CN103227682A - All-optical signal preprocessing device for receiving end of optical fiber communication system - Google Patents

All-optical signal preprocessing device for receiving end of optical fiber communication system Download PDF

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CN103227682A
CN103227682A CN2013101212667A CN201310121266A CN103227682A CN 103227682 A CN103227682 A CN 103227682A CN 2013101212667 A CN2013101212667 A CN 2013101212667A CN 201310121266 A CN201310121266 A CN 201310121266A CN 103227682 A CN103227682 A CN 103227682A
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electro
phase modulator
optic phase
optical fiber
waveform generator
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李蔚
范佑文
王艺蒙
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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Abstract

The invention discloses an all-optical signal preprocessing device for a receiving end of an optical fiber communication system, and belongs to the field of optical fiber communication. The all-optical signal preprocessing device solves the problem that the receiving end of the available high-speed optical fiber communication system cannot process in-band noises. The all-optical signal preprocessing device comprises a first electro-optic phase modulator, a dispersive medium, a second electro-optic phase modulator, an arbitrary waveform generator and a driving amplifier, wherein the first electro-optic phase modulator is connected with the second electro-optic phase modulator through the dispersive medium, and a periodic signal is outputted by the arbitrary waveform generator, and sent to driving ends of the first electro-optic phase modulator and the second electro-optic phase modulator after amplified by the driving amplifier. The all-optical signal preprocessing device is simple in structure; an aggregation extent of the signal energy on a time domain is raised; the white gaussian noises are filtered by filtering; an instantaneous signal-to-noise ratio is increased; the all-optical signal preprocessing device is transparent to various modulation formats and transmission rates, and has the characteristic of low power consumption, so that an ultimate bit error rate of the system is reduced by several magnitude orders; and the all-optical signal preprocessing device is applicable to long-distance, high-capacity and super-speed optical fiber communication systems in various modulation formats and transmission rates.

Description

The full light signal pretreatment unit of a kind of optical fiber telecommunications system receiving terminal
Technical field
The invention belongs to fiber optic communication field, be specifically related to the full light signal pretreatment unit of a kind of optical fiber telecommunications system receiving terminal, be applied to speed fiber optic communication systems, to improve instantaneous signal-to-noise ratio, the improvement system is an energy.
Background technology
Along with constantly development and informationization of contemporary society, the internet becomes people's daily life must an obligato part, and optical fiber communication is because its big capacity, little decay, outstanding electromagnetic interference resistance etc. have been subjected to people's favor, in the past few decades, optical communication network has become the major part that covers whole transmission network and Access Network.
In order to satisfy bandwidth demand owing to the data service develop rapidly, must make full use of the available bandwidth of optical fiber, so existing transmission system all adopts wavelength division multiplexing (Wavelength Division Multiplexing, WDM) mode increases the number of channel, the expanding system data throughout, (Erbium Doped Fiber Amplifier EDFA) is broad band full amplifier the most frequently used in the wdm system to erbium-doped fiber amplifier.Yet, the use of EDFA can bring amplified spont-aneous emission, and (Amplified Spontaneous Emission, ASE) noise reduce Optical Signal To Noise Ratio (Optical Signal to Noise Ratio, OSNR), even desirable EDFA also has the noise factor of 3dB size.For long-distance optical transmission system, total transmission range reaches thousands of kilometers, and the EDFA quantity of cascade can further increase, and makes The noise more serious.In addition, because optical fiber is from effect of nonlinear such as phase modulated, cross-phase modulation, light signal can be introduced into nonlinear phase shift at random in the process of transmission, and this random phase shift meeting further is converted into intensity noise under the effect of chromatic dispersion.So in the high-capacity and high-speed optical transmission system, The noise can not be ignored.The receiving terminal of existing optical transmission system is made of optical filter and optical-electrical converter series connection, and optical filter can the most of out-of-band noise of filtering, yet but can not handle the noise in the band.Along with the raising of transmission rate, the growth of channel width, the influence of in-band noise further enlarges.If can under the situation that in-band noise exists, improve the anti-noise ability of signal, will the performance improvement of system be had a very important role.
Summary of the invention
The invention provides the full light signal pretreatment unit of a kind of optical fiber telecommunications system receiving terminal, solve existing speed fiber optic communication systems receiving terminal and can not handle the problem of in-band noise, realize the energy accumulating of useful signal with simple device, improve judgement signal to noise ratio constantly, the error rate that the reduction system is final.
The full light signal pretreatment unit of a kind of optical fiber telecommunications system receiving terminal provided by the present invention comprises first electro-optic phase modulator, dispersive medium, second electro-optic phase modulator, AWG (Arbitrary Waveform Generator) and driving amplifier, it is characterized in that:
Described first electro-optic phase modulator and second electro-optic phase modulator are identical, optical fiber link receiving terminal light signal is sent into the described first electro-optic phase modulator input, the first electro-optic phase modulator output connects the second electro-optic phase modulator input by dispersive medium, and the second electro-optic phase modulator output connects optical receiver;
Take from the clock signal of optical fiber link receiving terminal light signal and import described AWG (Arbitrary Waveform Generator) trigger end, AWG (Arbitrary Waveform Generator) output periodic signal f (t) is enlarged into electric drive signal through driving amplifier and sends into first, second electro-optic phase modulator drive end simultaneously;
Described periodic signal f (t) is:
f ( t ) = Σ n = 0 ∞ a ( t - nT ) 2 , ( - T 2 ≤ t ≤ T 2 ) ;
A is periodic signal f (t) and the time relation parameter, and t is the time, and T is cycle, identical with clock signal period of f (t), and n is a periodicity;
Figure BDA00003027738400022
V PpBe the peak-to-peak value of AWG (Arbitrary Waveform Generator) output periodic signal voltage, 0.25v＜V Pp≤ 1v;
Described dispersive medium is optical fiber Bragg raster (FBG) or monomode fiber;
The gain G of described driving amplifier satisfies
Figure BDA00003027738400023
V wherein πBe the half-wave voltage of first, second electro-optic phase modulator, the required driving voltage size that adds of expression phase modulation position 180 degree.
The full light signal pretreatment unit of described optical fiber telecommunications system receiving terminal is characterized in that:
Described AWG (Arbitrary Waveform Generator) comprises address counter, waveform data memory, D/A converter, low pass filter and the amplifying circuit of series connection successively; Clock signal triggers port by AWG (Arbitrary Waveform Generator) and imports described address counter, and described amplifying circuit produces periodic signal f (t), by the output output of AWG (Arbitrary Waveform Generator).
The full light signal pretreatment unit of described optical fiber telecommunications system receiving terminal is characterized in that:
Described dispersive medium, its transfer function β wherein 2Be that the 2nd order chromatic dispersion constant is relevant with the dispersive medium material, z is a dispersive medium length, total dispersion value β 2The span of z is 0＜β 2Z＜50ps/nm, ω are optical carrier frequency.
The effect of dispersive medium is that its transfer function and input data signal frequency spectrum multiply each other on frequency domain.
Mathematical Modeling of the present invention can be represented with following formula:
X P ( t ) = 1 - i cot α 2 π exp ( - i 1 2 t 2 tan α 2 ) · { [ x ( t ) exp ( - i t 2 1 2 tan α 2 ) ] ⊗ exp ( i 1 2 csc α t 2 ) } ,
Wherein,
Figure BDA00003027738400033
The expression convolution algorithm, X P(t) and x (t) be respectively output light signal and input optical signal; Deflection angle
Figure BDA00003027738400034
Conversion order p is a real number, but can not be 2 integral multiple;
The input optical signal x (t) of receiving terminal sends into first electro-optic phase modulator earlier and carries out phase modulated and obtain first modulated light signal Enter one section dispersive medium again and become second modulated light signal
Figure BDA00003027738400036
Sending into second electro-optic phase modulator at last carries out obtaining exporting light signal after the phase modulated X p ( t ) = g ′ ( t ) 1 - i cot α 2 π exp ( - i 1 2 t 2 tan α 2 ) .
Following formula can be regarded as x (t) has been done Fourier Transform of Fractional Order.Studies have shown that the linear chrip signal has different energy accumulatings under different fractional order territories, yet white Gaussian noise all shows characteristic (the happy and carefree work that waits of relatively flat in any fractional order territory, " Fourier Transform of Fractional Order and application thereof ", P99-101, publishing house of Tsing-Hua University).
The present invention is simple in structure, the mode that adopts full optics is carried out preliminary treatment to the signal of receiving terminal, under the prerequisite that does not influence the distribution of noise time domain, increase the aggregation extent of signal energy on time domain, by the narrower filter elimination white Gaussian noise of bandwidth, improve instantaneous signal-to-noise ratio, various modulation formats and transmission rate all are transparent and have low in power consumption.Adopt communication system of the present invention through checking, the final error rate is from 10 -9Be reduced to 10 -14, the cost of the system complexity that usefulness is very little promptly brings the significantly improvement of performance, has great application prospect in growing apart from the high-capacity optical fiber communication system.
Description of drawings
Fig. 1 is an embodiment of the invention structural representation;
Fig. 2 is the structural representation of AWG (Arbitrary Waveform Generator).
Embodiment
The present invention is further described below in conjunction with drawings and Examples.
As shown in Figure 1, embodiments of the invention comprise first electro-optic phase modulator, dispersive medium, second electro-optic phase modulator, AWG (Arbitrary Waveform Generator) and driving amplifier, it is characterized in that:
Described first electro-optic phase modulator and second electro-optic phase modulator are identical, optical fiber link receiving terminal light signal is sent into the described first electro-optic phase modulator input, the first electro-optic phase modulator output connects the second electro-optic phase modulator input by dispersive medium, and the second electro-optic phase modulator output connects optical receiver;
Take from the clock signal of optical fiber link receiving terminal light signal and import described AWG (Arbitrary Waveform Generator) trigger end, AWG (Arbitrary Waveform Generator) output periodic signal f (t) is enlarged into electric drive signal through driving amplifier and sends into first, second electro-optic phase modulator drive end simultaneously.
As shown in Figure 2, described AWG (Arbitrary Waveform Generator) comprises address counter, waveform data memory, D/A converter, low pass filter and the amplifying circuit of series connection successively; Clock signal triggers port by AWG (Arbitrary Waveform Generator) and imports described address counter, by making address counter add 1 OPADD that changes the address production electric circuit that constitutes by address counter, each address in the inswept waveform data memory of address counter order is up to the end of Wave data, Wave data in each address all is sent in the D/A converter, so that digital signal is converted to analog signal, low pass filter carries out smoothing processing to the transition edge of D/A converter output analog signal, produce required any period signal f (t) through amplifying circuit again, by the output output of AWG (Arbitrary Waveform Generator).
Present embodiment adopts the AWG (Arbitrary Waveform Generator) of the model AWG7122C of U.S. Imtech, and maximum sample rate 24GS/s, waveform length 32M or 64M, maximum analog output amplitude are 1Vpp (2.5GHz), produces cycle parabolic pulses signal.
Driving amplifier is amplified to the output signal amplitude of AWG (Arbitrary Waveform Generator) can satisfy the required maximum phase modulation value of electro-optic phase modulator.The bandwidth of driving amplifier should be complementary with the transmission rate of optical fiber telecommunications system.Present embodiment adopts the radio frequency amplifier chip RF Amplifier TM1001 of Taiwan Micro company, this chip is made with the technological design of GaAs heterojunction bipolar transistor (HBT), be a low cost, high power and high efficiency amplifier integrated circuit, suitable frequency is 2.4GHz～2.5GHz.
In the present embodiment, first electro-optic phase modulator and second electro-optic phase modulator are identical, adopt the LiNbO of Beijing model PMS1527-EX of generation Wei Tong company 3Multi-functional phase-modulator, this phase-modulator is based on the lithium columbate crystal phase-modulator, adopt titanium diffusion or proton exchange technology to make waveguide, device insertion loss is little, driving voltage is low, and optical fiber and waveguide adopt accurate tiltedly coupling can obtain low back-reflection.The half-wave voltage V of operation wavelength 1550nm place π＜=5.0V, electric bandwidth＞=2.5GHz inserts loss＜=4.0dB.
Lithium columbate crystal is a uniaxial crystal, optical homogeneity is good, after applying electric field on the crystal, to cause the redistribution of bound charge, and may cause the miniature deformation of ionic lattice, its result will cause the variation of dielectric constant, finally cause the variation of crystal refractive index, making is that isotropic medium produces birefringence originally, is that the birefringence characteristic of optically anisotropic crystal changes originally, i.e. electro optic effect.When extra electric field was parallel to crystal Z axle, the refractive index of this direction became:
n z = n e - 1 2 n e 3 γ 33 E 3 5
N wherein e, γ 33, E 3Be respectively e optical axis refractive index, electro-optic coefficient and z direction electric field, light by the phase change that this modulator produces is:
Figure BDA00003027738400061
Wherein V (t) is for adding the driving voltage function, and d, l are the sizes of crystal.
In the present embodiment, it is 200m that dispersive medium adopts the length of company of Wuhan Changfei, and abbe number is the general single mode fiber of 16ps/nm/km, and the monomode fiber cost is low, but the flexible dispersion values.The SiO of monomode fiber itself 2Material just has the dispersion characteristics that depend on wavelength, and wavelength group velocitys different in transmission is different;
Dispersive medium also can adopt FBG, FBG since in the grating coupled mode of different wave length can produce reflection in different positions according to the difference in grating cycle, make different wavelength produce delay inequality, be chromatic dispersion, the chromatic dispersion span is bigger, structure is compact more; FBG as the model DCM-CI-1550.12-N200-FC/APC of Wuhan GuangXun Co., Ltd.

Claims (3)

1. the full light signal pretreatment unit of optical fiber telecommunications system receiving terminal comprises first electro-optic phase modulator, dispersive medium, second electro-optic phase modulator, AWG (Arbitrary Waveform Generator) and driving amplifier, it is characterized in that:
Described first electro-optic phase modulator and second electro-optic phase modulator are identical, optical fiber link receiving terminal light signal is sent into the described first electro-optic phase modulator input, the first electro-optic phase modulator output connects the second electro-optic phase modulator input by dispersive medium, and the second electro-optic phase modulator output connects optical receiver;
Take from the clock signal of optical fiber link receiving terminal light signal and import described AWG (Arbitrary Waveform Generator) trigger end, AWG (Arbitrary Waveform Generator) output periodic signal f (t) is enlarged into electric drive signal through driving amplifier and sends into first, second electro-optic phase modulator drive end simultaneously;
Described periodic signal f (t) is:
f ( t ) = Σ n = 0 ∞ a ( t - nT ) 2 , ( - T 2 ≤ t ≤ T 2 ) ;
A is periodic signal f (t) and the time relation parameter, and t is the time, and T is cycle, identical with clock signal period of f (t), and n is a periodicity;
Figure FDA00003027738300012
V PpBe the peak-to-peak value of AWG (Arbitrary Waveform Generator) output periodic signal voltage, 0.25v＜V Pp≤ 1v;
Described dispersive medium is optical fiber Bragg raster or monomode fiber;
The gain G of described driving amplifier satisfies V wherein πBe the half-wave voltage of first, second electro-optic phase modulator, the required driving voltage size that adds of expression phase modulation position 180 degree.
2. the full light signal pretreatment unit of optical fiber telecommunications system receiving terminal as claimed in claim 1 is characterized in that:
Described AWG (Arbitrary Waveform Generator) comprises address counter, waveform data memory, D/A converter, low pass filter and the amplifying circuit of series connection successively; Clock signal triggers port by AWG (Arbitrary Waveform Generator) and imports described address counter, and described amplifying circuit produces periodic signal f (t), by the output output of AWG (Arbitrary Waveform Generator).
3. the full light signal pretreatment unit of optical fiber telecommunications system receiving terminal as claimed in claim 1 or 2 is characterized in that:
Described dispersive medium, its transfer function
Figure FDA00003027738300021
β wherein 2Be that the 2nd order chromatic dispersion constant is relevant with the dispersive medium material, z is a dispersive medium length, total dispersion value β 2The span of z is 0＜β 2Z＜50ps/nm, ω are optical carrier frequency.
CN2013101212667A 2013-04-09 2013-04-09 All-optical signal preprocessing device for receiving end of optical fiber communication system Pending CN103227682A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102664685A (en) * 2012-04-12 2012-09-12 武汉邮电科学研究院 Device and method for restraining in-band white noise in high-speed optical fiber communication system
CN104467969A (en) * 2014-12-10 2015-03-25 北京理工大学 Method for measuring chromatic dispersion of optical fiber link through fractional order Fourier transformation

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1417968A (en) * 2001-11-11 2003-05-14 华为技术有限公司 Light signal regulating method and light transmission system for high-speed transmission system
US20040125435A1 (en) * 2002-12-30 2004-07-01 Xiang Liu Nonlinear phase-shift compensation method and apparatus
CN201191836Y (en) * 2008-05-12 2009-02-04 华中科技大学 Full-optical self-adapting signal equalizer
CN102420661A (en) * 2011-12-15 2012-04-18 华中科技大学 Device for compensating non-linear damage of optical fiber
CN102523048A (en) * 2011-12-15 2012-06-27 华中科技大学 Optical fiber nonlinear effect restraining device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1417968A (en) * 2001-11-11 2003-05-14 华为技术有限公司 Light signal regulating method and light transmission system for high-speed transmission system
US20040125435A1 (en) * 2002-12-30 2004-07-01 Xiang Liu Nonlinear phase-shift compensation method and apparatus
CN201191836Y (en) * 2008-05-12 2009-02-04 华中科技大学 Full-optical self-adapting signal equalizer
CN102420661A (en) * 2011-12-15 2012-04-18 华中科技大学 Device for compensating non-linear damage of optical fiber
CN102523048A (en) * 2011-12-15 2012-06-27 华中科技大学 Optical fiber nonlinear effect restraining device

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102664685A (en) * 2012-04-12 2012-09-12 武汉邮电科学研究院 Device and method for restraining in-band white noise in high-speed optical fiber communication system
CN104467969A (en) * 2014-12-10 2015-03-25 北京理工大学 Method for measuring chromatic dispersion of optical fiber link through fractional order Fourier transformation
US9602199B2 (en) 2014-12-10 2017-03-21 Beijing Institute Of Technology Method of measuring optical fiber link chromatic dispersion by fractional Fourier transformation (FRFT)
CN104467969B (en) * 2014-12-10 2017-03-22 北京理工大学 Method for measuring chromatic dispersion of optical fiber link through fractional order Fourier transformation

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Application publication date: 20130731