A gain flattening filter, multi-core fiber amplifier, and signal transmission system

Abstract

The utility model relates to optical communication technical field especially relates to a kind of gain flat filter, multicore fiber amplifier and signal transmission system, gain flat filter includes multicore fiber;Etching corresponding grating in each fiber core of the multicore fiber.The utility model etches grating in each fiber core of multicore fiber, thereby can carry out gain flat to each fiber core in multicore fiber amplifier, realizes a kind of independent device that can carry out gain flat to multicore fiber amplifier, thereby need not extra fan in fan out, only using the gain flat filter of the utility model can realize the gain flat of each signal transmission channel in multicore fiber amplifier, compact structure, it is convenient to apply.

Description

Technical Field

[0001] This utility model relates to the field of optical communication technology, and in particular to a gain-flattening filter, a multi-core fiber amplifier, and a signal transmission system. Background Technology

[0002] With the continuous and rapid growth of Internet Protocol (IP) services such as Artificial Intelligence (AI), 5G, Internet+, big data, and cloud computing, the demand for network bandwidth is becoming increasingly high. Traditional Dense Wavelength Division Multiplexing (DWDM) can no longer meet the bandwidth requirements, and Space Division Multiplexing (SDM) has become a current research hotspot. Multi-core / multi-core few-mode fiber amplifiers are key components in SDM network transmission, especially in transoceanic transmission systems, where multi-core amplifiers have greater application potential. Therefore, the demand for multi-core and multi-core few-mode fiber amplifiers is becoming increasingly urgent.

[0003] In multi-core fiber amplifiers, the absorption of pump light varies among different fiber cores, resulting in poor gain consistency. For a 7-core fiber amplifier, the gain difference between different cores can exceed 3dB, making it practically unusable for long-distance transmission systems. To date, research on multi-core amplifiers has not addressed the application of gain flattening filters in multi-wavelength applications. Existing technologies lack independent devices capable of performing gain flattening filtering on each fiber core of a multi-core fiber amplifier. One feasible approach is to introduce a gain flattening filter (GFF) from a single-mode fiber into the multi-mode fiber amplifier via a fan-in / fan-out configuration. This requires converting the existing multi-core fiber to single-mode fiber via fan-in / fan-out, and then connecting gain flattening filters to each single-mode fiber. This approach requires multiple gain flattening filters, resulting in a non-compact structure and negating the purpose of using multi-core fiber for spatial multiplexing. Utility Model Content

[0004] The present invention overcomes the problem that there is no independent device in the prior art that can perform gain flattening filtering on each fiber core of a multi-core fiber amplifier.

[0005] This utility model is implemented as follows: In a first aspect, this utility model provides a gain-flattening filter, comprising a multi-core optical fiber 1; Each core 11 of the multi-core optical fiber 1 is etched with a corresponding grating 111.

[0006] Secondly, this utility model provides a multi-core fiber amplifier, including a pump component 2, a first coupling component 3, a multi-core doped fiber 4, and the gain flattening filter 5 described in the first aspect. The pump assembly 2 generates multiple pump beams; The first coupling component 3 transmits the combined wave of the i-th pump light and the i-th signal light to the i-th fiber core in the multi-core doped fiber 4; The gain-flattening filter 5 performs gain-flattening filtering on each channel after amplification by the multi-core doped fiber 4.

[0007] Preferably, the first coupling component 3 is a multi-core coupler; The i-th reflecting end of the multi-core coupler is connected to the i-th pump output end of the pump assembly 2; The i-th common end of the multi-core coupler is connected to the i-th core of the multi-core doped optical fiber 4; The i-th transmission end of the multi-core coupler is used as the i-th signal input end of the multi-core fiber amplifier.

[0008] Preferably, the pump assembly 2 includes a plurality of pump lasers; The output of the i-th pump laser is used as the i-th pump output of the pump assembly 2.

[0009] Preferably, it also includes a multi-core fiber optic adjustable attenuator.

[0010] Preferably, it also includes a first multi-channel isolator 6; The first multi-channel isolator 6 is disposed at the i-th signal input end of the multi-core fiber amplifier, and the i-th channel of the first multi-channel isolator 6 is disposed on the transmission optical path of the i-th signal light.

[0011] Preferably, it also includes a second multi-channel isolator 7; The second multi-channel isolator 7 is disposed at the i-th signal output end of the multi-core fiber amplifier, and the i-th channel of the second multi-channel isolator 7 is disposed on the transmission optical path of the i-th signal light.

[0012] Preferably, it also includes a second coupling component 8 and a detection component 9; The second coupling component 8 is used to split the i-th output signal light to obtain the i-th detection light, and transmit the i-th detection light to the i-th detection port of the detection component 9.

[0013] Preferably, the detection component 9 includes multiple detectors; The input terminal of the i-th detector is used as the i-th detection port of the detection component 9.

[0014] Thirdly, this embodiment provides a signal transmission system, including a transmitter, a receiver, and a multi-core fiber optic amplifier as described in either the second aspect.

[0015] Compared with the prior art, the beneficial effects of this utility model are as follows: This utility model can perform gain flattening on each fiber core of a multi-core fiber amplifier by etching gratings in each fiber core, thus realizing an independent device (i.e., gain flattening filter) that can perform gain flattening on a multi-core fiber amplifier. Therefore, there is no need for additional fan-in and fan-out. The gain flattening filter described in this utility model can achieve gain flattening on each signal transmission channel in a multi-core fiber amplifier. It has a compact structure and is easy to apply. Attached Figure Description

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

[0017] Figure 1 A schematic diagram of the structure of a gain-flattening filter provided in an embodiment of this utility model; Figure 2 A schematic diagram of the structure of the first type of multi-core fiber optic amplifier provided in this embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a second type of multi-core fiber optic amplifier provided in an embodiment of the present invention; Figure 4 A schematic diagram of the structure of the third type of multi-core fiber optic amplifier provided in this embodiment of the present invention; Figure 5 A schematic diagram of the structure of the fourth type of multi-core fiber optic amplifier provided in this embodiment of the present invention; Figure 6 A schematic diagram of the structure of the fifth type of multi-core fiber optic amplifier provided in this embodiment of the present invention; Figure 7 A schematic diagram of the structure of the sixth type of multi-core fiber optic amplifier provided in this embodiment of the present invention; Figure 8 This is a schematic diagram of a signal transmission system provided in an embodiment of the present invention.

[0018] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1. Multi-core optical fiber; 11. Fiber core; 111. Grating; 2. Pump assembly; 3. First coupling assembly; 4. Multi-core doped optical fiber; 5. Gain flattening filter; 6. First multi-channel isolator; 7. Second multi-channel isolator; 8. Second coupling assembly; 9. Detection assembly; 10. Third multi-channel isolator. Detailed Implementation

[0019] In the description of this utility model, the terms "inner", "outer", "longitudinal", "lateral", "upper", "lower", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and do not require that this utility model must be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0020] In this utility model, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0021] In this application, unless otherwise expressly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the term "coupled" can refer to an electrical connection that enables signal transmission.

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0023] Example 1: This utility model embodiment provides a gain-flattening filter, such as Figure 1 As shown, it includes a multi-core optical fiber 1; each core 11 of the multi-core optical fiber 1 is etched with a corresponding grating 111. The grating 111 can be a Fiber Bragg Grating (FBG).

[0024] Each fiber core 11 can be considered as a gain-flattening filter channel, used to flatten the gain of light passing through the channel. The length of the grating 111 and the grating constant (i.e., the distance between adjacent grating elements) of each fiber core 11 can be different. The specific length and grating constant are determined by those skilled in the art based on the wavelength of the signal light transmitted in each fiber core 11 and the transmission requirements of the system. The grating 111 in each fiber core 11 is used to flatten the gain of one signal transmission channel in the multi-core fiber amplifier.

[0025] This embodiment achieves gain flattening of each fiber core in the multi-core fiber amplifier by etching gratings 111 in each fiber core 11 of the multi-core fiber 1. This realizes an independent device (i.e., gain flattening filter) capable of gain flattening of the multi-core fiber amplifier, thus eliminating the need for additional fan-in and fan-out. Gain flattening of each signal transmission channel in the multi-core fiber amplifier can be achieved using only the gain flattening filter described in this embodiment. The structure is compact and easy to apply.

[0026] Example 2: Based on the gain-flattening filter described in Example 1, this embodiment also provides a multi-core fiber amplifier, such as... Figure 2 or Figure 3 As shown, the system includes a pump assembly 2, a first coupling assembly 3, a multi-core doped fiber 4, and a gain-flattening filter 5 as described in Example 1. The pump assembly 2 generates multiple pump beams. The first coupling assembly 3 combines the i-th pump beam and the i-th signal beam and transmits them to the i-th core of the multi-core doped fiber 4. The multi-core doped fiber 4 can be doped with one or more of erbium, bismuth, ytterbium, or other rare earth elements, and different cores can be doped with different elements to amplify signal light of different wavelengths. The gain-flattening filter 5 performs gain-flattening filtering on each channel after amplification by the multi-core doped fiber 4.

[0027] The multi-core fiber amplifier can be implemented using forward pumping (i.e., the signal light and pump light are injected into the multi-core doped fiber 4 from the same direction, such as...). Figure 2 (as shown) or backward pumping (i.e., the signal light and pump light are injected into the multi-core doped fiber from different directions, such as...) Figure 3 (As shown).

[0028] When the multi-core fiber amplifier is used in a forward-pumped manner, such as Figure 2 As shown, the first coupling component 3 and the pump component 2 are located on the signal input side of the multi-core doped optical fiber 4, and the gain flattening filter 5 is located on the signal output side of the multi-core doped optical fiber 4.

[0029] When the multi-core fiber amplifier is back-pumped, such as Figure 3As shown, the first coupling component 3, the pump component 2, and the gain flattening filter 5 are all located on the side where the signal output end of the multi-core doped optical fiber 4 is located.

[0030] In some alternative implementations, such as Figure 4 As shown, the multi-core fiber amplifier includes two pump components 2 and two first coupling components 3. The two pump components 2 and the corresponding first coupling components 3 are respectively arranged in two directions of the multi-core doped fiber 4 to realize bidirectional pumping. One pump component 2 and the corresponding first coupling component 3 are arranged on the side where the signal input end of the multi-core doped fiber 4 is located. This pump component 2 is used to generate multiple first pump lights. The first pump lights and the signal light are injected into the multi-core doped fiber 4 from the same direction. The other pump component 2, the corresponding first coupling component 3 and the gain flattening filter 5 are arranged on the side where the signal output end of the multi-core doped fiber 4 is located. This pump component 2 is used to generate multiple second pump lights. The second pump lights and the signal light are injected into the multi-core doped fiber 4 from different directions.

[0031] It should be noted that in the following embodiments and accompanying drawings, the multi-core fiber amplifier will be shown and described in the form of forward pumping, but this does not mean that the form of the multi-core fiber amplifier is limited.

[0032] In a practical application scenario, the first coupling component 3 is a multi-core coupler; the i-th reflecting end of the multi-core coupler is connected to the i-th pump output end of the pump component 2; the i-th common end of the multi-core coupler is connected to the i-th fiber core of the multi-core doped optical fiber 4; and the i-th transmitting end of the multi-core coupler is used as the i-th signal input end of the multi-core optical fiber amplifier.

[0033] The multi-core coupler combines the pump light incident at the i-th reflecting end with the signal light incident at the i-th transmitting end and transmits them to the i-th core of the multi-core doped fiber 4 for optical amplification.

[0034] In one optional embodiment, the pump assembly 2 includes a plurality of pump lasers; the output terminal of the i-th pump laser is used as the i-th pump output terminal of the pump assembly 2.

[0035] In a preferred embodiment, the multi-core fiber amplifier further includes a multi-core fiber adjustable attenuator, wherein the i-th input terminal of the multi-core fiber adjustable attenuator is coupled to the i-th output terminal of the gain flat filter 5, thereby enabling independent attenuation adjustment of the signal light of each fiber core.

[0036] In practical use, such as Figure 5As shown, the multi-core fiber amplifier described in this embodiment also includes a first multi-channel isolator 6; the first multi-channel isolator 6 is disposed at the i-th signal input end of the multi-core fiber amplifier, and the i-th channel of the first multi-channel isolator 6 is disposed on the transmission optical path of the i-th signal light, so as to perform optical isolation on the signal input end.

[0037] Furthermore, it also includes a second multi-channel isolator 7; the second multi-channel isolator 7 is disposed at the i-th signal output terminal of the multi-core fiber amplifier, and the i-th channel of the second multi-channel isolator 7 is disposed in the transmission optical path of the i-th signal light to provide optical isolation for the signal output terminal. In an optional embodiment, the i-th input terminal of the second multi-channel isolator 7 is connected to the i-th output terminal of the gain flattening filter 5. In some embodiments, the multi-core fiber amplifier further includes a third multi-channel isolator 10, which is disposed between the multi-core doped fiber 4 and the gain flattening filter 5.

[0038] In a preferred embodiment, such as Figure 6 As shown, the multi-core fiber amplifier also includes a second coupling component 8 and a detection component 9; the second coupling component 8 is used to split the i-th output signal light to obtain the i-th detection light, and transmit the i-th detection light to the i-th detection port of the detection component 9; the detection component 9 is used to detect the optical power of each detection light, thereby for signal gain control.

[0039] In one optional implementation, the detection component 9 includes a plurality of detectors; the input terminal of the i-th detector is used as the i-th detection port of the detection component 9.

[0040] In practical applications, the multi-core fiber amplifier can also be a multi-stage amplifier, such as... Figure 7 As shown, the system includes two multi-core doped optical fibers 4. A third multi-channel isolator 10, a gain flattening filter 5, and a second multi-channel isolator 7 are connected between the two multi-core fiber amplifiers. A first multi-channel coupler and a pump assembly 2 are also connected between them. The pump assembly 2 is used to provide pump light to the second multi-core doped optical fiber 4. On the signal input side (i.e., before the first multi-core doped optical fiber 4), a second coupling assembly 8, a detection assembly 9, a first multi-channel isolator 6, a first coupling assembly 3, and the pump assembly 2 are connected. The detection assembly 9 is used to detect the optical power of the input signal light. On the signal output side (i.e., after the second multi-core doped optical fiber 4), a second multi-channel isolator 7, a second coupling assembly 8, and the detection assembly 9 are connected. The detection assembly 9 is used to detect the optical power of the output signal light.

[0041] Furthermore, the multi-core fiber amplifier may also include a microcontroller unit (MCU), which is used to control each pump component 2 according to the optical power output by each detection component 9, thereby realizing the gain control of the multi-core fiber amplifier.

[0042] Based on the aforementioned multi-core fiber amplifier, this embodiment also provides a signal transmission system, such as... Figure 8 As shown, the system includes a transmitter, a receiver, and the aforementioned multi-core fiber optic amplifier, wherein the signal in the signal transmission system is transmitted using multi-core fiber optic cable.

[0043] In practical applications, the first coupling component 3 can be a multi-core fiber pump / signal combiner, the second coupling component 8 can be a multi-core fiber splitter, and the pump component 2 can be a pump laser array.

[0044] Example 3: In the prior art, the gain of each fiber core in a multi-core fiber amplifier cannot be independently controlled. To solve this problem, this embodiment provides an integrated multi-core fiber amplifier with inter-core gain equalization. The gain of each core can be independently controlled, and the existing multi-core amplifiers have problems such as large differences in inter-core gain, only automatic current control, and no automatic gain or automatic power control in various application scenarios.

[0045] like Figure 7 As shown, the multi-core fiber amplifier provided in this embodiment includes, in sequence, an input multi-core fiber splitter (i.e., the second coupling component 8), a multi-core fiber isolator (i.e., the first multi-channel isolator 6), a multi-core fiber pump signal combiner (i.e., the first coupling component 3), a multi-core doped fiber 4, a multi-core fiber isolator (i.e., the third multi-channel isolator 10), a multi-core fiber gain filter (i.e., the gain flattening filter 5 described in Embodiment 2), a multi-core fiber isolator (i.e., the first multi-channel isolator 6), a multi-core doped fiber 4, an output multi-core fiber splitter (i.e., the second coupling component 8 in Embodiment 2), an input photodetector (i.e., the detection component 9 located on the signal input side), and an output photodetector (i.e., the detection component 9 located on the signal output side). The fiber amplifier also includes a control unit (i.e., a microcontroller) for controlling according to the expected amplification requirements. The multi-core doped fiber 4 is one or more of erbium-doped fiber, erbium-ytterbium co-doped fiber, or other rare-earth-doped fibers.

[0046] Based on the expected amplification requirements, the gain in each fiber core needs to be balanced across the entire wavelength range, necessitating a multi-core gain-flattening filter 5. Traditional thin-film filter methods are insufficient to meet the process requirements of multi-core amplifiers. To address this issue, this embodiment also provides a gain-flattening filter 5. Specifically, the gain-flattening filter 5 is implemented by etching fiber gratings 111, thereby realizing a multi-core gain-flattening filter 5. Furthermore, the gain of each fiber core can be individually controlled by monitoring the input and output power of each fiber. If a gain-adjustable multi-core fiber amplifier is desired, a multi-core fiber tunable attenuator is added to the optical path.

[0047] In a practical application scenario, the optical path diagram of the multi-core fiber amplifier provided in this embodiment is as follows: Figure 7 As shown, the signal light enters the amplifier from the input port of the multi-core fiber, and a portion of the light is split off by the second coupling component 8 and enters the detector component 9 through the small output end. The second coupling component 8 splits the light using a tapered or filter-like form. The input port, small output port, and large output port of this device are all multi-core fibers. The signal light enters the input port of the first multi-channel isolator 6 through the large output end of the second coupling component 8. The input port of the first multi-channel isolator 6 is connected to the signal port of the first coupling component 3. The signal port and common port of the first coupling component 3 are multi-core fibers. The pump end of the first coupling component 3 is a single-mode fiber, the number of which is the same as the number of cores in the multi-core fiber. Each fiber of the pump end of the first coupling component 3 is connected to one of the pump lasers of each single-mode pump component 2. The common port of the first coupling component 3 is connected to the first segment of multi-core doped fiber 4 (gain fiber). The other end of the multi-core doped fiber 4 is connected to the third multi-channel isolator 1. The input terminal of the first coupling component 3 is connected to the input terminal of the third multi-channel isolator 10. The output terminal of the third multi-channel isolator 10 is connected to the input terminal of the gain flattening filter 5. The output terminal of the gain flattening filter 5 is connected to the input terminal of the second multi-channel isolator 7. The output terminal of the second multi-channel isolator 7 is connected to the signal terminal of another first coupling component 3. The pump end of the first coupling component 3 is a single-mode fiber, the number of which is the same as the number of cores in the multi-core fiber. Each fiber of the pump end of the first coupling component 3 is connected to one of the pump lasers of each single-mode pump component 2. The common terminal of the first coupling component 3 is connected to the second multi-core doped fiber 4 (gain fiber). The other end of the multi-core doped fiber 4 is connected to the input terminal of another second multi-channel isolator 7. The output terminal of the second multi-channel isolator 7 is connected to the input terminal of another second coupling component 8. The small output terminal of the second coupling component 8 enters the detection component 9 for output light detection. The large output terminal of the second coupling component 8 is the amplifier output port. The microcontroller controls the pump power through the input and output power detection corresponding to each fiber core, so that the amplifier meets the automatic gain or automatic power control.

[0048] The traditional approach is to use fan-in and fan-out, where each fiber core is balanced by a gain flattening filter 5 in the form of a thin-film filter. This embodiment proposes a method to achieve gain flattening filter 5 to balance the gain of each fiber core by directly writing fiber gratings in multi-core optical fibers, resulting in a more compact size.

[0049] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A gain-flattening filter, characterized in that, Including multi-core optical fiber (1); Each core (11) of the multi-core optical fiber (1) is etched with a corresponding grating (111).

2. A multi-core fiber optic amplifier, characterized in that, It includes a pump assembly (2), a first coupling assembly (3), a multi-core doped fiber (4), and a gain-flattening filter (5) as described in claim 1; The pump assembly (2) generates multiple pump beams; The first coupling component (3) transmits the combined wave of the i-th pump light and the i-th signal light to the i-th core of the multi-core doped fiber (4); The gain-flattening filter (5) performs gain-flattening filtering on each channel after amplification by the multi-core doped fiber (4).

3. The multi-core fiber amplifier according to claim 2, characterized in that, The first coupling component (3) is a multi-core coupler; The i-th reflecting end of the multi-core coupler is connected to the i-th pump output end of the pump assembly (2); The i-th common end of the multi-core coupler is connected to the i-th core of the multi-core doped optical fiber (4); The i-th transmission end of the multi-core coupler is used as the i-th signal input end of the multi-core fiber amplifier.

4. The multi-core fiber amplifier according to claim 2, characterized in that, The pump assembly (2) includes multiple pump lasers; The output of the i-th pump laser is used as the i-th pump output of the pump assembly (2).

5. The multi-core fiber amplifier according to claim 2, characterized in that, It also includes multi-core fiber optic adjustable attenuators.

6. The multi-core fiber amplifier according to claim 2, characterized in that, It also includes the first multi-channel isolator (6); The first multi-channel isolator (6) is located at the i-th signal input end of the multi-core fiber amplifier, and the i-th channel of the first multi-channel isolator (6) is located on the transmission optical path of the i-th signal light.

7. The multi-core fiber amplifier according to claim 2, characterized in that, It also includes a second multi-channel isolator (7); The second multi-channel isolator (7) is located at the i-th signal output end of the multi-core fiber amplifier, and the i-th channel of the second multi-channel isolator (7) is located on the transmission optical path of the i-th signal light.

8. The multi-core fiber amplifier according to claim 2, characterized in that, It also includes a second coupling component (8) and a probe component (9); The second coupling component (8) is used to split the i-th output signal light to obtain the i-th detection light, and transmit the i-th detection light to the i-th detection port of the detection component (9).

9. The multi-core fiber amplifier according to claim 8, characterized in that, The detection component (9) includes multiple detectors; The input terminal of the i-th detector is used as the i-th detection port of the detection component (9).

10. A signal transmission system, characterized in that, It includes a transmitter, a receiver, and a multi-core fiber amplifier as described in any one of claims 2 to 9.

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