CN116365346A - Multi-wavelength switchable single longitudinal mode erbium-doped fiber laser based on cascade phase shift grating - Google Patents
Multi-wavelength switchable single longitudinal mode erbium-doped fiber laser based on cascade phase shift grating Download PDFInfo
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Abstract
A multi-wavelength switchable single longitudinal mode erbium-doped fiber laser based on cascade phase shift gratings belongs to the technical fields of fiber communication and instruments and meters. The invention has the advantages that the cascade phase shift grating is used as a multi-channel filter, the tunable uniform grating is used for wavelength switching, and the composite double-loop cavity is used for longitudinal mode filtering, so that stable five-wavelength and switchable single longitudinal mode laser output is realized. The invention plays an important role in the fields of ultra-long distance communication transmission, multi-parameter optical fiber sensing and the like.
Description
Technical Field
The invention relates to a multi-wavelength switchable single longitudinal mode erbium-doped fiber laser based on a cascade phase shift grating, belonging to the technical field of fiber communication and instruments.
Background
Erbium-doped fiber is the most mature rare earth doped fiber at present, and erbium-doped fiber lasers and amplifiers manufactured based on the erbium-doped fiber have been greatly developed and widely applied in optical communication systems. The erbium-doped fiber laser works in 1550nm wave band, has the advantages of small dispersion, low loss, high efficiency, high beam quality factor and the like, and is widely applied to the fields of ultra-long distance transmission, laser radar ranging, intelligent optical fiber sensing, coherent optical communication, gravitational wave detection and the like.
The multi-wavelength switchable and single longitudinal mode stable output is always an important research direction of the fiber laser. The multi-wavelength switchable laser output has important research value in the fields of wavelength division multiplexing, multi-parameter optical fiber sensing and the like. The design of the multi-channel filter and the wavelength selection mechanism is critical to the design of the multi-wavelength switchable laser. For multi-channel filters, there are commonly fabry-perot filters, chirped mole gratings, overlapping gratings, polarization maintaining gratings, sampled gratings, and the like. Phase-shift gratings have many advantages, such as small transmission bandwidth, low insertion loss, no relation to polarization state, etc., and are often used as single-channel filters. The conventional research generally realizes more transmission channels by increasing the number of phase shift points, but along with the increase of the phase shift points, the manufacturing difficulty is increased, although the transmission bandwidth of the phase shift grating is small, the phase shift grating has the advantages of improving the optical fiber sensing precision, good wavelength selection characteristics and the like, is rarely used as a multi-channel filter, and the larger design difficulty becomes the biggest bottleneck for restricting the multi-channel filter.
For wavelength selection, the common methods mainly include nonlinear polarization rotation effect, nonlinear amplifying ring mirror, acoustic wave effect, bending loss dependence, external feedback circuit and the like, but the methods are difficult to operate and bring high cost, and are not the optimal method for realizing wavelength switching.
The single longitudinal mode output can effectively improve the quality factor of the light beam and the stability of the optical fiber communication system. The DFB and DBR lasers can easily achieve stable single longitudinal mode output, but the output laser cannot obtain sufficient gain because of its too short cavity length. The saturable absorber can realize stable single longitudinal mode output, but under the condition of ensuring the filtering effect and enough power output, it is difficult to select a proper length for longitudinal mode filtering. Therefore, the sub-loop cavity is simple to manufacture, the cost is low, the main research direction of the longitudinal mode filter is realized, the longitudinal mode interval can be enlarged through vernier effect, and therefore stable single longitudinal mode output is realized, but the bandwidth of a conventional channel filter is larger, the conventional sub-loop cavity is used for enlarging the free spectrum range to adapt to the bandwidth of each channel through shorter cavity length and smaller cavity length difference so as to realize single longitudinal mode filtering, and the difficulty in manufacturing the sub-loop cavity is brought, and meanwhile, the instability of a laser is increased.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a multi-wavelength switchable single longitudinal mode erbium-doped fiber laser based on a cascade phase shift grating.
The multi-wavelength switchable single longitudinal mode erbium-doped fiber laser based on cascade phase shift grating is characterized in that a pumping source is connected with one end of an input end of a wavelength division multiplexer, an output end of the wavelength division multiplexer is connected with one end of an erbium-doped fiber through a first fiber pipeline, the other end of the erbium-doped fiber is connected with a 1 port of a circulator through a second fiber pipeline, a 2 port of the circulator is connected with one section of a tunable uniform grating through a third fiber pipeline, a 3 port of the circulator is connected with one end of the cascade phase shift grating through a fourth fiber pipeline, the other end of the cascade phase shift grating is connected with one end of an input end of a first fiber coupler through a fifth fiber pipeline, an output end of the first fiber coupler is connected with one end of an input end of a second fiber coupler through a sixth fiber pipeline, one end of an output end of the second fiber coupler is connected with one end of the first fiber coupler through a seventh fiber pipeline, the other output end of the second fiber coupler is connected with one end of the third fiber coupler through a fourth fiber pipeline, one end of the third output end of the third fiber coupler is connected with the other end of the fourth fiber coupler through a fourth fiber coupler, and the other end of the fourth coupler is connected with the other end of the fourth fiber coupler is connected with the other end of the fourth coupler.
The invention has the advantages that the cascade phase shift grating is used as a multi-channel filter, the tunable uniform grating is used for wavelength switching, the composite double-ring cavity is used for longitudinal mode filtering, and stable five-wavelength switchable single longitudinal mode laser output is realized. The invention plays an important role in the fields of ultra-long distance communication transmission, multi-parameter optical fiber sensing and the like.
Compared with the prior art, the invention has the following technical effects:
a multi-wavelength switchable single longitudinal mode erbium-doped fiber laser based on cascaded phase shift gratings is provided. The cascade phase shift grating is used as a multi-channel filter, and channel selection is carried out by tuning a uniform grating matched with the cascade phase shift grating, so that five-channel switchable single-wavelength stable output is realized. The stable single longitudinal mode output is realized by carrying out longitudinal mode filtering by the sub-loop cavity filter consisting of the first optical fiber coupler, the second optical fiber coupler and the third optical fiber coupler.
Considering the difficulty of manufacturing the multi-channel phase shift grating, the invention successfully simulates and manufactures the phase shift grating filter with five channels by cascading the phase shift gratings at two ends. The method overcomes the difficulty in manufacturing the phase shift grating as a multi-channel filter, fully exerts the advantage of narrow transmission bandwidth of the phase shift grating, and provides technical teaching for manufacturing the multi-channel phase shift grating. Meanwhile, the tunable uniform grating is fixed on the micro-displacement platform, and the center wavelength of the tunable uniform grating matched with the phase-shift grating is linearly changed along with the axial stress by changing the axial stress of the uniform grating. In order to ensure good longitudinal mode filtering characteristics of the subcyclic cavity, the free spectral range of the subcyclic cavity is required to be 0.5 to 1 time of the 3dB bandwidth of the grating, and only one composite subchamber is ensured to have an effective transmission passband in the reflection bandwidth of the FBG. Because of the narrow transmission bandwidth of the cascade phase shift grating, the ring length difference of the sub-ring cavity is not required to be controlled below 2cm (the ring length difference of the sub-ring cavity is enlarged to 11.5 cm), the difficulties of optical fiber fusion, cutting and length measurement are reduced, and the stability of the sub-ring cavity is improved.
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The invention, together with a further understanding of the many of its attendant advantages, will be best understood by reference to the following detailed description, when considered in conjunction with the accompanying drawings, which are included to provide a further understanding of the invention, and the accompanying drawings, illustrate and describe the invention and do not constitute a limitation to the invention, and wherein:
fig. 1 shows a multi-wavelength switchable single longitudinal mode erbium-doped fiber laser based on cascaded phase shift gratings according to the present invention.
Fig. 2a is a schematic diagram of a cascaded phase-shift grating according to the present invention.
FIG. 2b is a schematic diagram of simulated transmission spectra of a cascaded phase-shift grating of the present invention.
Fig. 3a is a schematic diagram of the actual transmission spectrum of a cascaded phase-shift grating according to the present invention.
FIG. 3b is a schematic diagram of the reflection spectrum of the tunable uniform grating of the present invention when it is unstressed.
Fig. 3c is a schematic view of the wavelength selection according to the present invention.
FIG. 4a is a single wavelength output spectrum of channel 1 of the present invention, with an optical signal to noise ratio > 53dB, and an inset is a scan spectrum of the output laser within one hour, with a scan time interval of 6 minutes.
FIG. 4b is a single wavelength output spectrum of channel 2 of the present invention, with an optical signal to noise ratio > 62dB, and an inset is a scan spectrum of the output laser within one hour, with a scan time interval of 6 minutes.
FIG. 4c is a single wavelength output spectrum of the channel 3 of the present invention, with an optical signal to noise ratio > 65dB, and an inset is a scan spectrum of the output laser within one hour, with a scan time interval of 6 minutes.
FIG. 4d is a single wavelength output spectrum of the channel 4 of the present invention, with an optical signal to noise ratio > 64dB, and an inset is a scan spectrum of the output laser within one hour, with a scan time interval of 6 minutes.
FIG. 4e is a single wavelength output spectrum of the channel 5 of the present invention, with an optical signal to noise ratio > 66dB, and an inset is a scan spectrum of the output laser within one hour, with a scan time interval of 6 minutes.
FIG. 5 is a graph of the beat frequency of the longitudinal mode of 0-100MHz in single longitudinal mode output, the graph of the beat frequency of the longitudinal mode of the output laser in one hour, and the scanning time interval is 6 minutes.
Corresponding Chinese translations of English appear in the figures: cascade PS-FBG, cascade phase-shift grating, PS-FBG: phase shift grating, wavelength, transmissibility, power; power, frequency, RF Power, radio Frequency Power, mm, nm: nano, dBm: decibel milliwatt, OSNR: optical signal-to-noise ratio, dB: decibels, MHz: megahertz.
Detailed Description
The invention will be further described with reference to the drawings and examples.
It will be apparent that many modifications and variations are possible within the scope of the invention, as will be apparent to those skilled in the art based upon the teachings herein.
The terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
Unless specifically stated or limited otherwise, the terms "mounted," "connected," "secured" and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
It will be understood by those skilled in the art that all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art unless defined otherwise.
In order to facilitate understanding of the embodiments, further explanation will be provided in connection with the following, and the respective embodiments do not constitute limitation of the embodiments.
Example 1: as shown in fig. 1, 2a, 2b, 3a, 3b, 3c, 4a, 4b, 4c, 4d, 4e, and 5, a cascaded phase shift grating-based multi-wavelength switchable single longitudinal mode erbium doped fiber laser uses a cascaded phase shift grating as a multi-channel narrow band filter; the tunable uniform grating performs wavelength switching; the composite double-ring cavity is used as a longitudinal mode filter, so that stable five-wavelength and switchable stable single longitudinal mode laser output is realized. The laser plays an important role in the fields of multi-parameter optical fiber sensing, narrow linewidth laser output, free space optical communication and the like.
A multi-wavelength switchable single longitudinal mode erbium doped fiber laser based on cascaded phase shift gratings comprising: the device comprises a pumping source, a wavelength division multiplexer, an erbium-doped optical fiber, a circulator, a tunable uniform grating, a cascade phase shift grating, a first optical fiber coupler, a second optical fiber coupler, a third optical fiber coupler, a polarization controller and a fourth optical fiber coupler.
The pump source is connected with one end of the input end of the wavelength division multiplexer, the output end of the wavelength division multiplexer is connected with one end of the erbium-doped optical fiber through a first optical fiber pipeline, the other end of the erbium-doped optical fiber is connected with one end of the circulator through a second optical fiber pipeline, the 2 end of the circulator is connected with one section of the tunable uniform grating through a third optical fiber pipeline, the 3 end of the circulator is connected with one end of the cascade phase shift grating through a fourth optical fiber pipeline, the other end of the cascade phase shift grating is connected with one end of the input end of the first optical fiber coupler through a fifth optical fiber pipeline, the output end of the first optical fiber coupler is connected with one end of the input end of the second optical fiber coupler through a sixth optical fiber pipeline, one end of the output end of the second optical fiber coupler is connected with one end of the first optical fiber coupler through a seventh optical fiber pipeline, the other output end of the second optical fiber coupler is connected with one end of the input end of the third optical fiber coupler through an eighth optical fiber pipeline, one end of the output end of the third optical fiber coupler is connected with the other end of the fourth optical fiber coupler through a thirteenth optical fiber pipeline, and the other end of the fourth optical fiber coupler is connected with the other end of the fourth optical fiber coupler.
The 980nm pump source is injected into the circulator through the 980/1550nm wavelength division multiplexer and optically amplifies the erbium-doped optical fiber. The annular device is used for ensuring unidirectional transmission of laser, the uniform grating is fixed on the micro-displacement platform, and axial stress of the grating is changed by adjusting axial displacement of the micro-displacement platform, so that the function of wavelength switching is achieved. Cascaded phase shift gratings (two sections provide multi-channel filtering, sub-ring cavities perform longitudinal mode filtering, and finally light is output from a coupler of a fiber coupler IV (coupling ratio: 90:10).
Example 2: as shown in fig. 1, fig. 2a, fig. 2b, fig. 3a, fig. 3b, fig. 3c, fig. 4a, fig. 4b, fig. 4c, fig. 4d, fig. 4e, fig. 5, the multi-wavelength switchable single longitudinal mode erbium-doped fiber laser based on the cascade phase shift grating is designed and manufactured by using a pump source, a wavelength division multiplexer, an erbium-doped fiber, a circulator, a tunable uniform grating, a cascade phase shift grating, a coupler and a polarization controller, the experimental principle is simple, and the five-channel single-wavelength and switchable single longitudinal mode laser output is realized by changing axial stress.
The technical problems to be solved are the difficulty in manufacturing the multi-channel phase shift grating and the difficulty in ensuring single longitudinal mode output of the fiber laser.
A multi-wavelength switchable single longitudinal mode erbium doped fiber laser based on cascaded phase shift gratings comprising: the pump source 01, the wavelength division multiplexer 02, the erbium-doped optical fiber 03, the circulator 04, the tunable uniform grating 05, the cascade phase shift grating 06, the first optical fiber coupler 07, the second optical fiber coupler 08, the third optical fiber coupler 09, the polarization controller 10, the fourth optical fiber coupler 11, the pump source 01 is connected with one end of the input end of the wavelength division multiplexer 02, the output end of the wavelength division multiplexer 02 is connected with one end of the erbium-doped optical fiber 03 through a first optical fiber pipeline 021, the other end of the erbium-doped optical fiber 03 is connected with the 1 port of the circulator 04 through a second optical fiber pipeline 031, the 2 port of the circulator 04 is connected with one section of the tunable uniform grating 05 through a third optical fiber pipeline 041, the 3 port of the circulator 04 is connected with one end of the cascade phase shift grating 06 through a fourth optical fiber pipeline 042, the other end of the cascade phase shift grating 06 is connected with one end of the input end of the first optical fiber coupler 07 through a fifth optical fiber pipeline 061, the output end of the first optical fiber coupler 07 is connected with one end of the input end of the second optical fiber coupler 08 through a sixth optical fiber pipeline 071, one end of the output end of the second optical fiber coupler 08 is connected with the input end of the first optical fiber coupler 07 through a seventh optical fiber pipeline 081, the other output end of the second optical fiber coupler 08 is connected with one end of the input end of the third optical fiber coupler 09 through an eighth optical fiber pipeline 082, one end of the output end of the third optical fiber coupler 09 is connected with the other input end of the second optical fiber coupler 08 through a ninth optical fiber pipeline 091, the other output end of the third optical fiber coupler 09 is connected with one end of the polarization controller 10 through a tenth optical fiber pipeline 092, the other end of the polarization controller 10 is connected with the input end of the fourth optical fiber coupler 11 through an eleventh optical fiber pipeline 101, one end of the output end of the fourth optical fiber coupler 11 is connected to the other input end of the wavelength division multiplexer 02 through a twelfth optical fiber pipe 111, and the other output end of the fourth optical fiber coupler 11 outputs laser light through a thirteenth optical fiber pipe 112.
Wherein, the main cavity of fiber laser is by: 980/1550nm wavelength division multiplexer 02, first optical fiber tube 021, erbium doped fiber 03, second optical fiber tube 031, circulator 04, third optical fiber tube 041, tunable uniform grating 05, fourth optical fiber tube 042, cascaded phase shift grating 06, fifth optical fiber tube 061, tenth optical fiber tube 092, polarization controller 10, eleventh optical fiber tube 101, 90: a fourth 10 optical fiber coupler 11 and a twelfth optical fiber pipeline 111.
The length of the main cavity of the multi-wavelength switchable single longitudinal mode erbium-doped fiber laser is 18.2 meters, and the main cavity is formed according to the formula
Where Δ is the longitudinal mode spacing and c is the speed of light in vacuum 3×10 8 m/s, n is the refractive index of the optical fiber of 1.447, L is the length of the main cavity, and the calculated longitudinal mode interval is 11.4MHz.
The pump light generated by the pump source 01 enters the light path through the 980/1550nm wavelength division multiplexer 02, the erbium-doped optical fiber 03 realizes the particle number inversion and generates the stimulated radiation light amplification effect of light, the circulator 04 ensures the unidirectional propagation of the light, the tunable uniform grating 05 realizes the channel selection, and the central wavelength is changed by changing the axial stress so as to perform the wavelength selection. The cascaded phase-shift grating 06 provides five-channel ultra-narrow bandwidth filtering as a multi-channel filter. The polarization controller 10 is used for adjusting the birefringence generated by the uneven fiber material in the cavity, 10% of the ports of the coupler IV 11 are used for outputting laser, and the rest 90% of the laser continues to circularly oscillate in the cavity.
As shown in fig. 2a, the cascade phase shift grating 06 is formed by cascading two phase shift gratings with the length of l=10mm, the phase shift point of the first phase shift grating is at 0.3L, and the phase shift amount is pi; the phase shift point of the second phase shift grating is pi at 0.7L, and no space exists between the two gratings. Fig. 2b shows the transmission spectrum of the cascaded phase shift grating simulated by the transmission matrix analysis method, and fig. 3a shows the actual transmission spectrum, wherein the actual transmission spectrum of the cascaded phase shift grating matches with the theoretical analysis through the comparative analysis. The 3dB bandwidths of the five channels of the cascade phase shift grating are respectively 0.02nm,0.021nm,0.018nm,0.021nm and 0.024nm, and the cascade grating realizes the manufacture of the five-channel phase shift grating only by a phase shift grating cascade method of two single-phase shift points, thereby reducing the manufacture difficulty and simultaneously ensuring the advantage of extremely narrow bandwidth of the phase shift grating. To ensure good channel selection characteristics, the 3dB bandwidth of the tunable uniform grating 05 is designed to be 0.066nm. The wavelength switching example of the tunable uniform grating 05 is shown in fig. 3c, the central wavelength of the tunable uniform grating 05 is changed by adjusting the displacement of the displacement platform, the ultra-narrow bandwidth reflection spectrum of the tunable uniform grating 05 can well cover each channel, good channel filtering is achieved, as shown in fig. 4a, fig. 4b, fig. 4c, fig. 4d and fig. 4e, each channel of the cascade phase-shift grating can achieve stable single-wavelength laser output, and the tunable uniform grating can stably work for 60 minutes under the condition of Gao Guangxin to noise ratio.
The sub-ring cavity longitudinal mode filter can be disassembled into a first ring cavity and a second ring cavity, the first ring cavity is composed of a first optical fiber coupler 07, a sixth optical fiber pipeline 071, a second optical fiber coupler 08 and a seventh optical fiber pipeline 081, and the second ring cavity is composed of a second optical fiber coupler 08, an eighth optical fiber pipeline 082, an optical fiber coupler 03 and a ninth optical fiber pipeline 091. The coupling ratio of the first optical fiber coupler 07, the second optical fiber coupler 08 and the third optical fiber coupler 09 is 50: 50. 90:10 and 50: the lengths of the sixth fiber duct 071, the seventh fiber duct 081, the eighth fiber duct 082, and the ninth fiber duct 091 were 90.9cm, 100.8cm, 83.5cm, and 96.7cm, respectively. Compared with the interference ring formed by other conventional multiple couplers, the sub-ring cavity filter realizes stable longitudinal mode filtering, as shown in fig. 3a, 3b and 3c, the cavity length difference of the first ring cavity and the second ring cavity is 11.5cm, and the ring length difference of the sub-ring cavity is not required to be controlled below 2cm due to the extremely narrow transmission bandwidth of the cascade phase shift grating 05, so that the difficulties of optical fiber fusion, cutting and length measurement are reduced, and the stability of the sub-ring cavity is improved.
Example 3: as shown in fig. 1, 2a, 2b, 3a, 3b, 3c, 4a, 4b, 4c, 4d, 4e, and 5, a multi-wavelength switchable single longitudinal mode erbium-doped fiber laser based on a cascaded phase shift grating includes: the pump source 01, the wavelength division multiplexer 02, the erbium-doped optical fiber 03, the circulator 04, the tunable uniform grating 05, the cascade phase shift grating 06, the first optical fiber coupler 07, the second optical fiber coupler 08, the third optical fiber coupler 09, the polarization controller 10, the fourth optical fiber coupler 11, the pump source 01 is connected with one end of the input end of the wavelength division multiplexer 02, the output end of the wavelength division multiplexer 02 is connected with one end of the erbium-doped optical fiber 03 through a first optical fiber pipeline 021, the other end of the erbium-doped optical fiber 03 is connected with the 1 port of the circulator 04 through a second optical fiber pipeline 031, the 2 port of the circulator 04 is connected with one section of the tunable uniform grating 05 through a third optical fiber pipeline 041, the 3 port of the circulator 04 is connected with one end of the cascade phase shift grating 06 through a fourth optical fiber pipeline 042, the other end of the cascade phase shift grating 06 is connected with one end of the input end of the first optical fiber coupler 07 through a fifth optical fiber pipeline 061, the output end of the first optical fiber coupler 07 is connected with one end of the input end of the second optical fiber coupler 08 through a sixth optical fiber pipeline 071, one end of the output end of the second optical fiber coupler 08 is connected with the input end of the first optical fiber coupler 07 through a seventh optical fiber pipeline 081, the other output end of the second optical fiber coupler 08 is connected with one end of the input end of the third optical fiber coupler 09 through an eighth optical fiber pipeline 082, one end of the output end of the third optical fiber coupler 09 is connected with the other input end of the second optical fiber coupler 08 through a ninth optical fiber pipeline 091, the other output end of the third optical fiber coupler 09 is connected with one end of the polarization controller 10 through an optical fiber tenth optical fiber pipeline 092, the other end of the polarization controller 10 is connected with the input end of the fourth optical fiber coupler 11 through an optical fiber eleventh optical fiber pipeline 101, one end of the output end of the fourth optical fiber coupler 11 is connected to the other input end of the wavelength division multiplexer 02 through a twelfth optical fiber pipe 111, and the other output end of the fourth optical fiber coupler 11 outputs laser light through a thirteenth optical fiber pipe 112.
The pump source 01 provides 980nm pump light, the generated pump light enters a light path through the 980/1550nm wavelength division multiplexer 02, the erbium-doped optical fiber 03 realizes particle inversion and generates stimulated radiation light amplification effect of light, the circulator 04 ensures unidirectional propagation of the light, the tunable uniform grating 05 realizes channel selection, the center wavelength is changed by changing axial stress so as to perform wavelength selection, the cascade phase shift grating 06 serves as a multichannel filter to provide five-channel ultra-narrow bandwidth filtering, the polarization controller 10 is used for adjusting birefringence generated by nonuniform optical fiber materials in a cavity, 10% ports of the coupler four 11 are used for outputting laser, and the rest 90% of laser continues to circularly oscillate in the cavity.
The cascade phase shift grating 06 is formed by cascading two phase shift gratings with the length of L=10mm, the phase shift point of the first phase shift grating is positioned at 0.3L, the phase shift size is pi, the phase shift point of the second phase shift grating is positioned at 0.7L, the phase shift size is pi, and the center wavelengths of the five channels are respectively: 1549.94nm,1550.06nm,1550.16nm,1550.24nm and 1550.36nm; the 3dB bandwidths were 0.020nm,0.021nm,0.018nm,0.021nm,0.024nm, respectively.
The sub-ring cavity can be disassembled into a first ring cavity and a second ring cavity, the first ring cavity is composed of a first optical fiber coupler 07, a sixth optical fiber pipeline 071, a second optical fiber coupler 08 and a seventh optical fiber pipeline 081, the second ring cavity is composed of a second optical fiber coupler 08, an eighth optical fiber pipeline 082, an optical fiber coupler 03 and a ninth optical fiber pipeline 091, and the coupling ratio of the first optical fiber coupler 07, the second optical fiber coupler 08 and the third optical fiber coupler 09 is 50 respectively: 50. 90:10 and 50:50, the lengths of the sixth fiber duct 071, the seventh fiber duct 081, the eighth fiber duct 082, and the ninth fiber duct 091 were 90.9cm, 100.8cm, 83.5cm, and 96.7cm, respectively, and the difference in loop length was 11.5cm.
The center wavelength of the tunable uniform grating 05 is 1549.83nm, the 3dB bandwidth is 0.066nm, the tunable uniform grating 05 is fixed on a micro-displacement platform, and the axial stress of the grating is changed through the micro-displacement platform, so that the center wavelength of the grating is changed, and the wavelength switching operation is realized.
The polarization controller 10 is a squeeze type polarization controller, and the azimuth angle and the phase retardation of the squeeze type polarization controller can be continuously adjusted respectively, so that the polarization state of the transmitted light wave can be changed by rotating the squeeze device and mechanically squeezing the optical fiber, and any input polarization state can be converted into a required output polarization state.
The coupling ratio of the fiber coupler four 11 is 90:10 The 10% port is used as an output and the 90% port is connected to the other input of the wavelength division multiplexer 02.
As described above, the embodiments of the present invention have been described in detail, but it will be apparent to those skilled in the art that many modifications can be made without departing from the spirit and effect of the present invention. Accordingly, such modifications are also entirely within the scope of the present invention.
Claims (8)
1. The multi-wavelength switchable single longitudinal mode erbium-doped fiber laser based on cascade phase shift grating is characterized in that a sub-ring cavity filter consisting of a first fiber coupler, a second fiber coupler and a third fiber coupler carries out longitudinal mode filtering, a pumping source is connected with one end of an input end of a wavelength division multiplexer, an output end of the wavelength division multiplexer is connected with one end of an erbium-doped fiber through a first fiber pipeline, the other end of the erbium-doped fiber is connected with a 1 port of a circulator through a second fiber pipeline, a 2 port of the circulator is connected with one section of a tunable uniform grating through a third fiber pipeline, a 3 port of the circulator is connected with one end of the cascade phase shift grating through a fourth fiber pipeline, the other end of the cascade phase shift grating is connected with one end of the input end of the first fiber coupler through a fifth fiber pipeline, an output end of the first fiber coupler is connected with one end of the input end of the second fiber coupler through a sixth fiber pipeline, one end of the output end of the second optical fiber coupler is connected with the input end of the first optical fiber coupler through a seventh optical fiber pipeline, the other output end of the second optical fiber coupler is connected with one end of the input end of the third optical fiber coupler through an eighth optical fiber pipeline, one end of the output end of the third optical fiber coupler is connected with the other input end of the second optical fiber coupler through a ninth optical fiber pipeline, the other output end of the third optical fiber coupler is connected with one end of the polarization controller through a tenth optical fiber pipeline, the other end of the polarization controller is connected with the input end of the fourth optical fiber coupler through an eleventh optical fiber pipeline, one end of the output end of the fourth optical fiber coupler is connected with the other input end of the wavelength division multiplexer through a twelfth optical fiber pipeline, and the other output end of the fourth optical fiber coupler outputs laser through a thirteenth optical fiber pipeline.
2. The cascade phase shift grating-based multi-wavelength switchable single longitudinal mode erbium-doped fiber laser of claim 1, wherein the main cavity length of the multi-wavelength switchable single longitudinal mode erbium-doped fiber laser is 18.2 meters, according to the formula
Where Δ is the longitudinal mode spacing and c is the speed of light in vacuum 3×10 8 m/s, n is the refractive index of the optical fiber of 1.447, and L is the longitudinal mode spacing calculated for the main cavity length of 11.4MHz.
3. The cascade phase shift grating-based multi-wavelength switchable single longitudinal mode erbium-doped fiber laser according to claim 1, wherein the pump source provides 980nm pump light, the generated pump light enters a light path through a 980/1550nm wavelength division multiplexer, the erbium-doped fiber achieves particle number inversion and generates stimulated radiation light amplification effect of light, the circulator ensures unidirectional propagation of light, the tunable uniform grating achieves channel selection, the central wavelength is changed by changing axial stress so as to perform wavelength selection, the cascade phase shift grating serves as a multi-channel filter to provide five-channel ultra-narrow bandwidth filtering, the polarization controller is used for adjusting birefringence generated by uneven fiber materials in a cavity, 10% of ports of the fourth coupler are used for outputting laser, and the rest 90% of laser continues circulating oscillation in the cavity.
4. The multi-wavelength switchable single longitudinal mode erbium-doped fiber laser based on the cascade phase shift grating according to claim 3, wherein the cascade phase shift grating is formed by cascading a first phase shift grating and a second phase shift grating, the lengths of the two sections are respectively l=10mm, the phase shift point of the first phase shift grating is positioned at 0.3L, the phase shift size is p, the phase shift point of the second phase shift grating is positioned at 0.7L, the phase shift size is p, and the center wavelengths of the five channels are respectively: 1549.94nm,1550.06nm,1550.16nm,1550.24nm and 1550.36nm; the 3dB bandwidths were 0.020nm,0.021nm,0.018nm,0.021nm,0.024nm, respectively.
5. The cascade phase shift grating-based multi-wavelength switchable single longitudinal mode erbium-doped fiber laser of claim 1, wherein the sub-ring cavity filter is capable of being disassembled into a first ring cavity and a second ring cavity, the first ring cavity is composed of a first fiber coupler, a sixth fiber pipeline, a second fiber coupler and a seventh fiber pipeline, the second ring cavity is composed of a second fiber coupler, an eighth fiber pipeline, a fiber coupler and a ninth fiber pipeline, and the coupling ratio of the first fiber coupler, the second fiber coupler and the third fiber coupler is 50 respectively: 50. 90:10 and 50: the lengths of the sixth optical fiber pipeline, the seventh optical fiber pipeline, the eighth optical fiber pipeline and the ninth optical fiber pipeline are respectively 90.9cm, 100.8cm, 83.5cm and 96.7cm, and the ring length difference is 11.5cm.
6. The cascade phase shift grating-based multi-wavelength switchable single longitudinal mode erbium-doped fiber laser of claim 1, wherein the tunable uniform grating has a center wavelength of 1549.83nm and a 3db bandwidth of 0.066nm, and is fixed on a micro-displacement platform, and the axial stress of the grating is changed by the micro-displacement platform so as to change the center wavelength of the grating, thereby realizing wavelength switching operation.
7. The cascade phase shift grating-based multi-wavelength switchable single longitudinal mode erbium-doped fiber laser of claim 1, wherein the polarization controller is an extrusion type polarization controller, the azimuth angle and the phase retardation of which are continuously adjusted respectively, and the polarization state of the transmitted light wave is changed by rotating the extruder and mechanically extruding the fiber, so as to convert any input polarization state into a desired output polarization state.
8. The cascade phase shift grating based multi-wavelength switchable single longitudinal mode erbium doped fiber laser of claim 1, wherein the coupling ratio of fiber coupler four is 90:10 The 10% port is used as the output and the 90% port is connected to the other input of the wavelength division multiplexer.
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