CN1240166C - All optical fibre adjustable width continuous spectrum laser pump source for superflat wide-band Raman amplification - Google Patents
All optical fibre adjustable width continuous spectrum laser pump source for superflat wide-band Raman amplification Download PDFInfo
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Abstract
The present invention relates to a full optical fiber adjustable wide continuous spectrum laser pumping source for super flat wideband Raman amplification (FBCSL), which belongs to the technical field of high-speed wideband optical fiber communication. The present invention is characterized in that the present invention uses high optical nonlinearity optical fiber (HNL-DSF) with the characteristic of approximate flat zero dispersion in the position of Raman laser wavelength as gain media; both ends of the HNL-DSF is connected with wideband reflectors to form an adjustable wide continuous spectrum Raman laser with a full optical fiber Fabry-Perot (F-P) cavity or connected with a wideband wavelength division multiplex optical fiber coupler to form an adjustable wide continuous spectrum Raman laser with a full optical fiber ring cavity; the HNL-DSF can also be replaced by new generation photon crystal fiber (PCF). The present invention is used as a pumping source for producing super flat wideband optical fiber Raman amplifying gain spectrums, the spectral bandwidth and the spectral pattern of the present invention can be adjusted, and the service band is flexible; the full optical fiber structure is simple, and the loss of pumping light is reduced; the PCF technique is introduced to realize the small-scale FBCSL with high pumping conversion efficiency.
Description
Technical field
The invention belongs to fiber amplifier and laser and high-speed wideband technical field of optical fiber communication, particularly a kind of method and complete wide continuous spectrum laser pump source of optical-fibre adjustable (FBCSL) thereof of realizing that in dense wave division multipurpose (DWDM) optical communication system the balanced fiber Raman of superflat wide-band amplifies.
Background technology
The appearance of erbium-doped fiber amplifier (EDFA) (1986) once caused the once great leap of Fibre Optical Communication Technology development, adopted wavelength division multiplexing (WDM) transmission technology of EDFA to become the dominant direction that current optical fiber communication engineering system develops.Along with the rapid growth of multiple communication services such as data, voice, image, multimedia in recent years, the wdm optical communication system transmission capacity is constantly upgraded.As the Optical Amplification Technology of a new generation, fiber Raman amplifier (FRA) demonstrate with its unique low noise, broadband, excellent specific property that service band is adjustable at a high speed, tempting application prospect in the big capacity, long distance D WDM Networks of Fiber Communications.In recent years, the technological break-through of high power pumping lasing light emitter has effectively promoted the research and development progress of FRA, and its engineering practicalization more and more receives publicity, and has become in recent years research and development " focus " both at home and abroad.
The operation principle of FRA is different fully with EDFA, and it is nonlinear optical effect-stimulated Raman scattering (SRS) of utilizing high power laser light pump transmission optical fiber self-light signal is directly amplified.Such as, with 14 * * pump light of nm wave band injects conventional quartz transport optical fiber, can be 15 * * the nm wave band obtains the gain of light.
Fig. 1 provides the light channel structure figure of backward pumping distributed optical fiber Raman amplifier (B-DFRA).14 * * pumping laser (Pump) of nm wavelength links 111 ends of wave division multiplex coupler (WDM), and by the SRS of the coupling injection Transmission Fibers between the 111-113 end with excitation fiber, 15 * * flashlight of nm wavelength imports from the Transmission Fibers left end, and obtain the distributed Raman gain in the whole transmission course in optical fiber, lead directly to through the 113-112 of WDM end through amplifying signal light and export from the Transmission Fibers right-hand member.
Compare with EDFA, FRA has following important feature:
1, the service band of FRA is determined by pumping wavelength, does not resemble the restriction that is subjected to er-doped emission of ions wavelength the EDFA.Therefore, as long as adopt the pump light of suitable wavelength can in the whole transmission bandwidth scope (1292-1660nm) of optical fiber, realize the broadband light amplification, so be easy to expand new communication wavelengths scope.
2, the intrinsic gain spectrum of single wavelength pumping FRA is " triangle ", the about 15nm of smooth scope, adopt a plurality of wavelength pumpings the further broadening of gain spectral suitably can be selected the number and the corresponding power ratio thereof of pumping wavelength, can realize the wideband gain spectrum that rises and falls less.
3, FRA can adopt (DFRA) mode of amplification that distributes, has good noise characteristic, this is significant to the high-speed wideband optical fiber telecommunications system, not only help to increase intersegmental span, prolong the transmission range of link and reduce cost, also help old system to the higher rate upgrading and need not to change the system link structure.
The typical transmission bandwidth of dwdm optical communication system now is 32nm (C-band) or 80nm (C+L wave band), for the DFRA that uses in the system, requires it to provide the equilibrium of gain or power to amplify in whole transmission bandwidth scope to optical channel, specifically comprises:
1, DFRA should have smooth gain spectral in whole transmission bandwidth
The synthetic gain spectral big rise and fall of multi wavelength pumping DFRA; In addition, SRS additional between the pump light of different wave length and between the flashlight can make energy shift, and causes gain spectral upward towards long wavelength side.The fluctuating of gain spectral will cause the channel gain of different wave length different with tilting, and this gain inequality also can amplify accumulate and increase the weight of with cascade, cause some channel power sharp increase and other channel is suppressed, and make the channel light signal to noise ratio severe exacerbation of low gain.
2, the flat gain spectrum of DFRA should be online adjustable under the system dynamics operation
In the optical communication network of reality, the variation of routed path can make each channel power that enters the node optical amplifier change; In addition, the number of channel by image intensifer also may cause the dynamic unbalance of gain spectral and output power spectrum with the reconstruct of network or changing up and down of channel.For DFRA, when the number of input signal and power change, also can make output spectra occur tilting owing to the SRS effect of interchannel.
So far, solving the smooth adjustable way of raman gain spectrum is: adopt the stack of the raman gain spectrum of discrete a plurality of wavelength pumpings generations to realize the broadband amplification, be implemented in the smooth raman gain spectrum of the minimum that rises and falls in the transmission bandwidth by appropriate design pump parametric (pumping wave long number, wavelength value and power ratio thereof); Realize the adjustment of gain spectral gradient by the power ratio of adjusting each pumping wavelength.
Fig. 2 (a) provides the raman gain spectrum that adopts 3,4,6,8 pumping wavelengths to produce respectively, the power ratio of every group of pumping wavelength all through optimizing so that corresponding gain spectral rises and falls minimum.Fig. 2 (b) is the power configuration of 8 pumping wavelengths.As seen from the figure, along with increasing of pumping wave long number, the fluctuating of synthetic raman gain spectrum reduces.
At present, the multi-wavelength pumping source as fiber Raman amplifier has two classes:
1, multi-wavelength semiconductor laser (LD) combination pumping source (S.Namiki and Y.Emiori, IEEE Journal on Selectedtopics of Quantum Electronics, vol.7, no.1,2001).With many 14 * * LD of nm different wave length is combined into beam of laser output by the multi-wavelength wave multiplexer, for eliminating polarization correlated that fiber Raman amplifies, each pumping wavelength is synthetic a branch of by the polarized composite wave device by the LD of two cross-polarizations outputs.Reported with 14 of 12 wavelength * * nm LD combination pumping source realizes that super smooth fiber Raman amplifies, and by adjusting the adjustment that each wavelength pump power realizes that gain spectral tilts.
Yet, use too much pumping LD that system cost is increased, encapsulate also very difficult; And too much pumping wavelength needs complicated pumping wave multiplexer spare, and corresponding pump light loss is bigger, has reduced the utilization ratio of pumping; In addition, too much pumping wavelength also makes by regulating pump power and realizes that the dynamic adjustment of gain spectral becomes very complicated.Therefore, in actual applications, often only use 2～5 pumping wavelengths, the flatness of gain spectral correspondingly is restricted.For example, for the gain spectral of 80nm bandwidth, as adopt 4 or 5 pumping wavelengths, gain fluctuation minimum under the 10dB average gain can reach 1.5dB or 1.0dB respectively.
2, multi-wavelength light fibre optic Raman laser pumping source (Lorcy L, et al., ECOC ' 2002, vol.2,4.1.2,2002 for Leplingard F, Borne S).Adopt the super high power multimode LD pumping double clad ytterbium-doping optical fiber laser of 915nm wavelength to produce the laser of 1117nm wavelength, be converted to 14 again through the Raman shift frequency fiber grating chamber of 3 grades (mixing P optical fiber) or 5 grades of (mixing Ge optical fiber) cascades * * laser of nm wavelength.At present, such laser can be simultaneously 14 * * 3～6 optical maser wavelengths of nm wave band output, the 915nm pumping light power is up to 10 watts of levels, 14 * * the nm power output reaches more than 1 watt, can also regulate the power of each wavelength by the output coupler of adjusting each wavelength.
Yet this type of laser output wavelength number is limited, and the effect of the LD combination pumping source of gain spectrum flattening degree number of wavelengths same as described above is suitable; In addition, the Output optical power of each wavelength is interrelated, makes equally by regulating pump power and realizes that the dynamic adjustment of gain spectral becomes very difficult.
In sum, although DFRA has tempting low noise broadband amplification characteristic, although the capacity upgrade of current optical communication system has eager expectation to it, even on international optical communication market, released the DFRA of commodity, but DFRA for discrete multi wavelength pumping, no matter adopt which kind of laser pump source, all exist some shortcoming that are difficult to avoid to bring difficulty for its engineering practicability, subject matter comprises:
1. consider from the equilibrium of channel light signal to noise ratio, because the intrinsic fluctuating of discrete multi wavelength pumping stack raman gain spectrum, add between the different pumping wavelengths and the influence of the additional SRS between the unlike signal light, the flatness of raman gain spectrum is restricted, and the fluctuating of this gain spectral also can be accumulated increase in the cascade amplification system, unbalance (the K.Ennser and V.L.da Silva, ECOC ' 2000) that causes DWDM transmission channel Optical Signal To Noise Ratio.
2. consider from the dynamic regulation of the WDM of system channel gain and power: the synthetic gain spectral of discrete multi wavelength pumping is formed by stacking by the gain contribution of each pumping wavelength, and the additional SRS effect in the pumping amplification process makes each wavelength pump light not independent mutually to the contribution of gain spectral.Therefore, attempt by adjust online adjustment that pump power realizes the DFRA gain spectral more than EDFA much more difficult (J.K.Rhee, M.J.Li, P.Iydroose and et al., OFC ' 2002, PaperPD38,2002).
3. consider from engineering cost and security of operation: LD combination pumping source needs many high-power LD to close bundle by the wave multiplexer spare of complexity; And the fibre optic Raman laser pumping source needs the multimode LD pumping source and the complicated double clad Yb dosed optical fiber and the multi-stage fiber grating chamber Raman shift frequency of nearly 10 watts of level power equally.These two kinds of raman pump sources all will make the system engineering cost heighten, and require the necessary security protection of strengthening light laser in system's installation, debugging and running.
Therefore, address these problems conscientiously just to become and advance FRA practicability and optical fiber telecommunications system crucial difficult point to big capacity upgrade.
Summary of the invention
The objective of the invention is to weak point, propose a kind of wide continuous spectrum laser pump source of full optical-fibre adjustable that is used to realize the balanced fiber Raman amplification of superflat wide-band at prior art.Its basic ideas are: the basic law that develops according to the spectrum stack of multi wavelength pumping raman gain fiber: since the suitable pumping wave long number of power configuration is many more, the fluctuating of synthetic raman gain spectrum is more little, as a plurality of discrete optical maser wavelength pumpings being pushed into the laser pumping of the limit-employing broadband continuous spectrum, should be able to realize that the superflat wide-band fiber Raman amplifies.Key is to realize the adjustable sharp continuously pump laser of penetrating of a kind of wide range.
Comprehensive nonlinear optics interaction process in the silica fiber resonant cavity under the operation principle of the wide continuous spectrum laser pump source of full optical-fibre adjustable of the present invention encourages based on light laser: stimulated Raman scattering (SRS) effect provides the gain of light, nonlinear phase modulation and four wave mixing (FWM) near the zero-dispersion wavelength, the parameter enlarge-effect makes spectrum widening, realizes sharp continuously the penetrating that wide range is adjustable.Specifically describe as follows:
The first, all optical fiber cavity Raman is sharp penetrates
Based on the stimulated Raman scattering in the silica fiber (SRS), when adopting one-wavelength laser pumping silica fiber, will be lower than pump frequency 13.2THz place generation raman gain spectrum, a Raman gain of representing with decibel (dB) is:
G
R(dB)≈4.343P
pL
effg
R/A
eff (1)
This shows Raman gain G
k(dB) size is with pump power P
p, optical fiber effective length L
Eff, optical fiber Raman gain coefficienct g
RAnd the 1/A reciprocal of optical fiber effective cross-sectional area
EffBe the exponential increase rule.The Raman gain spectrum width is relevant with pump power, and is determined by the vibration mode of quartz medium, under the 10dB peak gain, and the about 15～20nm in flat gain spectrum district.If suitably introduce the light feedback mechanism, for example, adopt wave division multiplex coupler that optical fiber is linked to be annular chamber, or at optical fiber two termination reflective optical systems formation Fabry-Perot line chamber, promptly constitute fibre optic Raman laser, the continuous Raman of narrow linewidth is sharp to be penetrated as long as Raman gain greater than the optical fiber cavity loss, can produce.See that by (1) formula high efficiency fibre optic Raman laser should adopt that core diameter is thin, Raman gain coefficienct g
RHigher high optical nonlinearity optical fiber, and increase pump power and the optical fiber effective length can obtain high-power raman laser output.Since the centre wavelength of raman gain spectrum only by the pumping wavelength decision, selects suitable pumping wavelength can be in the whole transmission bandwidth of silica fiber (1292-1660nm) realize that Raman is sharp and penetrate.
The second, the sharp broadening of spectrum of penetrating of fiber Raman
Based on the comprehensive function of multiple nonlinear optical effect in the silica fiber raman laser chamber, comprise between nonlinear phase modulation and each longitudinal mode four wave mixing (FWM) etc., can be with the raman laser spectrum widening near zero-dispersion wavelength.
Consideration is ω at the optical fiber medium frequency
1And ω
2Continuous beat frequency can take place in two longitudinal modes of co-propagate each other, and frequency is ω=ω
2-ω
1Intensity modulation will cause that the optical fibre refractivity relevant with light intensity I changes n
2(I, ω).The optical fiber medium frequency is ω
3The 3rd longitudinal mode will be because of n
2(I ω) is subjected to phase modulated, and causing it to produce frequency is ω
4=ω
3± (ω
2-ω
1) sideband; Equally, frequency is ω
3And ω
1Also beat frequency mutually of two longitudinal modes, making frequency is ω
2Longitudinal mode also to produce frequency be ω
4=ω
2± (ω
3-ω
1) sideband, and new side frequency ω
2+ (ω
3-ω
1) and aforementioned side frequency ω
3+ (ω
2-ω
1) overlap four wave mixing that Here it is (FWM) process.Suppose that interactional each longitudinal mode polarization state is in full accord, then frequency is ω
4=ω
3+ ω
2-ω
1The wave field complex amplitude can be expressed as (D.Marcuse, A.R.Chraplyvy and R.W.Tkach, J.Lightwave Technol., vol.9, no.1,1991)
A wherein
1, A
2And A
3Be the complex amplitude of three longitudinal mode components, if ω
3=ω
2, g
321=1, otherwise g
321=2.γ is the nonlinear fiber coefficient, and α is fibre loss, and L is a fiber lengths.Δ β=β
1+ β
4-β
2-β
3Be the phase misalignment dosage.Notice the longitudinal mode that has many equifrequent spacings (c/nL) in the fiber laser cavity, each longitudinal mode all might intercouple by this FWM process, swashs when causing many longitudinal modes to penetrate and make the raman laser spectrum widening.See that from (2) formula along with the enhancing of pump power, it is very fast that the lifting of each longitudinal mode power increases the FWM field component; In addition, β is more little for phase misalignment dosage Δ, and the FWM wave field is also strong more, and this all makes the sharp spectrum of penetrating of corresponding Raman open up widelyer.Therefore, be chosen in the optical fiber that the raman laser wave band has nearly smooth zero dispersion characteristics and make gain medium, can realize in the optical fiber cavity of light laser pumping that wide range is sharp continuously to penetrate.
Three, fiber Raman swashs the regulation and control of penetrating spectrum shape
As adopt a plurality of different wavelength of laser pumping optical fibers chamber, and then can form with corresponding each Raman excitation wavelength is that a plurality of sharp continuously of center penetrated bands of a spectrum, the synthetic sharp spectrum of penetrating is with further broadening; By interval and the relative power size of adjusting each pumping wavelength, can carry out flexibly and effectively adjusting to the output spectrum shape of laser.
So, use the wide continuous spectrum laser of described full optical-fibre adjustable to make pumping source, can realize that the balanced fiber Raman of superflat wide-band amplifies.
The invention is characterized in: it be a kind of employing near the raman laser wavelength, have nearly smooth zero dispersion characteristics high optical nonlinearity optical fiber (HNL-DSF) as gain media, and constitute the adjustable wide continuous spectrum Raman laser in full-optical fiber F-P chamber in Fabry-Perot (F-P) chamber at above-mentioned HNL-DSF two termination broadband light reflectors; Full-optical fiber F-P laserresonator is wherein penetrated the optical delivery fiber passage and is constituted along swashing by band optical fiber loop completely reflecting mirror FRR32, HNL-DSF and band optical fiber loop partially reflecting mirror FRR31 successively; Particularly, it contains:
HNL-DSF；
The pumping source that the heavy pumping laser of a plurality of wavelength constitutes;
Wideband WDM fiber coupler WDM31: the pump light that above-mentioned pumping source sends is coupled into to swash by it and penetrates the optical delivery fiber passage and excite coupled above-mentioned HNL-DSF; Band optical fiber loop completely reflecting mirror FRR32: it is penetrated optical coupling and constitutes than the symmetrical fiber coupler 3dBDC32 that is 50% swashing by what the residual pump light of an input optical fibre port and above-mentioned HNL-DSF spilt that port links to each other, two output optical fibre direct port connection are helped the light feedback control loop;
Band optical fiber loop partially reflecting mirror FRR31: it is penetrated optical coupling and constitutes than the asymmetric optical fiber coupler xdBDC33 that is xdB swashing by what an input optical fibre port and above-mentioned WDM31 sharp penetrated that the transmission line fiber port links to each other, two output optical fibre direct port connection become part light feedback control loop, the value of x will be according to best laser output condition design, and the part transmission fiber port of xdBDC33 is the delivery outlet of laser.
Feature of the present invention also is: it be a kind of employing near the raman laser wavelength, have nearly smooth zero dispersion characteristics high optical nonlinearity optical fiber (HNL-DSF) as gain media, and with the wideband WDM fiber coupler HNL-DSF is linked to be the adjustable wide continuous spectrum Raman laser of all optical fiber ring cavity of ring resonator at the HNL-DSF two ends; It contains:
HNL-DSF；
The fiber ring laser resonant cavity of clockwise direction (CW) circulation: it is by penetrating wideband WDM fiber coupler WDM41, optical isolator ISO that optical delivery fiber passage clockwise direction and HNL-DSF link to each other successively and penetrate optical coupling and constitute than the broadband optical fiber coupler xdBDC43 that is xdB swashing along swashing, and the value of x will design according to best laser output condition; The sharp light of penetrating of CW direction circulation is by xdBDC43 coupling back output in optic fiber ring-shaped cavity;
The pumping source that the light laser of a plurality of wavelength constitutes: the pump light that it sends is coupled into to swash by above-mentioned WDM41 and penetrates the optical delivery fiber passage and excite coupled above-mentioned HNL-DSF;
The residual pump light feedback device: the fiber port that residual pump light is derived in the coupling that it is serially connected in wideband WDM fiber coupler WDM42 in the optic fiber ring-shaped cavity and an input optical fibre port and described WDM42 by another that spills that port links to each other with the residual pump light of above-mentioned HNF-DSF links to each other, two output optical fibre direct port connection become loop completely reflecting mirror FRR to the pump light coupling ratio is that 50% fiber coupler 3dBDC44 constitutes;
Feature of the present invention also is: described HNL-DSF can be the photonic crystal fiber (PCF) that a new generation has high optical nonlinearity.
Evidence: the present invention can in the time of the structure of simplified apparatus, realize the super planarization in broadband of fiber Raman gain amplifier spectrum, and create condition for dynamic online adjustment gain spectral at the saving cost.
Description of drawings
Fig. 1 fiber Raman amplifier light channel structure figure
The raman gain fiber spectrum of Fig. 2 multi wavelength pumping
(a) the raman gain fiber spectrum of the different wave length pumping of flatness through optimizing
(b) corresponding pumping wavelength and power configuration thereof
Fig. 3 Fabry-Perot chamber FBCSL light channel structure figure
Fig. 4 annular chamber type FBCSL light channel structure figure
The output laser spectrum of Fig. 5 list wavelength pumping FBCSL
(a) output laser spectrum width is with the measured curve of pump power variation
(b) the longitudinal mode spectrum of single wavelength pumping FBCSL output laser
The output laser spectrum of Fig. 6 dual wavelength pumping (1425nm and 1454nm) FBCSL
(a) the FBCSL output laser spectrum of flatness through optimizing
(b) the output laser of dual wavelength pumping FBCSL spectrum is with the measured curve of pump power variation
Fig. 7 adopts dual wavelength pumping (1425nm and 1463nm) FBCSL to make the super smooth raman gain spectrum of pumping source
(a) the output laser of FBCSL spectrum
(b) compose with the raman gain fiber of FBCSL pumping
Embodiment
Described FBCSL adopts the high optical nonlinearity optical fiber (HNL-DSF) that has nearly smooth zero dispersion characteristics at raman laser wavelength place as gain media, can constitute linear pattern Fabry-Perot (F-P) resonant cavity at HNL-DSF optical fiber two termination broadband light reflectors, also can adopt the wavelength division multiplexing wide-band coupler that HNL-DSF optical fiber is linked to be ring resonator.
Fig. 3 is the light channel structure of F-P chamber FBCSL.The F31 end of HNL-DSF links to each other with 312 ends of WDM31 (wideband WDM fiber coupler), 313 ends of WDM31 connect pumping source, and pump light forms gain region by the stimulated Raman scattering in the coupling feed-in HNL-DSF excitation fiber between the 313-312 end of WDM31.The F32 end of HNL-DSF links to each other with 321 ends of 3dBDC32 (coupling ratio is 50% fiber coupler), and 323 ends of 3dBDC32 link to each other with 324 ends and constitute FRR32 (reflectivity is 100% band optical fiber loop speculum); (coupling ratio is the fiber coupler of x for 314 ends of WDM31 and xdBDC33, the x value determines according to best laser output condition) 331 ends link to each other, 333 ends of xdBDC33 link to each other with 334 ends and constitute FRR31 (band optical fiber loop partially reflecting mirror), so, just constitute the full-optical fiber F-P laserresonator by FRR31, HNL-DSF and FRR32,332 ends of xdBDC33 are the laser delivery outlet.According to actual needs, also can in the chamber, add filtering device, so that the bandwidth and the shape of control output laser spectrum.
Fig. 4 is the light channel structure of optic fiber ring-shaped cavity FBCSL.The F41 end of HNL-DSF links to each other with the F42 end by the 412-414 end of WDM41 (wideband WDM fiber coupler), the 401-402 end of ISO (optical isolator), the 431-433 end of xdBDC43 (coupling ratio is the broadband optical fiber coupler of xdB), the 424-422 end of WDM42 (wideband WDM fiber coupler), constitutes the fiber ring laser resonant cavity of clockwise direction (CW) circulation.413 ends of WDM41 link to each other with pumping source, and pump light forms gain region by the stimulated Raman scattering in the coupling feed-in HNL-DSF excitation fiber between the 413-412 end of WDM41.423 ends of WDM42 connect a FRR (reflectivity is 100% optical fiber loop speculum) who is made of 3dBDC44 (coupling ratio is 50% fiber coupler), the residual pump light that spills from HNL-DSF is held coupling luminous fibre annular-type cavity by the 422-423 of WDM42, all return again through the FRR reflection again and excite HNL-DSF in the ring cavity once more, thereby pumping light power is fully used.The laser of CW direction circulation is exported from 434 ends by the coupling between the 431-434 end of xdB DC43 in annular chamber.According to actual needs, can also in the chamber, add filtering device, so that export the bandwidth and the shape of laser spectrum for control.
Described FBCSL utilizes light laser to encourage described high optical nonlinearity fiber resonance cavity and forms excited Raman and swash and to penetrate, utilize the high optical nonlinearity of HNL-DSF to improve pump conversion efficiency, utilize near optical nonlinearity phase modulated and the four wave mixing of HNL-DSF zero-dispersion wavelength to make the sharp spectrum widening of penetrating.
Fig. 5 provides all optical fiber ring cavity FBCSL and is operated in the output spectrum under single wavelength pumping and the relation of pumping light power.Gain medium adopts the HNL-DSF of long 1447m, and the fibre loss coefficient is 1.33dB/km (1425nm) and 0.73dB/km (1550nm), and zero-dispersion wavelength is that (chromatic dispersion gradient is S=0.015ps/nm to 1543.1nm
2/ km), the nonlinear optical fiber coefficient is γ=12.5/W/km.Pumping wavelength is 1425nm, and maximum output gross power is 1.2W.The loss that records 1550nm wavelength place optic fiber ring-shaped cavity is about 4dB, and the output coupling ratio of coupler xdBDC is～70%.As seen from the figure, raman laser centre wavelength is positioned at the 1520nm place, and along with the progressively enhancing of pumping light power, the output raman laser is composed broadening gradually.With the tunable that output laser is 1.2nm by a bandwidth, electricity consumption frequency spectrograph (HP859E) observes it from the beat signal, as shown in Figure 5.As can be seen, FBCSL output light contains extremely many longitudinal modes, and longitudinal mode spacing is 142kHz, and the result who estimates with optic fiber ring-shaped cavity chamber long (1447m) matches.
Described FBCSL can adopt a plurality of wavelength pumpings that raman laser is composed further broadening.Fig. 6 is the raman laser spectrum that all optical fiber ring cavity FBCSL is the most smooth under two wavelength (1425nm and 1454nm) pumping.Pump power is respectively 425mW (1425nm) and 445mW (1454nm), record output laser spectrum ± the 2dB bandwidth is 44nm.
Described FBCSL can realize exporting the regulation and control of laser spectrum shape by the power ratio of adjusting each pumping wavelength.Fig. 7 be under two wavelength (1425nm and 1463nm) pumping annular chamber FSCL output spectrum gradient with the situation of change of pump power proportioning, (a) (b) three kinds of spectral patterns (c) marking corresponding three groups of pump power proportionings respectively.As seen from the figure, can regulate and control the gradient of FSCL output spectrum flexibly by the pump power proportioning of adjusting two wavelength.As increase the pumping wave long number, then can carry out meticulousr adjustment to the flatness of gain spectral.
Described FBCSL of the present invention can be used as the fiber Raman amplifier pumping source and realizes that the Raman of super flat gain spectrum amplifies.Fig. 7 (a) provides dual wavelength as the fiber Raman amplification test, and (Fig. 7 (b) is the L with this wide range laser pumping for 1425nm, 1463nm) the output laser of pumping FBCSL spectrum
+-wave band fiber Raman amplifies the turn off gain spectrum.Pumping light power is respectively 610mW (1425nm) and 400mW (1463nm), and Transmission Fibers is selected 25 kilometers TureWave optical fiber for use.As seen from the figure, the maximum of turn off gain is 3.7dB, and gain spectral ± 0.1dB bandwidth reaches 39nm; If adopt conventional multi wavelength pumping technology, need 4 pumping wavelengths at least for reaching identical gain flatness.
Described FBCSL of the present invention can adopt photonic crystal fiber of new generation (PCF) replacement HNL-DSF that the FBCSL performance is further optimized.In view of the PCF that occurs in recent years can have high optical nonlinearity and dispersion characteristics flexibly, proved that the conventional silica fiber of its optical nonlinearity coefficient ratio is high 500 times, can realize zero dispersion characteristics from 800nm (visible light wave range) to 1500nm (near infrared band).Therefore, adopt PCF grown up in the FBCSL chamber and shorten greatly, pumping light power can reduce significantly, thereby realizes high efficiency miniaturization FBCSL.
Adopt the fiber Raman amplifying technique of discrete multi wavelength pumping to compare with routine, FBCSL of the present invention and being used as The advantage that fiber Raman amplifies is: the first, adopt the FBCSL pumping source of less number of wavelengths can realize super flat gain spectrum Fiber Raman amplify, thereby reduce to contain the deterioration of the dwdm system transmission light signal to noise ratio of FRA; The second, spectrum Bandwidth and spectral pattern are adjustable. Compose shape by the power ratio capable of regulating Output of laser of adjusting the different pumping wavelengths of FBCSL, from And can regulate and control flexibly and effectively flatness and the gradient of FRA raman gain spectrum. Three, service band is flexible. But by wave band and the spectral pattern of choose reasonable FBCSL pumping wave long value and number of wavelengths flexible design Output of laser spectrum, thereby Can carry out to the optical signal of different-waveband and spectrum width fiber Raman amplifies; Four, introduce New-type photon crystal optical fiber (PCF) Technology can realize the miniaturization FBCSL of high pumping conversion efficiency; In addition, simple all optical fibre structure, wide range laser from Produce in the same optical fiber and output, need not complexity and expensive pump combiner spare, the pump light loss is reduced greatly. The miniaturization FBCSL of this low pumping operation not only saves engineering cost, and safe and reliable.
Claims (4)
1, the gain spectrum flattening Wideband Raman amplifies the wide continuous spectrum laser pump source of full optical-fibre adjustable of usefulness, it is characterized in that: it be a kind of employing near the raman laser wavelength, have nearly smooth zero dispersion characteristics high optical nonlinearity optical fiber as gain media, and constitute Fabry-glass sieve chamber full the optical fiber Fabry-glass sieve chamber be adjustable wide continuous spectrum Raman laser at above-mentioned high optical nonlinearity optical fiber two termination broadband light reflectors; Full optical fiber Fabry-glass sieve laserresonator is wherein penetrated the optical delivery fiber passage and is constituted along swashing by band optical fiber loop completely reflecting mirror, high optical nonlinearity optical fiber and band optical fiber loop partially reflecting mirror successively; It contains:
High optical nonlinearity optical fiber;
The pumping source that the heavy pumping laser of a plurality of wavelength constitutes;
The wideband WDM fiber coupler: the pump light that above-mentioned pumping source sends is coupled into to swash by it and penetrates the optical delivery fiber passage and excite coupled above-mentioned high optical nonlinearity optical fiber; Band optical fiber loop completely reflecting mirror: it by the residual pump light of an input optical fibre port and above-mentioned high optical nonlinearity optical fiber spill that port links to each other, two output optical fibre ports directly are connected and help penetrating optical coupling and constitute than the symmetrical fiber coupler that is 50% sharp of light feedback control loop;
Band optical fiber loop partially reflecting mirror: it is penetrated optical coupling and constitutes than the asymmetric optical fiber coupler that is xdB swashing by what an input optical fibre port and above-mentioned wideband WDM fiber coupler sharp penetrated that the transmission line fiber port links to each other, two output optical fibre ports directly connect into part light feedback control loop, the value of x will be according to best laser output condition design, and the part transmission fiber port of above-mentioned asymmetric optical fiber coupler is the delivery outlet of laser.
2, gain spectrum flattening Wideband Raman according to claim 1 amplifies the wide continuous spectrum laser pump source of full optical-fibre adjustable of usefulness, and it is characterized in that: described high optical nonlinearity optical fiber can be the photonic crystal fiber with high optical nonlinearity.
3, the gain spectrum flattening Wideband Raman amplifies the wide continuous spectrum laser pump source of full optical-fibre adjustable of usefulness, it is characterized in that: it be a kind of employing near the raman laser wavelength, have nearly smooth zero dispersion characteristics high optical nonlinearity optical fiber as gain media, and the adjustable wide continuous spectrum Raman laser of all optical fiber ring cavity that with the wideband WDM fiber coupler high optical nonlinearity optical fiber is linked to be ring resonator at high optical nonlinearity optical fiber two ends; It contains:
High optical nonlinearity optical fiber;
The fiber ring laser resonant cavity of clockwise direction circulation: it is by along swashing the first wideband WDM fiber coupler penetrating optical delivery fiber passage clockwise direction and described high optical nonlinearity optical fiber and link to each other successively, optical isolator and penetrating optical coupling and constitute than first broadband optical fiber coupler that is xdB swashing, and the value of x will design according to best laser output condition; The sharp light of penetrating of clockwise direction circulation is by described first broadband optical fiber coupler coupling back output in optic fiber ring-shaped cavity;
The pumping source that the light laser of a plurality of wavelength constitutes: the pump light that it sends is coupled into to swash by the above-mentioned first wideband WDM fiber coupler and penetrates the optical delivery fiber passage and excite coupled above-mentioned high optical nonlinearity optical fiber;
The residual pump light feedback device: the fiber port that residual pump light is derived in the coupling that is serially connected in the second wideband WDM fiber coupler in the optic fiber ring-shaped cavity and an input optical fibre port and the described second wideband WDM fiber coupler that it spills by the residual pump light with above-mentioned high optical nonlinearity optical fiber that port links to each other links to each other, two output optical fibre ports directly connect into the loop completely reflecting mirror to the pump light coupling ratio is that 50% second fiber coupler constitutes.
4, gain spectrum flattening Wideband Raman according to claim 3 amplifies the wide continuous spectrum laser pump source of full optical-fibre adjustable of usefulness, and it is characterized in that: described high optical nonlinearity optical fiber can be the photonic crystal fiber with high optical nonlinearity.
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| CN100424543C (en) * | 2005-05-11 | 2008-10-08 | 南京邮电学院 | Crystal optical fiber solition type full light regenerator and its light signal regenerating method |
| CN100410799C (en) * | 2006-07-17 | 2008-08-13 | 武汉光迅科技股份有限公司 | Efficient circulating filling-in clad pumping optical fiber amplifier |
| JP5251902B2 (en) * | 2010-03-02 | 2013-07-31 | オムロン株式会社 | Laser processing equipment |
| CN101908709A (en) * | 2010-07-26 | 2010-12-08 | 西南交通大学 | Multi-wavelength Brillouin erbium-doped fiber laser with annular cavity based on Taiji structure |
| CN103048305A (en) * | 2012-12-07 | 2013-04-17 | 中国科学院西安光学精密机械研究所 | All-fiber laser Raman testing device |
| CN103364106B (en) * | 2013-07-16 | 2015-07-29 | 扬州森斯光电科技有限公司 | A kind of Brillouin optical time domain analysis sensor-based system based on the pumping of overlength loop laser |
| CN104535007A (en) * | 2014-12-15 | 2015-04-22 | 哈尔滨工程大学 | Distributed type optical fiber strain measurement system based on cavity-length-adjustable F-P white light interference demodulating device |
| CN104618013B (en) * | 2015-01-26 | 2017-08-11 | 电子科技大学 | A kind of related optical time domain reflectometer based on all -fiber wide range chaos light source |
| CN107425406B (en) * | 2017-07-18 | 2023-08-18 | 无锡科技职业学院 | Pump source of third-order Raman amplifier |
| CN108107074B (en) * | 2017-12-20 | 2021-05-11 | 清华大学 | Double-pulse flash Raman method and system for representing thermophysical properties of two-dimensional nano material |
| CN108683063B (en) * | 2018-05-24 | 2021-02-09 | 中国工程物理研究院应用电子学研究所 | Diode direct pumping Raman fiber laser and spectrum synthesis method thereof |
| CN110600982A (en) * | 2019-08-14 | 2019-12-20 | 武汉光迅科技股份有限公司 | Remote pumping system capable of improving pumping fiber-entering power |
| CN112421352B (en) * | 2020-10-12 | 2022-09-13 | 武汉光谷航天三江激光产业技术研究院有限公司 | Optical parameter conversion device for realizing ultra-wide spectrum laser output |
| CN114499667B (en) * | 2022-01-28 | 2023-06-13 | 上海交通大学 | Device and method for optimizing gain of bidirectional optical amplifier in single-fiber bidirectional optical fiber link |
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