Spectrum analyzer and working method thereof

Abstract

The invention provides a spectrum analyzer and a working method thereof, the spectrum analyzer comprises a polarization rotation assembly, a light detector and a processor, and the light detector is connected with the processor; the adjustable filter selects a part of wavelength of a spectrum to enter a polarization rotation component (PRE), and the PRE is composed of a half-wave plate, a quarter-wave plate, a reflector, a quarter-wave plate and a half-wave plate in sequence. The wavelength selected by the adjustable filter passes through the polarization rotation assembly PRE and then reversely enters the adjustable filter again, light output by the adjustable filter enters the light detector to obtain an electric signal, and the electric signal enters the processor for spectral analysis; according to the invention, the PRE is utilized to reduce the polarization dependent loss of the system, so that the scanning range of the spectrometer is enlarged, and the spectrum analyzer can cover the wavelength range of about 400nm.

Description

Technical Field

[0001] The present application relates to the field of spectral technology, and in particular to a spectrum analyzer and a working method thereof. Background Art

[0002] When performing spectrum analysis using an optical spectrum analyzer (OSA) with a tunable filter, the performance is usually limited by polarization dependent loss (PDL).

[0003] In order to reduce polarization-dependent loss, a quarter-wave plate (QWP) is usually used in the prior art to eliminate the influence of PDL on spectral measurement. This method is suitable for spectrometers with a small scanning range (about 4% of the wavelength). For example, in the communication band, for a 1.5um spectrometer, the use of QWP can effectively optimize PDL within a working range of 60nm. As the wavelength range expands, other technologies must be used to replace QW to effectively eliminate the PDL generated by the tunable filter, thereby expanding the wavelength scanning range of the spectrometer. Summary of the invention

[0004] The present application provides a target identification method, device, equipment and storage medium to at least solve the above technical problems existing in the prior art.

[0005] According to a first aspect of the present application, a spectrum analyzer is provided, the spectrum analyzer comprising: an adjustable filter, a polarization rotation component, a light detector and a processor, the light detector being connected to the processor;

[0006] The tunable filter selects a part of the wavelengths of the spectrum to enter the polarization rotation component PRE, wherein PRE is composed of a half-wave plate, a quarter-wave plate, a reflector, a quarter-wave plate, and a half-wave plate in sequence; after the wavelength selected by the tunable filter passes through PRE, it enters the tunable filter again in reverse, and the light output by the tunable filter enters the photodetector to obtain an electrical signal, and the electrical signal enters the processor for spectral analysis.

[0007] In one possible implementation manner, a slow axis direction of the quarter wave plate is different from a slow axis direction of the half wave plate.

[0008] In one embodiment, the slow axis direction of the quarter wave plate and the slow axis direction of the half-axis wave plate satisfy the following relationship:

[0009]

[0010] Among them, θ q is one-quarter of the slow axis direction, θh is the slow axis direction of the half-wave plate.

[0011] In one embodiment, the slow axis direction of the quarter wave plate is The slow axis direction of the half-wave plate is

[0012] In one possible implementation manner, the reflector is a plane reflector, and a reflective surface of the reflector is coated with a high-reflection film.

[0013] According to a second aspect of the present application, a working method of a spectrum analyzer is provided, the method comprising:

[0014] Selecting a portion of the wavelength of the input spectrum using a tunable filter;

[0015] Select a portion of the wavelengths of the spectrum to enter a polarization rotation assembly PRE, wherein the PRE is composed of a half-wave plate, a quarter-wave plate, a reflector, a quarter-wave plate, and a half-wave plate in sequence, and the wavelength selected by the tunable filter passes through the PRE and then enters the tunable filter in reverse again;

[0016] The light output by the tunable filter enters the photodetector to obtain an electrical signal, and the electrical signal enters the processor for spectral analysis.

[0017] In one possible implementation manner, a slow axis direction of the quarter wave plate is different from a slow axis direction of the half wave plate.

[0018] In one embodiment, the slow axis direction of the quarter wave plate and the slow axis direction of the half-axis wave plate satisfy the following relationship:

[0019]

[0020] Among them, θ q is one-quarter of the slow axis direction, θ h is the slow axis direction of the half-wave plate.

[0021] In one embodiment, the angle between the slow axis direction of the quarter wave plate and the X axis is The angle between the slow axis direction of the half-wave plate and the X-axis is

[0022] In one possible implementation manner, the reflector is a plane reflector, and the reflective surface of the reflector is coated with a high-reflective film.

[0023] The spectrum analyzer and working method of the present application, in which the tunable filter receives the spectrum to be measured, and the tunable filter selects a part of the wavelength to enter the polarization rotation element (called PRE), and the PRE is composed of a half-wave plate, a quarter-wave plate, a reflector, a quarter-wave plate, and a half-wave plate in sequence. After the wavelength selected by the tunable filter passes through the PRE, it enters the tunable filter again in the reverse direction. Its output light enters the photodetector (Photodetector) and is converted into an electrical signal, and enters the processor for spectrum analysis. The present invention eliminates the PDL generated by the tunable filter in a wide wavelength range by the appropriate coordination of the quarter-wave plate and the half-wave plate in the PRE, thereby improving the wavelength scanning range of the OSA based on the tunable filter.

[0024] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present application, nor is it intended to limit the scope of the present application. Other features of the present application will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] By reading the detailed description below with reference to the accompanying drawings, the above and other purposes, features and advantages of the exemplary embodiments of the present application will become readily understood. In the accompanying drawings, several embodiments of the present application are shown in an exemplary and non-limiting manner, wherein:

[0026] In the drawings, the same or corresponding reference numerals represent the same or corresponding parts.

[0027] Figure 1 A schematic diagram of the structure of the spectrum analyzer according to an embodiment of the present application is shown;

[0028] Figure 2 The structure diagram of the existing spectrum analyzer is shown;

[0029] Figure 3 A schematic diagram of the Poincare polarization sphere according to an embodiment of the present application is shown;

[0030] Figure 4 The slow axis of the HWP in the embodiment of the present application is shown, and the direction of the output linear polarization is a mirror image of the input linear polarization relative to the slow axis of the HWP;

[0031] Figure 5 A simulation schematic diagram of a single HWP according to an embodiment of the present application is shown;

[0032] Figure 6 A schematic diagram showing two HWPs on the equator of the Poincare sphere and corresponding polarization state changes according to an embodiment of the present application is shown;

[0033] Figure 7A simulation schematic diagram of a dual HWP of an optical spectrum analyzer according to an embodiment of the present application is shown;

[0034] Figure 8 The simulation diagram of the spectrum analyzer HWP+QWP of the embodiment of the present application is shown Figure 1 ;

[0035] Fig. 9 The simulation diagram of the spectrum analyzer HWP+QWP of the embodiment of the present application is shown Figure 2 ;

[0036] Fig.10 The simulation diagram of the spectrum analyzer HWP+QWP of the embodiment of the present application is shown Figure 3 ;

[0037] Fig.11 A schematic diagram showing the steps of the working method of the spectrum analyzer according to the embodiment of the present application is shown;

[0038] Fig.12 A schematic diagram of the structure of an electronic device according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0039] In order to make the purpose, features, and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0040] A spectrum analyzer and a working method thereof provided by the present application are introduced below in conjunction with the accompanying drawings.

[0041] like Figure 1 As shown, the basic working principle of the spectrum analyzer provided by the present application is to make the light pass through the tunable filter twice in the optical path, and rotate the polarization state by 90 degrees between the first and second times, so that the PDL generated by the first pass through the tunable filter and the PDL generated by the second pass through the tunable filter cancel each other out. The core component of this method is the polarization rotation component, which can also be called the polarization rotation element. It is an optical device that can rotate the polarization of light in the opposite direction by 90 degrees. In specific implementation, Figure 1 As shown, it uses a half-wave plate + a quarter-wave plate + a reflector + a quarter-wave plate + a half-wave plate to achieve the effect of three half-wave plates.

[0042] The traditional approach is to use a half-wave plate, such as Figure 2As shown, it uses 1 / 4 wave plate + reflector + 1 / 4 wave plate to achieve the effect of half-wave plate. The principle is that the electric field of the incident beam can be decomposed into two components, X and Y. Each of these two orthogonal components passes through the adjustable filter and QWP twice. For the X component, the first pass through the filter is X polarization, and the second pass is Y polarization. The reason is that passing through the QWP twice will rotate the polarization 90 degrees. For the Y component, the first pass through the filter is Y polarization, and the second pass will become X polarization. The polarization rotation component provided in the present application can make the PDL of the two components of the incident light cancel each other after passing through the adjustable filter twice. Therefore, PDL becomes zero. Thus, the polarization direction of the PDL input light of the entire system is irrelevant.

[0043] To be precise, the above description is only correct for one wavelength. The reason is that the QWP is a wavelength-sensitive component. If the wavelength of the incident light deviates from the preset wavelength, the quarter-wave plate QWP will no longer work as expected. Generally speaking, if Figure 2 The quarter wave plate is used as a single element to eliminate PDL, and its effective range is about 4% of the wavelength value. If the wavelength is around 1.5um, the corresponding wavelength working range is about 60nm. This characteristic limits Figure 2 Application range of spectrometer.

[0044] In order to extend the wavelength scanning range of the spectrometer, the present application proposes the following Figure 1 The structure of the new CMOS image sensor is a fundamental improvement of the polarization rotation component, so that the wavelength scanning range can be extended to 400nm.

[0045] like Figure 1 As shown, the present application provides a spectrum analyzer, the spectrum analyzer comprising: the spectrum analyzer comprising: an adjustable filter, a polarization rotation component, a light detector and a processor, the light detector being connected to the processor;

[0046] The tunable filter selects a portion of wavelengths of the spectrum to enter the polarization rotation element (PRE), wherein the PRE is composed of a half-wave plate, a quarter-wave plate, a reflector, a quarter-wave plate, and a half-wave plate in sequence; after the wavelength selected by the tunable filter passes through the PRE, it enters the tunable filter again in reverse, and the light output by the tunable filter enters the photodetector to obtain an electrical signal, and the electrical signal enters the processor for spectral analysis.

[0047] Figure 1The structural block diagram of the spectrum analyzer provided in this application, the spectrum to be measured is input to the tunable filter, and the tunable filter can be an angle-tuned thin-film filter or a filter based on a diffraction grating. It should be noted that the PDL of the tunable filter usually increases with the increase of the wavelength range. In the near-infrared range of 1.2 to 1.6um, within the range of 400nm, the PDL of the diffraction grating is likely to exceed 2dB.

[0048] Relative to Figure 2 The structure, such as Figure 1 As shown, in the present application, the composite wave plate uses a combination of a quarter-wave plate QWP and a half-wave plate (huarter-wave plate, HWP) to replace the quarter-wave plate QWP, so as to expand the bandwidth from 4% to more than 25% of the wavelength (about 400nm, near the wavelength of 1.5um). In the present application, after passing through the tunable filter, the light passes through the half-wave plate and the quarter-wave plate, is reflected by the reflector, changes direction, passes through the quarter-wave plate and the half-wave plate again along the original route, and then passes through the tunable filter to the light detector. In this process, passing through the QWP twice in a row is equivalent to passing through one HWP. Therefore, physically speaking, it is equivalent to the light selected by the tunable filter passing through three HWPs in a row, and the slow axis direction of the third HWP is the same as the slow axis direction of the first HWP. And these three consecutive HWPs are the polarization rotation components PRE mentioned above.

[0049] In summary, the spectrum to be measured passes through the tunable filter twice, and between the two times, it passes through the PRE, which rotates the polarization direction of the light by 90 degrees. The above method produces two effects: the resolution of the spectrum is improved due to passing through the tunable filter twice; and because the polarization states of these two times are orthogonal, the PDL generated by the first and second passes through the tunable filter cancel each other out.

[0050] The spectrum analyzer provided in the present application gradually selects some wavelengths to enter the light detector through an adjustable filter, and adds PRE in the light path so that the polarization directions of the light passing through the adjustable filter for the first and second times are orthogonal, thereby eliminating the PDL generated by the adjustable filter.

[0051] It should be noted that all polarization-related angles in this application are based on the direction of the X-axis.

[0052] like Figure 3As shown, when understanding the effects of polarized light, the Poincare polarization sphere can be used to describe it. Each point on the sphere represents a polarization state. Linearly polarized light is located at the equator, and circularly polarized light is located at the North Pole and South Pole. The remaining points on the sphere correspond to elliptical polarization. The azimuth angle φ on the sphere is twice the actual polarization angle θ (relative to the x-direction) of the linearly polarized light. For example, a point on the equator that is +90 degrees from the X-axis represents +45 degrees linear polarization; a wave plate with a slow axis at +20 degrees from the X-axis is expressed on the sphere as a point on the equator that is at +40 degrees relative to the X-axis. By Figure 3 The equator of the Poincare sphere and the relationship between φ and θ can be seen.

[0053] like Figure 4 As shown, the half-wave plate (HWP) can change the polarization direction of incident linear polarized light. Specifically, the slow axis of the HWP is at an angle θ h , the polarization angles of the incident and output linearly polarized light are θ in and θ out . Essentially, the output polarization vector is the mirror image of the input polarization vector relative to the HWP slow axis. In a special case, if the input polarization is at a 45-degree angle to the HWP slow axis, the output polarization is at a 90-degree angle to the input polarization. Since the HWP is equivalent to two quarter-wave plates QWP connected in series, the light between the tunable filter and the wave plate, the light transmitted to the right, if the polarization state is in the X direction, passes through the wave plate, is reflected by the reflector, and then passes through the wave plate to the left, its polarization state will be converted to the Y direction, and vice versa.

[0054] In this application, in order to calculate how the wave plate changes the polarization of the incident light, for each wave plate, a matrix can be obtained according to its slow axis direction and the amount of phase delay. For example, for a wave plate with a slow axis in the X direction and a phase delay near π, its characteristic matrix is

[0055]

[0056] When δ=0, W 0 Represents a half-wave plate HWP, and the corresponding wavelength is λ 0 , when the wavelength shifts λ 0 When it becomes λ, the phase delay of this wave plate will deviate from π, and the phase shift δ is

[0057]

[0058] If the slow axis makes an angle θ with the X axis, then the above characteristic matrix becomes

[0059]

[0060] in,

[0061]

[0062] It should be noted that for an ideal HWP (slow axis is 45 degrees), at a specific wavelength, if the polarization of the incident light is along the X direction, all the light will be in the Y direction after passing through the wave plate. When deviating from the design wavelength, the phase delay is no longer 180 degrees. In this case, some light will remain in the X direction. In this application, the wavelength range where the residual power is less than -30dB is defined as the bandwidth of the HWP.

[0063] For the estimation of HWP bandwidth, specifically, assuming that the polarization vector entering the wave plate is in the X direction and the slow axis of the wave plate is in the 45-degree direction, the incident polarization vector and the outgoing polarization vector are

[0064]

[0065] According to formulas (2) and (3), the output polarization is

[0066]

[0067] The optical powers in the X and Y directions are,

[0068] It can be seen that when δ = 0, it is an ideal HWP, so P x =0,P y = 1. All power in the X direction is converted to the Y direction. If the phase bandwidth is defined as P x <10 -3 , then δ must be less than 3.6 degrees. Its full range is 7.2 degrees (= ± 3.6 degrees), which is about 4% of 180 degrees. In other words, if the HWP is designed for 1550 nanometers, according to the above definition, its bandwidth is about 60 nanometers. The above expression calculates the energy distribution of horizontally polarized light after passing through the HWP. Only when delta = 0, all the energy is transferred to the Y direction. Its energy distribution is as follows Figure 5 As shown,

[0069] Figure 5 The output power in the X (blue) and Y (red) directions near 1550nm is shown. At 1550nm, it is an ideal HWP, so P x =0,P y =1. When the wavelength deviates from 1550nm, P y Slowly decreasing, while P x Growing rapidly. Wavelength range P X <-30dB is about 60 nanometers.

[0070] From the above calculation, we know that using a single HWP to rotate the input polarization direction by 90 degrees will only result in a bandwidth of 60nm. Therefore, the following describes how to use two HWPs to increase the bandwidth.

[0071] Figure 6 The Poncare phase of the double wave plate method is shown. The initial X polarization is from φ in =0 becomes φ 1 =2φ h1 Then the second HWP takes the azimuth angle φ 1 Go to φ out The slow axes of these two wave plates are at θ h1 and θ h2 In order to convert the input X-polarized light into Y-polarized light (φ out =π), the two angles of the slow axis must satisfy the relationship,

[0072] At this time, the feature matrix is

[0073]

[0074] Convert to

[0075]

[0076] Through numerical calculation, the optimal solution is obtained as

[0077]

[0078] like Figure 7 P x (blue) and P y (red) as a function of wavelength. At 1550 nm (P x ,P y )=(0,1), indicating that this is an ideal HWP. -30dB bandwidth (for P x ) is about 360nm, which is six times the bandwidth of a single wave plate. In summary, the combination of dual HWPs significantly improves the bandwidth. However, it cannot be used in Figure 2 In the configuration shown, the light passes through the optics twice.

[0079] In order to enhance the bandwidth of the wave plate and improve Figure 2 In the PDL, this application proposes Figure 1 The structure shown in the figure, in which the HWP and QWP are placed in series in the optical path. Structurally, Figure 1 The optical fiber includes HWP and QWP, but optically, it is equivalent to having 3 HWPs, wherein the slow axis direction of the third HWP is the same as that of the first HWP.

[0080] Figure 8 The phase of the wave plate slow axis and polarization state vector on the Poncare sphere is shown. The initial azimuth and the corresponding angle after each rotation are (0,φ 1 ,φ 2 ,φ 3 ). In order to achieve φ 3 =π(Y polarization), the slow axis directions of QWP and HWP must satisfy the relationship According to the above calculation method, the optimized solution is θ q is one-quarter of the slow axis direction, θ h is the slow axis direction of the half-wave plate. Fig. 9 The calculated results are shown in Figure 1. The Px (blue) and Py (red) of the HWP+QWP have a central wavelength of 1550 nanometers, and the -30dB bandwidth can reach 384 nanometers, centered around 1550 nanometers. In other words, the slow axis direction of the quarter-wave plate is The slow axis direction of the half-wave plate is

[0081] In some embodiments, the reflector is a plane reflector, and the reflective surface of the reflector is coated with a high-reflective film and is perpendicular to the optical axis.

[0082] like Fig.10 As shown, the spectrum analyzer provided by the present application simulates Px (blue) and Py (red) of HWP+QWP, with a central wavelength of 1425nm. Between 1270nm and 1623nm, Px is less than -30dB. In the related art, the wavelengths used in the communications industry range from O-band to L-band. If the design wavelength of the wave plate is moved to 1425nm, then Px will be less than -30dB between the wavelengths (1270nm, 1623nm).

[0083] The spectrum analyzer provided in the present application utilizes a combination of a quarter-wave plate QWP and a half-wave plate HWP to extend the bandwidth to about 400 nanometers nm, avoiding the influence of polarization-dependent loss PDL of the tunable filter, and extending the operating wavelength range of the spectrum analyzer several times.

[0084] The spectrum analyzer provided in the present application increases the bandwidth by using a quarter wave plate and a half wave plate to reduce the PDL of the broadband tunable filter, thereby increasing the usable range of the spectrum analyzer. In addition, the tunable filter in the present application can be achieved by using a MEMS mirror and a grating, so the spectrum analyzer formed is a small spectrum analyzer that can cover a wavelength range of about 400nm.

[0085] like Fig.11As shown, an embodiment of the present application provides a working method of a spectrum analyzer, the method comprising:

[0086] S101, selecting a portion of wavelengths of an input spectrum using a tunable filter;

[0087] S102, selecting a portion of wavelengths of the spectrum to enter a polarization rotation component, wherein the polarization rotation component is composed of a half-wave plate, a quarter-wave plate, and a reflector, and the spectrum of the selected wavelengths passes through the half-wave plate, the quarter-wave plate, the reflector, the quarter-wave plate, and the half-wave plate, and then enters the tunable filter in the reverse direction again;

[0088] S103, the light output by the tunable filter enters a photodetector to obtain an electrical signal, and the electrical signal enters a processor for spectral analysis.

[0089] In some embodiments, the slow axis direction of the quarter wave plate is different from the slow axis direction of the half wave plate.

[0090] The slow axis direction of the quarter wave plate and the slow axis direction of the half-axis wave plate satisfy the following relationship:

[0091]

[0092] Among them, θ q is one-quarter of the slow axis direction, θ h is the slow axis direction of the half-wave plate.

[0093] The angle between the slow axis direction of the quarter wave plate and the X axis is The angle between the slow axis direction of the half-wave plate and the X-axis is

[0094] In some embodiments, the reflector is a plane reflector, and the reflective surface of the reflector is coated with a high-reflection film axis.

[0095] The working method of the spectrum analyzer provided in the present application is that the spectrum to be measured enters the output end of the spectrometer, passes through the tunable filter, the polarization rotation component PRE in sequence, and then passes through the tunable filter again, and its output light enters the photodetector and the processor for spectral analysis. The present application expands the bandwidth by using a quarter-wave plate and a half-wave plate, reduces the PDL of the broadband tunable filter, and improves the available range of the OSA based on the tunable filter.

[0096] An embodiment of the present application provides an electronic device, including:

[0097] at least one processor; and

[0098] a memory communicatively connected to the at least one processor; wherein,

[0099] The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method described in any one of the above embodiments.

[0100] An embodiment of the present application provides a non-transitory computer-readable storage medium storing computer instructions, wherein the computer instructions are used to enable a computer to execute the method described in any of the above embodiments.

[0101] According to an embodiment of the present application, the present application also provides an electronic device and a readable storage medium.

[0102] Fig.12 A schematic block diagram of an example electronic device 800 that can be used to implement an embodiment of the present application is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workbenches, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present application described and / or required herein.

[0103] like Fig.12 As shown, the device 800 includes a computing unit 801, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 802 or a computer program loaded from a storage unit 808 into a random access memory (RAM) 803. In the RAM 803, various programs and data required for the operation of the device 800 can also be stored. The computing unit 801, the ROM 802, and the RAM 803 are connected to each other via a bus 804. An input / output (I / O) interface 805 is also connected to the bus 804.

[0104] A number of components in the device 800 are connected to the I / O interface 805, including: an input unit 806, such as a keyboard, a mouse, etc.; an output unit 807, such as various types of displays, speakers, etc.; a storage unit 808, such as a disk, an optical disk, etc.; and a communication unit 809, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 809 allows the device 800 to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks.

[0105] The computing unit 801 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the computing unit 801 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, digital signal processors (DSPs), and any appropriate processors, controllers, microcontrollers, etc. The computing unit 801 performs the various methods and processes described above, such as the working method of the spectrometer. For example, in some embodiments, the working method of the spectrometer may be implemented as a computer software program, which is tangibly contained in a machine-readable medium, such as a storage unit 808. In some embodiments, part or all of the computer program may be loaded and / or installed on the device 800 via the ROM 802 and / or the communication unit 809. When the computer program is loaded into the RAM 803 and executed by the computing unit 801, one or more steps of the working method of the spectrometer described above may be performed. Alternatively, in other embodiments, the computing unit 801 may be configured to perform the working method of the spectrometer by any other appropriate means (e.g., by means of firmware).

[0106] Various implementations of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), complex programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include: being implemented in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0107] The program code for implementing the method of the present application can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that the program code, when executed by the processor or controller, implements the functions / operations specified in the flow chart and / or block diagram. The program code can be executed entirely on the machine, partially on the machine, partially on the machine and partially on a remote machine as a stand-alone software package, or entirely on a remote machine or server.

[0108] In the context of the present application, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or equipment, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0109] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including acoustic input, voice input, or tactile input).

[0110] The systems and techniques described herein may be implemented in a computing system that includes back-end components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes front-end components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such back-end components, middleware components, or front-end components. The components of the system may be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: a local area network (LAN), a wide area network (WAN), and the Internet.

[0111] A computer system may include a client and a server. The client and the server are generally remote from each other and usually interact through a communication network. The relationship of client and server is generated by computer programs running on respective computers and having a client-server relationship with each other. The server may be a cloud server, a server of a distributed system, or a server combined with a blockchain.

[0112] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this application can be executed in parallel, sequentially or in different orders, as long as the expected results of the technical solution of this application can be achieved, and this document does not limit this.

[0113] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0114] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A spectrum analyzer, characterized in that: The spectrum analyzer comprises: an adjustable filter, a polarization rotation component PRE, a light detector and a processor, wherein the light detector is connected to the processor; The tunable filter selects a part of the wavelengths of the spectrum to enter the polarization rotation component PRE, wherein PRE is composed of a half-wave plate, a quarter-wave plate, a reflector, a quarter-wave plate, and a half-wave plate in sequence; after the wavelength selected by the tunable filter passes through PRE, it enters the tunable filter again in reverse, and the light output by the tunable filter enters the photodetector to obtain an electrical signal, and the electrical signal enters the processor for spectral analysis.

2. The spectrum analyzer according to claim 1, characterized in that: The slow axis direction of the quarter wave plate is different from the slow axis direction of the half wave plate.

3. The spectrum analyzer according to claim 2, characterized in that: The slow axis direction of the quarter wave plate and the slow axis direction of the half-axis wave plate satisfy the following relationship: Among them, θ q is one-quarter of the slow axis direction, θ h is the slow axis direction of the half-wave plate.

4. The spectrum analyzer according to claim 3, characterized in that: The angle between the slow axis direction of the quarter wave plate and the X axis is The angle between the slow axis direction of the half-wave plate and the X-axis is 5. The spectrum analyzer according to claim 4, characterized in that: The reflector is a plane reflector, and the reflective surface of the reflector is coated with a high-reflection film axis.

6. A method for operating a spectrum analyzer, characterized in that: The method comprises: Selecting a portion of the wavelength of the input spectrum using a tunable filter; Select a portion of the wavelengths of the spectrum to enter a polarization rotation component PRE, wherein the PRE is composed of a half-wave plate, a quarter-wave plate, a reflector, a quarter-wave plate, and a half-wave plate in sequence, and the wavelength selected by the tunable filter passes through the PRE and then enters the tunable filter in the reverse direction again; The light output by the tunable filter enters the photodetector to obtain an electrical signal, and the electrical signal enters the processor for spectral analysis.

7. The working method according to claim 6, characterized in that: The slow axis direction of the quarter wave plate is different from the slow axis direction of the half wave plate.

8. The working method according to claim 6, characterized in that: The slow axis direction of the quarter wave plate and the slow axis direction of the half-axis wave plate satisfy the following relationship: Among them, θ q is one-quarter of the slow axis direction, θ h is the slow axis direction of the half-wave plate.

9. The working method according to claim 6, characterized in that: The angle between the slow axis direction of the quarter wave plate and the X axis is The angle between the slow axis direction of the half-wave plate and the X-axis is 10. The working method according to claim 6, characterized in that: The reflector is a plane reflector, and the reflective surface of the reflector is coated with a high-reflection film axis.

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