A high-gain fiber amplifier

Abstract

This invention discloses a high-gain fiber amplifier, comprising a circulator, a laser, a wavelength division multiplexer, a gain fiber, a pump reflector, and a filter reflector arranged sequentially. The signal light, after entering through the circulator, is coupled with the pump light (input through the laser) via the wavelength division multiplexer to the gain fiber and then enters the pump reflector. In the pump reflector, the pump light is reflected back into the gain fiber. The signal light, after being reflected by the filter reflector, passes sequentially through the pump reflector, the gain fiber, and the wavelength division multiplexer before being output from the circulator. This invention achieves two-way amplification of the signal light through the circulator and Faraday reflector. Simultaneously, the filtering device allows only the laser of the signal wavelength to pass through, filtering out amplified spontaneous emission light in the gain fiber, thus improving the signal-to-noise ratio and small-signal gain of the signal light. This solves the problems of low amplified signal power and poor signal-to-noise ratio in existing two-way amplification structures.

Description

Technical Field

[0001] This utility model relates to the fields of optical fiber communication and sensing, and specifically to a high-gain optical fiber amplifier. Background Technology

[0002] In traditional erbium-doped fiber amplifiers, high gain is typically achieved through two-stage or multi-stage amplification structures. These structures require multiple sets of passive fiber components such as gain fibers, wavelength division multiplexers, and isolators, leading to complexity, high cost, and hindering product miniaturization. Existing technologies have also proposed fiber amplifiers using fiber circulators for two-way amplification. This approach halves the amount of erbium-doped fiber used while maintaining the same optical gain, thus reducing production costs. However, due to the wide gain spectrum of erbium-doped fiber, this approach also amplifies spontaneous emission light in the two-way amplification structure. This amplified spontaneous emission light limits the energy extraction of the signal light, resulting in a poor signal-to-noise ratio and limited amplification gain at the amplified output. Furthermore, it is unsuitable for amplifying small-signal light. Utility Model Content

[0003] This invention addresses the problems in the prior art by disclosing a high-gain fiber amplifier. The invention achieves two-way amplification of the signal light through a circulator and a Faraday reflector. Simultaneously, the filtering device allows only laser light of the signal wavelength to pass through, filtering out amplified spontaneous emission light in the gain fiber, thereby improving the signal-to-noise ratio and small-signal gain. This solves the problems of low amplified signal power and poor signal-to-noise ratio in existing two-way amplification structures.

[0004] This utility model is achieved through the following technical solution:

[0005] This invention first provides a high-gain fiber amplifier, comprising a circulator, a laser, a wavelength division multiplexer, a gain fiber, a pump reflector, and a filter reflector arranged sequentially. The signal light is input through the circulator and coupled with the pump light input through the laser through the wavelength division multiplexer to the gain fiber, then enters the pump reflector. In the pump reflector, the pump light is reflected back into the gain fiber. The signal light is reflected by the filter reflector and then passes sequentially through the pump reflector, the gain fiber, and the wavelength division multiplexer before being output from the circulator.

[0006] As a further option, the circulator is a fiber optic circulator.

[0007] As a further option, the laser, wavelength division multiplexer, and gain fiber can form a forward pump or a backward pump.

[0008] As a further option, a pump isolator is inserted at the back end of the laser.

[0009] As a further option, the pump reflector is a fiber grating of the pump wavelength.

[0010] As a further option, the laser is a 980nm pumped semiconductor laser.

[0011] As a further option, the gain ions in the gain fiber include any one or more of neodymium ions, erbium ions, praseodymium ions, holmium ions, europium ions, ytterbium ions, dysprosium ions, and thulium ions.

[0012] As a further option, the gain fiber is erbium fiber.

[0013] As a further option, the filter reflector is a bandpass filter fiber optic mirror.

[0014] As a further option, the filter reflector includes a filter and a Faraday reflector arranged in sequence.

[0015] The features and beneficial effects of this utility model are as follows:

[0016] (1) This utility model achieves double-pass amplification of signal light through a circulator and a Faraday reflector. At the same time, the filter only allows the laser of the signal wavelength to pass through, filters out the amplified spontaneous emission light in the gain fiber, and improves the signal-to-noise ratio and small signal gain of the signal light. The pump reflector returns the remaining pump light to the gain fiber, which can reduce the length of the gain fiber. The use of the circulator, Faraday reflector, pump reflector and filter can improve the small signal gain.

[0017] (2) The fiber amplifier described in this utility model has a simple structure. Compared with the existing typical two-stage amplification structure, the structure of this application reduces multiple components, greatly reduces the production cost, and reduces the size of the product.

[0018] (3) The pump isolator provided in this utility model increases the stability of the fiber optic amplifier and extends its service life. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model, 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.

[0020] Figure 1 This is a schematic diagram of the forward pumping of the fiber amplifier according to an embodiment of the present invention. Figure 1 ;

[0021] Figure 2 This is a schematic diagram of the forward pumping of the fiber amplifier according to an embodiment of the present invention. Figure 2 ;

[0022] Figure 3 A schematic diagram showing the addition of a pump isolator to the fiber optic amplifier described in this embodiment of the invention;

[0023] Figure 4 This is a schematic diagram of the backward pumping of the fiber amplifier according to an embodiment of the present invention. Figure 1 ;

[0024] Figure 5 This is a schematic diagram of the backward pumping of the fiber amplifier according to an embodiment of the present invention. Figure 2 .

[0025] Explanation of reference numerals in the attached figures:

[0026] 1-Circulator; 2-Laser; 3-Wavelength division multiplexer; 4-Gain fiber; 5-Pump reflector; 6-Filter; 7-Faraday reflector; 8-Pump isolator; A-Filter reflector. Detailed Implementation

[0027] To facilitate understanding of this utility model, a more comprehensive description of this utility model will be provided below, along with embodiments of this utility model, but this does not limit the scope of this utility model.

[0028] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, 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. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0029] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0030] A high-gain fiber amplifier, such as Figures 1 to 5 As shown, the system includes a circulator 1, a laser 2, a wavelength division multiplexer 3, a gain fiber 4, a pump reflector 5, and a filter reflector A connected in sequence. The signal light, after being input through the circulator 1, is coupled with the pump light input through the laser 2 via the wavelength division multiplexer 3 to the gain fiber 4, and then enters the pump reflector 5. In the pump reflector 5, the pump light is reflected back into the gain fiber 4, improving the utilization rate of the pump light and reducing the length of the gain fiber. After being reflected by the filter reflector A, the signal light passes sequentially through the pump reflector 5, the gain fiber 4, and the wavelength division multiplexer 3 before being output from the circulator 1.

[0031] Compared with the existing typical two-stage amplification structure, the solution in this application reduces three devices, which can save costs and reduce the size of the product.

[0032] In some embodiments, the filter reflector A is a bandpass filter fiber optic reflector, preferably OFMBP-1064-08-22-NB-1.

[0033] In other embodiments, the filter reflector A includes a filter 6 and a Faraday reflector 7 arranged sequentially. The filter 6 performs filtering, and the Faraday reflector 7, while reflecting electromagnetic waves (such as light), uses the Faraday effect to fix their polarization direction, ensuring that the polarization state of the reflected light is not affected by the incident angle or minor system disturbances. Preferably, the filter 6 is model DWDM-1-C18-3.5x25-G657A2-1-0-N, and the Faraday reflector 7 is model ISO-FRDY-04-2050-N.

[0034] Circulator 1 is an optical fiber circulator. Preferably, its model number is MCPCIR-1550-3-CFD-P15-10-LN. Laser 2 is a pump semiconductor laser (LD), preferably model number MLU96ZW400-74H. Wavelength division multiplexer 3 is model number WDM-980 / 1550-2.5*30-HI1060flex-1.5-0-NC. Gain fiber 4 is erbium fiber. The gain ions in the gain fiber include any one or more of neodymium ions, erbium ions, praseodymium ions, holmium ions, europium ions, ytterbium ions, dysprosium ions, and thulium ions. Pump reflector 5 is a fiber grating for the pump wavelength, model number MPR980-APC-9 / 125. Pump isolator 8 is model number IO-P-980APC.

[0035] like Figure 2 As shown, in order to prevent the reflected pump light from being injected into laser 2 and affecting the output stability of laser 2, a pump isolator 8 can be inserted at the rear end of laser 2. This scheme is only used when the gain fiber is relatively short.

[0036] like Figure 3 As shown, laser 2, wavelength division multiplexer 3, and gain fiber 4 form a forward pump or a backward pump.

[0037] The working principle of a high-gain fiber optic amplifier is as follows. For ease of description, this application uses a filter reflector A, including a filter 6 and a Faraday reflector 7, as an example for illustration:

[0038] The amplified signal light is input through fiber optic circulator 1. Wavelength division multiplexer 3 couples the injected signal light and the pump light from the pump semiconductor laser (LD) 2 into the gain fiber. Under the action of the pump light, the gain fiber 4 forms a population inversion distribution, amplifying the input signal light. The remaining pump light is reflected back into the gain fiber 4 by pump reflector 5, improving the utilization rate of the pump light and reducing the length of the gain fiber. The filter device is a narrowband filter that only allows signal light of a specific amplification wavelength (such as C-band) to pass through, filtering out out-of-band stray light and pump leakage signal light. After passing through filter 6, the signal light is reflected back by Faraday reflector 7, and after passing through filter 6 and pump reflector 5 again, it enters the gain fiber 4 again, is amplified again by the gain fiber 4, and is output after passing through wavelength division multiplexer 3 and circulator 1.

[0039] Example

[0040] The input uses a 1540.56nm signal light, and the pump LD source uses a 980nm pump semiconductor laser. The 1540.56nm signal light is combined with the 980nm pump light through a circulator and then through a wavelength division multiplexer into the same optical fiber. The gain fiber is erbium fiber. Er3+ absorbs photons with a wavelength of 980nm, transitioning from the ground state to an excited state and then to a metastable state through non-radiative transition. Under the continuous action of the 980nm pump light, a large number of particles accumulate in the metastable state, resulting in population inversion. When the 1540.56nm signal light is incident, the particles in the metastable state undergo stimulated emission to transition back to the ground state, producing photons with the same frequency, phase, and direction as the signal light, thus amplifying the incident signal light. The 980nm pump light that is not completely absorbed in the gain erbium fiber is reflected back into the gain erbium fiber by the pump reflector and reabsorbed by Er3+, thus greatly improving the utilization rate of the pump light. The amplified 1540.56nm signal light, after passing through a filter to remove clutter, leaves only the signal wavelength we need. It is reflected back by a Faraday reflector, then passes through another filter and a pump reflector before entering the gain fiber again. After being amplified again by the gain fiber, it passes through a wavelength division multiplexer and is finally output from the output port of the circulator.

[0041] In summary, this application achieves two-way amplification of the signal light through circulator 1 and Faraday reflector 7, while filter 6 only allows laser light of the signal wavelength to pass through, filtering out amplified spontaneous emission light in gain fiber 4, thereby improving the signal-to-noise ratio and small-signal gain of the signal light; pump reflector 5 returns the remaining pump light to the gain fiber, which can reduce the length of the gain fiber; the use of circulator, Faraday reflector, pump reflector and filter can improve small-signal gain.

[0042] It should be noted that 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 high-gain fiber amplifier, characterized in that: The system includes a circulator, a laser, a wavelength division multiplexer, a gain fiber, a pump reflector, and a filter reflector arranged in sequence. The signal light is input through the circulator and coupled with the pump light input through the laser through the wavelength division multiplexer to the gain fiber, and then enters the pump reflector. In the pump reflector, the pump light is reflected back into the gain fiber. The signal light is reflected by the filter reflector and then passes through the pump reflector, the gain fiber, and the wavelength division multiplexer in sequence before being output from the circulator.

2. A high-gain fiber amplifier according to claim 1, characterized in that: The circulator is an optical fiber circulator.

3. A high-gain fiber amplifier according to claim 1, characterized in that: Lasers, wavelength division multiplexers, and gain fibers form either forward or backward pumping.

4. A high-gain fiber amplifier according to claim 1, characterized in that: A pump isolator is inserted at the rear end of the laser.

5. A high-gain fiber amplifier according to claim 1, characterized in that: The pump reflector is a fiber grating at the pump wavelength.

6. A high-gain fiber amplifier according to claim 1, characterized in that: The laser is a 980nm pumped semiconductor laser.

7. A high-gain fiber amplifier according to claim 1, characterized in that: The gain fiber is erbium fiber.

8. A high-gain fiber amplifier according to claim 1, characterized in that: The filter reflector is a bandpass filter fiber optic mirror.

9. A high-gain fiber amplifier according to claim 1, characterized in that: The filter reflector consists of a filter and a Faraday reflector arranged in sequence.

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