Optical filter

Abstract

The invention relates to the technical field of optics, and provides an optical filter which is used for filtering light beams of a light source and comprises a filtering module and a tuning module, the filtering module comprises a first filtering unit and a second filtering unit, and the tuning module is connected with the first filtering unit and / or the second filtering unit. The filter unit is used for adjusting the band-pass central wavelength and / or the band-pass width of the first filter unit and / or the second filter unit. The filtering range of the first filtering unit and the filtering range of the second filtering unit are partially overlapped, the light beam is output after being filtered by the first filtering unit and the second filtering unit, and narrow linewidth light with adjustable band-pass central wavelength and / or band-pass width is obtained; as the filtering module is internally provided with the two filtering units of which the filtering ranges are partially overlapped, even if the filtering range of each filtering unit is relatively wide, as long as the overlapped part of the filtering ranges of the two filtering units is small enough, a light beam with extremely narrow line width can be obtained, and the line width of the output light beam and the central wavelength range can be tuned.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and more particularly to an optical filter. Background Art

[0002] With the rapid development of optical communications, high-resolution optics, laser sensing and other fields, it is necessary to eliminate unnecessary other noise optical signals in the system through tunable bandpass optical filters to obtain single-channel, single longitudinal mode optical signals.

[0003] The traditional implementation of optical filters mainly includes Fabry-Perot Interferometer, dielectric thin film filter, acousto-optic tunable filter (AOTF), Mach-Zehnder interferometer and tunable fiber grating filter. Fabry-Perot interferometer filter is composed of a resonant cavity composed of two parallel mirrors, one mirror is fixed and the other is movable, so that the length of the resonant cavity can be changed to select the required channel from the wavelength division multiplexing channel. When making a resonant cavity on an optical fiber, the end face of the optical fiber itself acts as two parallel mirrors. If the optical fiber is fixed on a piezoelectric ceramic, the piezoelectric ceramic can be electrostricted by applying an external voltage to change the length of the resonant cavity. The acousto-optic tunable filter is a device based on the interaction between acousto-optics, which is composed of an acousto-optic converter (from TE to TM), two orthogonal polarizers and two very close optical waveguides. If the incident light is in TE mode, applying the RF signal to the transparent optical waveguide will cause periodic disturbances in its molecular structure. This period determines the period of refractive index change, and the polarization of all light waves that meet the Bragg condition is also converted from TE to TM, thereby achieving filtering. The principle of the Mach-Zehnder interference filter is based on the interference theory of two monochromatic lights after being transmitted through different optical paths. It consists of two 3dB couplers in series to form a Mach-Zehnder interferometer. The two arms of the interferometer are of different lengths. Adjusting the optical path difference can achieve a tunable Mach-Zehnder interference filter. Tunable fiber Bragg gratings usually use the filtering characteristics of phase-shifted gratings. The central wavelength of the fiber Bragg grating can change with temperature and fiber length. The central wavelength can be tuned by keeping the temperature constant and changing the length using a mechanical device, or keeping the length constant and changing the temperature.

[0004] However, the above optical filters are generally very complex in structure, difficult to tune, and have a narrow filtering bandwidth. Tunable fiber grating filters can only achieve tuning of the filter center range, but cannot change the passband size, nor can they simultaneously change the filter passband size and the filter unit center wavelength.

[0005] The above shortcomings need to be improved. Summary of the invention

[0006] The object of the present invention is to provide an optical filter to solve the technical problems in the prior art that the optical filter is difficult to tune and has a too wide filtering range.

[0007] To achieve the above object, the technical solution adopted by the present invention is: to provide an optical filter for filtering the light beam of a light source, comprising:

[0008] A filtering module, comprising a first filtering unit and a second filtering unit for filtering the light beam;

[0009] A tuning module, connected to the first filtering unit and / or the second filtering unit, and used to adjust the bandpass center wavelength and / or the bandpass width and / or the slope of the bandpass filtering edge of the first filtering unit and / or the second filtering unit;

[0010] The filtering range of the first filtering unit partially overlaps with the filtering range of the second filtering unit. The light beam is output after being filtered by the first filtering unit and the second filtering unit to obtain narrow linewidth light with adjustable passband center wavelength and / or passband width.

[0011] In one embodiment, the tuning module includes a first tuning unit, which is connected to the first filtering unit and is used to adjust the bandpass center wavelength and / or the bandpass width and / or the slope of the bandpass filtering edge of the first filtering unit;

[0012] or,

[0013] The tuning module comprises a second tuning unit, which is connected to the second filtering unit and is used to adjust the bandpass center wavelength and / or the bandpass width and / or the slope of the bandpass filtering edge of the second filtering unit;

[0014] or,

[0015] The tuning module includes a first tuning unit and a second tuning unit, the first tuning unit is connected to the first filtering unit, and the second tuning unit is connected to the second filtering unit.

[0016] In one embodiment, the first filtering unit is a transmission filtering unit, which is used to connect with the light source and perform transmission filtering on the light beam;

[0017] The second filtering unit is a transmission filtering unit, which is used to perform transmission filtering on the light beam and output the narrow line width light.

[0018] In one embodiment, the first filtering unit is a transmission filtering unit, which is used to perform transmission filtering on the light beam;

[0019] The second filtering unit is a reflective filtering unit, which is used to perform reflective filtering on the light beam.

[0020] In one embodiment, the first filter unit is further used to connect to the light source, and the light beam is sequentially transmitted through the first filter unit, reflected by the second filter unit, and then emitted through the first filter unit.

[0021] In one embodiment, the optical filter further comprises an output unit for outputting the narrow linewidth light at a side end of the filter module;

[0022] The first filter unit is also used to connect with the light source, and the light beam is sequentially transmitted through the first filter unit, reflected by the second filter unit, and then emitted through the output unit.

[0023] In one embodiment, the optical filter further comprises a coupling unit for coupling the light beam of the light source into the filtering module;

[0024] The light beam is sequentially transmitted through the coupling unit, the first filtering unit, reflected by the second filtering unit, and transmitted through the first filtering unit before being emitted.

[0025] In one embodiment, the first filtering unit is a reflective filtering unit that performs reflective filtering on the light beam;

[0026] The second filtering unit is a reflective filtering unit, which is used to perform reflective filtering on the light beam;

[0027] The optical filter further comprises:

[0028] A coupling unit, used for coupling the light beam of the light source into the filtering module;

[0029] An output unit is used to output the narrow line width light at the side end of the filter module.

[0030] In one embodiment, the optical filter further includes an isolation unit, which is disposed on the output path of the filter module and is used to isolate reverse narrow linewidth light.

[0031] In one embodiment, the optical filter further comprises a circulator arranged on an output path of the filtering module.

[0032] In one embodiment, the first filtering unit is a high-reflection fiber Bragg grating or a high-transmission fiber Bragg grating, and the second filtering unit is a high-reflection fiber Bragg grating or a high-transmission fiber Bragg grating.

[0033] The beneficial effects of an optical filter provided by the present invention are at least:

[0034] (1) The filter module is provided with two filter units (a first filter unit and a second filter unit) whose filter ranges partially overlap. Thus, even if the filter range of each filter unit is relatively wide, as long as the overlapping portion of the filter ranges of the two filter units is small enough, a light beam with an extremely narrow line width can be obtained. By adjusting the first filter unit and / or the second filter unit through the tuning module, the output light beam line width and the central wavelength range can be tuned.

[0035] (2) Since the filtering range requirement for each filtering unit is not high, filtering units with lower parameters and wider filtering range can be used, which greatly reduces the process difficulty.

[0036] (3) By setting a tuning module, the bandpass center wavelength and / or the bandpass width of the first filter unit and / or the second filter unit can be adjusted, so that the line width and frequency of the narrow linewidth light can be adjusted as needed to meet diverse usage requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 Schematic diagram of the structure of the optical filter provided in the embodiment of the present invention Figure 1 ;

[0039] Figure 2 Schematic diagram of the structure of the optical filter provided in the embodiment of the present invention Figure 2 ;

[0040] Figure 3 Schematic diagram of the structure of the optical filter provided in the embodiment of the present invention Figure 3 ;

[0041] Figure 4 The working principle of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 1 ;

[0042] Figure 5 The working principle of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 2 ;

[0043] Figure 6 The working principle of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 3 ;

[0044] Figure 7 The working principle of the tuning module of the optical filter provided in the embodiment of the present invention is shown in FIG. Figure 1 ;

[0045] Figure 8 The working principle of the tuning module of the optical filter provided in the embodiment of the present invention is shown in FIG. Figure 2 ;

[0046] Fig. 9 The working principle of the first embodiment of the optical filter provided by the present invention is shown in FIG. Figure 1 ;

[0047] Fig.10 The working principle of the first embodiment of the optical filter provided by the present invention is shown in FIG. Figure 2 ;

[0048] Fig.11 The working principle of the second embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 1 ;

[0049] Fig.12 The working principle of the second embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 2 ;

[0050] Fig.13 The working principle of the third embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 1 ;

[0051] Fig.14 The working principle of the third embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 2 ;

[0052] Fig.15 The working principle of the fourth embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 1 ;

[0053] Fig.16 The working principle of the fourth embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 2 ;

[0054] Fig.17 The working principle of the fifth embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 1 ;

[0055] Fig.18 The working principle of the fifth embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 2 ;

[0056] Fig.19The working principle of the sixth embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 1 ;

[0057] Fig. 20 The working principle of the sixth embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 2 ;

[0058] Fig.21 The working principle of the seventh embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 1 ;

[0059] Fig. 22 The working principle of the seventh embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 2 ;

[0060] Fig.23 The working principle of the seventh embodiment of the optical filter provided by the embodiment of the present invention is shown in FIG. Figure 3 .

[0061] Among them, the reference numerals in the figure are:

[0062] 10-light source; 20-filter module;

[0063] 201-a first filtering unit; 202-a second filtering unit;

[0064] 30- tuning module; 301- first tuning unit;

[0065] 302-second tuning unit;

[0066] 40-coupling unit; 50-output unit;

[0067] 60-isolation unit; 70-circulator. DETAILED DESCRIPTION

[0068] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0069] It should be noted that when a component is referred to as being "fixed on" or "disposed on" another component, it may be directly or indirectly located on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The directions or positions indicated by the terms "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positions shown in the accompanying drawings and are only for the convenience of description and cannot be understood as limitations on the present technical solution. The terms "first" and "second" are only used for the convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0070] Figures 1 to 23 A schematic diagram of the structure of an optical filter provided in this embodiment.

[0071] See also Figure 1 and Fig. 9 , an optical filter for filtering a light beam of a light source 10, comprising a filter module 20 and a tuning module 30, wherein the filter module 20 comprises a first filter unit 201 and a second filter unit 202 for filtering laser light, and the tuning module 30 is connected to the first filter unit 201 and / or the second filter unit 202, and is used to adjust the bandpass center wavelength and / or the bandpass width and / or the slope of the bandpass filter edge of the first filter unit 201 and / or the second filter unit 202. The filtering range of the first filter unit 201 partially overlaps with the filtering range of the second filter unit 202, and the light beam of the light source 10 is output after being filtered by the first filter unit 201 and the second filter unit 202, so as to obtain narrow line width light with adjustable bandpass center wavelength and / or bandpass width. The filtering described in this embodiment is frequency filtering, and the frequency range of the output laser light is the overlapping part of the filtering range of the first filter unit 201 and the filtering range of the second filter unit 202. The light source 10 can be a laser or other forms of light source, which is not limited here.

[0072] The adjustment method of the tuning module 30 at least includes:

[0073] Adjusting the bandpass center wavelength of the first filtering unit 201 or the second filtering unit 202;

[0074] Adjusting the passband width of the first filtering unit 201 or the second filtering unit 202;

[0075] Adjusting the passband center wavelength and passband width of the first filtering unit 201 or the second filtering unit 202;

[0076] Adjusting the bandpass center wavelengths of the first filtering unit 201 and the second filtering unit 202;

[0077] Adjusting the passband widths of the first filtering unit 201 and the second filtering unit 202;

[0078] Adjusting the passband center wavelength and passband width of the first filtering unit 201 and the second filtering unit 202;

[0079] Adjust the bandpass center wavelength of the first filtering unit 201 and adjust the bandpass width of the second filtering unit 202;

[0080] The passband width of the first filtering unit 201 is adjusted, and the passband center wavelength of the second filtering unit 202 is adjusted.

[0081] The working principle of an optical filter provided in this embodiment is as follows: first, the filter module 20 is connected to the light source 10 so that the light beam generated by the light source 10 can enter the filter module 20. The light source 10 can be a part of the optical filter or an external light source. When filtering is required, the light beam generated by the light source 10 enters the filter module 20. After filtering by the first filter unit 201 and the second filter unit 202, the light beam with a frequency range that is the overlapping part of the filtering range of the first filter unit 201 and the second filter unit 202 is output from the filter module 20, so that a filtered light with a narrow frequency range and narrow line width can be obtained. The bandpass center wavelength and / or bandpass width of the first filter unit 201 and / or the second filter unit 202 are adjusted by the tuning module 30, so that the bandpass center wavelength and / or bandpass width of the output narrow line width light can be adjusted.

[0082] The beneficial effects of an optical filter provided by this embodiment are:

[0083] (1) The filter module 20 is provided with two filter units (a first filter unit 201 and a second filter unit 202) whose filter ranges partially overlap. Thus, even if the filter range of each filter unit is relatively wide, as long as the overlapping portion of the filter ranges of the two filter units is small enough, a light beam with an extremely narrow line width can be obtained. By adjusting the first filter unit 201 and / or the second filter unit 202 through the tuning module 30, the output light beam line width and the central wavelength range can be tuned.

[0084] (2) Since the filtering range requirement for each filtering unit is not high, filtering units with lower parameters and wider filtering range can be used, which greatly reduces the process difficulty.

[0085] (3) By setting the tuning module 30, the bandpass center wavelength and / or the bandpass width of the first filtering unit 201 and / or the second filtering unit 202 can be adjusted, so that the line width and frequency of the narrow linewidth light can be adjusted as needed to meet diverse usage requirements.

[0086] See also Figure 2 In one embodiment, the tuning module 30 includes a first tuning unit 301, which is connected to the first filtering unit 201 and is used to adjust the passband center wavelength and / or passband width of the first filtering unit 201. By adjusting the passband center wavelength of the first filtering unit 201, the passband center wavelength of the overlapping portion of the first filtering unit 201 and the second filtering unit 202 can be adjusted; by adjusting the passband width of the first filtering unit 201, the passband width of the overlapping portion of the first filtering unit 201 and the second filtering unit 202 can be adjusted.

[0087] See also Figure 3 In one embodiment, the tuning module 30 includes a second tuning unit 302, which is connected to the second filtering unit 202 and is used to adjust the passband center wavelength and / or passband width of the second filtering unit 202. By adjusting the passband center wavelength of the second filtering unit 202, the passband center wavelength of the overlapping portion of the first filtering unit 201 and the second filtering unit 202 can be adjusted; by adjusting the passband width of the second filtering unit 202, the passband width of the overlapping portion of the first filtering unit 201 and the second filtering unit 202 can be adjusted.

[0088] See also Figure 1 In one embodiment, the tuning module 30 includes a first tuning unit 301 and a second tuning unit 302. The first tuning unit 301 is connected to the first filtering unit 201, and the second tuning unit 302 is connected to the second filtering unit 202. By adjusting the bandpass center wavelengths of the first filtering unit 201 and the second filtering unit 202, the bandpass center wavelengths of the overlapping parts of the first filtering unit 201 and the second filtering unit 202 can be adjusted (see Figure 7 , L30′ is the bandpass center wavelength before adjustment, and L30 is the bandpass center wavelength after adjustment); by adjusting the bandpass width of the first filtering unit 201 and the second filtering unit 202, the bandpass width of the overlapping portion of the first filtering unit 201 and the second filtering unit 202 can be adjusted (see Figure 8 , L30′ is the passband width before adjustment, and L30 is the passband width after adjustment).

[0089] See also Figure 4 and Fig. 9In one embodiment, the first filter unit 201 is a transmission filter unit that performs transmission filtering on the light beam. The first filter unit 201 is connected to the light source 10, so that a part of the light beam generated by the light source 10 can enter the filter module 20 through the first filter unit 201; the second filter unit 202 is a transmission filter unit that performs transmission filtering on the light beam. After the light beam in the filter module 20 passes through the second filter unit, part of it is transmitted and output.

[0090] The light beam generated by the light source 10 is a wide spectrum light beam. When the light beam passes through the first filter unit 201, the light beam within the reflection spectrum range (i.e., the first reflection spectrum range L11) of the first filter unit 201 is filtered and cannot pass through the first filter unit 201, while the light beam outside the first reflection spectrum range L11 passes through the first filter unit 201 and enters the filter module 20. The light beam entering the filter module 20 continues to propagate to the second filter unit 202, and the light beam within the reflection spectrum range (i.e., the second reflection spectrum range L21) of the second filter unit 202 is filtered and cannot pass through the second filter unit 202, while the light beam outside the second reflection spectrum range L21 passes through the second filter unit 202 and then exits. The overlapping portion of the frequency domain outside the first reflection spectrum range L11 and the frequency domain outside the second reflection spectrum range L21 is the filter range L30, and the light beam output after passing through the second filter unit 202 is the narrow line width light of the filter range L30.

[0091] It should be understood that the first filtering unit 201 can also allow part of the light beam to be transmitted, while the part of the light beam that cannot be transmitted will be absorbed by the first filtering unit 201; the second filtering unit 202 can also allow part of the light beam to be transmitted, while the part of the light beam that cannot be transmitted will be absorbed by the second filtering unit 202.

[0092] In one embodiment, the first filter unit 201 is a transmission filter unit that performs transmission filtering on the light beam, and the reflection spectrum range of the first filter unit 201 is the first reflection spectrum range L11, and the light beam outside the first reflection spectrum range L11 enters the filter module 20 or is emitted from the filter module 20 through the first filter unit 201; the second filter unit 202 is a reflection filter unit that performs reflection filtering on the light beam, and the transmission spectrum range of the second filter unit 202 is the second transmission spectrum range L22, and the light beam outside the second transmission spectrum range L22 will be reflected at the second filter unit 202; the overlapping part of the frequency domain outside the first reflection spectrum range L11 and the frequency domain outside the second transmission spectrum range L22 is the filter range L30, and the light beam output after passing through the filter module 20 is the narrow line width light of the filter range L30.

[0093] See also Figure 5 and Fig.11In one embodiment, the first filter unit 201 is a transmission filter unit, the second filter unit 202 is a reflection filter unit, and the first filter unit 201 is connected to the light source 10, so that the light beam of the light source 10 can enter the filter module 20 through the first filter unit 201. The light beam entering the filter module 20 continues to be transmitted to the second filter unit 202 for reflection, and the reflected part of the light beam returns to the first filter unit 201 and is filtered by the first filter unit 201 before being emitted, and the output light beam is a narrow line width light in the filtering range L30.

[0094] It should be understood that the first filtering unit 201 can also allow part of the light beam to be transmitted, while the part of the light beam that cannot be transmitted will be absorbed by the first filtering unit 201; the second transmission spectral range L22 of the second filtering unit 202 can also be an absorption range, that is, the light beam within this range will be absorbed by the second filtering unit 202.

[0095] See also Figures 13 to 16 In one embodiment, the first filter unit 201 is a transmission filter unit, the second filter unit 202 is a reflection filter unit, and the optical filter further comprises a coupling unit 40, which is connected to the first filter unit 201 and the light source 10, so as to couple the light beam of the light source 10 into the filter module 20. At this time, the light beam transmitted by the first filter unit 201 can be directly emitted through the first filter unit 201, or can be emitted after being transmitted to the coupling unit 40. Figure 21 to Figure 23 The coupling unit 40 may also be located in the filter module 20, and the coupling unit 40 is connected to the light source 10, so that the laser of the light source 10 is coupled into the filter module 20. After the light beam enters the filter module 20, it is first transmitted to the second filter unit 202 for reflection. The reflected part of the light beam returns to the first filter unit 201 and is filtered by the first filter unit 201 before being emitted. The output narrow line width light is the light beam in the filtering range L30.

[0096] See also Fig.19 In one embodiment, the first filter unit 201 is a transmission filter unit, the first filter unit 201 is connected to the light source 10, the second filter unit 202 is a reflection filter unit, and the optical filter further includes an output unit 50 for outputting a light beam at the side end of the filter module 20. The light beam of the light source 10 is sequentially transmitted through the first filter unit 201, reflected by the second filter unit 202, and then emitted through the output unit 50, and the output narrow line width light is a light beam within the filtering range L30. The output unit 50 may also be located outside the filter module 20 and connected to the first filter unit 201, so that the light beam is sequentially transmitted through the first filter unit 201, reflected by the second filter unit 202, and transmitted by the first filter unit 201, and then emitted through the output unit 50.

[0097] See also Figure 6 and Fig.21 In one embodiment, the first filter unit 201 is a reflective filter unit that performs reflective filtering on the light beam, and the transmission spectrum range of the first filter unit 201 is the first transmission spectrum range L12, and the light beam outside the first transmission spectrum range L12 will be reflected at the first filter unit 201; the second filter unit 202 is a reflective filter unit that performs reflective filtering on the light beam, and the transmission spectrum range of the second filter unit 202 is the second transmission spectrum range L22, and the light beam outside the second transmission spectrum range L22 will be reflected at the second filter unit 202; the overlapping part of the frequency domain outside the first transmission spectrum range L12 and the frequency domain outside the second transmission spectrum range L22 is the filter range L30, and the narrow line width light output after passing through the filter module 20 is the light beam in the filter range L30.

[0098] The optical filter also includes a coupling unit 40 and an output unit 50. The coupling unit 40 is located in the filter module 20, and the coupling unit 40 is connected to the light source 10, so as to couple the light beam of the light source 10 into the filter module 20; the output unit 50 is used to output narrow line width light at the side end of the filter module 20. The light beam of the light source 10 enters the filter module 20 through the coupling unit 40, and is output through the output unit 50 after being transmitted by the first filter unit 201 and reflected by the second filter unit 202. The output narrow line width light is a light beam in the filter range L30. It should be understood that the first transmission spectrum range L12 of the first filter unit 201 can also be an absorption range, that is, the light beam within this range will be absorbed by the first filter unit 201; the second transmission spectrum range L22 of the second filter unit 202 can also be an absorption range, that is, the light beam within this range will be absorbed by the second filter unit 202.

[0099] See also Fig. 22 Furthermore, the optical filter provided in this embodiment may include an isolation unit 60 disposed on the output path of the filter module 20 for isolating the reverse narrow linewidth light, thereby protecting the optical filter.

[0100] See also Fig.23 Furthermore, the optical filter provided in this embodiment may also include a circulator 70 arranged on the output path of the filter module 20, which can be used to output narrow linewidth light on the one hand, and can transmit the light beam back to the filter module on the other hand.

[0101] Furthermore, the first filter unit 201 and the second filter unit 202 may be high-reflection fiber Bragg gratings, and the light (including laser) in the frequency domain within the reflection spectrum range of the high-reflection fiber Bragg grating is filtered. The first tuning unit 301 is connected to the first filter unit 201, and the second tuning unit 302 is connected to the second filter unit 202. By affecting the physical and chemical properties of the grating (including temperature, stress, pressure, etc.), the bandpass center wavelength and the bandpass width are adjusted to meet specific usage requirements. Of course, the first filter unit 201 and the second filter unit 202 may also be high-transmission fiber Bragg gratings, which are not limited here.

[0102] Several specific embodiments are provided below, but are not limited to the following embodiments. In the following embodiments, the tuning module 30 may include a first tuning unit 301, the first tuning unit 301 is connected to the first filtering unit 201, and is used to adjust the bandpass center wavelength and / or the bandpass width of the first filtering unit 201; the tuning module 30 may include a second tuning unit 302, the second tuning unit 302 is connected to the second filtering unit 202, and is used to adjust the bandpass center wavelength and / or the bandpass width of the second filtering unit 202; the tuning module 30 may also include a first tuning unit 301 and a second tuning unit 302, the first tuning unit 301 is connected to the first filtering unit 201, and the second tuning unit 302 is connected to the second filtering unit 202. Thus, the bandpass center wavelength and the bandpass width of the first filtering unit 201 and the second filtering unit 202 can be adjusted by the tuning module 30.

[0103] See also Figure 4 and Fig. 9 , Embodiment 1:

[0104] The first filter unit 201 is a transmission filter unit, and the second filter unit 202 is a transmission filter unit; the first filter unit 201 is connected to the light source 10, and the light beam in the filter module 20 is output from the second filter unit 202. Since the first filter unit 201 is a transmission filter unit, the light beam within the first reflection spectrum range L11 of the first filter unit 201 in the frequency domain is filtered and cannot pass through the first filter unit 201, and the light beam outside the first reflection spectrum range L11 in the frequency domain passes through the first filter unit 201; since the second filter unit 202 is also a transmission filter unit, the light beam within the second reflection spectrum range L21 of the second filter unit 202 in the frequency domain is filtered and cannot pass through the second filter unit 202, and the light beam outside the second reflection spectrum range L21 in the frequency domain passes through the second filter unit 202; the overlapping part of the frequency domain outside the first reflection spectrum range L11 and the frequency domain outside the second reflection spectrum range L21 is the filter range L30.

[0105] The light beam generated by the light source 10 is a wide-spectrum light beam. When the light beam passes through the first filtering unit 201, the light beam outside the first reflection spectrum range L11 in the frequency domain is transmitted through the first filtering unit 201 and enters the filtering module 20; the light beam entering the filtering module 20 continues to propagate to the second filtering unit 202, and the light beam outside the second reflection spectrum range L21 in the frequency domain is transmitted through the second filtering unit 202 and then emitted. The emitted light beam is a narrow-linewidth light in the wave range L30 in the filter frequency domain.

[0106] It should be understood that the light beam within the first reflection spectral range L11 in the frequency domain can be reflected at the first filtering unit 201, and can also be absorbed by the first filtering unit 201; the light beam within the second reflection spectral range L21 in the frequency domain can be reflected at the second filtering unit 202, and can also be absorbed by the second filtering unit 202.

[0107] See also Figure 5 and Fig.11 , Embodiment 2:

[0108] The first filter unit 201 is a transmission filter unit, and the reflection spectrum range of the first filter unit 201 in the frequency domain is the first reflection spectrum range L11, and the light beam outside the first reflection spectrum range L11 can pass through the first filter unit 201; the second filter unit 202 is a reflection filter unit, and the transmission range of the second filter unit 202 in the frequency domain is the second transmission spectrum range L22, and the light beam outside the second transmission spectrum range L22 will be reflected at the second filter unit 202; the overlapping part of the frequency domain outside the first reflection spectrum range L11 and the frequency domain outside the second transmission spectrum range L22 is the filtering range L30; the first filter unit 201 is connected to the light source 10, and the light beam in the filter module 20 is emitted through the first filter unit 201.

[0109] The light beam of the light source 10 enters the filter module 20 through the first filter unit 201. The light beam entering the filter module 20 continues to be transmitted to the second filter unit 202 and is reflected. The reflected part of the light beam returns to the first filter unit 201 and is emitted after being transmitted through the first filter unit 201. The output narrow line width light is the narrow line width light of the filter range L30.

[0110] It should be understood that the light beam within the first reflection spectral range L11 can be reflected at the first filtering unit 201 or absorbed by the first filtering unit 201; the light beam within the second transmission spectral range L22 can be transmitted at the second filtering unit 202 or absorbed by the second filtering unit 202.

[0111] See also Figure 5 and Fig.13 , Embodiment 3:

[0112] On the basis of the above-mentioned embodiment 2, the optical filter also includes a coupling unit 40, which is connected to the first filtering unit 201, and the coupling unit 40 is connected to the light source 10. The light beam of the light source 10 passes through the coupling unit 40 and the first filtering unit 201 in sequence and enters the filtering module. The light beam entering the filtering module 20 continues to be transmitted to the second filtering unit 202 and is reflected. The reflected part of the light beam returns to the first filtering unit 201 and is emitted after being transmitted through the first filtering unit 201. The output narrow linewidth light is the narrow linewidth light of the filtering range L30.

[0113] See also Figure 5 and Fig.15 , Embodiment 4:

[0114] Based on the above third embodiment, the light beam in the filter module 20 is transmitted through the first filter unit 201 and then emitted, and is transmitted to the coupling unit 40 and then emitted through the coupling unit 40, and the output narrow line width light is the narrow line width light of the filter range L30.

[0115] See also Figure 5 and Fig.17 , Embodiment 5:

[0116] The first filter unit 201 is a transmission filter unit, and the reflection spectrum range of the first filter unit 201 in the frequency domain is the first reflection spectrum range L11; the second filter unit 202 is a reflection filter unit, and the transmission spectrum range of the second filter unit 202 in the frequency domain is the second transmission spectrum range L22; the overlapping part of the frequency domain outside the first reflection spectrum range L11 and the frequency domain outside the second transmission spectrum range L22 is the filtering range L30; the optical filter also includes a coupling unit 40, which is located in the filtering module 20 and is connected to the light source 10; the light beam in the filtering module 20 is emitted through the first filter unit 201.

[0117] The light beam of the light source 10 enters the filter module 20 through the coupling unit 40. The light beam entering the filter module 20 continues to be transmitted to the second filter unit 202 and is reflected. The reflected part of the light beam continues to be transmitted to the first filter unit 201 and is emitted after being transmitted through the first filter unit 201. The output narrow line width light is the narrow line width light of the filter range L30.

[0118] See also Figure 5 and Fig.19 , Embodiment 6:

[0119] The first filter unit 201 is a transmission filter unit, and the reflection spectrum range of the first filter unit 201 in the frequency domain is the first reflection spectrum range L11; the second filter unit 202 is a reflection filter unit, and the transmission spectrum range of the second filter unit 202 in the frequency domain is the second transmission spectrum range L22; the overlapping part of the frequency domain outside the first reflection spectrum range L11 and the frequency domain outside the second transmission spectrum range L22 is the filter range L30; the first filter unit 201 is connected to the light source 10; the optical filter also includes an output unit 50 for outputting laser at the side end of the filter module 20.

[0120] The light beam of the light source 10 enters the filter module 20 through the first filter unit 201. The light beam entering the filter module 20 continues to be transmitted to the second filter unit 202 and is reflected. The reflected part of the light beam is emitted through the output unit 50, and the output narrow line width light is the narrow line width light of the filter range L30.

[0121] It should be understood that the output unit 50 may also be located outside the filter module 20 and connected to the first filter unit 201 , and the light beam is sequentially transmitted through the first filter unit 201 , reflected by the second filter unit 202 , and then emitted through the output unit 50 after being transmitted through the first filter unit 201 .

[0122] See also Figure 7 and Fig.21 , Embodiment 7:

[0123] The first filter unit 201 is a reflective filter unit, and the transmission spectrum range of the first filter unit 201 in the frequency domain is the first transmission spectrum range L12, and the light beam outside the first transmission spectrum range L12 will be reflected at the first filter unit 201; the second filter unit 202 is a reflective filter unit, and the transmission spectrum range of the second filter unit 202 in the frequency domain is the second transmission spectrum range L22; the overlapping part of the frequency domain outside the first transmission spectrum range L12 and the frequency domain outside the second transmission spectrum range L22 is the filter range L30. The optical filter also includes a coupling unit 40 and an output unit 50, the coupling unit 40 is located in the filter module 20, and the coupling unit 40 is connected to the light source 10, so as to couple the light beam of the light source 10 into the filter module 20; the output unit 50 is used to output narrow line width light at the side end of the filter module 20.

[0124] The light beam of the light source 10 enters the filter module 20 through the coupling unit 40, and is reflected by the first filter unit 201 and the second filter unit 202 before being output through the output unit 50. The output narrow line width light is the narrow line width light of the filter range L30. The light beam entering the filter module 20 may be first transmitted to the first filter unit 201 for reflection, and then transmitted to the second filter unit 202 for reflection, or may be first transmitted to the second filter unit 202 for reflection, and then transmitted to the first filter unit 201 for reflection.

[0125] It should be understood that the light beam within the first transmission spectral range L12 can be transmitted through the first filtering unit 201 or absorbed by the first filtering unit 201 ; the light beam within the second transmission spectral range L22 can be transmitted through the second filtering unit 202 or absorbed by the second filtering unit 202 .

[0126] See also Fig.10 , Fig.12 , Fig.14 , Fig.16 , Fig.18 , Fig. 20 and Fig. 22 Furthermore, the optical filter in the above-mentioned embodiments 1 to 7 may also include an isolation unit 60, which is arranged on the output path of the filter module 20 to isolate the reverse light beam, thereby protecting the optical filter.

[0127] Furthermore, the optical filter in the above-mentioned embodiments 1 to 7 may further include a circulator 70, which is arranged on the output path of the filter module 20 (for example Fig.23 It should be understood that when the light beam is emitted after passing through the coupling unit 40, the coupling unit 40 can be replaced by a circulator.

[0128] In the above embodiments, the light source 10, the filter module 20, the coupling unit 40, the output unit 50, the isolation unit 60 and the circulator 70 can be connected by optical fibers to realize a full-fiber optical filter; some components can also be connected by optical fibers to realize a partial fiber optical filter; and light can also be transmitted through free space, which is not limited here.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An optical filter for filtering a light beam from a light source, characterized in that: include A filtering module, comprising a first filtering unit and a second filtering unit for filtering the light beam; A tuning module, connected to the first filtering unit and / or the second filtering unit, and used to adjust the bandpass center wavelength and / or the bandpass width and / or the slope of the bandpass filtering edge of the first filtering unit and / or the second filtering unit; The filtering range of the first filtering unit partially overlaps with the filtering range of the second filtering unit. The light beam is output after being filtered by the first filtering unit and the second filtering unit to obtain narrow linewidth light with adjustable passband center wavelength and / or passband width.

2. The optical filter according to claim 1, wherein: The tuning module comprises a first tuning unit, which is connected to the first filtering unit and is used to adjust the bandpass center wavelength and / or the bandpass width and / or the slope of the bandpass filtering edge of the first filtering unit; or, The tuning module comprises a second tuning unit, which is connected to the second filtering unit and is used to adjust the bandpass center wavelength and / or the bandpass width and / or the slope of the bandpass filtering edge of the second filtering unit; or, The tuning module includes a first tuning unit and a second tuning unit, the first tuning unit is connected to the first filtering unit, and the second tuning unit is connected to the second filtering unit.

3. The optical filter according to claim 1, wherein: The first filtering unit is a transmission filtering unit, which is used to connect with the light source and perform transmission filtering on the light beam; The second filtering unit is a transmission filtering unit, which is used to perform transmission filtering on the light beam and output the narrow line width light.

4. The optical filter according to claim 1, wherein: The first filtering unit is a transmission filtering unit, which is used to perform transmission filtering on the light beam; The second filtering unit is a reflective filtering unit, which is used to perform reflective filtering on the light beam.

5. The optical filter according to claim 4, characterized in that: The first filter unit is also used to connect with the light source, and the light beam is sequentially transmitted through the first filter unit, reflected by the second filter unit, and then emitted through the first filter unit.

6. The optical filter according to claim 4, wherein: The optical filter further comprises an output unit, which is used to output the narrow line width light at the side end of the filter module; The first filter unit is also used to connect with the light source, and the light beam is sequentially transmitted through the first filter unit, reflected by the second filter unit, and then emitted through the output unit.

7. The optical filter according to claim 4, wherein: The optical filter further comprises a coupling unit, which is used to couple the light beam of the light source into the filtering module; The light beam is sequentially transmitted through the coupling unit, the first filtering unit, reflected by the second filtering unit, and transmitted through the first filtering unit before being emitted.

8. The optical filter according to claim 1, wherein: The first filtering unit is a reflective filtering unit, which performs reflective filtering on the light beam; The second filtering unit is a reflective filtering unit, which is used to perform reflective filtering on the light beam; The optical filter further comprises: A coupling unit, used for coupling the light beam of the light source into the filtering module; An output unit is used to output the narrow line width light at the side end of the filter module.

9. The optical filter according to any one of claims 1 to 8, characterized in that: The optical filter further comprises an isolation unit, which is arranged on the output path of the filter module and is used to isolate the reverse narrow linewidth light.

10. The optical filter according to any one of claims 1 to 8, characterized in that: The optical filter further comprises a circulator, which is arranged on the output path of the filter module.

11. The optical filter according to any one of claims 1 to 8, characterized in that: The first filtering unit is a high-reflection fiber Bragg grating or a high-transmission fiber Bragg grating, and the second filtering unit is a high-reflection fiber Bragg grating or a high-transmission fiber Bragg grating.

Images