Reconfigurable optical add-drop multiplexer and optical communication system

Abstract

Embodiments of the present application provide a reconfigurable optical add-drop multiplexer (ROADM) and an optical communication system. The ROADM includes a light source, a filter, a coherent detection device, a processing module, and a wavelength selective switch (WSS). Based on the optical signal from the calibration of the previous hop ROADM and the alignment of the light source by the coherent detection device, the WSS is calibrated with the optical signal generated by the aligned light source, so that the frequency offset of the WSS can be calibrated more accurately.

Description

Technical Field

[0001] This application relates to the field of optical communication technology, and in particular to a reconfigurable optical add-drop multiplexer and an optical communication system. Background Technology

[0002] In communication systems, optical signals pass through multiple network nodes during transmission. These network nodes can be reconfigurable optical add / drop multiplexers (ROADMs). A ROADM is a device or equipment used in dense wavelength division multiplexing (DWDM) systems. Its function is to arbitrarily assign wavelengths for services as needed along the line, enabling flexible service scheduling. A ROADM includes a wavelength selective switch (WSS), which filters the optical signal.

[0003] During the use of ROADM, the center frequency of its WSS filter spectrum gradually shifts. When there is a frequency shift in the center frequency of the WSS filter spectrum in ROADM, it leads to asymmetrical filtering of the optical signal, thereby degrading the quality of the optical signal and reducing the performance of the optical transmission system. Therefore, how to reduce the frequency shift of the WSS filter spectrum in ROADM is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] This application discloses a reconfigurable optical add-drop multiplexer and an optical communication system, which can more accurately calibrate the frequency offset of the WSS in the reconfigurable optical add-drop multiplexer.

[0005] In a first aspect, this application provides a reconfigurable optical add-drop multiplexer (ROADM), which is a first ROADM, comprising:

[0006] Light source: used to generate the first multi-wavelength light signal;

[0007] Filter: Used to filter the aforementioned first multi-wavelength optical signal and output multiple single-wavelength optical signals; the aforementioned multiple single-wavelength optical signals include the first optical signal;

[0008] Coherent detection device: used to perform coherent detection on the aforementioned first optical signal and second optical signal; the aforementioned second optical signal is a reference signal for the aforementioned first optical signal, and the aforementioned second optical signal is an optical signal sent to the aforementioned first ROADM after frequency calibration in the second ROADM;

[0009] Processing module: Determines the frequency difference between the first optical signal and the second optical signal based on the signal obtained from the coherent detection.

[0010] The aforementioned light source is also used to generate a frequency of a multi-wavelength optical signal based on the aforementioned frequency difference alignment, and to generate a second multi-wavelength optical signal after the frequency of the multi-wavelength optical signal generated by alignment. The aforementioned second multi-wavelength optical signal is passed through the aforementioned filter to output a single-wavelength third optical signal. The aforementioned third optical signal is used to calibrate the frequency offset of the first wavelength selection switch WSS in the aforementioned first ROADM.

[0011] Optionally, the second ROADM mentioned above can be the upstream device of the first ROADM mentioned above in the communication network.

[0012] In this application, compared to existing ROADMs, the ROADM provided in this application uses an optical signal calibrated in the previous hop ROADM to align its light source, and uses the optical signal generated by this aligned light source to calibrate the frequency offset of the WSS in the ROADM provided in this application. Since the light source is already aligned, the generated optical signal is the aligned optical signal, and using the aligned optical signal to calibrate the frequency offset of the WSS can achieve more accurate calibration. In addition, for the entire optical communication system, if each ROADM uses the optical signal calibrated by the previous hop ROADM to align its own light source, and uses the optical signal generated by its own aligned light source to calibrate its own WSS, then the calibration standard of the WSS in each ROADM in the optical communication system is basically consistent, thereby achieving a smaller error between the filtering frequencies of the WSS in the ROADMs of the entire optical communication system. This can greatly reduce the filtering cost of the optical signal during the propagation process of the optical communication system, and thus improve the transmission performance of the entire optical communication system.

[0013] In one possible implementation, the aforementioned first ROADM further includes a power detection device; the aforementioned first WSS is the WSS used for outputting optical signals in the aforementioned first ROADM;

[0014] The aforementioned first WSS is used to receive the aforementioned third optical signal and output the aforementioned third optical signal to the aforementioned power detection device;

[0015] The aforementioned power detection device is used to detect the power value of the aforementioned third optical signal output from the aforementioned first WSS;

[0016] The aforementioned processing module is further configured to detect the first target frequency offset change value of the aforementioned first WSS based on the power value of the aforementioned third optical signal. The aforementioned first target frequency offset change value indicates the offset of the optical frequency corresponding to the pixel of the switching engine in the aforementioned first WSS.

[0017] In this application, the power value of the optical signal output from the WSS is detected by a power detection device, and the frequency offset change value of the WSS is calculated based on the detected power value. After obtaining the frequency offset change value, the frequency offset of the WSS can be calibrated based on the frequency offset change value.

[0018] In one possible implementation, the aforementioned second multi-wavelength optical signal, after passing through the aforementioned filter to output a single-wavelength optical signal, also includes a fourth optical signal;

[0019] The aforementioned first WSS is also used to receive the aforementioned fourth optical signal; and output the aforementioned fourth optical signal to the aforementioned power detection device;

[0020] The aforementioned power detection device is also used to detect the power value of the aforementioned fourth optical signal output from the aforementioned first WSS;

[0021] The aforementioned processing module is further configured to detect the first target frequency offset change value of the aforementioned first WSS based on the power value of the aforementioned third optical signal, including: detecting the first target frequency offset change value based on the power value of the aforementioned third optical signal and the power value of the aforementioned fourth optical signal.

[0022] Since there are some deviations in the frequency offset of different wavelength optical signals in WSS, this application uses two optical signals to detect the frequency offset of WSS in order to obtain a more accurate frequency offset change value.

[0023] In one possible implementation, the aforementioned processing module is specifically used for:

[0024] The first frequency offset change value of the first WSS is calculated based on the power value of the aforementioned third optical signal and the first reference frequency offset value. The first reference frequency offset value is the frequency offset value of the optical frequency corresponding to the channel transmitting the aforementioned third optical signal in the aforementioned first WSS relative to the first standard optical frequency, which is measured in advance.

[0025] The second frequency offset change value of the first WSS is calculated based on the power value of the aforementioned fourth optical signal and the second reference frequency offset value. The aforementioned two reference frequency offset values ​​are the frequency offset values ​​of the optical frequency corresponding to the channel transmitting the aforementioned fourth optical signal in the aforementioned first WSS relative to the second standard optical frequency, which are measured in advance.

[0026] The first target frequency offset change value is obtained by averaging the first frequency offset change value and the second frequency offset change value.

[0027] Optionally, averaging the first frequency offset change value and the second frequency offset change value can be done by directly summing the two frequency offset change values ​​and then averaging them, or by taking a weighted average.

[0028] In this application, the frequency offset change value of the WSS is measured by two optical signals respectively, and then the average value of the two frequency offset change values ​​is taken as the final frequency offset change value of the WSS, thereby obtaining a more accurate frequency offset change value, and thus more accurately realizing the frequency offset calibration of the WSS.

[0029] In one possible implementation, the aforementioned first ROADM further includes a second wavelength selection switch (WSS); the aforementioned second WSS is the WSS used for inputting optical signals in the aforementioned first ROADM;

[0030] The aforementioned second WSS is used to receive the aforementioned second optical signal and output the aforementioned second optical signal to the aforementioned coherent detection device;

[0031] The aforementioned coherent detection device is also used to detect the power value of the aforementioned second optical signal output from the aforementioned second WSS;

[0032] The aforementioned processing module is further configured to detect the second target frequency offset change value of the aforementioned second WSS based on the power value of the aforementioned second optical signal. The aforementioned second target frequency offset change value indicates the offset of the optical frequency corresponding to the pixel of the switching engine in the aforementioned second WSS.

[0033] In this application, the second optical signal, after frequency calibration in the second ROADM and sent to the first ROADM, can be used not only for light source alignment in the first ROADM but also for frequency offset calibration of the WSS (Wideband Filter) used for input optical signals in the first ROADM. Similarly, since the second optical signal is a frequency-calibrated optical signal, using the calibrated optical signal to calibrate the frequency offset of the WSS can achieve more accurate calibration. Furthermore, for the entire optical communication system, if each ROADM uses the frequency-calibrated optical signal from the previous ROADM to calibrate its own WSS used for input optical signals, then the calibration standards of the WSS used for input optical signals in each ROADM of the optical communication system are basically consistent. This results in a smaller error between the filtering frequencies of the WSS used for input optical signals in the ROADMs of the entire optical communication system, which can greatly reduce the filtering cost of optical signals propagating in the optical communication system, thereby improving the transmission performance of the entire optical communication system.

[0034] In one possible implementation, the aforementioned second WSS is further configured to receive a fifth optical signal from the aforementioned second ROADM and output the aforementioned fifth optical signal to the aforementioned coherent detection device;

[0035] The aforementioned coherent detection device is also used to detect the power value of the aforementioned fifth optical signal output from the aforementioned second WSS;

[0036] The aforementioned processing module is further configured to detect the second target frequency offset change value of the aforementioned second WSS based on the power value of the aforementioned second optical signal, including: detecting the second target frequency offset change value based on the power value of the aforementioned second optical signal and the power value of the aforementioned fifth optical signal.

[0037] Since there are some deviations in the frequency offset of different wavelength optical signals in WSS, this application uses two optical signals to detect the frequency offset of WSS in order to obtain a more accurate frequency offset change value.

[0038] In one possible implementation, the aforementioned processing module is specifically used for:

[0039] The third frequency offset change value of the aforementioned second WSS is calculated based on the power value of the aforementioned second optical signal and the third reference frequency offset value. The aforementioned third reference frequency offset value is the frequency offset value of the optical frequency corresponding to the channel transmitting the aforementioned second optical signal in the aforementioned second WSS relative to the third standard optical frequency, which is measured in advance.

[0040] The fourth frequency offset change value of the aforementioned second WSS is calculated based on the power value of the aforementioned fifth optical signal and the fourth reference frequency offset value. The aforementioned four reference frequency offset values ​​are the frequency offset values ​​of the optical frequency corresponding to the channel transmitting the aforementioned fifth optical signal in the aforementioned second WSS relative to the fourth standard optical frequency, which are measured in advance.

[0041] The second target frequency offset change value is obtained by averaging the aforementioned third frequency offset change value and the aforementioned fourth frequency offset change value.

[0042] Optionally, the average of the third and fourth frequency offset changes can be achieved by directly summing the two frequency offset changes and then averaging them, or by taking a weighted average.

[0043] In this application, the frequency offset change value of the WSS is measured by two optical signals respectively, and then the average value of the two frequency offset change values ​​is taken as the final frequency offset change value of the WSS, thereby obtaining a more accurate frequency offset change value, and thus more accurately realizing the frequency offset calibration of the WSS.

[0044] In one possible implementation, the aforementioned first WSS is further used to send the aforementioned third optical signal to the third ROADM, the aforementioned third optical signal being used to calibrate the frequency offset of the WSS in the aforementioned third ROADM and to calibrate the output frequency of the light source in the aforementioned third ROADM.

[0045] In this application, the third optical signal is the optical signal generated by the aligned light source in the first ROADM. This aligned third optical signal is sent to the next-hop ROADM to calibrate the frequency offset of the WSS used for input optical signals in the next-hop ROADM and to align the output frequency of the light source in the next-hop ROADM. This ensures that the alignment standards of the light sources in the first ROADM and the next-hop ROADM are consistent, reducing the frequency offset of the generated optical signal and improving the quality of the optical signal. Furthermore, the aligned optical signal is used to calibrate the frequency offset of the WSS used for input optical signals in the next-hop ROADM to achieve more accurate frequency offset calibration.

[0046] In one possible implementation, the aforementioned light source included in the first ROADM is an optical frequency comb generator.

[0047] This application uses an optical frequency comb generator as the light source because the optical frequency comb generator can generate equally spaced multi-wavelength optical signals. When aligning the light source, aligning with the frequency of one optical signal can align with the frequency of the entire generated multi-wavelength optical signal, thereby improving the alignment efficiency and accuracy of the light source.

[0048] Secondly, this application provides a reconfigurable optical add-drop multiplexer (ROADM), which is a second ROADM, comprising:

[0049] Light source: used to generate the first multi-wavelength light signal;

[0050] Filter: Used to filter the aforementioned first multi-wavelength optical signal and output multiple single-wavelength optical signals, the aforementioned multiple single-wavelength optical signals including the first optical signal;

[0051] Wavelength detection device: used to detect the wavelength of the aforementioned first optical signal;

[0052] Processing module: used to calculate the frequency difference between the aforementioned first optical signal and the aforementioned standard wavelength optical signal based on the wavelength of the first optical signal and the standard wavelength;

[0053] The aforementioned light source is also used to generate a frequency of a multi-wavelength optical signal based on the aforementioned frequency difference alignment, and to generate a second multi-wavelength optical signal after the frequency of the multi-wavelength optical signal generated by alignment. The aforementioned second multi-wavelength optical signal is output as a single-wavelength second optical signal through the aforementioned filter. The aforementioned second optical signal is used to calibrate the frequency offset of the first wavelength selection switch WSS in the aforementioned second ROADM.

[0054] Optionally, the aforementioned second ROADM may be the starting network node in an optical communication system, which may be connected to the user-side communication equipment.

[0055] In this application, a wavelength detection device can be used to align the ROADM provided in this application, and the optical signal generated by the aligned light source can be used to calibrate the frequency offset of the WSS in the ROADM provided in this application. Since the light source has been aligned, the generated optical signal is the aligned optical signal. Using the aligned optical signal to calibrate the frequency offset of the WSS can achieve more accurate calibration.

[0056] In one possible implementation, the aforementioned second ROADM further includes a first power detection device; the aforementioned first WSS is the WSS used for outputting optical signals in the aforementioned second ROADM;

[0057] The aforementioned first WSS is used to receive the aforementioned second optical signal and output the aforementioned second optical signal to the aforementioned first power detection device;

[0058] The aforementioned first power detection device is used to detect the power value of the aforementioned second optical signal output from the aforementioned first WSS;

[0059] The aforementioned processing module is further configured to detect a first target frequency offset change value of the aforementioned first WSS based on the power value of the aforementioned second optical signal. The aforementioned first target frequency offset change value indicates the offset of the optical frequency corresponding to the pixel of the switching engine in the aforementioned first WSS.

[0060] In this application, the power value of the optical signal output from the WSS is detected by a power detection device, and the frequency offset change value of the WSS is calculated based on the detected power value. After obtaining the frequency offset change value, the frequency offset of the WSS can be calibrated based on the frequency offset change value.

[0061] In one possible implementation, the single-wavelength optical signal output by the aforementioned filter for the aforementioned second multi-wavelength optical signal further includes a third optical signal;

[0062] The aforementioned first WSS is also used to receive the aforementioned third optical signal; and output the aforementioned third optical signal to the aforementioned first power detection device;

[0063] The aforementioned first power detection device is also used to detect the power value of the aforementioned third optical signal output from the aforementioned first WSS;

[0064] The aforementioned processing module is further configured to detect the first target frequency offset change value of the aforementioned first WSS based on the power value of the aforementioned second optical signal, including: detecting the first target frequency offset change value based on the power value of the aforementioned second optical signal and the power value of the aforementioned third optical signal.

[0065] Since there are some deviations in the frequency offset of different wavelength optical signals in WSS, this application uses two optical signals to detect the frequency offset of WSS in order to obtain a more accurate frequency offset change value.

[0066] In one possible implementation, the aforementioned processing module is specifically used for:

[0067] The first frequency offset change value of the first WSS is calculated based on the power value of the second optical signal and the first reference frequency offset value. The first reference frequency offset value is the frequency offset value of the optical frequency corresponding to the channel transmitting the second optical signal in the first WSS relative to the first standard optical frequency, which is measured in advance.

[0068] The second frequency offset change value of the first WSS is calculated based on the power value of the aforementioned third optical signal and the second reference frequency offset value. The aforementioned two reference frequency offset values ​​are the frequency offset values ​​of the optical frequency corresponding to the channel transmitting the aforementioned third optical signal in the aforementioned first WSS relative to the second standard optical frequency, which are measured in advance.

[0069] The first target frequency offset change value is obtained by averaging the first frequency offset change value and the second frequency offset change value.

[0070] Optionally, averaging the first frequency offset change value and the second frequency offset change value can be done by directly summing the two frequency offset change values ​​and then averaging them, or by taking a weighted average.

[0071] In this application, the frequency offset change value of the WSS is measured by two optical signals respectively, and then the average value of the two frequency offset change values ​​is taken as the final frequency offset change value of the WSS, thereby obtaining a more accurate frequency offset change value, and thus more accurately realizing the frequency offset calibration of the WSS.

[0072] In one possible implementation, the aforementioned first WSS is further used to send the aforementioned second optical signal to the first ROADM, the aforementioned second optical signal being used to calibrate the frequency offset of the WSS in the aforementioned first ROADM and to calibrate the output frequency of the light source in the aforementioned first ROADM.

[0073] In this application, the second optical signal is the optical signal generated by the aligned light source in the second ROADM. This aligned second optical signal is sent to the next-hop ROADM to calibrate the frequency offset of the WSS used for input optical signals in the next-hop ROADM and to align the output frequency of the light source in the next-hop ROADM. This ensures that the alignment standards of the light sources in the first ROADM and the next-hop ROADM are consistent, reducing the frequency offset of the generated optical signal and improving the quality of the optical signal. Furthermore, the aligned optical signal is used to calibrate the frequency offset of the WSS used for input optical signals in the next-hop ROADM to achieve more accurate frequency offset calibration.

[0074] In one possible implementation, the aforementioned second ROADM further includes a second power detection device and a second wavelength selection switch (WSS); the aforementioned second WSS is the WSS used for inputting optical signals in the aforementioned second ROADM;

[0075] The aforementioned second WSS is used to receive the fourth optical signal and output the aforementioned fourth optical signal to the aforementioned second power detection device;

[0076] The aforementioned second power detection device is also used to detect the power value of the aforementioned fourth optical signal output from the aforementioned second WSS;

[0077] The aforementioned processing module is further configured to detect the second target frequency offset change value of the aforementioned second WSS based on the power value of the aforementioned fourth optical signal. The aforementioned second target frequency offset change value indicates the offset of the optical frequency corresponding to the pixel of the switching engine in the aforementioned second WSS.

[0078] Optionally, the fourth optical signal may be an optical signal from a user-side device or an optical signal generated by a light source in the second ROADM.

[0079] In this application, a power detection device detects the power value of the optical signal output from the WSS (Wide Sensor) used as the input optical signal in the second ROADM, and calculates the frequency offset change value of the WSS based on the detected power value. After obtaining the frequency offset change value, the frequency offset of the WSS can be calibrated based on the frequency offset change value.

[0080] In one possible implementation, the aforementioned second WSS is further used to receive the fifth optical signal and output the aforementioned fifth optical signal to the aforementioned second power detection device;

[0081] The aforementioned second power detection device is also used to detect the power value of the aforementioned fifth optical signal output from the aforementioned second WSS;

[0082] The aforementioned processing module is further configured to detect the second target frequency offset change value of the aforementioned second WSS based on the power value of the aforementioned fourth optical signal, including: detecting the second target frequency offset change value based on the power value of the aforementioned fourth optical signal and the power value of the aforementioned fifth optical signal.

[0083] Since there are some deviations in the frequency offset of different wavelength optical signals in WSS, this application uses two optical signals to detect the frequency offset of WSS in order to obtain a more accurate frequency offset change value.

[0084] Thirdly, this application provides an optical communication system, which includes a first ROADM and a second ROADM; wherein the first ROADM is the first ROADM described in any of the first aspects above, and the second ROADM is the second ROADM described in any of the second aspects above.

[0085] It is understood that the beneficial effects that the optical communication system described in the third aspect above can achieve can be referred to the beneficial effects described in the first and second aspects above, and will not be repeated here. Attached Figure Description

[0086] The accompanying drawings used in the embodiments of this application will be described below.

[0087] Figure 1 The diagram shown is a schematic diagram of the optical communication system structure provided in this application;

[0088] Figure 2 The diagram shown is a schematic of a ROADM structure;

[0089] Figure 3 The diagram shown illustrates the structure and working principle of WSS.

[0090] Figure 4 The diagram shows a schematic of the physical structure of a silicon-based liquid crystal.

[0091] Figure 5 The diagram shows the arrangement of light spots on the pixel array of a silicon-based liquid crystal.

[0092] Figure 6 The diagram shows the power spectrum of the signal and the filtered power spectrum.

[0093] Figure 7 A schematic diagram of the structure of a ROADM provided in this application;

[0094] Figure 8 The diagram shows a transmission channel in the switching engine.

[0095] Figure 9 The figure shows a schematic diagram of the relationship between the transmission channel and the power value;

[0096] Figures 10 to 15 This is a schematic diagram of another ROADM structure provided in this application. Detailed Implementation

[0097] The embodiments of this application will now be described with reference to the accompanying drawings.

[0098] Before introducing the technical solutions provided in this application, let's first introduce the optical communication system, reconfigurable optical add / drop multiplexer (ROADM), wavelength selective switch (WSS), and switching engine in the WSS involved in this application. Examples can be found below. Figures 1 to 5 Introduction.

[0099] Optical communication systems can be structured in various network architectures, such as chain networks, ring networks, mesh networks, or other networking forms. They can be applied to a wide range of communication scenarios, including local telephone trunk lines, long-distance trunk communications, global communication networks, and public telecommunications networks in various countries. Optical communication systems can also be used for high-quality color television transmission, industrial production site monitoring and dispatching, traffic monitoring and control, urban cable television networks, community antenna television (CATV) systems, and fiber optic local area networks (LANs).

[0100] For example, Figure 1 A partial structural diagram of an optical communication system is shown. (For example...) Figure 1 As shown, the optical communication system 100 may include multiple ROADMs 101. ROADMs are used to implement add / drop, block, and pass-through configurations for optical signals of any wavelength or wavelength group. Figure 1 The optical communication system 100 is illustrated by an example comprising n ROADMs 101, where n is an integer greater than 1. These ROADMs 101 can be interconnected via optical fibers. One or more ROADMs 101 shown in the optical communication system 100 can also connect with other ROADMs (…). Figure 1 (Not shown in the image) Connections, not limited to Figure 1 The ROADM 101 shown is connected. One or more ROADMs 101 in the optical communication system 100 can be connected to user-side communication equipment. Figure 1 The illustration shows a user-side communication device 110 connected to a reconfigurable optical add-drop multiplexer 1 and a reconfigurable optical add-drop multiplexer n. The user-side communication device 110 can be an optical line terminal (OLT) device or an optical network unit (ONU) or other optical network access device.

[0101] For easier understanding of ROADM 101 above, please refer to the example provided. Figure 2 .like Figure 2 As shown, ROADM 101 includes WSS 1011, WSS 1012, add / drop wavelength selective switch (ADWSS) 1013, receiver 1014, and transmitter 1015. The add / drop wavelength selective switch can also be called an up / down wavelength selective switch.

[0102] The aforementioned WSS 1011 receives the optical signal input to ROADM 101. This input optical signal includes at least one of two types of optical signals: the first type is the optical signal received by receiver 1014, and the second type is the optical signal forwarded by ROADM 101. WSS 1011 splits the input optical signal into multiple single-wavelength optical signals. If the multiple single-wavelength optical signals include the first type of optical signal, then the first type of optical signal is sent to ADWSS 1013. If the multiple single-wavelength optical signals include the second type of optical signal, then the second type of optical signal is sent to WSS 1012.

[0103] After receiving the first type of optical signal from WSS 1011, ADWSS 1013 sends the received optical signal to receiver 1014 for reception. Additionally, ADWSS 1013 can also receive optical signals from transmitter 1015 and then send the optical signals from transmitter 1015 to WSS 1012 for transmission.

[0104] After receiving optical signals from WSS 1011 and / or ADWSS 1013, WSS 1012 couples the received optical signals into the optical fiber and transmits them.

[0105] In one possible implementation, ADWSS 1013 may consist of two WSSs: an upwave WSS and a downwave WSS. The upwave WSS can be used to receive optical signals from transmitter 1015 and then transmit the optical signals from transmitter 1015 to WSS 1012. The downwave WSS can be used to receive optical signals from WSS 1011 and transmit the received optical signals to receiver 1014.

[0106] To better understand WSS in ROADM, please refer to the example provided. Figure 3 . Figure 3A schematic diagram illustrating the structure and working principle of the WSS 300 is provided. The WSS 300 includes a grating 301, a lens 302, a switching engine 303, a reflector 304, a port 305, and a polarization conversion unit 306. Port 305 includes an input port and an output port. The input optical signal can be a multi-wavelength optical signal. After the input optical signal is input into the WSS 300 through the input port, it first passes through the polarization conversion unit 306. The polarization conversion unit 306 converts the polarization state of the input optical signal, which is then reflected by the reflector 304 to the lens 302, and then incident on the grating 301 through the lens. The grating 301 disperses the multi-wavelength optical signal into multiple single-wavelength optical signals. These multiple single-wavelength optical signals pass through the lens 302 and are reflected by the reflector 304 to the switching engine 303. The switching engine 303 changes the transmission direction of each single-wavelength optical signal, and the single-wavelength optical signals with changed transmission directions are reflected by the reflector 304 to the output port for output.

[0107] The aforementioned grating 301 can be a diffraction grating. The aforementioned switching engine 303 can be a liquid crystal on silicon (LCOS) or a microelectromechanical system (MEMS), etc.

[0108] In one possible implementation, the switching engine 303 is a liquid crystal on silicon. The principle of how the switching engine changes the transmission direction of a single-wavelength optical signal is described below, using a liquid crystal on silicon as an example. For example, see... Figure 4 . Figure 4 A schematic diagram of the physical structure of the aforementioned silicon-based liquid crystal is provided. The silicon-based liquid crystal includes a first panel 401, a second panel 402, a liquid crystal layer 403, a driving circuit 404, and two alignment films 405. The first panel 401 and the second panel 402 are disposed opposite to each other. The first panel 401 is parallel to the second panel 402. The first panel 401 may be a silicon backplane, and the second panel 402 may be a transparent glass substrate. The liquid crystal layer 403 is located between the first panel 401 and the second panel 402, and contains a plurality of liquid crystal particles 4031. The liquid crystal particles 4031 deflect when a voltage is applied by the driving circuit 404. The driving circuit 404 generates an electric field to control the deflection of the liquid crystal in the liquid crystal layer 403. The two alignment films 405 are respectively located on opposite sides of the liquid crystal layer 403. One alignment film 405 is located between the liquid crystal layer 403 and the first panel 401, and the other alignment film 405 is located between the liquid crystal layer 403 and the second panel 402. The alignment film 405 is used to give the liquid crystal particles 4031 in the liquid crystal layer 403 an initial orientation.

[0109] For example, the driving circuit 404 includes a first electrode layer 4041 and a second electrode layer 4042. The first electrode layer 4041 is located between the liquid crystal layer 403 and the first panel 401. The second electrode layer 4042 is located between the liquid crystal layer 403 and the second panel 402. The first electrode layer 4041 is formed on the side of the first panel 401 facing the liquid crystal layer 403, and the second electrode layer 4042 is formed on the side of the second panel 402 facing the liquid crystal layer 403. Two alignment films 405 are located between the first electrode layer 4041 and the second electrode layer 4042. When the first electrode layer 4041 and the second electrode layer 4042 are energized, the deflection of the liquid crystal in the liquid crystal layer 403 can be controlled.

[0110] Specifically, when a voltage is applied to the first electrode layer 4041 and the second electrode layer 4042, creating an electric field between them, the liquid crystal particles 4031 in the liquid crystal layer 403 will deflect. Since liquid crystal is a birefringent material, this deflection results in a change in the equivalent refractive index, thereby altering the transmission direction of the incident light. Furthermore, the angle of deflection of the liquid crystal particles 4031 is related to the magnitude of the voltage applied to the first electrode layer 4041 and the second electrode layer 4042; therefore, different voltages can be applied to achieve deflection of different incident light transmission directions.

[0111] Liquid crystal on silicon (LCD) consists of millions of pixels, which can be arranged in an array, known as a pixel array. Each pixel can be an electronic component, and these components may include the aforementioned... Figure 3 The panel, electrode layer, and liquid crystal layer shown can control the phase of pixels by applying different voltages to the liquid crystal particles in the liquid crystal layer. Light signals incident on the silicon-based liquid crystal are displayed as light spots on the pixel array; different wavelengths of light signals display different areas. A single-wavelength light signal spot can be displayed on multiple pixels in the pixel array, and these multiple pixels can be referred to as the transmission channel for that single-wavelength light signal. For ease of understanding, see the example provided. Figure 5 .

[0112] Figure 5This diagram illustrates the arrangement of incident single-wavelength light signals as pixel arrays on a silicon-based liquid crystal (LCD) matrix. The pixel array includes a wavelength direction and a port direction. In the wavelength direction, different wavelengths of light signals incident on the surface of the LCD spread out at different angles. In the port direction, light signals of a certain wavelength are output at different ports according to different phases (or different diffraction angles). When the light signals strike the surface of the LCD, the light signals of different wavelengths (e.g., λ1, λ2, λ3) are arranged along the wavelength direction of the liquid crystal plane. Specifically, the transmission channel corresponding to the incident light signal with wavelength λ1 occupies the pixels in region S1, the transmission channel corresponding to the incident light signal with wavelength λ2 occupies the pixels in region S2, and the transmission channel corresponding to the incident light signal with wavelength λ3 occupies the pixels in region S3. The wavelengths of the incident light beams λ1, λ2, and λ3 are different from each other. For these three transmission channels, a driving circuit applies a driving voltage to the pixels in these three transmission channels to achieve phase modulation, thereby changing the transmission direction of the corresponding light signals. It should be noted that the light spots of different wavelengths are not completely independently distributed in the pixel array of the silicon liquid crystal. The light spots of different wavelengths can overlap with each other, and the same pixel can contain multiple wavelengths of light spots.

[0113] Based on the above description, it can be seen that the areas displayed by light spots of different wavelengths in the pixel array of a liquid crystal on silicon (LCD) are different. Each wavelength of light signal displays an area comprising multiple pixels (or multiple pixel columns; for example, areas S1, S2, and S3 each comprise five pixel columns). Therefore, it can be said that these multiple pixels (or multiple pixel columns) correspond to the wavelength (or frequency) of the light signal. In practice, at the factory, the pixels (or pixel columns) in the LCD are pre-calibrated with a specific wavelength (or frequency). When a light signal of a specific wavelength (or frequency) is incident on the LCD, it is displayed as a light spot on the multiple pixels (or multiple pixel columns) corresponding to that wavelength (or frequency). Furthermore, these multiple pixels (or multiple pixel columns) constitute the transmission channel for the light signal of that specific wavelength (or frequency). Therefore, it can also be said that this transmission channel corresponds to the light signal of that specific wavelength (or frequency). That is, the transmission channel in the LCD changes the transmission direction of the corresponding light signal of that specific wavelength (or frequency).

[0114] In one possible implementation, the aforementioned switching engine 303 is a microelectromechanical system (MEMS). The MEMS includes a MEMS mirror array. This MEMS mirror array is equivalent to the pixel array in the aforementioned liquid crystal on silicon (LCD). The mirrors in the MEMS mirror array correspond to the wavelength (or frequency) of the optical signal, and this correspondence can be pre-calibrated at the factory. The reflection angle of the optical signal can be changed by adjusting the angle of the corresponding mirror in the MEMS mirror array, thereby reflecting the optical signal of the corresponding wavelength (or frequency) to a specific fiber optic port for output. Similarly, there can be one or more mirrors corresponding to a single wavelength (or frequency), and these one or more mirrors constitute the transmission channel corresponding to the optical signal of that single wavelength (or frequency), meaning that the transmission channel corresponds to the optical signal of that single wavelength (or frequency). For ease of subsequent description, in this application, the mirrors in the MEMS mirror array can also be referred to as pixels; therefore, the MEMS mirror array can also be referred to as a pixel array.

[0115] The aforementioned switching engine 303 can also be other devices used to change the transmission direction of incident light signals, and this application does not limit this.

[0116] The process described above, where the transmission direction of the incident optical signal is changed in the switching engine of the WSS to output it from a specific port, is a filtering process. The wavelength (or frequency) corresponding to the pixel calibrated in the switching engine is the filtering center frequency corresponding to that pixel. Normally, the filtering center frequency corresponding to the pixel calibrated at the factory is accurate. However, as usage time increases, the filtering center frequency corresponding to the pixel in the switching engine of the WSS will gradually deviate (i.e., frequency offset occurs), leading to asymmetrical filtering of the optical signal, resulting in filtering costs, which degrade the quality of the optical signal and reduce the performance of the optical transmission system. For a better understanding of filtering costs, please refer to the example provided. Figure 6 .

[0117] Signal quality can be evaluated using the signal-to-noise ratio (SNR) margin (the SNR required to reach the forward error correction (FEC) threshold). Filtering cost refers to the difference in SNR margin before and after filtering; it represents the degree of signal degradation caused by filtering. Figure 6 The image shows the power spectrum of the signal and the filtered power spectrum. Assuming the signal bandwidth and the filter bandwidth are the same, it can be seen that because the center frequency of the filter is offset from the center frequency of the signal, a portion of the signal is filtered out during filtering, resulting in a missing part in the power spectrum of the filtered signal (see [link to relevant documentation] for the missing part). Figure 6(The area with the diagonal lines at the bottom). Because a portion of the signal is filtered out, signal degradation occurs, resulting in a difference in the signal-to-noise ratio tolerance between the filtered and unfiltered signals, causing a filtering overhead. This filtering overhead leads to the loss of useful signals, reducing the quality of the received signal and limiting its transmission capability.

[0118] In addition to the frequency offset of the filter center frequency in the WSS causing optical signal quality degradation, frequency offset of the transmitted optical signal itself also leads to filtering overhead during the WSS filtering process, affecting signal transmission capability. Therefore, in order to better reduce the filtering overhead in the WSS and improve the optical signal transmission capability, this application provides a reconfigurable optical add-drop multiplexer.

[0119] For example, Figure 7 The diagram shown is a structural schematic of a reconfigurable optical add-drop multiplexer provided in this application. Figure 7 The ROADM 700 shown includes a light source 701, a filter 702, a splitter 703, a wavelength detection device 704, a processing module 705, an ADWSS 706, a WSS 707, a power detection device 708, a WSS 709, a receiver 7010, and a transmitter 7011.

[0120] The functions implemented by WSS 709 can be found in the above description. Figure 2 The functions implemented by WSS 1011 and WSS 707 can be found in the above description. Figure 2 The functions implemented by WSS 1012 and ADWSS 706 can be referenced above. Figure 2 The functions implemented by ADWSS 1013 and the functions implemented by receiver 7010 can be referenced above. Figure 2 The functions implemented by receiver 1014 and transmitter 7011 can be referenced above. Figure 2 The functions implemented by the 1015 transmitter will not be elaborated here.

[0121] The aforementioned light source 701 is used to generate multi-wavelength optical signals. In one possible implementation, the frequency intervals between adjacent optical signals in the multi-wavelength optical signals generated by the light source are equal. For example, the light source 701 may be an optical frequency comb generator, or it may be a laser array, etc.

[0122] The filter 702 described above is used to filter the multi-wavelength optical signal generated by the light source 701 into multiple single-wavelength optical signals. For example, the filter 702 can be an arrayed waveguide grating (AWG) filter, etc.

[0123] The aforementioned optical splitter 703 is used to divide an optical signal into multiple optical signals according to power. An optical splitter can also be called an optical splitter or a power divider.

[0124] The wavelength detection device 704 is used to detect the wavelength of an optical signal. For example, the wavelength detection device 704 may be a high-precision wavelength detection device.

[0125] Processing module 705 can be the computation and control core of ROADM700, serving as the final execution unit for information processing and program execution. Processing module 705 can be a central processing unit, a general-purpose processor, a digital signal processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. Processing module 705 can also be a combination that implements computational functions, such as a combination of one or more microprocessors, a combination of a digital signal processor and a microprocessor, etc.

[0126] The power detection device 708 is used to detect the power of the optical signal. Exemplarily, the power detection device may be a photodiode (PD) or an optical power meter (OPM).

[0127] In one possible implementation, the power detection device in the ROADM provided in this application can be replaced with a coherent detection device, and the power value of the optical signal can also be detected by performing coherent detection on the optical signal.

[0128] In one possible implementation, a portion of the single-wavelength optical signal after the multi-wavelength optical signal generated by the light source 701 is filtered by the filter 702 can be used as the transmitted optical signal of the transmitter 7011 or as the local oscillator optical signal of the receiver 7010. Therefore, the transmitter 7011 or receiver 7010 no longer needs to include a light source, thus saving costs.

[0129] In a specific implementation, the light source 701 generates multi-wavelength light signals, which are then filtered by filter 702 to output multiple single-wavelength light signals.

[0130] One of the multiple single-wavelength optical signals can be input to the optical splitter 703 for power distribution, resulting in two optical signal outputs. For ease of description, the single-wavelength optical signal input to the optical splitter 703 is referred to as the first optical signal, and the wavelength of the first optical signal is referred to as the first wavelength. The first optical signal can be a pre-set optical signal input to the optical splitter 703. In one possible implementation, the first optical signal can be a signal outside the standard communication frequency band. That is, the first optical signal may not carry service data transmission.

[0131] The first optical signal is split into two optical signals by the beam splitter 703. The power of the two optical signals may be the same or different. However, the wavelengths of the two optical signals are the same, which is still the first wavelength. Therefore, the two optical signals can still be called the first optical signal.

[0132] One of the two optical signals is input to the WSS 707 via the ADWSS 706 and can be used to calibrate the frequency offset of the WSS. The specific implementation of this frequency offset calibration will be introduced later and will not be detailed here.

[0133] The other optical signal of the two optical signals is input to the wavelength detection device 704. The wavelength detection device 704 detects the wavelength of the input optical signal and sends the detected wavelength to the processing module 705.

[0134] After obtaining the detected wavelength, the processing module 705 compares the detected wavelength with a preset first reference wavelength. Specifically, it calculates the wavelength difference between the detected wavelength and the first reference wavelength, and then calculates the corresponding frequency difference. The processing module 705 then sends this frequency difference to the light source 701. The light source 701 adjusts the frequency of its generated multi-wavelength optical signal based on this frequency difference to align the frequency of the generated multi-wavelength optical signal with the reference frequency. For example, the first reference wavelength or reference frequency can be a standard-defined wavelength or frequency, such as the wavelength or frequency specified by the International Telecommunication Union (ITU) Telecommunication Standardization.

[0135] For example, when the light source 701 receives the frequency difference sent by the processing module 705, it can first determine whether the frequency difference is within a preset frequency difference range. This preset frequency difference range can be an acceptable frequency deviation range; exceeding this range would lead to significant filtering costs, which is unacceptable. Therefore, if the received frequency difference is within the preset frequency difference range, the light source 701 can continue to generate multi-wavelength optical signals without adjusting its own frequency. If the received frequency difference exceeds the preset frequency difference range, the light source 701 can adjust its own frequency based on the received frequency difference to align the frequency of its generated multi-wavelength optical signals with the standard frequency. For example, the preset frequency range can be set according to actual conditions, and this application does not impose any restrictions on it.

[0136] In one possible implementation, after the light source 701 is aligned with its own frequency, a multi-wavelength optical signal is generated again. Similarly, this multi-wavelength optical signal is filtered by filter 702 to output multiple single-wavelength optical signals. One of these single-wavelength optical signals (referred to as the second optical signal for ease of description) can be input to beam splitter 703 for power distribution, resulting in two optical signal outputs. Likewise, the second optical signal can be a pre-set optical signal input to beam splitter 703. In one possible implementation, the second optical signal can be a signal outside the standard communication frequency band, meaning it may not carry service data transmission.

[0137] The second optical signal is split into two optical signals by the beam splitter 703. The power of the two optical signals may be the same or different. Since the wavelengths of the two optical signals are the same, they can still be referred to as the second optical signals. For ease of description, one of the two optical signals will be called the A-channel second optical signal, and the other will be called the B-channel second optical signal.

[0138] The second optical signal from path A is input to WSS 707 via ADWSS 706. The second optical signal from path B is input to wavelength detection device 704. After being input to wavelength detection device 704, the second optical signal from path B can be used again to align the frequency of the light source. For specific operation, please refer to the corresponding description in the first optical signal section above, which will not be repeated here.

[0139] After the second optical signal from channel A is input to the WSS 707, it can be used to calibrate the frequency offset of the WSS 707. Specifically, the WSS 707 can output the second optical signal sequentially through multiple transmission channels, and the output second optical signal is input to the power detection device 708. The power detection device 708 detects the power values ​​of the second optical signal output from the multiple transmission channels, obtains multiple power values, and sends these multiple power values ​​to the processing module 705. The processing module 705 can detect the frequency offset change value of the WSS 707 based on the multiple power values. Then, the processing module 705 can send the frequency offset change value to the WSS 707, and the WSS 707 can adjust the correspondence between pixels and optical frequencies (or optical wavelengths) in its own switching engine based on the frequency offset change value to calibrate the correspondence between pixels and optical frequencies (or optical wavelengths) in the switching engine, thereby achieving frequency offset calibration of the WSS 707. For ease of understanding, an example is given below.

[0140] For example, assuming the wavelength (or frequency) of the second optical signal is a second wavelength (or a second frequency), and multiple pixels in the WSS707's switching engine correspond to this second frequency, then the transmission channel composed of these multiple pixels is the transmission channel for the second optical signal; that is, the transmission channel corresponds to the second frequency. The transmission of the second frequency optical signal through this channel can be pre-set. With increased usage time, the transmission channel will gradually shift, meaning the correspondence between the transmission channel (or pixels) and the optical frequency will shift, causing the transmission channel to no longer be the ideal transmission channel for its pre-set corresponding optical frequency signal. This results in signal loss during the transmission of the optical signal, i.e., the aforementioned filtering cost. Therefore, to reduce the filtering cost of the optical signal, it is necessary to calibrate the correspondence between pixels and optical frequencies in the WSS's switching engine. Specifically, the transmission channel corresponding to the second frequency can be used as a reference to sequentially open the adjacent or nearby transmission channels to transmit the second optical signal. Then, the power value of the output second optical signal is detected by the power detection device 708, and the ideal transmission channel for transmitting the second optical signal in the current WSS 707 is found based on the maximum power value.

[0141] The above-mentioned opening of the transmission channel is the above-mentioned Figure 5 The method described above applies a driving voltage to the pixels of the transmission channel through a driving circuit to achieve phase modulation of the pixels in the transmission channel, thereby changing the transmission direction of the corresponding optical signal.

[0142] To facilitate understanding of the above-described method of sequentially opening transmission channels adjacent to or near the second frequency to transmit the second optical signal, please refer to the example provided. Figure 8 . Figure 8 An example is shown of a partial pixel array in the swapping engine, assuming this partial pixel array comprises 9 pixel columns. Figure 8 In the middle, assuming Figure 8 The transmission channel 1 shown in (a) is a preset transmission channel in the switching engine of the aforementioned WSS 707 for transmitting the aforementioned second frequency optical signal. This transmission channel 1 includes pixel columns 4, 5, and 6. Referring to this transmission channel 1, transmission channel 2 can be configured (see...). Figure 8 (b) of), transmission channel 3 (see Figure 8 (c) of), transmission channel 4 (see Figure 8 (d) and transmission channel 5 (see Figure 8 (e)). Among them, transmission channel 2 includes pixel columns 5, 6 and 7, which are to the right of transmission channel 1 (facing the viewpoint). Figure 8In the case of the pixel array shown, the left and right (hereinafter the same) are offset by one pixel column. Transmission channel 3 includes pixel columns 6, 7, and 8, which are offset to the right by two pixel columns compared to transmission channel 1. Transmission channel 4 includes pixel columns 3, 4, and 5, which are offset to the left by one pixel column compared to transmission channel 1. Transmission channel 5 includes pixel columns 2, 3, and 4, which are offset to the left by two pixel columns compared to transmission channel 1. That is, taking one pixel column as the step size, the new transmission channel is gradually offset to the left and right of transmission channel 1 to obtain a new transmission channel. However, in the specific implementation, this step size can be two pixel columns, three pixel columns, etc., or it can be an offset with unequal step sizes. This application does not limit this.

[0143] Based on the above description, after the second optical signal of the second frequency is input to the WSS 707 via the ADWSS 706, the WSS 707 can first open transmission channel 1 in the switching engine to transmit the second optical signal. The power value of the second optical signal output through transmission channel 1 is detected by the power detection device 708 to obtain power value 1. Then, transmission channels 2, 3, 4, and 5 are opened sequentially to transmit the second optical signal respectively. The power value of the second optical signal output through each of these transmission channels is measured by the power detection device 708 to obtain power values ​​2, 3, 4, and 5 respectively. It should be noted that the opening order of transmission channels 2, 3, 4, and 5 can be arbitrary, and this application does not impose any restrictions on this.

[0144] The above Figure 8 The transmission channels shown are merely examples and do not constitute a limitation on the embodiments of this application.

[0145] The following describes the process by which the processing module 705 detects the frequency offset change value of the WSS 707 based on the multiple power values ​​measured by the power detection device 708.

[0146] Specifically, the power detection device 708 measures the power values ​​of the second optical signals output through the multiple transmission channels and sends these power values ​​to the processing module 705. In one possible implementation, the processing module 705 compares the multiple power values ​​and finds the largest power value among them. Then, based on the largest power value, it determines the transmission channel corresponding to the largest power value (referred to as the target transmission channel), that is, the power value measured for the second optical signal output through the target transmission channel is the largest power value. As described above, there is a correspondence between pixels and optical frequencies in the switching engine, or in other words, there is a correspondence between transmission channels and optical frequencies in the switching engine. Therefore, based on this correspondence, the preset optical frequency (referred to as the target optical frequency) corresponding to the target transmission channel can be determined. Then, the difference between the second frequency and the target optical frequency is calculated. This difference is the offset value of the optical frequency corresponding to the target transmission channel. Furthermore, this difference can be used as the offset value of the optical frequency corresponding to the pixel in the switching engine of the WSS 707. Then, the processing module 705 can send the offset value to the WSS 707. The WSS 707 adjusts the correspondence between pixels and light frequencies in its own switching engine based on the offset value, thereby realizing the calibration of pixels and light frequencies in the switching engine, that is, realizing the frequency offset calibration in the WSS 707.

[0147] In one possible implementation, if the target optical frequency deviates from the frequency specified by the International Telecommunication Union (ITU) telecommunications standard (referred to as the first standard optical frequency), then the frequency offset (i.e., frequency difference) between the target optical frequency and the first standard optical frequency can be calculated, and this frequency offset is used as the first reference frequency offset. Then, the frequency offset (referred to as the first frequency offset value) between the second frequency and the first standard optical frequency is calculated. Next, the difference between the first frequency offset value and the first reference frequency offset value is calculated; this difference is the frequency offset change value (referred to as the first frequency offset change value) between the first frequency offset value and the first reference frequency offset value. This first frequency offset change value also indicates the offset value of the optical frequency corresponding to the target transmission channel, that is, it indicates the offset value of the optical frequency corresponding to the pixel in the WSS 707's switching engine. Then, similarly, the processing module 705 can send the first frequency offset change value to the WSS 707. The WSS 707 adjusts the correspondence between pixels and light frequencies in its own switching engine based on the first frequency offset change value, thereby realizing the calibration of pixels and light frequencies in the switching engine, that is, realizing the frequency offset calibration in the WSS 707.

[0148] In one possible implementation, since the multiple transmission channels are set according to a certain step size, the size of this step size will affect the final determined ideal transmission channel for transmitting the optical signal of the second frequency. That is, the multiple transmission channels may not include the ideal transmission channel in the switching engine of WSS 707 used to transmit the second optical signal. To find the ideal transmission channel more accurately, the processing module 705 can fit a smooth power curve based on the multiple power values ​​obtained above. The horizontal axis of the power curve represents the transmission channel, and the vertical axis represents the power value. Then, the maximum value in the power curve is found, and the transmission channel corresponding to the maximum value is determined. The transmission channel corresponding to the maximum value is the target transmission channel. Subsequent operations can be found in the above description of the target transmission channel, and will not be repeated here.

[0149] To facilitate understanding of this power curve, assume that the above power values ​​are related to the above... Figure 8 The description includes power values ​​1, 2, 3, 4, and 5. Then, a smooth power curve is obtained by fitting these five power values, as exemplarily shown in [reference needed]. Figure 9 .exist Figure 9 As shown in the power curve, the power values ​​1, 2, 3, 4, and 5 corresponding to transmission channels 1, 2, 3, 4, and 5 are not the maximum power values ​​on the curve. The maximum power value on the curve is 0, and the corresponding transmission channel is the target transmission channel mentioned above.

[0150] In one possible implementation, two optical signals can be used to achieve frequency alignment of the light source 701 and frequency offset calibration in the WSS 707.

[0151] like Figure 10 As shown, the ROADM 700 may also include a beam splitter 7012. Similarly, the light source 701 generates multi-wavelength optical signals, which are filtered by filter 702 to output multiple single-wavelength optical signals.

[0152] One of the multiple single-wavelength optical signals can be input to the optical splitter 7012 for power distribution, resulting in two optical signal outputs. For ease of description, the single-wavelength optical signal input to the optical splitter 7012 is referred to as the third optical signal, and the wavelength of the third optical signal is referred to as the third wavelength. The third optical signal can be a pre-set optical signal input to the optical splitter 7012. In one possible implementation, the third optical signal can be a signal outside the standard communication frequency band. That is, the third optical signal may not carry service data transmission.

[0153] The third optical signal is split into two optical signals by the beam splitter 7012. The power of the two optical signals may be the same or different. Since the wavelengths of the two optical signals are the same, they are still considered the third wavelength, and therefore can still be called third optical signals. One of the two optical signals is input to the wavelength detection device 704. The wavelength detection device 704 detects the wavelength of the input optical signal and sends the detected wavelength to the processing module 705.

[0154] After obtaining the wavelength of the detected third optical signal, the processing module 705 compares the detected wavelength with a preset second reference wavelength. Specifically, it calculates the wavelength difference between the detected wavelength and the second reference wavelength, and then calculates the corresponding frequency difference. Combining the frequency difference corresponding to the first optical signal calculated above, it calculates the average value of the two frequency differences. This average value is used as the frequency offset value of the light source 701. Then, the processing module 705 sends this average value to the light source 701. The light source 701 adjusts the frequency of its generated multi-wavelength optical signal based on this average value to align the frequency of the generated multi-wavelength optical signal with the reference frequency. For example, the second reference wavelength or reference frequency can be a standard-defined wavelength or frequency, such as a wavelength or frequency specified by the International Telecommunication Union (ITU) telecommunications standards.

[0155] Optionally, the average of the two frequency differences can be obtained by directly summing the two frequency differences and taking the average; or it can be obtained by weighted averaging of the two frequency differences.

[0156] Alternatively, after receiving the average value sent by the processing module 705, the light source 701 can first determine whether the average value is within a preset frequency difference range. Then, based on the determination result, the corresponding operation is performed. For details, please refer to the foregoing description, which will not be repeated here.

[0157] The frequency of the light source 701, which is based on two optical signals, can achieve more accurate alignment.

[0158] In one possible implementation, after the light source 701 is aligned with its own frequency, a multi-wavelength optical signal is generated again. Similarly, this multi-wavelength optical signal is filtered by filter 702 to output multiple single-wavelength optical signals. One of these single-wavelength optical signals (referred to as the fourth optical signal for ease of description) can be input to beam splitter 7012 for power distribution, resulting in two optical signal outputs. Likewise, the fourth optical signal can be a pre-set optical signal input to beam splitter 7012. In one possible implementation, the fourth optical signal can be a signal outside the standard communication frequency band, meaning it may not carry service data transmission.

[0159] The fourth optical signal is split into two optical signals by the beam splitter 7012. The power of the two optical signals may be the same or different. Since the wavelengths of the two optical signals are the same, they can still be referred to as the fourth optical signal. For ease of description, one of the two optical signals will be called the fourth optical signal A, and the other will be called the fourth optical signal B.

[0160] The fourth optical signal from channel A is input to WSS 707 via ADWSS 706. The fourth optical signal from channel B is input to wavelength detection device 704. After being input to wavelength detection device 704, the fourth optical signal from channel B can be used again to align the frequency of the light source. For specific operation, please refer to the corresponding description in the third optical signal section above, which will not be repeated here.

[0161] The fourth optical signal of channel A can be coupled with the second optical signal of channel A to the coupler 7013, and then input together through ADWSS 706 to WSS 707.

[0162] After the fourth optical signal from channel A is input to the WSS 707, it can be used to calibrate the frequency offset of the WSS 707. Specifically, the processing module 705 calculates another frequency offset change value of the optical frequency corresponding to the pixel in the switching engine of the WSS 707 based on the power value of the fourth optical signal and the second reference frequency offset value. The second reference frequency offset value is the pre-measured frequency offset value of the optical frequency corresponding to the transmission channel transmitting the fourth optical signal in the WSS 707 relative to the second standard optical frequency; for example, the second standard optical frequency can be the frequency specified by the International Telecommunication Union telecommunications standard. The specific calculation process of this other frequency offset change value can be referred to the corresponding description of the second optical signal above, and will not be repeated here.

[0163] The processing module 705 combines the two frequency offset change values ​​of the corresponding optical frequencies of pixels in the switching engine of WSS 707, calculated based on the fourth and second optical signals, and calculates the average of these two frequency offset change values. This average value is used as the offset value of the optical frequency corresponding to the pixel in the switching engine of WSS 707. Then, the processing module 705 sends this average value to WSS 707. WSS 707 can adjust the correspondence between pixels and optical frequencies (or wavelengths) in its own switching engine based on this average value to calibrate the correspondence between pixels and optical frequencies (or wavelengths) in the switching engine, thereby achieving frequency offset calibration of WSS 707.

[0164] Alternatively, in another possible implementation, the processing module 705 can determine the maximum power value based on the power value of the fourth optical signal, and determine the target transmission channel in the switching engine for transmitting the fourth optical signal based on the maximum power value. Then, based on the correspondence between the transmission channels and optical frequencies in the switching engine, the target optical frequency corresponding to the target transmission channel is determined. The frequency difference is calculated based on the target optical frequency and the optical frequency of the fourth optical signal. The WSS 707 can calibrate its own frequency offset based on this frequency difference. For a detailed implementation, please refer to the aforementioned description of the corresponding second optical signal; it will not be repeated here.

[0165] The above method of calibrating the frequency offset of WSS 707 based on two optical signals can achieve more accurate calibration.

[0166] In one possible implementation, this application can also calibrate the frequency offset of the WSS 709 in the ROADM 700. For example, see... Figure 11 As can be seen, the ROADM 700 also includes a power detection device 7014, which is used to detect the power of the optical signal output from the WSS 709 in order to achieve frequency offset calibration of the WSS 709.

[0167] In its specific implementation, the WSS 709 can receive an optical signal (which can be simply referred to as the fifth optical signal). Optionally, this fifth optical signal can be an optical signal from the previous ROADM of the ROADM 700. This fifth optical signal can be an optical signal sent to the ROADM 700 after frequency calibration in the previous ROADM.

[0168] The fifth optical signal, after passing through WSS 709, is input to power detection device 7014 via ADWSS 706. Power detection device 7014 detects the power value of the fifth optical signal from WSS 709. Then, processing module 705 calculates the frequency offset change value of WSS 709 based on the power value measured by power detection device 7014. WSS 709 can calibrate its own frequency offset based on this frequency offset change value.

[0169] Similarly, specifically, the WSS 709 can sequentially output the fifth optical signal through multiple transmission channels, and the output fifth optical signal is input to the power detection device 7014. The power detection device 7014 detects the power values ​​of the fifth optical signal output from the multiple transmission channels, obtains multiple power values, and sends these multiple power values ​​to the processing module 705. The processing module 705 can detect the frequency offset change value of the WSS 709 based on the multiple power values. Then, the processing module 705 can send the frequency offset change value to the WSS 709, and the WSS 709 can adjust the correspondence between pixels and optical frequencies (or optical wavelengths) in its own switching engine based on the frequency offset change value to calibrate the correspondence between pixels and optical frequencies (or optical wavelengths) in the switching engine, thereby achieving frequency offset calibration of the WSS 709. The specific implementation process of the frequency offset calibration of the WSS 709 can refer to the specific implementation process of the frequency offset calibration of the WSS 707 described above, and will not be repeated here.

[0170] In one possible implementation, two optical signals can be used to achieve the frequency offset calibration in the WSS 709 described above. Specifically, the WSS 709 can also receive a sixth optical signal. The specific source of this sixth optical signal can be referred to the specific source of the fifth optical signal described above, and will not be repeated here. Then, the sixth optical signal is input to the power detection device 7014 after passing through the WSS 709 via the ADWSS 706. The power detection device 7014 detects the power value of the sixth optical signal from the WSS 709, and then the processing module 705 calculates the frequency offset change value of the WSS 709 based on the power value measured by the power detection device 7014. The processing module 705 combines the frequency offset change value of the WSS 709 obtained based on the fifth optical signal and the frequency offset change value of the WSS 709 obtained based on the sixth optical signal to calculate the final frequency offset change value of the WSS 709. The final frequency offset change value is then sent to the WSS 709 for frequency offset calibration. The specific implementation process of calibrating the frequency offset of WSS 709 based on two optical signals can be referred to the specific implementation process of calibrating the frequency offset of WSS 707 based on two optical signals mentioned above, and will not be repeated here.

[0171] One possible implementation can be exemplarily seen in [reference needed]. Figure 12The power detection device 7014 in the aforementioned ROADM 700 can be replaced with a coherent detection device 7014. The local oscillator signal of the coherent detection device 7014 can be the aforementioned second optical signal and / or fourth optical signal. Specifically, the second optical signal and / or fourth optical signal are input to the coupler 7013 after passing through the beam splitter 703 and / or beam splitter 7012. The coupler 7013 couples the second optical signal and / or fourth optical signal and splits it into two optical signal outputs, one of which is sent to the AWDSS 706, and the other is sent to the coherent detection device 7014 as its local oscillator signal.

[0172] After the fifth and / or sixth optical signals from WSS 709 are input into the coherent detection device 7014 via ADWSS 706, the fifth and / or sixth optical signals are coherently correlated with the second and / or fourth optical signals to detect their power values. The subsequent operations after obtaining the power values ​​can be referred to the foregoing description and will not be repeated here.

[0173] For example, cohering the fifth optical signal and / or the sixth optical signal with the second optical signal and / or the fourth optical signal includes: the fifth optical signal cohering with the second optical signal, or the sixth optical signal cohering with the fourth optical signal. Alternatively, cohering the fifth optical signal and / or the sixth optical signal with the second optical signal and / or the fourth optical signal includes: the fifth optical signal cohering with the fourth optical signal, or the sixth optical signal cohering with the second optical signal.

[0174] In one possible implementation, after the frequency-calibrated second and / or fourth optical signals are output from the WSS707, in addition to being input to the power detection device 708 for power detection, they can also be output to the ROADM700 via a separate path. The second and / or fourth optical signals output from the ROADM700 will be sent to the next-hop ROADM of the ROADM700 for frequency offset calibration of the WSS in the next-hop ROADM and / or frequency alignment of the light source in the next-hop ROADM.

[0175] See Figure 13 , Figure 13 An exemplary structural diagram of the ROADM 1300 is shown. Figure 13The ROADM 1300 shown includes a light source 1301, a filter 1302, a coupler 1303, a coherent detection device 1304, a processing module 1305, an ADWSS 1306, a WSS 1307, a power detection device 1308, a WSS 1309, a receiver 13010, and a transmitter 13011. For example, the functions of these components in the ROADM 1300 and their specific forms in implementation can be found in the descriptions of the corresponding components in the ROADM 700 described above, and will not be repeated here.

[0176] For example, let's take ROADM 1300 as the next-hop ROADM of ROADM 700. First, let's introduce the process by which ROADM 1300 aligns the frequency of the second optical signal with the frequency of the light source 1301 after receiving the second optical signal.

[0177] Specifically, the second optical signal is first received by WSS 1309. WSS 1309 then inputs the received second optical signal to ADWSS 1306, which forwards the second optical signal to coherent detection device 1304.

[0178] Additionally, light source 1301 generates a multi-wavelength optical signal (referred to as the third multi-wavelength optical signal). This third multi-wavelength optical signal is filtered by filter 1302, outputting multiple single-wavelength optical signals. One of these single-wavelength optical signals can be input to coupler 1303 for power distribution, resulting in two optical signal outputs. For ease of description, this single-wavelength optical signal input to coupler 1303 is referred to as the seventh optical signal. This seventh optical signal can be a pre-set optical signal input to coupler 1303. Theoretically, this seventh optical signal has the same frequency (or wavelength) as the aforementioned second optical signal; however, over time, the seventh optical signal generated by light source 1301 will gradually exhibit frequency deviation, thus requiring frequency alignment of light source 1301.

[0179] In one possible implementation, the seventh optical signal can be a signal outside the standard communication frequency band. That is, the seventh optical signal may not carry service data transmission. After passing through coupler 1303, the seventh optical signal is split into two optical signals, and the power of the two optical signals may be the same or different. Since the wavelengths of the two optical signals are the same, they can still be called the seventh optical signal. One of the two seventh optical signals is input to the coherent detection device 1304.

[0180] After receiving the seventh optical signal and the second optical signal, the coherent detection device 1304 performs coherent detection on the seventh optical signal and the second optical signal to obtain a coherently detected signal. The coherent detection device 1304 then sends the coherently detected signal to the processing module 1305.

[0181] The processing module 1305 determines the frequency difference between the seventh optical signal and the second optical signal based on the coherently detected signal. Specifically, the center frequency of the coherently detected signal is the frequency difference. Then, the processing module 1305 sends the frequency difference to the light source 1301. The light source 1301 adjusts the frequency of its generated multi-wavelength optical signal based on the frequency difference to align the frequency of the generated multi-wavelength optical signal with a reference frequency. For example, the reference frequency is the reference frequency for frequency alignment of the light source 701 of the ROAD M 700. Specifically, since the second optical signal is aligned with the reference frequency in the ROADM 700, the frequency alignment of the light source 1301 is achieved using the second optical signal as a reference. By using the optical signal calibrated by the previous ROADM to align its own light source, the light source frequencies of the two ROADMs can be aligned. If each ROADM in the entire optical communication system uses the optical signal calibrated by the previous ROADM to align with its own light source, then the light source alignment of the ROADMs in the entire optical communication system can be achieved, reducing the frequency offset of the optical signal and improving the transmission performance of the optical communication system.

[0182] For example, when the light source 1301 receives the frequency difference sent by the processing module 1305, it can first determine whether the frequency difference is within a preset frequency difference range. This preset frequency difference range can be an acceptable frequency deviation range; exceeding this range would lead to significant filtering costs, which is unacceptable. Therefore, if the received frequency difference is within the preset frequency difference range, the light source 1301 can continue to generate multi-wavelength optical signals without adjusting its own frequency. If the received frequency difference exceeds the preset frequency difference range, the light source 1301 can adjust its own frequency based on the received frequency difference to align the frequency of its generated multi-wavelength optical signals with the standard frequency. For example, the preset frequency range can be set according to actual conditions, and this application does not impose any restrictions on it.

[0183] In one possible implementation, the coherent detection device 1304 in the ROADM 1300 can be replaced with a power detection device 1304. Then, the seventh optical signal and the second optical signal can be input into the power detection device 1304 to obtain two optical power values ​​and their corresponding optical frequencies. The processing module 1305 then calculates the frequency difference between the optical frequencies corresponding to the two optical power values ​​and sends this frequency difference to the light source 1301. The light source 1301 can then align the frequency of its generated multi-wavelength optical signal based on this frequency difference.

[0184] In one possible implementation, after the light source 1301 is aligned with its own frequency, a multi-wavelength optical signal is generated again. Similarly, this multi-wavelength optical signal is filtered by filter 1302 to output multiple single-wavelength optical signals. One of these single-wavelength optical signals (referred to as the eighth optical signal for ease of description) can be input to coupler 1303 for power distribution, resulting in two optical signal outputs. Likewise, the eighth optical signal can be a pre-set optical signal input to coupler 1303. In one possible implementation, the eighth optical signal can be a signal outside the standard communication frequency band, meaning it may not carry service data transmission.

[0185] The eighth optical signal is split into two optical signals after passing through coupler 1303. The power of these two optical signals may be the same or different. Since the wavelengths of the two optical signals are the same, they can still be referred to as the eighth optical signal. For ease of description in the following text, one of the two optical signals will be called the A-channel eighth optical signal, and the other will be called the B-channel eighth optical signal.

[0186] The eighth optical signal from channel A is input to WSS 1307 via ADWSS 1306. The eighth optical signal from channel B is input to the coherent detection device 1304. After being input to the coherent detection device 1304, the eighth optical signal from channel B can be used again to align the frequency of the light source. For specific operations, please refer to the corresponding description in the seventh optical signal section above, which will not be repeated here.

[0187] After the eighth optical signal from channel A is input to WSS 1307, it can be used to calibrate the frequency offset of WSS 1307. Specifically, WSS 1307 can sequentially output the eighth optical signal through multiple transmission channels, and the output eighth optical signal is input to power detection device 1308. Power detection device 1308 detects the power values ​​of the eighth optical signal output from the multiple transmission channels, obtains multiple power values, and sends the multiple power values ​​to processing module 1305. Processing module 1305 can detect the frequency offset value (or frequency offset change value) of WSS 1307 based on the multiple power values. Then, the processing module 1305 can send the frequency offset value (or frequency offset change value) to the WSS 1307. The WSS 1307 can adjust the correspondence between pixels and light frequencies (or light wavelengths) in its own switching engine based on the frequency offset value (or frequency offset change value) to calibrate the correspondence between pixels and light frequencies (or light wavelengths) in the switching engine, thereby achieving frequency offset calibration of the WSS 1307. The specific implementation process of the frequency offset calibration of the WSS 1307 can be referred to the implementation process of calibrating the frequency offset of the WSS 707 based on the second optical signal in the ROADM 700 mentioned above, and will not be repeated here.

[0188] In one possible implementation, two optical signals can be used to achieve frequency alignment of the light source 1301. Specifically, taking ROADM 1300 as the next-hop ROADM of ROADM 700 as an example, ROADM 1300 can receive the second optical signal and the fourth optical signal from ROADM 700.

[0189] After the fourth optical signal is received by WSS 1309, WSS 1309 inputs the received fourth optical signal to ADWSS 1306, which then forwards the fourth optical signal to coherent detection device 1304.

[0190] In addition, the third multi-wavelength optical signal generated by the light source 1301 is filtered by the filter 1302 and then output as multiple single-wavelength optical signals. Among these multiple single-wavelength optical signals, besides the seventh optical signal mentioned above, another optical signal (referred to as the ninth optical signal) can also be input into the coupler 1303, such as... Figure 14 As shown. Theoretically, the ninth optical signal has the same frequency (or wavelength) as the fourth optical signal mentioned above. However, over time, the ninth optical signal generated by the light source 1301 will gradually show a frequency deviation, so it is necessary to align the frequency of the light source 1301.

[0191] The ninth optical signal and the aforementioned seventh optical signal are coupled in coupler 1303 and then split into two optical signal outputs. Each of the two optical signal outputs includes both the seventh and ninth optical signals. The power of the two optical signals may be the same or different. One of the two optical signals is input to WSS 1307 via ADWSS 1306; the other is input to coherent detection device 1304.

[0192] For one optical signal input to the coherent detection device 1304, the seventh optical signal in this optical signal is coherently ...

[0193] For example, when the light source 1301 receives the average value sent by the processing module 1305, it can first determine whether the average value is within a preset frequency difference range. Then, the light source 1301 decides whether to adjust its own frequency based on the determination result. Specific implementation details can be found in the preceding description and will not be repeated here.

[0194] In one possible implementation, two optical signals can be used to achieve frequency alignment of the WSS 1307. Specifically, after the light source 1301 aligns with its own frequency, the multi-wavelength optical signal generated is filtered by filter 1302. Among the multiple single-wavelength optical signals output, in addition to the eighth optical signal, another single-wavelength optical signal (referred to as the tenth optical signal for ease of description) can be input into coupler 1303 along with the eighth optical signal. Similarly, the tenth optical signal can be a pre-set optical signal input to coupler 1303. In one possible implementation, the tenth optical signal can be a signal outside the standard communication frequency band. That is, the tenth optical signal may not carry service data transmission.

[0195] The tenth optical signal and the aforementioned eighth optical signal are coupled in coupler 1303 and then split into two optical signal outputs. Each of these two optical signals includes both the eighth and tenth optical signals. The power of the two optical signals may be the same or different. For ease of subsequent description, these two optical signals will be referred to as the A-channel combined optical signal and the B-channel combined optical signal, respectively.

[0196] The aforementioned A-channel combined optical signal is input to WSS 1307 via ADWSS 1306. The aforementioned B-channel combined optical signal is input to coherent detection device 1304 for further alignment of light source 1301. The specific alignment process is described above in the description of using two optical signals to achieve frequency alignment of light source 1301, and will not be repeated here.

[0197] For the A-channel multiplexed optical signal input to the WSS 1307, a frequency offset value (or frequency offset change value) of the WSS 1307 is detected based on the eighth optical signal in the A-channel multiplexed optical signal, and another frequency offset value (or frequency offset change value) of the WSS 1307 is detected based on the tenth optical signal in the A-channel multiplexed optical signal, thereby obtaining two frequency offset values ​​(or two frequency offset change values) of the WSS 1307. The specific implementation process of obtaining the frequency offset value (or frequency offset change value) can refer to the implementation process of obtaining the frequency offset value (or frequency offset change value) of the WSS 707 based on the second optical signal in the ROADM 700 mentioned above, and will not be repeated here.

[0198] Then, the processing module 1305 calculates the average of the two frequency offset values ​​(or two frequency offset changes) of the WSS 1307. This average value is used as the offset value of the optical frequency corresponding to the pixel in the switching engine of the WSS 1307. The processing module 1305 then sends this average value to the WSS 1307, which can adjust the correspondence between pixels and optical frequencies (or optical wavelengths) in its own switching engine based on this average value to calibrate the correspondence between pixels and optical frequencies (or optical wavelengths) in the switching engine, thereby achieving frequency offset calibration of the WSS 1307.

[0199] The above method of calibrating the frequency offset of WSS 1307 based on two optical signals can achieve more accurate calibration.

[0200] In one possible implementation, after the frequency-calibrated eighth and / or tenth optical signals are output from WSS1307, in addition to being input to the power detection device 1308 for power detection, they can also be output to ROADM1300 via a separate output. The eighth and / or tenth optical signals output from ROADM1300 will be sent to the next-hop ROADM of ROADM1300 for frequency offset calibration of the WSS in the next-hop ROADM and / or frequency alignment of the light source in the next-hop ROADM. The structure of the next-hop ROADM of ROADM1300 can refer to the structure of ROADM1300, and the frequency offset calibration of the WSS and / or frequency alignment of the light source in the next-hop ROADM of ROADM1300 can refer to the specific implementation of frequency offset calibration of the WSS and / or frequency alignment of the light source in ROADM1300, which will not be elaborated here.

[0201] In one possible implementation, this application can also calibrate the frequency offset of WSS 1309 in ROADM 1300. For example, taking ROADM 1300 as the next-hop ROADM of ROADM 700, the following describes the process of calibrating the frequency offset of WSS 1309 based on the second optical signal received by ROADM 1300.

[0202] In its specific implementation, WSS 1309 receives a second optical signal from the aforementioned ROADM 700. This second optical signal, after passing through WSS 1309, is input to the coherent detection device 1304 via ADWSS 1306. The coherent detection device 1304 detects the power value of the second optical signal from WSS 1309. Then, the processing module 1305 calculates the frequency offset change value of WSS 1309 based on the power value measured by the coherent detection device 1304. WSS 1309 can then calibrate its own frequency offset based on this frequency offset change value.

[0203] Similarly, specifically, the WSS 1309 can sequentially output the second optical signal through multiple transmission channels, and the output second optical signal is input to the coherent detection device 1304. The coherent detection device 1304 detects the power values ​​of the second optical signal output from the multiple transmission channels, obtains multiple power values, and sends these multiple power values ​​to the processing module 1305. The processing module 1305 can detect the frequency offset change value of the WSS 1309 based on the multiple power values. Then, the processing module 1305 can send the frequency offset change value to the WSS 1309, and the WSS 1309 can adjust the correspondence between pixels and optical frequencies (or optical wavelengths) in its own switching engine based on the frequency offset change value to calibrate the correspondence between pixels and optical frequencies (or optical wavelengths) in the switching engine, thereby achieving frequency offset calibration of the WSS 1309. The specific implementation process of the frequency offset calibration of the WSS 1309 can refer to the specific implementation process of the frequency offset calibration of the WSS 1307 described above, and will not be repeated here.

[0204] In one possible implementation, two optical signals can be used to achieve the frequency offset calibration in the WSS 1309. Specifically, the WSS 1309 can also receive a fourth optical signal from the ROADM 700. This fourth optical signal, after passing through the WSS 1309, is then input to the coherent detection device 1304 via the ADWSS 1306. The coherent detection device 1304 detects the power value of the fourth optical signal from the WSS 1309. Then, the processing module 1305 calculates the frequency offset change value of the WSS 1309 based on the power value measured by the coherent detection device 1304. The processing module 1305 combines the frequency offset change value of the WSS 1309 obtained based on the second optical signal and the frequency offset change value of the WSS 1309 obtained based on the fourth optical signal to calculate the final frequency offset change value of the WSS 1309. This final frequency offset change value is then sent to the WSS 1309 for frequency offset calibration. The specific implementation process of calibrating the frequency offset of WSS 1309 based on two optical signals can be referred to the specific implementation process of calibrating the frequency offset of WSS 707 based on two optical signals mentioned above, and will not be repeated here.

[0205] In one possible implementation, the local oscillator signal of the coherent detection device 1304 can be the aforementioned eighth optical signal and / or tenth optical signal. Specifically, the eighth optical signal and / or tenth optical signal are input to the coupler 1303. The coupler 1303 couples the eighth optical signal and / or tenth optical signal and splits it into two optical signal outputs, one of which is sent to the ADWSS 1306, and the other is sent to the coherent detection device 1304 as the local oscillator signal of the coherent detection device 1304.

[0206] After the second and / or fourth optical signals from WSS 1309 are input into the coherent detection device 1304 via ADWSS 1306, the second and / or fourth optical signals are coherently correlated with the eighth and / or tenth optical signals to detect the power values ​​of the second and / or fourth optical signals. The subsequent operations after obtaining the power values ​​can be referred to the foregoing description and will not be repeated here.

[0207] For example, cohering the second optical signal and / or the fourth optical signal with the eighth optical signal and / or the tenth optical signal includes: the second optical signal cohering with the eighth optical signal, or the fourth optical signal cohering with the tenth optical signal. Alternatively, cohering the second optical signal and / or the fourth optical signal with the eighth optical signal and / or the tenth optical signal includes: the second optical signal cohering with the tenth optical signal, or the fourth optical signal cohering with the eighth optical signal.

[0208] In one possible implementation, the coherent detection device 1304 in the ROADM 1300 described above can be replaced with a power detection device 1304. Then, the power value of the second optical signal and / or the fourth optical signal output from the WSS 1309 can be detected using this power detection device 1304.

[0209] In one possible implementation, as described above, the ROADM provided in this application includes a light source (e.g., light source 701 or light source 1301 as described above). If a single light source cannot generate an optical signal covering a wide range of wavelengths, multiple light sources can be used. The wavelengths of the optical signals generated by these multiple light sources may not overlap or may partially overlap. For example, if the used optical wavelength range is 1510nm-1530nm, and if the wavelength range of the multi-wavelength optical signal generated by one light source is between 1510nm and 1520nm, then another light source can be added that generates a multi-wavelength optical signal with a wavelength range between 1520nm and 1530nm. This is merely an example; in a specific implementation, multiple light sources can be added to generate an optical signal with a wider range of wavelengths.

[0210] In the aforementioned ROADM, a light source is added. To reduce the frequency offset of the generated optical signal, the added light source can be frequency-aligned. Based on the foregoing description, frequency alignment of one light source in the ROADM can be achieved. For ease of description, the frequency-aligned light source is referred to as the first light source, and the light source added to expand the wavelength range of the generated optical signal is referred to as the second light source. One or more of these second light sources can be added to the ROADM. Since the first light source has already achieved frequency alignment, the frequency of the second light source can be aligned using the optical signal generated by the frequency-calibrated first light source.

[0211] In one possible implementation, a single-wavelength optical signal (referred to as optical signal A) from the multi-wavelength optical signals generated by the first light source after frequency calibration is selected. Additionally, a single-wavelength optical signal (referred to as optical signal B) from the multi-wavelength optical signals generated by the second light source is selected. Optical signals A and B are input into a coherent detection device for coherent detection to obtain the coherently detected signal. Then, the processing module in the ROADM determines the frequency difference between optical signals A and B based on the signal obtained from the coherent detection. The processing module then calculates the difference between this frequency difference and a preset frequency difference to obtain the change in the frequency difference between optical signals A and B. This preset frequency difference can be the frequency difference between optical signals A and B measured when there is no frequency offset (e.g., when the ROADM is manufactured).

[0212] The aforementioned processing module sends the calculated frequency difference change value to the second light source. The second light source can then align the frequency of its generated multi-wavelength optical signal based on this frequency difference change value. For a detailed explanation of how this alignment of the light source frequency is based on the signal output from the coherent detection device, please refer to the specific implementation of light source frequency alignment in the ROADM 1300, which will not be elaborated upon here.

[0213] For ease of understanding, please refer to the example provided. Figure 15 . Figure 15 The ROADM 1300 shown also includes a light source 13012 and a coherent detection device 13013. The light source 13012 is the second light source mentioned above. Figure 15 Based on coherent detection devices (such as Figure 15 The coherent detection device 13013 shown above realizes the above-mentioned second light source (such as...). Figure 15 The frequency alignment of the light source 13012 shown is used as an example for illustration. Figure 15 Taking one of the second light sources as an example, the frequency alignment of multiple second light sources is similar, and will not be elaborated in this application.

[0214] In specific implementation, frequency alignment of the light source 1301 is achieved based on the foregoing description. After frequency alignment, the light source 1301 generates multi-wavelength optical signals, which are filtered by filter 1302 to obtain multiple single-wavelength optical signals. One of these single-wavelength optical signals (e.g., signal A mentioned above) is input to the coherent detection device 13013. Additionally, the light source 13012 generates multi-wavelength optical signals, which are filtered by filter 1302 to obtain multiple single-wavelength optical signals. One of these single-wavelength optical signals (e.g., signal B mentioned above) is input to the coherent detection device 13013. The coherent detection device 13013 performs coherent detection on the two input single-wavelength optical signals to obtain a coherently detected signal. Then, the processing module 1305 determines the frequency difference between the two single-wavelength optical signals based on the signal obtained from the coherent detection. The processing module then calculates the difference between this frequency difference and a preset frequency difference to obtain the frequency difference change value between the two single-wavelength optical signals. This frequency difference change value is then sent to the light source 13012. The light source 13012 can align itself with the frequency of the multi-wavelength light signal it generates based on the frequency difference change value.

[0215] The above Figure 15 Taking ROADM 1300 as an example, the frequency alignment of the light source increased in the ROADM 700 provided in this application to expand the wavelength range of the generated optical signal can be referred to the above. Figure 15 The relevant descriptions will not be repeated here.

[0216] This application also provides an optical communication system, which includes any of the ROADM 700 and any of the ROADM 1300 described in the above embodiments.

[0217] In summary, in this application, the optical signal sent to ROADM 1300 after frequency calibration in ROADM 700 can be used not only for light source alignment in ROADM 1300, but also for frequency offset calibration of the WSS used for input optical signals in ROADM 1300. Similarly, since this optical signal is a frequency-calibrated optical signal, using the calibrated optical signal to calibrate the frequency offset of the WSS can achieve more accurate calibration. Furthermore, for the entire optical communication system, if each ROADM uses the frequency-calibrated optical signal from the previous ROADM to calibrate its own WSS used for input optical signals, then the calibration standard of the WSS used for input optical signals in each ROADM of the optical communication system is basically consistent. This results in a smaller error between the filtering frequencies of the WSS used for input optical signals in the ROADMs of the entire optical communication system, which can greatly reduce the filtering cost of optical signals propagating in the optical communication system, thereby improving the transmission performance of the entire optical communication system.

[0218] Furthermore, in this application, compared to existing ROADMs, the light source of the ROADM (e.g., ROADM 1300) provided in this application can be aligned using the optical signal calibrated in the previous ROADM (e.g., ROADM 700), and the optical signal generated by the aligned light source is used to calibrate the frequency offset of the WSS in the ROADM provided in this application. Since the light source is already aligned, the generated optical signal is the aligned optical signal, and using the aligned optical signal to calibrate the frequency offset of the WSS can achieve more accurate calibration. In addition, for the entire optical communication system, if each ROADM uses the optical signal calibrated by the previous ROADM to align its own light source, and uses the optical signal generated by its own aligned light source to calibrate its own WSS, then the calibration standard of the WSS in each ROADM in the optical communication system is basically consistent, thereby achieving a smaller error between the filtering frequencies of the WSS in the ROADMs of the entire optical communication system. This can greatly reduce the filtering cost of the optical signal during the propagation process of the optical communication system, and thus improve the transmission performance of the entire optical communication system.

[0219] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A reconfigurable optical add-drop multiplexer (ROADM), comprising: The ROADM is the first ROADM, including: Light source: used to generate the first multi-wavelength light signal; Filter: Used to filter the first multi-wavelength optical signal and output multiple single-wavelength optical signals; the multiple single-wavelength optical signals include the first optical signal; Coherent detection device: used to perform coherent detection on the first optical signal and the second optical signal; the second optical signal is a reference signal of the first optical signal, and the second optical signal is an optical signal sent to the first ROADM after frequency calibration in the second ROADM; Processing module: Determines the frequency difference between the first optical signal and the second optical signal based on the signal obtained from the coherent detection device; The light source is also used to generate a frequency of a multi-wavelength optical signal based on the frequency difference alignment, and to generate a second multi-wavelength optical signal after the frequency of the multi-wavelength optical signal generated by alignment. The second multi-wavelength optical signal is passed through the filter to output a single-wavelength third optical signal. The third optical signal is used to calibrate the frequency offset of the first wavelength selection switch WSS in the first ROADM.

2. The first ROADM of claim 1, wherein, The first ROADM also includes a power detection device; the first WSS is the WSS used for outputting optical signals in the first ROADM; The first WSS is used to receive the third optical signal and output the third optical signal to the power detection device; The power detection device is used to detect the power value of the third optical signal output from the first WSS; The processing module is further configured to detect a first target frequency offset change value of the first WSS based on the power value of the third optical signal, wherein the first target frequency offset change value indicates the offset of the optical frequency corresponding to the pixel of the switching engine in the first WSS.

3. The first ROADM of claim 2, wherein, The second multi-wavelength optical signal, after passing through the filter, outputs a single-wavelength optical signal, which also includes a fourth optical signal; The first WSS is also used to receive the fourth optical signal and output the fourth optical signal to the power detection device; The power detection device is also used to detect the power value of the fourth optical signal output from the first WSS; The processing module is further configured to detect the first target frequency offset change value of the first WSS based on the power value of the third optical signal, including: detecting the first target frequency offset change value based on the power value of the third optical signal and the power value of the fourth optical signal.

4. The first ROADM according to claim 3, characterized in that, The processing module is specifically used for: The first frequency offset change value of the first WSS is calculated based on the power value of the third optical signal and the first reference frequency offset value. The first reference frequency offset value is the frequency offset value of the optical frequency corresponding to the channel transmitting the third optical signal in the first WSS relative to the first standard optical frequency, which is measured in advance. The second frequency offset change value of the first WSS is calculated based on the power value of the fourth optical signal and the second reference frequency offset value. The second reference frequency offset value is the frequency offset value of the optical frequency corresponding to the channel transmitting the fourth optical signal in the first WSS relative to the second standard optical frequency, which is measured in advance. The first target frequency offset change value is obtained by averaging the first frequency offset change value and the second frequency offset change value.

5. The first ROADM according to any one of claims 1-4, characterized in that, The first ROADM also includes a second wavelength selection switch (WSS); the second WSS is the WSS used for input optical signals in the first ROADM. The second WSS is used to receive the second optical signal and output the second optical signal to the coherent detection device; The coherent detection device is also used to detect the power value of the second optical signal output from the second WSS; The processing module is further configured to detect a second target frequency offset change value of the second WSS based on the power value of the second optical signal, wherein the second target frequency offset change value indicates the offset of the optical frequency corresponding to the pixel of the switching engine in the second WSS.

6. The first ROADM according to claim 5, characterized in that, The second WSS is also used to receive a fifth optical signal from the second ROADM and output the fifth optical signal to the coherent detection device; the fifth optical signal is an optical signal sent to the first ROADM after frequency calibration in the second ROADM. The coherent detection device is also used to detect the power value of the fifth optical signal output from the second WSS; The processing module is further configured to detect the second target frequency offset change value of the second WSS based on the power value of the second optical signal, including: detecting the second target frequency offset change value based on the power value of the second optical signal and the power value of the fifth optical signal.

7. The first ROADM according to claim 6, characterized in that, The processing module is specifically used for: The third frequency offset change value of the second WSS is calculated based on the power value of the second optical signal and the third reference frequency offset value. The third reference frequency offset value is the frequency offset value of the optical frequency corresponding to the channel transmitting the second optical signal in the second WSS relative to the third standard optical frequency, which is measured in advance. The fourth frequency offset change value of the second WSS is calculated based on the power value of the fifth optical signal and the fourth reference frequency offset value. The fourth reference frequency offset value is the frequency offset value of the optical frequency corresponding to the channel transmitting the fifth optical signal in the second WSS relative to the fourth standard optical frequency, which is measured in advance. The second target frequency offset change value is obtained by averaging the third frequency offset change value and the fourth frequency offset change value.

8. The first ROADM according to any one of claims 1-4, characterized in that, The first WSS is also used to send the third optical signal to the third ROADM, the third optical signal being used to calibrate the frequency offset of the WSS in the third ROADM and to calibrate the output frequency of the light source in the third ROADM.

9. The first ROADM according to any one of claims 1-4, characterized in that, The first ROADM includes a light source that is an optical frequency comb generator.

10. A reconfigurable optical add-drop multiplexer (ROADM), characterized in that, The ROADM is a second ROADM, including: Light source: used to generate the first multi-wavelength light signal; Filter: Used to filter the first multi-wavelength optical signal and output multiple single-wavelength optical signals, wherein the multiple single-wavelength optical signals include the first optical signal; Wavelength detection device: used to detect the wavelength of the first optical signal; Processing module: used to calculate the frequency difference between the first optical signal and the optical signal at the standard wavelength based on the wavelength of the first optical signal and the standard wavelength; The light source is also used to generate a frequency of a multi-wavelength optical signal based on the frequency difference alignment, and to generate a second multi-wavelength optical signal after the frequency of the multi-wavelength optical signal generated by alignment. The second multi-wavelength optical signal is output as a single-wavelength second optical signal through the filter. The second optical signal is used to calibrate the frequency offset of the first wavelength selection switch WSS in the second ROADM.

11. The second ROADM according to claim 10, characterized in that, The second ROADM also includes a first power detection device; the first WSS is the WSS used for outputting optical signals in the second ROADM; The first WSS is used to receive the second optical signal and output the second optical signal to the first power detection device; The first power detection device is used to detect the power value of the second optical signal output from the first WSS; The processing module is further configured to detect a first target frequency offset change value of the first WSS based on the power value of the second optical signal, wherein the first target frequency offset change value indicates the offset of the optical frequency corresponding to the pixel of the switching engine in the first WSS.

12. The second ROADM according to claim 11, characterized in that, The single-wavelength optical signal output by the filter for the second multi-wavelength optical signal also includes a third optical signal; The first WSS is also used to receive the third optical signal and output the third optical signal to the first power detection device; The first power detection device is further configured to detect the power value of the third optical signal output from the first WSS; The processing module is further configured to detect a first target frequency offset change value of the first WSS based on the power value of the second optical signal, including: detecting the first target frequency offset change value based on the power value of the second optical signal and the power value of the third optical signal.

13. The second ROADM according to claim 12, characterized in that, The processing module is specifically used for: The first frequency offset change value of the first WSS is calculated based on the power value of the second optical signal and the first reference frequency offset value. The first reference frequency offset value is the frequency offset value of the optical frequency corresponding to the channel transmitting the second optical signal in the first WSS relative to the first standard optical frequency, which is measured in advance. The second frequency offset change value of the first WSS is calculated based on the power value of the third optical signal and the second reference frequency offset value. The second reference frequency offset value is the frequency offset value of the optical frequency corresponding to the channel transmitting the third optical signal in the first WSS relative to the second standard optical frequency, which is measured in advance. The first target frequency offset change value is obtained by averaging the first frequency offset change value and the second frequency offset change value.

14. The second ROADM according to any one of claims 10 to 13, characterized in that, The first WSS is also used to send the second optical signal to the first ROADM, and the second optical signal is used to calibrate the frequency offset of the WSS in the first ROADM and calibrate the output frequency of the light source in the first ROADM.

15. The second ROADM according to any one of claims 10-13, characterized in that, The second ROADM also includes a second power detection device and a second wavelength selection switch (WSS); the second WSS is the WSS used for input optical signals in the second ROADM. The second WSS is used to receive the fourth optical signal and output the fourth optical signal to the second power detection device; The second power detection device is also used to detect the power value of the fourth optical signal output from the second WSS; The processing module is further configured to detect a second target frequency offset change value of the second WSS based on the power value of the fourth optical signal, wherein the second target frequency offset change value indicates the offset of the optical frequency corresponding to the pixel of the switching engine in the second WSS.

16. The second ROADM according to claim 15, characterized in that, The second WSS is also used to receive the fifth optical signal and output the fifth optical signal to the second power detection device; The second power detection device is also used to detect the power value of the fifth optical signal output from the second WSS; The processing module is further configured to detect the second target frequency offset change value of the second WSS based on the power value of the fourth optical signal, including: detecting the second target frequency offset change value based on the power value of the fourth optical signal and the power value of the fifth optical signal.

17. An optical communication system, characterized in that, The communication system includes a first ROADM and a second ROADM; wherein the first ROADM is the first ROADM according to any one of claims 1-9, and the second ROADM is the second ROADM according to any one of claims 10-16.

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