Patent Application
20210234325
The present disclosure relates to the fields of optical communication technology, and in particular relates to an opposing pump structure for twin 980-nm pump lasers in EDFA.
In an optical fiber communication system, an Erbium Doped Fiber Amplifier (EDFA) is an important relay device that extends the transmission distance of optical signals. Unlike optical-electric-optical relay amplification, the EDFA is a kind of light-to-light repeater. Since its first appearance in the late 1980s, the EDFA has been playing a pivotal role in the global optical communication system, and has been booming and widely used. A pump laser is an energy source for the EDFA to amplify the signal light. Pump light is injected into an erbium-doped fiber to excite erbium ions from a ground state to an upper energy level, and then to a metastable state without radiation. When signal light is injected into the doped fiber, in a case of erbium ions falling from the metastable state to the basic level, energy could be released and amplified light having the same direction, frequency, and phase as the incident signal light could be generated, that is, an optical amplification process is completed.
At present, there are mainly two types of pump lasers: 980-nm pump laser and 1480-nm pump laser. The 980-nm pump laser may have relatively strong noise suppression capability, while the 1480-nm pump laser may have relatively high energy conversion efficiency. Both the 980 and 1480-nm pump lasers are F-P lasers. The F-P laser is a multi-longitudinal mode laser with a broad spectrum, for example, a 20 dB spectral width of the 1480-nm pump laser can reach 10 nm or even 20 nm. Emission and absorption spectra of Erbium ion is relatively steep in a 980-nm band, but relatively flat in a 1480-nm band. Correspondingly, an Erbium Doped Fiber (EDF) put higher requirements on the spectrum of the 980-nm pump laser. Therefore, it is necessary to write a fiber Bragg grating (FBG) on a pigtail of the 980-nm pump laser as an external cavity to further process the spectrum, so it is difficult to integrate an isolator on the package of the 980-nm pump laser; on the contrary, there is no need to add the FBG to a pigtail of the 1480-nm pump laser as an external cavity for further processing the spectrum, thus the 1480-nm pump laser may output in only the original spectrum. Correspondingly, since there is no FBG external cavity on the pigtail of the 1480-nm pump laser, an isolator can be integrated on a tail tube of the 1480-nm pump laser.
In terms of the optical path structure, a forward pump has a strong ability to suppress noise, and a backward pump has a high amplification gain. In an engineering design and application, it is often necessary to combine the forward pump and the backward pump together, so that the advantages of the forward pump and the backward pump can be combined to increase an output optical power while suppressing the noise. In an opposing pump structure, however, if residual pump light with the same or similar wavelength is injected into an opposing pump, it may cause lasing in the opposing pump and cause the failure of the opposing pump laser. That is, there is a risk of mutual interference between the two opposing pumps. In the above-mentioned 980-nm pump laser, the FBG on the pigtail of 980-nm pump laser belongs to an external cavity which is used in a filtering mode, and only the optical power of the desired wavelength is emitted; while there is no blocking effect for external stray pump light with other wavelengths and the external stray pump light can still be injected into the cavity of the pump laser. If the wavelength of the stray pump light is close to the wavelength of output light of the interfered pump laser, then there is a certain probability that the pump laser is subject to lasing, whereby destroying an original resonance mode of the pump laser cavity, and further causing the failure of the disturbed pump laser.
Since the output position of the 1480-nm pump laser is generally integrated with an isolator, two 1480-nm pump lasers can be used as opposing pump lasers. Given that the central wavelengths of the 980-nm pump laser and the 1480-nm pump laser are far apart from each other, the 980-nm pump laser and the 1480-nm pump laser can be used as opposing pump lasers. Since the 980-nm pump laser cannot be integrated with an isolator, the opposing pump structure for twin 980-nm pump lasers cannot be used directly. Therefore, there are only opposing pump structure for twin 980-nm pump 980+1480-nm pump and 1480-nm pump+1480-nm pump in the current engineering design. In some engineering applications, a unidirectional 980-nm pump laser, a unidirectional 1480-nm pump laser, an opposing pump structure for 1480+1480-nm pump lasers or an opposing pump structure for 980+1480-nm pump lasers cannot meet the requirements, and only a 980+980 opposing pump structure is qualified. For example, the 980+980 opposing pump structure can well meet a good noise performance requirement for the opposing pump architecture. In another example, for some symmetrical array optical path EDFA, the 980+1480 opposing pump structure is not applicable for it cannot be symmetrical, and the 1480+1480 opposing pump structure is not applicable for it cannot achieve array symmetry due to its slow absorption. Only the 980+980 opposing pump structure is suitable for this case. In this situation, it is necessary to properly modify the optical path to prevent the two opposing 980-nm pump lasers from interfering each other.
In view of this, the above-mentioned defect in the prior arts is an urgent problem to be solved in this technical field.
The technical problem to be solved by the present disclosure is:
There is a risk of mutual interference between two 980-nm opposing pump lasers, since there currently is no 980-nm pump laser integrated with optical isolator on the market, and in the 980+980 opposing pump structure, if residual pump light with the same or similar wavelength is injected into the opposing pump lasers, it may cause lasing in the pump lasers and cause the opposing pump lasers to be failed.
The present disclosure provides following technical solutions to achieve the above objective.
The present disclosure provides an opposing pump structure for twin 980-nm pump lasers in EDFA, comprising an erbium-doped fiber, a first 980-nm pump laser, a second 980-nm pump laser, a signal/pump combiner, a second signal/pump combiner, and anti-interference structures;
the first 980-nm pump laser being used to output first pump light and being connected to the first signal/pump combiner, and the first signal/pump combiner being connected to a signal input end of the erbium-doped fiber, so that the first pump light is injected into the erbium-doped fiber in a forward direction; the second 980-nm pump laser being used to output second pump light and being connected to the second signal/pump combiner, and the second signal/pump combiner being connected to a signal output end of the erbium-doped fiber so that the second pump light is injected into the erbium-doped fiber in a reverse direction;
wherein anti-interference structures are respectively arranged on a forward optical transmission path of the first pump light and a reverse optical transmission path of the second pump light to respectively resist interference of the first pump light to the second 980-nm pump laser and interference of the second pump light on the first 980-nm pump laser.
Preferably, the anti-interference structure includes a first fiber Bragg grating and a second fiber Bragg grating, the first fiber Bragg grating being arranged on the transmission light path of the first pump light, and being used to pass through the first pump light and highly reflect the second pump light; and the second fiber Bragg grating being arranged on the transmission light path of the second pump light, and being used to pass through the second pump light and highly reflect the first pump light.
Preferably, a central wavelength and bandwidth of a high reflection band of the first fiber Bragg grating match the second pump light, and a central wavelength and bandwidth of a high reflection band of the second fiber Bragg grating match the first pump light.
Preferably, the first fiber Bragg grating is arranged between the first 980-nm pump laser and the first signal/pump combiner, or between the first signal/pump combiner and the signal input end of the erbium-doped fiber; and the second fiber Bragg grating is arranged between the second 980-nm pump laser and the second signal/pump combiner, or between the second signal/pump combiner and the signal output end of the erbium-doped fiber.
Preferably, the first fiber Bragg grating is written on a pigtail of the first 980-nm pump laser, or a pigtail of the first signal/pump combiner, or the signal input end of the erbium-doped fiber; and the second fiber Bragg grating is written on a pigtail of the second 980-nm pump laser, or a pigtail of the second signal/pump combiner, or the signal output end of the erbium-doped fiber.
Preferably, the anti-interference structure includes a first optical filter and a second optical filter, the first optical filter being arranged between the first 980-nm pump laser and the first signal/pump combiner, and the second optical filter being arranged between the second 980-nm pump laser and the second signal/pump combiner.
Preferably, the first optical filter and the second optical filter both may be a narrow-band band-pass filter; wherein the first optical filter allows the first pump light to pass through and shields the second pump light, and the second optical filter allows the second pump light to pass through and shields the first pump light.
Preferably, the central wavelengths of the first pump light and the second pump light are both selected in a range of 973-981.5 nm.
Preferably, the first pump light and the second pump light are different with each other in central wavelength, and a central wavelength difference thereof is 4-7 nm.
Preferably, the erbium-doped optical fiber is only a single section, or one cascaded from at least two sections.
The beneficial effects of the present invention are as follows.
In opposing pump structure for twin 980-nm pump lasers in EDFA provided by the present disclosure, an optical path of the 980+980 opposing pump structure is appropriately improved, and fiber Bragg gratings or optical filters are added as anti-interference structures, such that residual pump light in any direction cannot be injected into the opposing pump, thereby avoiding the mutual interference between the two 980 opposing pumps, and avoiding the failure of the pump laser. Moreover, compared with an integrated optical isolator, the solution adopting fiber Bragg grating and optical filter is of low loss, small size and low cost.
For a clear illustration of technical solutions of embodiments of the present disclosure, the drawings necessary for the embodiments of the present disclosure will be briefly introduced hereinafter. Obviously, the drawings described below are only some embodiments of the present disclosure. For those of ordinary skilled in the art, other drawings can be obtained based on these drawings without creative work.
Without considering the mutual interference between two 980-nm opposing pumps, an original twin 980-nm pump structure comprises, as shown in
Referring to
In the theoretical opposing pump structure shown in
In order to make the objectives, technical solutions and advantages of the present disclosure clearer, the present disclosure 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 disclosure, but not to limit the present disclosure.
In addition, the technical features involved in various embodiments of the present disclosure described below can be combined with each other as long as they do not conflict with each other. The present disclosure is described in detail below with reference to the accompanying drawings and embodiments.
In an embodiment of the present disclosure, there is provided an opposing pump structure for twin 980-nm pump lasers in EDFA, comprising an erbium-doped fiber 1, a first 980-nm pump laser 2-1, a second 980-nm pump laser 2-2, a first signal/pump combiner 3-1, a second signal/pump combiner 3-2, and an anti-interference structure. On the basis of
As shown in
In an opposing pump structure for twin 980-nm pump lasers used in EDFA provided in the present disclosure, optical paths of the 980+980 opposing pump structure are appropriately improved, and a fiber Bragg grating is respectively added to the optical transmission paths of two pump lights and each can highly reflect residual pump light in another direction, so that the residual pump light in another direction cannot be injected into the opposing pump, whereby avoiding the mutual interference between two 980-nm opposing pumps with each other and avoiding the failure of the opposing pump laser. Moreover, compared with the integrated optical isolator, the solution adopting optical fiber Bragg gratings has the advantages of small loss, small size and low cost.
Referring specifically to
In order to eliminate the mutual interference between the first 980-nm pump laser 2-1 and the second 980-nm pump laser 2-2, in the embodiments of the present disclosure, the first fiber Bragg grating 4-1 and the second fiber Bragg grating 4-2 may both be a high-reflectivity fiber Bragg grating, whose 30 dB bandwidth of the high reflection windows is 4-7 nm and reflectivity is above 99%. A central wavelength and bandwidth of a high reflection band of the first fiber Bragg grating 4-1 match a central wavelength and bandwidth of the second pump light so as to highly reflect the second pump light, and a central wavelength and bandwidth of the high reflection band of the second fiber Bragg grating 4-2 match a central wavelength and bandwidth of the first pump light so as to highly reflect the first pump light. Therefore, when the first pump light is transmitted in the forward direction, it can pass through the first fiber Bragg grating 4-1 with low loss and then continue to be transmitted, and after the second pump light passes through the second signal/pump combiner 3-2, the erbium-doped fiber 1, and the first signal/pump combiner 3-1, remaining second pump light reaches the first fiber Bragg grating 4-1 in the reverse direction, and can be reflected to the greatest extent, such that it is difficult for the second pump light to pass through the first fiber Bragg grating 4-1 to reach the first 980-nm pump laser 2-1, whereby eliminating the interference of the second 980-nm pump laser 2-2 to the first 980-nm pump laser 2-1. Similarly, when the second pump light is transmitted in the reverse direction, it can pass through the second fiber Bragg grating 4-2 with low loss and then continue to transmit, and when the first pump light is forward transmitted to the second fiber Bragg grating 4-2, it can be reflected to the greatest extent, such that it is difficult for the first pump light to pass through the second fiber Bragg grating 4-2 to reach the second 980-nm pump laser 2-2, whereby eliminating the interference of the first 980-nm pump laser 2-1 to the second 980-nm pump laser 2-2.
In the embodiments of the present disclosure, the central wavelengths of the first pump light and the second pump light both can be selected in a range of 973-981.5 nm. It should be noted that in the embodiments of the present disclosure, in order to prevent the first pump light from passing through the second fiber Bragg grating 4-2, or the second pump light from passing through the first fiber Bragg grating 4-1, the first pump light and the second pump light have different central wavelengths, and the central wavelength difference thereof is in a range of 4-7 nm. If the central wavelength difference is too small, it is difficult to separate the two pump lights; and when the central wavelength difference is greater than 4 nm, the two pump lights can be distinguished from each other without any difficulty. In the opposing pump structure for twin 980-nm pump lasers of this embodiment, the first 980-nm pump laser 2-1 and the second 980-nm pump laser 2-2 are select wavelengths in a mismatched manner, for example, 973 and 977 nm are selected respectively. The bandwidth of high reflection window of FBG can actually be determined by the difference in the central wavelength of the two opposing pump lasers. Assuming that the central wavelength difference of the two pumps is 4 nm, the bandwidth of the high reflection window can be set to 4 nm; if the central wavelength difference of the two pumps is 7 nm, the bandwidth of the high reflection window can be set to 4˜7 nm.
Referring to
On the basis of the embodiments of the present disclosure, the first fiber Bragg grating 4-1 can also be arranged on the first pump light path, and the second fiber Bragg grating 4-2 can also be arranged on the main optical path of the signal light path. Specifically, the first fiber Bragg grating 4-1 is arranged between the first 980-nm pump laser 2-1 and the first signal/pump combiner 3-1, and the second fiber Bragg grating 4-2 is arranged between the second signal/pump combiner 3-2 and the signal output end of the erbium-doped fiber 1. Alternatively, the first fiber Bragg grating 4-1 may be arranged on the main optical path of the signal light, and the second fiber Bragg grating 4-2 may be arranged on the second pumping optical path. Specifically, the first fiber Bragg grating 4-1 is arranged between the first signal/pump combiner 3-1 and the signal input end of the erbium-doped fiber 1, and the second fiber Bragg grating 4-2 is arranged between the second signal/pump combiner 3-2 and the signal output end of the erbium-doped optical fiber 1; in addition, the specific connection mode and working principle are not repeated here.
In comparison, when the first fiber Bragg grating 4-1 is arranged on the first pump light path, and the second fiber Bragg grating 4-2 is arranged on the second pump light path, the first fiber Bragg grating 4-1 and the second fiber Bragg grating 4-2 could not cause additional insertion loss to the signal light, so this arrangement is better.
In embodiments of the present invention, the first fiber Bragg grating 4-1 and the second fiber Bragg grating 4-2 can also be directly written on the pigtail of the device. Specifically, the first fiber Bragg grating 4-1 can be directly written on the pigtail of the first 980-nm pump laser 2-1, or on the pigtail of the first signal/pump combiner 3-1, or on the signal input end of the erbium-doped optical fiber 1, and the second fiber Bragg grating 4-2 can be directly written on the pigtail of the second 980-nm pump laser 2-2, or on the pigtail of the second signal/pump combiner 3-2, or on the signal output end of the erbium-doped fiber 1. Through this arrangement, in the entire optical path transmission, the first fiber Bragg grating 4-1 can still highly reflect the second pump light, and the second fiber Bragg grating 4-2 can still highly reflect the first pump light, whereby still being able to eliminate the mutual interference between the two 980-nm pump lasers.
With reference to
On the basis of the above embodiment 1, an embodiment of the present disclosure also provides another opposing pump structure for twin 980-nm pump lasers used in EDFA, as shown in
Referring to
In the embodiment of the present disclosure, the first optical filter 5-1 and the second optical filter 5-2 are both narrow-band band-pass filters, which may allow optical signals with specific wavelengths to pass through while shielding optical signals with other wavelengths. The bandwidth of their narrowband window 30 dB is 3-7 nm, and the transmission insertion loss of the filters is within 0.6 dB. The first optical filter 5-1 can only allow light with a first pump light wavelength to pass through and shield light with other wavelengths, and the second optical filter 5-2 can only allow light with a second pump wavelength to pass through and shield light with other wavelengths. Therefore, when the second pump light passes through the second signal/pump combiner 3-2, the erbium-doped fiber 1 and the first signal/pump combiner 3-1, and residual second pump light reaches the first optical filter 5-1 in the reverse direction, since the first optical filter 5-1 has a shielding effect on the second pump light, the second pump light cannot pass through the first optical filter 5-1 and reach the first 980-nm pump laser 2-1, thereby eliminating the interference of the second 980-nm pump laser 2-2 on the first 980-nm pump laser 2-1. Similarly, when the first pump light is transmitted to the second optical filter 5-2, since the second optical filter 5-2 can only allow the second pump light to pass through but shield the first pump light, the first pump light cannot pass through the second optical filter 5-2 and reach the second 980-nm pump laser 2-2, thereby eliminating the interferes of the first 980-nm pump laser 2-1 on the second 980-nm pump laser 2-2.
In the embodiment of the present disclosure, the central wavelengths of the first pump light and the second pump light can be selected in a range of 973-981.5 nm. It should be noted that, in the embodiment of the present disclosure, in order to prevent the first pump light from passing through the second optical filter 5-2 and prevent the second pump light from passing through the first optical filter 5-1, the first pump light and the second pump light have different central wavelengths, and the central wavelength difference thereof is in a range of 4-7 nm. If the central wavelength difference is too small, the two pump light is difficult to be separated; and when the central wavelength difference is greater than 4 nm, the two pump light may be distinguished without any difficulty. In the opposing pump structure for twin 980-nm pump lasers of this embodiment, the first 980-nm pump laser 2-1 and the second 980-nm pump laser 2-2 are misaligned to select wavelengths, for example, 973 and 977 nm.
In the opposing pump structure for twin 980-nm pump lasers used in EDFA provided by the present disclosure, the optical path of the 980+980 opposing pump structure is appropriately improved, and an optical filter is added to the optical transmission path of the two pump lights respectively, wherein each optical filter only allows the corresponding pump light to pass through, and does not allow the residual pump light in another direction to pass through, so that the residual pump light in another direction cannot be injected into the opposing pump, thereby avoiding the mutual interference between the two 980 opposing pumps and the failure of the opposing pump lasers. Moreover, compared with the integrated optical isolator, the optical filter has the advantages of small loss, small size and low cost.
The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in the scope of protection of the invention of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201810840108.X | Jul 2018 | CN | national |
The present application is a national phase entry under 35 U.S.C § 371 of International Application No. PCT/CN2018/123439 filed Dec. 25, 2018, which claims priority from Chinese Application No. 201810840108.X filed Jul. 27, 2018, all of which are hereby incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2018/123439 | 12/25/2018 | WO | 00 |
