nonlinearly to disperse the laser.
6. According to claim 5,

   The wavelength selection switch for a wavelength selective laser system, characterized in that the distance between the plurality of MEMS mirrors is arranged to be nonlinearly long so as to correspond to the wavelength spacing of the wavelength channel that is nonlinearly long.
7. The method of claim 6, wherein the MEMS mirror array,

   a plurality of electrostatic actuators that independently oscillate the plurality of MEMS mirrors in a uniaxial direction;

   A wavelength selection switch for a wavelength selective laser system, characterized in that it further comprises.
8. The method of claim 7, wherein the MEMS mirror array,

   The plurality of MEMS mirrors are arranged in a line,

   The wavelength selection switch for a wavelength selective laser system, characterized in that the plurality of electrostatic actuators are alternately connected up and down to a plurality of MEMS mirrors in the uniaxial direction, respectively.
9. 9. The method of claim 8, wherein the MEMS mirror is

   It is formed in a rectangular shape, and the electrostatic actuator is connected to one side of a short side in the uniaxial direction,

   A wavelength selection switch for a wavelength selective laser system, characterized in that the line width of the laser selected by the width of the short side is determined.
10. According to claim 8,

    The line width of the output laser is determined by calculating an optical path that is dispersed in the diffraction grating and incident on the MEMS mirror array, and the widths of the plurality of MEMS mirrors are designed according to the determined optical path. Wavelength selection switch for system.
11. A wavelength selection switch that selectively outputs a laser of a specific wavelength channel suitable for laser resonance conditions using a broadband optical gain medium; includes,

    The wavelength selection switch,

    a diffraction grating using the broadband optical gain medium and dispersing nonlinearly into a plurality of wavelength channels; and

    It includes a plurality of MEMS mirrors nonlinearly arranged to correspond to a plurality of wavelength channels nonlinearly dispersed by the diffraction grating, and selectively selects only a specific wavelength among the plurality of wavelength channels input to the plurality of MEMS mirrors. An array of MEMS mirrors that reflect and cause resonance;

    A wavelength-selective laser system comprising a.
12. The method of claim 11, wherein the wavelength selection switch,

    an input/output optical collimator that collects the broadband light emitted from the optical fiber amplifier in parallel and transfers the light to the diffraction grating, or collects light of a specific wavelength selected from the MEMS mirror array and outputs the collected light to the optical fiber amplifier; and

    an optical system that transmits lasers of a plurality of wavelength channels nonlinearly dispersed by the diffraction grating to the MEMS mirror array in parallel;

    A wavelength selective laser system further comprising a.

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