Optical communication method, device, and system

Abstract

The present application provides an optical communication method applied in the field of optical communication. The optical communication method includes the following steps: obtaining a wavelength division multiplexed optical signal, the wavelength division multiplexed optical signal includes N pairs of optical signals, each pair of optical signals includes a first optical signal and a second optical signal with different wavelengths and orthogonal polarizations, N is an integer greater than 1, and the frequency of at least one of the N first optical signals and the frequency of at least one of the N second optical signals are within a ZDF region of an optical fiber; and transmitting the wavelength division multiplexed optical signal through an optical fiber. In the present application, the optical signals with different polarizations are configured within the ZDF region to reduce the influence of four-wave mixing effect.

Description

[Technical field]

[0001] This application claims priority to Chinese Patent Application No. 202210333073.7, entitled "Optical Communication Method, Apparatus, and System," filed with the State Intellectual Property Office of China on March 31, 2022, and claims priority to Chinese Patent Application No. 202210726364.2, entitled "Optical Communication Method, Apparatus, and System," filed with the State Intellectual Property Office of China on June 24, 2022, both of which are incorporated by reference in their entireties herein.

[0002] The present application relates to the field of optical communications, and in particular to optical communications methods, devices, and systems. [Background technology]

[0003] Optical communication systems generally transmit optical signals through optical fibers. To reduce the dispersion penalty, the frequency of a wavelength division multiplexing (WDM) optical signal may be configured near the zero-dispersion frequency (ZDF) of the optical fiber. However, the WDM optical signal near the ZDF has a severe four-wave mixing effect. The four-wave mixing effect degrades the performance of the optical communication system. The impact of the four-wave mixing effect on the performance of the optical communication system is related to the power of the WDM optical signal. To suppress the four-wave mixing phenomenon, the transmission power of the WDM optical signal may be reduced. However, the reduction in the transmission power of the WDM optical signal reduces the power margin of the WDM optical signal. The power margin affects the reliability of the optical communication system. Summary of the Invention

[0004] In conclusion, how to reduce the four-wave mixing effect in optical communication systems is currently a technical problem that needs to be urgently solved.

[0005] The present application provides an optical communication method, apparatus and system, in which optical signals with different polarizations are arranged in a ZDF region to reduce the influence of four-wave mixing effect. [Means for solving the problem]

[0006] A first aspect of the present application provides an optical communication method. The optical communication method may be applied to a transmitting end. The optical communication method includes the following steps: The transmitting end obtains a wavelength division multiplexed optical signal. The wavelength division multiplexed optical signal includes N pairs of optical signals. Each pair of optical signals includes a first optical signal and a second optical signal with different wavelengths and orthogonal polarizations. Each optical signal is a single-polarized optical signal. N is an integer greater than 1. At least one frequency of the N first optical signals and at least one frequency of the N second optical signals are within a ZDF region of the optical fiber. The ZDF of the optical fiber corresponds to a zero-dispersion wavelength (ZDW) of the optical fiber. Thus, the ZDF region also has a corresponding ZDW region. In this case, at least one wavelength of the N first optical signals and at least one wavelength of the N second optical signals are within a ZDW region of the optical fiber. The transmitting end transmits the wavelength division multiplexed optical signal through the optical fiber.

[0007] In the present application, the wavelength division multiplexed optical signal in the ZDF region includes optical signals with orthogonal polarizations. The four-wave mixing effect occurring between the optical signals with orthogonal polarizations is low. Therefore, in the present application, the influence of the four-wave mixing effect can be reduced.

[0008] In an optional method of the first aspect, at least two optical signals having different polarizations are included between two adjacent optical signals having the same polarization in the wavelength division multiplexed optical signal. For example, two second optical signals are included between two adjacent first optical signals, or two first optical signals are included between two adjacent second optical signals. When the frequency interval between adjacent frequencies in the wavelength division multiplexed optical signal is M Gigahertz (GHz), the frequency interval between adjacent frequencies of at least one pair of optical signals having the same polarization in the wavelength division multiplexed optical signal is K×M GHz. K is an integer greater than 2. When the first optical signal and the second optical signal are alternately distributed, the four-wave mixing effect may still occur between the four optical signals having the same polarization. In the present application, in order to avoid the alternate distribution of the first optical signal and the second optical signal, the frequency interval is adjusted by adjusting the polarization order of each pair of optical signals such that at least two optical signals having different polarizations are included between the two adjacent optical signals having the same polarization. Thus, in the present application, the effect of the four-wave mixing effect may be further reduced.

[0009] In an optional method of the first aspect, any four optical signals among the optical signals having the same polarization in the wavelength division multiplexed optical signal satisfy the following condition: B1+B4-B2-B3=B, where B is not equal to 0. For ease of explanation, the above formula is called the first condition. Any four optical signals are sequentially sorted based on the value of frequency. The frequencies of any four optical signals are B1, B2, B3, and B4 in order. The value of (B2+B3) / 2 is within the ZDF region. In the vicinity of the ZDF, the most intense four-wave mixing effect occurs among the four optical signals when B1+B4-B2-B3=0. In the present application, the most intense four-wave mixing effect can be avoided by adjusting the frequency interval. Therefore, in the present application, the influence of the four-wave mixing effect can be reduced.

[0010] In an optional method of the first aspect, B4-B1=B0. The value of B0 is less than 4.5 Tera Hertz (THz). In order to improve the communication bandwidth, optical signals having different frequencies may be used in the WDM optical signal. When the used frequency is sufficient, the four optical signals easily meet the first condition. However, when the frequency interval between B1 and B4 of the four optical signals is large enough, the effect of the four-wave mixing effect is small. Therefore, for the four optical signals with small effect of the four-wave mixing effect, the frequency interval may not need to be adjusted, thereby reducing the complexity of adjusting the frequency interval.

[0011] In an optional method of the first aspect, the frequency intervals of any three optical signals among the optical signals having the same polarization in the wavelength division multiplexed optical signal are different. The frequency intervals of any three optical signals are different means that the frequency intervals between adjacent frequencies of any three optical signals are different. Any three optical signals are sequentially sorted based on the value of the frequency. The frequencies of any three optical signals are B5, B6, and B7 in order. B5+B7-2×B6=B8. When the frequency intervals of any three optical signals are different, B8 is not equal to 0. When the frequency intervals of any three optical signals are the same, B8 is equal to 0. At least two frequencies of any three optical signals are within the ZDF region. In the vicinity of the ZDF, the degenerate four-wave mixing effect may also occur among the three optical signals having the same frequency interval. In the present application, the degenerate four-wave mixing effect occurred among the three optical signals may be avoided by adjusting the frequency intervals. Therefore, in the present application, the influence of the four-wave mixing effect can be reduced.

[0012] In an optional method of the first aspect, the optical communication method further includes the following steps: The transmitting end performs beam combining on the N pairs of optical signals using N polarization-division multiplexers (PDMs) to obtain N beam-combined optical signals. The N pairs of optical signals have a one-to-one correspondence with the N PDMs. The transmitting end performs beam combining on the N beam-combined optical signals using a wavelength-division multiplexer to obtain a wavelength-division multiplexed optical signal. The number of wavelength-division multiplexers can be reduced by first performing polarization beam combining and then performing multiplexing. In addition, the cost of the PDM is much less than the cost of the wavelength-division multiplexer. Therefore, in the present application, the cost of the transmitting end can be reduced.

[0013] In an optional method of the first aspect, the frequency of each of the N pairs of optical signals is adjacent. When the frequency of each pair of optical signals is not adjacent, a cross frequency filter is configured at the input port of the wavelength division multiplexer, resulting in an increase in the cost of the wavelength division multiplexer. However, in the present application, the cost of the wavelength division multiplexer can be reduced. In addition, when the frequency of each pair of optical signals is not adjacent, the optical signals having different polarizations can have different polarization deviations. The polarizations of the first optical signal and the second optical signal are not orthogonal due to the different polarization deviations, resulting in the four-wave mixing effect. Therefore, in the present application, the influence of the four-wave mixing effect can be reduced.

[0014] In an optional method of the first embodiment, N is 2. Based on the wavelength order, the polarization configuration of the N pairs of optical signals is XYYX or YXXY. The interval between any two adjacent optical signals of the N pairs of optical signals is the same. The influence of the four-wave mixing effect can be greatly reduced by controlling the polarization configuration of the N pairs of optical signals. X represents X polarization and Y represents Y polarization.

[0015] In an optional method of the first aspect, the total transmission rate of the N pairs of optical signals is 400 or 800 gigabits per second (Gb / s).

[0016] In an optional method of the first embodiment, N is 4. Based on the wavelength order, the polarization configurations of the N pairs of optical signals are XYYXYXXY, YXXYXYYX, XYYXXYYX, or YXXYYXXY. The influence of the four-wave mixing effect can be significantly reduced by controlling the polarization configurations of the N pairs of optical signals.

[0017] In an optional method of the first aspect, the total transmission rate of the N pairs of optical signals is 0.8 or 1.6 terabits per second (Tb / s).

[0018] In an optional method of the first embodiment, the frequency spacing between adjacent frequencies of the N pairs of optical signals is 400 GHz or 800 GHz.

[0019] In an optional method of the first embodiment, the frequencies of the N pairs of optical signals include two frequencies in a local area network wavelength division multiplexing LAN WDM system, the two frequencies being 229.8 THz and 229 THz, respectively.

[0020] In an optional method of the first embodiment, the frequencies of the N pairs of optical signals further include 231.4 THz and 230.6 THz.

[0021] A second aspect of the present application provides an optical communication device. The optical communication device includes N PDMs and a wavelength division multiplexer. The N PDMs are configured to perform beam combining on N pairs of optical signals to obtain N beam-combined optical signals. N is an integer greater than 1. The N pairs of optical signals are in one-to-one correspondence with the N PDMs. Each of the N beam-combined optical signals includes a first optical signal and a second optical signal having different wavelengths and orthogonal polarizations to each other. A frequency of at least one of the N first optical signals and a frequency of at least one of the N second optical signals are within a ZDF region of an optical fiber. The wavelength division multiplexer is configured to perform beam combining on the N beam-combined optical signals to obtain a wavelength division multiplexed optical signal. The wavelength division multiplexer is configured to transmit the wavelength division multiplexed optical signal through the optical fiber.

[0022] In an optional method of the second aspect, at least two optical signals having different polarizations are included between two adjacent optical signals having the same polarization in the wavelength division multiplexed optical signal. In an optional method of the second aspect, any four optical signals among the optical signals having the same polarization in the wavelength division multiplexed optical signal satisfy the following condition: B1+B4-B2-B3=B, where B is not equal to 0. Any four optical sub-signals are sequentially sorted based on frequency values. The frequencies of any four optical sub-signals are B1, B2, B3, and B4, in order. The value of (B2+B3) / 2 is within the ZDF region.

[0023] In an optional method of the second embodiment, B4-B1=B0, where the value of B0 is less than 4.5 THz.

[0024] In an optional method of the second aspect, any three of the optical signals having the same polarization in the wavelength division multiplexed optical signal have different frequency intervals, and at least two of the frequencies of the any three optical signals are within the ZDF region.

[0025] In an optional method of the second embodiment, the frequencies of each of the N pairs of optical signals are adjacent.

[0026] In an optional method of the second aspect, the wavelength division multiplexer is a polarization-independent non-polarization-maintaining wavelength division multiplexer. When the optical communication device obtains a wavelength division multiplexed optical signal by first performing multiplexing and then performing polarized beam combining, the wavelength division multiplexer is a polarization-maintaining wavelength division multiplexer. If the wavelength division multiplexer is a polarization-independent wavelength division multiplexer, large losses occur when the optical communication device performs polarized beam combining. In the present application, the wavelength division multiplexed optical signal is obtained by first performing polarized beam combining and then multiplexing, and a polarization-independent non-polarization-maintaining wavelength division multiplexer can be used. The polarization-independent non-polarization-maintaining wavelength division multiplexer does not affect the loss during polarized beam combining. In addition, the cost of the polarization-independent non-polarization-maintaining wavelength division multiplexer is lower than the cost of the polarization-maintaining wavelength division multiplexer. Therefore, in the present application, the cost of the optical communication device can be reduced.

[0027] In an optional method of the second embodiment, N is 2. Based on the wavelength order, the polarization arrangement of the N pairs of optical signals is XYYX or YXXY. The interval between any two adjacent optical signals of the N pairs of optical signals is the same. The influence of the four-wave mixing effect can be significantly reduced by controlling the polarization arrangement of the N pairs of optical signals.

[0028] In an optional method of the second embodiment, the total transmission rate of the N pairs of optical signals is 400 Gb / s or 800 Gb / s.

[0029] In an optional method of the second embodiment, N is 4. The polarization configurations of the N pairs of optical signals are XYYXYXXY, YXXYXYYX, XYYXXYYX, or YXXYYXXY. The influence of the four-wave mixing effect can be significantly reduced by controlling the polarization configurations of the N pairs of optical signals.

[0030] In an optional method of the second embodiment, the total transmission rate of the N pairs of optical signals is 0.8 Tb / s or 1.6 Tb / s.

[0031] In an optional method of the second embodiment, the frequency spacing between adjacent frequencies of the N pairs of optical signals is 400 GHz or 800 GHz.

[0032] In an optional method of the second embodiment, the frequencies of the N pairs of optical signals include two frequencies in a local area network wavelength division multiplexing LAN WDM system, the two frequencies being 229.8 THz and 229 THz, respectively.

[0033] In an optional method of the second embodiment, the frequencies of the N pairs of optical signals further include 231.4 THz and 230.6 THz.

[0034] A third aspect of the present application provides an optical communication system. The optical communication system includes a transmitting end and a receiving end. The transmitting end is connected to the receiving end through an optical fiber. The transmitting end is configured to transmit a wavelength division multiplexed optical signal to the receiving end through the optical fiber. The wavelength division multiplexed optical signal includes N pairs of optical signals. Each pair of optical signals includes a first optical signal and a second optical signal having different wavelengths and orthogonal polarizations. N is an integer greater than 1. The frequency of at least one of the N first optical signals and the frequency of at least one of the N second optical signals are within a zero dispersion frequency ZDF region of the optical fiber. The receiving end is configured to receive the wavelength division multiplexed optical signal.

[0035] In an optional method of the third aspect, at least two optical signals having different polarizations are included between two adjacent optical signals having the same polarization in the wavelength division multiplexed optical signal.

[0036] In an optional method of the third aspect, any four optical signals among the optical signals having the same polarization in the wavelength division multiplexed optical signal satisfy the following condition: B1+B4-B2-B3=B, where B is not equal to 0. Any four optical signals are sequentially sorted based on frequency values. The frequencies of any four optical signals are B1, B2, B3, and B4, in that order. The value of (B2+B3) / 2 is within the ZDF region.

[0037] In an optional method of the third aspect, B4-B1=B0, where the value of B0 is less than 4.5 THz.

[0038] In an optional method of the third aspect, any three of the optical signals having the same polarization in the wavelength division multiplexed optical signal have different frequency intervals, and at least two of the frequencies of the any three optical signals are within the ZDF region.

[0039] In an optional method of the third aspect, N is equal to N, and the transmitting end is further configured to perform beam combining on the N pairs of optical signals using the N PDMs to obtain N beam-combined optical signals. The N pairs of optical signals are in one-to-one correspondence with the N PDMs. The transmitting end is further configured to perform beam combining on the N beam-combined optical signals using a wavelength division multiplexer to obtain a wavelength division multiplexed optical signal.

[0040] In an optional method of the third embodiment, the frequencies of each of the N pairs of optical signals are adjacent.

[0041] In an optional method of the third aspect, the wavelength division multiplexer is a polarization independent non-polarization maintaining wavelength division multiplexer.

[0042] In an optional method of the third embodiment, N is 2. Based on the wavelength order, the polarization arrangement of the N pairs of optical signals is XYYX or YXXY. The interval between any two adjacent optical signals of the N pairs of optical signals is the same. The influence of the four-wave mixing effect can be significantly reduced by controlling the polarization arrangement of the N pairs of optical signals.

[0043] In an optional method of the third aspect, the total transmission rate of the N pairs of optical signals is 400 Gb / s or 800 Gb / s.

[0044] In an optional method of the third embodiment, N is 4. The polarization configurations of the N pairs of optical signals are XYYXYXXY, YXXYXYYX, XYYXXYYX, or YXXYYXXY. The influence of four-wave mixing effect can be significantly reduced by controlling the polarization configurations of the N pairs of optical signals.

[0045] In an optional method of the third aspect, the total transmission rate of the N pairs of optical signals is 0.8 Tb / s or 1.6 Tb / s.

[0046] In an optional method of the third aspect, the frequency spacing between adjacent frequencies of the N pairs of optical signals is 400 GHz or 800 GHz.

[0047] In an optional method of the third embodiment, the frequencies of the N pairs of optical signals include two frequencies in a local area network wavelength division multiplexing LAN WDM system, the two frequencies being 229.8 THz and 229 THz, respectively.

[0048] In an optional method of the third embodiment, the frequencies of the N pairs of optical signals further include 231.4 THz and 230.6 THz.

[0049] A fourth aspect of the present application provides a wavelength division multiplexed optical signal. The wavelength division multiplexed optical signal includes N pairs of optical signals. Each pair of optical signals includes a first optical signal and a second optical signal having different wavelengths and orthogonal polarizations. N is an integer greater than 1. At least one frequency of the N first optical signals and at least one frequency of the N second optical signals are within a ZDF region of an optical fiber.

[0050] In an optional method of the fourth aspect, at least two optical signals having different polarizations are included between two adjacent optical signals having the same polarization in the wavelength division multiplexed optical signal.

[0051] In an optional method of the fourth aspect, any four optical signals among the optical signals having the same polarization in the wavelength division multiplexed optical signal satisfy the following condition: B1+B4-B2-B3=B, where B is not equal to 0. Any four optical signals are sequentially sorted based on frequency values. The frequencies of any four optical signals are B1, B2, B3, and B4, in that order. The value of (B2+B3) / 2 is within the ZDF region.

[0052] In an optional method of the fourth aspect, B4-B1=B0, where the value of B0 is less than 4.5 THz.

[0053] In an optional method of the fourth aspect, any three of the optical signals having the same polarization in the wavelength division multiplexed optical signal have different frequency intervals, and at least two of the frequencies of the any three optical signals are within the ZDF region.

[0054] In an optional method of the fourth embodiment, N is 2. Based on the wavelength order, the polarization arrangement of the N pairs of optical signals is XYYX or YXXY. The interval between any two adjacent optical signals of the N pairs of optical signals is the same. The influence of the four-wave mixing effect can be significantly reduced by controlling the polarization arrangement of the N pairs of optical signals.

[0055] In an optional method of the fourth aspect, N is 4. The polarization configurations of the N pairs of optical signals are XYYXYXXY, YXXYXYYX, XYYXXYYX, or YXXYYXXY. The influence of four-wave mixing effect can be significantly reduced by controlling the polarization configurations of the N pairs of optical signals.

[0056] In an optional method of the fourth aspect, the frequency spacing between adjacent frequencies of the N pairs of optical signals is 400 GHz or 800 GHz.

[0057] In an optional method of the fourth embodiment, the frequencies of the N pairs of optical signals include two frequencies in a local area network wavelength division multiplexing LAN WDM system, the two frequencies being 229.8 THz and 229 THz, respectively.

[0058] In an optional method of the fourth embodiment, the frequencies of the N pairs of optical signals further include 231.4 THz and 230.6 THz. [Brief description of the drawings]

[0059] [Figure 1] 1 is a schematic distribution diagram of a wavelength division multiplexed optical signal. [Diagram 2] 1 is a schematic flowchart of an optical communication method according to an embodiment of the present application. [Diagram 3] 1 is a first schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application; [Figure 4] FIG. 2 is a second schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. [Diagram 5] FIG. 4 is a third schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. [Figure 6] FIG. 4 is a fourth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. [Figure 7] FIG. 5 is a fifth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. [Figure 8] FIG. 6 is a sixth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. [Figure 9] FIG. 7 is a seventh schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. [Figure 10] FIG. 8 is an eighth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. [Figure 11] FIG. 9 is a ninth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. [Figure 12] FIG. 10 is a schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. [Figure 13] FIG. 11 is an eleventh schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. [Figure 14] FIG. 12 is a twelfth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. [Figure 15]FIG. 13 is a thirteenth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. [Figure 16] FIG. 1 is a first schematic structural diagram of a transmitting end according to an embodiment of the present application; [Figure 17] FIG. 2 is a second schematic structural diagram of a transmitting end according to an embodiment of the present application; [Figure 18] FIG. 2 is a schematic structural diagram of a receiving end according to an embodiment of the present application; [Figure 19] FIG. 1 is a schematic structural diagram of an optical communication system according to an embodiment of the present application; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] The present application provides an optical communication method, apparatus, and system. In order to reduce the influence of the four-wave mixing effect, optical signals having different polarizations are configured in a ZDF region. It should be understood that the terms "first", "second", etc., used in the present application are used for distinction purposes only, and should not be understood to indicate or imply relative importance or order. In addition, for brevity and clarity, reference numbers and / or letters are repeated in the multiple accompanying drawings of the present application. The repetition does not indicate a strict limiting relationship between the various embodiments and / or configurations.

[0061] The optical communication method of the present application may be applied to an optical communication system. In the optical communication system, an optical signal may be transmitted through an optical fiber. In order to reduce the dispersion penalty, the frequency of the wavelength division multiplexed optical signal may be configured near the ZDF of the optical fiber. However, the wavelength division multiplexed optical signal near the ZDF has a severe four-wave mixing effect. FIG. 1 is a schematic distribution diagram of a wavelength division multiplexed optical signal. In FIG. 1, the horizontal coordinate indicates the frequency, and the left arrow indicates that the frequency gradually increases along the direction of the arrow. As shown in FIG. 1, the wavelength division multiplexed optical signal includes eight optical signals with different frequencies. The eight optical signals are L1 to L8, respectively. In L1 to L8, the frequency interval between adjacent frequencies of the optical signals is the same. The wavelength division multiplexed optical signal is near the ZDF of the optical fiber. For example, the frequency range of the ZDF region of the optical fiber covers frequencies from L6 to L8. In this case, in FIG. 1, there exists a four-wave mixing effect between any four consecutive optical signals. For example, any four consecutive optical signals can be L1 to L4, L2 to L5, L3 to L6, or L5 to L8. The four-wave mixing effect degrades the performance of optical communication systems.

[0062] Therefore, the present application provides an optical communication method. The optical communication method can be applied to a transmitting end. The transmitting end is connected to a receiving end through an optical fiber. The transmitting end or the receiving end may be a switch, a router, a server, etc. The server may be a computing node in a data center. Alternatively, the transmitting end or the receiving end may be an optical module in a switch, a router, or a server. Figure 2 is a schematic flowchart of an optical communication method according to an embodiment of the present application. As shown in Figure 2, the optical communication method includes the following steps:

[0063] Step 201: A transmitting end obtains a wavelength division multiplexed optical signal, which includes a first optical signal and a second optical signal whose polarizations are orthogonal to each other in a ZDF region of an optical fiber.

[0064] The transmitting end may receive a wavelength division multiplexed optical signal from another device. Alternatively, the transmitting end may generate a wavelength division multiplexed optical signal based on an electrical signal. The wavelength division multiplexed optical signal includes N pairs of optical signals, where N is an integer greater than 1. Each pair of optical signals includes a first optical signal and a second optical signal with different wavelengths and orthogonal polarizations. Each optical signal is a single-polarized optical signal. Specifically, each optical signal of one wavelength includes at most an optical signal having X polarization or an optical signal having Y polarization. The transmitting end is connected to the receiving end through an optical fiber. The frequency of at least one of the N first optical signals and the frequency of at least one of the N second optical signals are within the ZDF region of the optical fiber. The optical fiber has a ZDF or ZDW. A zero-dispersion wavelength means that the group velocity dispersion (also called group delay dispersion or second-order dispersion per unit length) of the optical fiber at that frequency is zero. Group velocity dispersion is the decrease in the group velocity of light in a transparent medium related to the frequency or wavelength of the light. ZDF=C / ZDW, where C is the speed of light. Due to the manufacturing process, the ZDF of different optical fibers may be different. The ZDF region may be a frequency range specified in the standard. For example, in standard single-mode fiber (SSMF), the ZDF region is from 230.609 THz to 226.429 THz. In optical fibers manufactured by manufacturers according to the standard, the ZDF is within the ZDF region. The ZDF region may also be called a continuous first frequency region. The center of the first frequency region is the ZDF of the optical fiber. The frequency width of the first frequency region is less than a first threshold. For example, the first threshold is 4.5 THz.

[0065] It should be understood that in practical applications, wavelength and frequency can be converted to each other. Thus, the ZDF region has a corresponding ZDW region. For example, when the ZDF region is from 230.609 THz to 226.429 THz, the ZDW region corresponding to the ZDF region is from 1300 nm to 1324 nm. Thus, in this application, at least one wavelength of the N first optical signals and at least one wavelength of the N second optical signals are within the ZDW region of the optical fiber. In this application, unless otherwise specified, the frequency of the optical signal is the center frequency of the optical signal. The wavelength of the optical signal is the center wavelength of the optical signal. The frequency interval is the frequency interval between two center frequencies.

[0066] In the present application, N is an integer greater than 1. Thus, N can be 2, 4, 6, 8, etc. In the following, the wavelength division multiplexed optical signal of the present application is described using an example in which N is equal to 4. FIG. 3 is a first schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. As shown in FIG. 3, the wavelength division multiplexed optical signal includes four pairs of optical signals having different frequencies. The four pairs of optical signals include eight optical signals. The eight optical signals are L1 to L8, respectively. L1, L3, L5, and L7 are first optical signals having X polarization. L2, L4, L6, and L8 are second optical signals having Y polarization. The first optical signals and the second optical signals are distributed alternately. The ZDF region of the optical fiber is assumed to cover the frequencies of L3 to L8. In this case, the ZDF region includes three first optical signals having X polarization and three second optical signals having Y polarization.

[0067] Step 202: The transmitting end transmits a wavelength division multiplexed optical signal through an optical fiber. The transmitting end is connected to the receiving end through the optical fiber. The optical fiber may be a non-polarization maintaining optical fiber. The transmitting end transmits the wavelength division multiplexed optical signal through the optical fiber to the receiving end. The receiving end may transmit the wavelength division multiplexed optical signal to another device. Alternatively, the receiving end may perform demultiplexing on the wavelength division multiplexed optical signal to obtain N first optical signals and N second optical signals. The receiving end converts the N first optical signals and the N second optical signals into 2×N electrical signals. Each optical signal has a one-to-one correspondence with each electrical signal. The receiving end may perform data processing on the 2×N electrical signals.

[0068] In FIG. 3, the ZDF region includes a first optical signal and a second optical signal whose polarizations are orthogonal to each other. No four-wave mixing effect occurs between the first optical signal and the second optical signal. For example, in FIG. 1, the four-wave mixing effect occurs between L5 and L8. In FIG. 3, L5 and L7 are the first optical signal with X polarization, and L6 and L8 are the second optical signal with Y polarization. Therefore, no four-wave mixing effect occurs between L5 and L8. Therefore, in the present application, the influence of the four-wave mixing effect can be reduced.

[0069] In FIG. 3, the first optical signal and the second optical signal are distributed alternately. Therefore, one optical signal with different polarization is included between two adjacent optical signals with the same polarization. In this case, the four-wave mixing effect can still occur between four optical signals with the same polarization. For example, the four-wave mixing effect can still occur between L1, L3, L5, and L7. Therefore, in this embodiment of the present application, the four-wave mixing effect can be further reduced by adjusting the frequency interval. Adjusting the frequency interval is to change the polarization distribution of the wavelength division multiplexed optical signal without changing the amount of optical signals and the frequency of the optical signals. FIG. 4 is a second schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. As shown in FIG. 4, based on FIG. 3, L2, L3, L4, L6, and L7 are changed so that at least two optical signals with different polarization are included between two adjacent optical signals with the same polarization in the wavelength division multiplexed optical signal. Specifically, the four first optical signals are L1, L4, L5, and L6, respectively. The four second optical signals are L2, L3, L7, and L8, respectively. Two second optical signals are included between L1 and L4. Three first optical signals are included between L3 and L7. By adjusting the frequency interval, the four-wave mixing effect may not occur between L1, L4, L5, and L6, thereby reducing the influence of the four-wave mixing effect.

[0070] For example, the frequency spacing between adjacent frequencies in a wavelength division multiplexed optical signal is M GHz. In FIG. 3, the frequency spacing between adjacent first optical signals is 2×M GHz. The frequency spacing between adjacent second optical signals is 2×M GHz. In FIG. 4, the frequency spacing between L1 and L4 is 3×M GHz. The frequency spacing between L4 and L5 is M GHz. The frequency spacing between L3 and L7 is 4×M GHz.

[0071] In FIG. 4, the central frequencies of the four second optical signals are assumed to be B1 to B4, respectively. The four second optical signals are sequentially sorted based on the value of the frequency. The central frequency of L2 is B1. The central frequency of L3 is B2. The central frequency of L7 is B3. The central frequency of L8 is B4. The four second optical signals have a central axis of symmetry. In this case, B1+B4-B2-B3=B. B is equal to 0. For ease of explanation, this formula is called the first condition. When B is equal to 0 and the value of (B2+B3) / 2 is within the ZDF region, the four second optical signals can still produce the four-wave mixing effect. Therefore, in this embodiment of the present application, the frequency interval can be adjusted so that B is not equal to 0. FIG. 5 is a third schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. As shown in FIG. 5, based on FIG. 3, the polarization of L3 and L6 is changed. The four first optical signals are L1, L5, L6, and L7, respectively. The four second optical signals are L2, L3, L4, and L8, respectively. The four second optical signals are sequentially sorted based on the frequency values. The center frequencies of the four second optical signals are assumed to be B1 to B4, respectively. In this case, B1+B4-B2-B3=B. B is not equal to 0. Similarly, in FIG. 5, when the center frequencies of the four first optical signals are B1 to B4, respectively, B is not equal to 0.

[0072] From the above description, it can be seen that N is an integer greater than 3. Therefore, as N increases, the four optical signals in the WDM optical signal easily meet the first condition mentioned above. However, in practical applications, when B is equal to 0 and the difference between B1 and B4 is large, the impact of the four-wave mixing effect occurring among the four optical signals is small. Therefore, in order to reduce the complexity of adjusting the frequency interval, the difference between B1 and B4 can be limited to be less than 4.5 THz. When the difference between B1 and B4 is greater than or equal to 4.5 THz, the transmitting end does not need to adjust the frequency interval to allow the four optical sub-signals not to meet the first condition.

[0073] In practical application, the degenerate four-wave mixing effect may occur among three optical signals having the same frequency interval. The three optical signals are sorted sequentially based on frequency. The center frequencies of the three optical signals are B5, B6, and B7 in order. The three optical signals have frequency intervals, which means that B8 is equal to 0. B5+B7-2×B6=B8. For example, in FIG. 5, the frequency intervals of L2, L3, and L4 are the same. In this case, the degenerate four-wave mixing effect may occur among L2, L3, and L4. Similarly, the degenerate four-wave mixing effect may occur among L5, L6, and L7. Therefore, in this embodiment of the present application, the frequency intervals may be further adjusted so that the three optical signals having the same frequency intervals do not exist in the vicinity of the ZDF. FIG. 6 is a fourth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. As shown in FIG. 6, based on FIG. 3, the polarization of L3 and L4 is changed. The four first optical signals are L1, L4, L5, and L7, respectively. The four second optical signals are L2, L3, L6, and L8, respectively. Three optical signals having the same frequency interval do not exist among the four second optical signals. Specifically, the frequency interval between L2 and L3 is M GHz. The frequency interval between L3 and L6 is 3×M GHz. The frequency interval between L6 and L8 is 2×M GHz. Similarly, three optical signals having the same frequency interval do not exist among the four first optical signals. The frequency interval between L1 and L4 is 3×M GHz. The frequency interval between L4 and L5 is M GHz. The frequency interval between L5 and L7 is 2×M GHz.

[0074] From the above description, we can see that N is an integer greater than 3. Therefore, as N increases, three optical signals with the same frequency interval are more likely to exist in a WDM optical signal. However, in practical applications, when the frequencies of the three optical signals are far away from the ZDF region, the impact of the four-wave mixing effect occurring between the three optical signals is small. Therefore, in order to reduce the complexity of adjusting the frequency interval, only the frequency intervals of the three optical signals near the ZDF region can be adjusted. In the three optical signals, at least two frequencies of the optical signals are within the ZDF region.

[0075] The optical communication method of the present application may be applied to a fronthaul communication system, a data center communication system, a metropolitan area network communication system, etc. The fronthaul communication system may be a local area network wavelength division multiplexing (LAN WDM) system, or other possible wavelength division multiplexing systems. In the following, the LAN WDM system is used as an example to describe the wavelength division multiplexing optical signal of the present application. The LAN WDM system may use eight wavebands within the range of 1273 nm to 1309 nm in the O waveband.

[0076] [Table 1]

[0077] Please refer to Table 1 for the center frequencies, center wavelengths, and wavelength ranges of the eight wavebands of the LAN WDM system. In Table 1, the wavelength division multiplexed optical signal includes eight optical signals L1 to L8 with different frequencies. The frequency interval between adjacent frequencies of L1 to L4 is 800 GHz. The frequency interval between adjacent frequencies of L5 to L8 is 800 GHz. The frequency interval between L4 and L5 is 1600 GHz.

[0078] Based on the waveband distribution shown in Table 1, wavelength division multiplexed optical signals with different polarization distributions can be obtained. FIG. 7 is a fifth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. As shown in FIG. 7, the wavelength division multiplexed optical signal includes eight optical signals with different frequencies. The eight optical signals are L1 to L8, respectively. The center frequencies of L1 to L8 correspond to the eight center frequencies listed in Table 1. L1, L4, L6, and L7 are first optical signals with X polarization. L2, L3, L5, and L8 are second optical signals with Y polarization. In a specific example, the polarization arrangement of the eight optical signals is XYYXYXXY.

[0079] The frequency range of the ZDF region of the optical fiber is assumed to be from 230.609 THz to 226.429 THz. In this case, the ZDF region covers the frequencies of L6, L7, and L8. In this case, the ZDF region includes two first optical signals with X polarization and one second optical signal with Y polarization. In Figure 6, the four optical signals that satisfy the first condition and the three optical signals with the same frequency interval do not exist in the vicinity of the ZDF.

[0080] It should be understood that FIG. 7 is merely an example of a wavelength division multiplexing optical signal provided in this embodiment of the present application. For example, in practical applications, based on FIG. 7, the polarization of all optical signals in the wavelength division multiplexing optical signal may be alternately polarized, such that L1, L4, L6, and L7 are the first optical signals of Y polarization, and L2, L3, L5, and L8 are the second optical signals of X polarization. In this case, the polarization arrangement of the eight optical signals may be described as YXXYXYYX. In practical applications, the frequency interval between L4 and L5 may be 800 GHz or 1600 GHz. As another example, the polarization arrangement of the eight optical signals may alternatively be XYYXXYYX or YXXYYXXY. When the transmission rate of each of the eight optical signals in the wavelength division multiplexing optical signal is 200 Gb / s (for example, when PAM-4 modulation with 100 G baud rate is used), the total transmission rate of the eight optical signals is 1.6 Tb / s. When the transmission rate of each of the eight optical signals in the wavelength division multiplexed optical signal is 100 Gb / s, the total transmission rate of the eight optical signals is 800 Gb / s.

[0081] In practical applications, the polarization distribution of the wavelength division multiplexed optical signal may be the same as the polarization distribution of the wavelength division multiplexed optical signal in Figures 3 to 6. For example, in the wavelength division multiplexed optical signal, the four first optical signals are L1, L4, L5, and L7, respectively. The four second optical signals are L2, L3, L6, and L8, respectively. The center frequencies of L1 to L8 correspond to the eight center frequencies listed in Table 1.

[0082] From the above description, it can be seen that at least three optical signals are required to produce the four-wave mixing effect. Therefore, after the influence of the four-wave mixing effect is reduced in an orthogonal polarization manner, at least five optical signals are required to produce the four-wave mixing effect. FIG. 8 is a sixth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. As shown in FIG. 8, the wavelength division multiplexed optical signal includes five optical signals with different frequencies. The five optical signals are L4 to L8, respectively. L4, L6, and L8 are first optical signals with X polarization. L5 and L7 are second optical signals with Y polarization. In this case, the frequency intervals of L4, L6, and L8 are the same. The degenerate four-wave mixing effect may occur between L4, L6, and L8. The frequency intervals are adjusted so that three optical signals with the same frequency interval do not exist in an optical signal with the same polarization. FIG. 9 is a seventh schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. As shown in Figure 9, based on Figure 8, the polarization of L6 and L7 is changed. In this case, L4, L7, and L8 are the first optical signals with X polarization. L5 and L6 are the second optical signals with Y polarization. The frequency intervals between adjacent frequencies of L4, L7, and L8 are different. The frequency interval between L4 and L7 is 2 x M GHz. The frequency interval between L7 and L8 is M GHz. Therefore, the influence of the four-wave mixing effect is reduced by adjusting the frequency intervals.

[0083] From the above description, it can be seen that N is an integer greater than 3. In practical applications, N can be a product of 2 and Z. Z is an integer greater than 0. For example, N may be 2, 4, 6, or 8. In Figs. 3 to 7, N is 4. An example in which N is 8 is used below to describe the wavelength division multiplexed optical signal provided in this embodiment of the present application. Fig. 10 is an eighth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. As shown in Fig. 10, the wavelength division multiplexed optical signal includes 16 optical signals having different frequencies. The 16 optical signals are L1 to L8, L1+ to L4+, and L5- to L8-, respectively. For the center frequencies of L1 to L8, please refer to the eight center frequencies listed in Table 1. The frequency of L1+ is between the frequency of L1 and the frequency of L3. The frequency of L2+ is between the frequency of L2 and the frequency of L3. Similarly, the frequency of L5- is between the frequency of L4 and the frequency of L5. The frequency of L6- is between the frequency of L5 and the frequency of L6. The 16 optical signals include eight first optical signals with X polarization and eight second optical signals with Y polarization. The eight first optical signals are L1, L2, L3+, L4, L5-, L6-, L7, and L8-, respectively. The eight second optical signals are L1+, L2+, L3, L4+, L5, L6, L7-, and L8, respectively.

[0084] The frequency range of the ZDF region of the optical fiber is assumed to be from 230.609 THz to 226.429 THz. In this case, the frequency range of the ZDF region covers the frequencies of L6, L7-, L7, L8-, and L8. In FIG. 10, there are no four optical signals that satisfy the first condition and have a value of (B2+B3) / 2 within the ZDF region. However, the frequency intervals between adjacent frequencies of L8, L7-, and L5 are the same. The frequencies of L8 and L7- are within the ZDF region. The degenerate four-wave mixing effect may occur between L8, L7-, and L5. Therefore, the frequency intervals may be adjusted so that three optical signals with the same frequency intervals do not exist in the vicinity of the ZDF. FIG. 11 is a ninth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. As shown in FIG. 11, based on FIG. 10, the polarizations of L2, L2+, L3, L3+, L6-, L6, L7-, and L7 are changed. In this case, three optical signals having the same frequency spacing are not present in the vicinity of the ZDF region.

[0085] In Figures 10 and 11, the polarization distribution of L1 to L4+ is the same as that of L5- to L8. Specifically, in Figure 10, the polarization distribution of L1 to L4+ is 10100110. The polarization distribution of L5- to L8 is 10100110. 1 represents X polarization. 0 represents Y polarization. In Figure 11, the polarization distribution of L1 to L4+ is 10011010. The polarization distribution of L5- to L8 is 10011010. The complexity of adjusting the frequency interval can be reduced by using the same polarization distribution.

[0086] In Fig. 11, the polarization distributions of L1 to L4+ are the same as those in Fig. 6. Therefore, for the description of the wavelength division multiplexed optical signal when N is equal to 16, please refer to the relevant descriptions of Figs. 3 to 7. For example, in Fig. 7, the polarization distribution of the wavelength division multiplexed optical signal is 10010110. When N is equal to 16, in a possible example, the polarization distribution of the wavelength division multiplexed optical signal is 1001011010010110. Similarly, when N is equal to 32, please refer to the relevant descriptions of Figs. 3 to 7.

[0087] To explain the wavelength division multiplexed optical signal provided in this embodiment of the present application, an example in which N is 2 is used below. FIG. 12 is a tenth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. As shown in FIG. 12, the wavelength division multiplexed optical signal includes two pairs of optical signals having different frequencies. The two pairs of optical signals include L5 to L8. For the center frequencies, center wavelengths, and wavelength ranges of L5 to L8, please refer to L5 to L8 in Table 1. The two pairs of optical signals include two first optical signals with X polarization and two second optical signals with Y polarization. The two first optical signals are L5 and L7, respectively. The two second optical signals are L6 and L8, respectively.

[0088] It should be understood that in FIG. 12, each pair of optical signals includes one first optical signal with X polarization and one second optical signal with Y polarization. In practical applications, the polarization states of different pairs of optical signals may be different. For example, a wavelength division multiplexed optical signal includes two pairs of optical signals. The two pairs of optical signals include a first pair of optical signals and a second pair of optical signals. The first pair of optical signals includes a first optical signal with X polarization and a second optical signal with Y polarization. The second optical signal includes a third optical signal with X' polarization and a fourth optical signal with Y' polarization. The X polarization is orthogonal to the Y polarization. The X polarization is different from the X' polarization. The Y polarization is different from the Y' polarization.

[0089] From the above description, it can be seen that in this embodiment of the present application, the frequency interval between optical signals having the same polarization can be adjusted. For example, the polarization arrangement of four adjacent equally-spaced optical signals in a wavelength division multiplexing optical signal can be XYYX or YXXY, and the four-wave mixing effect of four adjacent equally-spaced optical signals in a wavelength division multiplexing optical signal is small in the random birefringence optical fiber model. FIG. 13 is an eleventh schematic distribution diagram of a wavelength division multiplexing optical signal according to an embodiment of the present application. As shown in FIG. 13, based on FIG. 12, the polarization of L7 and L8 is changed. In this case, L5 and L8 are X-polarized. L6 and L7 are Y-polarized. When the transmission rate of each of the four optical signals in the wavelength division multiplexing optical signal is 100 Gb / s, the total transmission rate of the four optical signals is 400 Gb / s. Alternatively, based on FIG. 13, the polarization of all of the four optical signals in the wavelength division multiplexing optical signal may be changed. In this case, L5 and L8 are Y-polarized. L6 and L7 are X-polarized. In practical applications, the polarization configuration XYYX or YXXY can be used for four adjacent equally spaced optical signals in any optical signal whose quantity is a multiple of 4 in a wavelength division multiplexed optical signal. For example, the polarization configurations of eight optical signals in a wavelength division multiplexed optical signal may be XYYXYXXY, YXXYXYYX, XYYXXYYX, or YXXYYXXY.

[0090] To explain the wavelength division multiplexed optical signal provided in this embodiment of the present application, an example in which N is 6 is used below. FIG. 14 is a twelfth schematic distribution diagram of a wavelength division multiplexed optical signal according to an embodiment of the present application. As shown in FIG. 14, the wavelength division multiplexed optical signal includes six pairs of optical signals having different frequencies. The six pairs of optical signals include L1 to L12. For the center frequency, center wavelength, and wavelength range of L1 to L12, please refer to L1 to L12 in Table 2. The six pairs of optical signals include six first optical signals with X polarization and six second optical signals with Y polarization. The six first optical signals are L1, L3, L5, L7, L9, and L11, respectively. The six second optical signals are L2, L4, L6, L8, L10, and L12, respectively.

[0091] [Table 2]

[0092] From the above description, it can be seen that in this embodiment of the present application, the frequency interval between optical signals having the same polarization can be adjusted. Figure 15 is a thirteenth schematic distribution diagram of a wavelength division multiplexing optical signal according to an embodiment of the present application. As shown in Figure 15, based on Figure 14, the polarization of L7 and L8 is changed. In this case, the six first optical signals are L1, L3, L5, L8, L9, and L11, respectively. The six second optical signals are L2, L4, L6, L7, L10, and L12, respectively.

[0093] The above describes an optical communication method provided in an embodiment of the present application. The following describes an optical communication device provided in an embodiment of the present application. The optical communication device is also called a transmitting end. FIG. 16 is a first schematic structural diagram of a transmitting end according to an embodiment of the present application. As shown in FIG. 16, the transmitting end 1600 includes N PDMs 1603 to 1606 and a wavelength division multiplexer 1601. N is an integer greater than 1. In FIG. 16, an example in which N is equal to 4 is used for explanation. The N PDMs 1603 to 1606 are configured to perform beam combining on N pairs of optical signals to obtain N beam combined optical signals. The N pairs of optical signals are in one-to-one correspondence with the N PDMs 1603 to 1606. The N pairs of optical signals include a first pair of optical signals, a second pair of optical signals, a third pair of optical signals, and a fourth pair of optical signals, respectively. The first pair of optical signals corresponds to the PDM 1603. The first pair of optical signals includes L1 and L2. The second pair of optical signals includes L3 and L4. The third pair of optical signals includes L5 and L6. The fourth pair of optical signals includes L7 and L8. Each of the N beam combined optical signals includes a first optical signal and a second optical signal with different wavelengths and orthogonal polarizations. The first optical signal is X polarized and the second optical signal is Y polarized. The X polarized light is orthogonal to the Y polarized light.

[0094] The PDM may be a polarization beam combiner (PBC) or a polarization rotation beam combining device. When the PDM is a polarization rotation beam combining device, L1 to L8 are all X-polarized or Y-polarized. The polarization rotation beam combining device is configured to perform polarization rotation beam combining on optical signals with the same polarization to obtain a beam-combined optical signal. The beam-combined optical signal includes a first optical signal with X-polarization and a second optical signal with Y-polarization. When the PDM is a PBC, each PBC receives a first optical signal with X-polarization and a second optical signal with Y-polarization. The PBC is configured to perform polarization beam combining on two optical signals with different polarizations to obtain a beam-combined optical signal.

[0095] The wavelength division multiplexer 1601 is configured to perform beam combining on the N beam-combined optical signals to obtain a wavelength division multiplexed optical signal. At least one frequency of the N first optical signals and at least one frequency of the N second optical signals are within the ZDF region of the optical fiber. For the description of the wavelength division multiplexed optical signal, please refer to the above description of the wavelength division multiplexed optical signal in FIG. 2 to FIG. 15. The transmitting end 1600 is connected to the receiving end through the optical fiber 1602. The wavelength division multiplexer 1601 is configured to transmit the wavelength division multiplexed optical signal to the receiving end through the optical fiber 1602. The transmitting end 1600 can generate N pairs of optical signals based on the electrical signal. FIG. 17 is a second schematic structural diagram of the transmitting end according to an embodiment of the present application. As shown in FIG. 17, based on FIG. 16, the transmitting end 1600 further includes an optical modulator 1701, a laser 1702, and a processor 1703.

[0096] The processor 1703 is configured to transmit an electrical signal to the optical modulator 1701. The processor 1703 may be a central processing unit (CPU), a network processor (NP), or a combination of a CPU and an NP. The processor 1703 may also be a graphic processing unit (GPU). The processor 1703 may further include a hardware chip or other general-purpose processor. The aforementioned hardware chip may be an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof.

[0097] The laser 1702 is configured to generate 2×N laser lights having different wavelengths. In the following, an example in which N is equal to 4 is used for explanation. For example, the laser 1702 includes eight sub-lasers. Each sub-laser is configured to generate a laser light having one wavelength. The optical modulator 1701 is configured to modulate the eight laser lights based on an electrical signal to obtain eight optical signals L1 to L8. The optical modulator 1701 may obtain L1 to L8 through intensity modulation or phase modulation. The optical modulator 1701 is further configured to send L1 to L8 to the polarization rotation beam combining devices 1603 to 1606. Each polarization rotation beam combining device is configured to perform polarization rotation beam combining on two optical signals and output a beam combined optical signal. The wavelength division multiplexer 1601 is configured to perform beam combining on the N beam combined optical signals to obtain a wavelength division multiplexed optical signal. Wavelength division multiplexer 1601 is further configured to transmit the wavelength division multiplexed optical signal over optical fiber 1602 to a receiving end.

[0098] In another embodiment, the transmitting end 1600 may further include a memory. The memory may be configured to store the electrical signal. The processor 1703 may be configured to retrieve the electrical signal from the memory. The memory may be a non-volatile memory, such as a hard disk drive (HDD), or a volatile memory, such as a random-access memory (RAM). The memory may be any other medium, including but not limited to, that can carry or store expected program code in the form of instructions or data structures and that can be accessed by a computer.

[0099] In practical applications, one device may include both a transmitting end 1600 and a receiving end. The other device may include both a receiving end and a transmitting end. The transmitting end 1600 of one device is configured to transmit a wavelength division multiplexed optical signal to the receiving end of the other device. The transmitting end of the other device may also be configured to transmit a wavelength division multiplexed optical signal to the receiving end of the one device. In this case, the receiving end of one device may receive a wavelength division multiplexed optical signal from the other device through the optical fiber 1602. For a description of the wavelength division multiplexed optical signal, please refer to the above description of the wavelength division multiplexed optical signal in Figures 2 to 15. In this case, the receiving end may process the wavelength division multiplexed optical signal in any one of the following ways. For example, the receiving end transmits the wavelength division multiplexed optical signal to another device. In another example, the receiving end converts the wavelength division multiplexed optical signal into an electrical signal and performs data processing on the electrical signal.

[0100] In the following, an example in which the receiving end converts the wavelength division multiplexed optical signal into an electrical signal is used for explanation. FIG. 18 is a schematic structural diagram of a receiving end according to an embodiment of the present application. As shown in FIG. 18, the receiving end 1800 includes a wavelength division demultiplexer 1801, an optical-electrical conversion module 1802, and a processor 1803. The wavelength division demultiplexer 1801 is configured to receive a wavelength division multiplexed optical signal from a transmitting end of another device through an optical fiber 1602. The wavelength division demultiplexer 1801 is configured to perform wavelength conversion demultiplexing on the wavelength division multiplexed optical signal to obtain eight optical signals L1 to L8. The optical-electrical conversion module 1802 is configured to demodulate L1 to L8 to obtain eight electrical signals. The processor 1803 is configured to perform data processing on the electrical signal. For the description of the processor 1803, please refer to the above description of the processor 1703 in FIG. 17.

[0101] It should be understood that Figures 16 to 18 are only some examples of the transmitting end or the receiving end provided in the embodiments of the present application. In practical applications, those skilled in the art may adaptively modify the above examples as necessary. The adaptive modifications include, but are not limited to, any one of the following contents:

[0102] First, the frequency interval of one or more pairs of optical signals of the N pairs of optical signals is changed. For example, in FIG. 16, the frequencies of the optical signals of each pair are adjacent. The frequencies of L1 and L2 of the first pair of optical signals are adjacent. The frequencies of L3 and L4 of the second pair of optical signals are adjacent. In practical applications, the first pair of optical signals may include L1 and L4. The second pair of optical signals may include L2 and L3. In this case, the frequencies of L1 and L4 of the first pair of optical signals are adjacent.

[0103] Secondly, the transmitting end 1600 further includes a polarization rotator. For example, in FIG. 17, the PDM is a polarization rotation beam combining device. The polarization rotation beam combining devices 1603 to 1606 receive optical signals with X polarization or Y polarization. In practical applications, the PDM may be a PBC. The transmitting end 1600 further includes a polarization rotator. The polarization rotator is configured to perform polarization rotation on L2, L4, L6, and L8 output by the optical modulator 1701 to obtain L2, L4, L6, and L8 with Y polarization. Each PBC is configured to perform polarization beam combining on the first optical signal with X polarization and the second optical signal with Y polarization to obtain a beam combined optical signal.

[0104] Third, the transmitting end 1600 uses a laser to generate laser light. For example, in FIG. 17, the transmitting end 1600 may use eight sub-lasers to generate laser light L1 to L8. In practical application, the transmitting end 1600 may include only one laser. This one laser is configured to generate laser light having multiple frequencies. The laser light having multiple frequencies includes L1 to L8.

[0105] Fourth, the transmitting end 1600 first performs multiplexing and then performs polarization beam combining. For example, in FIG. 17, the transmitting end 1600 first performs polarization beam combining using a polarization rotating beam combining device, and then performs multiplexing using a wavelength division multiplexer 1601. In practical applications, the transmitting end 1600 may include two wavelength division multiplexers and a PBC. One wavelength division multiplexer is configured to perform beam combining on four optical signals with X polarization to obtain a beam combined optical signal with X polarization. The other wavelength division multiplexer is configured to perform beam combining on four optical signals with Y polarization to obtain a beam combined optical signal with Y polarization. The PBC is configured to perform polarization beam combining on the beam combined optical signals with and the beam combined optical signals with X polarization to obtain a wavelength division multiplexed optical signal.

[0106] Fifth, the transmitting end 1600 uses one wavelength division multiplexer to directly perform multiplexing on the N optical signals with X polarization and the N optical signals with Y polarization, and ensures the polarization configuration of the N pairs of optical signals. In this case, the transmitting end 1600 may not need to include N PDMs. For the polarization configuration of the N pairs of optical signals, please refer to the description of any one of the above examples.

[0107] In practical application, the PDMs 1603 to 1606 can be connected to the wavelength division multiplexer 1601 through optical fibers. The optical fibers can be non-polarization-maintaining optical fibers. When the transmitting end 1600 first performs multiplexing and then performs polarization beam combining, the wavelength division multiplexer is connected to the PBC through polarization-maintaining optical fibers. Therefore, in this embodiment of the present application, the cost of the transmitting end 1600 can be reduced.

[0108] The PDMs 1603 to 1606 and the optical modulator 1701 may be implemented on the same integrated optical chip. The material of the PDMs 1603 to 1606 or the optical modulator 1701 may be indium phosphide InP, silicon-on-insulator (SoI), or lithium niobate-on-insulator (LNoI). The material of the wavelength division multiplexer 1601 may be thick silicon or planar lightwave circuit (PLC). The wavelength division multiplexer 1601 may be implemented on an optical chip with polarization-maintaining or polarization-independent function. The two optical chips may be directly coupled or connected through optical fiber. The optical fiber may be a non-polarization-maintaining optical fiber. In this embodiment, the size of the transmitting end 1600 may be reduced, the complexity of the assembly of the transmitting end 1600 is simplified, and the cost of the transmitting end 1600 is reduced.

[0109] The following describes an optical communication system provided in an embodiment of the present application. Figure 19 is a schematic structural diagram of an optical communication system according to an embodiment of the present application. As shown in Figure 19, the optical communication system 1900 includes a transmitting end 1901 and a receiving end 1902. The transmitting end 1901 is connected to the receiving end 1902 through an optical fiber. The transmitting end 1901 is configured to transmit a wavelength division multiplexed optical signal to the receiving end 1902 through the optical fiber. The wavelength division multiplexed optical signal includes N pairs of optical signals. Each pair of optical signals includes a first optical signal and a second optical signal with different wavelengths and orthogonal polarizations. N is an integer greater than 1. At least one frequency of the N first optical signals and at least one frequency of the N second optical signals are within the zero dispersion frequency ZDF region of the optical fiber. The receiving end 1902 is configured to receive the wavelength division multiplexed optical signal. For the description of the transmitting end 1901, please refer to the above description of the transmitting end 1600 in Figure 16 or Figure 17. For a description of the receiving end 1902, please refer to the above description of the receiving end 1800 in Figure 18. For a description of the wavelength division multiplexed optical signal, please refer to the above description of the wavelength division multiplexed optical signal in Figures 2 to 15.

[0110] In another embodiment, the optical communication system may further include a first device and a second device. The first device is configured to send 2×N electrical signals to a sending end 1901. The sending end 1901 is further configured to convert the 2×N electrical signals into N first optical signals and N second optical signals. Each optical signal has a one-to-one correspondence with each electrical signal. The sending end 1901 is further configured to obtain a wavelength division multiplexed optical signal based on the N second optical signals and the N first optical signals. The receiving end 1902 is further configured to split the wavelength division multiplexed optical signal into N first optical signals and N second optical signals, and convert the N first optical signals and the N second optical signals into 2×N electrical signals. The receiving end 1902 is further configured to send the 2×N electrical signals to a second device.

[0111] The above description is merely a specific implementation form of the present application, and is not intended to limit the protection scope of the present application. Any variations or replacements that can be easily thought of by those skilled in the art within the technical scope disclosed in this application shall be included in the protection scope of the present application. [Explanation of symbols]

[0112] 1600,1901 Sending end 1601 Wavelength Division Multiplexer 1602 Optical Fiber 1603~1606 Polarization Division Multiplexer (PDM) 1701 Optical Modulator 1702 Laser 1703,1803 processors 1800,1902 Receiving end 1801 Wavelength Division Demultiplexer 1802 Optical-electrical conversion module 1900 Optical Communication System

Claims

1. 1. An optical communication method, comprising: obtaining a wavelength division multiplexed optical signal, the wavelength division multiplexed optical signal including N pairs of optical signals, each pair of optical signals including a first optical signal and a second optical signal having different wavelengths and orthogonal polarizations, N being an integer greater than 1, and a frequency of at least one of the N first optical signals and a frequency of at least one of the N second optical signals being within a zero dispersion frequency (ZDF) region of an optical fiber; transmitting the wavelength division multiplexed optical signal through the optical fiber; An optical communication method comprising:

2. The method of claim 1 , wherein at least two optical signals having different polarizations are included between two adjacent optical signals having the same polarization in the wavelength division multiplexed optical signal.

3. Any four optical signals among the optical signals having the same polarization in the wavelength division multiplexed optical signal satisfy the following condition: B1+B4-B2-B3=B, where B is not equal to 0, and the four optical signals are sequentially sorted based on frequency values, the frequencies of the four optical signals are B1, B2, B3, and B4, in that order, and the value of (B2+B3) / 2 is within the ZDF region; The method according to claim 2, wherein

4. 4. The method of claim 3, wherein B4-B1=B0, and the value of B0 is less than 4.5 THz.

5. The frequency intervals of any three optical signals among the optical signals having the same polarization in the wavelength division multiplexed optical signal are different, and the frequencies of at least two optical signals among the any three optical signals are within the ZDF region.

5. The method according to any one of claims 1 to 4.

6. The method comprises: performing beam combining on the N pairs of optical signals using N polarization division multiplexers (PDMs) to obtain N beam combined optical signals, the N pairs of optical signals having a one-to-one correspondence with the N PDMs; performing beam combining on the N beam combined optical signals using a wavelength division multiplexer to obtain the wavelength division multiplexed optical signal; 6. The method of claim 1, further comprising:

7. The method of claim 6 , wherein the frequencies of each of the N pairs of optical signals are adjacent.

8. 8. The method of claim 1, wherein N is 2, the polarization configurations of the N pairs of optical signals are XYYX or YXXY, and the spacing between any two adjacent optical signals of the N pairs of optical signals is the same.

9. 9. The method of claim 8, wherein the total transmission rate of the N pairs of optical signals is 400 or 800 gigabits per second (Gb / s).

10. 8. The method of claim 1, wherein N is 4 and the polarization configurations of the N pairs of optical signals are XYYXYXXY, YXXYXYYX, XYYXXYYX, or YXXYYXXY.

11. The method according to claim 10, wherein the total transmission rate of the N pairs of optical signals is 0.8 or 1.6 terabits per second Tb / s.

12. 12. The method according to claim 1, wherein the frequency spacing between adjacent frequencies of the N pairs of optical signals is 400 GHz or 800 GHz.

13. 13. The method according to claim 1, wherein the frequencies of the N pairs of optical signals include two frequencies in a local area network wavelength division multiplexing LAN WDM system, the two frequencies being 229.8 THz and 229 THz, respectively.

14. 14. The method of claim 13, wherein the frequencies of the N pairs of optical signals further include 231.4 THz and 230.6 THz.

15. An optical communication device comprising N polarization division multiplexers (PDM) and a wavelength division multiplexer, the N PDMs are configured to perform beam combining on N pairs of optical signals to obtain N beam-combined optical signals, N being an integer greater than 1, the N pairs of optical signals having a one-to-one correspondence with the N PDMs, each of the N beam-combined optical signals including a first optical signal and a second optical signal having different wavelengths and mutually orthogonal polarizations, and a frequency of at least one of the N first optical signals and at least one of the N second optical signals is within a zero dispersion frequency ZDF region of an optical fiber; the wavelength division multiplexer is configured to perform beam combining on the N beam combined optical signals to obtain a wavelength division multiplexed optical signal, and to transmit the wavelength division multiplexed optical signal through the optical fiber. Optical communication equipment.

16. 16. The apparatus of claim 15, wherein at least two optical signals having different polarizations are included between two adjacent optical signals having the same polarization in the wavelength division multiplexed optical signal.

17. Any four optical signals among the optical signals having the same polarization in the wavelength division multiplexed optical signal satisfy the following conditions: B1+B4-B2-B3=B, where B is not equal to 0, and the four optical signals are sequentially sorted based on frequency values, the frequencies of the four optical signals are B1, B2, B3, and B4, in that order, and the value of (B2+B3) / 2 is within the ZDF region; The apparatus according to claim 16,

18. 18. The apparatus of claim 17, wherein B4-B1=B0, the value of B0 being less than 4.5 THz.

19. 19. The apparatus of claim 15, wherein the frequency spacing of any three of the optical signals having the same polarization in the wavelength division multiplexed optical signal is different, and the frequencies of at least two of the any three optical signals are within the ZDF region.

20. 20. The apparatus of claim 15, wherein the frequencies of each of the N pairs of optical signals are adjacent.

21. 21. An apparatus according to any one of claims 15 to 20, wherein the wavelength division multiplexer is a polarization independent non-polarization maintaining wavelength division multiplexer.

22. 22. The apparatus of claim 15, wherein N is 2, a polarization configuration of the N pairs of optical signals is XYYX or YXXY, and a spacing between any two adjacent optical signals of the N pairs of optical signals is the same.

23. The apparatus of claim 22, wherein a total transmission rate of the N pairs of optical signals is 400 Gb / s or 800 Gb / s.

24. 22. The apparatus of claim 15, wherein N is 4 and the polarization configurations of the N pairs of optical signals are XYYXYXXY, YXXYXYYX, XYYXXYYX, or YXXYYXXY.

25. The apparatus of claim 24, wherein a total transmission rate of the N pairs of optical signals is 0.8 Tb / s or 1.6 Tb / s.

26. 26. The apparatus of claim 15, wherein a frequency spacing between adjacent frequencies of the N pairs of optical signals is 400 GHz or 800 GHz.

27. 27. The apparatus according to claim 15, wherein the frequencies of the N pairs of optical signals include two frequencies in a LAN WDM system, the two frequencies being 229.8 THz and 229 THz, respectively.

28. 28. The apparatus of claim 27, wherein the frequencies of the N pairs of optical signals further include 231.4 THz and 230.6 THz.

29. 1. An optical communication system comprising a transmitting end and a receiving end, the transmitting end being connected to the receiving end through an optical fiber; The transmitting end is configured to transmit a wavelength division multiplexed optical signal to the receiving end through the optical fiber, the wavelength division multiplexed optical signal including N pairs of optical signals, each pair of optical signals including a first optical signal and a second optical signal having different wavelengths and orthogonal polarizations, N is an integer greater than 1, and a frequency of at least one of the N first optical signals and a frequency of at least one of the N second optical signals is within a zero dispersion frequency (ZDF) region of the optical fiber; Optical communication system.

30. 30. The system of claim 29, wherein N is 2, a polarization configuration of the N pairs of optical signals is XYYX or YXXY, and a spacing between any two adjacent optical signals of the N pairs of optical signals is the same.

31. 31. The system of claim 30, wherein a total transmission rate of the N pairs of optical signals is 400 Gb / s or 800 Gb / s.

32. 30. The system of claim 29, wherein N is 4 and the polarization configurations of the N pairs of optical signals are XYYXYXXY, YXXYXYYX, XYYXXYYX, or YXXYYXXY.

33. 33. The system of claim 32, wherein a total transmission rate of the N pairs of optical signals is 0.8 Tb / s or 1.6 Tb / s.

34. 34. The system of claim 29, wherein a frequency spacing between adjacent frequencies of the N pairs of optical signals is 400 GHz or 800 GHz.

35. 35. The system according to claim 29, wherein the frequencies of the N pairs of optical signals include two frequencies in a LAN WDM system, the two frequencies being 229.8 THz and 229 THz, respectively.

36. 36. The system of claim 35, wherein the frequencies of the N pairs of optical signals further include 231.4 THz and 230.6 THz.

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