A single-pumped dual-polarization erbium-doped fiber amplifier

Abstract

The utility model relates to optical communication network equipment technical field more specifically, relate to a kind of single-pumped bipolar erbium-doped fiber amplifier.A kind of single-pumped bipolar erbium-doped fiber amplifier, comprising: signal light source, optical isolator, coupler, pump laser, first-stage erbium-doped fiber and second-stage erbium-doped fiber;The output end of signal light source is connected with the first input end of coupler, and the output end of pump laser is connected with the second input end of coupler;The coupler, first-stage erbium-doped fiber, optical isolator and second-stage erbium-doped fiber are sequentially connected.

Description

Technical Field

[0001] This utility model relates to the field of optical communication network equipment technology, and more specifically, to a single-pumped bipolar erbium-doped fiber amplifier. Background Technology

[0002] In fiber optic communication systems, optical signals attenuate during transmission, requiring compensation using optical amplifiers. Currently, all-optical amplification technology directly compensates for attenuated optical signals in the fiber using optical amplifiers, replacing the photoelectric-optical conversion mode of traditional photoelectric regeneration repeaters. It features small size, low cost, simple structure, and excellent performance, and is therefore widely used in various fiber optic communication systems. With technological advancements, all-optical amplification technology supports dense wavelength division multiplexing (DWDM) systems, enabling high-capacity data transmission. There are many types of optical amplifiers, among which semiconductor optical amplifiers (SOAs), erbium-doped fiber amplifiers (EDFAs), and Raman fiber amplifiers (RFAs) are the most representative.

[0003] Semiconductor optical amplifiers (SOAs) were the earliest type of optical amplifiers. Their structure is similar to that of semiconductor lasers. The amplification mechanism involves injecting current into a semiconductor PN junction to create population inversion. When signal light is incident, stimulated emission occurs, amplifying the signal light. SOAs have advantages such as miniaturization, ease of integration, and mature manufacturing processes, but they also have disadvantages such as difficulty in coupling with optical fibers, high noise figure, and strong nonlinearity.

[0004] The origins of EDFA can be traced back to the first development of erbium-doped fiber amplifiers at the University of Southampton in the UK in 1985. In 1990, Beryl introduced the first commercial EDFA, which subsequently moved from laboratory applications to commercial use, greatly promoting the advancement of optical fiber communication. It primarily utilizes the stimulated emission principle of rare-earth elements in doped optical fibers to amplify optical signals. Its applications are diverse, with varying performance requirements across different scenarios. EDFA advantages include low coupling loss with optical fibers, high energy conversion efficiency, high gain, low noise figure, high output power, and low cross-gain. However, it also has disadvantages such as a fixed gain spectrum range, narrow and uneven gain bandwidth, thermal effects at high power output, and optical nonlinearity, which can negatively impact performance. Today, EDFA is evolving towards L-band extensions and integrated waveguide amplifiers, such as chip-level amplifiers based on erbium-doped lithium niobate thin films, breaking through the bottleneck of traditional optical transmission gain and laying the foundation for the intelligence and efficiency of future optical networks.

[0005] Raman fiber amplifiers operate based on the stimulated Raman scattering (SRS) effect. When a low-frequency signal light and a high-frequency pump light are simultaneously input into a segment of optical fiber, and the frequency difference is within the Raman gain bandwidth of the pump light, the signal light can be amplified. Raman amplifiers offer significant advantages: the gain spectrum range is determined by the pump light wavelength, allowing for the amplification of any optical signal band by selecting an appropriate wavelength; they require no special gain medium, resulting in a simple structure and low cost; they have a wide bandwidth, and multiple pumping methods can increase gain and improve flatness; they support distributed amplification and suppress nonlinear effects. However, their disadvantages include low pump efficiency, the need for high-power pump light, performance susceptible to the quality of the transmission fiber, and relatively low and uneven gain.

[0006] Optical isolators are passive optical devices with non-reciprocal characteristics. Inserted into the ends or middle of an optical fiber amplifier, they suppress reflected light, reduce noise and signal fluctuations, and improve stability. High isolation (generally exceeding 30 dB) and low insertion loss are typically required to effectively block spontaneous emission noise from the preceding and following amplification stages. Erbium-doped fiber (EDFA) is fiber doped with an appropriate amount of trivalent erbium ions. Under pump light, it can amplify signals in the 1550 nm range. As the core component of an EDFA, its length, core diameter, numerical aperture, and erbium ion concentration significantly affect its performance. The core of an EDFA lies in erbium-doped fiber (EDF). By doping erbium ions into the core of a single-mode silica fiber, gain amplification of signals near 1550 nm is achieved under pump light. It is typically equipped with a wavelength division multiplexer (WDM) to couple the signal and pump light, a pump laser to provide energy, and a gain flattening filter (GFF) to flatten the spectrum and ensure uniform output across the entire wavelength range. Amidst the rapid development of the industry, many manufacturers have introduced hybrid integrated devices, combining functional components such as optical isolators and WDM to achieve miniaturization, multifunctionality, and low cost, thereby enhancing the potential of EDFA in long-distance trunk communication. These advancements have reduced the noise figure, improved pump efficiency and system stability, making EDFA a core device in modern fiber optic communication.

[0007] However, existing erbium-doped fiber amplifiers have the following drawbacks:

[0008] 1. Due to its long length, the input end generates significant reverse amplified spontaneous radiation, which consumes pump power and increases the noise figure.

[0009] 2. Increasing the pump power can improve the gain, but it reduces the pump efficiency and laser reliability.

[0010] 3. Ordinary single-stage structures cannot simultaneously satisfy high signal gain, low noise figure, and high output power.

[0011] 4. While adopting a two-stage direct-connect structure can improve gain and output power, it increases cost and complexity and reduces stability.

[0012] To address the aforementioned issues, an erbium-doped fiber amplifier is needed that can effectively suppress reverse amplified spontaneous emission, reduce costs, and improve performance. Utility Model Content

[0013] This invention provides a single-pumped bipolar erbium-doped fiber amplifier to overcome the shortcomings of existing erbium-doped fiber amplifiers, which are characterized by long lengths leading to significant backward amplified spontaneous emission, high pump power consumption, and increased noise figure. This invention achieves effective suppression of backward ASE by inserting an optical isolator into the erbium-doped fiber to form a bipolar structure and optimizing the positional allocation ratio. Simultaneously, it uses only a single-pump laser, simplifying system design and improving overall efficiency and reliability.

[0014] This invention provides a single-pumped bipolar erbium-doped fiber amplifier, comprising: a signal source, an optical isolator, a coupler, a pump laser, a first-stage erbium-doped fiber, and a second-stage erbium-doped fiber;

[0015] The output terminal of the signal light source is connected to the first input terminal of the coupler, and the output terminal of the pump laser is connected to the second input terminal of the coupler.

[0016] The coupler, the first-stage erbium-doped fiber, the optical isolator, and the second-stage erbium-doped fiber are connected in sequence.

[0017] Optionally, the length ratio of the first-stage erbium-doped fiber to the second-stage erbium-doped fiber is 1:2.

[0018] Optionally, the length of the first-stage erbium-doped fiber is 2 meters, and the length of the second-stage erbium-doped fiber is 4 meters.

[0019] Optionally, the pump laser is configured to face forward.

[0020] Optionally, the optical signal output by the signal light source propagates in one direction.

[0021] Optionally, the wavelength of the signal light source is 1535 nm.

[0022] Optionally, the Er in the first-stage erbium-doped fiber and the second-stage erbium-doped fiber... 3+ The ion concentration is 1×10 25 m -3 Numerical aperture 0.24, doping radius 2.2 μm.

[0023] Optionally, the coupler signal operates at a wavelength of 1550 nm and has a bandwidth of 130 nm.

[0024] Optionally, the pump laser operates at a wavelength of 980 nm and a power of 80 mW.

[0025] Optionally, the optical isolator has an isolation of 60 dB, an insertion loss of 0.5 dB, and a return loss of 60 dB.

[0026] Compared with the prior art, the beneficial effects of this utility model's technical solution are:

[0027] This invention provides a single-pumped bipolar erbium-doped fiber amplifier, comprising: a signal source, an optical isolator, a coupler, a pump laser, a first-stage erbium-doped fiber, and a second-stage erbium-doped fiber. The output end of the signal source is connected to the first input end of the coupler, and the output end of the pump laser is connected to the second input end of the coupler. The coupler, the first-stage erbium-doped fiber, the optical isolator, and the second-stage erbium-doped fiber are connected sequentially. This invention employs a single-pumped bipolar structure, reducing the number of pump lasers used and lowering system cost and complexity. Simultaneously, the optical isolator effectively suppresses reverse ASE (associated aliasing), improving the overall amplifier performance. Finally, the erbium-doped fiber used in this invention is shorter, lower in cost, and exhibits less loss and higher transmission efficiency during fiber transmission. Compared to traditional single-stage or multi-pump structures, this invention achieves superior performance with a signal gain of up to 45.81 dB, a noise figure as low as 3.28 dB, and an output power of 5.80 dBm under small signal input conditions. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A schematic diagram of the structure of a single-pumped bipolar erbium-doped fiber amplifier according to an embodiment of the present invention is shown.

[0030] Illustration: 101 - Signal source; 102 - Pump laser; 103 - Coupler; 104 - First-stage erbium-doped fiber; 105 - Optical isolator; 106 - Second-stage erbium-doped fiber. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0033] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0034] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product is habitually placed in during use. They are used only for the convenience of describing this utility model and for simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0035] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," not that the structure must be completely horizontal, but can be slightly tilted.

[0036] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," "couple," and "couple" 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.

[0037] Example 1

[0038] like Figure 1As shown, the single-pumped bipolar erbium-doped fiber amplifier 100 includes a signal light source 101 at the input end for providing input signal light. This can be, for example, signal light from an external optical communication device or a signal from an analog test. The input optical signal may include a communication signal of a specific wavelength. In at least some other embodiments, the signal light source 101 has a standard interface for easy connection to optical fibers or other optical devices.

[0039] The signal light source 101 routes the input signal light to the coupler 103. In this embodiment, the output light signal wavelength of the signal light source 101 is set to 1535 nm, and the power can be adjusted according to the application scenario, for example, -40 dBm for small signal input or 0 dBm for large signal input.

[0040] Pump laser 102 serves as a pump source, providing pump light. In this embodiment, the center wavelength of pump laser 102 is set to 980 nm, and the pump power is set to 80 mW. Pump laser 102 injects pump light into coupler 103.

[0041] Furthermore, the pump laser 102 is configured for forward pumping, meaning the signal light and pump light propagate in the same direction. Compared to reverse pumping or bidirectional pumping, forward pumping allows the amplifier system 100 to achieve a lower noise figure. The noise figure, as an amplifier performance indicator, measures the degree of signal-to-noise ratio degradation and reflects the overall performance of the system.

[0042] It should be noted that in erbium-doped fiber amplifier systems, most components are passive devices, resulting in high reliability. The pump laser, however, is an active device, requiring adjustment of the pump power based on the input-output power ratio to maintain stable output gain. A lower noise figure reduces the need for adjustment frequency and amplitude, improving the stability and lifespan of the pump laser, thereby enhancing the overall reliability of the amplifier system and making it suitable for long-distance optical communication trunk lines.

[0043] Coupler 103 (WDM Coupler) multiplexes the signal light from signal source 101 and the pump light from pump laser 102, and injects the multiplexed optical signal output into the first-stage erbium-doped fiber 104 for preliminary amplification. In this embodiment, the signal operating wavelength of coupler 103 is 1550 nm, the pump operating wavelength is 980 nm, and the operating bandwidth is 130 nm.

[0044] The first-stage erbium-doped fiber 104 (EDF1) receives the output optical signal from coupler 103, including a 1535 nm signal light and a 980 nm pump light. The first-stage erbium-doped fiber 104 absorbs the energy of the pump light and amplifies the signal light through stimulated emission of erbium ions (Er³⁺). In this embodiment, the length of the first-stage erbium-doped fiber 104 is set to 2 m, and the Er³⁺ ion concentration is 1 × 10².5 m⁻³, numerical aperture of 0.24, and doping radius of 2.2 μm.

[0045] Optical isolator 105 (ISO) receives the initially amplified optical signal from the first-stage erbium-doped fiber 104. ISO 105 routes the signal light through and suppresses amplified spontaneous emission (ASE) in the reverse direction, preventing it from entering upstream components. In this embodiment, the isolation of ISO 105 is 60 dB, the insertion loss is 0.5 dB, and the return loss is 60 dB. This configuration reduces pump power consumption on the reverse ASE, improves overall gain, and lowers the noise figure.

[0046] The second-stage erbium-doped fiber 106 (EDF2) receives the output optical signal from the optical isolator 105 and further absorbs the energy of the remaining pump light for secondary amplification of the signal light. In this embodiment, the length of the second-stage erbium-doped fiber 106 is set to 4m, with a length ratio of 1:2 to that of the first-stage erbium-doped fiber 104. This allocation ratio is based on optimal positioning of the optical isolator, achieving maximum signal gain, lowest noise figure, and higher output power.

[0047] It should be noted that this single-pump bipolar structure uses only one pump laser, reducing the number of active devices compared to multi-pump systems and improving system reliability. In the event of a partial system failure, the remaining components can still provide basic amplification, preventing complete communication interruption and providing time for maintenance. The single-pump bipolar erbium-doped fiber amplifier is simple to assemble, easy to operate, and has a low cost. It can reduce the failure rate of the pump laser during long-term operation, and its low noise figure makes it suitable for use in high-stability optical communication transmission systems.

[0048] In this embodiment, the output of the single-pumped bipolar erbium-doped fiber amplifier can be connected to an external device to provide amplified signal light. This system is simple to assemble, low in cost, and suitable for line amplifier, power amplifier, or preamplifier applications, enabling its use in high-reliability optical communication systems. In line amplifier applications, this system can compensate for signal attenuation in the fiber optic link, ensuring transmission quality; in power amplifier mode, it can enhance the transmitter output strength and reduce transmission loss; in preamplifier scenarios, it can optimize signal processing before the receiver, improving system sensitivity.

[0049] The same or similar labels correspond to the same or similar parts;

[0050] The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0051] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating this utility model, and are not intended to limit the implementation of this utility model. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A single-pumped bipolar erbium-doped fiber amplifier, characterized in that, include: Signal source, optical isolator, coupler, pump laser, first-stage erbium-doped fiber and second-stage erbium-doped fiber; The output terminal of the signal light source is connected to the first input terminal of the coupler, and the output terminal of the pump laser is connected to the second input terminal of the coupler. The coupler, the first-stage erbium-doped fiber, the optical isolator, and the second-stage erbium-doped fiber are connected in sequence.

2. The single-pumped bipolar erbium-doped fiber amplifier according to claim 1, characterized in that, The length ratio of the first-stage erbium-doped fiber to the second-stage erbium-doped fiber is 1:

2.

3. The single-pumped bipolar erbium-doped fiber amplifier according to claim 2, characterized in that, The first-stage erbium-doped fiber is 2 meters long, and the second-stage erbium-doped fiber is 4 meters long.

4. The single-pumped bipolar erbium-doped fiber amplifier according to claim 1, characterized in that, The pump laser is configured to face forward.

5. A single-pumped bipolar erbium-doped fiber amplifier according to claim 1, characterized in that, The light signal output by the signal source propagates in one direction.

6. A single-pumped bipolar erbium-doped fiber amplifier according to claim 5, characterized in that, The wavelength of the optical signal is 1535nm.

7. A single-pumped bipolar erbium-doped fiber amplifier according to claim 1, characterized in that, Er in the first-stage erbium-doped fiber and the second-stage erbium-doped fiber 3+ The ion concentration is 1×10 25 m -3 Numerical aperture 0.24, doping radius 2.2 μm.

8. A single-pumped bipolar erbium-doped fiber amplifier according to claim 1, characterized in that, The coupler operates at a wavelength of 1550nm and has a bandwidth of 130nm.

9. A single-pumped bipolar erbium-doped fiber amplifier according to claim 1, characterized in that, The pump laser operates at a wavelength of 980nm and has a power of 80mW.

10. A single-pumped bipolar erbium-doped fiber amplifier according to claim 1, characterized in that, The optical isolator has an isolation of 60 dB, an insertion loss of 0.5 dB, and a return loss of 60 dB.

Images