CN101666954B - High-speed optical soliton transmission system under Raman amplification and computing method for soliton spectrum - Google Patents

Abstract

The invention discloses a high-speed optical soliton transmission system under Raman amplification and a computing method for a soliton spectrum, which builds the high-speed optical soliton transmission system, modifies a soliton transmission equation and gives the computing method for the soliton spectrum by adopting backward pump Raman amplification technology. The high-speed soliton pulse transmission system built by the invention has good performance, simple structure, low cost and easy use, and overcomes the shortages of the prior optical pulse transmission system; and the corresponding computing method provides powerful support for pulse transmission system optimization and intensive study of the field. The system and the computing method can be applied in the fields of high-speed pulse transmission and high-speed communication. The figure 1 in the abstract is a schematic diagram of the high-speed optical soliton transmission system under the Raman amplification, wherein 1 represents high-speed light pulse (10GHz), 2 represents an erbium doped fiber amplifier, 3 represents optical fiber, 4 represents a Raman laser, 5 represents a polarization controller, 6 represents a combiner, 7 represents a measuring apparatus or an output port.

Description

The high-speed optical soliton transmission system under the Raman amplification and the computing method of soliton spectrum

Affiliated technical field

The present invention relates to the high-speed optical soliton transmission system under the Raman amplification and the computing method of soliton spectrum, can be applicable to high-speed optical pulse transmission and high-speed communication field.

Background technology

Raman among the present invention amplifies the full light amplification that is based on the stimulated Raman scattering principle and realizes as gain media with optical fiber, for rear-earth-doped optical fiber amplifies, it has bigger gain bandwidth (GB), gain spectral district, lower amplifier spontaneous emission noise and the advantages such as deterioration that can effectively suppress signal to noise ratio (S/N ratio) flexibly, obtains increasing the application in recent years in fibre-optic transmission system (FOTS).The research that fiber Raman is amplified at present both at home and abroad concentrates on the selection and the optimization of pumping source number in the linear transfer system, power, wavelength etc. mostly, less to the research that utilizes the optical soliton transmission system that fiber Raman amplifies, and adopting autocorrelation technique to measure the pulse time domain mostly changes, be difficult to accurately judge the parameters such as time domain waveform of pulse, and optical soliton transmission spectrum complexity, the further investigation in this field is subjected to certain limitation.

Summary of the invention

In order to overcome the deficiency of existing optical pulse transmission system, the present invention adopts backward pump Raman amplifying technique to make up high-speed optical soliton transmission system, revised orphan's transmission equation, utilize second harmonic-frequency resolution optical gate technique to measure the characteristic parameters such as waveform of importing soliton pulse, provided the computing method of soliton spectrum.The high speed soliton pulse transmission system performance that the present invention makes up is good, simple in structure, low price and be easy to practicality, and corresponding computing method provide powerful support for for the further investigation in pulse transmission system optimization and this field provides especially.

The technical solution adopted for the present invention to solve the technical problems is: adopt backward pump Raman amplifying technique to make up high-speed optical soliton transmission system, revised orphan's transmission equation, utilize second harmonic-frequency resolution optical gate technique to measure the characteristic parameters such as waveform of importing soliton pulse, provided the computing method of soliton spectrum.

The invention has the beneficial effects as follows: burst transmissions is effective, simple in structure, low price and be easy to practicality, and corresponding computing method provide powerful support for for the further investigation in pulse transmission system optimization and this field provides especially.

Description of drawings

The present invention is further described with enforcement below in conjunction with accompanying drawing.

Fig. 1 is the high-speed optical soliton pulse transmission system synoptic diagram under the Raman amplification of the present invention.

1. high-speed optical pulses (10GHz) among the figure, 2. Erbium-Doped Fiber Amplifier (EDFA), 3. optical fiber, 4. Raman laser, 5. Polarization Controller, 6. wave multiplexer, 7. surveying instrument or output port.

Embodiment

In Fig. 1,10GHz high-speed optical pulse (1) is amplified by Erbium-Doped Fiber Amplifier (EDFA) (2) appropriate power and forms the optical soliton pulse, can adopt this moment second harmonic-frequency resolution optical gate technique to measure the characteristic parameters such as waveform of input soliton pulse, then optical soliton input optical fibre (3) be transmitted; The continuous pump light that Raman laser (4) sends enters Transmission Fibers by wave multiplexer (6) backward pump after Polarization Controller (5) is regulated polarization, the optical soliton signal that transmits in the optical fiber is realized the distributed Raman amplification.At last, can carry out optical pulse detection or transmission at surveying instrument or output port (7).

Consider that native system adopts the Raman of continuous pumping wave 1450nm backward pump to amplify, the effective fiber length that Raman amplifies is

$L_{\mathrm{eff}}=\frac{1}{{\mathrm{\α}}_p}[1-\exp \left({-\mathrm{\α}}_{p}L\right)],---\left(1\right)$

In the formula, α _pBe the fibre loss at pump light frequency place, at the 1450nm place, experiment records α _p=0.29dB/km.When optical fiber longer, α _pL〉〉 1 o'clock, $L_{\mathrm{eff}}\≈\frac{1}{{\mathrm{\α}}_p}=\frac{1}{0.29\×{4.343}^{-1}}\≈15\mathrm{km}.$ Consider the situation such as distributed Raman amplification, fibre loss of above-mentioned transmission system, we are modified to the optical soliton transmission equation:

$i\frac{\∂u}{\∂\mathrm{\ξ}}+\frac{1}{2}\frac{{\∂}^{2}u}{\∂{\text{\τ}}^2}+{\left|u\right|}^{2}u=-0.5i({\mathrm{\α}}_s-{\mathrm{\α}}_R^{\′})L_{D}u,---\left(2\right)$

In the formula, u is the normalization electric field, and ξ is the normalization transmission range, τ=T/T ₀Be the normalization time, ${\mathrm{\α}}_R^{\′}={\mathrm{\α}}_s\exp [-{\mathrm{\α}}_p(L\′-\mathrm{\ξ})L_D]$ The normalization Raman gain coefficienct, α _sFibre loss coefficient when being the respective signal wavelength, L _DBe a chromatic dispersion length.Consider the complicacy of optical soliton transmission spectrum, provided r.m.s. spectrum

${\mathrm{\ω}}_{\mathrm{RMS}}={[\frac{\underset{-\∞}{\overset{+\∞}{\∫}}{\mathrm{\ω}}^2{\left|u(\mathrm{\ξ},\mathrm{\ω})\right|}^2\mathrm{d\ω}}{\underset{-\∞}{\overset{+\∞}{\∫}}{\left|u(\mathrm{\ξ},\mathrm{\ω})\right|}^2\mathrm{d\ω}}-{(\frac{\underset{-\∞}{\overset{+\∞}{\∫}}\mathrm{\ω}{\left|u(\mathrm{\ξ},\mathrm{\ω})\right|}^2\mathrm{d\ω}}{\underset{-\∞}{\overset{+\∞}{\∫}}{\left|u(\mathrm{\ξ},\mathrm{\ω})\right|}^2\mathrm{d\ω}})}^2]}^{1/2}.---\left(3\right)$

In conjunction with the input characteristics of equation (1), (2) and (3) and soliton pulse, can be optimized with characteristics such as spectrum optical soliton transmission system and carry out deep research.

Our experimental study the pulse of 10GHz optical soliton transmit the situation of 9km (G652 optical fiber) in said system, the result shows that the aforementioned calculation method is very effective.

Claims (1)

1. based on the soliton spectrum computing method of backward pump Raman amplifying technique high-speed optical soliton transmission system, it is characterized in that:

Backward pump Raman amplifying technique high-speed optical soliton transmission system briefly is described as: the 10GHz high-speed optical pulse is amplified by the Erbium-Doped Fiber Amplifier (EDFA) appropriate power and forms the optical soliton pulse, can adopt this moment second harmonic-frequency resolution optical gate technique to measure the waveform of input soliton pulse, then the optical soliton input optical fibre be transmitted; The continuous pump light that Raman laser sends enters Transmission Fibers by the wave multiplexer backward pump after Polarization Controller is regulated polarization, the optical soliton signal that transmits in the optical fiber is realized the distributed Raman amplification; At last, the light pulse after can amplifying Raman experimentize and measure or transmission;

Consider that native system adopts the Raman of continuous pumping wave 1450nm backward pump to amplify, the effective fiber length that Raman amplifies is

$L_{\mathrm{eff}}=\frac{1}{{\mathrm{\α}}_p}[1-\exp (-{\mathrm{\α}}_{p}L)],---\left(1\right)$

In the formula (1), L is a Transmission Fibers length, α _pBe the fibre loss at pump light frequency place, at the 1450nm place, experiment records α _p=0.29dB/km; When optical fiber longer, α _pL＞＞1 o'clock, This system adopts fiber lengths 9km; Optical soliton transmission equation under the Raman amplification is modified to:

$i\frac{\∂u}{\∂\mathrm{\ξ}}+\frac{1}{2}\frac{{\∂}^{2}u}{{\∂\mathrm{\τ}}^2}+{\left|u\right|}^{2}u=-0.5i{({\mathrm{\α}}_s-{\mathrm{\α}}_R^{\′})L}_{D}u,---\left(2\right)$

In the formula (2), u is a normalization time domain electric field, and ξ is a normalization transmission range variable, τ=T/T ₀Be the normalization time, α ' _R=α _sExp[-α _p(L '-ξ) L _D] the normalization Raman gain coefficienct, α _sBe the fibre loss coefficient of respective signal wavelength, L ' is the normalization length of Transmission Fibers, L _DBe a chromatic dispersion length,

Consider the complicacy of optical soliton transmission spectrum, provided r.m.s. (RMS) spectrum of transmission optical soliton

${\mathrm{\ω}}_{\mathrm{RMS}}={[\frac{\underset{-\∞}{\overset{+\∞}{\∫}}{\mathrm{\ω}}^2{\left|u(\mathrm{\ξ},\mathrm{\ω})\right|}^2\mathrm{d\ω}}{\underset{-\∞}{\overset{+\∞}{\∫}}{\left|u(\mathrm{\ξ},\mathrm{\ω})\right|}^2\mathrm{d\ω}}-{\left(\frac{\underset{-\∞}{\overset{+\∞}{\∫}}\mathrm{\ω}{\left|u(\mathrm{\ξ},\mathrm{\ω})\right|}^2\mathrm{d\ω}}{\underset{-\∞}{\overset{+\∞}{\∫}}{\left|u(\mathrm{\ξ},\mathrm{\ω})\right|}^2\mathrm{d\ω}}\right)}^2]}^{1/2},---\left(3\right)$

In the formula (3), ω _RMSExpression orphan's r.m.s. spectrum, (ξ ω) is the Fourier transform of time domain electric field to u, and ω is orphan's frequency domain angular frequency; Select Transmission Fibers length according to equation (1); According to equation (2) transmission that the input orphan carries out under the Raman amplification is calculated, input orphan's waveform was obtained by second harmonic-frequency resolution optical gate technique experiment measuring during transmission was calculated; Orphan's r.m.s. spectrum calculates with equation (3) in the transmission course.

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