A crosstalk prevention optimization configuration method based on circulator forward transmission system

Abstract

The present invention discloses an anti-crosstalk optimization configuration method based on a circulator fronthaul system, which relates to the field of optical communication technology. The method comprises: controlling the deviation of the central wavelengths of corresponding transmitted optical signals on the AAU side and the DU side to be at least 0.4 nm, so that the evaluation threshold of the reflection equivalent influence factor under predetermined conditions becomes smaller than the original evaluation threshold; or, according to the reflection equivalent influence factor, adjusting the power difference of the corresponding transmitted optical signals on the AAU side and the DU side, the larger the power difference is, the smaller the influence of the reflected optical signal on the circulator fronthaul system is; both methods can improve the tolerance of the circulator fronthaul system to the influence of line reflection crosstalk.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to an anti-crosstalk optimization configuration method based on a circulator fronthaul system. Background Art

[0002] Limited by optical fiber resources, the 5G fronthaul bearer solution mainly adopts wavelength division multiplexing technology. At present, the wavelength division scheme in the fronthaul system is mainly implemented based on CWDM. In order to expand the capacity of the 5G fronthaul system, the characteristics of the mutually different conduction of the circulator ports are generally used to realize bidirectional transmission of the same wavelength in a single optical fiber. The single-fiber bidirectional system based on the circulator solution is relatively common in the field of optical communications. The corporate standard "Q / CT 2692-2021" of China Telecom Group Co., Ltd. has relevant indicator definitions for the circulator-based fronthaul solution. The current specific implementation method of the 5G fronthaul system based on the circulator solution is generally placed in the multiplexer to meet the corporate standards of China Telecom.

[0003] This solution can achieve double capacity transmission in a single fiber without changing the wavelength of the optical module, and can be used for other wavelengths besides CWDM. However, the characteristics of the circulator ports being mutually different also bring risks, such as Figure 1 As shown in the figure, the three ports of circulator 1 are Port1, Port2, and Port3. When the same wavelength single fiber is bidirectionally transmitted, the local transmission signal is conducted from port1 to port2, and the opposite transmission signal is conducted from port2 to port3. When there is a reflection point in the transmission line, the local transmission signal is reflected by each reflection point and then superimposed together, and then conducted from port2 to port3. That is, the reflected signal of the local transmission signal and the opposite transmission signal are mixed together at port3 to form crosstalk noise, which the local receiver cannot distinguish, causing system failure.

[0004] For the fronthaul system based on the circulator solution, how to reduce the impact of reflection crosstalk in the transmission line, so as to solve the potential system failure problem caused by it, no relevant solution is given in the currently known technologies. Summary of the invention

[0005] In response to the above-mentioned problems and technical requirements, the inventors have proposed an anti-crosstalk optimization configuration method based on a circulator fronthaul system. Through a series of optimization configuration schemes, the impact of reflected light signals superimposed by joints and fusion points at different positions on signal transmission is reduced, and the line's tolerance to reflection crosstalk is increased.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect, the present application provides an anti-crosstalk optimization configuration method based on a circulator fronthaul system, comprising the following steps:

[0008] In a circulator-based fronthaul system, the optical signal wavelengths output from the respective signal transmitting ends of the optical module on the AAU side correspond to the optical signal wavelengths output from the respective signal transmitting ends of the optical module on the DU side;

[0009] By controlling the deviation of the central wavelengths of the corresponding transmitted optical signals on the AAU side and the DU side to be at least 0.4 nm or more, the evaluation threshold of the reflection equivalent impact factor under predetermined conditions becomes smaller compared to the original evaluation threshold, thereby improving the tolerance of the circulator-based fronthaul system to the impact of line reflection crosstalk;

[0010] Among them, the reflection equivalent impact factor is used to evaluate the impact of line reflection crosstalk, and is defined as the power difference between the power of the transmitted optical signal from the opposite end reaching the receiving end of this end and the power of the reflected optical signal of the corresponding transmitted optical signal of this end reaching the receiving end of this end; if the AAU side or the DU side is this end, then the other side is the opposite end.

[0011] A further technical solution thereof is that the evaluation threshold of the reflection equivalent impact factor under predetermined conditions becomes smaller compared to the original evaluation threshold, including:

[0012] For a 5G fronthaul system based on a circulator, under the predetermined conditions that the rate of each channel of the system is 25 Gbps, BER <= 5E-5, and the transmitted optical signal from the opposite end meets the sensitivity of the receiver of this end:

[0013] When the central wavelengths of the corresponding transmitted optical signals on the AAU side and the DU side are the same, the original evaluation threshold is 23; if ΔBn > 23, then the reflected optical signal has no impact on the circulator-based fronthaul system, and the impact of reflection crosstalk in the transmission line is ignored during evaluation;

[0014] When the deviation of the central wavelengths of the corresponding transmitted optical signals on the AAU side and the DU side is 0.4 nm, the evaluation threshold drops to 10, then ΔBn > 10 can ignore the impact of reflection crosstalk in the transmission line;

[0015] Among them, ΔBn is the reflection equivalent impact factor obtained at the receiving end of the nth signal of this end.

[0016] A further technical solution thereof is that the method further includes:

[0017] Using bevel connectors for the connectors in the transmission line, as well as the multiplexers and circulators on the AAU side and the DU side, to suppress the reflected optical signal from returning to the receiving end of this end along the line.

[0018] In a second aspect, the present application also provides an anti-crosstalk optimization configuration method for a circulator-based fronthaul system, including the following steps:

[0019] In a circulator-based fronthaul system, the optical signal wavelengths output from the respective signal transmitting ends of the optical module on the AAU side correspond to the optical signal wavelengths output from the respective signal transmitting ends of the optical module on the DU side;

[0020] According to the reflection equivalent influence factor, adjust the power difference between the corresponding transmitted optical signals on the AAU side and the DU side. The greater the power difference, the smaller the influence of the reflected optical signal of the local transmitted optical signal on the circulator-based fronthaul system, thereby improving the tolerance of the circulator-based fronthaul system to the influence of line reflection crosstalk;

[0021] Among them, the reflection equivalent influence factor is used to evaluate the influence of line reflection crosstalk, and is defined as the power difference between the power of the transmitted optical signal from the opposite end reaching the local receiving end and the power of the reflected optical signal of the corresponding local transmitted optical signal reaching the local receiving end; if the AAU side or the DU side is the local end, the other side is the opposite end.

[0022] Its further technical solution is to adjust the power difference between the corresponding transmitted optical signals on the AAU side and the DU side according to the reflection equivalent influence factor, including:

[0023] If the DU side is the local end and the AAU side is the opposite end, control any pair of signal transmitting ends of the optical modules on the AAU side and the DU side to transmit signals in turn. The reflection equivalent influence factor obtained at the nth local signal receiving end corresponding to the wavelength is denoted as ΔBn, and ΔBn = RBn_1 - RBn_2, where RBn_1 is the power of the nth transmitted optical signal from the opposite end reaching the local receiving end measured through the transmission line, and RBn_2 is the power of the reflected optical signal generated by the nth local transmitted optical signal reaching the local receiving end measured through the transmission line;

[0024] When considering system loss and line reflection equivalent coefficient:

[0025] RBn_1 = TAn - MUX_AAU - Line_loss - MUX_DU;

[0026] RBn_2 = TBn - MUX_DU - ΔBRn - MUX_DU;

[0027] Then ΔBn = RBn_1 - RBn_2 = (TAn - TBn) - (Line_loss - ΔBRn) > M;

[0028] Among them, TAn is the power of the nth transmitted optical signal from the opposite end, TBn is the power of the nth local transmitted optical signal; MUX_AAU and MUX_DU are the losses of the multiplexers on the AAU side and the DU side respectively, and it is assumed that the loss values on both sides are the same; Line_loss is the transmission line loss; ΔBRn is the line reflection equivalent coefficient of channel n, and when the transmission line and the connection remain unchanged, ΔBRn is a fixed value; M is the evaluation threshold under predetermined conditions.

[0029] Its further technical solution is that the method further comprises:

[0030] According to the reflection equivalent impact factor, the transmission line loss is adjusted. The smaller the loss, the smaller the impact of the reflected optical signal on the circulator-based fronthaul system, thereby improving the tolerance of the circulator-based fronthaul system to the impact of line reflection crosstalk.

[0031] Its further technical solution is that the method further comprises:

[0032] When the AAU side or the DU side is used as the local side, the reflection equivalent impact factor obtained by the receiving end is obtained;

[0033] If the two are different, the step of adjusting the power difference of the corresponding transmitted optical signals on the AAU side and the DU side according to the reflection equivalent influence factor is performed.

[0034] Its further technical solution is that the method further comprises:

[0035] The connectors in the transmission line, as well as the connectors of the multiplexer and circulator on the AAU and DU sides, are all equipped with bevel connectors to suppress the reflected optical signal from returning to the local receiving end along the line.

[0036] The beneficial technical effects of the present invention are:

[0037] For the circulator-based fronthaul system, by adjusting the central wavelength deviation of the corresponding transmitted optical signals on the AAU side and the DU side to at least 0.4nm and increasing the power difference of the corresponding transmitted optical signals on the AAU side and the DU side, the influence of the reflected optical signals superimposed by the joints and welding points at different positions in the line on the signal transmission can be effectively reduced, and the tolerance of the fronthaul system to the influence of reflection crosstalk can be greatly improved; by adjusting the central wavelength deviation, the evaluation threshold of the reflection equivalent impact factor is reduced from 23dB to 10dB or even lower; by using bevel connectors in conjunction with the system connectors, the system requirements for line quality are reduced, effectively solving the reflection problems that may exist in the old lines in the 5G fronthaul system. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the reciprocity of the circulator ports.

[0039] Figure 2 This is a schematic diagram of the fronthaul system based on the circulator solution.

[0040] Figure 3 This is a flow chart of the anti-crosstalk optimization configuration method based on the circulator fronthaul system provided in this application. DETAILED DESCRIPTION

[0041] The following further describes the specific implementation manners of the present invention in conjunction with the accompanying drawings.

[0042] The crosstalk prevention and optimization configuration method provided in this application is applied to Figure 2 the typical fronthaul system based on the circulator solution shown in the figure. Among them, the multiplexers MUX1 to MUX4 are used for wavelength multiplexing and demultiplexing, and can be considered the same. The optical signal wavelengths output from the respective signal transmitting ends of the optical modules on the active antenna unit (AAU) side correspond to the optical signal wavelengths output from the respective signal transmitting ends of the optical modules on the distribution unit (DU) side, that is, TA1 corresponds to TB1, TA2 corresponds to TB2... TAn corresponds to TBn. The wavelengths between TA1 to TAn and between TB1 to TBn are different, and the wavelength accuracy is within the requirements of the fronthaul system specification. The channel bandwidths of the multiplexers can cover the transmitted optical signal wavelengths. Taking the CWDM system as an example, within the full temperature range, its signal wavelength range is ITU wavelength + / - 6.5 nm. At the same temperature, the wavelength deviation of the optical module is small; the wavelength of the MUX transmission end is required to satisfy > ITU + / - 6.5 nm. For the above fronthaul system, this application uses three embodiments to separately explain the proposed crosstalk prevention and optimization configuration method.

[0043] Embodiment 1:

[0044] In conjunction with Figure 2 、 Figure 3 shown in the figure, a crosstalk prevention and optimization configuration method for a fronthaul system based on a circulator, the method includes:

[0045] Control the deviation of the central wavelengths of the corresponding transmitted optical signals on the AAU side and the DU side to be at least 0.4 nm or more, then the evaluation threshold of the reflection equivalent impact factor under the predetermined conditions becomes smaller compared with the original evaluation threshold, thereby improving the tolerance of the fronthaul system based on the circulator to the influence of line reflection crosstalk.

[0046] Among them, the reflection equivalent impact factor is used to evaluate the influence of line reflection crosstalk, and is defined as the power difference between the optical signal of the opposite-end transmitted optical signal reaching the local receiving end and the reflected optical signal of the corresponding local transmitted optical signal reaching the local receiving end; if the AAU side or the DU side is the local end, then the other side is the opposite end.

[0047] Specifically, the evaluation threshold of the reflection equivalent impact factor under the predetermined conditions becomes smaller compared with the original evaluation threshold, including:

[0048] For the 5G fronthaul system based on the circulator, under the predetermined conditions that the rate of each channel of the system is 25 Gbps, BER <= 5E-5, and the opposite-end transmitted optical signal meets the sensitivity of the local receiver:

[0049] 1) When the central wavelengths of the corresponding transmitted optical signals (TAn and TBn) on the AAU side and the DU side are the same, the original evaluation threshold is 23; if ΔBn > 23, the reflected optical signals superimposed at different positions in the line have no impact on the circulator-based fronthaul system, and the reflected crosstalk impact in the transmission line can be ignored during evaluation.

[0050] 2) When the deviation of the central wavelengths of the corresponding transmitted optical signals (TAn and TBn) on the AAU side and the DU side is 0.4 nm, the evaluation threshold drops to 10, and then ΔBn > 10 can ignore the reflected crosstalk impact in the transmission line.

[0051] Among them, ΔBn is the reflection equivalent impact factor obtained at the receiving end of the nth local signal.

[0052] As Figure 2 shown, taking TA1 and TB1 as an example, the light sources of TA1 and TB1 are the same. Taking the CWDM wavelength as an example for illustration, TA1 and TB1 are set to 1271 + / - 6.5 nm. From the above analysis, it can be seen that when evaluating the impact of ΔB1 on the system when the central wavelengths are exactly the same, it is necessary to ensure that ΔB1 > 23. However, the applicant found during the experiment that when the deviation of the central wavelengths of TA1 and TB1 is more than 0.4 nm, the impact of ΔB1 on the system is greatly reduced, and ΔB1 > 10 can ensure the system performance. Therefore, as long as the deviation of the central wavelengths of TAn and TBn is controlled to be more than 0.4 nm, the tolerance of the circulator-based fronthaul system to line reflections can be reduced from 23 dB to 10 dB or even lower.

[0053] For another example, taking the MWDM system as an example for illustration, the wavelength requirement of one channel is 1374.5 + / - 2.5 nm, and the MUX wavelength matches it. Controlling the wavelength of TA1 to be 1375.5 + / - 0.5 nm and the wavelength of TB1 to be 1374 nm + / - 0.5 nm, the wavelength difference between TA1 and TB1 can always be maintained above 0.5 nm. At this time, the impact factors of the reflected optical signals superimposed at different positions in the line, such as joints and fusion splices, and the transmitted optical signals from the opposite end on the system transmission can be greatly reduced to below 10 dB.

[0054] It should be noted that the method of controlling the deviation of the central wavelengths of the corresponding transmitted optical signals on both sides can adopt the commonly used TEC control temperature control method, ambient temperature control, etc. in the art to make the central wavelength of the optical module "deliberately" deviate from the standard central wavelength. The above control method is not the inventive point of this application, so it will not be introduced in detail.

[0055] Embodiment 2:

[0056] Combined with Figure 2 、 Figure 3 shown, a crosstalk prevention and optimization configuration method for a circulator-based fronthaul system, the method includes:

[0057] Step 1: Obtain the reflection equivalent impact factor obtained by the receiving end when the AAU side or the DU side is used as the local end respectively. If the reflection equivalent impact factors on both sides are different, for example, when the deviation is greater than 5 dB, go to Step 2. Otherwise, it is impossible to reduce the impact of line reflection on the system by adjusting the power difference between the corresponding transmitted optical signals on both sides.

[0058] Step 2: Adjust the power difference between the corresponding transmitted optical signals on the AAU side and the DU side according to the reflection equivalent impact factor. If the power value of the local transmitted optical signal is less than the power value of the opposite transmitted optical signal (that is, the obtained power difference is positive), when the reflection equivalent impact factor of the opposite end meets the evaluation threshold, the greater the power difference between the transmitted powers of the opposite end and the local end, the smaller the impact of the reflected optical signal of the local transmitted signal on the circulator-based fronthaul system, thereby improving the tolerance of the circulator-based fronthaul system to the impact of line reflection crosstalk.

[0059] And / or, adjust the size of the transmission line loss according to the reflection equivalent impact factor. The smaller the loss, the smaller the impact of the reflected optical signal on the circulator-based fronthaul system, thereby improving the tolerance of the circulator-based fronthaul system to the impact of line reflection crosstalk.

[0060] Among them, the reflection equivalent impact factor is used to evaluate the impact of line reflection crosstalk, and is defined as the power difference between the power of the transmitted optical signal of the opposite end reaching the receiving end of the local end and the power of the reflected optical signal of the corresponding local transmitted optical signal reaching the receiving end of the local end; if the AAU side or the DU side is the local end, the other side is the opposite end.

[0061] Specifically, adjusting the power difference between the corresponding transmitted optical signals on the AAU side and the DU side according to the reflection equivalent impact factor includes:

[0062] If the DU side is the local end and the AAU side is the peer end, any pair of signal transmitting ends of the optical modules on the AAU side and the DU side are sequentially controlled to transmit signals (such as TA1 and TB1). The reflection equivalent influence factor obtained at the local signal receiving end RB1 corresponding to the wavelength is denoted as ΔB1, and ΔB1 = RB1_1 - RB1_2. Wherein: RB1_1 is the power of the transmitted optical signal TA1 from the peer end reaching the local receiving end via the transmission line, that is, after TA1 is multiplexed by MUX3, it enters the transmission line through the circulator 2, passes through the ODF (Optical Distribution Frame), transmission optical fiber, connector loss, and splicing loss, and then enters the local end through Port2 of the circulator 1 and is conducted to Port3, and reaches RB1 after being demultiplexed by MUX2. RBn_2 is the power of the reflected optical signal generated by the local transmitted optical signal TB1 reaching the local receiving end via the transmission line, that is, after TB1 is multiplexed by MUX1, it enters the transmission line through the circulator 1, and is reflected by flange joints at different positions, splicing points at different positions, and end faces suspended (or in poor contact) at different positions during the passage of the line. The reflection values of these may vary greatly, but all are transmitted in the AAU→DU direction, enter the local end through Port2 of the circulator 1 and are conducted to Port3, and reach RB1 after being demultiplexed by MUX2.

[0063] Optionally, RB1_1 and RB1_2 can be measured by connecting a power test device to the RB1 end of MUX2 at the local end. For example, when TB1 is turned off and TA1 is turned on, RB1_1 is measured; when TB1 is turned on and TA1 is turned off, RB1_2 is measured.

[0064] When considering the system loss and the line reflection equivalent coefficient:

[0065] RB1_1 = TA1 - MUX_AAU - Line_loss - MUX_DU (1)

[0066] RB1_2 = TB1 - MUX_DU - ΔBR1 - MUX_DU (2)

[0067] Then ΔB1 = RB1_1 - RB1_2 = (TA1 - TB1) - (Line_loss - ΔBR1) > M (3)

[0068] Wherein, MUX_AAU and MUX_DU are the losses of the multiplexers on the AAU side and the DU side respectively, and it is assumed that the loss values on both sides are the same; Line_loss is the transmission line loss; ΔBR1 is the line reflection equivalent coefficient of channel 1 (unit: dB), and when the transmission line and the connection remain unchanged, ΔBR1 is a fixed value; M is the evaluation threshold under the predetermined conditions. Referring to the predetermined conditions given in Embodiment 1, M = 23 or other values.

[0069] For a single-fiber bidirectional fronthaul system, reflection has a certain directionality. When it is along one direction, the corresponding M is fixed and unchanged. As shown in formula (3), the larger (TA1-TB1), the smaller the impact of line reflection crosstalk on the system (1:1 linear change). Different transmission line losses Line_loss have different tolerances for line reflection. The smaller Line_loss, the smaller the impact of line reflection crosstalk on the system, and the higher the system tolerance. Therefore, it is necessary to pay attention to the line loss to ensure that it is within a reasonable range.

[0070] Embodiment three:

[0071] like Figure 3 As shown, a crosstalk prevention optimization configuration method based on a circulator fronthaul system, the method comprising:

[0072] The connectors in the transmission line, as well as the connectors of the multiplexers MUX1 to MUX4 and the circulator on the AAU side and the DU side, are all made of bevel connectors to suppress the reflected optical signal from returning to the local receiving end along the line.

[0073] Optionally, bevel connectors are available in 8° APC type.

[0074] In order to significantly improve the system's anti-reflection crosstalk impact, the method provided in the third embodiment can be used together with the first and second embodiments to achieve better results.

[0075] The above is only a preferred embodiment of the present application, and the present invention is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. An anti-crosstalk optimization configuration method based on circulator forward transmission system, It is characterized in that The method comprises: In the circulator-based fronthaul system, the wavelength of the optical signal output by each signal transmitting end of the optical module at the AAU side corresponds to the wavelength of the optical signal output by each signal transmitting end of the optical module at the DU side; By controlling the deviation of the central wavelengths of the corresponding transmitted optical signals on the AAU side and the DU side to be at least 0.4 nm, the evaluation threshold of the reflection equivalent impact factor under the predetermined conditions becomes smaller than the original evaluation threshold, thereby improving the tolerance of the circulator-based fronthaul system to the influence of line reflection crosstalk; The reflection equivalent impact factor is used to evaluate the line reflection crosstalk impact, which is defined as the power difference between the power of the optical signal transmitted by the other end reaching the receiving end of the local end and the power of the reflected optical signal of the corresponding optical signal transmitted by the local end reaching the receiving end of the local end; the AAU side or the DU side is the local end, and the other side is the opposite end; The evaluation threshold of the reflection equivalent impact factor under the predetermined conditions becomes smaller than the original evaluation threshold, including: For a 5G fronthaul system based on a circulator, under the conditions that the rate of each channel of the system is 25 Gbps, the bit error rate BER <= 5E-5, and the optical signal transmitted by the opposite end meets the predetermined sensitivity of the local receiver: When the central wavelengths of the corresponding transmitted optical signals on the AAU side and the DU side are the same, the original evaluation threshold is 23; if ΔBn>23, the reflected optical signal has no effect on the circulator-based fronthaul system, and the reflection crosstalk effect in the transmission line is ignored during the evaluation; When the deviation of the central wavelengths of the corresponding transmitted optical signals on the AAU side and the DU side is 0.4 nm, the evaluation threshold is reduced to 10, and ΔBn>10 can ignore the reflection crosstalk effect in the transmission line; Wherein, ΔBn is the reflection equivalent impact factor obtained at the nth local signal receiving end.

2. According to claim 1, the anti-crosstalk optimization configuration method based on the circulator forward transmission system, It is characterized in that The method further comprises: The connectors in the transmission line, as well as the connectors of the multiplexer and circulator on the AAU side and the DU side, are all bevel connectors, which are used to suppress the reflected optical signal from returning to the local receiving end along the line. 3.An anti-crosstalk optimization configuration method based on circulator forward transmission system, It is characterized in that The method comprises: In the circulator-based fronthaul system, the wavelength of the optical signal output by each signal transmitting end of the optical module at the AAU side corresponds to the wavelength of the optical signal output by each signal transmitting end of the optical module at the DU side; According to the reflection equivalent impact factor, the power difference of the corresponding transmitted optical signals on the AAU side and the DU side is adjusted. The larger the power difference is, the smaller the impact of the reflected optical signal of the optical signal transmitted at the local end on the circulator-based fronthaul system is, thereby improving the tolerance of the circulator-based fronthaul system to the impact of line reflection crosstalk; Among them, the reflection equivalent impact factor is used to evaluate the impact of line reflection crosstalk, and is defined as the power difference between the power of the optical signal transmitted from the opposite end reaching the receiving end of the local end and the power of the reflected optical signal of the corresponding optical signal transmitted from the local end reaching the receiving end of the local end; if the AAU side or the DU side is the local end, then the other side is the opposite end; Among them, adjusting the power difference between the corresponding transmitted optical signals on the AAU side and the DU side according to the reflection equivalent impact factor includes: If the DU side is used as the local end and the AAU side is used as the opposite end, control any pair of signal transmitting ends of the optical modules on the AAU side and the DU side to transmit signals in sequence. The reflection equivalent impact factor obtained at the nth local signal receiving end corresponding to the wavelength is denoted as ΔBn, and ΔBn = RBn_1 - RBn_2, where RBn_1 is the power of the nth transmitted optical signal from the opposite end reaching the receiving end of the local end measured through the transmission line, and RBn_2 is the power of the reflected optical signal generated by the nth transmitted optical signal from the local end reaching the receiving end of the local end measured through the transmission line; When considering system loss and line reflection equivalent coefficient: RBn_1 = TAn - MUX_AAU - Line_loss - MUX_DU; RBn_2 = TBn - MUX_DU - ΔBRn - MUX_DU; Then ΔBn = RBn_1 - RBn_2 = (TAn - TBn) - (Line_loss - ΔBRn) > M; Among them, TAn is the power of the nth transmitted optical signal from the opposite end, TBn is the power of the nth transmitted optical signal from the local end; MUX_AAU and MUX_DU are the losses of the multiplexers on the AAU side and the DU side respectively, and it is assumed that the loss values on both sides are the same; Line_loss is the transmission line loss; ΔBRn is the line reflection equivalent coefficient of channel n, and when the transmission line and the connection remain unchanged, ΔBRn is a fixed value; M is the evaluation threshold under predetermined conditions.

4. The anti-crosstalk optimization configuration method for a circulator-based fronthaul system according to claim 3, characterized in that the method further includes: According to the reflection equivalent impact factor, adjust the magnitude of the transmission line loss. The smaller the loss, the smaller the impact of the reflected optical signal on the circulator-based fronthaul system, thereby improving the tolerance of the circulator-based fronthaul system to the impact of line reflection crosstalk.

5. The anti-crosstalk optimization configuration method for a circulator-based fronthaul system according to claim 3 or 4, characterized in that the method further includes: Respectively obtain the reflection equivalent impact factors obtained at the receiving end when the AAU side or the DU side is used as the local end; If they are different, then perform the step of adjusting the power difference between the corresponding transmitted optical signals on the AAU side and the DU side according to the reflection equivalent impact factor.

6. The anti-crosstalk optimization configuration method for a circulator-based fronthaul system according to claim 3 or 4, characterized in that the method further includes: Use bevel connectors for the connectors in the transmission line, as well as the connectors of the multiplexers and circulators on the AAU side and the DU side, to suppress the reflected optical signal from returning to the receiving end of the local end along the line.

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