Optical transmission tail end device, optical transmission head end device and mobile forward transmission system

Abstract

The invention provides an optical transmission tail end device, an optical transmission head end device, an optical transmission system and a mobile forward transmission system. The optical transmission tail end device comprises a first combiner / splitter, a plurality of first optical modules and a first optical path switching module, the plurality of first optical modules are respectively connected with the first combiner / demultiplexer; a first nominal central wavelength of an optical signal received and sent by the first optical module has uniqueness; the first wavelength combiner is connected with the optical transmission head end device through a main optical fiber and a standby optical fiber; the first optical path switching module is used for controlling the first combiner / demultiplexer to transmit the coupling optical signal through the main optical fiber or the standby optical fiber. According to the invention, the influence of four-wave mixing on optical transmission can be avoided, and the transmission performance of optical transmission is ensured; the main and standby optical fibers can be switched, the risk of interruption of service data due to link problems can be reduced, and the service quality is improved.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to an optical transmission tail-end device, an optical transmission head-end device, an optical transmission system and a mobile fronthaul system. Background Art

[0002] With the popularization of 5G mobile systems and the increasing number of base stations, network construction will face problems such as tight fiber resources, long construction period and high cost of new fiber. At present, color optical modules and WDM (Wavelength Division Multiplexing) technology are usually used to solve the problems of tight fiber resources, long construction period and high cost of wireless fronthaul networks. CWDM (Coarse wavelength division multiplexing) technology can be used in WDM fronthaul systems using the O band (wavelength of 1260-1360nm), but the signal quality of optical signals will deteriorate after long-distance transmission. In the WDM fronthaul system using the O-band, technologies such as LWDM (Local Area Network Wavelength Division Multiplexing) can also be used. The central wavelength defined by LWDM technology is located near the zero dispersion point of the optical fiber (wavelength is 1300-1324nm), with low dispersion penalty, and is more suitable for long-distance transmission. However, since the channels of the optical signal are equally spaced and some wavelengths are located in the zero dispersion zone of the optical fiber, four-wave mixing effects will occur in some application scenarios, limiting the transmission capacity. In addition, when the transmission of the optical signal using optical fiber is abnormal, the business data cannot be transmitted normally. Summary of the invention

[0003] In view of this, a technical problem to be solved by the present invention is to provide an optical transmission tail-end device, an optical transmission head-end device, an optical transmission system and a mobile fronthaul system.

[0004] According to a first aspect of the present disclosure, there is provided an optical transmission tail-end device, comprising: a first wavelength combiner / splitter, a plurality of first optical modules and a first optical path switching module; the plurality of first optical modules are respectively connected to the first wavelength combiner / splitter; a first nominal central wavelength of an optical signal received and sent by the first optical module is unique; the first wavelength combiner / splitter is connected to an optical transmission head-end device via a main optical fiber and a backup optical fiber; the first optical path switching module is used to control the first wavelength combiner / splitter to transmit a coupled optical signal via the main optical fiber or the backup optical fiber.

[0005] Optionally, the first optical path switching module is specifically used to control the first combiner / splitter to transmit the coupled optical signal through the main optical fiber when the first optical power value of the coupled optical signal sent by the first combiner / splitter through the main optical fiber and / or the second optical power value of the coupled optical signal received by the first combiner / splitter through the main optical fiber is greater than a power threshold.

[0006] Optionally, the first optical path switching module is specifically configured to control the first combiner / splitter to transmit the coupled optical signal through the backup optical fiber when the first optical power value and / or the second optical power value is less than or equal to a power threshold.

[0007] Optionally, the optical transmission tail-end device includes a first up / down path unit and a third optical module; the first up / down path unit is connected to the third optical module, and is used to extract at least one optical signal from the coupled optical signal sent and / or received by the first combiner / splitter, and send the optical signal to the third optical module.

[0008] Optionally, the first uplink and downlink unit is used to couple the optical signal with the first nominal center wavelength sent by the third optical module with the coupled optical signal sent and / or received by the first combiner / splitter, generate a new coupled optical signal and send it to the optical transmission head-end device and / or the first combiner / splitter.

[0009] Optionally, the first nominal central wavelength includes: an O-band wavelength.

[0010] Optionally, among all the first nominal center wavelengths, a frequency interval between two first nominal center frequencies corresponding to two adjacent first nominal center wavelengths is a first frequency interval value.

[0011] Optionally, the frequency interval of two first nominal center frequencies corresponding to two adjacent uplink first nominal center wavelengths or two adjacent downlink first nominal center wavelengths includes: the first frequency interval value, twice, three times or four times the first frequency interval value; wherein, the uplink first nominal center wavelength is the first nominal center wavelength of the optical signal sent by the first optical module, and the downlink first nominal center wavelength is the first nominal center wavelength of the optical signal received by the first optical module.

[0012] Optionally, the number of the uplink first nominal center wavelength and the downlink first nominal center wavelength includes: six; the first frequency interval value includes: 800 GHz; the maximum value of the first nominal center frequency includes: 236.2 THz.

[0013] Optionally, the first optical module is connected to the first combiner / splitter through an optical fiber, and the first optical module sends and receives optical signals through the one optical fiber; or, the first optical module is connected to the first combiner / splitter through two optical fibers, and the first optical module sends and receives optical signals through the two optical fibers respectively.

[0014] Optionally, the first optical module includes: a WDM optical module.

[0015] According to a second aspect of the present disclosure, there is provided an optical transmission head-end device, comprising: a second wavelength combiner / splitter, a plurality of second optical modules and a second optical path switching module; the plurality of second optical modules are respectively connected to the second wavelength combiner / splitter; the second nominal center wavelength of the optical signal received and sent by the second optical module is unique; the second wavelength combiner / splitter is connected to the optical transmission tail-end device via a main optical fiber and a backup optical fiber; the second optical path switching module is used to control the second wavelength combiner / splitter to transmit the coupled optical signal via the main optical fiber or the backup optical fiber.

[0016] Optionally, the second optical path switching module is specifically used to control the second combiner / splitter to transmit the coupled optical signal through the main optical fiber when the third optical power value of the coupled optical signal sent by the second combiner / splitter through the main optical fiber and / or the fourth optical power value of the coupled optical signal received through the main optical fiber is greater than a power threshold.

[0017] Optionally, the second optical path switching module is specifically used to control the second combiner / splitter to transmit the coupled optical signal through the backup optical fiber when the third optical power value and / or the fourth optical power value is less than or equal to a power threshold.

[0018] Optionally, the optical transmission head-end device includes: a second up / down path unit and a fourth optical module; the second up / down path unit is connected to the fourth optical module, and is used to extract at least one optical signal from the coupled optical signal sent and / or received by the second combiner / splitter, and send the optical signal to the fourth optical module.

[0019] Optionally, the second uplink and downlink unit is used to couple the optical signal with the second nominal center wavelength sent by the fourth optical module with the coupled optical signal sent and / or received by the second combiner / splitter, generate a new coupled optical signal and send it to the optical transmission tail end device and / or the second combiner / splitter.

[0020] Optionally, the second nominal central wavelength includes: an O-band wavelength.

[0021] Optionally, among all the second nominal center wavelengths, a frequency interval between two second nominal center frequencies corresponding to two adjacent second nominal center wavelengths is a second frequency interval value.

[0022] Optionally, the frequency interval of two second nominal center frequencies corresponding to two adjacent uplink second nominal center wavelengths or two adjacent downlink second nominal center wavelengths includes: the second frequency interval value, twice the second frequency interval value, or three times the second frequency interval value; wherein, the uplink second nominal center wavelength is the second nominal center wavelength of the optical signal received by the second optical module, and the downlink second nominal center wavelength is the second nominal center wavelength of the optical signal sent by the second optical module.

[0023] Optionally, the number of the uplink second nominal center wavelength and the downlink second nominal center wavelength includes: six; the second frequency interval value includes: 800 GHz; the maximum value of the first nominal center frequency includes: 236.2 THz.

[0024] Optionally, the second optical module is connected to the second combiner / demultiplexer through an optical fiber, and the second optical module sends and receives optical signals through the one optical fiber; or, the second optical module is connected to the second combiner / demultiplexer through two optical fibers, and the second optical module sends and receives optical signals through the two optical fibers respectively.

[0025] Optionally, the second optical module includes: a WDM optical module.

[0026] According to a third aspect of the present disclosure, there is provided an optical transmission system, comprising: the optical transmission tail-end device as described above, and the optical transmission head-end device as described above; wherein the first nominal center wavelength set is the same as the second nominal center wavelength set; the first nominal center wavelength set is composed of all first nominal center wavelengths, and the second nominal center wavelength set is composed of all second nominal center wavelengths.

[0027] According to a fourth aspect of the present disclosure, a mobile fronthaul system is provided, comprising: the optical transmission system as described above.

[0028] Optionally, the mobile fronthaul system includes: a 4G mobile fronthaul system, a 5G mobile fronthaul system, and a 6G mobile fronthaul system.

[0029] The optical transmission tail-end device, optical transmission head-end device, optical transmission system and mobile fronthaul system disclosed in the present invention, by setting the nominal center wavelength of the optical modules located at the remote end and the local end, make the nominal center wavelength of the optical signals received and sent by the optical modules unique, thereby avoiding the influence of four-wave mixing on optical transmission and ensuring the transmission performance of optical transmission; it can realize the switching of primary and backup optical fibers, reduce the risk of service data interruption due to link problems, and improve service quality; it can realize the add / drop function and the pass-through function; and it improves the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] By describing the embodiments of the present disclosure in more detail in conjunction with the accompanying drawings, the above and other purposes, features and advantages of the present disclosure will become more apparent. The accompanying drawings are used to provide a further understanding of the embodiments of the present disclosure and constitute a part of the specification. Together with the embodiments of the present disclosure, they are used to explain the present disclosure and do not constitute a limitation of the present disclosure. The above and other purposes and advantages of the present disclosure will be further described below in conjunction with specific embodiments and with reference to the accompanying drawings. In the accompanying drawings, the same or corresponding technical features or components will be represented by the same or corresponding figure marks.

[0031] Figure 1 is a schematic diagram of an embodiment of an optical transmission tail end device according to the present disclosure;

[0032] Figure 2 The schematic diagram is a principle diagram of switching between the main and backup optical fibers through the first combiner / demultiplexer;

[0033] Figure 3 is a schematic diagram of another embodiment of the optical transmission tail end device according to the present disclosure;

[0034] Figure 4 is an allocation schematic diagram of another allocation scheme for the uplink and downlink wavelengths of the first optical module;

[0035] Figure 5 A schematic diagram of signal transmission between a first combiner / demultiplexer and a first optical module according to another embodiment of the optical transmission tail end device disclosed in the present invention;

[0036] Figure 6 is a schematic diagram of an embodiment of an optical transmission head-end device according to the present disclosure;

[0037] Figure 7 is a schematic diagram of another embodiment of an optical transmission head-end device according to the present disclosure;

[0038] Figure 8 is an allocation schematic diagram of another allocation scheme for the uplink and downlink wavelengths of the second optical module;

[0039] Fig. 9A schematic diagram of signal transmission between a second combiner / demultiplexer and a second optical module according to another embodiment of the optical transmission head-end device disclosed in the present invention;

[0040] Fig.10 is a schematic diagram of another embodiment of an optical transmission system according to the present disclosure. DETAILED DESCRIPTION

[0041] Exemplary embodiments of the present disclosure will be described below in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of the embodiments are described in the specification. However, it should be understood that many implementation-specific settings must be made in the process of implementing the embodiments in order to achieve the specific goals of the developer, for example, to meet those restrictions related to the device and the service, and these restrictions may vary depending on the implementation. In addition, it should be understood that although the development work may be very complex and time-consuming, it is only a routine task for those skilled in the art who benefit from the content of this disclosure.

[0042] It should be noted that the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure unless specifically stated otherwise.

[0043] Those skilled in the art can understand that the terms "first" and "second" in the embodiments of the present disclosure are only used to distinguish different steps, devices or modules, etc., and neither represent any specific technical meaning nor indicate the necessary logical order between them.

[0044] It should also be understood that in the embodiments of the present disclosure, “plurality” may refer to two or more than two, and “at least one” may refer to one, two, or more than two.

[0045] It should also be understood that any component, data or structure mentioned in the embodiments of the present disclosure can generally be understood as one or more, unless explicitly limited or otherwise indicated in the context.

[0046] In addition, the term "and / or" in the present disclosure is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present disclosure generally indicates that the associated objects before and after are in an "or" relationship.

[0047] It should also be understood that the description of the various embodiments in the present disclosure focuses on the differences between the various embodiments, and the same or similar aspects thereof can be referenced to each other, and for the sake of brevity, they will not be described one by one.

[0048] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0049] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0050] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0051] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0052] In addition, in order to avoid obscuring the present disclosure due to unnecessary details, only the processing steps and / or device structures closely related to at least the scheme according to the present disclosure are shown in the drawings, and other details that are not closely related to the present disclosure are omitted. It should also be noted that similar reference numerals and letters in the drawings indicate similar items, and therefore once an item is defined in one drawing, it does not need to be discussed again for subsequent drawings.

[0053] In the related technologies known to the inventors, the original band is also called the O band, and CWDM technology can be used in the WDM fronthaul system using the O band. Since the wavelength interval used by CWDM technology is relatively wide, no temperature control device is required, and the requirements of industrial-grade temperature (-40°C-85°C) can be met. However, the optical signal will have a problem of deterioration in signal quality after long-distance transmission, and the channel bandwidth of the optical signal cannot meet the fronthaul requirements in some specific scenarios, and the number of channels of the optical signal needs to be expanded.

[0054] In the WDM fronthaul system using the O-band, technologies such as LWDM (Local Area Network Wavelength Division Multiplexing) can also be used. The central wavelength defined by LWDM technology is located near the zero dispersion point of the optical fiber (wavelength is 1300-1324nm), with low dispersion penalty, which is more suitable for long-distance transmission. However, since the optical signal channels used in LWDM technology are equally spaced and the wavelengths of some optical signals are located in the zero dispersion area of ​​the optical fiber, four-wave mixing effects will occur in some application scenarios, limiting the transmission capacity.

[0055] Four-Wave Mixing (FWM) is a kind of optical wave coupling effect produced by the real part of the third-order polarization of the optical fiber medium. Four-Wave Mixing occurs because the light at a certain wavelength in the incident light will change the refractive index of the optical fiber, which will produce a change in the phase of the light wave at a different frequency, thereby generating a light wave of a new wavelength. Due to the interaction of two or three light waves of different wavelengths, the so-called mixing products or new light waves of the sideband are generated at other wavelengths. This interaction may occur between signals in a multi-channel system, and can produce a variety of parametric effects such as triple frequency, sum frequency, and difference frequency, which limits the transmission capacity.

[0056] In one embodiment, Figure 1 As shown, the present disclosure provides an optical transmission tail-end device, which may be a TEE (Tail-End Equipment) device, etc., and may be located at a remote antenna side, etc. The optical transmission tail-end device includes a first combiner / demultiplexer 111 and a plurality of first optical modules, and the number of the plurality of first optical modules may be five, six, etc. The following description assumes that the number of the plurality of first optical modules is six.

[0057] The six first optical modules are respectively a first optical module 121, a first optical module 122, a first optical module 123, a first optical module 124, a first optical module 125 and a first optical module 126. The six first optical modules are respectively connected to the first wavelength combiner / demultiplexer 111, and the first nominal center wavelengths of the optical signals received and sent by the first optical module 121, the first optical module 122, the first optical module 123, the first optical module 124, the first optical module 125 and the first optical module 126 are all unique, that is, the first nominal center wavelengths of the optical signals received and sent by each first optical module are different.

[0058] The first combiner / splitter 111 is a remote combiner / splitter, which can be an existing combiner / splitter. The combiner / splitter is a device composed of a combiner and a splitter. The six first optical modules can be set at the AAU (Active Antenna Unit) side and other positions. The first optical module can be a WDM optical module, etc. The WDM optical module can be a DWDM (Dense Wavelength Division Multiplex) optical module, an LWDM optical module and other optical modules. For example, the LWDM optical module can be a 25Gbit / s LWDM optical module, a 50Gbit / s LWDM optical module and other optical modules. The first optical module can also be a CWDM optical module or other WDM optical module.

[0059] The first wavelength combiner / demultiplexer 111 is connected to the optical transmission head-end device 20 through the main optical fiber 51 and the backup optical fiber 52. The optical transmission head-end device 20 can be a variety of optical transmission head-end devices. The first optical path switching module 31 is used to control the first wavelength combiner / demultiplexer 111 to transmit the coupled optical signal through the main optical fiber 51 or the backup optical fiber 52.

[0060] For example, when the first optical power value of the coupled optical signal sent by the first combiner / demultiplexer 111 through the main optical fiber 51 and the second optical power value of the coupled optical signal received by the first combiner / demultiplexer 111 through the main optical fiber 51 are greater than the power threshold, the first optical path switching module 31 controls the first combiner / demultiplexer 111 to transmit the coupled optical signal through the main optical fiber 51.

[0061] The first optical path switching module 31 controls the first wavelength combiner / demultiplexer 111 to transmit the coupled optical signal through the spare optical fiber 52 when the first optical power value and the second optical power value are less than or equal to the power threshold.

[0062] The first optical path switching module 31 can use a variety of existing methods to detect the first optical power value of the coupled optical signal sent by the first combiner / demultiplexer 111 through the main optical fiber 51 and the second optical power value of the coupled optical signal received through the main optical fiber 51. The power threshold can be set, for example, the power threshold is -30dBm, etc. When the first optical power value and the second optical power value are less than or equal to the power threshold -30dBm, it is determined that the main optical fiber 51 is abnormal, and the main and backup optical fibers are switched, and the first combiner / demultiplexer 111 is controlled to transmit the coupled optical signal through the backup optical fiber 52.

[0063] In one embodiment, the first optical path switching module 31 can use a variety of methods to implement the main and backup optical fiber switching. Figure 2 As shown, a one-to-two optical switch is provided at the common end (trunk end) of the first combiner / demultiplexer 111, and the one-to-two optical switch is respectively connected to the main optical fiber 51 or the backup optical fiber 52. The first optical path switching module 31 controls the one-to-two optical switch to switch the main and backup optical fibers, and controls the first combiner / demultiplexer 11 to transmit the coupled optical signal of the common end of the first combiner / demultiplexer 111 through the main optical fiber 51 or the backup optical fiber 52.

[0064] In one embodiment, Figure 3 As shown, the optical transmission tail end device also includes: a first up / down path unit 61 and a third optical module, and the first up / down path unit 61 is connected to the third optical module. The third optical module can be an LWDM optical module, a CWDM optical module, or other optical modules. The number of third modules can be multiple, and the following takes the number of third modules as two as an example for description.

[0065] The first add / drop unit 61 is connected to the third optical module 711 and the third optical module 712 respectively. The first add / drop unit 61 extracts at least one optical signal from the coupled optical signal sent and received by the first multiplexer / demultiplexer 111 and sends the optical signal to the third optical module 711 and the third optical module 712.

[0066] For example, the first up / down path unit 61 is disposed between the first combiner / demultiplexer 111 and the optical transmission head-end device 20, and is connected to the first combiner / demultiplexer 111 and the optical transmission head-end device 20 respectively through the main optical fiber 51 and the backup optical fiber 52. The first up / down path unit 61 is provided with a combiner / demultiplexer and other devices, and the coupled optical signal sent and received by the first combiner / demultiplexer 111 can be transmitted (transparently transmitted) through the first up / down path unit 61, and the first up / down path unit 61 decouples the coupled optical signal sent and received by the first combiner / demultiplexer 111 through the combiner / demultiplexer, decouples multiple optical signals, and sends one or multiple optical signals to the third optical module 711 and the third optical module 712.

[0067] The first add / drop unit 61 couples the optical signal with the first nominal central wavelength sent by the third optical module 711 and the third optical module 712 with the coupled optical signal sent and / or received by the first combiner / splitter 111, generates a new coupled optical signal and sends it to the optical transmission head-end device and / or the first combiner / splitter.

[0068] For example, the first uplink and downlink unit 61 couples the optical signal with the first nominal central wavelength sent by the third optical module 711 and the third optical module 712 with the coupled optical signal sent and / or received by the first combiner / demultiplexer 111 through a combiner / demultiplexer to generate a new coupled optical signal and send it to the optical transmission head-end device 20 and / or the first combiner / demultiplexer 111.

[0069] In one embodiment, the first nominal center wavelength of the optical signal received and sent by the first optical module 121, the first optical module 122, the first optical module 123, the first optical module 124, the first optical module 125, and the first optical module 126 may be an O-band wavelength, etc. Among all the first nominal center wavelengths, the frequency interval between two first nominal center frequencies corresponding to two adjacent first nominal center wavelengths is a first frequency interval value, and the first frequency interval value may be a plurality of values, for example, the first frequency interval value is 800 GHz, etc.

[0070] In the O band, 12 channels L1-L12 for optical transmission are allocated to the six first optical modules, and the first nominal center wavelength, the first nominal center frequency, etc. are allocated to L1-L12 respectively, and the frequency interval between the two first nominal center frequencies is 800 GHz, wherein 12 continuous O band wavelengths located in the low dispersion region are selected as the optical module center wavelengths. The number of all first nominal center wavelengths is 12, and the allocation table of the 12 first nominal center wavelengths is shown in Table 1 below:

[0071]

[0072]

[0073] Table 1-Nominal center wavelength allocation table

[0074] The maximum value of the first nominal center wavelength is 1269.23nm, and the maximum value of the first nominal center wavelength can also select other values ​​according to needs. The 12 first nominal center wavelengths are the 12 nominal center wavelengths in Table 1; two channels for optical transmission are allocated to each of the six first optical modules, and among all the 12 first nominal center wavelengths, the frequency interval between the two first nominal center frequencies corresponding to the two adjacent first nominal center wavelengths is 800GHz. The first nominal center wavelengths of the six first optical modules are unique, thereby avoiding the influence of four-wave mixing on the transmission performance of the optical transmission tail device and ensuring the optical transmission performance.

[0075] In one embodiment, the uplink direction refers to the direction from the tail end (sending) to the head end (receiving), and the downlink direction refers to the direction from the head end (sending) to the tail end (receiving). An uplink first nominal center wavelength and a downlink first nominal center wavelength are respectively allocated to the six first optical modules, the uplink first nominal center wavelength is the first nominal center wavelength of the optical signal received by the first optical module, and the downlink first nominal center wavelength is the first nominal center wavelength of the optical signal sent by the first optical module. The frequency interval between the two first nominal center frequencies corresponding to the uplink first nominal center wavelength or the downlink first nominal center wavelength with two adjacent wavelengths is the first frequency interval value, twice the first frequency interval value, or three times the first frequency interval value.

[0076] The uplink channels allocated to the six first optical modules and the uplink first nominal central wavelengths are shown in Table 2 below:

[0077]

[0078]

[0079] Table 2 - Allocation of the first nominal central wavelength of the upstream

[0080] The six uplink channels allocated to the six first optical modules are the uplink channels L1, L3, L5, L8, L9, and L11 in Table 2; the six uplink first nominal center wavelengths allocated to the six first optical modules are the six nominal center wavelengths in Table 2.

[0081] The downstream channels allocated to the six first optical modules and the downstream first nominal central wavelengths are shown in Table 3 below:

[0082]

[0083] Table 3 - Allocation of the first nominal central wavelength of the downstream

[0084] The six downlink channels allocated to the six first optical modules are the downlink channels L2, L4, L6, L7, L10, and L12 in Table 3; the six downlink first nominal center wavelengths allocated to the six first optical modules are the six nominal center wavelengths in Table 3.

[0085] As shown in Table 2, the two adjacent uplink first nominal center wavelengths are 1269.23 and 1277.89, and the corresponding two first nominal center frequencies are 236.2 and 234.6. The frequency interval between the two first nominal center frequencies is 1.6 THz, which is twice the first frequency interval value of 0.8 THz.

[0086] The two adjacent uplink first nominal center wavelengths are 1286.66 and 1300.05, and the corresponding two first nominal center frequencies are 233.0 and 230.6. The frequency interval between the two first nominal center frequencies is 2.4 THz, which is three times the first frequency interval value of 0.8 THz.

[0087] The two adjacent uplink first nominal center wavelengths are 1300.05 and 1304.58, and the corresponding two first nominal center frequencies are 230.6 and 229.8. The frequency interval between the two first nominal center frequencies is 0.8 THz, which is the first frequency interval value of 0.8 THz.

[0088] As shown in Table 3, the first nominal center wavelengths of two adjacent downlink wavelengths are 1273.54 and 1282.26, and the corresponding two first nominal center frequencies are 235.4 and 233.8. The frequency interval between the two first nominal center frequencies is 1.6 THz, which is twice the first frequency interval value of 0.8 THz.

[0089] The first nominal center wavelengths of two adjacent downlink wavelengths are 1291.10 and 1295.56, and the corresponding two first nominal center frequencies are 232.2 and 231.4. The frequency interval between the two first nominal center frequencies is 0.8 THz, which is the first frequency interval value of 0.8 THz.

[0090] The two adjacent downlink first nominal center wavelengths are 1295.56 and 1309.14, and the corresponding two first nominal center frequencies are 231.4 and 229.0. The frequency interval between the two first nominal center frequencies is 2.4 THz, which is three times the first frequency interval value of 0.8 THz.

[0091] By defining six uplink and six downlink first nominal central wavelengths for the six first optical modules, the influence of four-wave mixing on the transmission performance of the optical transmission tail-end device can be avoided.

[0092] In one embodiment, there may be multiple allocation schemes for the first nominal central wavelengths of the uplink and downlink of the first optical module. Figure 4 As shown in FIG. 1 , the six uplink channels allocated to the six first optical modules are L1, L3, L5, L9, L10, and L12; the six downlink channels allocated to the six first optical modules are L2, L4, L6, L7, L8, and L11. Figure 4 The first nominal central wavelengths of the six upstream and six downstream signals shown can also avoid the influence of four-wave mixing on the transmission performance of the optical transmission tail-end device.

[0093] In one embodiment, Figure 1 As shown, the first optical module 121, the first optical module 122, the first optical module 123, the first optical module 124, the first optical module 125 and the first optical module 126 are connected to the first combiner / splitter 111 through two optical fibers, and the first optical module 121, the first optical module 122, the first optical module 123, the first optical module 124, the first optical module 125 and the first optical module 126 respectively send and receive optical signals through the two optical fibers.

[0094] The first optical module 121, the first optical module 122, the first optical module 123, the first optical module 124, the first optical module 125, and the first optical module 126 may be dual-fiber bidirectional optical modules, and the sending and receiving interfaces of each first optical module have two pigtails connected to the two branch ports of the first combiner / demultiplexer 111. One or more of the first optical module 121, the first optical module 122, the first optical module 123, the first optical module 124, the first optical module 125, and the first optical module 126 may also be connected to the first combiner / demultiplexer 111 via one optical fiber.

[0095] like Figure 5As shown, the first optical module 131, the first optical module 132, the first optical module 133, the first optical module 134, the first optical module 135 and the first optical module 136 are connected to the first combiner / splitter 111 through an optical fiber, and the first optical module 131, the first optical module 132, the first optical module 133, the first optical module 134, the first optical module 135 and the first optical module 136 respectively send and receive optical signals through an optical fiber.

[0096] The first optical module 131, the first optical module 132, the first optical module 133, the first optical module 134, the first optical module 135 and the first optical module 136 may be single-fiber bidirectional optical modules, and each first optical module has a unique optical interface and a pigtail connected to a branch port of the first combiner / demultiplexer 111. One or more of the first optical module 131, the first optical module 132, the first optical module 133, the first optical module 134, the first optical module 135 and the first optical module 136 may also be connected to the first combiner / demultiplexer using two optical fibers.

[0097] In one embodiment, Figure 6 As shown, the present disclosure provides an optical transmission head-end device, which may be a HEE (Head-End Equipment) device, etc. The optical transmission head-end device may be set in a central machine room, etc. The optical transmission head-end device includes a second combiner / demultiplexer 211 and a plurality of second optical modules, and the number of the plurality of second optical modules may be five, six, etc. The following description is based on the number of the plurality of second optical modules being six.

[0098] The six second optical modules are respectively a second optical module 221, a second optical module 222, a second optical module 223, a second optical module 224, a second optical module 225 and a second optical module 226. The six second optical modules are respectively connected to the second wavelength combiner / demultiplexer 211, and the second nominal center wavelengths of the optical signals received and sent by the second optical module 221, the second optical module 222, the second optical module 223, the second optical module 224, the second optical module 225 and the second optical module 226 are all unique, that is, the second nominal center wavelengths of the optical signals received and sent by each second optical module are fixed and different.

[0099] The second combiner / demultiplexer 211 is a local-end combiner / demultiplexer, which can be an existing combiner / demultiplexer. The combiner / demultiplexer is a device composed of a combiner and a demultiplexer. Six second optical modules can be set at the DU (Distributed Unit) side and other locations. The second optical modules can be WDM optical modules, etc. The WDM optical modules can be DWDM optical modules, LWDM optical modules and other optical modules. For example, the LWDM optical modules can be 25Gbit / s LWDM optical modules, 50Gbit / s LWDM optical modules and other optical modules. The second optical module can also be other WDM optical modules such as CWDM optical modules.

[0100] The second wavelength combiner / demultiplexer 211 is connected to the optical transmission tail-end device 10 through the main optical fiber 51 and the backup optical fiber 52. The optical transmission tail-end device 10 can be a variety of optical transmission head-end devices. The second optical path switching module 41 is used to control the second wavelength combiner / demultiplexer 211 to transmit the coupled optical signal through the main optical fiber 51 or the backup optical fiber 52.

[0101] For example, when the third optical power value of the coupled optical signal sent by the second combiner / demultiplexer 211 through the main optical fiber 51 and the fourth optical power value of the coupled optical signal received by the second combiner / demultiplexer 211 through the main optical fiber 51 are greater than the power threshold, the second optical path switching module 41 controls the second combiner / demultiplexer 211 to transmit the coupled optical signal through the main optical fiber 51.

[0102] When the third optical power value and the fourth optical power value are less than or equal to the power threshold, the second optical path switching module 41 controls the second wavelength combiner / demultiplexer 211 to transmit the coupled optical signal through the spare optical fiber 52 .

[0103] The second optical path switching module 41 can use a variety of existing methods to detect the third optical power value of the coupled optical signal sent by the second combiner / demultiplexer 211 through the main optical fiber 51 and the fourth optical power value of the coupled optical signal received through the main optical fiber 51. The power threshold can be set, for example, the power threshold is -30dBm, etc. When the third optical power value and the fourth optical power value are less than or equal to the power threshold -30dBm, it is determined that the main optical fiber 51 is abnormal, and the main and standby optical fibers are switched, and the second combiner / demultiplexer 211 is controlled to transmit the coupled optical signal through the standby optical fiber 52.

[0104] In one embodiment, the second optical path switching module 41 can use a variety of methods to implement the switching of the main and standby optical fibers. A one-to-two optical switch can be provided at the common end (trunk end) of the second combiner / demultiplexer 211, and the one-to-two optical switch is respectively connected to the main optical fiber 51 or the standby optical fiber 52. The second optical path switching module 41 controls the one-to-two optical switch to switch the main and standby optical fibers, and controls the second combiner / demultiplexer 211 to transmit the coupled optical signal at the common end of the second combiner / demultiplexer 211 through the main optical fiber 51 or the standby optical fiber 52.

[0105] In one embodiment, Figure 7 As shown, the optical transmission head-end device also includes: a second up / down path unit 62 and a fourth optical module, and the second up / down path unit 62 is connected to the fourth optical module. The fourth optical module can be an LWDM optical module, a CWDM optical module, or other optical modules. The number of the fourth modules can be multiple, and the following takes the number of the fourth modules as two as an example for description.

[0106] The second add / drop unit 62 is connected to the fourth optical module 713 and the fourth optical module 714 respectively. The second add / drop unit 62 extracts at least one optical signal from the coupled optical signal sent and received by the second multiplexer / demultiplexer 211 and sends the optical signal to the fourth optical module 713 and the fourth optical module 714.

[0107] For example, the second up / down unit 62 is disposed between the second combiner / demultiplexer 211 and the optical transmission tail-end device 10, and is connected to the second combiner / demultiplexer 211 and the optical transmission tail-end device 10 respectively through the main optical fiber 51 and the backup optical fiber 52. The second up / down unit 62 is provided with a combiner / demultiplexer and other devices, and the coupled optical signal sent and received by the second combiner / demultiplexer 211 can be transmitted (transparently transmitted) through the second up / down unit 62, and the second up / down unit 62 decouples the coupled optical signal sent and received by the second combiner / demultiplexer 211 through the combiner / demultiplexer, decouples multiple optical signals, and sends one or multiple optical signals to the fourth optical module 713 and the fourth optical module 714.

[0108] The first up / down path unit 62 couples the optical signal with the second nominal central wavelength sent by the fourth optical module 713 and the fourth optical module 714 with the coupled optical signal sent and / or received by the second combiner / splitter 211 to generate a new coupled optical signal and send it to the optical transmission tail end device 10 and / or the second combiner / splitter 211.

[0109] For example, the second uplink and downlink unit 62 couples the optical signal with the second nominal central wavelength sent by the fourth optical module 713 and the fourth optical module 714 with the coupled optical signal sent and / or received by the second combiner / splitter 211 through a combiner / splitter to generate a new coupled optical signal and send it to the optical transmission tail-end device 10 and / or the second combiner / splitter 211.

[0110] In one embodiment, the second nominal center wavelength of the optical signal received and sent by the second optical module 221, the second optical module 222, the second optical module 223, the second optical module 224, the second optical module 225, and the second optical module 226 may be an O-band wavelength. Among all the second nominal center wavelengths, the frequency interval between two second nominal center frequencies corresponding to two adjacent second nominal center wavelengths is a second frequency interval value, and the second frequency interval value may be a plurality of values, for example, the second frequency interval value is 800 GHz, etc.

[0111] The six first optical modules are allocated with 12 channels L1-L12 for optical transmission in Table 1; the number of all second nominal center wavelengths is 12, and the 12 second nominal center wavelengths are the 12 nominal center wavelengths in Table 1, and the frequency interval between the two second nominal center frequencies is 800 GHz. The first nominal center wavelength set is the same as the second nominal center wavelength set, the first nominal center wavelength set is composed of all (12) first nominal center wavelengths, and the second nominal center wavelength set is composed of all (12) second nominal center wavelengths.

[0112] In one embodiment, one uplink second nominal center wavelength and one downlink second nominal center wavelength are respectively allocated to the six second optical modules, the uplink second nominal center wavelength is the second nominal center wavelength of the optical signal received by the second optical module, and the downlink second nominal center wavelength is the second nominal center wavelength of the optical signal sent by the second optical module. The frequency interval between two second nominal center frequencies corresponding to two adjacent uplink second nominal center wavelengths or downlink second nominal center wavelengths is the second frequency interval value, twice the second frequency interval value, or three times the second frequency interval value.

[0113] The six uplink channels allocated to the six second optical modules are channels L2, L4, L6, L7, L10, and L12 in Table 1; the six uplink first nominal center wavelengths allocated to the six second optical modules are the six nominal center wavelengths corresponding to channels L2, L4, L6, L7, L10, and L12. The six downlink channels allocated to the six second optical modules are channels L1, L3, L5, L8, L9, and L11 in Table 1; the six downlink second nominal center wavelengths allocated to the six second optical modules are the six nominal center wavelengths corresponding to channels L1, L3, L5, L8, L9, and L11. By setting the second nominal center wavelengths of the six uplinks and six downlinks of the six second optical modules, the influence of four-wave mixing on transmission performance can be avoided.

[0114] In one embodiment, there may be multiple allocation schemes for the uplink and downlink second nominal central wavelengths of the second optical module. Figure 8 As shown in FIG. 1 , the six uplink channels allocated to the six second optical modules are L2, L4, L6, L7, L8, and L11; the six downlink channels allocated to the six second optical modules are L1, L3, L5, L9, L10, and L12. Figure 8 The first nominal central wavelengths of the six upstream and six downstream signals shown can also avoid the influence of four-wave mixing on the transmission performance.

[0115] In one embodiment, Figure 5As shown, the second optical module 221, the second optical module 222, the second optical module 223, the second optical module 224, the second optical module 225 and the second optical module 226 are connected to the second combiner / splitter 211 through two optical fibers, and the second optical module 221, the second optical module 222, the second optical module 223, the second optical module 224, the second optical module 225 and the second optical module 226 respectively send and receive optical signals through the two optical fibers.

[0116] The second optical module 221, the second optical module 222, the second optical module 223, the second optical module 224, the second optical module 225, and the second optical module 226 may be dual-fiber bidirectional optical modules, and the sending and receiving interfaces of each second optical module are connected to the two branch ports of the second combiner / demultiplexer 211 through two pigtail fibers. One or more of the second optical module 221, the second optical module 222, the second optical module 223, the second optical module 224, the second optical module 225, and the second optical module 226 may also be connected to the second combiner / demultiplexer 211 through one optical fiber.

[0117] like Fig. 9 As shown, the second optical module 231, the second optical module 232, the second optical module 233, the second optical module 234, the second optical module 235 and the second optical module 236 are connected to the second combiner / demultiplexer 211 through an optical fiber, and the second optical module 231, the second optical module 232, the second optical module 233, the second optical module 234, the second optical module 235 and the second optical module 236 send and receive optical signals through an optical fiber.

[0118] The second optical module 231, the second optical module 232, the second optical module 233, the second optical module 234, the second optical module 235 and the second optical module 236 are single-fiber bidirectional optical modules, and each second optical module has a unique optical interface and a pigtail connected to a branch port of the second combiner / demultiplexer 211. The use of a single-fiber bidirectional optical module can reduce the use of pigtails and the number of combiner / demultiplexer ports, which is conducive to the improvement of installation and maintenance and link budget. One or more of the second optical module 231, the second optical module 232, the second optical module 233, the second optical module 234, the second optical module 235 and the second optical module 236 can also be connected to the second combiner / demultiplexer using two optical fibers.

[0119] In one embodiment, Fig.10As shown, the present disclosure provides an optical transmission system, including an optical transmission tail-end device and an optical transmission head-end device as in any of the above embodiments, the optical transmission tail-end device is located at the remote end (remote wire side such as AAU side), and the optical transmission head-end device is located at the local end (central machine room and DU side, etc.); wherein, for the first optical path switching module 31 and the second optical path switching module 41, it can be configured to use only one optical path switching module, and the other optical path switching module can be configured to be in a failed state (for backup); for the first uplink and downlink unit 61 and the second uplink and downlink unit 62, it can be configured as one uplink and downlink unit or two uplink and downlink units.

[0120] By setting the nominal central wavelength and wavelength range of the optical modules in the optical transmission tail-end device and the optical transmission head-end device, the influence of four-wave mixing on optical transmission can be avoided, thereby ensuring the transmission performance of optical transmission.

[0121] In one embodiment, the present disclosure provides a mobile fronthaul system, including an optical transmission system as in any of the above embodiments, and the mobile fronthaul system may be a mobile fronthaul system based on LWDM. The mobile fronthaul system is a fronthaul system in a mobile communication system, and the mobile fronthaul system may be a 4G mobile fronthaul system, a 5G mobile fronthaul system, or a 6G mobile fronthaul system. The mobile fronthaul system of the present disclosure performs better in long-distance transmission (e.g., 20km or 40km) and higher-rate optical modules (e.g., 50Gb / s or 100Gb / s). For example, the maximum capacity of the mobile fronthaul system is 150Gbit / s, the nominal bit rate of a single channel is 25Gbit / s, the nominal transmission distance is 10km and 20km, etc.

[0122] The technical solution disclosed in the present invention aims at the problem that wavelengths near the zero dispersion point (1300-1324nm) may cause four-wave mixing effect (i.e., L8-L12), and optimizes the uplink and downlink wavelengths; 0 When the G.652 optical fiber is used, the wavelength channels that generate four-wave mixing are different; through the traversal simulation of different zero dispersion points, it is verified that the asymmetric upstream and downstream wavelengths of the present invention can suppress the influence of four-wave mixing on the system to a certain extent within the required fiber input power range; the cost simulation of four-wave mixing after 10km and 20km G.652 optical fiber transmission is provided, and the simulation results show that the technical solution of the present invention can greatly reduce the risk of four-wave mixing.

[0123] The optical transmission tail-end device, optical transmission head-end device, optical transmission system and mobile fronthaul system in the above-mentioned embodiments, by setting the nominal center wavelength of the optical modules located at the remote end and the local end, make the nominal center wavelength of the optical signals received and sent by the optical modules unique, thereby avoiding the influence of four-wave mixing on optical transmission and ensuring the transmission performance of optical transmission; and, by using a single-fiber bidirectional optical module, the use of pigtails and the number of combiner / splitter ports can be reduced, which is beneficial to installation and maintenance and reduces costs; by setting the main optical fiber and the backup optical fiber, the main and backup optical fiber switching can be realized, which can ensure the normal transmission of the user's business data and improve the service quality; the uplink and downlink functions and the pass-through functions can be realized.

[0124] The basic principles of the present disclosure are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present disclosure are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present disclosure. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, and are not limitations. The above details do not limit the present disclosure to the necessity of adopting the above specific details to be implemented.

[0125] Each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system embodiment, since it basically corresponds to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0126] The block diagrams of the devices, apparatuses, equipment, and systems involved in this disclosure are only illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, apparatuses, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including," "comprising," "having," and the like are open words, referring to "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or," and can be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0127] It should also be noted that in the apparatus, device and method of the present disclosure, each component or each step can be decomposed and / or recombined. Such decomposition and / or recombination should be regarded as equivalent solutions of the present disclosure.

[0128] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present disclosure. Therefore, the present disclosure is not intended to be limited to the aspects shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

[0129] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present disclosure to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, it will be appreciated by those skilled in the art that the above embodiments are merely illustrative and do not limit the scope of the present disclosure. It will be appreciated by those skilled in the art that the above embodiments may be combined, modified or replaced without departing from the scope and essence of the present disclosure.

Claims

1. An optical transmission tail-end device, comprising: A first wave combiner / demultiplexer, a plurality of first optical modules and a first optical path switching module; the plurality of first optical modules are respectively connected to the first wave combiner / demultiplexer; The first nominal central wavelength of the optical signal received and sent by the first optical module is unique; the first wavelength combiner / splitter is connected to the optical transmission head-end device through the main optical fiber and the backup optical fiber; the first optical path switching module is used to control the first wavelength combiner / splitter to transmit the coupled optical signal through the main optical fiber or the backup optical fiber.

2. The device according to claim 1, wherein: The first optical path switching module is specifically used to control the first combiner / splitter to transmit the coupled optical signal through the main optical fiber when the first optical power value of the coupled optical signal sent by the first combiner / splitter through the main optical fiber and / or the second optical power value of the coupled optical signal received by the first combiner / splitter through the main optical fiber is greater than the power threshold.

3. The device as claimed in claim 2, wherein: The first optical path switching module is specifically used to control the first combiner / splitter to transmit the coupled optical signal through the backup optical fiber when the first optical power value and / or the second optical power value is less than or equal to a power threshold.

4. The device according to any one of claims 1 to 3, further comprising: A first add / drop unit and a third optical module; The first add / drop unit is connected to the third optical module, and is used to extract at least one optical signal from the coupled optical signal sent and / or received by the first combiner / demultiplexer, and send the optical signal to the third optical module.

5. The device according to claim 4, wherein: The first up / down path unit is used to couple the optical signal with the first nominal center wavelength sent by the third optical module with the coupled optical signal sent and / or received by the first combiner / splitter, generate a new coupled optical signal and send it to the optical transmission head-end device and / or the first combiner / splitter.

6. The optical transmission tail-end device according to claim 1, wherein: The first nominal central wavelength includes: an O-band wavelength.

7. The optical transmission tail end device according to claim 6, wherein: Among all the first nominal center wavelengths, a frequency interval between two first nominal center frequencies corresponding to two adjacent first nominal center wavelengths is a first frequency interval value.

8. The optical transmission tail-end device according to claim 7, wherein: The frequency interval between two first nominal center frequencies corresponding to two adjacent upstream first nominal center wavelengths or two adjacent downstream first nominal center wavelengths includes: the first frequency interval value, twice, three times or four times the first frequency interval value; The first nominal uplink central wavelength is the first nominal central wavelength of the optical signal sent by the first optical module, and the first nominal downlink central wavelength is the first nominal central wavelength of the optical signal received by the first optical module.

9. The optical transmission tail end device according to claim 8, wherein: The number of the first nominal central wavelength of the upstream and the first nominal central wavelength of the downstream includes: six; The first frequency interval value includes: 800 GHz; The maximum value of the first nominal center frequency includes: 236.2 THz.

10. The optical transmission tail end device according to claim 1, wherein: The first optical module is connected to the first wavelength combiner / demultiplexer via an optical fiber, and the first optical module sends and receives optical signals via the optical fiber, or, The first optical module is connected to the first wavelength combiner / demultiplexer through two optical fibers, and the first optical module sends and receives optical signals through the two optical fibers respectively.

11. The optical transmission tail end device according to claim 1, wherein: The first optical module includes: a WDM optical module.

12. An optical transmission head-end device, comprising: A second wave combiner / demultiplexer, a plurality of second optical modules and a second optical path switching module; the plurality of second optical modules are respectively connected to the second wave combiner / demultiplexer; The second nominal central wavelength of the optical signal received and sent by the second optical module is unique; the second wavelength combiner is connected to the optical transmission tail-end device through the main optical fiber and the backup optical fiber; The second optical path switching module is used to control the second combiner / demultiplexer to transmit the coupled optical signal through the main optical fiber or the backup optical fiber.

13. The device of claim 12, wherein: The second optical path switching module is specifically used to control the second combiner / splitter to transmit the coupled optical signal through the main optical fiber when the third optical power value of the coupled optical signal sent by the second combiner / splitter through the main optical fiber and / or the fourth optical power value of the coupled optical signal received through the main optical fiber is greater than the power threshold.

14. The device of claim 13, wherein: The second optical path switching module is specifically used to control the second combiner / splitter to transmit the coupled optical signal through the spare optical fiber when the third optical power value and / or the fourth optical power value is less than or equal to the power threshold.

15. The device according to any one of claims 12 to 14, further comprising: A second add / drop unit and a fourth optical module; The second add / drop unit is connected to the fourth optical module, and is used to extract at least one optical signal from the coupled optical signal sent and / or received by the second combiner / demultiplexer, and send the optical signal to the fourth optical module.

16. The device of claim 15, wherein: The second up / down path unit is used to couple the optical signal with the second nominal center wavelength sent by the fourth optical module with the coupled optical signal sent and / or received by the second combiner / splitter, generate a new coupled optical signal and send it to the optical transmission tail end device and / or the second combiner / splitter.

17. The optical transmission head-end device according to claim 12, wherein: The second nominal central wavelength includes: an O-band wavelength.

18. The optical transmission head-end device according to claim 17, wherein: Among all the second nominal center wavelengths, the frequency interval between two second nominal center frequencies corresponding to two adjacent second nominal center wavelengths is a second frequency interval value.

19. The optical transmission head-end device according to claim 18, wherein: The frequency interval between two second nominal center frequencies corresponding to two adjacent upstream second nominal center wavelengths or two adjacent downstream second nominal center wavelengths includes: the second frequency interval value, twice the second frequency interval value, or three times the second frequency interval value; The uplink second nominal central wavelength is the second nominal central wavelength of the optical signal received by the second optical module, and the downlink second nominal central wavelength is the second nominal central wavelength of the optical signal sent by the second optical module.

20. The optical transmission head-end device according to claim 19, wherein: The number of the uplink second nominal central wavelength and the downlink second nominal central wavelength includes: six; The second frequency interval value includes: 800 GHz; The maximum value of the first nominal center frequency includes: 236.2 THz.

21. The optical transmission head-end device according to claim 12, wherein: The second optical module is connected to the second wavelength combiner / demultiplexer via an optical fiber, and the second optical module sends and receives optical signals via the optical fiber; or, The second optical module is connected to the second wavelength combiner / demultiplexer through two optical fibers, and the second optical module sends and receives optical signals through the two optical fibers respectively.

22. The optical transmission head-end device according to claim 12, wherein: The second optical module includes: a WDM optical module.

23. An optical transmission system, comprising: The optical transmission tail-end device according to any one of claims 1 to 11, the optical transmission head-end device according to any one of claims 12 to 22; The first nominal central wavelength set is the same as the second nominal central wavelength set; the first nominal central wavelength set consists of all first nominal central wavelengths, and the second nominal central wavelength set consists of all second nominal central wavelengths.

24. A mobile fronthaul system, comprising: The optical transmission system as claimed in claim 23.

25. The mobile fronthaul system according to claim 24, wherein: The mobile fronthaul system includes: 4G mobile fronthaul system, 5G mobile fronthaul system, and 6G mobile fronthaul system.

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