Channel interval adjustable optical fiber filter based on cross interference and filtering method

Abstract

The invention discloses an optical fiber filter with an adjustable channel interval based on cross interference and a filtering method. The optical fiber filter is structurally characterized in that a polarizer, a first polarization controller and a polarization beam splitter are connected in sequence; the polarization beam splitter is divided into a branch I and a branch II, and the branch I is connected with the second polarization controller and the first polarization maintaining optical fiber in sequence; the branch 2 is connected with a third polarization controller and a second polarization maintaining optical fiber in sequence; the branch I and the branch II are connected through a first circulator, a third polarization maintaining optical fiber and a second circulator to form cross interference; and the tail ends of the branch I and the branch II are respectively connected with two input ports of the beam combiner. By adjusting the first polarization controller, the second polarization controller or the third polarization controller, switching of three channel intervals can be achieved under the condition that devices are not replaced.

Description

Technical Field

[0001] The invention belongs to the technical field of optical communication, and in particular relates to an optical fiber filter with adjustable channel spacing based on cross interference and a filtering method. Background Art

[0002] Multi-wavelength fiber laser is a new type of laser technology developed with the advancement of optical fiber communication technology. It has the advantages of multi-wavelength, broadband, tunable, high power and stable output. It is suitable as a light source for dense wavelength division multiplexing and can meet the needs of high-capacity information transmission in optical fiber communication. In addition, multi-wavelength fiber laser can also meet the requirements of light sources in fields such as optical sensing and optical detection technology.

[0003] Periodic optical filters are indispensable wavelength selection components in dense wavelength division multiplexing optical networks, and fiber comb filters have attracted extensive attention due to their low cost, simple structure, small insertion loss, strong stability and strong compatibility with optical fiber communication systems. Such as the classic Mach-Zehnder interferometer, Sagnac ring and Lyot filter and their improved filters, but these filters require very fine adjustments when switching channel intervals, and still have shortcomings in structure, cost, stability and flexibility. Summary of the invention

[0004] In view of the above-mentioned shortcomings and deficiencies in the prior art, the present invention provides an optical fiber filter with adjustable channel spacing based on cross-interference and a filtering method thereof.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] A cross-interference-based channel spacing adjustable optical fiber filter comprises a polarizer, a first polarization controller, a polarization beam splitter, a second polarization controller, a first polarization-maintaining optical fiber, a first circulator, a third polarization controller, a second polarization-maintaining optical fiber, a second circulator, a third polarization-maintaining optical fiber, and a beam combiner; the polarizer, the first polarization controller, and the polarization beam splitter are connected in sequence; the polarization beam splitter divides into a first branch and a second branch, wherein, in the first branch: the output port 1 of the polarization beam splitter is connected in sequence to the second polarization controller and the first polarization-maintaining optical fiber; in the second branch: the output port 2 of the polarization beam splitter is connected in sequence to the third polarization controller and the second polarization-maintaining optical fiber; the output port of the first polarization-maintaining optical fiber is connected to the first port of the first circulator, the output port of the second polarization-maintaining optical fiber is connected to the first port of the second circulator, the second port of the first circulator is connected to the second port of the second circulator through the third polarization-maintaining optical fiber, and the third port of the first circulator and the third port of the second circulator are respectively connected to two input ports of the beam combiner.

[0007] As a preferred solution, the first polarization-maintaining optical fiber, the second polarization-maintaining optical fiber and the third polarization-maintaining optical fiber have different lengths or birefringence indices.

[0008] As a preferred solution, the first polarization-maintaining optical fiber, the second polarization-maintaining optical fiber and the third polarization-maintaining optical fiber can be replaced with different lengths and birefringence indices as needed.

[0009] As a preferred solution, the polarization beam splitter and the polarization beam combiner are the same optical device, and the different descriptions are intended to distinguish their working characteristics.

[0010] As a preferred solution, the polarizer is also connected to the broadband light source via an isolator.

[0011] As a preferred solution, the tail end of the polarization beam combiner is also connected to a spectrometer.

[0012] As a preferred solution, the combination of the first polarization controller and the first polarization beam splitter can change the output light intensity of the two output ports of the polarization beam splitter by adjusting the polarization controller, thereby realizing working branch switching.

[0013] As a preferred solution, the above connections are all optical fiber connections.

[0014] The present invention also discloses an optical fiber filtering method with adjustable channel spacing based on cross-interference. Based on the above optical fiber filter, the optical fiber filtering method is specifically as follows: the light output by the wide-spectrum light source is converted into polarized light with controllable polarization state after passing through an isolator, a polarizer, and a first polarization controller in sequence; the polarization beam splitter decomposes the polarized light into two mutually orthogonal linear polarized lights, which are coupled into branch one and branch two respectively; the linear polarized light of branch one enters the first polarization-maintaining optical fiber through the second polarization controller; the linear polarized light entering the first polarization-maintaining optical fiber is decomposed into two orthogonal vector modes, which are propagated on the fast and slow axes of the first polarization-maintaining optical fiber respectively; the linear polarized light The linearly polarized light of branch two enters the second polarization-maintaining fiber through the third polarization controller, and the third polarization controller controls the polarization state of the polarized light entering the second polarization-maintaining fiber. The polarized light passes through the first port of the second circulator, is output from its second port, passes through the third polarization-maintaining fiber, and then passes through the first port of the first circulator, from its second port to the third port, enters branch one, and is output from the combiner taking the horizontally polarized light combined beam.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1) The present invention can realize the switching of three optical paths by adjusting the first polarization controller, the second polarization controller and the third polarization controller.

[0017] 2) The present invention can realize channel interval switching, and can realize a variety of switchable wavelength interval combinations by replacing the polarization-maintaining optical fiber.

[0018] 3) The present invention has a simple structure, low cost, and good stability of the transmission spectrum. The multi-wavelength fiber laser designed on this basis can realize the switching of channel intervals and has high power stability and wavelength stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of an optical fiber filter with adjustable channel spacing based on cross-interference according to a preferred embodiment of the present invention.

[0020] Figure 2 It is a transmission spectrum output diagram of the first channel spacing of an optical fiber filter with adjustable channel spacing based on cross-interference in a preferred embodiment of the present invention.

[0021] Figure 3 It is a transmission spectrum output diagram of the second channel spacing of an optical fiber filter with adjustable channel spacing based on cross-interference in a preferred embodiment of the present invention.

[0022] Figure 4 This is a transmission spectrum output diagram of the third channel spacing of an optical fiber filter with adjustable channel spacing based on cross-interference in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0023] In order to more clearly illustrate the embodiments of the present invention, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other accompanying drawings and other implementation methods can be obtained based on these accompanying drawings without creative work.

[0024] This embodiment is a fiber filter with adjustable channel spacing based on cross-interference, and its structure is as follows: Figure 1 As shown, it includes a broadband light source 1, an isolator 2, a polarizer 3, a first polarization controller 4-1, a polarization beam splitter 5-1, a second polarization controller 4-2, a first polarization-maintaining fiber 6-1, a first circulator 7-1, a third polarization controller 4-3, a second polarization-maintaining fiber 6-2, a second circulator 7-2, a third polarization-maintaining fiber 6-3, a beam combiner 5-2, and a spectrum analyzer 8. The specific connection structure of each component is as follows:

[0025] The broadband light source 1, the isolator 2, the polarizer 3, the first polarization controller 4-1 and the a port of the polarization beam splitter 5-1 are connected in sequence through optical fibers; the b port of the first polarization beam splitter 5-1, the second polarization controller 4-2, the first polarization-maintaining fiber 6-1 and the 1 port of the first circulator 7-1 are connected in sequence through optical fibers; the c port of the first polarization beam splitter 5-1, the third polarization controller 4-3, the second polarization-maintaining fiber 6-2 and the 1 port of the second circulator 7-2 are connected in sequence through optical fibers; the 2 port of the first circulator 7-1, the third polarization-maintaining fiber 6-3 and the 2 port of the second circulator 7-2 are connected in sequence through optical fibers; the b port and the c port of the first combiner 5-2 are connected to the 3 ports of the first circulator 7-1 and the second circulator 7-2 respectively; the a port of the first combiner 5-2 is connected to the spectrometer 8 through optical fibers.

[0026] In this embodiment, the first polarization-maintaining optical fiber, the second polarization-maintaining optical fiber, and the third polarization-maintaining optical fiber have different lengths or birefringence indices.

[0027] The principle of the present invention will be further described below in conjunction with the above structure:

[0028] The light output by the wide-spectrum light source 1 is converted into polarized light with controllable polarization state after passing through the isolator 2, the polarizer 3, and the first polarization controller 4-1 in sequence. The polarization beam splitter 5-1 decomposes the polarized light into two mutually orthogonal linear polarized lights, which are coupled into branch 1 and branch 2 respectively. The linear polarized light of branch 1 passes through the second polarization controller 4-2 and the first polarization-maintaining fiber 6-1 in sequence. The linear polarized light entering the first polarization-maintaining fiber 6-1 will be decomposed into two orthogonal vector modes, which propagate on the fast and slow axes of the first polarization-maintaining fiber 6-1 respectively. Due to the effective refractive index difference between the fast and slow axes, these two orthogonal vector modes will produce a phase difference related to the wavelength. By adjusting the second polarization controller 4-2, the polarization state of the polarized light is parallel to the fast and slow axes of the polarization-maintaining fiber, and the wavelength-related phase difference can be eliminated. The polarized light is guided by the first circulator 7-1, input from port 1, output from port 2, passes through the third polarization-maintaining fiber 6-3, and then is guided by the second circulator 7-2, from port 2 to port 3, enters branch 2, and is output by the combiner 5-2 as a vertically polarized light beam. Similarly, the linearly polarized light of branch 2 passes through the third polarization controller 4-3 and the second polarization-maintaining fiber 6-2 in sequence, and the third polarization controller 4-3 controls the polarization state of the polarized light entering the polarization-maintaining fiber. The polarized light is guided by the second circulator 7-2, input from port 1, output from port 2, passes through the third polarization-maintaining fiber 6-3, and then is guided by the first circulator 7-2, from port 2 to port 3, enters branch 1, and is output by the combiner 5-2 as a horizontally polarized light beam. Branch 1 and branch 2 are connected through the first circulator, the third polarization-maintaining fiber, and the second circulator to form cross interference. The combined light output is observed by the spectrometer 8 (AQ6370B).

[0029] The method of using this embodiment is as follows:

[0030] Turn on the broadband light source, adjust the light source power, select the appropriate polarization-maintaining fiber, adjust the first polarization controller to select the target working branch, and adjust the polarization controller (second or third polarization controller) of the corresponding branch to obtain the comb spectrum. The first output spectrum of branch 2 is as follows: Figure 2 As shown, the output spectrum of branch one is Figure 3 As shown, the second output spectrum of branch 2 is Figure 4 shown.

[0031] In summary, the present invention can switch the working branch by adjusting the first polarization controller, thereby realizing wavelength interval switching without replacing the device, and can obtain more wavelength interval switchable combinations by replacing the polarization-maintaining optical fiber.

[0032] It should be noted that the above description is only a detailed description of the preferred embodiments and principles of the present invention. For ordinary technicians in this field, there will be changes in the specific implementation methods based on the ideas provided by the present invention, and these changes should also be regarded as the scope of protection of the present invention.

Claims

1. An optical fiber filter with adjustable channel spacing based on cross-interference, characterized in that: It includes a polarizer, a first polarization controller, a polarization beam splitter, a second polarization controller, a first polarization-maintaining fiber, a first circulator, a third polarization controller, a second polarization-maintaining fiber, a second circulator, a third polarization-maintaining fiber, and a beam combiner; the polarizer, the first polarization controller, and the polarization beam splitter are connected in sequence; the polarization beam splitter divides into a first branch and a second branch, wherein, in branch one, the output port one of the polarization beam splitter is connected in sequence with the second polarization controller and the first polarization-maintaining fiber; in branch two, the output port two of the polarization beam splitter is connected in sequence with the third polarization controller and the second polarization-maintaining fiber; the output port of the first polarization-maintaining fiber is connected to the first port of the first circulator, the output port of the second polarization-maintaining fiber is connected to the first port of the second circulator, the second port of the first circulator is connected to the second port of the second circulator through the third polarization-maintaining fiber, and the third port of the first circulator and the third port of the second circulator are respectively connected to the two input ports of the beam combiner.

2. The optical fiber filter with adjustable channel spacing based on cross-interference as claimed in claim 1, characterized in that: The polarizer is connected to a broad spectrum light source through an isolator.

3. The optical fiber filter with adjustable channel spacing based on cross-interference as claimed in claim 1, characterized in that: The output port of the polarization beam combiner is connected to a spectrum analyzer.

4. The optical fiber filter with adjustable channel spacing based on cross-interference as claimed in claim 1, characterized in that: The first polarization-maintaining optical fiber, the second polarization-maintaining optical fiber, and the third polarization-maintaining optical fiber have different lengths or birefringences.

5. An optical fiber filter with adjustable channel spacing based on cross-interference as claimed in any one of claims 1 to 4, characterized in that: The output light intensity of the two output ports of the polarization beam splitter is changed by adjusting the first polarization controller to achieve working branch switching.

6. A fiber filtering method with adjustable channel spacing based on cross-interference, based on the fiber filter according to claim 2, characterized in that: The optical fiber filtering method is specifically as follows: The light output by the wide-spectrum light source is converted into polarized light with controllable polarization state after passing through an isolator, a polarizer, and a first polarization controller in sequence. The polarization beam splitter decomposes the polarized light into two mutually orthogonal linear polarized lights, which are coupled into branch one and branch two respectively. The linear polarized light of branch one enters the first polarization-maintaining optical fiber through the second polarization controller. The linear polarized light entering the first polarization-maintaining optical fiber is decomposed into two orthogonal vector modes, which propagate on the fast and slow axes of the first polarization-maintaining optical fiber respectively. The linear polarized light passes through the first port of the first circulator, is output from its second port, and passes through the third polarization-maintaining optical fiber. The polarized optical fiber enters the first port of the second circulator, passes through its second port to the third port, enters branch two, and is output by the combiner taking the vertically polarized light combined beam; the linearly polarized light of branch two enters the second polarization-maintaining optical fiber through the third polarization controller, and the third polarization controller controls the polarization state of the polarized light entering the second polarization-maintaining optical fiber. The polarized light passes through the first port of the second circulator, is output from its second port, passes through the third polarization-maintaining optical fiber, and then passes through the first port of the first circulator, passes through its second port to the third port, enters branch one, and is output by the combiner taking the horizontally polarized light combined beam.

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