Optical fiber amplifier

Abstract

The present application provides an optical fiber amplifier, comprising: a gain optical path, configured to amplify signal light; a first filter, configured to filter backward spontaneous emission light generated by the amplification of the signal light by the gain optical path, and retain auxiliary light that meets a preset requirement; and a coupler, configured to combine the auxiliary light with new signal light to be amplified by the gain optical path, so as to enhance population inversion generated when the combined new signal light is amplified by the gain optical path.

Description

Optical fiber amplifier

[0001] Cross-reference to related applications

[0002] The present application claims priority to the Chinese patent application No. 202410860759.0, filed on June 28, 2024, and entitled "Optical fiber amplifier", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the field of optical communication technology, and in particular to an optical fiber amplifier. BACKGROUND

[0004] With the rapid development of optical communication technology, optical fiber amplifiers play a crucial role in optical communication networks. In the process of signal light transmission, the signal intensity will gradually weaken with the increase of transmission distance. In order to maintain the stability of signal intensity in long-distance transmission, it is necessary to use optical fiber amplifiers to amplify signal light.

[0005] The noise figure of an optical fiber amplifier is one of the key factors affecting its performance. The noise figure reflects the degree of interference of the optical fiber amplifier to the signal, and a lower noise figure means lower signal interference, thereby improving the transmission quality and stability of signal light in optical communication networks.

[0006] Therefore, how to reduce the noise figure of an optical fiber amplifier is a problem that needs to be solved at present. SUMMARY

[0007] The purpose of the present application is to provide an optical fiber amplifier that can produce stronger population inversion of signal light when amplifying signal light, thereby effectively reducing the noise figure.

[0008] In a first aspect, an optical fiber amplifier is provided, comprising: a gain optical path for amplifying signal light; a first filter for filtering backward spontaneous emission light generated by the gain optical path amplifying signal light, and retaining auxiliary light meeting a preset requirement; a coupler for combining the auxiliary light with new signal light to be amplified by the gain optical path, so as to enhance the population inversion of the new signal light generated by the gain optical path amplifying the new signal light after combination. BRIEF DESCRIPTION OF DRAWINGS

[0009] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments described in the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0010] Fig. 1 is a first structural schematic diagram of the optical fiber amplifier according to an embodiment of the present application.

[0011] Fig. 2 is a comparative schematic diagram of the noise figure between the optical fiber amplifier according to an embodiment of the present application and a conventional optical fiber amplifier.

[0012] Fig. 3 is a structural schematic diagram of the gain optical path in the optical fiber amplifier according to an embodiment of the present application.

[0013] Fig. 4 is a second structural schematic diagram of the optical fiber amplifier according to an embodiment of the present application.

[0014] Fig. 5 is a third structural schematic diagram of the optical fiber amplifier according to an embodiment of the present application.

[0015] Fig. 6 is a fourth structural schematic diagram of the optical fiber amplifier according to an embodiment of the present application.

[0016] Fig. 7 is a fifth structural schematic diagram of the optical fiber amplifier according to an embodiment of the present application. DETAILED DESCRIPTION

[0017] As mentioned above, the noise figure of the optical fiber amplifier is one of the key factors affecting its performance. The noise figure reflects the degree of interference of the optical fiber amplifier to the signal, and a lower noise figure means a lower signal interference, thereby improving the transmission quality and stability of the signal light in the optical communication network.

[0018] Population inversion is a prerequisite for laser generation. In order to obtain laser, it is necessary to make the number of atoms on the high energy level E2 greater than that on the low energy level E1, that is, to excite a large number of atoms on the low energy level E1 to the high energy level E2. The transition of atoms from the low energy level E1 to the high energy level E2 is the population inversion.

[0019] As can be seen from the above introduction of population inversion, enhancing the population inversion can improve the effect of light amplification. Therefore, when the optical fiber amplifier amplifies the signal light, if the population inversion of the signal light can be further enhanced, the noise figure of the optical fiber amplifier can be effectively reduced.

[0020] In view of this, the present application aims to provide an optical fiber amplifier capable of enhancing the population inversion generated by the signal light when amplified.

[0021] In order for those skilled in the art to better understand the technical solutions in the specification, the technical solutions in the embodiments of the present application will be clearly and completely described in the specification below in conjunction with the drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the specification, not all. Based on the embodiments in the specification, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the specification.

[0022] Figure 1 is a schematic diagram of the structure of the optical fiber amplifier according to the embodiments of the present application, which comprises: a gain optical path 110 for amplifying signal light. A first filter 120 for filtering the backward spontaneous emission light generated by the gain optical path amplifying the signal light, and retaining the auxiliary light meeting the preset requirements. A coupler 130 for coupling the auxiliary light with the new signal light to be amplified by the gain optical path to enhance the population inversion of the coupled signal light generated by the gain optical path amplification.

[0023] It should be understood that in the process of optical communication, the signal light is continuously input to the optical fiber amplifier and amplified by the gain optical path 110. Therefore, from a dynamic point of view, in addition to the signal light amplified for the first time by the gain optical path 110, the signal light has been coupled with the auxiliary light by the coupler 130 before amplification.

[0024] In practical applications, signal light can be transmitted by different wavebands. Among them, the C waveband has smaller transmission loss, so the current mainstream optical communication network adopts a dual waveband transmission mode of C waveband + another waveband (such as L waveband).

[0025] Considering that the signal light of the C waveband has a smaller noise figure after being amplified by the optical fiber amplifier than the signal light of other wavebands, the first filter 120 of the present embodiment only retains the auxiliary light of the C waveband after filtering the backward spontaneous emission light. That is, the auxiliary light meeting the preset requirements described above refers to the auxiliary light of the C waveband.

[0026] Correspondingly, the coupler 130 is an injection coupler for injecting the auxiliary light (C waveband) into the signal light to be amplified by the gain optical path 110, so that the auxiliary light and the signal light to be amplified by the gain optical path form a coupling.

[0027] Among them, Figure 2 is a comparison diagram of the noise figure of the optical fiber amplifier when injecting the auxiliary light of the C waveband and the noise figure when not injecting the auxiliary light of the C waveband. The vertical axis represents the value of the noise figure, and the horizontal axis represents the injection power of the auxiliary light of the C waveband. As can be seen from Figure 2, after injecting the auxiliary light of the C waveband, the noise figure of the optical fiber amplifier can be significantly reduced. In particular, when the injection power is in the interval of [-12dbm, -6dbm], the noise figure reduction effect is more obvious.

[0028] The optical fiber amplifier of the present application extracts the auxiliary light meeting the preset requirements from the backward spontaneous emission light generated by amplification when amplifying the current signal light, so as to combine the auxiliary light with the signal light which needs to be amplified later. The signal light after the combination of the auxiliary light can enhance the population inversion generated when being amplified, thereby effectively reducing the noise figure of the optical fiber amplifier. After the optical fiber amplifier of the present application is deployed to the optical communication network, the transmission quality of the signal light can be improved. In addition, the auxiliary light is filtered from the backward spontaneous emission light generated by the amplification of the signal light, and the optical fiber amplifier does not need to introduce an additional light source, and the overall structure is simple and easy to implement in engineering.

[0029] The structure of the optical fiber amplifier will be described in detail below.

[0030] Referring to FIG. 3, in the present embodiment, the main structure of the gain optical path 110 is composed of a plurality of optical gain media (such as erbium-doped optical fiber) cascaded with each other. The signal light entering the optical fiber amplifier can be individually power-amplified by each optical gain medium in the gain optical path 110 and finally output by one port. Among them, the plurality of optical gain media in the gain optical path 110 can be cascaded in any one of the series connection mode shown in FIG. 3(a), the parallel connection mode shown in FIG. 3(b), and the series-parallel connection hybrid mode shown in FIG. 3(c), which is not limited herein.

[0031] Here, the series connection mode shown in FIG. 4 is taken as an example. The first filter 120 can be arranged between the plurality of optical gain media, so that the plurality of optical gain media are divided into forward optical gain media and backward optical gain media with respect to the first filter, and the first filter is used to filter the backward spontaneous emission light (the direction of the dashed arrow represents the transmission direction of the backward spontaneous emission light) generated by all the backward optical gain media, so as to obtain the auxiliary light of the C band.

[0032] In addition, referring to FIG. 5, the optical fiber amplifier of the present embodiment can also introduce an optical splitter 140 on the basis of FIG. 4. The splitter 140 is used to split the backward spontaneous emission light generated by all the backward optical gain media to the first filter 120. It should be understood that the signal light after amplification by the forward optical gain media and the backward spontaneous emission light generated by the backward gain media are in opposite transmission directions, and the arrangement of the splitter 140 can separate the transmission path of the backward spontaneous emission light from the transmission path of the signal light after amplification by the optical gain media, thereby reducing the interference of the backward spontaneous emission light on the signal light.

[0033] It should be noted that the above is the basic structure of the gain optical path 110. In actual applications, the gain optical path 110 also needs to be provided with a pump, a backward filter of the optical gain medium, and an optical attenuator and the like. Among them, the pump is used to excite the signal light, that is, the particle number inversion mentioned above; the backward filter is used to filter the noise light generated by the signal light generated by the optical gain medium; and the optical attenuator is used to adjust the power of the signal light to keep the signal light in the specified power interval for transmission.

[0034] The connection relationship of the internal devices of the optical fiber amplifier will be introduced below in combination with the implementation mode. The following content is only for the convenience of understanding the implementation details, and is not a necessary choice for implementing the scheme.

[0035] FIG. 6 is a schematic diagram of the connection relationship of the internal devices of the optical fiber amplifier of the embodiment. IN represents the input end of the optical fiber amplifier, OUT represents the output end of the optical fiber amplifier, and the path direction from IN to OUT represents the transmission direction of the signal light.

[0036] The gain optical path includes: four optical gain media EDF1, EDF2, EDF3 and EDF4 connected in series; seven pumps WDM1, WDM2, WDM3, WDM4, WDM5, WDM6 and WDM7; and four second filters GFF1, GFF2, GFF3 and GFF4.

[0037] Among them, WDM1 is the forward pump of EDF1, WDM2 and WDM3 are the bidirectional pumps of EDF2, WDM4 and WDM5 are the bidirectional pumps of EDF3, and WDM6 and WDM7 are the bidirectional pumps of EDF4. The functions of WDM1 to WDM7 are to excite the signal light particle number inversion to emit in the transmission direction. In addition, GFF1 is the backward filter of EDF1, which is used to filter the noise of the signal light output by EDF1; GFF2 is the backward filter of EDF2, which is used to filter the noise of the signal light output by EDF2; GFF3 is the backward filter of EDF3, which is used to filter the noise of the signal light output by EDF3; and GFF4 is the backward filter of EDF4, which is used to filter the noise of the signal light output by EDF4.

[0038] It should be understood that the number of optical gain media shown in FIG. 6 can be flexibly set according to actual needs. Regardless of the number of optical gain media, the gain optical path will set a forward pump for the first optical gain medium in the signal light transmission direction, and a bidirectional pump for each optical gain medium except the first optical gain medium. In addition, each optical gain medium corresponds to a second filter for noise filtering.

[0039] Further, Filter represents a first filter, and an input end F-portl of Filter is connected to a path between EDF2 and EDF3. In this way, EDF1 and EDF2 are forward optical gain media of Filter, and EDF3 and EDF4 are backward optical gain media of Filter. Filter is used to filter the backward spontaneous emission light generated by EDF3 and EDF4 to obtain auxiliary light.

[0040] Circulator represents an optical circulator, which is a type of optical splitter. The Circulator of the present embodiment is provided with three ports, i.e., a first port portl, a second port port2 and a third port port3. In the absence of all pump and second filter, the first port portl is connected to the nearest forward optical gain medium EDF2 of the first filter Filter, the second port port2 is connected to the nearest backward optical gain medium EDF3 of the first filter Filter, and the third port port3 is connected to the input end F-portl of the first filter Filter. Among them, the first port portl and the second port port2 form an optical branch for transmitting signal light, and the second port port2 and the third port port3 form an optical branch for transmitting backward spontaneous emission light. That is, the backward spontaneous emission light generated by EDF3 and EDF4 reaches the first filter Filter by avoiding the transmission path of the signal light.

[0041] Further, Coupler represents a coupler, and an input end C-portl of Coupler is connected to both the input end IN of the whole fiber amplifier and the output end F-port2 of the first filter Filter. That is, the signal light subsequently entering the fiber amplifier and the auxiliary light output by the first filter Filter reach the Coupler together, and the Coupler performs beam combination.

[0042] It should be noted that the signal light entering the fiber amplifier needs to pass through the coupler to reach the optical gain medium EDF1, EDF2, EDF3 and EDF4 in turn for amplification. Therefore, the output end C-port2 of the coupler needs to be connected with at least the first optical gain medium EDF1 in the signal light transmission direction. In addition, with reference to the dashed line shown in FIG. 7, the output end C-port2 of the coupler can also be connected with any other optical gain medium EDF2, EDF3 and EDF4 except the first optical gain medium EDF1. As an example, assuming that the output end C-port2 of the coupler is connected with EDF1 (mandatory), EDF3 (optional) and EDF4 (optional), the population inversion at EDF1, EDF3 and EDF4 can be enhanced; similarly, assuming that the output end C-port2 of the coupler is connected with only EDF1 (mandatory), the population inversion at EDF1 can be enhanced.

[0043] In addition, the fiber amplifier further comprises a first optical attenuator VOA1 and a second optical attenuator VOA2. The first optical attenuator VOA1 is arranged between the first filter Filter and the coupler Coupler, and is used to correct the power of the auxiliary light output by the first filter Filter. The second optical attenuator VOA2 is arranged between the nearest forward optical gain medium EDF2 of the first filter Filter and the first port port1 of the optical circulator Circulator, and is used to correct the power of the signal light in the gain light path.

[0044] The above describes the internal device connection structure of the fiber amplifier of the embodiment. In related applications, the fiber amplifier of the embodiment can be deployed in an L-band signal light transmission network to solve the problem of large noise coefficient of the amplified L-band signal light. Taking the fiber amplifier shown in FIG. 6 as an example, the working process of the fiber amplifier is as follows.

[0045] After the optical fiber amplifier is turned on, the L-band signal light first entering from the input end IN directly passes through the coupler Coupler and is amplified by the optical gain medium EDF1-EDF4 in turn under the lasing action of the pumps WDM1-WDM7. In this amplification process, the L-band signal light is adjusted to an appropriate power by the second optical attenuator VOA2 and finally reaches the output end OUT to be emitted through the optical branching formed by the first port port1 and the second port port2 of the optical circulator Circulator to reach the next node of the transmission network. At the same time, the optical gain medium EDF3-4 generates multi-band backward spontaneous emission light in the amplification process of the L-band signal light. The backward spontaneous emission light reaches the first filter Filter through the optical branching formed by the first port port2 and the second port port3 of the optical circulator Circulator, and the C-band auxiliary light is retained after being filtered by the first filter Filter. Then, the C-band auxiliary light reaches the coupler Coupler after being adjusted to an appropriate power by the first optical attenuator VOA1. At this time, the L-band signal light entering through the input end IN is also injected into the coupler Coupler by the C-band auxiliary light to complete beam combining.

[0046] After the optical fiber amplifier is turned on, the L-band signal light first entering from the input end IN directly passes through the coupler Coupler and is amplified by the optical gain medium EDF1-EDF4 in turn under the lasing action of the pumps WDM1-WDM7. In this amplification process, the L-band signal light is adjusted to an appropriate power by the second optical attenuator VOA2 and finally reaches the output end OUT to be emitted through the optical branching formed by the first port port1 and the second port port2 of the optical circulator Circulator to reach the next node of the transmission network. At the same time, the optical gain medium EDF3-4 generates multi-band backward spontaneous emission light in the amplification process of the L-band signal light. The backward spontaneous emission light reaches the first filter Filter through the optical branching formed by the first port port2 and the second port port3 of the optical circulator Circulator, and the C-band auxiliary light is retained after being filtered by the first filter Filter. Then, the C-band auxiliary light reaches the coupler Coupler after being adjusted to an appropriate power by the first optical attenuator VOA1. At this time, the L-band signal light entering through the input end IN is also injected into the coupler Coupler by the C-band auxiliary light to complete beam combining.

[0047] For the L-band signal light entering the fiber amplifier from the input end IN later, the C-band auxiliary light will reach the coupler Coupler together with the L-band signal light before, and the C-band auxiliary light is injected into the L-band signal light after the beam combining is completed by the coupler Coupler. At this point, in addition to the L-band signal light entering from the input end IN for the first time, the subsequent L-band signal light can be combined with the C-band auxiliary light at the coupler Coupler, so that the L-band signal light after the beam combining can produce stronger particle inversion when amplifying in the optical gain medium EDF1, thereby reducing the noise figure of the fiber amplifier relative to the L-band signal light, and then improving the power attenuation of the L-band signal light in the transmission process, which can significantly extend the transmission distance of the L-band signal light.

[0048] The above only describes the embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the embodiments of the present application, a number of improvements and refinements can be made, which should be considered as the protection scope of the embodiments of the present application.

[0049] Each of the embodiments in the present application is described in a progressive manner, and the same or similar parts of each embodiment can be referred to each other, and each embodiment mainly explains the difference from other embodiments. Especially, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the related parts can be referred to the part of the method embodiment.

[0050] In addition, those skilled in the art should understand that the above-mentioned modules or steps of the present application can be realized by a general computing device, which can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, which can be realized by program code executable by the computing device, so that they can be stored in the storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in different order, or they can be manufactured into individual integrated optical modules, or multiple modules or steps can be manufactured into a single integrated optical module. Thus, the present application is not limited to any specific hardware and software combination.

Claims

1. An optical fiber amplifier, comprising: Gain optical path, used to amplify signal light; The first filter is used to filter the back-emission light generated by the amplified signal light in the gain optical path, and retain the auxiliary light that meets the preset requirements. A coupler is used to combine the auxiliary light with the signal light to be amplified by the gain optical path, so as to enhance the population inversion generated by the amplification of the combined signal light by the gain optical path.

2. The fiber optic amplifier according to claim 1, wherein, Also includes: An optical splitter is used to split the back-emission light generated by the gain optical path to the first filter.

3. The fiber optic amplifier according to claim 2, wherein, The gain optical path includes multiple cascaded optical gain media, each of which is used to amplify the passing signal light; the first filter is used to filter the backscattered spontaneous emission light generated by at least one of the optical gain media. The coupler is used to combine the auxiliary light with the signal light to be amplified by at least one of the optical gain media.

4. The fiber optic amplifier according to claim 3, wherein, The plurality of optical gain media are connected in series, and the first filter is disposed between the plurality of optical gain media, so that the plurality of optical gain media are divided into forward optical gain media and backward optical gain media for the first filter. The first filter is used to filter the backward spontaneous emission light generated by all the backward optical gain media.

5. The fiber optic amplifier according to claim 4, wherein, The gain optical path further includes a forward pump for the first optical gain medium in the signal light transmission direction, and a bidirectional pump for each optical gain medium other than the first optical gain medium.

6. The fiber amplifier according to claim 4, wherein, The optical splitter is an optical circulator, including a first port, a second port, and a third port; wherein, the first port is connected to the nearest forward optical gain medium of the first filter, the second port is connected to the nearest backward optical gain medium of the first filter, and the third port is connected to the input end of the first filter; the first port and the second port form an optical splitter, and the second port and the third port form an optical splitter.

7. The fiber optic amplifier according to claim 6, wherein, The input end of the coupler is connected to the output end of the first filter, and the output end of the coupler is used to receive the signal light entering the optical fiber amplifier and is connected to at least one optical gain medium, including the first optical gain medium in the optical transmission direction.

8. The fiber optic amplifier according to claim 3, wherein, The gain optical path further includes a second-direction filter corresponding to each of the optical gain media, the second-direction filter being used to filter noise in the signal light output by the corresponding optical gain media.

9. The fiber optic amplifier according to claim 1, wherein, The preset requirements include the C-band. The coupler injects the auxiliary light into the signal light to be amplified by the gain optical path, so that the auxiliary light and the signal light to be amplified by the gain optical path form a combined beam. The injection power range corresponding to the auxiliary light is [-12dBm, -6dBm].

10. The fiber optic amplifier according to any one of claims 1 to 9, wherein, Also includes: A first optical attenuator is used to correct the power of the auxiliary light; and / or The second optical attenuator is used to correct the power of the signal light in the gain optical path.

11. The fiber optic amplifier according to any one of claims 1 to 9, wherein, The second-direction filter is a gain-flattening filter, and the optical gain medium is erbium-doped fiber.

Images