Bidirectional fiber optic transmission system

Abstract

The present application relates to the field of optical fiber transmission technology and discloses a bidirectional optical fiber transmission system, including a first wavelength division multiplexer / demultiplexer, a second wavelength division multiplexer / demultiplexer, a first power amplifier, a second power amplifier, a first preamplifier, a second preamplifier, a first optical fiber switching module, a second optical fiber switching module, a first filter, a second filter, a third filter and a fourth filter; the first optical fiber switching module and the second optical fiber switching module are configured to transmit optical signals via a first optical fiber or a second optical fiber; the present technical solution supports automatic switching to a backup optical fiber link when a single optical fiber link fails or its performance degrades, and also implements the splitting and combining of band signals through filters to ensure the stability and anti-interference capability of the transmitted signal.

Description

Technical Field

[0001] The present invention relates to the field of optical transmission technology, and in particular to a bidirectional optical fiber transmission system. Background Art

[0002] With the rapid development of optical communication technology, wavelength division multiplexing (WDM) has been widely used in modern fiber-optic communication systems. By simultaneously transmitting multiple optical signals of different wavelengths through the same optical fiber, WDM significantly increases optical fiber transmission capacity and spectrum efficiency, making it suitable for long-distance and high-capacity communication scenarios. Existing bidirectional fiber-optic communication systems typically use two separate optical fibers for transmitting and receiving optical signals to ensure signal stability and prevent mutual interference. However, dual-fiber deployment has certain disadvantages in terms of cost, maintenance, and construction space. For example, re-laying two optical fibers in some constrained environments (such as the seabed, underground pipelines, or existing infrastructure) is difficult. In cost-sensitive or cabling-constrained scenarios, a single optical fiber is preferred for bidirectional transmission. However, fiber link failures, attenuation, or interruptions can still occur, resulting in poor reliability for single-fiber transmission. Summary of the Invention

[0003] The embodiment of the present invention provides a bidirectional optical fiber transmission system to solve the above technical problems.

[0004] A first aspect of an embodiment of the present invention provides a bidirectional optical fiber transmission system, comprising a first wavelength division multiplexer / demultiplexer, a second wavelength division multiplexer / demultiplexer, a first power amplifier, a second power amplifier, a first preamplifier, a second preamplifier, a first optical fiber switching module, a second optical fiber switching module, a first filter, a second filter, a third filter, a fourth filter, a first optical fiber, and a second optical fiber, wherein the optical signal multiplexing output end of the first wavelength division multiplexer / demultiplexer is connected to the input end of the first power amplifier, the optical signal multiplexing input end of the first wavelength division multiplexer / demultiplexer is connected to the output end of the second preamplifier, the output end of the first power amplifier is connected to the first common end of the first optical fiber switching module, the input end of the second preamplifier is connected to the second common end of the first optical fiber switching module, the first switching end of the first optical fiber switching module is connected to the first end of the first filter, the second switching end of the first optical fiber switching module is connected to the second end of the first filter, the third switching end of the first optical fiber switching module is connected to the first end of the third filter, and the first optical fiber switching module The fourth switching end of the first filter is connected to the second end of the third filter, the third end of the first filter is connected to one end of the first optical fiber, the other end of the first optical fiber is connected to the first end of the second filter, the third end of the third filter is connected to one end of the second optical fiber, the other end of the second optical fiber is connected to the first end of the fourth filter, the second end of the second filter is connected to the fifth switching end of the second optical fiber switching module, the third end of the second filter is connected to the sixth switching end of the second optical fiber switching module, the second end of the fourth filter is connected to the seventh switching end of the second optical fiber switching module, the third end of the fourth filter is connected to the eighth switching end of the second optical fiber switching module, the third common end of the second optical fiber switching module is connected to the input end of the second power amplifier, the fourth common end of the second optical fiber switching module is connected to the input end of the first preamplifier, the output end of the second power amplifier is connected to the optical signal multiplexing input end of the second wavelength division multiplexer / demultiplexer, and the input end of the first preamplifier is connected to the optical signal multiplexing output end of the second wavelength division multiplexer / demultiplexer;

[0005] When the first common end of the first optical fiber switching module is connected to the first switching end, the second common end is connected to the second switching end, and the third common end of the second optical fiber switching module is connected to the fifth switching end, and the fourth common end is connected to the sixth switching end, the first optical fiber transmits an optical signal;

[0006] Alternatively, when the first common end of the first optical fiber switching module is connected to the third switching end, the second common end is connected to the fourth switching end, and the third common end of the second optical fiber switching module is connected to the seventh switching end, and the fourth common end is connected to the eighth switching end, the second optical fiber transmits the optical signal.

[0007] Optionally, when the first optical fiber transmits an optical signal, the first wavelength division multiplexer / demultiplexer multiplexes the optical signal within the first wavelength band into a first optical signal, the first power amplifier amplifies the first optical signal to obtain a second optical signal, the first optical fiber switching module switches to the first filter, so that the first filter filters the second optical signal to obtain a third optical signal, and outputs the third optical signal to the second filter through the first optical fiber, the second filter filters the third optical signal to obtain a fourth optical signal, the frequencies of the third optical signal and the fourth optical signal both fall within the first wavelength band, the second optical fiber switching module outputs the fourth optical signal to the first preamplifier, the first preamplifier amplifies the fourth optical signal to obtain a fifth optical signal, and the second wavelength division multiplexer / demultiplexer demultiplexes the fifth optical signal into an optical signal within the first wavelength band.

[0008] Optionally, when the first optical fiber transmits an optical signal, the second wavelength division multiplexer / demultiplexer multiplexes the optical signal within the second wavelength band into a sixth optical signal, the second power amplifier amplifies the sixth optical signal to obtain a seventh optical signal, the second optical fiber switching module switches to the second filter, so that the second filter filters the seventh optical signal to obtain an eighth optical signal, and outputs the eighth optical signal to the first filter through the first optical fiber, the first filter filters the eighth optical signal to obtain a ninth optical signal, the frequencies of the eighth and ninth optical signals both being within the second wavelength band, the first optical fiber switching module outputs the ninth optical signal to the second preamplifier, the second preamplifier amplifies the ninth optical signal to obtain a tenth optical signal, and the first wavelength division multiplexer / demultiplexer demultiplexes the tenth optical signal into optical signals within the second wavelength band.

[0009] Optionally, when the second optical fiber transmits an optical signal, the first wavelength division multiplexer / demultiplexer multiplexes the optical signal within the first wavelength band into a first optical signal, the first power amplifier amplifies the first optical signal to obtain a second optical signal, the first optical fiber switching module switches to the third filter, so that the third filter filters the second optical signal to obtain a third optical signal, and outputs the third optical signal to the fourth filter through the second optical fiber. The fourth filter filters the third optical signal to obtain a fourth optical signal, and the frequencies of the third and fourth optical signals are both within the first wavelength band. The second optical fiber switching module outputs the fourth optical signal to the first preamplifier, the first preamplifier amplifies the fourth optical signal to obtain a fifth optical signal, and the second wavelength division multiplexer / demultiplexer demultiplexes the fifth optical signal into an optical signal within the first wavelength band.

[0010] Optionally, when the second optical fiber transmits an optical signal, the second wavelength division multiplexer / demultiplexer multiplexes the optical signal within the second wavelength band into a sixth optical signal, the second power amplifier amplifies the sixth optical signal to obtain a seventh optical signal, the second optical fiber switching module switches to the fourth filter, so that the fourth filter filters the seventh optical signal to obtain an eighth optical signal, and outputs the eighth optical signal to the third filter through the second optical fiber. The third filter filters the eighth optical signal to obtain a ninth optical signal, and the frequencies of the eighth and ninth optical signals are both within the second wavelength band. The first optical fiber switching module outputs the ninth optical signal to the second preamplifier, the second preamplifier amplifies the ninth optical signal to obtain a tenth optical signal, and the first wavelength division multiplexer / demultiplexer demultiplexes the tenth optical signal into an optical signal within the second wavelength band.

[0011] Optionally, the first optical fiber switching module includes a first optical splitter and a first optical switch, the first end of the first optical splitter is the first common end, the second end of the first optical splitter is the first switching end, the third end of the first optical splitter is the third switching end, the first end of the first optical switch is the second common end, the second end of the first optical switch is the second switching end, and the third end of the first optical switch is the fourth switching end.

[0012] Optionally, the second optical fiber switching module includes a second optical splitter and a second optical switch, the first end of the second optical splitter is the third common end, the second end of the second optical splitter is the fifth switching end, the third end of the second optical splitter is the seventh switching end, the first end of the second optical switch is the fourth common end, the second end of the second optical switch is the sixth switching end, and the third end of the second optical switch is the eighth switching end.

[0013] Optionally, when the first end of the first filter receives an optical signal within a first wavelength range, the third end of the first filter outputs an optical signal within the first wavelength range;

[0014] When the third end of the first filter receives optical signals within the first wavelength range and the second wavelength range, the second end of the first filter outputs optical signals within the second wavelength range;

[0015] When the first end of the second filter receives optical signals within the first wavelength range and the second wavelength range, the third end of the first filter outputs the optical signal within the first wavelength range;

[0016] When the second end of the second filter receives an optical signal within a second wavelength band, the first end of the second filter outputs an optical signal within the second wavelength band.

[0017] Optionally, when the first end of the third filter receives an optical signal within a first wavelength band, the third end of the third filter outputs an optical signal within the first wavelength band;

[0018] When the third end of the third filter receives optical signals within the first wavelength range and the second wavelength range, the second end of the third filter outputs optical signals within the second wavelength range;

[0019] When the first end of the fourth filter receives optical signals within the first wavelength range and the second wavelength range, the third end of the fourth filter outputs the optical signal within the first wavelength range;

[0020] When the second end of the fourth filter receives an optical signal within a second wavelength band, the first end of the fourth filter outputs an optical signal within the second wavelength band.

[0021] Optionally, the bidirectional optical fiber transmission system further includes a first compensation module and a second compensation module, wherein the first compensation module is located between the first wavelength division multiplexer / demultiplexer and the second preamplifier, and the second compensation module is located between the second wavelength division multiplexer / demultiplexer and the first preamplifier.

[0022] The technical effect of the embodiment of the present invention is: by introducing a first wavelength division multiplexer / demultiplexer, a second wavelength division multiplexer / demultiplexer, a first power amplifier, a second power amplifier, a first preamplifier, a second preamplifier, a first optical fiber switching module, a second optical fiber switching module, a first filter, a second filter, a third filter and a fourth filter, a dual-fiber switchable bidirectional optical fiber transmission system is constructed, which not only supports automatic switching to a backup optical fiber link when a single optical fiber link fails or the performance degrades, but also realizes the diversion and combination of band signals through filters to ensure the stability and anti-interference ability of the transmission signal; compared with the existing technology, this technical solution significantly improves the reliability and maintainability in complex environments, is suitable for cost-sensitive or wiring-limited communication scenarios, and effectively solves the problem that the existing single-fiber bidirectional communication cannot be restored when the link fails. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 This is a first structural diagram of a bidirectional optical fiber transmission system provided by the first embodiment of the present invention;

[0025] Figure 2 This is a schematic structural diagram of a first optical fiber switching module and a second optical fiber switching module in a bidirectional optical fiber transmission system provided in a first embodiment of the present invention;

[0026] Figure 3 This is a second structural diagram of a bidirectional optical fiber transmission system provided in the first embodiment of the present invention;

[0027] In the figure: 101, first wavelength division multiplexer / demultiplexer; 102, first power amplifier; 103, first optical fiber switching module; 104, first filter; 105, second filter; 106, third filter; 107, fourth filter; 108, second optical fiber switching module; 109, second power amplifier; 110, first preamplifier; 111, second wavelength division multiplexer / demultiplexer; 112, second preamplifier; 113, first optical fiber; 114, second optical fiber; 115, first compensation module; 116, second compensation module; 201, first optical splitter; 202, first optical switch; 203, second optical splitter; 204, second optical switch. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] It should be understood that the present invention can be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the invention to those skilled in the art. In the drawings, the dimensions and relative dimensions of layers and regions may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0030] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, a first element, component, region, layer, or part discussed below may be represented as a second element, component, region, layer, or part without departing from the teachings of the present invention.

[0031] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0032] In order to fully understand the present invention, detailed structures and steps will be provided in the following description to illustrate the technical solutions proposed by the present invention. Preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other implementations.

[0033] Example 1

[0034] This embodiment provides a bidirectional optical fiber transmission system. Figure 1 As shown, a first wavelength division multiplexer / demultiplexer 101, a second wavelength division multiplexer / demultiplexer 111, a first power amplifier 102, a second power amplifier 109, a first preamplifier 110, a second preamplifier 112, a first optical fiber switching module 103, a second optical fiber switching module 108, a first filter 104, a second filter 105, a third filter 106, a fourth filter 107, a first optical fiber and a second optical fiber, an optical signal multiplexing output end of the first wavelength division multiplexer / demultiplexer 101 is connected to the input end of the first power amplifier 102, and the first wavelength division multiplexer / demultiplexer 1 The optical signal multiplexing input end of 01 is connected to the output end of the second preamplifier 112, the output end of the first power amplifier 102 is connected to the first common end of the first optical fiber switching module 103, the input end of the second preamplifier 112 is connected to the second common end of the first optical fiber switching module 103, the first switching end of the first optical fiber switching module 103 is connected to the first end of the first filter 104, the second switching end of the first optical fiber switching module 103 is connected to the second end of the first filter 104, the third switching end of the first optical fiber switching module 103 is connected to the first end of the third filter 106, and the first optical fiber switching module 103 is connected to the first end of the third filter 106. The fourth switching end of the first filter 103 is connected to the second end of the third filter 106, the third end of the first filter 104 is connected to one end of the first optical fiber 113, the other end of the first optical fiber 113 is connected to the first end of the second filter 105, the third end of the third filter 106 is connected to one end of the second optical fiber 114, the other end of the second optical fiber 114 is connected to the first end of the fourth filter 107, the second end of the second filter 105 is connected to the fifth switching end of the second optical fiber switching module 108, the third end of the second filter 105 is connected to the sixth switching end of the second optical fiber switching module 108, and the second end of the fourth filter 107 is connected to the The output end of the second power amplifier 109 is connected to the optical signal multiplexing input end of the second wavelength division multiplexer / demultiplexer 111, and the input end of the first preamplifier 110 is connected to the optical signal multiplexing output end of the second wavelength division multiplexer / demultiplexer 111;

[0035] When the first common end of the first optical fiber switching module 103 is connected to the first switching end, the second common end is connected to the second switching end, and the third common end of the second optical fiber switching module 108 is connected to the fifth switching end, and the fourth common end is connected to the sixth switching end, the first optical fiber 113 transmits an optical signal;

[0036] Alternatively, when the first common end of the first optical fiber switching module 103 is connected to the third switching end, the second common end is connected to the fourth switching end, and the third common end of the second optical fiber switching module 108 is connected to the seventh switching end, and the fourth common end is connected to the eighth switching end, the second optical fiber 114 transmits the optical signal.

[0037] The first wavelength division multiplexer / demultiplexer 101 multiplexes and outputs multiple optical signals of different wavelengths or demultiplexes and outputs received optical signals, implementing optical signal multiplexing / demultiplexing and supporting the management of different wavelength channels in a single-fiber bidirectional transmission structure. The second wavelength division multiplexer / demultiplexer 111 cooperates with the first wavelength division multiplexer / demultiplexer 101 to implement multiplexing and demultiplexing functions for multiple optical signals of different wavelengths at the other end of the system, completing wavelength division channel management in the receiving or transmitting direction, and ensuring the correct separation and aggregation of optical signals. The first power amplifier 102 amplifies the optical signal output from the first wavelength division multiplexer / demultiplexer 101 to compensate for optical power loss during long-distance transmission and ensure that the signal strength is sufficient to enter the primary / backup optical fiber path. The second power amplifier 109 amplifies the optical signal output from the second wavelength division multiplexer / demultiplexer 111 to compensate for optical power loss during long-distance transmission and ensure that the signal strength is sufficient to enter the primary / backup optical fiber path. The first preamplifier 110 preamplifies the output weak optical signal, improving the signal-to-noise ratio (SNR) of subsequent circuit processing. It works in conjunction with the second wavelength division multiplexer / demultiplexer 111 to enhance the ability to detect low light intensity. The second preamplifier 112 amplifies the input signal in the opposite direction, assisting the system's opposite transmission path. It collaborates with the first wavelength division multiplexer / demultiplexer 101 to enhance the ability to detect low light intensity. The first fiber switching module 103 is used to select whether to direct the signal output from the first power amplifier 102 to the primary optical fiber path (first optical fiber 113) or the backup optical fiber path (second optical fiber 114). This provides active optical path switching capability, allowing transmission to be switched to the second optical fiber 114 if the first optical fiber 113 is broken or malfunctions. The second fiber switching module 108 receives the return optical signal from the first optical fiber 113 or the second optical fiber 114, enabling optical path selection in the receive link direction and supporting switching between the primary and backup links. The first filter 104 performs wavelength selection and noise suppression on the optical signal before it enters the first optical fiber 113. Second filter 105 performs wavelength selection and noise suppression on the signal returned from first optical fiber 113. Third filter 106, connected to second optical fiber 114, controls the wavelength or bandwidth of the optical signal on the backup channel. Fourth filter 107 processes the signal returned from second optical fiber 114, performing wavelength selection and noise suppression. First optical fiber 113 serves as the primary transmission path, enabling bidirectional optical signal transmission during normal system communication. Second optical fiber 114 serves as a backup path for first optical fiber 113, activated in the event of a failure in first optical fiber 113. This enhances system fault tolerance and reliability, enabling automatic or manual link switching protection.

[0038] The technical effect of this embodiment is that: by introducing the first wavelength division multiplexer / demultiplexer 101, the second wavelength division multiplexer / demultiplexer 111, the first power amplifier 102, the second power amplifier 109, the first preamplifier 110, the second preamplifier 112, the first optical fiber switching module 103, the second optical fiber switching module 108, the first filter 104, the second filter 105, the third filter 106 and the fourth filter 107, a dual-fiber switchable bidirectional optical fiber transmission system is constructed. It not only supports automatic switching to a backup optical fiber link when a single optical fiber link fails or the performance degrades, but also realizes the splitting and combining of band signals through filters to ensure the stability and anti-interference capability of the transmission signal. Compared with the existing technology, this technical solution significantly improves the reliability and maintainability in complex environments, is suitable for cost-sensitive or wiring-constrained communication scenarios, and effectively solves the problem that existing single-fiber bidirectional communication cannot be restored when a link fails.

[0039] As an embodiment, when the first optical fiber 113 transmits an optical signal, the first wavelength division multiplexer / demultiplexer 101 multiplexes the optical signal within the first wavelength band into a first optical signal. The first power amplifier 102 amplifies the first optical signal to obtain a second optical signal. The first optical fiber switching module 103 switches to the first filter 104, so that the first filter 104 filters the second optical signal to obtain a third optical signal, and outputs the third optical signal to the second filter 105 through the first optical fiber 113. The second filter 105 filters the third optical signal to obtain a fourth optical signal. The frequencies of the third and fourth optical signals are both within the first wavelength band. The second optical fiber switching module 108 outputs the fourth optical signal to the first preamplifier 110. The first preamplifier 110 amplifies the fourth optical signal to obtain a fifth optical signal. The second wavelength division multiplexer / demultiplexer 111 demultiplexes the fifth optical signal into an optical signal within the first wavelength band.

[0040] The technical effect of this embodiment is that by sequentially configuring a first wavelength division multiplexer / demultiplexer 101, a first power amplifier 102, a first filter 104, a first optical fiber switching module 103, and a first preamplifier 110 in a first optical fiber transmission path, stable transmission and enhancement of optical signals within a first wavelength band are achieved. Signal multiplexing and amplification at the transmitting end improves transmission performance, while filters are used during the relay process to ensure wavelength purity. Preamplification and demultiplexing restore the original signal at the receiving end, effectively reducing attenuation and crosstalk during signal transmission and improving the signal quality and overall reliability of the system in bidirectional communication over a single optical fiber.

[0041] As an embodiment, when the first optical fiber 113 transmits an optical signal, the second wavelength division multiplexer / demultiplexer 111 multiplexes the optical signal within the second wavelength band into a sixth optical signal. The second power amplifier 109 amplifies the sixth optical signal to obtain a seventh optical signal. The second optical fiber switching module 108 switches to the second filter 105, so that the second filter 105 filters the seventh optical signal to obtain an eighth optical signal, and outputs the eighth optical signal to the first filter 104 through the first optical fiber. The first filter 104 filters the eighth optical signal to obtain a ninth optical signal. The frequencies of the eighth and ninth optical signals are both within the second wavelength band. The first optical fiber switching module 103 outputs the ninth optical signal to the second preamplifier 112. The second preamplifier 112 amplifies the ninth optical signal to obtain a tenth optical signal. The first wavelength division multiplexer / demultiplexer 101 demultiplexes the tenth optical signal into an optical signal within the second wavelength band.

[0042] The technical effect of this embodiment is that, while the optical signal is transmitted through the first optical fiber 113, the reverse transmission and amplification of the optical signal within the second wavelength band are achieved. After the multi-wavelength signal is multiplexed by the second wavelength division multiplexer / demultiplexer 111, it undergoes power amplification, filtering, transmission through the first optical fiber, re-filtering and pre-amplification, and is finally demultiplexed and restored by the first wavelength division multiplexer / demultiplexer 101, achieving bidirectional independent transmission of signals of different wavelength bands within the same optical fiber. This design not only improves optical fiber utilization, but also ensures signal isolation and stability, effectively enhancing the system's communication capacity and anti-interference capabilities.

[0043] As an embodiment, when the second optical fiber 114 transmits an optical signal, the first wavelength division multiplexer / demultiplexer 101 multiplexes the optical signal within the first wavelength band into a first optical signal. The first power amplifier 102 amplifies the first optical signal to obtain a second optical signal. The first optical fiber switching module 103 switches to the third filter 106, so that the third filter 106 filters the second optical signal to obtain a third optical signal. The third optical signal is then output to the fourth filter 107 through the second optical fiber 114. The fourth filter 107 filters the third optical signal to obtain a fourth optical signal. The frequencies of the third and fourth optical signals are both within the first wavelength band. The second optical fiber switching module 108 outputs the fourth optical signal to the first preamplifier 110. The first preamplifier 110 amplifies the fourth optical signal to obtain a fifth optical signal. The second wavelength division multiplexer / demultiplexer 111 demultiplexes the fifth optical signal into an optical signal within the first wavelength band.

[0044] The technical effect of this embodiment is that: under the transmission path of the second optical fiber 114, efficient transmission and processing of optical signals within the first band are achieved; after the signal is multiplexed by the first wavelength division multiplexer / demultiplexer 101, the transmission power is increased with the help of a power amplifier, and the signal is screened and purified within the band in combination with the third filter 106 and the fourth filter 107, effectively suppressing interference components and ensuring signal quality; at the receiving end, the preamplifier performs gain compensation on the filtered signal, and finally restores it to the optical signal of the original band through the second wavelength division multiplexer / demultiplexer 111; this technical solution improves the transmission performance and stability of the backup optical fiber link, provides a guarantee for rapid switching when the main optical fiber fails, and enhances the reliability and redundancy fault tolerance of the system.

[0045] As an embodiment, when the second optical fiber 114 transmits an optical signal, the second wavelength division multiplexer / demultiplexer 111 multiplexes the optical signal within the second wavelength band into a sixth optical signal. The second power amplifier 109 amplifies the sixth optical signal to obtain a seventh optical signal. The second optical fiber switching module 108 switches to the fourth filter 107, so that the fourth filter 107 filters the seventh optical signal to obtain an eighth optical signal, and outputs the eighth optical signal to the third filter 106 through the second optical fiber 114. The third filter 106 filters the eighth optical signal to obtain a ninth optical signal. The frequencies of the eighth and ninth optical signals are both within the second wavelength band. The first optical fiber switching module 103 outputs the ninth optical signal to the second preamplifier 112. The second preamplifier 112 amplifies the ninth optical signal to obtain a tenth optical signal. The first wavelength division multiplexer / demultiplexer 101 demultiplexes the tenth optical signal into an optical signal within the second wavelength band.

[0046] The technical effect of this embodiment is that: under the transmission path of the second optical fiber 114, the reverse transmission and enhanced processing of the optical signal within the second wavelength band are realized. After the system multiplexes the multiple second-band signals through the second wavelength division multiplexer / demultiplexer 111, the signal strength is increased by the power amplifier, and the signal is double-filtered by the fourth and third filters 106 to ensure spectrum purity and signal stability. After the signal is transmitted to the receiving end, it is amplified by the second preamplifier 112 and input into the first wavelength division multiplexer / demultiplexer 101 for demultiplexing, and finally the complete second-band signal is restored. This technical solution provides a reliable backup channel when the main path fails, ensuring the continuity and high reliability of the two-way communication system and improving the system's fault resistance and flexibility.

[0047] As an implementation method, based on the existing bidirectional optical fiber transmission system, this implementation method further introduces a link state prediction and pre-switching mechanism to improve the intelligence level of the system and link stability.

[0048] In this embodiment, the bidirectional optical fiber transmission system further includes:

[0049] The link monitoring module is provided at one end of the first optical fiber 113 and one end of the second optical fiber 114, and is connected to the first filter 104 and the third filter 106 respectively, for detecting the transmission state parameters of the optical signal in real time;

[0050] The status assessment module is connected to the link monitoring module and the control module respectively, and is used to collect multiple link parameters from the primary and backup optical fibers and perform trend analysis to form a health score;

[0051] The control module is connected to the status evaluation module, the first fiber switching module 103 and the second fiber switching module 108, and is configured to output a predicted switching control instruction based on the health score to complete the preparation of the backup fiber path in advance.

[0052] The link monitoring module samples and caches key performance indicators (KPIs) such as signal power, bit error rate, delay jitter, and burst packet loss on the optical fiber link at a fixed period (e.g., every 50 ms). The status assessment module uses a multi-factor fusion algorithm (e.g., weighted average, sliding window, or machine learning model) to convert the continuously collected data into a real-time link health score (e.g., a range of 0 to 100). The control module sets two-level scoring thresholds. If the health score falls below the first scoring threshold, e.g., 70 points, "pre-switching preparation" is triggered; if it falls below the second scoring threshold, e.g., 50 points, "formal switching" is triggered. The control module activates the backup link (e.g., the second optical fiber 114) in advance and pre-adjusts the optical power, level, delay compensation, etc. to complete the link hot standby. When the health score of the main link further drops below 50, the control module controls the first optical fiber switching module 103 and the second optical fiber switching module 108 to switch to the second optical fiber 114, achieving seamless switching without service interruption.

[0053] The technical effects of this embodiment are as follows: this embodiment realizes the transformation from "passive responsive switching" to "active predictive switching" by introducing a link health prediction algorithm, significantly improving the stability and response speed of the optical fiber link; realizing a smooth switching process without service interruption, avoiding communication interruption caused by sudden link failure; and extending the working life of the main optical fiber and reducing the maintenance cost caused by link aging by activating the backup link and hot switching mechanism in advance.

[0054] Furthermore, in this embodiment, the link status assessment module generates a health score representing the current link quality by collecting and analyzing multiple link status parameters in multiple dimensions. This scoring mechanism includes the following core steps:

[0055] The parameters collected by the link monitoring module and transmitted to the status assessment module include at least:

[0056] Signal optical power value (P): indicates the actual optical power at the receiving end, in dBm;

[0057] Bit Error Rate (BER): Indicates the bit error rate of the optical signal during transmission;

[0058] Jitter: indicates the degree of phase fluctuation of the optical signal, affecting signal stability.

[0059] Packet loss rate (Loss): refers to the ratio of optical data packets that are not successfully received per unit time;

[0060] Slope: Build a trend curve based on the previous N samples to calculate whether the current indicator continues to deteriorate.

[0061] The status assessment module normalizes the above parameters and constructs a health score function, for example:

[0062] S = W1×f1(P) + W2×f2(BER) + W3×f3(Jitter) + W4×f4(Loss) +W5× f5(Slope).

[0063] Where: W1 to W5 are the weight coefficients of each scoring factor (configurable or adaptively adjusted); fi(X)

[0064] The corresponding scoring sub-functions are typically designed to include linear normalization, logarithmic compression, piecewise, gain-attenuation, and trend factor functions. The final output is a comprehensive score, typically ranging from 0 to 100, with higher values ​​indicating better link status. The ratings are as follows: S > 80: Healthy link; 50 ≤ S ≤ 80: Slightly degraded link, entering observation mode; 30 ≤ S < 50: Moderately degraded link, triggering pre-switching preparation; S < 30: Severely degraded link, triggering automatic switchover to the backup fiber.

[0065] To avoid permanently staying on the backup link and improve the utilization of the main link, this embodiment also introduces a link fallback mechanism, that is, after the main link is restored, the system can automatically switch back to the main optical fiber path.

[0066] When the system has switched to the backup link (e.g., the second optical fiber 114), the status assessment module continues to perform a health score on the primary link (e.g., the first optical fiber 113) and decides whether to fall back based on the following conditions:

[0067] The primary link health score continuously maintains S ≥ the fallback threshold (e.g., 85); the continuous score meets the condition for a duration T ≥ T_hold (e.g., 10 seconds); the current backup link health has no obvious advantage (e.g., the score difference is ≤ 10 points); the number of switchovers does not exceed the set threshold (to prevent frequent jitter). The fallback process is as follows:

[0068] After monitoring that the main link score continuously meets the fallback conditions, the status assessment module sends a "fallback preparation signal" to the prediction control module. The prediction control module activates the main link optical path and performs optical power matching and delay correction. After fallback preparation is complete, the control module controls the first fiber switching module 103 and the second fiber switching module 108 to switch back to the first fiber 113. After the switch, the first fiber is re-scored and confirmed. If the score remains ≥85 for three consecutive times, the fallback is completed and recorded. To avoid switching jitter, this mechanism also provides: a jitter suppression lock time: for example, it prohibits further switching within 30 seconds; a dynamic memory function: if the link degrades again after fallback, the next fallback wait time will be extended (such as exponential backoff); and fallback failure processing: if the score drops immediately after fallback, the original backup link is quickly restored.

[0069] This embodiment introduces a link fallback mechanism, which enables the system to continuously monitor the status of the main link and evaluate its health after completing the switch from the main optical fiber link to the backup optical fiber link. When the status of the main link returns to stability and continuously meets the set conditions, the system can automatically complete the switchback operation from the backup link to the main link. This mechanism has the following technical effects: when the status of the main link returns to normal, the main path is promptly rolled back to avoid long-term occupation of backup optical fiber resources and improve link utilization efficiency; through continuous scoring and jitter suppression mechanisms, signal fluctuations and service interruptions caused by frequent switching are avoided; dynamic scheduling and status perception between the main and backup paths are achieved, improving the system's intelligent operation capabilities in complex transmission environments; the fallback mechanism is combined with the link health scoring system to construct a closed-loop optimized optical fiber routing control logic, improving the robustness and long-term operation reliability of the entire optical fiber transmission system.

[0070] As an implementation method, Figure 2 As shown, the first optical fiber switching module 103 includes a first optical splitter 201 and a first optical switch 202, the first end of the first optical splitter 201 is a first common end, the second end of the first optical splitter 201 is a first switching end, the third end of the first optical splitter 201 is a third switching end, the first end of the first optical switch 202 is a second common end, the second end of the first optical switch 202 is a second switching end, and the third end of the first optical switch 202 is a fourth switching end.

[0071] The second optical fiber switching module 108 includes a second optical switch 204 and a second optical splitter 203. The first end of the second optical switch 204 is the third common end, the second end of the second optical switch 204 is the fifth switching end, and the third end of the second optical switch 204 is the seventh switching end. The first end of the second optical splitter 203 is the fourth common end, the second end of the second optical splitter 203 is the sixth switching end, and the third end of the second optical splitter 203 is the eighth switching end.

[0072] The first optical splitter 201 receives optical signals and splits them into two output paths, supporting parallel transmission preparation for the primary link (first optical fiber 113) and the backup link (second optical fiber 114). The first optical switch 202 implements optical path switching for the primary / backup link in the receive path, selecting whether to receive the optical signal from the primary or backup link. The second optical switch 204 receives the return optical signal from the primary or backup optical fiber and selects the appropriate path to enter the second power amplifier 109. The second optical splitter 203 distributes the signal demultiplexed by the second wavelength division multiplexer / demultiplexer 111 to the primary / backup receive path for amplification by the first preamplifier 110.

[0073] The technical benefit of this embodiment lies in the fact that, through the combined structure of an optical splitter and an optical switch, flexible switching of optical signals between the primary and backup optical fibers is achieved, improving the system's fault tolerance and reliability. If a failure occurs on the primary link, the system can quickly switch to the backup link, ensuring the continuity and stability of optical signal transmission, thereby effectively improving the operational safety and communication stability of the bidirectional optical fiber transmission system.

[0074] As an embodiment, when the first end of the first filter 104 receives an optical signal within a first wavelength range, the third end of the first filter 104 outputs an optical signal within the first wavelength range;

[0075] When the third end of the first filter 104 receives optical signals within the first wavelength range and the second wavelength range, the second end of the first filter 104 outputs optical signals within the second wavelength range;

[0076] When the first end of the second filter 105 receives optical signals within the first wavelength range and the second wavelength range, the third end of the first filter 104 outputs the optical signal within the first wavelength range;

[0077] When the second end of the second filter 105 receives an optical signal within the second wavelength band, the first end of the second filter 105 outputs an optical signal within the second wavelength band.

[0078] The function of the first filter 104 can be summarized as band-selective separation. Based on the wavelength content of the input optical signal, it outputs signals of target wavelengths from different ports. The first port inputs only the first wavelength range (e.g., C-band), while the third port outputs optical signals within the first wavelength range. The third port inputs optical signals containing both the first wavelength range and the second wavelength range (e.g., C+L band) transmitted in the first optical fiber, while the second port outputs optical signals within the second wavelength range (e.g., L-band). This function acts as a filter separation device, separating and outputting light of different wavelengths through different paths. The second filter 105 also has three ports: the first, second, and third ports. Its function is similar to that of the first filter 104, but it is used for wavelength selection at the receiving end of the system. Its functionality is as follows: the first port inputs both the first and second wavelength ranges, while the third port outputs optical signals within the first wavelength range (e.g., C-band). The desired wavelength band is extracted from the composite optical signal and outputted. The second port inputs only the second wavelength range, enabling reverse transmission and output of L-band optical signals returned from the backup link.

[0079] The technical effect of this embodiment is that by providing a multi-port band separation function in the first filter 104 and the second filter 105, automatic identification and path distribution of optical signals of different bands are achieved; according to the difference in input port and optical signal band, the optical signals of the first band and the second band can be respectively directed to the corresponding paths, effectively realizing dynamic routing and precise control of multi-band signals in the primary / backup link, thereby improving the system's wavelength division processing capability and the flexibility and reliability of optical signal transmission.

[0080] As an implementation manner, when the first end of the third filter 106 receives an optical signal within a first wavelength range, the third end of the third filter 106 outputs an optical signal within the first wavelength range;

[0081] When the third end of the third filter 106 receives optical signals within the first wavelength range and the second wavelength range, the second end of the third filter 106 outputs optical signals within the second wavelength range;

[0082] When the first end of the fourth filter 107 receives optical signals in the first wavelength range and the second wavelength range, the third end of the fourth filter 107 outputs the optical signal in the first wavelength range;

[0083] When the second end of the fourth filter 107 receives an optical signal within the second wavelength band, the first end of the fourth filter 107 outputs an optical signal within the second wavelength band.

[0084] As an implementation, the function of the third filter 106 can be summarized as band-selective separation. Based on the wavelength content of the input optical signal, it outputs signals of target wavelengths from different ports. The first port inputs only the first wavelength range (e.g., C-band), while the third port outputs optical signals within the first wavelength range. The third port inputs optical signals containing both the first wavelength range and the second wavelength range (e.g., C+L band) transmitted in the first optical fiber, while the second port outputs optical signals within the second wavelength range (e.g., L-band). This function serves as a filter separation device, separating and outputting light of different wavelength bands through different paths. The fourth filter 107 also has three ports: a first port, a second port, and a third port. Its function is similar to that of the third filter 106, but it is used for wavelength selection at the receiving end of the system. Its functionality is as follows: the first port inputs both the first and second wavelength ranges, while the third port outputs optical signals within the first wavelength range (e.g., C-band). The desired wavelength band is extracted from the composite optical signal and outputted. The second port inputs only the second wavelength range, enabling reverse transmission and output of L-band optical signals returned from the backup link.

[0085] The technical effect of this embodiment is that by providing a multi-port band separation function in the first filter 104 and the second filter 105, automatic identification and path distribution of optical signals in different bands are achieved. Depending on the input port and the optical signal band, the optical signals in the first and second bands can be directed to the corresponding paths, effectively achieving dynamic routing and precise control of multi-band signals in the primary and backup links, thereby improving the system's wavelength division processing capabilities and the flexibility and reliability of optical signal transmission.

[0086] As an implementation method, the first filter 104, the second filter 105, the third filter 106 and the fourth filter 107 not only have basic optical band screening functions, but are also further designed to have dynamic passband control, multi-band identification and link status adaptive adjustment capabilities, thereby supporting more complex wavelength division multiplexing systems and intelligent link management systems.

[0087] The first filter 104 and the third filter 106 are respectively arranged in the transmitting channel, and filter the optical signal to be transmitted before the first optical fiber 113 and the second optical fiber 114 are connected, so as to separate the signals that do not belong to the target band in the multiplexed optical signal, thereby ensuring the purity and consistency of the signal band in the transmitting link. The second filter 105 and the fourth filter 107 are respectively arranged in the receiving channel, and filter the return signals of the first optical fiber 113 and the second optical fiber 114 before they enter the receiving end, thereby extracting the target signal within the preset band from the mixed signal to prevent signal crosstalk. The above four filters can be implemented using any of the following structures or a combination thereof:

[0088] Tunable optical filter, used to adjust the central wavelength and bandwidth in real time under the control of the control module;

[0089] Multi-port wavelength selective switch, used to support on-demand switching of multiple service bands simultaneously;

[0090] MEMS micro-electromechanical mirror arrays are used to control the direction of the light beam through angle deflection, achieving dynamic guidance of signal paths in different bands;

[0091] Arrayed waveguide grating (AWG) structure achieves precise wavelength separation and is suitable for dense wavelength division systems;

[0092] Fiber Bragg Grating (FBG) filters are suitable for highly selective reflection and transmission of single-band signals.

[0093] In this embodiment, all four filters establish a communication connection with the control module and possess the following dynamically controllable operating modes: Based on the type of service transmitted in the system (e.g., voice, data, video streaming, etc.), the control module issues control instructions to the filter modules, causing them to switch to the corresponding service band. For example, voice services are prioritized over the C-band; video services are transmitted in the L-band; and data synchronization services are transmitted in a backup bandwidth (e.g., the S-band). The status assessment module provides feedback to the control module, including parameters such as the current link optical power and bit error rate. The control module adjusts the filter passband configuration based on changes in the primary link quality. For example, if it detects that the power of the C-band signal on the primary link is continuously attenuating, the control module controls the first filter 104 to switch its passband to allow the L-band signal to pass, switching some services to the backup channel. The control module can simultaneously control the first filter 104, the second filter 105, and the third filter 106 and fourth filter 107 to operate in the same band mode, ensuring symmetry in band management between the transmit and receive links, thereby reducing the risk of mismatching. If a filter fails or an abnormal passband drift is detected, the control module can temporarily bypass the filter node, enable the bypass channel, and start the backup filter unit set in the system for compensation; in a multi-filter system, it can also temporarily switch to the redundant band channel to continue communication.

[0094] Taking the first filter 104 as an example, when it is in the primary channel, the control process is as follows: the control module sets the current main link service type to "high-definition video streaming" and selects its transmission band as the L-band; the control module sends a tuning control instruction to the first filter 104, locking its center wavelength to the range of 1565nm~1625nm (typical L-band); if the link status assessment module detects an increase in the L-band bit error rate, the control module can issue an instruction to switch the filter to the C-band passband (1530nm~1565nm) and simultaneously switch the transmission service flow to this band; throughout this process, the filter center wavelength and bandwidth can be continuously adjusted to ensure uninterrupted communication when the link degrades.

[0095] The technical effect of this embodiment is that by enhancing the functionality and dynamically configuring the first, second, third, and fourth filters, precise band selection, real-time channel switching, and service-aware scheduling are achieved in multi-band optical signal transmission scenarios. Compared to traditional static filtering structures, the filters are tunable, band-adaptive, and link-state linked, significantly improving the system's adaptability and anti-interference capabilities in complex transmission environments. Furthermore, band coordination and symmetrical scheduling can be achieved between the primary and backup links, supporting seamless switching and dynamic load balancing of optical signals between the primary and backup fibers, thereby enhancing the system's stability, flexibility, and scalability.

[0096] As an implementation method, Figure 3 As shown, the bidirectional optical fiber transmission system further includes a first compensation module 115 and a second compensation module 116. The first compensation module 115 is located between the first wavelength division multiplexer / demultiplexer 101 and the second preamplifier 112, and the second compensation module 116 is located between the second wavelength division multiplexer / demultiplexer 111 and the first preamplifier 110.

[0097] The first compensation module 115 processes the optical signal transmitted back from one end of the second wavelength division multiplexer / demultiplexer 111 to the first side. The first compensation module 115 is used to perform dispersion compensation, delay compensation, or power equalization compensation on the optical signal transmitted from the optical fiber link to the first wavelength division multiplexer / demultiplexer 101. It can dynamically adjust the amplitude, phase, or spectral response of the signal based on factors such as transmission distance, wavelength drift, or device insertion loss. This helps to improve the signal-to-noise ratio and spectral integrity of the optical signal before demultiplexing, ensure the stability of the preamplifier input signal, and reduce the bit error rate. The second compensation module 116 processes the optical signal transmitted back from the optical fiber link to the second side. It is used to perform corresponding physical layer compensation processing on the optical signal transmitted from the primary / backup optical fiber path to the second wavelength division multiplexer / demultiplexer 111. It can adjust the power fluctuation of the optical signal and eliminate the delay and attenuation differences caused by different paths, devices, or bands. It ensures that the signal received by the first preamplifier 110 has consistent amplitude, clear waveform, and no obvious distortion, thereby improving the accuracy of post-processing.

[0098] The technical effect of this embodiment is that the first compensation module 115 and the second compensation module 116 serve as auxiliary enhancement units in the optical link, serving the receiving directions on both sides of the bidirectional path respectively, which helps to improve the system's adaptability to problems such as long-distance transmission, multipath interference and band imbalance, and enhances the anti-interference, stability and transmission quality consistency of the entire bidirectional optical fiber transmission system.

[0099] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A bidirectional optical fiber transmission system, characterized in that: The optical fiber switching module comprises a first wavelength division multiplexer / demultiplexer, a second wavelength division multiplexer / demultiplexer, a first power amplifier, a second power amplifier, a first preamplifier, a second preamplifier, a first optical fiber switching module, a second optical fiber switching module, a first filter, a second filter, a third filter, a fourth filter, a first optical fiber and a second optical fiber, wherein the optical signal multiplexing output end of the first wavelength division multiplexer / demultiplexer is connected to the input end of the first power amplifier, the optical signal multiplexing input end of the first wavelength division multiplexer / demultiplexer is connected to the output end of the second preamplifier, the output end of the first power amplifier is connected to the first common end of the first optical fiber switching module, the input end of the second preamplifier is connected to the second common end of the first optical fiber switching module, the first switching end of the first optical fiber switching module is connected to the first end of the first filter, the second switching end of the first optical fiber switching module is connected to the second end of the first filter, the third switching end of the first optical fiber switching module is connected to the first end of the third filter, and the fourth switching end of the first optical fiber switching module is connected to the the second ends of the three filters, the third end of the first filter is connected to one end of the first optical fiber, the other end of the first optical fiber is connected to the first end of the second filter, the third end of the third filter is connected to one end of the second optical fiber, the other end of the second optical fiber is connected to the first end of the fourth filter, the second end of the second filter is connected to the fifth switching end of the second optical fiber switching module, the third end of the second filter is connected to the sixth switching end of the second optical fiber switching module, the second end of the fourth filter is connected to the seventh switching end of the second optical fiber switching module, the third end of the fourth filter is connected to the eighth switching end of the second optical fiber switching module, the third common end of the second optical fiber switching module is connected to the input end of the second power amplifier, the fourth common end of the second optical fiber switching module is connected to the input end of the first preamplifier, the output end of the second power amplifier is connected to the optical signal multiplexing input end of the second wavelength division multiplexer / demultiplexer, and the input end of the first preamplifier is connected to the optical signal multiplexing output end of the second wavelength division multiplexer / demultiplexer; When the first common end of the first optical fiber switching module is connected to the first switching end, the second common end is connected to the second switching end, and the third common end of the second optical fiber switching module is connected to the fifth switching end, and the fourth common end is connected to the sixth switching end, the first optical fiber transmits an optical signal; Alternatively, when the first common end of the first optical fiber switching module is connected to the third switching end, the second common end is connected to the fourth switching end, and the third common end of the second optical fiber switching module is connected to the seventh switching end, and the fourth common end is connected to the eighth switching end, the second optical fiber transmits the optical signal.

2. The bidirectional optical fiber transmission system according to claim 1, wherein: When the first optical fiber transmits an optical signal, the first wavelength division multiplexer / demultiplexer multiplexes the optical signal within the first wavelength band into a first optical signal. The first power amplifier amplifies the first optical signal to obtain a second optical signal. The first optical fiber switching module switches to the first filter, causing the first filter to filter the second optical signal to obtain a third optical signal, and outputs the third optical signal to the second filter through the first optical fiber. The second filter filters the third optical signal to obtain a fourth optical signal. The frequencies of the third and fourth optical signals are both within the first wavelength band. The second optical fiber switching module outputs the fourth optical signal to the first preamplifier. The first preamplifier amplifies the fourth optical signal to obtain a fifth optical signal. The second wavelength division multiplexer / demultiplexer demultiplexes the fifth optical signal into an optical signal within the first wavelength band.

3. The bidirectional optical fiber transmission system according to claim 1, wherein: When the first optical fiber transmits an optical signal, the second wavelength division multiplexer / demultiplexer multiplexes the optical signal within the second wavelength band into a sixth optical signal. The second power amplifier amplifies the sixth optical signal to obtain a seventh optical signal. The second optical fiber switching module switches to the second filter, causing the second filter to filter the seventh optical signal to obtain an eighth optical signal, which is then output to the first filter through the first optical fiber. The first filter filters the eighth optical signal to obtain a ninth optical signal. The frequencies of the eighth and ninth optical signals are both within the second wavelength band. The first optical fiber switching module outputs the ninth optical signal to the second preamplifier. The second preamplifier amplifies the ninth optical signal to obtain a tenth optical signal. The first wavelength division multiplexer / demultiplexer demultiplexes the tenth optical signal into optical signals within the second wavelength band.

4. The bidirectional optical fiber transmission system according to claim 1, wherein: When the second optical fiber transmits an optical signal, the first wavelength division multiplexer / demultiplexer multiplexes the optical signal within the first wavelength band into a first optical signal. The first power amplifier amplifies the first optical signal to obtain a second optical signal. The first optical fiber switching module switches to the third filter, causing the third filter to filter the second optical signal to obtain a third optical signal. The third optical signal is output to the fourth filter through the second optical fiber. The fourth filter filters the third optical signal to obtain a fourth optical signal. The frequencies of the third and fourth optical signals are both within the first wavelength band. The second optical fiber switching module outputs the fourth optical signal to the first preamplifier. The first preamplifier amplifies the fourth optical signal to obtain a fifth optical signal. The second wavelength division multiplexer / demultiplexer demultiplexes the fifth optical signal into an optical signal within the first wavelength band.

5. The bidirectional optical fiber transmission system according to claim 1, wherein: When the second optical fiber transmits an optical signal, the second wavelength division multiplexer / demultiplexer multiplexes the optical signal within the second wavelength band into a sixth optical signal. The second power amplifier amplifies the sixth optical signal to obtain a seventh optical signal. The second optical fiber switching module switches to the fourth filter, causing the fourth filter to filter the seventh optical signal to obtain an eighth optical signal. The eighth optical signal is output to the third filter through the second optical fiber. The third filter filters the eighth optical signal to obtain a ninth optical signal. The frequencies of the eighth and ninth optical signals are both within the second wavelength band. The first optical fiber switching module outputs the ninth optical signal to the second preamplifier. The second preamplifier amplifies the ninth optical signal to obtain a tenth optical signal. The first wavelength division multiplexer / demultiplexer demultiplexes the tenth optical signal into optical signals within the second wavelength band.

6. The bidirectional optical fiber transmission system according to any one of claims 1 to 5, wherein: The first optical fiber switching module includes a first optical splitter and a first optical switch. The first end of the first optical splitter is the first common end, the second end of the first optical splitter is the first switching end, and the third end of the first optical splitter is the third switching end. The first end of the first optical switch is the second common end, the second end of the first optical switch is the second switching end, and the third end of the first optical switch is the fourth switching end.

7. The bidirectional optical fiber transmission system according to any one of claims 1 to 5, wherein: The second optical fiber switching module includes a second optical splitter and a second optical switch, the first end of the second optical splitter is the third common end, the second end of the second optical splitter is the fifth switching end, the third end of the second optical splitter is the seventh switching end, the first end of the second optical switch is the fourth common end, the second end of the second optical switch is the sixth switching end, and the third end of the second optical switch is the eighth switching end.

8. The bidirectional optical fiber transmission system according to claim 1, wherein: When the first end of the first filter receives an optical signal within a first wavelength range, the third end of the first filter outputs an optical signal within the first wavelength range; When the third end of the first filter receives optical signals within the first wavelength range and the second wavelength range, the second end of the first filter outputs optical signals within the second wavelength range; When the first end of the second filter receives optical signals within the first wavelength range and the second wavelength range, the third end of the first filter outputs the optical signal within the first wavelength range; When the second end of the second filter receives an optical signal within a second wavelength band, the first end of the second filter outputs an optical signal within the second wavelength band.

9. The bidirectional optical fiber transmission system according to claim 1, wherein: When the first end of the third filter receives an optical signal within a first wavelength range, the third end of the third filter outputs an optical signal within the first wavelength range; When the third end of the third filter receives optical signals within the first wavelength range and the second wavelength range, the second end of the third filter outputs optical signals within the second wavelength range; When the first end of the fourth filter receives optical signals within the first wavelength range and the second wavelength range, the third end of the fourth filter outputs the optical signal within the first wavelength range; When the second end of the fourth filter receives an optical signal within a second wavelength band, the first end of the fourth filter outputs an optical signal within the second wavelength band.

10. The bidirectional optical fiber transmission system according to claim 1, wherein: The bidirectional optical fiber transmission system further includes a first compensation module and a second compensation module, wherein the first compensation module is located between the first wavelength division multiplexer / demultiplexer and the second preamplifier, and the second compensation module is located between the second wavelength division multiplexer / demultiplexer and the first preamplifier.

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