An L-band extended hybrid fiber amplifier

Abstract

The present invention discloses an L-band extended hybrid fiber amplifier, which belongs to the technical field of broadband fiber amplifiers. The system includes a first amplifying module and a second amplifying module; the first amplifying module is used to amplify the signal power of a conventional signal band; the second amplifying module is provided with an erbium-doped fiber, which is used to eliminate the backward ASE generated by the first amplifying module and amplify the signal power of an extended wavelength band. The present invention connects a section of highly-absorbent thulium-doped fiber to the front end of the first amplifying module including an erbium-doped fiber and a wavelength division multiplexer, and utilizes its absorption and emission characteristics in the C+L band to eliminate the backward 1.5μmASE generated in the system, thereby improving the L-band extended band amplification performance. The system of the present invention has a simple structure, high cost-effectiveness, and high efficiency, and at the same time meets the urgent demand for communication capacity of the current optical fiber communication system.

Description

Technical Field

[0001] The present invention belongs to the technical field of broadband optical fiber amplifiers, and more specifically, relates to an L-band extended hybrid optical fiber amplifier. Background Art

[0002] With the rapid development of data transmission services, the demand for communication capacity in long-distance optical fiber transmission systems has increased sharply, and how to expand the potential bandwidth of optical communications needs to be solved urgently. Wavelength division multiplexing technology (WDM) uses a single optical fiber to transmit multiple signals. In the early 1990s, it was combined with erbium-doped fiber amplifier (EDFA) technology to increase the bandwidth of the transmission system. Since then, the capacity of optical transmission systems has shown explosive growth, opening a new era of optical fiber communications. With the increase in the capacity demand of WDM systems, the gain bandwidth of traditional C-band EDFA can no longer meet the requirements. Expanding the working bandwidth of EDFA from C-band (1524-1572nm) to L-band (1575-1625nm), or even L-band extended band (1625-1635nm) has become the best solution to expand communication capacity at this stage.

[0003] However, EDFAs extended to the L-band still face many challenges. The power conversion efficiency (PCE) of L-band EDFAs is usually lower than that of C-band EDFAs because L-band EDFAs operate at the tail of the erbium gain band, and the tail emission cross section is much smaller than that near the 1530 nm peak. On the other hand, in the traditional structure of EDFA, the gain spectrum is usually shifted to the L-band by increasing the length of erbium-doped fiber. As a result, harmful backward ASE in the system accumulates in large quantities and reaches its maximum power at the input end of the amplifier, which not only wastes excessive pump power and affects the amplifier efficiency, but also consumes the particle inversion degree of erbium ions and deteriorates the system noise. At present, the main approach to this problem is to introduce fiber Bragg gratings or fiber reflectors to inject backward ASE back into the system. At this time, backward ASE acts as an auxiliary pump source in the system for reuse; however, this solution adjusts the effective pump power and increases the length of fiber used, which causes the system performance to deteriorate sharply. In addition, the injected backward ASE may compete with the original signal and degrade the system performance. The introduction of devices such as fiber Bragg gratings and fiber reflectors will also introduce additional device losses, which deteriorates the noise. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides an L-band extended hybrid fiber amplifier, which aims to utilize the backward ASE accumulated in the erbium-doped fiber amplifier, combined with the spectral characteristics of the thulium-doped fiber, to improve the efficiency of the L-band EDFA and achieve the purpose of L-band extended amplification.

[0005] To achieve the above object, the present invention provides an L-band extended hybrid optical fiber amplifier, comprising: a broadband light source, a filtering module, a first amplification module and a second amplification module;

[0006] The broadband light source is used to generate L-band signal light;

[0007] The first port of the filter module is connected to a broadband light source, the second port is connected to the first amplification module, and the third port is connected to the second amplification module, and is used to filter out the backward ASE reflected by the first amplification module and then couple it into the second amplification module;

[0008] The first amplification module is used to amplify the signal power of the conventional signal band;

[0009] The second amplification module is provided with thulium-doped optical fiber, which is used to eliminate the backward ASE generated by the first amplification module and amplify the L-band extended band signal light.

[0010] Further, the first amplification module includes an erbium-doped optical fiber, a wavelength division multiplexer, a first pump transmission optical fiber and a semiconductor laser;

[0011] The semiconductor laser is used to generate laser light;

[0012] The first pump transmission optical fiber is used to couple the pump light into the wavelength division multiplexer;

[0013] The wavelength division multiplexer is used to couple the signal light and the pump light into the erbium-doped optical fiber;

[0014] The erbium-doped optical fiber is used to act as a gain medium to absorb pump light and amplify L-band signal light.

[0015] Further, the second amplification module includes a thulium-doped optical fiber, a wavelength division multiplexer, and a second pump transmission optical fiber;

[0016] One end of the second pump transmission optical fiber is connected to the third port of the filter module, and the other end is connected to one end of the wavelength division multiplexer; the other end of the wavelength division multiplexer is connected to the thulium-doped optical fiber;

[0017] The second pump transmission optical fiber is a single-mode fiber supporting the passage of C-band light, and is used to transmit the backward ASE reflected by the first amplification module into the wavelength division multiplexer, and serves as a pump source for the second amplification module;

[0018] The wavelength division multiplexer is used to couple the pump light and the signal light into the thulium-doped optical fiber;

[0019] The thulium-doped optical fiber is used to absorb backward ASE and amplify the signal light in the L-band extension band.

[0020] Furthermore, the filtering module reflects and transmits the C band and the L band respectively; a gain flattening filter, or a fiber circulator, or a fiber Bragg grating type filtering component is used.

[0021] Furthermore, the laser wavelengths generated by the semiconductor laser include 980nm, 1480nm and 1530nm.

[0022] Furthermore, the first pump transmission optical fiber and the wavelength division multiplexer are matched with the selection of the pump light wavelength.

[0023] Furthermore, the system also includes a coupler for coupling the amplified normal-band signal light and the amplified L-band extended-band signal light into the system back end.

[0024] Furthermore, the system also includes an isolator, which is arranged at the front end of the receiving device and is used to isolate the light reflected back from the receiving port to protect the system from being affected.

[0025] In general, compared with the prior art, the above technical solution conceived by the present invention can achieve the following beneficial effects.

[0026] At present, thulium-doped fiber lasers can achieve ultra-wideband amplification of wavelengths of 1600-2050nm through different optical path designs. The present invention is based on the absorption characteristics of thulium ions in the C-band. By introducing thulium-doped fiber into the system, harmful backward ASE in the system is absorbed and used as the pump source of the thulium-doped fiber to improve the performance of the L-band extension band of the amplifier. This solution does not require the introduction of additional specific wavelength pump sources, thereby improving the efficiency and integration of the amplifier; it also makes up for the defect that the working wavelength of traditional L-band EDFA is difficult to further expand due to the limitation of erbium ion characteristics; at the same time, by absorbing and utilizing backward ASE, the degree of ASE accumulation in the system is reduced, thereby avoiding the problem of system performance degradation caused by it.

[0027] In general, the present invention improves the problem of low efficiency of conventional L-band erbium-doped fiber amplifiers, while further achieving L-band bandwidth expansion to alleviate transmission pressure, which meets the urgent demand for communication capacity of current optical fiber communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of the L-band extended hybrid optical fiber amplifier provided by the present invention;

[0029] Among them, 1 represents a broadband light source, 2 represents a filter module, 3 represents an erbium-doped fiber, (4, 8) represents a wavelength division multiplexer, 5 represents a first pump transmission fiber, 6 represents a semiconductor laser, 7 represents a thulium-doped fiber, 9 represents a second pump transmission fiber, 10 represents a coupler, and 11 represents an isolator. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] The present invention connects a filtering module in front of a first amplifier module including an erbium-doped fiber and a wavelength division multiplexer, and introduces the backward 1.5μm ASE generated by the erbium-doped fiber in the first amplifier module into a section of thulium-doped fiber. At this time, the harmful backward 1.5μm ASE in the system acts as a pump source for the thulium-doped fiber to excite the thulium-doped fiber to amplify the 1.6μm signal light. This solution effectively reduces the harmful backward ASE intensity in a conventional L-band erbium-doped fiber amplifier system, and is conducive to improving the performance of the amplifier in the L extended band.

[0032] Figure 1 This is a schematic diagram of the structure of the L-band extended hybrid optical fiber amplifier provided by the present invention:

[0033] The broadband light source 1 uses an ultra-wideband spectrum laser with a signal wavelength range of 1575-1635nm to generate signal light in a specific band. The output end of the broadband light source 1 is divided into two, connected to the first amplification module and the second amplification module respectively. The first amplification module is a link including erbium-doped optical fiber 3, and the second amplification module is a link including thulium-doped optical fiber 7.

[0034] like Figure 1 As shown, the first port a of the filter module 2 is connected to the broadband light source 1 that generates L-band signal light, the second port b of the filter module is connected to the first amplification module, and the third port c of the filter module is connected to the second amplification module; the filter module 2 reflects and transmits the C-band and L-band light respectively, so as to filter out the backward ASE of the first amplification module and couple it into the second amplification module. The filter module includes but is not limited to a gain flattening filter, or a fiber circulator, or a fiber Bragg grating filter assembly

[0035] like Figure 1 As shown, the first amplification module includes an erbium-doped fiber 3, a wavelength division multiplexer 4, a first pump transmission fiber 5 and a semiconductor laser 6; the semiconductor laser 6 generates laser light, and couples the pump light to the wavelength division multiplexer 4 through the first pump transmission fiber 5; the wavelength division multiplexer further couples the signal light and the pump light into the erbium-doped fiber 3; the erbium-doped fiber 3 is either an erbium-doped fiber or an erbium-ytterbium co-doped fiber; it is used to act as a gain medium to absorb the pump light and amplify the L-band signal light.

[0036] Specifically, the laser wavelengths generated by the semiconductor laser 6 include 980nm, 1480nm and 1530nm; and the corresponding first pump transmission optical fiber 5 and wavelength division multiplexer 4 are matched with the selection of the pump light wavelength; the adopted pumping scheme is either core pumping or cladding pumping.

[0037] like Figure 1 As shown, the backward ASE generated by the erbium-doped optical fiber 3 in the first amplifier module is transmitted backward from the output end and transmitted to the filter module 2 via the wavelength division multiplexer 4; at this time, the filter module exhibits reflective characteristics for the C-band light where the ASE is located, and enters the second amplifier module through the port 3 of the filter module 2.

[0038] like Figure 1 As shown, the second amplification module includes a thulium-doped fiber 7, a wavelength division multiplexer 8, and a second pump transmission fiber 9; the backward ASE generated by the first amplification module couples the pump light into the wavelength division multiplexer 8 through the second pump transmission fiber 9; at this time, the backward ASE acts as the injected pump light of the second amplification module, and is coupled together with the signal light into the thulium-doped fiber 7.

[0039] By adjusting the glass mechanism, thulium-doped fiber can show absorption characteristics for backward ASE and at the same time have a strong emission spectrum in the 1600-1700nm band. Using this characteristic, thulium-doped fiber can amplify signal light in the L-band extension band (1610-1635nm), making up for the defect of erbium-doped fiber in this band that the emission value is drastically attenuated due to being far away from the erbium ion emission peak band.

[0040] Furthermore, the thulium-doped fiber absorbs the backward ASE in the first amplifier module, avoiding its accumulation at the input end of the wavelength division multiplexer and competing with the signal light to consume the inversion degree and pump light, so as to improve the gain performance and pump conversion efficiency of the first amplifier module. At the same time, the consumption of backward ASE is also beneficial to the optimization of the noise performance of the first amplifier module. On the other hand, the backward ASE can serve as the pump source of the second amplifier module, and the L-band extended amplification performance can be achieved without introducing additional pumping structures.

[0041] Furthermore, the system also includes a coupler 10 connected to the front end of the first amplifying module and the second amplifying module, which is used to couple the amplified conventional band signal light and the amplified extended band signal light into the back end of the system; and an isolator 11 arranged at the front end of the receiving device, which is used to isolate the light reflected back from the receiving port to protect the system from being affected.

[0042] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An L-band extended hybrid fiber amplifier, characterized in that: include: A broadband light source (1), a filtering module (2), a first amplifying module and a second amplifying module; The broadband light source (1) is used to generate L-band signal light; The first port of the filter module (2) is connected to a broadband light source, the second port is connected to the first amplification module, and the third port is connected to the second amplification module, and is used to filter out the backward ASE reflected by the first amplification module and couple it into the second amplification module; The first amplification module is used to amplify the power of the conventional L-band signal; The second amplification module is provided with a thulium-doped optical fiber for eliminating the backward ASE generated by the first amplification module and amplifying the L-band extended band signal light; The second amplification module comprises a thulium-doped optical fiber (7), a wavelength division multiplexer (8), and a second pump transmission optical fiber (9); One end of the second pump transmission optical fiber (9) is connected to the third port of the filter module (2), and the other end is connected to one end of the wavelength division multiplexer (8); the other end of the wavelength division multiplexer (8) is connected to the thulium-doped optical fiber (7); The second pump transmission optical fiber (9) is a single-mode fiber that supports the passage of C-band light, and is used to transmit the backward ASE reflected by the first amplification module into the wavelength division multiplexer (8) to serve as a pump source for the second amplification module; The wavelength division multiplexer (8) is used to couple the pump light and the signal light together into the thulium-doped optical fiber (7); The thulium-doped optical fiber (7) is used to absorb backward ASE and amplify signal light in the L-band extension band.

2. The L-band extended hybrid fiber amplifier according to claim 1, characterized in that: The first amplification module comprises an erbium-doped optical fiber (3), a wavelength division multiplexer (4), a first pump transmission optical fiber (5) and a semiconductor laser (6); The semiconductor laser (6) is used to generate laser light; The first pump transmission optical fiber (5) is used to couple the pump light into the wavelength division multiplexer (4); The wavelength division multiplexer (4) is used to couple the signal light and the pump light into the erbium-doped optical fiber (3); The erbium-doped optical fiber (3) is used to act as a gain medium to absorb pump light and amplify L-band signal light.

3. The L-band extended hybrid fiber amplifier according to claim 2, characterized in that: The filtering module reflects and transmits the C band and the L band respectively; a gain flattening filter, or an optical fiber circulator, or an optical fiber Bragg grating type filtering component is adopted.

4. The L-band extended hybrid fiber amplifier according to claim 2, characterized in that: The laser wavelengths generated by the semiconductor laser (6) include 980nm, 1480nm and 1530nm.

5. The L-band extended hybrid fiber amplifier according to claim 4, characterized in that: The first pump transmission optical fiber (5) and the wavelength division multiplexer (4) are matched with the selection of the wavelength of the pump light.

6. The L-band extended hybrid fiber amplifier according to any one of claims 1 to 5, characterized in that: The system also includes a coupler (10) for coupling the amplified conventional L-band signal light and the amplified L-band extended-band signal light into the system back end.

7. The L-band extended hybrid fiber amplifier according to claim 6, characterized in that: The system also includes an isolator (11), which is arranged at the front end of the receiving device and is used to isolate the light reflected back from the receiving port to protect the system from being affected.

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