Optical amplifier and optical communication system

Abstract

The present application belongs to the technical field of optical communications. Provided are an optical amplifier and an optical communication system. The optical amplifier is an optical amplifier of three or more stages. In the optical amplifier, after a pump light provided by a pump light source enters a certain stage of amplification assembly, the remaining pump light of the stage of amplification assembly is output to another stage of amplification assembly using the pump light; and after using the received pump light, said another stage of amplification assembly outputs the remaining pump light to the next stage of amplification assembly using the pump light. In this way, the pump light is directly used, and no VOA exists on an input path of the pump light, thus preventing any degradation of the dynamic response performance of optical amplifiers.

Description

Optical amplifiers and optical communication systems

[0001] This application claims priority to Chinese patent application filed on August 29, 2024, application number 202411205437.9, entitled "Optical Amplifier and Optical Communication System", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of optical communication technology, and in particular to an optical amplifier and an optical communication system. Background Technology

[0003] In the field of optical communication, optical signals attenuate during transmission through fiber optic links. Therefore, optical amplifiers are installed in fiber optic links to compensate for transmission losses. With the increasing frequency of data transmission, the demand for low-cost, high-power optical amplifiers is becoming more and more urgent. To achieve low-cost, high-power optical amplifiers, low-cost and high-power pumps have become the preferred pump source.

[0004] In related technologies, in low-cost and high-power pumped optical amplifiers, to ensure the performance and pump conversion efficiency of the optical amplifier, the optical amplifier is generally multi-stage amplification. When implementing multi-stage amplification, the pump light output from a single high-power pump source is split into beams by a power beam splitter, and then each beam passes through a variable optical attenuator (VOA). The VOA adjusts the power of the split pump light, and then each beam is used to pump each stage of optical amplification.

[0005] In optical amplifiers, the response of the VOA is slow. Adjusting the output power of the optical amplifier through the VOA will slow down the dynamic response of the optical amplifier. Summary of the Invention

[0006] This application provides an optical amplifier and an optical communication system. The optical amplifier directly uses pump light, which does not slow down the dynamic response of the optical amplifier. The technical solution adopted is as follows:

[0007] In a first aspect, this application provides an optical amplifier comprising a pump source and N-stage amplification components connected in series, where N is greater than or equal to 3; the pump source is used to input pump light into the i-th stage amplification component of the N-stage amplification components; the i-th stage amplification component is used to amplify and output received signal light using the pump light, and to input the remaining pump light of the i-th stage amplification component into the j-th stage amplification component of the N-stage amplification components; the j-th stage amplification component is used to amplify and output received signal light using the remaining pump light of the i-th stage amplification component, and to input the remaining pump light of the j-th stage amplification component into the k-th stage amplification component of the N-stage amplification components; the k-th stage amplification component is used to amplify and output received signal light using the remaining pump light of the j-th stage amplification component, wherein i, j, and k are not equal, and i, j, and k are all greater than or equal to 1 and less than or equal to N.

[0008] In the scheme shown in this application, the optical amplifier is a three-stage or higher optical amplifier. In this optical amplifier, the pump light provided by the pump source enters a certain stage of the amplification component. The remaining pump light of that stage is output to another stage of the amplification component, which is the next component to use the pump light. After using the received pump light, the other stage of the optical amplifier outputs the remaining pump light to the next stage of the optical amplifier, which is the next component to use the pump light. In this way, the pump light is used directly, there is no VOA in the input path of the pump light, and the dynamic response of the optical amplifier is not slowed down.

[0009] In one alternative approach, the i-th stage amplification component is the first stage amplification component, and the j-th stage amplification component is the last stage amplification component. In this way, the pump light first enters the first stage amplification component, where the pump light is relatively abundant, maintaining a high population inversion and gain. This results in low noise in the first stage amplification component, leading to a low noise figure (NF), which reflects the magnitude of the optical amplifier's noise. Furthermore, the signal light power is relatively low in the first stage amplification component, resulting in less pump light consumption and a larger amount of remaining pump light input to the last stage amplification component. In the last stage amplification component, the signal light power is high, and more pump light is consumed, ensuring sufficient signal light gain.

[0010] In one alternative approach, in the first-stage amplification component, the pump light and signal light propagate in the same direction and both enter the gain fiber immediately, generating no noise. The pump light amplifies the signal light, and since the power of the signal light is greater than the power of the noise, the noise gain is suppressed, thus reducing noise amplification. Furthermore, because the signal light and pump light propagate in the same direction, pump light consumption is relatively low, allowing more pump light to remain in the final amplification component, ensuring the signal light gain.

[0011] In one alternative approach, the signal light undergoes multiple amplification stages before reaching the final amplification stage, resulting in high signal light power and high pump light consumption in the final stage. This significantly impacts the pump conversion efficiency due to the optical path design. By employing a reverse pumping method where the pump light and signal light propagate in opposite directions, the saturation effect is reduced, and the pump conversion efficiency is improved.

[0012] In one alternative approach, when N equals 3, the i-th amplification component is the first-stage amplification component, the j-th amplification component is the last-stage amplification component, and the k-th amplification component is the second-stage amplification component. Each amplification component includes multiple sub-amplification components. This effectively divides the optical amplifier into three amplification regions: the region containing the first-stage amplification component, the region containing the second-stage amplification component, and the region containing the last-stage amplification component. These three amplification regions are arranged along the transmission direction of the signal light. The pump light output from the pump source is preferentially used in the first region, then in the last region, and finally in the middle region. Within each region, the multiple sub-amplification components are used sequentially. This ensures that the pump light preferentially enters the first region, resulting in sufficient pump light. The population inversion of each sub-amplification component in the first region remains at a high level, and the gain remains high, leading to lower noise and a lower noise figure in the first region. Moreover, in the first region, the signal light power is relatively small, and the pump light consumption is relatively low. There is a lot of remaining pump light in the first region, which is input to the last region. In the last region, the signal light power is high, and more pump light is consumed, which can ensure the signal light gain.

[0013] In an alternative embodiment, to flexibly adjust the power of the output signal light, the optical amplifier further includes a power adjustment component located between two adjacent sub-amplifiers of the last stage amplification component. This power adjustment component is used to attenuate the power of the received signal light.

[0014] In the scheme shown in this application, the signal light has been amplified before the last stage amplification component. The power adjustment component is set in the two adjacent sub-amplification components of the last stage amplification component to attenuate the signal light, thereby attenuating more noise in the same proportion.

[0015] In one alternative embodiment, the optical amplifier also includes an isolator and gain flattening filters (GFFs). An isolator and a GFF are provided after each sub-amplifier in each amplification stage. The isolator prevents the back-transmitted optical signal from returning to the optical amplification stage, and the GFF performs flattening filtering on the amplified signal light.

[0016] In an alternative embodiment, the k-th stage amplification component is further configured to, if the k-th stage amplification component is not the last amplification component to use pump light, output the remaining pump light of the k-th stage amplification component to the next amplification component to use pump light.

[0017] In one alternative approach, the pump light output from the pump source is first used by the first-stage amplification component. The first-stage amplification component then outputs the remaining pump light to the last-stage amplification component. When the last-stage amplification component outputs the remaining pump light, there is still a relatively large amount of remaining pump light, which is preferentially used by the preceding amplification components. In the preceding amplification components, the population inversion degree is maintained at a high level, and the gain is maintained at a high level, resulting in relatively low noise in the preceding amplification components, thereby making the noise figure of the optical amplifier relatively low.

[0018] In one alternative approach, to couple pump light to the gain fiber and guide it to the next amplification component using the pump light, each amplification component in the N-stage amplification system, excluding the last amplification component to use the pump light, includes a pump input module, a pump output module, and a gain fiber. For each amplification component, the pump input module inputs the received pump light into the gain fiber within that amplification component, and the pump output module outputs any remaining pump light from the gain fiber. Thus, the pump input module can be used to couple pump light to the gain fiber, and the pump output module can be used to guide any remaining pump light to the next amplification component using the pump light.

[0019] In one alternative approach, both the pump export module and the pump import module are wavelength division multiplexing (WDM) modules.

[0020] In one alternative approach, in the optical amplifier, an isolator and a GFF are provided between two adjacent amplification stages in the N-stage amplification component. The isolator can prevent the back-transmitted optical signal from returning to the optical amplification component, and the GFF can perform flat filtering on the amplified signal light.

[0021] In one alternative approach, to flexibly adjust the power of the pump light output from the pump source, a controller is incorporated into the optical amplifier. This controller controls the power of the pump light output from the pump source. An input detector is positioned on the input path of the first-stage amplification component of the optical amplifier to detect the first power of the signal light input to the first-stage amplification component. An output detector is positioned on the output path of the last-stage amplification component to detect the second power of the signal light output from the last-stage amplification component. The controller adjusts the power of the pump light output from the pump source based on the first and second power values.

[0022] In a second aspect, this application provides an optical communication system comprising a transmitting device, a receiving device, and one or more optical amplifiers as described in the first aspect or any optional embodiment of the first aspect, the optical amplifiers being located between the transmitting device and the receiving device. Attached Figure Description

[0023] Figure 1 is a schematic diagram of the structure of a communication system provided in an exemplary embodiment of this application;

[0024] Figure 2 is a schematic diagram of a structure of an optical amplifier provided in an exemplary embodiment of this application;

[0025] Figure 3 is a schematic diagram of the structure of a forward-pumped amplification component provided in an exemplary embodiment of this application;

[0026] Figure 4 is a schematic diagram of the structure of a backward-pumped amplification component provided in an exemplary embodiment of this application;

[0027] Figure 5 is a schematic diagram of a three-stage optical amplifier provided in an exemplary embodiment of this application;

[0028] Figure 6 is a schematic diagram of the structure of a four-stage optical amplifier provided in an exemplary embodiment of this application;

[0029] Figure 7 is a schematic diagram of another structure of a three-stage optical amplifier provided in an exemplary embodiment of this application;

[0030] Figure 8 is a schematic diagram of another structure of a three-stage optical amplifier provided in an exemplary embodiment of this application;

[0031] Figure 9 is a schematic diagram of another structure of a three-stage optical amplifier provided in an exemplary embodiment of this application;

[0032] Figure 10 is a schematic diagram of another structure of an optical amplifier provided in an exemplary embodiment of this application;

[0033] Figure 11 is a schematic diagram of another structure of an optical amplifier provided in an exemplary embodiment of this application;

[0034] Figure 12 is a schematic diagram of another structure of an optical amplifier provided in an exemplary embodiment of this application;

[0035] Figure 13 is a schematic diagram of another structure of an optical amplifier provided in an exemplary embodiment of this application;

[0036] Figure 14 is a schematic diagram of the performance of an optical amplifier provided in an exemplary embodiment of this application;

[0037] Figure 15 is another performance schematic diagram of an optical amplifier provided in an exemplary embodiment of this application.

[0038] Illustration

[0039] 1. Pump light source; 2. N-stage amplification assembly; 3. Power adjustment assembly; 4. Isolator; 5. GFF;

[0040] 6. Input detector; 7. Output detector; 8. Controller. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0042] Optical amplifiers are widely used in optical communication, primarily to compensate for transmission loss in optical fibers, enabling long-distance transmission. Furthermore, with the adoption of fiber optic communication between data centers, the demand for low-cost, high-power optical amplifiers is becoming increasingly urgent. In these amplifiers, low-cost and high-power pumping has become the preferred pumping solution. In addition, to ensure the performance and pump conversion efficiency of optical amplifiers, they are generally multi-stage amplifiers. Therefore, how to solve the problem of using high-power pumping in multi-stage optical amplifiers has become a key technical bottleneck for high-power optical amplifiers.

[0043] Based on this, embodiments of this application provide an optical amplifier, which is a three-stage or higher optical amplifier. In this optical amplifier, the pump light provided by the pump source first enters a certain stage of the amplification component. After using the pump light, the stage amplification component outputs the remaining pump light to another stage of the optical amplification component that uses the pump light. This next stage of the optical amplification component uses the received pump light and then outputs the remaining pump light to yet another stage of the optical amplification component that uses the pump light, until all stages of the amplification component use the pump light. In this way, the pump light is used directly in each stage of the amplification component, there is no VOA in the input path of the pump light, and it does not slow down the dynamic response of the optical amplifier.

[0044] The optical amplifier provided in this application embodiment can be applied to an optical communication system. As shown in FIG1, the optical communication system includes a transmitting device, a receiving device, and an optical amplifier. The optical amplifier is located between the transmitting device and the receiving device and is used to amplify the optical signal transmitted between the transmitting device and the receiving device. The transmitting device and the optical amplifier are connected through an optical fiber, and the receiving device and the optical amplifier are connected through an optical fiber.

[0045] Optionally, the transmitting and receiving devices are located in different data centers. For example, the transmitting device is an optical transport network device in data center A, used to connect to the switches in data center A, and the receiving device is an optical transport network device in data center B, used to connect to the switches in data center B. The switches in each data center are connected to the servers in the data center.

[0046] Optionally, the transmitting and receiving devices are located in the backbone network.

[0047] Optionally, there may be one or more optical amplifiers between the transmitting and receiving devices.

[0048] Optionally, the optical amplifier is positioned near the transmitting device to increase the power of the output optical signal of the transmitting device, or the optical amplifier is positioned near the receiving device to amplify the optical signal to improve the quality of the optical signal received by the receiving device, or the optical amplifier is positioned between the transmitting device and the receiving device to compensate for the transmission loss of the transmission fiber. This intermediate position may not be an absolute center position and may deviate from the center position. Figure 1 shows the optical amplifier positioned near the transmitting device.

[0049] In this application embodiment, the optical amplifier is a general optical amplifier, including but not limited to conventional (C) band and long (L) band optical amplifiers.

[0050] Figure 2 provides a schematic diagram of the optical amplifier. As shown in Figure 2, the optical amplifier includes a pump light source 1 and N-stage amplification components 2 connected in series, where N is greater than or equal to 3. The N-stage amplification components 2 include a first-stage amplification component to an Nth-stage amplification component, with the Nth-stage amplification component being the last stage amplification component. After the signal light enters the optical amplifier, it passes through the first-stage amplification component to the Nth-stage amplification component in sequence. That is to say, the arrangement order of the first-stage amplification component to the Nth-stage amplification component is along the transmission direction of the signal light.

[0051] Pump source 1 is connected to the i-th stage amplification component, where i is greater than or equal to 1 and less than or equal to N. Pump source 1 inputs pump light to the i-th stage amplification component, which amplifies and outputs the received signal light using the pump light. The remaining pump light from the i-th stage amplification component is input to the j-th stage amplification component. The j-th stage amplification component is different from the i-th stage amplification component. The remaining pump light of the i-th stage amplification component is all or part of the unused pump light received by the i-th stage amplification component. The j-th stage amplification component amplifies and outputs the received signal light using the received pump light. The j-th stage amplification component inputs its remaining pump light to the k-th stage amplification component. The k-th stage amplification component is different from both the j-th and i-th stage amplification components. The remaining pump light of the j-th stage amplification component is all or part of the unused pump light received by the j-th stage amplification component. The k-th stage amplification component amplifies and outputs the received signal light using the received pump light. Here, after a certain stage of amplification amplifies the signal light using the received pump light, if this stage of amplification is not the last stage of amplification, it outputs the amplified signal light to the next stage of amplification. If this stage of amplification is the last stage of amplification, the amplified signal light output will be output from the optical amplifier.

[0052] In the case where N equals 3, the k-th stage amplification component is the last amplification component in stage N2 to use the pump light, and it does not need to be exported after using the pump light. The amplification component that last uses the pump light refers to the amplification component that last receives the pump light.

[0053] When N is greater than 3, if the k-th stage amplification component is not the last amplification component in stage N2 to use pump light, its remaining pump light is output to the s-th stage amplification component. The s-th stage amplification component uses the received pump light to amplify the received signal light. The remaining pump light of the k-th stage amplification component is all or part of the unused pump light received by the k-th stage amplification component. If the s-th stage amplification component is the last amplification component to use pump light, the pump light consumption is almost complete, and there is no need to output it again. If the s-th stage amplification component is not the last amplification component to use pump light, then the s-th stage amplification component outputs its remaining pump light to the next amplification component for use. This next amplification component is the next amplification component to use pump light.

[0054] It should be noted that, in the above description, if the remaining pump light is all unused pump light, there may be some residue of this unused pump light due to device or other reasons during the extraction process, but this situation is also within the scope of protection of this application.

[0055] It should also be noted that, using the optical amplifier shown in Figure 2, after the pump light enters a certain stage of the amplification component, the remaining pump light is exported to the next amplification component that uses the pump light. Instead, a beam splitter is not used to supply multiple stages of the amplification component at the same time.

[0056] In an alternative embodiment, Figures 3 and 4 provide schematic diagrams of the amplification assembly. Figure 3 is a schematic diagram of co-directional pumping, also known as forward pumping, and Figure 4 is a schematic diagram of reverse pumping, also known as backward pumping. For each stage of the N-stage amplification assembly 2, excluding the amplification assembly that uses pump light last, the amplification assembly includes a pump inlet module, a pump outlet module, and a gain fiber. The gain fiber is located between the pump inlet module and the pump outlet module. The pump inlet module receives the pump light from the current amplification assembly and couples the pump light into the gain fiber of the current amplification assembly. The signal light and the pump light are transmitted in the gain fiber. The signal light is amplified and output. The remaining pump light is output to the pump outlet module, which then outputs the remaining pump light to the next amplification assembly that uses pump light. The pump inlet module of this amplification assembly couples the remaining pump light into the gain fiber.

[0057] In a certain stage of amplification, if the amplification component is unidirectionally pumped, the pump input module combines the signal light and the pump light into a single beam and inputs it into the gain fiber. The pump output module continues to output the signal light forward and outputs the remaining pump light. If the amplification component is reversely pumped, the pump input module inputs the pump light into the gain fiber and outputs the signal light amplified by the gain fiber. The pump output module inputs the signal light into the gain fiber and outputs the remaining pump light output from the gain fiber.

[0058] Optionally, both the pump import module and the pump export module are WDM.

[0059] Optionally, the gain fiber is a doped fiber and / or a Raman fiber, wherein the doped fiber is erbium-doped fiber (EDF) or ytterbium-doped fiber, etc. When the gain fiber is erbium-doped fiber, the optical amplifier is an erbium-doped fiber amplifier (EDFA). When the gain fiber is ytterbium-doped fiber, the optical amplifier is a ytterbium-doped fiber amplifier.

[0060] Optionally, the amplification component that uses the pump light last includes a pump inlet module and a gain fiber, but does not include a pump outlet module, since it does not need to export the pump light.

[0061] Optionally, the amplification component that uses the pump light last may also include a pump output module, which outputs the remaining pump light from the amplification component back to the amplification component for continued use.

[0062] In an alternative approach, Figures 5 and 6 provide another structural schematic diagram of the optical amplifier. Figure 5 is a structural schematic diagram of a three-stage optical amplifier, and Figure 6 is a structural schematic diagram of a four-stage optical amplifier. As shown in Figures 5 and 6, the i-th stage amplification component is the first stage amplification component, the j-th stage amplification component is the last stage amplification component, and the last stage amplification component is the N-th stage amplification component.

[0063] In an optical amplifier, according to the formula for the noise figure of a multi-stage optical amplifier (see formula (1)), the noise figure of the optical amplifier is mainly determined by the noise figure of the first-stage amplification component. In each stage amplification component, the noise figure NF is inversely related to the population inversion and the gain, see formulas (2) and (3). Here, the pump light first enters the first-stage amplification component. The pump light of the first-stage amplification component is sufficient, so that the population inversion is kept at a high level and the gain is kept at a high level. According to formula (3), the noise of the first-stage amplification component is relatively small and the noise figure is low, so the overall noise figure of the optical amplifier is low. Moreover, in the first-stage amplification component, the signal light power is relatively small and the pump light consumption is relatively small. The remaining pump light of the first-stage amplification component is relatively large and output to the last stage amplification component. In the last stage amplification component, the signal light power is large and the pump light consumption is also large, which can ensure the gain. The gain is used to reflect the amplification factor of the optical amplifier and is equal to the output logarithmic optical power minus the input logarithmic optical power.

[0064] In formula (1), the noise figure of the multistage amplifier is NF. 总 L a G is the insertion loss of the a-th amplification component. a Let NF be the gain of the a-th amplification component. a It is the noise figure of the a-th stage amplification component, expressed as formula (2), where the value of a ranges from 1 to N.

[0065] In formula (2), P ASE To amplify the power of spontaneously emitted (ASE) light, P ASE =2n sp hvB(G a -1), n sp is the spontaneous emission coefficient, which is inversely correlated with the population inversion degree, h is Planck's constant, v is the center frequency of the signal light, and B is the spectral width of the signal light. Therefore, formula (2) can be converted into formula (3).

[0066] Optionally, the pump light and signal light input to the first-stage amplification component are transmitted in the same direction, indicating that the first-stage amplification component is unidirectionally pumped. In this way, in the first-stage amplification component, the signal light and pump light enter the gain fiber simultaneously. No noise is generated immediately upon entering the gain fiber. The pump light is used to amplify the signal light, and the power of the signal light is greater than the power of the noise, thus suppressing the noise gain and reducing noise amplification. Furthermore, since the signal light and pump light transmit in the same direction, less pump light is consumed, leaving more pump light for the final amplification component, ensuring the signal light gain. In this case, other amplification components can be unidirectionally pumped or counter-directionally pumped; this embodiment does not limit this. For example, Figures 7 and 8 provide schematic diagrams of a three-stage optical amplifier. In Figure 7, the final amplification component is counter-directionally pumped, and in Figure 8, the final amplification component is unidirectionally pumped.

[0067] Optionally, as shown in Figure 7, the signal light has already been amplified by multiple stages of amplification before reaching the final stage amplification component. This results in relatively high power of the signal light input to the final stage amplification component, leading to significant pump consumption. Therefore, the optical path design has a substantial impact on the pump conversion efficiency. Co-directional pumping suffers from low pump conversion efficiency due to saturation effects. In the final stage amplification component, the signal light and pump light propagate in opposite directions, employing reverse pumping. This weakens the saturation effect and improves the pump conversion efficiency. In this case, the other stages of amplification can be either co-directional or reverse pumped; this embodiment does not impose limitations.

[0068] In one alternative approach, when N is greater than 3, pump light source 1 outputs pump light, which first enters the first-stage amplification component. The remaining pump light output from the first-stage amplification component is input to the last-stage amplification component, the remaining pump light output from the last-stage amplification component is input to the second-stage amplification component, the remaining pump light output from the second-stage amplification component is input to the third-stage amplification component, and so on, until the penultimate amplification component uses pump light to amplify the signal light. For example, as shown in Figure 6, the i-th stage amplification component is the first-stage amplification component, the j-th stage amplification component is the last-stage amplification component, the k-th stage amplification component is the second-stage amplification component, and the s-th stage amplification component is the third-stage amplification component. In this way, the remaining pump light output from the last-stage amplification component is preferentially supplied to the preceding amplification components. The pump light in the preceding amplification components is relatively sufficient, which keeps the population inversion at a high level and the gain at a high level, resulting in lower noise in the preceding amplification components and thus a lower overall noise figure of the optical amplifier.

[0069] Alternatively, when N is greater than 3, pump light source 1 outputs pump light, which first enters the first-stage amplification component. The remaining pump light output from the first-stage amplification component is input to the last-stage amplification component, the remaining pump light output from the last-stage amplification component is input to the penultimate-stage amplification component, the remaining pump light output from the penultimate-stage amplification component is input to the third-to-last-stage amplification component, and so on, until the second-stage amplification component uses the pump light to amplify the signal light. In this way, the signal light input to the later amplification components has higher power and absorbs more pump light, which can ensure the gain of the signal light.

[0070] In an alternative embodiment of this application, in some cases, the signal light should not be too strong when transmitted through the optical fiber. The optical amplifier can further attenuate the signal light. Figure 9 provides another schematic diagram of the optical amplifier structure. As shown in Figure 9, the optical amplifier also includes a power adjustment component 3, located between the penultimate amplification stage and the last amplification stage, i.e., between the (N-1)th and Nth amplification stages. The power adjustment component 3 is used to attenuate the power of the received optical signal. Thus, after passing through the (N-1)th amplification stage, the signal light has already been amplified to a relatively high level. At this point, attenuating the signal light at the same attenuation ratio allows for the attenuation of more signal light and more noise.

[0071] Optionally, the power adjustment component 3 includes a first coupler, a first detector, a VOA, a second coupler, and a second detector. The first coupler is connected to the (N-1)th stage amplification component and the first detector, the second coupler is connected to the Nth stage amplification component and the second detector, and the VOA is located between the first coupler and the second coupler. The first coupler allocates a portion of the received optical signal to the first detector according to a preset ratio and outputs the remaining optical signal to the VOA. The first detector detects the power of the received optical signal to obtain power A. The VOA attenuates the received optical signal and outputs it to the second coupler. The second coupler allocates a portion of the received optical signal to the second detector according to a preset ratio and outputs the remaining optical signal to an adjacent amplification component. The second detector detects the power of the optical signal to obtain power B. The attenuation amplitude of the VOA is determined based on the ratio of power A to power B. For example, when the ratio of power A to power B is large, the attenuation amplitude of the VOA is decreased; when the ratio of power A to power B is small, the attenuation amplitude of the VOA is increased.

[0072] The preset ratio can be set according to actual needs, such as a preset ratio of 5%.

[0073] Optionally, both the first detector and the second detector are photodetectors (PDs).

[0074] In an alternative embodiment, the optical amplifier may also include other components, including but not limited to multiple isolators 4 and multiple GFF5. Figure 10 provides another schematic diagram of the optical amplifier structure. As shown in Figure 10, isolators 4 and GFF5 are located between two adjacent amplification stages. An isolator 4, placed after a certain amplification stage, is used to prevent the back-transmitted optical signal from returning to that stage, and GFF5 is used to perform gain flattening filtering on the received signal light.

[0075] Optionally, the arrangement order of isolators 4 and GFF5 is the same as or opposite to the transmission direction of the signal light.

[0076] In one alternative approach, as described above, each amplification stage performs one level of amplification, and at least one subsequent amplification stage contains multiple levels of amplification. Specifically, when N equals 3, in the N-stage amplification stage, each stage represents a logical amplification region. The i-th stage amplification stage is the first stage, the j-th stage is the last stage, and the k-th stage is the second stage. At least one stage in the three-stage amplification system includes multiple sub-amplifiers. If at least one stage includes only one stage amplification, that stage is not the second stage. The following explanation uses the example of each stage amplification stage including multiple sub-amplifiers. Figure 11 provides another schematic diagram of the optical amplifier's structure, showing an output where each stage amplification stage includes two sub-amplifiers. This effectively divides the optical amplifier into multiple amplification regions, performing at least one level of amplification in each region.

[0077] Pump source 1 is connected to the m-th sub-amplifier in the first-stage amplification component. Pump source 1 inputs pump light to the m-th sub-amplifier. The m-th sub-amplifier uses the pump light to amplify and output the received signal light, and outputs the remaining pump light to the n-th sub-amplifier. The n-th sub-amplifier belongs to the first-stage amplification component. The remaining pump light is the remaining pump light in the m-th sub-amplifier. The m-th sub-amplifier is different from the n-th sub-amplifier. Both m and n are less than or equal to the order of the sub-amplifier in the first-stage amplification component.

[0078] The nth-stage sub-amplifier uses the received pump light to amplify and output the received signal light. In the first-stage amplifier, if the nth-stage sub-amplifier is the last sub-amplifier to use the pump light, the remaining pump light is output to the dth-stage sub-amplifier in the last stage amplifier. If the nth-stage sub-amplifier is not the last sub-amplifier to use the pump light, the remaining pump light is output to the next sub-amplifier in the first-stage amplifier to use the pump light.

[0079] The d-th stage sub-amplifier is the first sub-amplifier in the last stage amplification assembly to use pump light. It amplifies and outputs the received signal light using the received pump light, and also outputs residual pump light to the f-th stage sub-amplifier in the last stage amplification assembly. This residual pump light is the residual pump light of the d-th stage sub-amplifier. The d-th stage sub-amplifier is different from the f-th stage sub-amplifier. The f-th stage sub-amplifier amplifies and outputs the received signal light using the received pump light. In the last stage amplification assembly, if the f-th stage sub-amplifier is the last sub-amplifier to use pump light, it outputs residual pump light to the second stage amplification assembly. If the f-th stage sub-amplifier is not the last sub-amplifier to use pump light, it outputs residual pump light to the next sub-amplifier in the last stage amplification assembly to use pump light. This residual pump light is the residual pump light of the f-th stage sub-amplifier. Both d and f are less than or equal to the order of the sub-amplifiers in the last stage amplification assembly.

[0080] The h-th sub-amplifier in the second-stage amplification assembly receives the remaining pump light from the last-stage amplification assembly, amplifies the received signal light using the received pump light, and outputs it. In the second-stage amplification assembly, if the h-th sub-amplifier is the last sub-amplifier to use the pump light, it no longer outputs the remaining pump light. If the h-th sub-amplifier is not the last sub-amplifier to use the pump light, it outputs the remaining pump light to the next sub-amplifier in the second-stage amplification assembly that uses the pump light. This remaining pump light is the remaining pump light of the h-th sub-amplifier, and d is less than or equal to the stage of the sub-amplifier in the second-stage amplification assembly.

[0081] In this way, pump light source 1 first inputs pump light to the first-stage amplification component, then to the last-stage amplification component, and finally to the second-stage amplification component. As described above, the population inversion of the first-stage amplification component is maintained at a high level, and the gain of the first-stage amplification component is also maintained at a high level. Thus, the noise of the first-stage amplification component is relatively small, and the noise figure is low. Moreover, the power of the signal light in the first-stage amplification component is low, the pump light consumption is low, and there is a lot of pump light remaining. When it is input to the last-stage amplification component, the signal light power is high, the pump light consumption is high, and the signal light is amplified more, thereby ensuring the gain.

[0082] Optionally, in the first-stage amplification component, the m-th stage sub-amplifier is the first-stage sub-amplifier, and the n-th stage sub-amplifier is the second-stage sub-amplifier. That is, in the first-stage amplification component, the pump light is used sequentially along the transmission direction of the signal light. In this way, by first inputting the pump light into the first-stage sub-amplifier, sufficient pump light is provided, maintaining a high population inversion and gain level in the first-stage sub-amplifier, resulting in relatively low noise and a low noise figure.

[0083] Optionally, in the second-stage amplification component, the h-th sub-amplifier component is the first-stage sub-amplifier component, and the sub-amplifier component that uses the pump light next is the second-stage sub-amplifier component. That is, in the second-stage amplification component, the pump light is used in the order of the signal light transmission direction. In this way, the pump light is first input into the first-stage sub-amplifier component, resulting in relatively low noise. After the signal light is amplified, the noise can be suppressed.

[0084] Alternatively, in the second-stage amplification assembly, the h-th sub-amplifier is the last sub-amplifier, and the sub-amplifier that uses the pump light next is the penultimate sub-amplifier. That is, in the second-stage amplification assembly, the pump light is used in the reverse order of the signal light transmission direction. In this way, by inputting the pump light first into the last sub-amplifier, the signal light power is high, consuming more pump light, thus ensuring gain.

[0085] Optionally, in the last stage amplification component, the d-th sub-amplifier is the last stage, and the f-th sub-amplifier is the penultimate stage. This means that in the last stage, the pump light is used in the reverse order of the signal light transmission direction. By inputting the pump light into the last stage sub-amplifier first, the signal light power is relatively high, and more pump light is consumed. This not only ensures gain but also improves pump conversion efficiency.

[0086] Optionally, in the first and second stage amplification components, each sub-amplifier is pumped in the same direction. In the final stage amplification component, each sub-amplifier is pumped in the opposite direction.

[0087] Alternatively, in the first-stage amplification assembly, all sub-amplifiers are pumped in the same direction. In the second-stage and final-stage amplification assemblies, all sub-amplifiers are pumped in opposite directions.

[0088] Optionally, in some embodiments of this application, the signal light should not be too strong when transmitted in the optical fiber. The optical amplifier can also attenuate the signal light. The optical amplifier further includes a power adjustment component 3, which is located in the last stage amplification component and between two adjacent sub-amplifier stages. For example, as shown in FIG12, in the last stage amplification component, the power adjustment component 3 is located between the last sub-amplifier stage and the penultimate sub-amplifier stage. As another example, in the last stage amplification component, the power adjustment component 3 is located between the penultimate and third-to-last sub-amplifier stages.

[0089] The function and structure of the power adjustment component 3 are described above and will not be repeated here.

[0090] Optionally, the optical amplifier also includes multiple isolators 4 and GFF5, located after each sub-amplifier assembly. The functions of isolators 4 and GFF5 have been described above and will not be repeated here.

[0091] Optionally, each sub-amplifier stage, except for the last one to use pump light, includes a pump input module, a pump output module, and a gain fiber. The gain fiber, which is doped fiber and / or Raman fiber, is located between the pump input module and the pump output module. The pump input module receives the pump light from the current sub-amplifier stage and couples it into the gain fiber of that stage. The signal light and pump light propagate in the gain fiber, the signal light is amplified and output, and the remaining pump light is output to the pump output module. The pump output module then outputs this remaining pump light to the next sub-amplifier stage that uses pump light. The pump input module in this sub-amplifier stage couples the received pump light into the gain fiber. The usage of the pump input and pump output modules is described above and will not be repeated here.

[0092] In one alternative approach, the pump source 1 is any high-power laser. The wavelength of the pump light output from the pump source 1 is determined by the wavelength of the signal light to be pumped.

[0093] Optionally, the pump source 1 may include one or more sub-sources. When the pump light power requirement is particularly high, the pump source 1 may include multiple sub-sources 1. In the case where the pump source 1 includes multiple sub-sources, the pump light output from the multiple sub-sources is combined into a single beam and input to the i-th stage amplification component. Alternatively, each sub-source can be used as a pump source for a portion of the amplification component. For example, the pump source 1 includes a first sub-source and a second sub-source. The first sub-source is responsible for the first half of the amplification component, and the second sub-source is responsible for the second half of the amplification component. The process of the first sub-source pumping the first half of the amplification component is the same as the pumping method described above, and the process of the second sub-source pumping the second half of the amplification component is also the same as the pumping method described above.

[0094] In an alternative embodiment of this application, the power of the pump light can also be adjusted in the optical amplifier. Figure 13 provides another schematic diagram of the optical amplifier structure. As shown in Figure 13, the optical amplifier further includes an input detector 6, an output detector 7, and a controller 8. The input detector 6 includes a third coupler and a third detector, and the output detector 7 includes a fourth coupler and a fourth detector. The third coupler and the third detector are connected via optical fiber, and the fourth coupler and the fourth detector are also connected via optical fiber. Both the third and fourth detectors are connected to the controller 8, and the pump light source 1 is also connected to the controller 8. The third coupler is located on the input path of the first-stage amplification component, and the fourth coupler is located on the output path of the last-stage amplification component.

[0095] The third coupler splits the input optical amplifier's signal light into a first signal beam and a second signal beam. The power of the first signal beam is greater than that of the second signal beam. The first signal beam is output to the first-stage amplification component, and the second signal beam is output to the third detector. The third detector converts the second signal beam into an electrical signal and determines its power to obtain the power of the second signal beam. Thus, since the second signal beam is obtained by splitting the input optical amplifier's signal light according to a certain ratio, the logarithmic power of the first signal beam, i.e., the first power, can be obtained.

[0096] The fourth coupler splits the signal light output from the last stage amplifier into a third and a fourth signal light beam. The power of the third signal light beam is greater than that of the fourth signal light beam. The third signal light beam is output, while the fourth signal light beam is output to the fourth detector. The fourth detector converts the fourth signal light beam into an electrical signal and determines the power of the electrical signal to obtain the power of the fourth signal light beam. Thus, since the fourth signal light beam is obtained by splitting the signal light output from the last stage amplifier stage according to a certain ratio, the logarithmic power of the third signal light beam, i.e., the second power, can be obtained.

[0097] Based on the difference between the first power and the second power, controller 8 determines the gain of the optical amplifier. Then, using this gain, and within the correspondence between gain and pump light power, it determines the power of the pump light output by pump source 1 and adjusts the power of the pump light output by pump source 1. In this way, by detecting the gain of the optical amplifier, the power of the pump light can be adjusted, thereby ensuring that the gain of the optical amplifier meets the requirements.

[0098] Optionally, both the third and fourth detectors are PDs (Power Distribution Devices).

[0099] Furthermore, to better illustrate the beneficial effects of the embodiments of this application, a prototype experiment was conducted on the optical amplifier using the structure shown in Figure 8. The gain range of the optical amplifier was 23–32 dB, and the output power was 22.5 dBm. Figure 14 shows the gain and noise figure spectrum of the optical amplifier when the pump light output power of pump source 1 is 1.4 W. As can be seen from Figure 14, the noise figure (NF) is less than 4.2 dB throughout the entire C-band range. In addition, the single-wave performance of the optical amplifier was also tested. The gain and noise figure under single-wave conditions are shown in Figure 15, and the single-wave noise figure is less than 6 dB.

[0100] It should be noted that, in the embodiments of this application, the signal light may include optical signals of one or more wavelengths.

[0101] It should also be noted that there are many combinations of solutions in the embodiments of this application, and it is impossible to list them all. The above solutions can be combined arbitrarily without violating the essence of the solution.

[0102] In this application, the terms "first" and "second," etc., are used to distinguish identical or similar items that have substantially the same function and purpose. It should be understood that there is no logical or temporal dependency between "first" and "second," nor does it limit the quantity or order of execution. It should also be understood that although the following description uses the terms "first" and "second," etc., to describe various elements, these elements should not be limited by the terms. These terms are merely used to distinguish one element from another. For example, without departing from the scope of various examples, a first detector can be referred to as a second detector, and similarly, a second detector can be referred to as a first detector. Both a first detector and a second detector can be detectors, and in some cases, they can be separate and different detectors.

[0103] In this application, the term "at least one" means one or more, and the term "multiple" means two or more.

[0104] The above description is merely an exemplary embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and such modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An optical amplifier, characterized in that, It includes a pump light source (1) and an N-stage amplifier assembly (2) connected in series, where N is greater than or equal to 3; The pump light source (1) is used to input pump light into the i-th stage amplification component in the N-stage amplification component (2); The i-th stage amplification component is used to amplify and output the received signal light using the pump light, and to input the remaining pump light of the i-th stage amplification component into the j-th stage amplification component in the N-th stage amplification component (2); The j-th stage amplification component is used to amplify and output the received signal light using the remaining pump light of the i-th stage amplification component, and to input the remaining pump light of the j-th stage amplification component into the k-th stage amplification component in the N-th stage amplification component (2). The k-th stage amplification component is used to amplify and output the received signal light using the remaining pump light of the j-th stage amplification component, where i, j, and k are not equal, i, j, and k are all greater than or equal to 1, and less than or equal to N.

2. The optical amplifier according to claim 1, characterized in that, The i-th amplification component is the first-stage amplification component, and the j-th amplification component is the last-stage amplification component.

3. The optical amplifier according to claim 2, characterized in that, The pump light and signal light input to the first-stage amplification component are transmitted in the same direction.

4. The optical amplifier according to claim 2 or 3, characterized in that, The pump light and signal light input to the last stage amplification component are transmitted in opposite directions.

5. The optical amplifier according to claim 1, characterized in that, N equals 3, the i-th amplification component is the first amplification component, the j-th amplification component is the last amplification component, the k-th amplification component is the second amplification component, and each amplification component includes multiple sub-amplification components; The m-th sub-amplifier in the first-stage amplification assembly is used to amplify and output the received signal light using the pump light output by the pump light source (1), and to output the remaining pump light of the m-th sub-amplifier to the n-th sub-amplifier in the first-stage amplification assembly. The nth-stage sub-amplifier is used to amplify and output the received signal light using the received pump light. If the nth-stage sub-amplifier is the last sub-amplifier in the first-stage amplifier to use the pump light, it outputs the remaining pump light of the nth-stage sub-amplifier to the dth-stage sub-amplifier in the last-stage amplifier. If the nth-stage sub-amplifier is not the last sub-amplifier in the first-stage amplifier to use the pump light, it outputs the remaining pump light of the nth-stage sub-amplifier to the next sub-amplifier in the first-stage amplifier to use the pump light. The d-th stage sub-amplifier is used to amplify and output the received signal light using the received pump light, and to output the remaining pump light of the d-th stage sub-amplifier to the f-th stage sub-amplifier in the last stage amplifier. The f-th stage sub-amplifier is used to amplify and output the received signal light using the received pump light. If the f-th stage sub-amplifier is the last sub-amplifier in the last stage amplification assembly to use the pump light, it outputs the remaining pump light of the f-th stage sub-amplifier to the second stage amplification assembly. If the f-th stage sub-amplifier is not the last sub-amplifier in the last stage amplification assembly to use the pump light, it outputs the remaining pump light of the f-th stage sub-amplifier to the next sub-amplifier in the last stage amplification assembly to use the pump light.

6. The optical amplifier according to claim 5, characterized in that, The optical amplifier also includes a power adjustment component (3); The power adjustment component (3) is located between two adjacent sub-amplifiers of the last stage amplifier component; The power adjustment component (3) is used to attenuate the power of the received signal light.

7. The optical amplifier according to any one of claims 1 to 4, characterized in that, The k-th stage amplification component is further configured to, when the k-th stage amplification component is not the last amplification component to use pump light, output the remaining pump light of the k-th stage amplification component to the next amplification component to use pump light.

8. The optical amplifier according to claim 7, characterized in that, The i-th stage amplification component is the first stage amplification component, the j-th stage amplification component is the last stage amplification component, and the k-th stage amplification component is located before the next amplification component using pump light.

9. The optical amplifier according to any one of claims 1 to 8, characterized in that, Each stage of the N-stage amplification assembly (2), except for the amplification assembly that uses pump light last, includes a pump inlet module, a pump outlet module, and a gain fiber. The pump input module in the amplification component is used to input the received pump light into the gain fiber in the amplification component. The pump output module is used to export the remaining pump light output from the gain fiber in the amplification component.

10. The optical amplifier according to claim 9, characterized in that, Both the pump export module and the pump import module are wavelength division multiplexers (WDM).

11. The optical amplifier according to any one of claims 1 to 10, characterized in that, The optical amplifier also includes an isolator (4) and a gain-flattening filter (GFF) (5); The isolator (4) and the GFF (5) are provided between two adjacent amplification stages in the N-stage amplification component (2).

12. The optical amplifier according to any one of claims 1 to 11, characterized in that, The optical amplifier also includes an input detector (6), an output detector (7), and a controller (8); The input detector (6) is located on the input path of the first stage amplification component of the optical amplifier, and the output detector (7) is located on the output path of the last stage amplification component of the optical amplifier. The controller (8) is connected to the pump light source (1), the input detector (6) and the output detector (7) respectively. The input detector (6) is used to detect the first power of the signal light input to the first stage amplification component, and the output detector (7) is used to detect the second power of the signal light output by the last stage amplification component. The controller (8) is used to adjust the power of the pump light output by the pump light source (1) based on the first power and the second power.

13. An optical communication system, characterized in that, Includes a transmitting device, a receiving device, and an optical amplifier as described in any one of claims 1 to 12; The optical amplifier is located between the transmitting device and the receiving device.

Images