Optical amplification system balanced against background noise and method for balancing background noise thereof

Abstract

The application provides a kind of optical amplification system and its background noise balancing method for balancing background noise, belong to optical communication technical field, the optical amplification module in system output contains multiple candidate operating wavelengths and broadband background noise mixed optical signal;First wavelength division multiplexing module according to wavelength and flow to the corresponding multiple first flow channel of mixed optical signal;Optical path switching module according to the switch control channel corresponding to target operating wavelength is turned on, and the rest switch control channel is physically blocked;Second wavelength division multiplexing module is output by optical path switching module Multiple optical signals are converged into single optical signal output;The passband bandwidth of first flow channel is greater than the passband bandwidth of second convergence channel, so that second wavelength division multiplexing module uses band-pass filter window to the output optical signal of optical path switching module Secondary filtering processing.The application can accurately remove the edge noise associated with main signal while effectively balancing the background noise at different wavelengths.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to an optical amplification system and a method for balancing background noise. Background Technology

[0002] In the field of space laser communication, to achieve long-distance optical signal transmission, it is usually necessary to use an optical amplification module at the transmitting or receiving end to amplify the power of the weak optical signal. However, while amplifying the optical signal at the target operating wavelength, the optical amplification module inevitably generates broadband background noise covering the entire communication frequency band due to its internal physical stimulated emission process.

[0003] In multi-wavelength switching space communication applications, the gain characteristics and noise figures of the optical amplification module are not perfectly flat for different wavelengths, resulting in significant differences in the background noise level when the system switches between different operating wavelengths. This imbalance in background noise can severely affect the demodulation consistency at the receiver and the overall stability of the communication system. Summary of the Invention

[0004] This invention provides an optical amplification system and a method for balancing background noise, which can effectively balance background noise at different wavelengths while accurately removing noise associated with the edge of the main signal.

[0005] In a first aspect, the present invention provides an optical amplification system for balancing background noise, comprising an optical amplification module, a first wavelength division multiplexing module, an optical path switching module, and a second wavelength division multiplexing module connected in sequence via optical communication; The optical amplification module is used to amplify the input optical signal and output a mixed optical signal containing multiple candidate operating wavelengths and broadband background noise. The first wavelength division multiplexing module is used to split the mixed optical signal according to wavelength to a plurality of corresponding first split channels; The optical path switching module includes multiple switch control channels that are respectively connected to the multiple first split channels. It is used to turn on the switch control channel corresponding to the target operating wavelength according to communication requirements and physically block the other switch control channels to filter out non-target wavelength frequency band noise in the broadband background noise. The second wavelength division multiplexing module includes multiple second convergence channels that are respectively connected to the multiple switch control channels, and is used to converge multiple optical signals output by the optical path switching module into a single optical signal output; The passband bandwidth of the first split channel is greater than that of the second convergence channel, so that the second wavelength division multiplexing module can use the bandpass filter window to perform secondary filtering on the output optical signal of the optical path switching module to filter out edge noise on both sides of the center frequency of the target operating wavelength.

[0006] In some embodiments, it also includes: A unidirectional isolation module is connected in series between the optical amplification module and the first wavelength division multiplexing module. It is used to allow the mixed optical signal to be transmitted from the optical amplification module to the first wavelength division multiplexing module and to block the reverse return optical signal generated by the subsequent optical path.

[0007] In some embodiments, the first wavelength division multiplexing module includes an input terminal and a plurality of first shunt output terminals, and the second wavelength division multiplexing module includes a plurality of second shunt input terminals and a multiplex output terminal; The optical path switching module includes optical switch units connected in series in each of the switch control channels. The input side of each unit is connected to the plurality of first shunt output terminals, and the output side is connected to the plurality of second shunt input terminals. Multiple parallel physical wavelength channels are formed between the first wavelength division multiplexing module and the second wavelength division multiplexing module.

[0008] In some embodiments, the passband bandwidth of the first shunt channel is 1.5 to 3 times the passband bandwidth of the second convergence channel.

[0009] In some embodiments, it also includes: The signal-to-noise ratio equalization control loop includes a variable optical attenuation module and a control module for communication connection; The variable optical attenuation module is disposed on the optical signal transmission path from each of the switch control channels to each of the second convergence channels, and the control module is disposed on the single output side of the second wavelength division multiplexing module, and is used to adjust the optical attenuation of the variable optical attenuation module disposed on the corresponding conduction switch control channel according to the optical signal-to-noise ratio of the optical signal on the single output side.

[0010] In some embodiments, the second wavelength division multiplexing module is provided with a passive filter structure, and the optical amplification system further includes: The temperature adaptation compensation loop includes a temperature sensor, a control module, and a temperature control module that are connected in sequence via communication. The temperature sensor is used to acquire the ambient temperature of the second wavelength division multiplexing module. The temperature control module is attached to the second wavelength division multiplexing module. The control module is used to drive the temperature control module to heat or cool the second wavelength division multiplexing module according to the ambient temperature.

[0011] In a second aspect, the present invention also provides a method for balancing background noise in an optical amplification system, for controlling the optical amplification system for balancing background noise as described in the first aspect, the method comprising: Obtain the wavelength switching command corresponding to the communication requirements; According to the wavelength switching command, the optical path switching module is controlled to turn on the switch control channel corresponding to the target operating wavelength and physically block the remaining switch control channels in order to filter out non-target wavelength band noise in the broadband background noise.

[0012] In some embodiments, it also includes: When the optical signal-to-noise ratio (SNR) of the single-channel output optical signal deviates from the absolute SNR reference at the current target operating wavelength, the attenuation compensation amount is obtained, and an adjustment command is sent to the variable optical attenuation module set in the corresponding current conduction switch control channel according to the attenuation compensation amount to adjust its optical attenuation amount until the optical signal-to-noise ratio of the single-channel output optical signal remains constant and consistent with the absolute SNR reference when switching to any candidate target operating wavelength.

[0013] In some embodiments, it also includes: When the ambient temperature fluctuation of the second wavelength division multiplexing module causes the center wavelength of the bandpass filter window to drift, the channel attenuation compensation parameter is obtained according to the preset mapping relationship; wherein, the preset mapping relationship is the mapping relationship between the ambient temperature, the center wavelength drift of the bandpass filter window and the channel attenuation compensation parameter; The optical attenuation of the control channel in the optical path switching module is adjusted according to the channel attenuation compensation parameter to compensate for the optical signal attenuation caused by the center wavelength drift when the optical signal passes through the second wavelength division multiplexing module.

[0014] Thirdly, the present invention also provides a space communication device, including an optical amplification system for balancing background noise as described in the first aspect.

[0015] This invention directly eliminates background noise across the entire frequency band of non-target wavelengths by physically blocking the optical path switching module. By setting an asymmetric bandwidth structure where the bandwidth of the first shunt channel is greater than that of the second convergence channel, a secondary physical cut-off of the noise accompanying the target wavelength signal edge is achieved, further purifying the optical signal. When the system switches between different candidate operating wavelengths, each selected wavelength undergoes the exact same processing procedure. Since all unselected wavelengths and their accompanying noise are forcibly filtered to an extremely low, uniform level, and the residual noise of the selected wavelength itself is also suppressed to a consistently low level due to secondary filtering, the background noise level of the final output optical signal no longer varies significantly with different operating wavelengths. This achieves a balance of background noise at different wavelengths, thus ensuring the operational consistency of the laser communication payload. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of an optical amplification system for balancing background noise provided in an embodiment of the present invention; Figure 2 This is a schematic flowchart of a background noise balancing method for an optical amplification system provided in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0019] With the rapid development of low-Earth orbit satellite networking and space laser communication technology, the performance requirements for communication payloads are increasing. Erbium-doped fiber amplifiers (EDFAs), as core components in laser communication payloads, are used to directly amplify weak optical signals. However, the physical characteristics of traditional high-power EDFAs inevitably generate broadband spontaneous emission background noise during operation. The intensity of this background noise is strongly correlated with the amplification wavelength. When EDFAs operate at different wavelengths, such as 1540.56 nm and 1563.05 nm, the low-noise levels they generate differ significantly, with a maximum difference of up to 22 dB. This noise inconsistency severely affects the consistency of high-power EDFAs in laser communication payloads and the stability of communication links. To address the aforementioned technical problems, embodiments of this invention propose systems and methods for balancing low-noise at different wavelengths, such as methods and apparatus for balancing the background noise of high-power EDFAs, primarily solving the problem of varying low-noise levels at different wavelengths.

[0020] Figure 1 This is a schematic diagram of the structure of an optical amplification system for balancing background noise provided in an embodiment of the present invention. Figure 1As shown, the optical amplification system for balancing background noise includes an optical amplification module 101, a first wavelength division multiplexing module 102, an optical path switching module 103, and a second wavelength division multiplexing module 104 connected in sequence via optical communication. The optical amplification module 101 amplifies the input optical signal and outputs a mixed optical signal containing multiple candidate operating wavelengths and broadband background noise. The first wavelength division multiplexing module 102 splits the mixed optical signal according to wavelength to multiple corresponding first splitting channels part-1, part-2, part-3, part-n… The optical path switching module 103 includes multiple switching control channels part-10, part-20, part-30, part-n0… respectively connected to the multiple first splitting channels, used to switch according to the wavelength… The signal requires the switching control channel corresponding to the target operating wavelength to be turned on, and the remaining switching control channels are physically blocked to filter out non-target wavelength frequency band noise in the broadband background noise; the second wavelength division multiplexing module 104 includes multiple second convergence channels part-1', part-2', part-3', part-n', etc., which are respectively connected to multiple switching control channels to converge multiple optical signals output by the optical path switching module 103 into a single optical signal output; wherein, the passband bandwidth of the first split channel is greater than the passband bandwidth of the second convergence channel, so that the second wavelength division multiplexing module 104 uses a bandpass filter window to perform secondary filtering processing on the output optical signal of the optical path switching module 103 to filter out edge-related noise on both sides of the center frequency of the target operating wavelength.

[0021] Specifically, optical amplification module 101 refers to a device or group of devices used to amplify the power of the input optical signal, such as an erbium-doped fiber amplifier, whose output optical signal contains not only the amplified signal light but also broadband background noise. First wavelength division multiplexing module 102 refers to a passive optical device based on wavelength division multiplexing technology, capable of decomposing and distributing a mixed optical signal containing multiple wavelengths to multiple different output ports, i.e., the first splitting channel. Optical path switching module 103 refers to a controllable optical switch device or array of devices capable of selectively turning on or physically blocking a specific optical path among multiple parallel optical paths. Second wavelength division multiplexing module 104 refers to another type of wavelength division multiplexing passive optical device, whose function is the opposite of the first wavelength division multiplexing module 102, capable of converging optical signals of different wavelengths entering from multiple input ports, i.e., the second convergence channel, to a single output port.

[0022] The first splitter channel refers to the independent optical path inside or at the output of the first wavelength division multiplexing module 102, used to transmit optical signals within a specific wavelength range. The switch control channel refers to the independent optical path unit inside the optical path switching module 103, corresponding to each first splitter channel, responsible for controlling the conduction or blocking of the optical signal on that path. The second convergence channel refers to the input of the second wavelength division multiplexing module 104, used to receive optical signals from the corresponding outputs of the optical path switching module 103. Passband bandwidth refers to the frequency or wavelength range of optical signals allowed to pass through a specific channel of an optical channel, such as a wavelength division multiplexer. The wider the bandwidth, the larger the spectral range that can be transmitted.

[0023] The optical amplification module 101 first amplifies the weak input communication optical signal. The output of this process is not a single pure signal, but a mixed optical signal containing multiple candidate operating wavelengths—that is, several communication wavelengths the system might use—and broadband background noise covering the entire spectral range. This mixed optical signal enters the first wavelength division multiplexing module 102. The first wavelength division multiplexing module 102, utilizing its wavelength selectivity, splits the mixed optical signal according to different wavelengths into multiple corresponding first split channels. For example, light with wavelength λ1 and its nearby noise are directed into first split channel part-1, and light with wavelength λ2 and its nearby noise are directed into first split channel part-2. At this point, the optical signal in each channel is still a mixture of the center wavelength signal of that channel and the background noise within the bandwidth of that channel.

[0024] After being split, the multiple optical signals enter the respective switch control channels of the optical path switching module 103. Based on current communication requirements, such as the need to transmit light at wavelength λ2, the system sends a command to the optical path switching module 103. The optical path switching module 103 then activates the switch control channel corresponding to the target operating wavelength, such as λ2, allowing that optical signal to pass. Simultaneously, it physically blocks all other switch control channels, such as those corresponding to λ1, λ3, etc. Because the remaining channels are physically cut off, broadband background noise in the non-target wavelength bands transmitted within these channels is completely filtered out.

[0025] After being selected by the optical path switching module 103, note that only one optical path may be conducted by the optical path switching module 103, but physically multiple channels still exist, and the optical signal enters the second wavelength division multiplexing module 104. The second wavelength division multiplexing module 104 receives the optical signals from each optical path switching module 103 through its multiple second convergence channels and finally converges them into a single optical signal output. This step achieves physical multiplexing. In addition, the passband bandwidth of the first split channel is greater than that of the second convergence channel. This means that when an optical signal of a target operating wavelength passes through the wider first split channel, it still carries a certain width of edge noise on both sides. When the signal enters the second convergence channel with a narrower passband bandwidth, the bandpass filtering window of the second wavelength division multiplexing module 104 only allows light in a narrower range near the center frequency to pass through. Therefore, the accompanying noise that is close to the center frequency of the target operating wavelength and was originally at the edge of the bandwidth of the first split channel cannot pass through the narrower filtering window of the second wavelength division multiplexing module 104 and is effectively filtered out, realizing secondary fine filtering of the target optical signal.

[0026] Therefore, this embodiment of the invention directly eliminates background noise across the entire frequency band of non-target wavelengths through the physical blocking of the optical path switching module 103. By setting an asymmetric bandwidth structure where the bandwidth of the first shunt channel is greater than that of the second convergence channel, a secondary physical cut-off of the noise accompanying the edge of the target wavelength signal is achieved, further purifying the optical signal. When the system switches between different candidate operating wavelengths, each selected wavelength undergoes the exact same processing procedure. Since all unselected wavelengths and their accompanying noise are forcibly filtered out to an extremely low level, and the residual noise of the selected wavelength itself is also suppressed to a consistent low level due to secondary filtering, the background noise level of the final output optical signal no longer varies significantly due to different operating wavelengths, achieving a balance of background noise at different wavelengths, thereby ensuring the operational consistency of the laser communication payload.

[0027] In some embodiments, the optical amplification system for balancing background noise further includes a unidirectional isolation module 105 connected in series between the optical amplification module 101 and the first wavelength division multiplexing module 102, for allowing the mixed optical signal to be transmitted from the optical amplification module 101 to the first wavelength division multiplexing module 102, and blocking the reverse return optical signal generated by the subsequent optical path.

[0028] Specifically, the unidirectional isolation module 105 refers to an optical device that allows optical signals to transmit in only one direction, while having extremely high attenuation capability for optical signals transmitted in the opposite direction. Examples include fiber optic circulators or optical isolators. Its main function is to protect the preceding optical module from damage caused by reflected light or echoes from the following stage. The optical amplifier module 101, as a light source, is sensitive to echoes; strong echoes can lead to performance degradation or damage. Therefore, a unidirectional isolation module 105 is connected in series between the output of the optical amplifier module 101 and the input of the first wavelength division multiplexing module 102. The unidirectional isolation module 105 has a clear transmission directionality; that is, when the mixed optical signal output from the optical amplifier module 101 is transmitted in the forward direction, the unidirectional isolation module 105 exhibits low insertion loss, allowing the optical signal to pass smoothly and enter the first wavelength division multiplexing module 102. However, when reflected light generated by connection points or the devices themselves in the subsequent optical paths, such as the first wavelength division multiplexing module 102, the optical path switching module 103, or the second wavelength division multiplexing module 104, generates backflow optical signals, the unidirectional isolation module 105 presents extremely high isolation for these backflow optical signals, for example, greater than 50dB, which greatly attenuates them so that they cannot return to the optical amplification module 101.

[0029] Therefore, this embodiment of the invention effectively eliminates the threat posed by reflected light from the subsequent optical path to the preceding optical amplification module 101, preventing performance degradation or optical damage caused by reflected light, and significantly improving the stability and reliability of the system. This ensures that the state of the subsequent optical path, such as impedance mismatch or connector reflection, will not interfere with the normal operation of the optical amplification module 101, achieving effective isolation between the preceding and following stage circuits and the optical path.

[0030] In some embodiments, the first wavelength division multiplexing module 102 includes an input terminal and multiple first shunt output terminals, and the second wavelength division multiplexing module 104 includes multiple second shunt input terminals and a multiplexing output terminal; the optical path switching module 103 includes optical switch units respectively connected in series in each switch control channel, with its input side respectively connected to multiple first shunt output terminals and its output side respectively connected to multiple second shunt input terminals, and forming multiple parallel physical wavelength channels between the first wavelength division multiplexing module 102 and the second wavelength division multiplexing module 104.

[0031] Specifically, the input and output terminals refer to the ports on the optical module used to connect optical fibers. The input terminal is the port where the optical signal enters the module, and the output terminal is the port where the optical signal leaves the module. An optical switch unit refers to the basic element constituting the optical path switching module 103. It is a two-port or multi-port optical device with a controllable state, capable of quickly switching the input optical signal to a designated output port or completely blocking the transmission of the optical path under the control of an electrical signal. A parallel physical wavelength channel refers to an independent and physically separated optical transmission path formed by a first shunt output terminal of the first wavelength division multiplexing module 102, a corresponding optical switch unit connected to it, and a second shunt input terminal of the second wavelength division multiplexing module 104 connected to the optical switch unit. These different channels are physically parallel and do not interfere with each other.

[0032] The first wavelength division multiplexing (WDM) module 102 has one common input and N first split outputs. The mixed light enters from the common input and is decomposed into N different wavelength components, which are then output from the N first split outputs. The second WDM module 104 has N second split inputs and one common multiplexing output. The N different wavelengths of light enter from the N second split inputs and are ultimately combined into a single beam output from the common multiplexing output. The optical path switching module 103 consists of multiple independent optical switch units. The input side of each optical switch unit is connected to a corresponding first split output via optical fiber, and its output side is connected to a corresponding second split input via optical fiber. Through this point-to-point connection, the system establishes an independent and parallel physical wavelength channel between the first WDM module 102 and the second WDM module 104 for each candidate operating wavelength.

[0033] Therefore, in this embodiment of the invention, each wavelength channel is physically completely independent, and the optical signals from different channels will not interfere with or crosstalk each other during transmission, ensuring the purity of wavelength switching. Each optical switch unit can be controlled independently, thereby achieving precise and independent control of the conduction or blocking of different wavelength channels.

[0034] In some embodiments, the passband bandwidth of the first shunt channel is 1.5 to 3 times that of the passband bandwidth of the second convergence channel.

[0035] Specifically, the bandwidth multiple refers to the quotient obtained by dividing the passband bandwidth of the first shunt channel by the passband bandwidth of the second convergence channel. For example, if the passband bandwidth of the second convergence channel is 100 GHz, corresponding to a spectral width of approximately 0.8 nm, then the passband bandwidth of the first shunt channel is set between 150 GHz and 300 GHz, corresponding to a spectral width of approximately 1.2 nm to 2.4 nm. When an optical signal of the target operating wavelength passes through these two channels with different bandwidths sequentially, it first passes through the wider first shunt channel, ensuring that most of the signal energy passes through without loss. Subsequently, when the signal attempts to pass through the second convergence channel, whose bandwidth is only 1 / 1.5 to 1 / 3 of the former, the edge portion of the signal, i.e., the spectral component farther from the center frequency, mainly noise, will be significantly attenuated because it exceeds the narrower passband range of the second convergence channel. A bandwidth factor in the range of 1.5 to 3 times ensures sufficient cutting depth for edge-related noise while preventing the main lobe energy of the useful signal from being cut off due to excessive factor, thus achieving the best balance between noise suppression and signal fidelity.

[0036] Therefore, by limiting the passband bandwidth of the first shunt channel to 1.5 to 3 times the passband bandwidth of the second convergence channel, this embodiment of the invention provides a parameter range that achieves the optimal balance between signal throughput and noise suppression capability, avoiding signal loss due to excessive bandwidth ratio or incomplete noise filtering due to insufficient bandwidth ratio.

[0037] In some embodiments, the optical amplification system for balancing background noise further includes a signal-to-noise ratio equalization control loop, comprising a variable optical attenuation module and a control module connected in communication; wherein the variable optical attenuation module is disposed on the optical signal transmission path from each switch control channel to each second convergence channel, and the control module is disposed on the single-channel output side of the second wavelength division multiplexing module 104, for adjusting the optical attenuation amount of the variable optical attenuation module disposed on the corresponding conduction switch control channel according to the optical signal-to-noise ratio of the optical signal on the single-channel output side.

[0038] Specifically, the signal-to-noise ratio (SNR) equalization control loop refers to a closed-loop automatic control subsystem designed to dynamically maintain a stable SNR in the final output signal. A variable optical attenuation module refers to an optical device capable of continuously and dynamically changing its attenuation level for passing optical signals based on external electrical signal commands. A control module refers to a microprocessor or control circuit with data acquisition, logic operation, and command issuance functions. Optical signal-to-noise ratio (SNR) is the ratio of the effective power of the optical signal to the background noise power, and is a core indicator for measuring the quality of optical communication.

[0039] The signal-to-noise ratio (SNR) equalization control loop adds a variable optical attenuation module to the optical signal transmission path from each switch control channel to each second convergence channel. Simultaneously, a control module, which may include a beam splitting detection element, is added to the single-channel output side of the second wavelength division multiplexing module 104. During operation, even though the system has filtered out a significant amount of background noise through pre- and post-stage filtering, the optical signal-to-noise ratio (SNR) for different wavelengths may still not be completely consistent due to slight physical differences in the gain floor and inherent noise figure of the optical amplification module 101 for different wavelengths. The control module acquires the SNR of the single-channel output optical signal in real time and compares it with the expected target parameters. Based on the comparison results, the control module generates a power signal to the variable optical attenuation module located in the currently active switch control channel, fine-tuning its optical attenuation. For example, if the current wavelength SNR is slightly high, a slight increase in attenuation is applied.

[0040] For example, the control module acquires the optical signal-to-noise ratio (SNR) of the current output optical signal in real time and compares the measured value with a preset absolute SNR reference value. If the measured value deviates from the reference value—for example, when switching to wavelength λ2, the SNR is slightly lower than when switching to λ1—the control module calculates an attenuation compensation amount. For instance, if the measured value is too low, the attenuation amount needs to be reduced to improve the SNR; conversely, the attenuation amount needs to be increased. Based on the calculated attenuation compensation amount, an adjustment command is sent to the variable optical attenuation module corresponding to the currently active switch control channel. The variable optical attenuation module then changes its current optical attenuation amount, thereby changing the final output signal power and optical SNR. After multiple rapid monitoring, comparison, calculation, and adjustment cycles, the system eventually adjusts the output optical SNR at the current operating wavelength to match the absolute SNR reference value.

[0041] Therefore, through this active, dynamic, real-time fine-tuning, the system not only filters out background noise at the passive physical level but also smooths out the inherent slight differences between different operating wavelengths at the active control level. Regardless of how the system switches candidate operating wavelengths, the control module can precisely adjust the variable optical attenuation module within the corresponding conduction switch control channel, ensuring that the optical signal-to-noise ratio of the single-channel output optical signal remains at a completely consistent level. This achieves a balance between background noise and signal quality, meeting the stringent requirements of high-quality spatial multi-wavelength communication.

[0042] In some embodiments, a passive filter structure is provided in the second wavelength division multiplexing module 104, and the optical amplification system further includes a temperature adaptation compensation loop, including a temperature sensor, a control module, and a temperature control module that are connected in sequence; wherein, the temperature sensor is used to obtain the ambient temperature of the second wavelength division multiplexing module 104, the temperature control module is attached to the second wavelength division multiplexing module 104, and the control module is used to drive the temperature control module to heat or cool the second wavelength division multiplexing module 104 according to the ambient temperature.

[0043] Specifically, the passive filter structure refers to the core component within the second wavelength division multiplexing module 104 that implements wavelength selection. It can be a passive optical structure without active gain media, such as a thin-film filter, arrayed waveguide grating, or fiber grating. Its filtering characteristics, such as the center wavelength, will drift with temperature changes. The temperature adaptation compensation loop refers to a closed-loop control system used to combat the impact of environmental temperature changes on the performance of key components. The temperature sensor refers to a device used to sense and measure the temperature of an object and convert it into a usable output signal. The temperature control module refers to a device capable of heating or cooling a target object according to a control signal, such as a thermoelectric cooler or a heating resistor.

[0044] The passive filter structure inside the second wavelength division multiplexing module 104 undergoes slight changes in its physical dimensions and refractive index with temperature variations, causing a shift in the center wavelength of its bandpass filter window. For the second wavelength division multiplexing module 104, which has a very narrow passband, even a small wavelength shift can cause the filter window to deviate from the center of the target operating wavelength, resulting in erroneous attenuation of useful signal energy and a degraded system performance. This embodiment of the invention introduces a temperature adaptation compensation loop to actively suppress this drift. A temperature sensor attached to or inside the housing of the second wavelength division multiplexing module 104 accurately acquires the ambient temperature in real time and transmits the temperature data to the control module. The control module pre-stores a mapping relationship between the center wavelength drift of the second wavelength division multiplexing module 104 and temperature; for example, for every 1°C increase in temperature, the center wavelength shifts 0.01 nm towards longer wavelengths. When the control module detects a change in the current ambient temperature relative to a preset reference temperature, such as 25°C, it calculates whether heating or cooling is needed to bring the drifted center wavelength back to the correct position in order to correct the second wavelength division multiplexing module 104, and how much heat or cooling is required. Based on this, the control module drives a temperature control module, such as a thermoelectric cooler, attached to the second wavelength division multiplexing module 104. If the ambient temperature is too high, causing the wavelength to drift towards longer wavelengths, cooling is activated; if the ambient temperature is too low, causing the wavelength to drift towards shorter wavelengths, heating is activated. Through closed-loop control, the internal operating temperature of the second wavelength division multiplexing module 104 is kept stable near the reference temperature, thereby precisely anchoring and clamping the center wavelength of its filtering window to the preset target operating wavelength.

[0045] Therefore, this invention significantly enhances the system's adaptability to extreme temperature variations, which is particularly important for laser communication payloads operating in alternating hot and cold environments. It ensures that the filtering window of the second wavelength division multiplexing module 104, acting as a fine filter, is always aligned with the center wavelength of the target signal, thus guaranteeing the effectiveness and reliability of its secondary filtering function. It eliminates optical power fluctuations and signal-to-noise ratio degradation caused by temperature drift, ensuring long-term stable and high-performance system operation.

[0046] In some embodiments, the control terminal of the optical path switching module 103 is communicatively connected to the media access control layer controller of the external communication payload, for receiving the status signal of the communication payload data frame, and triggering the channel switching action of the optical path switching module 103 during the data frame guard interval or communication silence period.

[0047] Specifically, the Media Access Control (MAC) layer controller refers to the core digital logic controller in the communication system responsible for managing media access control at the data link layer and scheduling the transmission and reception timing of data frames. The guard interval or communication silence period refers to the extremely short time gap intentionally reserved by the system protocol between consecutively transmitted data frames, which does not contain any valid service data. The control terminal of the optical path switching module 103 is directly connected to the MAC layer controller of the external communication payload via a communication bus. When the system needs to switch wavelengths, the optical path switching module 103 does not immediately perform physical actions but remains in a waiting state. The MAC layer controller monitors the transmission and reception status of the communication payload data frames in real time. When it detects that the current data frame has been transmitted and the system has entered the data frame guard interval or communication silence period, it immediately sends a status signal to the optical path switching module 103. The optical path switching module 103 utilizes this extremely short data-free gap to instantly trigger and complete the physical switching action of the switching control channel.

[0048] Therefore, since active switching actions, whether mechanical or optoelectronic, inevitably introduce millisecond or microsecond-level transient jitter in optical power and signal interruptions, blind switching can easily lead to damage to transmitted service data packets or generate a large number of bit errors. By interacting with the underlying Media Access Control (MAC) layer controller, channel switching actions are precisely nested within guard intervals or communication quiet periods when there is no service data, achieving zero loss of service data and smooth transition during wavelength switching, significantly improving the data integrity and reliability of the entire optical communication link.

[0049] The following is a detailed description using a specific embodiment: like Figure 1As shown, the optical amplification system for balancing background noise consists of five parts: an optical fiber amplifier, an optical fiber circulator, a first wavelength division multiplexer (WDM), an optical switch assembly, and a second WDM. Specifically, the optical fiber amplifier is the optical amplification module 101, the optical fiber circulator is the unidirectional isolation module 105, the first WDM is the first WDM module 102, the optical switch assembly is the optical path switching module 103, and the second WDM is the second WDM module 104. The system uses the optical amplification module 101 to generate different wavelengths; this module is also the source for generating different low-noise wavelengths in a traditional optical fiber amplifier.

[0050] First, the amplified mixed optical signal is emitted by the optical amplification module 101, enters through the part1 port of the unidirectional isolation module 105, and exits through the part2 port. The outgoing light passes through the first wavelength division multiplexing module 102, where wavelength selection is performed, splitting the optical signal into multiple corresponding first split channels part-1, part-2, part-3, part-n... to select the actual light source for the fiber amplifier. Then, the wavelength channel is controlled by the optical path switching module 103, turning on the switching control channels part-10, part-20, part-30, part-n0... of the target operating wavelength. The signal is then filtered again by the second wavelength division multiplexing module 104, entering multiple corresponding second convergence channels part-1', part-2', part-3', part-n'... After entering the corresponding channel, it is connected to the laser communication payload through the beam combining port. Thus, all wavelengths other than the main wavelength can be filtered out, i.e., filtering out non-target wavelength band noise and edge-related noise in the broadband background noise, significantly reducing the noise floor capability of the fiber amplifier.

[0051] For example, the optical amplification module 101 can be a fiber optic amplifier with a polarization contrast greater than or equal to 20dB, capable of switching between 1540.56nm and 1563.05nm wavelengths. The unidirectional isolation module 105 can be a fiber optic circulator with an operating wavelength from 1520nm to 1580nm, a transmit / receive isolation better than 50dB, a mode field core diameter of 10.1±0.4μm at 1550nm wavelength, and a numerical aperture (NA) of 0.125. The first wavelength division multiplexing module 102 can be a wavelength division multiplexer with three channels: 1540.56nm, 1563.05nm, and 1550nm, forming multiple corresponding first shunt channels. Both 1540.56nm and 1563.05nm correspond to a 200G passband bandwidth. The optical path switching module 103 can use an optical switch component, model MEMS-PMOSM-1*3-1550-PM-900-FC / APC-60*24*11, which can switch between different modes and has multiple switch control channels internally. The second wavelength division multiplexing module 104 can use a wavelength division multiplexer with three channels, namely 1540.56nm, 1563.05nm and 1550nm, forming multiple corresponding second convergence channels. 1540.56nm and 1563.05nm both correspond to 100G passband bandwidth.

[0052] When the optical amplification module 101 selects 1540.56nm, 1563.05nm, or other candidate working wavelengths for transmission, the mixed wavelength light containing the target wavelength enters through the part1 port of the unidirectional isolation module 105, and exits through the part2 port. Then, the wavelength light passes through the first splitting channels part-1, part-2, part-3, part-n... of the first wavelength division multiplexing module 102, selecting the corresponding channel to enter the optical path switching module 103. The optical path switching module 103 selects the corresponding wavelength light by opening the switching control channels part-10, part-20, part-30, part-n0... according to communication requirements, and physically blocks the other channels. Then, the wavelength light passes through the second wavelength division multiplexing module 104, through the second convergence channels part-1', part-2', part-3', part-n'... of the second wavelength division multiplexing module 104, and performs wavelength selection and secondary filtering using the bandpass filter window to complete the final wavelength combining and output.

[0053] In summary, the embodiments of the present invention can balance the noise figure at different wavelengths, making the noise figure consistent; the use of a unidirectional isolation module 105 avoids the return power from affecting and damaging the optical amplification module 101; and the optical path switching module 103 completes the selection of wavelength and physical isolation. This solves the problem of low noise differences caused by different transmission wavelengths in the use of existing erbium-doped fiber amplifiers, achieving selection of different wavelengths, physically blocking other channels, and effectively removing non-working wavelength light; the use of the wavelength division multiplexer's asymmetric bandwidth design allows for further filtering and cutting, selecting even purer effective light.

[0054] This invention also provides a method for background noise balancing in an optical amplification system. Figure 2 This is a schematic flowchart illustrating a background noise balancing method for an optical amplification system provided in an embodiment of the present invention. The background noise balancing method for an optical amplification system can be used to control an optical amplification system with balanced background noise as described in the above embodiments. Figure 2 As shown, the background noise balancing method for an optical amplification system includes the following steps: S201. Obtain the wavelength switching command corresponding to the communication requirements.

[0055] S202. According to the wavelength switching command, the optical path switching module is controlled to turn on the switch control channel corresponding to the target working wavelength and physically block the other switch control channels in order to filter out non-target wavelength frequency band noise in the broadband background noise.

[0056] Specifically, the wavelength switching command refers to a command signal issued by the upper-level communication control unit that explicitly instructs the optical amplification system to switch its current operating wavelength to a candidate operating wavelength. The system's control module first acquires the wavelength switching command from an external source or generated internally. This command explicitly specifies the target operating wavelength to be used in the next communication time slot, for example, switching to wavelength 1563.05nm. After parsing the command, the control module sends a precise control signal to the optical path switching module 103. Based on this signal, the optical path switching module 103 finds the switch control channel corresponding to the target operating wavelength from all parallel physical wavelength channels and sets it to the ON state, allowing the optical signal to pass through unimpeded. Simultaneously, the optical path switching module 103 sets all other switch control channels to the physical OFF state. In the broadband background noise, all noise components located in non-target operating wavelength bands are filtered out because their corresponding physical transmission channels have been completely cut off, preventing them from reaching the system output.

[0057] In some embodiments, the background noise balancing method of the optical amplification system further includes: when the optical signal-to-noise ratio of the single-channel output side optical signal at the current target operating wavelength deviates from the absolute signal-to-noise ratio reference, obtaining the attenuation compensation amount, and sending an adjustment command to the variable optical attenuation module set according to the attenuation compensation amount to adjust its optical attenuation amount, until the optical signal-to-noise ratio of the single-channel output side optical signal remains constant and consistent with the absolute signal-to-noise ratio reference when switching to any candidate target operating wavelength.

[0058] Specifically, the absolute signal-to-noise ratio (SNR) reference refers to a pre-set fixed value that serves as the target for controlling the system's output optical SNR. The system will strive to ensure that the output optical SNR at any wavelength is precisely equal to this reference value. The attenuation compensation amount refers to a value calculated by the control module, indicating whether the optical attenuation of the current variable optical attenuation module needs to be increased or decreased to bring the output optical SNR back to the absolute SNR reference value.

[0059] After the system stably outputs the optical signal at the target operating wavelength, the control module continuously monitors the optical signal-to-noise ratio (SNR) on the single-channel output side of the second wavelength division multiplexing module 104. It compares this measured value with the internally stored absolute SNR benchmark to determine if there is a deviation. Once a deviation is detected, the control module calculates an attenuation compensation amount according to a preset algorithm, such as a proportional-integral-derivative (PID) control algorithm. For example, to improve the optical SNR by 2 dB, it may be necessary to reduce the attenuation of the variable optical attenuation module of the current channel by X dB. The control module converts the calculated attenuation compensation amount into a specific adjustment command and sends it to the variable optical attenuation module corresponding to the currently active switch control channel. The variable optical attenuation module changes its optical attenuation according to the command, and the power and optical SNR of the output optical signal change accordingly. The control module samples again and repeats the above closed-loop process until the difference between the measured optical SNR and the absolute SNR benchmark value is less than the allowable error range. After the above independent closed-loop calibration for each wavelength, when switching to any candidate target operating wavelength, the optical signal-to-noise ratio of its stable output remains precisely constant and is completely consistent with the same absolute signal-to-noise ratio reference value.

[0060] As a result, the optical signal-to-noise ratio at different wavelengths is not only leveled out, but also precisely locked at the same target value, which can automatically compensate for the slow performance drift caused by factors such as temperature changes and device aging, and always maintain the consistency of output quality.

[0061] In some embodiments, the background noise balancing method of the optical amplification system further includes: when the ambient temperature fluctuation of the second wavelength division multiplexing module 104 causes the center wavelength of the bandpass filter window to drift, obtaining channel attenuation compensation parameters according to a preset mapping relationship; wherein, the preset mapping relationship is the mapping relationship between ambient temperature, the amount of center wavelength drift of the bandpass filter window and the channel attenuation compensation parameters; adjusting the optical attenuation of the control channel in the optical path switching module 103 according to the channel attenuation compensation parameters, so as to compensate for the optical signal attenuation caused by the center wavelength drift when the optical signal passes through the second wavelength division multiplexing module 104.

[0062] Specifically, the preset mapping relationship refers to a mathematical formula or lookup table obtained in advance through theoretical calculations or experimental calibration. It describes how much optical attenuation needs to be added or reduced in the optical path to avoid signal loss when changes in ambient temperature cause the filter window to drift. The channel attenuation compensation parameter refers to the specific value calculated based on the preset mapping relationship, which is used to guide the adjustment of the variable optical attenuation module.

[0063] Unlike the ambient temperature compensation process described in the previous embodiments, in this embodiment of the invention, when a temperature change causes a center wavelength drift in the bandpass filter window of the second wavelength division multiplexing module 104, this drift causes a change in the insertion loss of the signal light passing through. The greater the window deviation, the greater the loss. The control module obtains the current temperature of the second wavelength division multiplexing module 104 through a temperature sensor. Using a preset mapping relationship, the control module inputs the current temperature value and looks up or calculates two key results: one is how much the center wavelength of the filter window has drifted at that temperature; the other is how much additional optical signal attenuation, i.e., how many dB of power is lost, caused by this drift when the optical signal passes through the second wavelength division multiplexing module 104.

[0064] Based on the calculated additional attenuation, the control module further generates a channel attenuation compensation parameter. This parameter is designed to offset the temperature-induced power loss, requiring the upstream stage to actively reduce the corresponding amount of attenuation. For example, if temperature drift causes an additional 0.5dB of insertion loss, the compensation parameter is -0.5dB, meaning the variable optical attenuation module is required to reduce its attenuation by 0.5dB. Based on this channel attenuation compensation parameter, the control module sends an adjustment command to the variable optical attenuation module on the currently active switch control channel, causing it to adjust its optical attenuation accordingly.

[0065] Therefore, this embodiment of the invention compensates for power loss only by adjusting a variable optical attenuator, consuming almost no additional power, which is a significant advantage for spacecraft with extremely tight power budgets. It eliminates the need to add a complex temperature control module to the second wave division multiplexing module 104, simplifying the system structure and control logic. Through active compensation for attenuation, it ensures that even if the filter window drifts, the final output signal power and optical signal-to-noise ratio remain stable, thus offsetting the negative impact of temperature drift.

[0066] This invention also provides a space communication device, including an optical amplification system for balancing background noise as described in the above embodiments, and thus possesses the beneficial effects described in the above embodiments, which will not be repeated here.

[0067] Specifically, space communication equipment refers to a complete communication payload mounted on spacecraft such as satellites, space stations, or deep space probes, used to perform information exchange between space and Earth or between satellites in vacuum and extremely high and low temperature environments. The aforementioned optical amplification system for balancing background noise is integrated as a core subsystem into the space communication equipment. The optical amplification system, through its input and output fiber optic interfaces, is seamlessly connected in series in the optical transceiver link of the space communication equipment, working in conjunction with front-end or back-end equipment such as laser transceiver antennas and communication modulation / demodulation payloads.

[0068] Therefore, since the optical amplification system that balances background noise has extremely high background noise filtering capability, absolute signal-to-noise ratio equalization capability, and strong space temperature adaptability, integrating it into space communication equipment can fundamentally solve the problem of drastic signal-to-noise ratio fluctuations faced by inter-satellite multi-wavelength laser communication during wavelength switching. This enables the space communication equipment to maintain extremely high communication sensitivity and extremely low bit error rate for a long time in the complex space environment, greatly improving the communication quality and engineering application value of the entire device.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical amplification system for balancing background noise, characterized in that, It includes an optical amplification module, a first wavelength division multiplexing module, an optical path switching module, and a second wavelength division multiplexing module, which are connected in sequence via optical communication. The optical amplification module is used to amplify the input optical signal and output a mixed optical signal containing multiple candidate operating wavelengths and broadband background noise. The first wavelength division multiplexing module is used to split the mixed optical signal according to wavelength to a plurality of corresponding first split channels; The optical path switching module includes multiple switch control channels that are respectively connected to the multiple first split channels. It is used to turn on the switch control channel corresponding to the target operating wavelength according to communication requirements and physically block the other switch control channels to filter out non-target wavelength frequency band noise in the broadband background noise. The second wavelength division multiplexing module includes multiple second convergence channels that are respectively connected to the multiple switch control channels, and is used to converge multiple optical signals output by the optical path switching module into a single optical signal output; The passband bandwidth of the first split channel is greater than that of the second convergence channel, so that the second wavelength division multiplexing module can use the bandpass filter window to perform secondary filtering on the output optical signal of the optical path switching module to filter out edge noise on both sides of the center frequency of the target operating wavelength.

2. The optical amplification system for balancing background noise according to claim 1, characterized in that, Also includes: A unidirectional isolation module is connected in series between the optical amplification module and the first wavelength division multiplexing module. It is used to allow the mixed optical signal to be transmitted from the optical amplification module to the first wavelength division multiplexing module and to block the reverse return optical signal generated by the subsequent optical path.

3. The optical amplification system for balancing background noise according to claim 1, characterized in that, The first wavelength division multiplexing module includes an input terminal and multiple first shunt output terminals, and the second wavelength division multiplexing module includes multiple second shunt input terminals and a multiplexer output terminal; The optical path switching module includes optical switch units connected in series in each of the switch control channels. The input side of each unit is connected to the plurality of first shunt output terminals, and the output side is connected to the plurality of second shunt input terminals. Multiple parallel physical wavelength channels are formed between the first wavelength division multiplexing module and the second wavelength division multiplexing module.

4. The optical amplification system for balancing background noise according to claim 1, characterized in that, The passband bandwidth of the first split channel is 1.5 to 3 times that of the passband bandwidth of the second convergence channel.

5. The optical amplification system for balancing background noise according to any one of claims 1-4, characterized in that, Also includes: The signal-to-noise ratio equalization control loop includes a variable optical attenuation module and a control module for communication connection; The variable optical attenuation module is disposed on the optical signal transmission path from each of the switch control channels to each of the second convergence channels, and the control module is disposed on the single output side of the second wavelength division multiplexing module, and is used to adjust the optical attenuation of the variable optical attenuation module disposed on the corresponding conduction switch control channel according to the optical signal-to-noise ratio of the optical signal on the single output side.

6. The optical amplification system for balancing background noise according to any one of claims 1-4, characterized in that, The second wavelength division multiplexing module is equipped with a passive filter structure, and the optical amplification system further includes: The temperature adaptation compensation loop includes a temperature sensor, a control module, and a temperature control module that are connected in sequence via communication. The temperature sensor is used to acquire the ambient temperature of the second wavelength division multiplexing module. The temperature control module is attached to the second wavelength division multiplexing module. The control module is used to drive the temperature control module to heat or cool the second wavelength division multiplexing module according to the ambient temperature.

7. A method for background noise balancing in an optical amplification system, characterized in that, The method for controlling the optical amplification system with balanced background noise as described in any one of claims 1-6 includes: Obtain the wavelength switching command corresponding to the communication requirements; According to the wavelength switching command, the optical path switching module is controlled to turn on the switch control channel corresponding to the target operating wavelength and physically block the remaining switch control channels in order to filter out non-target wavelength band noise in the broadband background noise.

8. The background noise balancing method for an optical amplification system according to claim 7, characterized in that, Also includes: When the optical signal-to-noise ratio (SNR) of the single-channel output optical signal deviates from the absolute SNR reference at the current target operating wavelength, the attenuation compensation amount is obtained, and an adjustment command is sent to the variable optical attenuation module set in the corresponding current conduction switch control channel according to the attenuation compensation amount to adjust its optical attenuation amount until the optical signal-to-noise ratio of the single-channel output optical signal remains constant and consistent with the absolute SNR reference when switching to any candidate target operating wavelength.

9. The background noise balancing method for an optical amplification system according to claim 7 or 8, characterized in that, Also includes: When the ambient temperature fluctuation of the second wavelength division multiplexing module causes the center wavelength of the bandpass filter window to drift, the channel attenuation compensation parameter is obtained according to the preset mapping relationship; wherein, the preset mapping relationship is the mapping relationship between the ambient temperature, the center wavelength drift of the bandpass filter window and the channel attenuation compensation parameter; The optical attenuation of the control channel in the optical path switching module is adjusted according to the channel attenuation compensation parameter to compensate for the optical signal attenuation caused by the center wavelength drift when the optical signal passes through the second wavelength division multiplexing module.

10. A space communication device, characterized in that, Includes the optical amplification system for balancing background noise as described in any one of claims 1-6.

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