Optical amplifier and related device

Abstract

Provided in the embodiments of the present application are an optical amplifier and a related device, which are used for reducing the NFs of optical amplifiers and improving signal transmission quality. The optical amplifier provided in the embodiments of the present application comprises n gain medium stages arranged in sequence, the n gain medium stages being used for successively amplifying an input optical signal of an optical module, n≥2. The optical signal is input into a first gain medium stage among the n gain medium stages and is output from an n-th gain medium stage among the n gain medium stages. The n gain medium stages comprise a first gain medium and a second gain medium, the first gain medium being an m-th gain medium stage among the n gain medium stages, the second gain medium being at least one gain medium following the first gain medium, and m≤[n / 2]. The first gain medium and the second gain medium are different types of gain mediums, an output end of the first gain medium being connected to an input end of the second gain medium. The average gain of a gain medium type to which the first gain medium belongs is greater than the average gain of a gain medium type to which the second gain medium belongs.

Description

An optical amplifier and related equipment

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on January 30, 2024, with application number CN202410138195.X and invention name “An optical amplifier and related equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The embodiments of the present application relate to the field of optical communications, and in particular to an optical amplifier and related equipment. Background Art

[0003] Optical amplifiers (OAs) are commonly used in optical communication networks, amplifying the power of optical signals. With the development of optical communication networks, the power requirements for optical signals are increasing, and the gain requirements for optical amplifiers are also increasing.

[0004] A commonly used method for increasing the gain of an optical amplifier is to cascade multiple gain media to achieve high gain of the optical signal by gradually amplifying the optical signal through the multiple-stage gain media.

[0005] The gain medium itself has an inherent noise factor (NF). In a cascaded optical amplifier structure, the NF of each gain medium contributes to the NF of the entire optical amplifier, resulting in a large NF for the entire amplifier, a low signal-to-noise ratio, and poor signal transmission quality. Summary of the Invention

[0006] The embodiments of the present application provide an optical amplifier and related devices for reducing the NF of the optical amplifier and improving the signal transmission quality.

[0007] In a first aspect, an embodiment of the present application provides an optical amplifier. The optical amplifier includes n-stage gain media arranged in sequence, and the n-stage gain media are used to sequentially amplify the input optical signal of the optical amplifier. Wherein, n ≥ 2. The optical signal is input from the first-stage gain medium in the n-stage gain medium and output from the n-stage gain medium in the n-stage gain medium. The n-stage gain medium includes a first gain medium and a second gain medium, the first gain medium is the m-th stage gain medium in the n-stage gain medium, and the second gain medium is at least one gain medium after the first gain medium. Wherein, That is, m is less than or equal to (n / 2) rounded up. The first gain medium and the second gain medium are different types of gain medium. The output end of the first gain medium is connected to the input end of the second gain medium. The average gain of the type of gain medium to which the first gain medium belongs is greater than the average gain of the type of gain medium to which the second gain medium belongs. In the embodiment of the present application, the average gain is the average gain of the gain medium for signals in the operating band.

[0008] In the embodiment of the present application, in the optical amplifier structure with multi-stage gain media, the NF of the first half of the gain medium contributes more to the overall NF of the optical amplifier, and the NF of the gain medium is negatively correlated with the average gain of the type of gain medium, so the first half of the gain medium contributes more to the overall NF of the optical amplifier. The average gain of the first gain medium (the type of gain medium, hereinafter referred to as the type) in the first stage is greater than the average gain of the second gain medium (the type) in the subsequent stage, which can minimize the NF of the optical amplifier, improve the signal-to-noise ratio of the optical amplifier, and improve the signal transmission quality.

[0009] In an optional implementation, the maximum average gain of the type of gain medium to which the first gain medium belongs is greater than the maximum average gain of the type of gain medium to which the second gain medium belongs.

[0010] In the embodiment of the present application, the maximum average gain is the average gain of the gain medium for each wavelength signal within the working band (the working band of the optical amplifier) ​​at the optimal medium length, and the optimal medium length is the medium length corresponding to the maximum gain at different medium lengths.

[0011] In the embodiments of the present application, the maximum average gain of the type of gain medium is a representation of the average gain of the type of gain medium. Compared to the average gain, the maximum average gain can more accurately reflect the type of gain medium, thereby more accurately distinguishing the first gain medium from the second gain medium.

[0012] It is worth noting that in other implementations below, different types of gain media can also be better distinguished by using the maximum average gain, which will not be described in detail below.

[0013] In an optional implementation, m ≥ 2, and the n-stage gain media arranged in sequence include a first-stage gain medium to an m-th-stage gain medium connected in sequence. In the first-stage gain medium to the m-th-stage gain medium connected in sequence, an average gain of the type of each stage of the gain medium is greater than an average gain of the type of the second gain medium.

[0014] In the embodiment of the present application, the average gain of the first m-stage gain medium (of the type) is made greater than the average gain of the second-stage gain medium (of the type) in the subsequent stage, which can ensure that the NF of the first-stage gain medium is small. Since the weight of the first m-stage gain medium is greater than the weight of the second-stage gain medium in the subsequent stage, this structure can make the NF of the gain medium with a large weight relatively small, thereby reducing the noise figure NF of the optical amplifier. oa , improving signal transmission quality.

[0015] It is worth noting that the first-stage gain medium to the m-th-stage gain medium connected step by step can be the same type of gain medium or different types of gain medium, which is not limited in this application.

[0016] In an optional implementation, m≤n / 3.

[0017] In the embodiment of the present application, since the first third of the gain media is the gain media that is closer to the front among the n-level gain media, the noise factor NF occupied by the first third of the gain media is oa The weight of the first gain medium is large, and limiting the first gain medium to the first third of the gain medium can more significantly reduce the noise figure NF oa , improving signal transmission quality.

[0018] In an optional implementation, m = 1. If the number of second gain media is 1, the output end of the first gain medium is connected to the input end of the second gain medium; if the number of second gain media is greater than 1, the output end of the first gain medium is connected to the input end of the first-stage gain medium among the plurality of second gain media.

[0019] In the embodiment of the present application, since the noise factor NF of the first-stage gain medium in the n-stage gain medium is oa The weight of the first gain medium is the largest, so the first gain medium is limited to the first-level gain medium. Compared with setting the first gain medium at other positions, the noise coefficient NF can be improved. oa The best optimization effect can be achieved, thereby improving the signal transmission quality.

[0020] In one optional implementation, among n-stage gain media arranged sequentially, the average gain of any given type of gain medium is greater than the average gain of the next-stage gain medium. That is, among n-stage gain media 2000, the average gain of each type of gain medium decreases from the first stage to the n-stage gain medium.

[0021] In the embodiments of the present application, since the average gain of the gain medium is negatively correlated with the NF, the average gain of the n-stage gain medium decreases step by step, so that the NF of the n-stage gain medium increases step by step. Since the weights of the stages in the n-stage gain medium decrease step by step (the noise figure NF oa of the gain medium closer to the front has a greater weight). The weights of the stages in the n-stage gain medium decrease step by step and the NF increases step by step. The greater the weight of the gain medium, the smaller the NF, which can better reduce the noise figure NF oa and improve the signal transmission quality.

[0022] In an optional implementation, m≥2, the n-stage gain medium further includes a third gain medium, and the third gain medium is the k-th stage gain medium in the n-stage gain medium, where k < m. The third gain medium and the first gain medium are different types of gain media. The average gain of the gain medium type to which the third gain medium belongs is less than the average gain of the gain medium type to which the first gain medium belongs.

[0023] In an optional implementation, m = 2 and k = 1.

[0024] In an optional implementation, the n-stage gain medium further includes a fourth gain medium. The input end of the fourth gain medium is connected to the output end of the second gain medium. The fourth gain medium and the second gain medium are different types of gain media. The average gain of the gain medium type to which the fourth gain medium belongs is greater than the average gain of the gain medium type to which the second gain medium belongs.

[0025] In an optional implementation, there is at least one target gain medium in the second gain medium. The gain flatness of the target gain medium is better than that of the first gain medium. The target gain medium is at least one gain medium after the m-th stage gain medium.

[0026] In the same stage of gain medium, it is usually impossible to achieve the optimal values of the average gain and the gain flatness simultaneously, and a trade-off needs to be made between the two in application. Since the target gain medium is relatively far back in the n-stage gain medium, the weight of the target gain medium is small. If the noise figure NF of the optical amplifier oa is reduced by increasing the average gain of the target gain medium oa , the gain is small and the significance is not great. Therefore, the gain flatness of the target gain medium is made better (better than the gain flatness of the first gain medium 2100), which can improve the spectral flatness of the optical amplifier oa, thereby reducing the GFF depth, reducing the loss of the optical amplifier oa, and further reducing the pump power of the pump module corresponding to each stage of the gain medium.

[0027] In an optional implementation, the gain flatness of the gain medium in at least one second gain medium is better than that of the first gain medium.

[0028] In the embodiment of the present application, the first gain medium is mainly used to reduce the noise factor NF of the optical amplifier oa oa The second gain medium after the first gain medium has a significant effect on the noise factor NF of the optical amplifier oa. oa The impact of the first gain medium is minimal. Therefore, the gain flatness of all secondary gain media following the first gain medium is superior to that of the first gain medium. Consequently, the gain flatness of the optical amplifier oa is improved through all secondary gain media, significantly reducing the GFF depth, lowering the losses of the optical amplifier oa, and reducing pump power.

[0029] In an optional implementation, among n-stage gain media arranged sequentially, the gain flatness of any gain medium is better than the gain flatness of the previous stage gain medium.

[0030] In the embodiment of the present application, since the average gain and gain flatness of the gain medium cannot be optimized at the same time, the gain flatness of the n-stage gain medium is gradually improved, so that: in the trade-off between average gain and gain flatness, the gain medium closer to the front is more inclined towards average gain; the gain medium closer to the back is more inclined towards gain flatness. oa The weight of the n-level gain medium is shown in the figure. The weight of each level decreases step by step (the noise coefficient NF of the gain medium closer to the front is larger). oa The greater the weight of the gain medium, the more inclined it is to the average gain, which can better reduce the noise figure NF of the optical amplifier oa. oa The further back the gain medium is, the more inclined it is to gain flatness, which can better reduce the loss of the optical amplifier OA, so that the optical amplifier OA has a lower noise figure NF. oa With smaller losses.

[0031] In an optional implementation, the n-stage gain media arranged in sequence include multiple gain media of different types.

[0032] In an optional implementation, there are multiple second gain media, and the multiple second gain media include multiple gain media of different types.

[0033] In an optional implementation, the multiple gain media of different types include at least one of the following: doped optical fibers with different doping elements, doped optical fibers with different doping concentrations, and gain media with different structures.

[0034] In an optional implementation, a gain flattening filter GFF and / or a variable optical attenuator VOA are further included between the output end of the first gain medium and the input end of the second gain medium. The GFF is used to balance the gain of the optical signal at each wavelength, and the VOA is used to adjust the gain point and tilt of the optical amplifier.

[0035] In an optional implementation, the optical amplifier further includes a control circuit configured to control at least one of the following items of the output optical signal of the optical amplifier: output optical power, gain, and tilt.

[0036] In a second aspect, an embodiment of the present application provides an optical communication device, which includes the optical amplifier described in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG1 is a schematic structural diagram of an optical communication system provided by the present application;

[0038] FIG2 is a schematic structural diagram of an optical amplifier OA provided in an embodiment of the present application;

[0039] FIG3 is a schematic diagram of the gain of a gain medium provided in an embodiment of the present application at different medium lengths;

[0040] FIG4 is a schematic structural diagram of an optical amplifier OA with gradually decreasing maximum average gain provided by an embodiment of the present application;

[0041] FIG5a is a schematic structural diagram of an optical amplifier oa including a low-gain medium in a first gain medium front stage provided by an embodiment of the present application;

[0042] FIG5 b is another structural diagram of an optical amplifier oa including a low-gain medium in the first gain medium front stage provided by an embodiment of the present application;

[0043] FIG6 is a schematic structural diagram of an optical amplifier oa including a third gain medium provided in an embodiment of the present application;

[0044] FIG7 is a schematic structural diagram of an optical amplifier oa including a fourth gain medium provided in an embodiment of the present application;

[0045] FIG8 is a schematic diagram showing the gain flatness arrangement of an optical amplifier oa provided in an embodiment of the present application;

[0046] FIG9 is a schematic diagram of a wavelength-gain curve provided in an embodiment of the present application;

[0047] FIG10 is a schematic structural diagram of an optical amplifier oa including different types of second gain media provided in an embodiment of the present application. DETAILED DESCRIPTION

[0048] The embodiments of the present application are described below in conjunction with the accompanying drawings. Those skilled in the art will appreciate that, with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0049] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the terms used in this way are interchangeable when appropriate, and this is merely a way of distinguishing objects of the same attributes when describing the embodiments of the present application. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, so that the process, method, system, product or device comprising a series of units need not be limited to those units, but may include other units that are not clearly listed or inherent to these processes, methods, products or devices. In addition, "at least one" refers to one or more, and "a plurality" refers to two or more. "and / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent: the situation where A exists alone, A and B exist simultaneously, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or plural.

[0050] Figure 1 is a schematic diagram of the structure of an optical communication system. The optical communication system includes a transmitter, a receiver, and optical fibers. The transmitter performs electro-optical modulation, thereby carrying signals in optical signals, and then inputs the optical signals into the optical fiber for transmission. The optical fiber transmits the optical signals. The receiver receives and analyzes the optical signals.

[0051] As shown in Figure 1, an optical communication system may also include an optical amplifier. This amplifier is located between the transmitter and receiver. It amplifies optical signals to increase their power at the receiver, thereby compensating for signal loss and improving transmission reliability and quality.

[0052] Optionally, the optical amplifier may also be present in any optical communication device (eg, a transmitting device, a receiving device, a relay node, etc.) of the optical communication system to amplify the optical signal.

[0053] With the advancement of optical communication technology, optical communication systems are placing increasing demands on transmission power, and consequently, on the output power of optical amplifiers. To increase the output power of optical amplifiers, it is necessary to boost their gain. A common approach is to cascade multiple gain media within an optical amplifier. This multi-stage gain medium gradually amplifies the optical signal, achieving high gain and thus increasing the output power of the optical amplifier.

[0054] However, the gain medium itself has an inherent noise figure (NF). In an optical amplifier structure with multiple gain media, the NF of each gain medium contributes to the overall NF of the optical amplifier, resulting in a high NF. This high NF leads to a low optical signal-to-noise ratio (OSNR) of the optical amplifier, affecting signal transmission quality.

[0055] To address the above issues, embodiments of the present application provide an optical amplifier and related devices. The optical amplifier provided by embodiments of the present application reduces the NF of the optical amplifier by placing the gain medium with higher average gain at the front of the multi-stage gain medium, thereby improving signal transmission quality.

[0056] The optical amplifier oa provided in the embodiment of the present application includes n-stage gain media 2000 arranged in sequence. The noise figure NF of the optical amplifier oa is oa The theoretical calculation formula is shown in the following formula 1:

[0057] Among them, NF x is the noise coefficient of the x-th gain medium; G x is the gain of the x-th level gain medium, which is the actual gain of the gain medium; L x is the loss value between the x-1th level gain medium and the xth level gain medium.

[0058] The n items included in formula 1 are the noise coefficients generated by each level of the n-level gain medium. The sum of the n noise coefficients is the noise coefficient NF of the optical amplifier oa. oa If the noise coefficient generated by each level of gain medium in the optical amplifier oa in formula 1 is divided by the noise coefficient NF of the gain medium itself x Divide them and you can get the weight of the gain medium of this stage in the optical amplifier oa. The larger the weight, the greater the noise factor NF of the gain medium of this stage on the optical amplifier oa. x The greater the contribution of x , G x Usually larger, so mainly consider G x The impact on weight size.

[0059] In Formula 1, the noise coefficient generated by the first-stage gain medium is the first term NF1. The ratio of NF1 to the noise coefficient NF1 of the first-stage gain medium is 1, that is, the weight of the first-stage gain medium is 1.

[0060] In formula 1, the noise coefficient generated by the second-stage gain medium is the second term The ratio of the noise figure NF2 of the second-stage gain medium is approximately That is, the weight of the second-stage gain medium is Weight of the second-stage gain medium Less than the weight 1 of the first-stage gain medium.

[0061] In formula 1, the noise coefficient generated by the third-stage gain medium is the third term The ratio of the noise figure NF3 of the third-stage gain medium is approximately That is, the weight of the third-level gain medium is Weight of the third-stage gain medium Less than the weight of the second-stage gain medium

[0062] By analogy, we can see that the weight of the gain medium decreases as the stage is further back. In other words, the noise coefficient NF of the gain medium in the first few stages of the optical amplifier oa has a greater impact on the optical amplifier oa. And the noise coefficient NF of the gain medium in the first stage has a greater impact on the optical amplifier oa. As long as the noise coefficient NF of the gain medium in the first few stages is reduced, the noise coefficient NF of the optical amplifier oa can be reduced. oa .

[0063] Therefore, in the embodiment of the present application, the noise factor NF of the optical amplifier oa is reduced oa The idea is to make the noise factor of the first few stages of gain media in the n-stage gain medium smaller than the noise factor NF of the last few stages of gain media. Since the noise factor NF of the gain medium is negatively correlated with the average gain of the type of gain medium (hereinafter referred to as the average gain of the gain medium for convenience), making the average gain of the first few stages of gain media in the optical amplifier oa greater than the average gain of the last few stages of gain media can reduce the NF of the first few stages of gain media, thereby reducing the noise factor NF of the optical amplifier oa. oa .

[0064] Therefore, the embodiment of the present application provides an optical amplifier structure as shown in FIG2. In this structure, the average gain of the mth-stage gain medium (first gain medium 2100) in the optical amplifier oa is made greater than the average gain of the second gain medium 2200 in the subsequent stage of the first gain medium 2100, thereby reducing the NF of the mth-stage gain medium in the front, thereby reducing the noise figure NF of the optical amplifier oa. oa .

[0065] As shown in FIG2 , an optical amplifier (OA) provided in an embodiment of the present application includes n-stage gain media 2000 arranged in sequence. Where n ≥ 2. An optical signal is input from the first-stage gain medium in the n-stage gain media 2000 and output from the n-stage gain medium in the n-stage gain media 2000. The n-stage gain media 2000 are used to sequentially amplify the input optical signal of the optical amplifier OA.

[0066] The n-stage gain medium 2000 includes a first gain medium 2100 and a second gain medium 2200. The first gain medium 2100 and the second gain medium 2200 are different types of gain media. The average gain of the type of gain medium to which the first gain medium 2100 belongs is greater than the average gain of the type of gain medium to which the second gain medium 2200 belongs. For example, the first gain medium 2100 is a semiconductor optical amplifier (SOA), and the second gain medium 2200 is an erbium-doped fiber (EDF).

[0067] The first gain medium 2100 is the mth gain medium in the n-stage gain medium 2000, and the second gain medium 2200 is at least one gain medium subsequent to the first gain medium 2100. The output end of the first gain medium 2100 is connected to the input end of the second gain medium 2200.

[0068] In the embodiment of the present application, the first gain medium 2100 is the mth-order gain medium that is located at the front of the n-order gain medium 2000. In the n-order gain medium 2000, the closer the first gain medium 2100 is to the front (i.e., the smaller m is), the lower the noise figure NF of the optical amplifier oa. oa The smaller it is, the better the signal transmission quality.

[0069] In order to achieve a smaller noise figure NF oa , the value range of m can be limited to That is, m is less than or equal to the result of rounding up (n / 2), thereby limiting the first gain medium 2100 to the first half of the gain medium of the n-stage gain medium 2000.

[0070] That is, among n-stage gain media 2000, the first half of the gain media stages include a first gain medium 2100. Following the first gain medium 2100, there is at least one second gain medium 2200, and the average gain of the type to which the second gain medium 2200 belongs is smaller than the average gain of the type to which the first gain medium 2100 belongs.

[0071] For example, in Figure 2, n=3, then m can be 1 or 2. The first gain medium 2100 is the first or second gain medium in the three-stage gain medium 2000. In FIG2 , the first-stage gain medium is used as an example of the first gain medium 2100, and the second-stage gain medium and the third-stage gain medium are the second gain medium 2200.

[0072] In the embodiments of the present application, average gain is an inherent characteristic of the gain medium and is related to the type of gain medium. The average gain of the gain medium for signals of various wavelengths within the operating band of the optical amplifier oa is the average gain of the gain medium.

[0073] It's worth noting that the average gain of a given type of gain medium is an inherent property of that type of medium. However, in optical amplifier OA, the actual gain of first gain medium 2100 may be greater or less than the actual gain of second gain medium 2200, and this is not a limitation of this disclosure. In one example, the gain of first gain medium 2100 is 3 dB, and the gain of second gain medium 2200 is 4 dB.

[0074] In the embodiment of the present application, since in the optical amplifier structure of the multi-stage gain medium, the NF of the first half of the gain medium contributes more to the overall NF of the optical amplifier, and the NF of the gain medium is negatively correlated with the average gain of the type to which the gain medium belongs, the average gain of the first gain medium 2100 (the type of gain medium to which it belongs, hereinafter referred to as the type to which it belongs) of the mth stage in the n-stage gain medium 2000 is greater than the average gain of the second gain medium (the type to which it belongs), which can minimize the NF of the optical amplifier, improve the signal-to-noise ratio of the optical amplifier, and improve the signal transmission quality.

[0075] The maximum average gain of a gain medium type is a measure of the average gain of that type. This maximum average gain is also an inherent characteristic of the gain medium and is related to its type. For each gain medium, its gain is related to the medium length. An example of a corresponding medium length-gain curve is shown in Figure 3. In the medium length-gain curve, the medium length corresponding to the maximum gain is the optimal medium length for that gain medium. The average gain of that gain medium for signals at all wavelengths within the operating band of the optical amplifier oa at the optimal medium length is the maximum average gain of that gain medium.

[0076] In an optional implementation, the maximum average gain of the type of gain medium to which the first gain medium 2100 belongs may be greater than the maximum average gain of the type of gain medium to which the second gain medium 2200 belongs.

[0077] In the embodiments of the present application, the maximum average gain of the type of gain medium is a representation of the average gain of the type of gain medium. Compared to the average gain, the maximum average gain can more accurately reflect the type of gain medium, thereby more accurately distinguishing the first gain medium from the second gain medium.

[0078] It is worth noting that in other embodiments below, different types of gain media can also be better distinguished by using the maximum average gain, which will not be described in detail below.

[0079] In this embodiment of the present application, the optical amplifier OA may further include pump modules for each stage of gain medium 2000. The pump modules are configured to output pump light to the corresponding gain medium. For example, in Figure 2 , if the first-stage gain medium is an erbium-doped fiber, the pump module for that stage of gain medium is configured to emit pump light, which is then output to the first-stage gain medium to amplify the optical signal. Alternatively, the pump may be pump light, pump current, or pump voltage, and this application does not limit this.

[0080] Optionally, the value range of m can be further narrowed so that the first gain medium 2100 is closer to the front, thereby further reducing the noise factor NF of the optical amplifier oa. oa For example, the value range of m can be limited to m≤n / 3, thereby limiting the first gain medium 2100 to the first third of the n-stage gain medium 2000.

[0081] In the embodiment of the present application, since the first third of the gain media are the gain media closer to the front in the n-stage gain media 2000, the noise factor NF occupied by the first third of the gain media is oa The weight of the first gain medium 2100 is large, and the noise figure NF can be more significantly reduced by limiting the first gain medium 2100 to the first one-third of the gain medium. oa , improving signal transmission quality.

[0082] In an optional implementation, m=1, that is, the first gain medium 2100 is the first-stage gain medium in the n-stage gain medium 2000. In the embodiment of the present application, since the noise factor NF of the first-stage gain medium in the n-stage gain medium 2000 is oa The weight is the largest, so the first gain medium 2100 is limited to the first-stage gain medium. Compared with setting the first gain medium 2100 at other positions, the noise coefficient NF oa The best optimization effect can be achieved, thereby improving the signal transmission quality.

[0083] In one optional implementation, among the n-stage gain media 2000 arranged sequentially, the average gain of any given gain medium is greater than the average gain of the next-stage gain medium. Specifically, as shown in FIG4 , among the n-stage gain media 2000, the maximum average gain of the gain media decreases from the first stage to the n-stage gain medium. The first-stage gain medium with the highest maximum average gain is the first gain medium 2100, and the remaining gain media are the second gain media 2200.

[0084] In the embodiment of the present application, since the average gain of the type of gain medium is negatively correlated with the NF, the average gain of the n-stage gain medium 2000 is gradually reduced, and the NF of the n-stage gain medium 2000 is gradually increased. oa The weight of each level in the n-level gain medium 2000 decreases step by step (the noise coefficient NF of the gain medium closer to the front is greater). oa The greater the weight of the n-level gain medium 2000, the weight of each level decreases step by step, and the NF increases step by step. The greater the weight of the gain medium, the smaller the NF, which can better reduce the noise factor NF. oa , improving signal transmission quality.

[0085] Similarly, the maximum average gain of any of the plurality of sequentially arranged second gain media 2200 can be greater than the maximum average gain of the subsequent gain medium. That is, the maximum average gain of the plurality of second gain media 2200 following the first gain medium 2100 decreases step by step.

[0086] Similarly, it is also possible to ensure that, among the n-stage gain media 2000 arranged in sequence, the maximum average gain of the type of any gain medium is greater than the maximum average gain of the type of the subsequent gain medium.

[0087] In an optional implementation, m≥2. In order to minimize the noise factor NF oa , which can make the maximum average gain of the first few stages of gain media larger. Specifically, in the n-stage gain medium 2000, the average gain of the type of gain media from the first to the mth stage is greater than the average gain of the type of the second gain medium.

[0088] For example, as shown in FIG5 a , n=4, m=2, the first gain medium 2100 is the second-order gain medium, and the third-order gain medium to the fourth-order gain medium are all the second gain medium 2200 .

[0089] The average gain of the first-stage gain medium is 8 dB, and the average gain of the second-stage gain medium (the first gain medium 2100) is 10 dB, both of which are greater than the average gain of 5 dB of the second gain medium 2200 (the third and fourth-stage gain media).

[0090] In the embodiment of the present application, making the average gain of the first m-stage gain media greater than the average gain of the subsequent second gain medium 2200 can ensure that the NF of the previous-stage gain medium is relatively small. Since the weight of the first m-stage gain media is greater than the weight of the subsequent second gain medium 2200, this structure can make the NF of the gain medium with a larger weight relatively small, thereby reducing the noise figure NF. oa , improving the signal transmission quality.

[0091] It should be noted that the first m-stage gain media can be different types of gain media as shown in FIG. 5a, so that the average gains of the types to which the first m-stage gain media belong are different. Or as shown in FIG. 5b, the first m-stage gain media are of the same type of gain medium (for example, all erbium-doped fibers), and the average gains of the types to which the first m-stage gain media belong are the same. The present application does not limit this.

[0092] Similarly, it is also possible to make the maximum average gain of the first m-stage gain media greater than the maximum average gain of the subsequent second gain medium 2200.

[0093] In an optional implementation manner, a third gain medium 2300 with a lower gain is further included before the first gain medium 2100.

[0094] The third gain medium 2300 is the k-th stage gain medium among the n-stage gain media, where k < m. The third gain medium 2300 and the first gain medium 2100 are different types of gain media. The output end of the third gain medium 2300 is connected to the input end of the first gain medium 2100. The average gain of the type of gain medium to which the third gain medium 2300 belongs is less than the average gain of the type of gain medium to which the first gain medium 2100 belongs.

[0095] For example, as shown in FIG. 6, n = 4, m = 2, the first gain medium 2100 is the second-stage gain medium with an average gain of 12 dB. The third and fourth-stage gain media are both the second gain medium 2200 with an average gain of 6 dB. The first-stage gain medium is the third gain medium 2300 with an average gain of 6 dB, which is less than the average gain of the first gain medium 2100.

[0096] In one optional implementation, the subsequent stage of the second gain medium 2200 further includes a fourth gain medium 2400 having a higher gain. The input end of the fourth gain medium 2400 is connected to the output end of the second gain medium 2200. The fourth gain medium 2400 and the second gain medium 2200 are different types of gain media. The average gain of the type of gain medium to which the fourth gain medium belongs is greater than the average gain of the type of gain medium to which the second gain medium belongs.

[0097] For example, as shown in FIG7 , n=4, m=1, the second and third-level gain media are the second gain medium 2200, with a maximum average gain of 6 dB. The fourth-level gain medium is the fourth gain medium 2400, with an average gain of 10 dB, which is greater than the average gain of the second gain medium 2200.

[0098] In the embodiment of the present application, in addition to reducing the noise factor NF of the optical amplifier oa om The gain flattening filter (GFF) depth of the optical amplifier oa can also be reduced by sorting the gain flatness of each level of gain medium in the n-level gain medium 2000, thereby reducing the power consumption of the optical amplifier oa.

[0099] In an optional implementation, a target gain medium is present in at least one second gain medium 2200 subsequent to the first gain medium 2100 , and the gain flatness of the target gain medium is better than that of the first gain medium 2100 .

[0100] In this embodiment of the present application, the optical amplifier OA may further include components such as a gain flattening filter (GFF) and a variable optical attenuator (VOA). The GFF can be located between any two stages of gain media in the n-stage gain media 2000 to balance the gain of the optical signal at various wavelengths. The VOA can be located between any two stages of gain media in the n-stage gain media 2000 to adjust the gain point and tilt of the optical amplifier OA.

[0101] For example, as shown in FIG8 , n=3, a GFF is included between the first-stage gain medium (first gain medium 2100 ) and the second-stage gain medium, and a GFF and a VOA are included between the second-stage gain medium and the third-stage gain medium.

[0102] After the first-stage gain medium amplifies the input optical signal, it is output to the GFF, which performs flat filtering on the signal, flattening the gain spectrum. The optical signal then enters the second-stage gain medium for amplification, the GFF for flat filtering, the VOA for attenuation adjustment to match the power of the pump module (to achieve different gain point locking and tilt adjustment for the optical amplifier), and finally enters the third-stage gain medium for further amplification.

[0103] As shown in Figure 9, after an optical signal is amplified by a gain medium, the gain flatness of the gain medium causes the gain to vary across wavelengths. Some bands have higher gains, while others have lower gains. The wavelength-gain curve shown in Figure 9 provides the average gain for each wavelength within the optical amplifier's OA operating band. The gain flatness is calculated by calculating the envelope area between the minimum gain in the operating band and the wavelength-gain curve.

[0104] The GFF achieves flat filtering of the signal by attenuating peaks in the curve. The GFF is a filter spectrum that attenuates the optical signal. A deeper GFF increases the power attenuation. The worse the gain flatness of the gain medium, the deeper the corresponding GFF. This increases the power attenuation and the greater the loss to the optical amplifier (OA). This requires a higher-power pump module.

[0105] In the same level of gain medium, the maximum average gain and gain flatness cannot usually be optimized at the same time, and a trade-off needs to be made between the two in application. Since the target gain medium is relatively late in the n-level gain medium, the weight of the target gain medium is relatively small. If the noise figure NF of the optical amplifier oa is reduced by increasing the maximum average gain of the target gain medium, oa , the benefit is small and of little significance. Therefore, making the gain flatness of the target gain medium better (better than the gain flatness of the first gain medium 2100) can improve the spectral flatness of the optical amplifier oa, thereby reducing the GFF depth and the loss of the optical amplifier oa, and thus reducing the pump power of the pump module corresponding to each level of gain medium.

[0106] In one optional implementation, the gain flatness of any one of the at least one second gain medium 2200 is superior to the gain flatness of the first gain medium 2100. For example, as shown in FIG8 , the first-stage gain medium is the first gain medium 2100, and the second and third-stage gain media are the second gain medium 2200, which are target gain media. The gain flatness of both the second and third-stage gain media is superior to that of the first-stage gain medium.

[0107] In the embodiment of the present application, the first gain medium 2100 is mainly used to reduce the noise factor NF of the optical amplifier oa. oaThe second gain medium after the first gain medium 2100 has a noise factor NF for the optical amplifier oa. oa The influence of the gain flatness is minimal. Therefore, the gain flatness of all second gain media 2200 subsequent to the first gain medium 2100 is superior to that of the first gain medium 2100. Consequently, the gain flatness of the optical amplifier oa is improved by all second gain media 2200, thereby significantly reducing the GFF depth, lowering the loss of the optical amplifier oa, and reducing the pump power.

[0108] In an optional implementation, among the n-stage gain media 2000 arranged sequentially, the gain flatness of any gain medium is better than that of the previous stage gain medium. That is, the gain flatness of the n-stage gain media 2000 becomes better step by step, as shown in FIG8 .

[0109] In the embodiment of the present application, since the maximum average gain and gain flatness of the gain medium cannot be optimized at the same time, the gain flatness of the n-stage gain medium 2000 is gradually improved, so that: in the trade-off between maximum average gain and gain flatness, the gain medium closer to the front is more inclined toward the maximum average gain; the gain medium closer to the back is more inclined toward gain flatness. oa The weight of each level in the n-level gain medium 2000 decreases step by step (the noise coefficient NF of the gain medium closer to the front is greater). oa The greater the weight of the gain medium, the more it tilts towards the maximum average gain, which can better reduce the noise figure NF of the optical amplifier oa. oa The further back the gain medium is, the more inclined it is to gain flatness, which can better reduce the loss of the optical amplifier OA, so that the optical amplifier OA has a lower noise figure NF. oa With smaller losses.

[0110] It is worth noting that Figure 8 is only an example of the positions of the GFFs and VOAs and does not limit the number and positions of the GFFs and VOAs. The optical amplifier oa may include more or fewer GFFs and more or fewer VOAs, and this application does not limit this.

[0111] In any of the embodiments of FIG. 2 to FIG. 7 , a GFF and / or a VOA may also be included, and this application does not limit this.

[0112] In the embodiment of the present application, the types of the gain media of each level in the sequentially arranged n-level gain media 2000 are not limited. The n-level gain media 2000 can be different types of gain media, which is not limited in the present application.

[0113] In the embodiments of the present application, different types of gain media may include doped fibers with different doping elements, doped fibers with different doping concentrations, or gain media with different structures, which is not limited in the present application.

[0114] Taking Figure 2 as an example, if the first-stage gain medium is an erbium-doped fiber and the second-stage gain medium is a bismuth-doped fiber, then the first-stage gain medium and the second-stage gain medium are doped fibers with different doping elements. If the first-stage gain medium is a semiconductor optical amplifier (SOA) and the n-stage gain medium is an erbium-doped fiber, then the first-stage gain medium and the n-stage gain medium are gain media with different structures. Optionally, optical fibers with different core diameters and refractive indices also have different gain media structures, but this application does not limit this.

[0115] In an optional implementation, there are multiple second gain media 2200 , and the multiple second gain media 2200 may also include multiple gain media of different types.

[0116] For example, as shown in Figure 10, n = 5, m = 2, and k = 3. In a five-level gain medium 2000, the first and second level gain media are the first gain medium 2100, and the third through fifth level gain media are the second gain medium 2200. The third level gain medium is an SOA, and the fourth and fifth level gain media are doped fibers. Therefore, the second gain medium 2200 includes multiple gain media of different types.

[0117] The optical amplifiers described in the embodiments shown in Figures 2 to 10 may further include a control circuit. The control circuit is configured to control the output optical signal of the optical amplifier. Specifically, the control circuit may control at least one of the following aspects of the output optical signal: output optical power, gain, tilt, etc., which are not limited in this application.

[0118] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0119] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0120] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0121] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0122] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

Claims

1. An optical amplifier, characterized in that: It includes an n-stage gain medium arranged in sequence. The optical signal is input from the first-stage gain medium in the n-stage gain medium and output from the n-stage gain medium in the n-stage gain medium. The n-stage gain medium is used to amplify the input optical signal of the optical module in sequence, where n≥2; The n-stage gain medium includes a first gain medium and a second gain medium, wherein the first gain medium is the m-th stage gain medium in the n-stage gain medium, and the second gain medium is at least one gain medium in the subsequent stage of the first gain medium. The first gain medium and the second gain medium are gain media of different types; The output end of the first gain medium is connected to the input end of the second gain medium; The average gain corresponding to the type of gain medium to which the first gain medium belongs is greater than the average gain corresponding to the type of gain medium to which the second gain medium belongs. The average gain is the average gain of the gain medium for the signals in the working band.

2. The optical amplifier according to claim 1, wherein The maximum average gain of the type of gain medium to which the first gain medium belongs is greater than the maximum average gain of the type of gain medium to which the second gain medium belongs; The maximum average gain is the average gain of the gain medium for the signals of each wavelength in the working band under the optimal medium length. The optimal medium length is the medium length corresponding to the maximum gain under different medium lengths.

3. The optical amplifier according to claim 1 or 2, characterized in that m≥2, and the n-stage gain medium arranged in sequence includes the 1st-stage gain medium to the mth-stage gain medium connected in sequence; Among the 1st-stage gain medium to the mth-stage gain medium connected in sequence, the average gain of each stage of gain medium belongs to a type greater than the average gain of the type to which the second gain medium belongs.

4. The optical amplifier according to claim 3, wherein: The 1st-stage gain medium to the mth-stage gain medium connected in sequence are gain media of the same type.

5. The optical amplifier according to any one of claims 1 to 4, characterized in that m≤n / 3.

6. The optical amplifier according to claim 1, 2 or 5, characterized in that: m＝1； If the number of the second gain media is 1, the output end of the first gain medium is connected to the input end of the second gain medium; If the number of the second gain media is greater than 1, the output end of the first gain medium is connected to the input end of the first-stage gain medium among the multiple second gain media.

7. The optical amplifier according to claim 6, wherein: In the n-stage gain medium arranged in sequence, the average gain of any gain medium belongs to a type greater than the average gain of the type of the subsequent-stage gain medium.

8. The optical amplifier according to any one of claims 1 to 5, characterized in that m≥2, and the n-stage gain medium further includes a third gain medium. The third gain medium is the kth-stage gain medium in the n-stage gain medium, where k<m. The third gain medium and the first gain medium are gain media of different types; The average gain of the type of gain medium to which the third gain medium belongs is less than the average gain of the type of gain medium to which the first gain medium belongs.

9. The optical amplifier according to any one of claims 1 to 8, characterized in that The n-stage gain medium further includes a fourth gain medium. The input end of the fourth gain medium is connected to the output end of the second gain medium. The fourth gain medium and the second gain medium are gain media of different types; The average gain of the type of gain medium to which the fourth gain medium belongs is greater than the average gain of the type of gain medium to which the second gain medium belongs.

10. The optical amplifier according to any one of claims 1 to 9, characterized in that There is a target gain medium in at least one second gain medium, and the gain flatness of the target gain medium is better than the gain flatness of the first gain medium.

11. The optical amplifier according to claim 10, wherein: The gain flatness of the gain media in at least one second gain medium is better than the gain flatness of the first gain medium.

12. The optical amplifier according to claim 11, wherein: In the n-stage gain media arranged in sequence, the gain flatness of any gain medium is better than the gain flatness of the previous stage gain medium.

13. The optical amplifier according to any one of claims 1 to 12, characterized in that There are multiple second gain media, and the multiple second gain media include multiple gain media of different types.

14. The optical amplifier according to any one of claims 1 to 13, characterized in that The multiple gain media of different types include at least one of the following: Doped optical fibers with different doping elements, doped optical fibers with different doping concentrations, and gain media with different structures.

15. The optical amplifier according to any one of claims 1 to 14, characterized in that A variable optical attenuator VOA and / or a gain flattening filter GFF are further included between the output end of the first gain medium and the input end of the second gain medium; The GFF is used to balance the gain of the optical signal at each wavelength, and the VOA is used to adjust the gain point and tilt of the optical amplifier.

16. An optical communication device, characterized in that: The optical amplifier comprises the optical amplifier according to any one of claims 1 to 15.

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