CN104993872A - Raman fiber amplifier gain compensation and transient control method - Google Patents

Abstract

The invention relates to a Raman fiber amplifier gain compensation and transient control method. According to the Raman fiber amplifier gain compensation and transient control method, a pump laser set in a Raman fiber amplifier works in a constant power mode, and when the pump laser set is in a locked output power state, the change in input power or output power of the Raman fiber amplifier is determined, and the power of the pump laser set is adjusted according to the change in input power or output power in order to enable the change in power of the pump laser set and the change in input power or output power to meet the formula deltaPp=k*deltaPtotal, wherein deltaPp is the change in power of the pump laser set and the unit is mw, deltaPtotal is the change in input power or output power and the unit is mw, and k is correction slope. For a Raman fiber amplifier of which the pump laser set works in a constant power mode, when the input optical power changes in a large range, forward, backward and two-way Raman amplifier gain compensation can be realized.

Description

Raman Fiber Amplifier gain compensation and transient control methods

Technical field

The present invention relates to a kind of method, be a kind of Raman Fiber Amplifier gain compensation and transient control methods, belong to the technical field of optical communication.

Background technology

Raman Fiber Amplifier (RFA:Raman Fiber Amplifier) due to noise figure low, with erbium-doped fiber amplifier (EDFA:Erbium-doped Optical Fiber Amplifier) with the use of, Optical Signal To Noise Ratio (OSNR:Optical Signal Noise Ratio) can be optimized, reduce the error rate, increase transmission range, be widely used at present in long distance optical communication transmission system.

For a certain pumping wavelength, the small-signal turn off gain of RFA can be represented by formula (1):

$G_{\mathrm{on}/\mathrm{off}}=\exp \left(g_R\frac{P_p}{A_{\mathrm{eff}}}\frac{L_{\mathrm{eff}}}{K}\right)---\left(1\right)$

Wherein, g _rfor optical fiber Raman gain coefficienct; A _efffor optical fiber effective area; P _pfor entering fine pump power; K is polarization factor; L _efffor optical fiber effective length, be defined as L _eff=1-exp (-α _pl)/α _p; α _pfor pump light attenuation coefficient in a fiber; L is fiber lengths, and small-signal refers to that signal power is little of affecting pump power distribution in a fiber.

RFA input power is in the past very little, and RFA is operated in low level signal amplification district, can be found out by formula (1), as long as now enter fine pump power P _pconstant can realize permanent gain control.But along with increasing of transmission system medium wavelength number, input power also increases thereupon, causes RFA operation interval beyond low level signal amplification district, now once input power changes, permanent pump power mode of operation cannot ensure that permanent gain controls, and now needs to carry out corresponding compensation to gain.

The gain media of RFA is Transmission Fibers itself, its length is longer (even the RFA of discrete, its gain fibre length is substantially also at more than 5km), therefore only have a power monitor in RFA module, therefore the gain control method of EDFA (carrying out gain control by the monitoring result of input and output monitor) cannot be adopted to carry out gain compensation and transient control.

What publication number was that CN102307068A file describes is method by carrying out Raman gain locking with outer ASE, but this patent only considers the mathematical relationship of Raman gain and ASE, do not consider the impact of input power, therefore this patent is suitable only for the RFA that input optical power remains unchanged.

Publication number is CN200510067689.0 file when mainly describing input optical power change, the method for Raman gain adjustment, but is realized by two power monitors, is unpractical in actual transmissions system; And be change minimal wave length pump power to realize gain compensation in patent, overall gain now can be kept constant, but flat gain, gain slope can change, and may occur error code at signal receiving end.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, a kind of Raman Fiber Amplifier gain compensation and transient control methods are provided, it works in the RFA of constant power-mode to pump laser group, when input optical power wide variation, the gain compensation of forward, backward, two-way raman amplifier can be realized.

According to technical scheme provided by the invention, described Raman Fiber Amplifier gain compensation and transient control methods, pump laser group in Raman Fiber Amplifier work in constant power-mode and described pump laser group is under locking power output state time, determine input power or the power output variable quantity of described Raman Fiber Amplifier, and the power of variable quantity adjustment pump laser group according to input power or power output, meet Δ P to make the power variation of pump laser group and input power or power output variable quantity _p=k* Δ Ptotal, wherein, Δ P _pfor the power variation of pump laser group, unit mw; Δ Ptotal is the variable quantity of input power or power output, unit mw; K is calibration slopes.

Described Raman Fiber Amplifier is forward direction Raman Fiber Amplifier, backward Raman Fiber Amplifier or two-way Raman Fiber Amplifier.

Described pump laser group comprises some pump lasers, calibrates each pump laser in pump laser group, to determine the calibration slopes k corresponding to each pump laser _i, i=1,2 ... n, n are the quantity of pump laser in pump laser group.

To pump laser group inside-pumping laser calibration slopes k _icalibration comprise the steps:

Step 1, closedown pump laser group, access testing light source, adjustment attenuator makes input light be a fixed value, and by spectroanalysis instrument scanning Raman Fiber Amplifier output spectrum;

Step 2, open and adjust pump laser group, by the output spectrum of spectroanalysis instrument scanning Raman Fiber Amplifier, meeting the demands to make Raman Fiber Amplifier parameter;

The pump power of each pump laser, the input power of Raman Fiber Amplifier or power output in step 3, record pump laser group;

Step 4, repetition above-mentioned steps, to obtain organizing calibration data set, all comprise the pump power of each pump laser in pump laser group, the input power of Raman Fiber Amplifier or power output in described many group calibration data set more;

Step 5, basis many groups calibration data carry out matching, to obtain the calibration slopes k of each pump laser _i, i=1,2 ... n.

When many groups calibration data carries out matching, adopt linear fit or multistage curve.

Advantage of the present invention:

1, the present invention can be applicable to forward direction, reverse and two-way Raman Fiber Amplifier, is widely used.

2, calibration value involved in the present invention only has one, namely only needs to obtain calibration slopes, and calibration and control method simply, are implemented convenient and reliable.

3, the present invention and light path design scheme have nothing to do, and for designing Raman Fiber Amplifier that is complete or that applying, by upgrading Firmware (increasing calibration slopes k), can realize Raman gain and compensating and transient control.

Accompanying drawing explanation

Fig. 1 is the structural representation of Raman Fiber Amplifier of the present invention.

The emulation schematic diagram that Fig. 2 ~ Fig. 6 is the Raman gain of the present invention's reverse Raman Fiber Amplifier when being 12dB, wherein:

Fig. 2 is the relation schematic diagram of output signal power of the present invention and pump power, comprises linear fit result, and wherein output signal power unit is mw, and pump power unit is mw.

Fig. 3 is the relation schematic diagram of output signal power of the present invention and pump power, and wherein output signal power unit is dBm, and pump power unit is mw.

Fig. 4 is the relation schematic diagram that the present invention exports gross power and pump power, comprises linear fit result, and wherein exporting gross power unit is mw, and pump power unit is mw.

Fig. 5 is the relation schematic diagram that the present invention exports gross power and pump power, and wherein exporting gross power unit is dBm, and pump power unit is mw.

Fig. 6 is output power signal of the present invention, the comparison diagram exporting gross power and pump power.

Description of reference numerals: 1-Transmission Fibers, 2-pump signal wave multiplexer, 3-light splitting coupler, 4-pump laser group, 5-power monitor and 6-control unit.

Embodiment

Below in conjunction with concrete drawings and Examples, the invention will be further described.

As shown in Figure 1: RFA pump laser group being worked in constant power-mode, when input optical power wide variation, in order to realize forward direction, backward, the gain compensation of two-way raman amplifier, Raman Fiber Amplifier gain compensation of the present invention and transient control methods are specially: the pump laser group in Raman Fiber Amplifier work in constant power-mode and described pump laser group is under locking power output state time, determine input power or the power output variable quantity of described Raman Fiber Amplifier, and the power of variable quantity adjustment pump laser group according to input power or power output, Δ P is met to make the power variation of pump laser group and input power or power output variable quantity _p=k* Δ Ptotal, wherein, Δ P _pfor the power variation of pump laser group, unit mw, Δ Ptotal is the variable quantity of input power or power output, unit mw, k is calibration slopes.

Particularly, when Raman Fiber Amplifier is operated in permanent gain, permanent gain slope, between the pump power of arbitrary wavelength and input signal power or output signal power, there is following relation:

P _P＝f(Psig) (2)

By analogue simulation and experiment, formula (2) can be reduced to first order linear relation, is specially:

P _P＝k*Psig+c (3)

Wherein, P _pfor pump power, unit mw; Psig is input signal power or output signal power, unit mw, and for Fig. 1 (A), Psig is input signal power, and for Fig. 1 (B), Psig is output signal power; K is calibration slopes, and c is for correcting intercept.

Formula (3) is variable to be changed to:

ΔP _P＝k*ΔPsig (4)

Wherein, Δ P _pfor pump power variable quantity, unit mw; Δ Psig is signal power variations amount, unit mw; K is calibration slopes.

RFA, while amplifying optical signals, can produce certain noise power, and this noise power is generally referred to as ASE (Amplified Spontaneous Emission) power.The available formula of relation (5) between gross power, signal power, ASE power represents:

Ptotal＝Psig+Pase (5)

Wherein, Ptotal is gross power, by power monitor 5 direct detection, and unit mw; Psig is signal power, unit mw; Pase is the ASE power under this condition, unit mw.

For Fig. 1 (A), Ptotal is input general power, Psig is input signal power, because power monitor 5 is positioned at before RFA, ASE power does not affect input power detection monitoring, therefore can think that Pase is 0, power monitor 5 probe power are input general power, namely equal input signal power.For Fig. 1 (B), power monitor 5 is positioned at RFA rear end, and ASE power influences power output is monitored, and the power that power monitor 5 detects, for exporting gross power, comprises output signal power, ASE power.

When gain remains unchanged, Pase remains unchanged, and now formula (5) being substituted into formula (3) abbreviation can obtain:

ΔP _P＝k*ΔPtotal (6)

Wherein, Δ P _pfor pump power variable quantity, unit mw; Δ Ptotal for inputing or outputing gross power variable quantity, unit mw; K is calibration slopes.

Based on above-mentioned analysis, the Raman gain that the present invention proposes compensates and transient control methods is: input power or the power output variable quantity of being determined described Raman Fiber Amplifier by power monitor 5, and the power of variable quantity adjustment pump laser group according to input power or power output, meet Δ P to make the power variation of pump laser group and input power or power output variable quantity _p=k* Δ Ptotal.In the embodiment of the present invention, described Raman Fiber Amplifier is forward direction Raman Fiber Amplifier, backward Raman Fiber Amplifier or two-way Raman Fiber Amplifier.In the specific implementation, to reverse RFA, the power output variable quantity for Raman Fiber Amplifier determined, and for forward direction RFA, the input power variable quantity for Raman Fiber Amplifier then determined, namely determine that variable quantity or the power output variable quantity of input power are relevant with the type of Raman Fiber Amplifier, concrete condition, known by the art personnel, no longer describes in detail herein.

The schematic diagram that Fig. 1 (A) is forward direction RFA, the schematic diagram that Fig. 1 (B) is reverse RFA, the schematic diagram that Fig. 1 (C) is two-way RFA.For Fig. 1 (B) oppositely RFA, flashlight enters into RFA module through Transmission Fibers 1, and RFA comprises pump signal wave multiplexer 2, light splitting coupler 3, pump laser group 4, power monitor 5 and control unit 6.Transmission Fibers 1 is connected with the common port of pump signal wave multiplexer 2, and the output of pump laser group 4 is connected with the reflection end of pump signal wave multiplexer 2, and the transmission end of pump signal wave multiplexer 2 is connected with the common port of light splitting coupler 3; The auxiliary light splitting end (being generally little light splitting end) of light splitting coupler 3 is connected with power monitor 5, the output that the main light splitting end (being generally large light splitting end) of light splitting coupler 3 is RFA module; The power output variable quantity that control unit 6 detects according to power monitor 5, the power of adjustment pump laser group 4, make the relation between the power variation of pump laser group 4 and the variable quantity of power output trend towards meeting formula (6), namely think that control completes.In the embodiment of the present invention, the concrete enforcement structure of pump signal wave multiplexer 2, light splitting coupler 3, pump laser group 4, power monitor 5 and control unit 6 all adopts version conventional in the art, be specially known by the art personnel, repeat no more herein.

Particularly, carry out analogue simulation to reverse RFA when keeping gain to be 12dB, simulation result is (figure only represents single pump power) as shown in Fig. 2 ~ Fig. 6.Wherein, Fig. 2, Fig. 3 represent the graph of a relation between output signal power and pump power; Fig. 4, Fig. 5 represent the graph of a relation between gross output (comprising ASE power) and pump power.Can be drawn a conclusion by simulation result:

1), from Fig. 2, Fig. 4, the linearity of matching is greater than 99%, namely all tends to meet formula (3) between pump power and output signal power, power output.

2), as can be seen from Figure 3, when the output signal power of RFA is less than-10dBm, P _psubstantially remain unchanged, namely RFA is operated in the low level signal amplification interval described by formula (1), and now permanent gain mode is equal to permanent pump power pattern.

3), from Fig. 4, Fig. 6, ASE power can be ignored the impact of fitting result, and calibration slopes k value remains unchanged, and namely formula (4) is identical with the calibration slopes k in formula (6).

Known by above-mentioned explanation, formula (3), formula (4), formula (6) be set up, namely the present invention propose Raman gain compensate and transient control methods be also set up.

If total n pump laser (pump in pump laser group 4 in RFA ₁, pump ₂pump _n), its power is respectively with P _p1p _pnrepresent, then each pump laser all has a corresponding calibration slopes value, i.e. k ₁, k ₂k _n; The probe power of power monitor 5 represents with Ptotal.Equipment required for parametric calibration comprises OSA (Optical SpectrumAnalyzer, spectroanalysis instrument), PM (Power Meter, power meter), ATT (Attenuator, attenuator), then for Fig. 1 (B), as follows to the calibration steps of calibration slopes corresponding to pump laser group 4:

Step 1, closedown pump laser group, access testing light source, adjustment attenuator makes input light be a fixed value, and by spectroanalysis instrument scanning FRA output spectrum;

Step 2, open and adjust pump laser group, by the output spectrum of spectroanalysis instrument scanning RFA, meeting the demands to make the parameter of RFA; Described parameter comprises gain, flat gain and gain slope.

The pump power of each pump laser, the power output of RFA in step 3, record pump laser group; Pump laser itself, with power monitor, can directly be obtained its pump power values, be obtained the power output of FRA by power monitor 5, namely obtains the calibration data Ptotal of first group ₁, P ¹ _p1p ¹ _pn;

Step 4, by adjustment attenuator make input light be different fixed values, repeat above-mentioned steps, to obtain organizing calibration data set, in described many group calibration data set, all comprise the pump power of each pump laser in pump laser group, the power output of RFA, i.e. Ptotal more ₂, P ² _p1p ² _pn; Ptotal ₃, P ³ _p1p ³ _pn; Ptotal _m, P ^m _p1p ^m _pn; Wherein, n represents the quantity of pump laser, and m represents calibration data set number, wherein n>=1, m>=2.

Step 5, basis many groups calibration data carry out linear fit, to obtain the calibration slopes k of each pump laser _i, i=1,2 ... n.

When carrying out linear fit, with Ptotal ₁ptotal _mfor abscissa, with (P ¹ _p1p ¹ _pn..., P ^m _p1p ^m _pn) be ordinate, adopt formula (3) to carry out linear fit respectively, obtain k _i, i=1,2 ... n is also saved in control unit 6, namely according to k _i, i=1,2 ... n obtains the calibration slopes k corresponding to each pumping, and control unit 6 can regulate the pump power of pump laser group 4 according to calibration slopes k.Especially, for improving control precision, described approximating method can change to multistage curve.In addition, in RFA, pumping actual power normally carries out distinguishing according to pumping wavelength, and namely the pump laser of phase co-wavelength is summed up as same pump laser.Therefore in actual alignment matching, can carry out bank calibration according to the pumping wavelength in pump laser group, obtain calibration slopes corresponding to each pumping wavelength for gain compensation and transient control, calibration steps remains unchanged.

Gain compensation and transient control implementation method: when after RFA working stability, according to the real-time detection total power value Ptotal of power detector 5, calculate power variation (Δ Ptotal), call calibration slopes k, calculated the power variation of each pump laser by formula (6): Δ P _p1Δ P _pn, according to Δ P _p1Δ P _pnadjust the performance number of each pump laser and lock, gain compensation completes.Control mode can be divided into software-controlled manner, hardware controls mode.Software mode is realized by firmware (firmware), calls calibration slopes k, makes pump power variable quantity and input or output power variation to tend to meet formula (6), and in general regulation time is slightly long.Hardware mode is realized by feedback circuit, according to calibration slopes k, configure circuit parameter, make pump power variable quantity and input or output power variation to tend to meet formula (6), regulation time extremely short (musec order), easily realizes transient control.Be implemented as known by the art personnel, repeat no more herein.

The present invention has described gain compensation and the transient control methods of Raman Fiber Amplifier in detail, and provides parameter calibrating method, and those skilled in the art should be understood that.Not deviating from the scope of the invention, its form and details can make various change, these changes all will drop in the scope of the present invention.

Claims (5)

1. a Raman Fiber Amplifier gain compensation and transient control methods, it is characterized in that: the pump laser group in Raman Fiber Amplifier work in constant power-mode and described pump laser group is under locking power output state time, determine input power or the power output variable quantity of described Raman Fiber Amplifier, and the power of variable quantity adjustment pump laser group according to input power or power output, meet Δ P to make the power variation of pump laser group and input power or power output variable quantity _p=k* Δ Ptotal, wherein, Δ P _pfor the power variation of pump laser group, unit mw; Δ Ptotal is the variable quantity of input power or power output, unit mw; K is calibration slopes.

2. Raman Fiber Amplifier gain compensation according to claim 1 and transient control methods, is characterized in that: described Raman Fiber Amplifier is forward direction Raman Fiber Amplifier, backward Raman Fiber Amplifier or two-way Raman Fiber Amplifier.

3. Raman Fiber Amplifier gain compensation according to claim 1 and transient control methods, it is characterized in that: described pump laser group comprises some pump lasers, each pump laser in pump laser group is calibrated, to determine the calibration slopes k corresponding to each pump laser _i, i=1,2 ... n, n are the quantity of pump laser in pump laser group.

4. Raman Fiber Amplifier gain compensation according to claim 3 and transient control methods, is characterized in that, to pump laser group inside-pumping laser calibration slopes k _icalibration comprise the steps:

Step 1, closedown pump laser group, access testing light source, adjustment attenuator makes input light be a fixed value, and by spectroanalysis instrument scanning Raman Fiber Amplifier output spectrum;

Step 2, open and adjust pump laser group, by the output spectrum of spectroanalysis instrument scanning Raman Fiber Amplifier, meeting the demands to make Raman Fiber Amplifier parameter;

The pump power of each pump laser, the input power of Raman Fiber Amplifier or power output in step 3, record pump laser group;

Step 4, repetition above-mentioned steps, to obtain organizing calibration data set, all comprise the pump power of each pump laser in pump laser group, the input power of Raman Fiber Amplifier or power output in described many group calibration data set more;

Step 5, basis many groups calibration data carry out matching, to obtain the calibration slopes k of each pump laser _i, i=1,2 ... n.

5. Raman Fiber Amplifier gain compensation according to claim 4 and transient control methods, is characterized in that, when many group calibration data carry out matching, adopts linear fit or multistage curve.