CN102540623A - Scheme and device for increasing gain of optical fiber parametric amplifier by adopting phase-shifting grating - Google Patents

Abstract

The invention discloses a scheme and a device for increasing gain of an optical fiber parametric amplifier by adopting a phase-shifting grating, which comprise external cavity lasers, phase modulators, erbium-doped fiber amplifiers, polarization controllers, couplers, the phase-shifting grating, high-nonlinearity optical fibers and optical spectrum analyzers, and are characterized in that when the interval between the wavelength of pump light and the optical fiber zero dispersion wavelength is in a larger range, the phase-shifting grating is introduced between the two high-nonlinearity optical fibers to serve as a filter and a phase shifter to reflect and perform phase shifting for idling frequency, so that phase mismatch in an optical fiber parametric process is compensated, and the gain of the optical fiber parametric amplifier is increased. High parametric amplification is realized by introducing the phase-shifting grating, the gain of the optical fiber parametric amplifier is increased, and development of the all-optical amplification technology in an optical communication system is benefited.

Description

Adopt phase-shifted grating to improve the scheme and the device of optical fiber parameter amplifier gain

Technical field

The present invention relates to a kind of high-gain optical fiber parameter amplifier, especially a kind of phase-shifted grating that adopts is realized the optical fiber parameter amplifier that gain improves, and is applicable to optical fiber communication and nonlinear optical fiber optical field.

Background technology

Along with professional the increasing of internet data, optical fiber communication becomes the trunk of present communication network because of characteristics such as its broadband, low-loss, anti-electromagnetic interference (EMI), and can realize that the image intensifer of full light signal amplification technology is one of important devices in the optical fiber telecommunications system.Wherein, Optical fiber parameter amplifier is because have the ability that high gain-bandwidth, high-gain level, saturation output power, high phase-sensitive nature and any wavelength signals of multichannel are amplified simultaneously; Receive increasing concern, be considered to be fit in the following dense wavelength division multiplexing system the full Optical Amplification Technology of tool future.Improve the important indicator that gain is the research amplifier, therefore, the gain that research improves optical fiber parameter amplifier becomes extremely attractive focus.

With regard to present progress, mainly be through letting the pump light wavelength be operated near the zero-dispersion wavelength of optical fiber and adopting several sections highly nonlinear optical fiber cascades to realize the gain that modes such as dispersion compensation improve optical fiber parameter amplifier.But, based on optical fiber telecommunications system in requisition for, hope that also the pump light wavelength is operated in the zero-dispersion wavelength away from optical fiber, the same raising that realizes gain in a big relatively wave-length coverage.

Summary of the invention

Seeing that the deficiency of the prior art of above statement; The objective of the invention is to propose a kind of scheme and device that adopts phase-shifted grating to improve the optical fiber parameter amplifier gain; Be spaced apart under the big relatively wavelength coverage at pump light wavelength and zero-dispersion wavelength of fiber, adopt phase-shifted grating to be inserted in the raising that realizes the optical fiber parameter amplifier gain between two sections highly nonlinear optical fibers.

The objective of the invention is to realize through following means.

Adopt phase-shifted grating to improve the scheme and the device of optical fiber parameter amplifier gain, form by outside cavity gas laser, phase-modulator, Erbium-Doped Fiber Amplifier (EDFA), Polarization Controller, coupling mechanism, phase-shifted grating, highly nonlinear optical fiber and spectroanalysis instrument; Comprise following treatment step: the pump light Pump2 that pump light Pump1 that outside cavity gas laser ECL1 produces and outside cavity gas laser ECL2 produce amplifies through phase-modulator PM1 and PM2 modulation, Erbium-Doped Fiber Amplifier (EDFA) EDFA1 and EDFA2 respectively successively; And behind Polarization Controller PC1 and its polarization state of PC2 adjustment; Be coupled through coupling mechanism OC1; Flashlight Signal with the outside cavity gas laser ECL3 generation of adjusting through Polarization Controller PC3 is coupled into coupling mechanism OC2 together; Right latter two pump light and flashlight get into highly nonlinear optical fiber HNLF1 simultaneously; Realize the generation and the amplification of flashlight of ideler frequency light through the parametric process in the highly nonlinear optical fiber, then four light waves get into phase-shifted grating PS-FBG simultaneously, through phase-shifted grating to the part filtering of ideler frequency light and the phase matching of phase shift realization parametric process; Realize amplification again after getting into highly nonlinear optical fiber HNLF2 again, utilize spectroanalysis instrument OSA1 and OSA2 to measure the variation of corresponding power flashlight.The phase-shifted grating compensation of phase mismatch that the present invention adopts has realized the raising of optical fiber parameter amplifier gain.

After design as above; Utilize a phase-shifted grating reflecting part ideler frequency light and ideler frequency light is produced respective phase-shifted; Adjusted the phase mismatch parameter between two pump lights, flashlight and the ideler frequency light; And then compensated the phase mismatch in first section Fiber-optic parametric process, improved the gain of optical fiber parameter amplifier and improved the energy conversion efficiency of pump light simultaneously to flashlight.The present invention has following advantage: the phase-shifted grating that only needs to select according to the needs of reflectivity and phase shift corresponding grating length and relative index of refraction; Just can improve the gain of optical fiber parameter amplifier effectively; This programme and device are simple to be realized easily, has improved the energy conversion efficiency and the system flexibility of optical fiber parameter amplifier.

Description of drawings is following:

Fig. 1 is the present invention program's a system chart.

Fig. 2 is the structural representation of phase-shifted grating, and wherein Λ is the grating cycle, and phase shift is phase shift.

(a) reflectance spectrum of phase-shifted grating and (b) phase shift synoptic diagram when Fig. 3 is the π phase shift.

Fig. 4 is the synoptic diagram that the power of two pump lights, ideler frequency light and flashlight changes with fiber lengths, and wherein solid line is for introducing phase-shifted grating, and dotted line is for no phase-shifted grating.

Fig. 5 inserts the synoptic diagram that concerns of loss and flashlight gain for grating.

Fig. 6 is that the flashlight gain concerns synoptic diagram with what fiber lengths changed, and wherein solid line is for introducing phase-shifted grating, and dotted line is for no phase-shifted grating.

Embodiment

Below in conjunction with accompanying drawing enforcement of the present invention is done further to describe.

As shown in Figure 1, the present invention program and device are made up of outside cavity gas laser ECL, phase-modulator PM, Erbium-Doped Fiber Amplifier (EDFA) EDFA, Polarization Controller PC, coupling mechanism OC, phase-shifted grating PS-FBG, highly nonlinear optical fiber HNLF and spectroanalysis instrument OSA.Phase-shifted grating is little because of its volume, cost is low and insert the aspects such as narrow-band filtering, wavelength-division multiplex/demultiplexing, phase shift control and Er-doped fiber flat gain of advantage in optical fiber communication and sensory field such as loss is low has wide application prospect.

In Fig. 1, the wavelength X that outside cavity gas laser ECL1 produces _P1The pump light Pump1 of=1480nm is with the wavelength X of ECL2 generation _P2The pump light Pump2 of=1620nm, respectively through being coupled into coupling mechanism OC1 behind phase-modulator, Erbium-Doped Fiber Amplifier (EDFA) and the Polarization Controller, the wavelength X that produces with another road outside cavity gas laser ECL3 again _sThe flashlight Signal of=1520nm is coupled into coupling mechanism OC2 together, is 60m zero-dispersion wavelength λ at first section fiber lengths ₀The four-wave mixing effect takes place among the highly nonlinear optical fiber HNLF1 of=1550nm, and the generation wavelength is λ _iIdeler frequency light Idler, simultaneously flashlight is amplified.Angular frequency in the Fiber-optic parametric amplification process between two pump light, flashlight and ideler frequency light satisfies ω _P1+ ω _P2=ω _s+ ω _iCondition.Fiber distance is not more considered its loss, and under the situation of each optical polarization retention wire polarization continuous light, the coupling mode equations below the complex amplitude change procedure between four light waves satisfies:

$\frac{d{A}_{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HSA00000674588400013.png,HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}1}}{\mathrm{dz}}=\mathrm{i\&gamma;}[({\left|A_{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HSA00000674588400013.png,HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}1}\right|}^2+2({\left|A_{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}2}\right|}^2+{\left|A_s\right|}^2+{\left|A_i\right|}^2))A_{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HSA00000674588400013.png,HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}1}+2A_{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}2}*A_s{A}_i{e}^{\mathrm{i\&Delta;\&beta;z}}]---\left(1\right)$

$\frac{d{A}_{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}2}}{\mathrm{dz}}=\mathrm{i\&gamma;}[({\left|A_{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}2}\right|}^2+2({\left|A_{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HSA00000674588400013.png,HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}1}\right|}^2+{\left|A_s\right|}^2+{\left|A_i\right|}^2))A_{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}2}+2A_{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HSA00000674588400013.png,HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}1}*A_s{A}_i{e}^{\mathrm{i\&Delta;\&beta;z}}]---\left(2\right)$

$\frac{d{A}_s}{\mathrm{dz}}=\mathrm{i\&gamma;}[({\left|A_s\right|}^2+2({\left|A_{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HSA00000674588400013.png,HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}1}\right|}^2+{\left|A_{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}2}\right|}^2+{\left|A_i\right|}^2))A_s+2A_i*A_{p1}{A}_{p2}{e}^{-\mathrm{i\&Delta;\&beta;z}}]---\left(3\right)$

$\frac{d{A}_i}{\mathrm{dz}}=\mathrm{i\&gamma;}[({\left|A_i\right|}^2+2({\left|A_{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HSA00000674588400013.png,HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}1}\right|}^2+{\left|A_{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HSA00000674588400021.png"\; state="\{\{state\}\}">p</figure-callout>}2}\right|}^2+{\left|A_s\right|}^2))A_i+2A_s*A_{p1}{A}_{p2}{e}^{-\mathrm{i\&Delta;\&beta;z}}]---\left(4\right)$

A wherein _P1, A _P2, A _sAnd A _iBe respectively the complex amplitude of two pump lights, flashlight and ideler frequency light, γ is the nonlinear factor of highly nonlinear optical fiber, and Δ β is linear wave vector mismatching.

Connect a phase-shifted grating at the HNLF1 output terminal; The structure of phase-shifted grating is as shown in Figure 2; Wherein Λ is the grating cycle; Parameters such as length and relative index of refraction through the adjustment phase-shifted grating obtain different reflection coefficients and phase shift, are made as Prague phase shift wavelength of grating to the ideler frequency light wavelength as the phase-shifted grating of wave filter and phase-shifter, and purpose is to reduce the power and the generation respective phase-shifted of ideler frequency light.In Fig. 3, be that the ideler frequency reflection of light rate at 1574.6nm place is 0.7 at wavelength, mean and have only about 30% ideler frequency light, and produce the phase shift of π in ideler frequency light wave strong point through phase-shifted grating.But the light of other three wavelength does not have the phase-shifted grating that passes through of reflection and extra phase shift simultaneously.Phase-shifted grating in this programme is as wave filter and phase-shifter, changed the relative phase difference between four light waves, and then realized phase matching.

Four light waves through the phase mismatch compensation continue to carry out the parameter amplification through second section highly nonlinear optical fiber then, have realized the further amplification of signal light power, the gain that has improved optical fiber parameter amplifier.Wherein highly nonlinear optical fiber HNLF2 and HNLF1 are except fiber lengths is different, and all the other optical fiber parameter character are all consistent, and the length of HNLF2 is 36m in this scheme.Fig. 4 has explained the relation of the power of pump light 1, pump light 2, ideler frequency light and flashlight when whether introducing phase-shifted grating with two sections highly nonlinear optical fiber length variations.Can find out power input all be two pump lights of 2W and flashlight that power input is 1mW through behind the HNLF1, through the parameter amplification process, the energy of two pump lights can be to flashlight and the transfer of ideler frequency light; The minimum 1.24W that is reduced to of power of two pump lights at fiber lengths 60m place; The power maximum of flashlight is amplified to 0.75W, if there is not the introducing of phase-shifted grating, along with the increase of fiber lengths; Previous pump light changes to the energy shift direction of flashlight; Then the power of flashlight does not continue to amplify, and continues lessly to approaching 0 on the contrary, and the power of pump light increases to gradually and approaches power input simultaneously; Obviously, this moment is very little for the amplification of flashlight.If but after having introduced phase-shifted grating; At fiber lengths 60m place, because phase-shifted grating is to the effect of ideler frequency reflection of light, the power of ideler frequency light reduces to 0.22W from 0.75W shown in Fig. 4 (c); And produce the phase shift of π, and then the phase mismatch in the parametric process is played compensating action.In the case, shown in Fig. 4 (d), along with the increase of fiber lengths; The power of flashlight continues to increase, and reaches 1.98W at the output terminal of HNLF2, simultaneously like Fig. 4 (a) with (b); The power of two pump lights reduces near 0, and pump light significantly improves to the energy conversion efficiency of flashlight.Simultaneously, find out in gain Fig. 5 with the fiber lengths variation of flashlight that being compared to does not have phase-shifted grating to introduce, the maximum gain of flashlight has improved 4.3dB, and output gain has improved 18.1dB.In brief, the introducing of phase-shifted grating has significantly improved the gain of optical fiber parameter amplifier.

On the other hand, when considering the junction loss of phase-shifted grating and highly nonlinear optical fiber, introduce the influence of phase-shifted grating to the optical fiber parameter amplifier gain; In Fig. 6, see; Through the introducing of phase-shifted grating, even the insertion loss at each tie point place is 1dB, the gain of flashlight has still improved 1.7dB; And generally speaking, the insertion loss at each tie point place is less than 0.5dB.In real system, the introducing of phase-shifted grating still can significantly improve the gain of optical fiber parameter amplifier obviously.

Comprehensive above statement, the present invention has following characteristic: 1). in two sections highly nonlinear optical fibers of Fiber-optic parametric amplification system, introduced phase-shifted grating; 2). utilize phase-shifted grating to filtering of ideler frequency light and phase shift, compensated the phase mismatch in the Fiber-optic parametric process, improve the gain of optical fiber parameter amplifier; 3). through selecting the reflectivity and the phase shift of phase-shifted grating, in tunable range, realize the raising of optical fiber parameter amplifier gain under the different condition.Help optimizing the characteristic of optical fiber parameter amplifier, for the full Optical Amplification Technology of dense wave division multipurpose optical communication system provides new scheme.

It is above that what state only is the preferred implementation of the present invention program and device; Should be understood that; Under the prerequisite that does not break away from the present invention program and device essence; In reality is implemented, can make some changes (such as the power input that changes pump light and flashlight with wavelength time, when the reflectivity of change phase-shifted grating and phase shift, when the nonlinear factor of change highly nonlinear optical fiber and fiber lengths) also should be included in protection scope of the present invention.

Claims (3)

1. adopt phase-shifted grating to improve the scheme and the device of optical fiber parameter amplifier gain; Constitute by outside cavity gas laser ECL, phase-modulator PM, Erbium-Doped Fiber Amplifier (EDFA) EDFA, Polarization Controller PC, coupling mechanism OC, phase-shifted grating PS-FBG, highly nonlinear optical fiber HNLF and spectroanalysis instrument OSA; It is characterized in that the pump light Pump1 of outside cavity gas laser ECL1 generation and the pump light Pump2 that outside cavity gas laser ECL2 produces amplify through phase-modulator PM1 and PM2 modulation, Erbium-Doped Fiber Amplifier (EDFA) EDFA1 and EDFA2 respectively successively; And behind Polarization Controller PC1 and its polarization state of PC2 adjustment; Be coupled through coupling mechanism OC1; And be coupled into coupling mechanism OC2 with flashlight Signal that outside cavity gas laser ECL3 through Polarization Controller PC3 adjustment produces; Right latter two pump light and flashlight get into highly nonlinear optical fiber HNLF1 simultaneously; Realize the generation of ideler frequency light and the amplification of flashlight through the parametric process in the optical fiber, then four light waves get into phase-shifted grating PS-FBG simultaneously, through part filtering and the phase shift realization phase matching of phase-shifted grating to ideler frequency light; Realize amplification again after getting into highly nonlinear optical fiber HNLF2 again, utilize spectroanalysis instrument OSA1 and OSA2 to measure the variation of corresponding power flashlight.The phase-shifted grating that the present invention adopts carries out the raising that the phase mismatch compensation has realized the optical fiber parameter amplifier gain.

2. employing phase-shifted grating according to claim 1 improves the scheme and the device of optical fiber parameter amplifier gain; It is characterized in that; Between two sections highly nonlinear optical fibers, introduce phase-shifted grating and ideler frequency light is produced reflection and phase shift, compensated the phase mismatch in the Fiber-optic parametric process as wave filter and phase-shifter.And, in tunable range, realize the raising of optical fiber parameter amplifier gain under the different condition through selecting the reflectivity and the phase shift of phase-shifted grating.

3. improve the scheme and the device of optical fiber parameter amplifier gain based on the described employing phase-shifted grating of claim 1; It is characterized in that, in the raising of this optical fiber parameter amplifier gain is equally applicable to the pump light wavelength and zero-dispersion wavelength of fiber is spaced apart a relative wide wave-length coverage.

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